A review of water pollution arising from agriculture and mining activities in Central Asia: Facts, causes and effects

Quality evaluation and health risk assessment of karst groundwater in Southwest China

Groundwater in karst regions is of immense value due to its vital support for regional ecosystems and residents' livelihoods. However, it is simultaneously threatened by multi-source pollution from agricultural non-point sources, industrial and domestic point sources, and mining activities. This study focuses on the Guangxi of China, which features typical karst topography, aiming to thoroughly assess the groundwater quality and related health risks in Guangxi, especially identifying the impacts of various key pollution sources on the groundwater environment. A total of 1912 groundwater samples were collected, covering an area of approximately 237,600 km2. The spatial distribution of pollutants was analysed using the Nemeroww index method and Kriging interpolation, while multivariate statistical and cluster analysis methods were employed to identify the main types of pollution sources. Furthermore, based on the human health risk assessment model of the U.S. Environmental Protection Agency (US EPA), a risk assessment was conducted for key pollutants. The results revealed widespread heavy metal contamination in Guangxi's groundwater, particularly with concentrations of Mn, As, Al, Pb reaching up to 9.4 mg/L, 2.483 mg/L, 37.95 mg/L, 4.761 mg/L, respectively, significantly exceeding China's national Class III groundwater quality standards. Cluster analysis indicated that mining and industrial activities are the primary sources of pollution. The health risk assessment demonstrated that these activities pose a significant risk to public health. The aim of this study is to provide a scientific basis for the protection of the groundwater environment in Guangxi and other karst areas, the formulation of pollution prevention and control strategies, and the optimization of urban and industrial land use layouts. Future research should focus on advanced isotopic and molecular biological techniques to trace pollution sources more precisely and evaluate the effectiveness of pollution control measures.

An overview of the recent advances and future prospects of three-dimensional particle electrode systems for treating wastewater

Three-dimensional (3D) electrochemical technology is considered a very effective industrial wastewater treatment method for its high treatment efficiency, high current efficiency, low energy consumption, and, especially, ability to completely mineralize nonbiodegradable organic contaminants. Particle electrodes, which are the fundamental components of 3D electrochemical technology, have multiple functions in the electrochemical reaction process. Various types of particle electrodes have been created and applied for wastewater treatment. Herein, we present a thorough analysis of the research and development of particle electrodes used for electrocatalyzing pollutants. Initially, reactor designs, factors affecting the removal efficiency of pollutants and degradation mechanisms are introduced. In particular, a detailed investigation is conducted into the selection of particle electrode materials and the roles they play in the 3D electrochemical treatment of wastewater. Subsequently, the degradation efficiency and energy consumption associated with 3D electrochemical technology for different pollutants are investigated. Finally, the directions and outlook for further studies on particle electrodes are discussed. We believe that this review will offer a useful perspective on the development and application of particle electrodes for wastewater purification.

Removal of Heavy Metals from Wastewaters and Other Aqueous Streams by Pressure-Driven Membrane Technologies: An Outlook on Reverse Osmosis, Nanofiltration, Ultrafiltration and Microfiltration Potential from a Bibliometric Analysis

A bibliometric study to analyze the scientific documents released until 2024 in the database Scopus related to the use of pressure-driven membrane technologies (microfiltration, ultrafiltration, nanofiltration and reverse osmosis) for heavy metal removal was conducted. The work aimed to assess the primary quantitative attributes of the research in this field during the specified period. A total of 2205 documents were identified, and the corresponding analysis indicated an exponential growth in the number of publications over time. The contribution of the three most productive countries (China, India and USA) accounts for more than 47.1% of the total number of publications, with Chinese institutions appearing as the most productive ones. Environmental Science was the most frequent knowledge category (51.9% contribution), followed by Chemistry and Chemical Engineering. The relative frequency of the keywords and a complete bibliometric network analysis allowed the conclusion that the low-pressure technologies (microfiltration and ultrafiltration) have been more deeply investigated than the high-pressure technologies (nanofiltration and reverse osmosis). Although porous low-pressure membranes are not adequate for the removal of dissolved heavy metals in ionic forms, the incorporation of embedded adsorbents within the membrane structure and the use of auxiliary chemicals to form metallic complexes or micelles that can be retained by this type of membrane are promising approaches. High-pressure membranes can achieve rejection percentages above 90% (99% in the case of reverse osmosis), but they imply lower permeate productivity and higher costs due to the required pressure gradients.

Cryosphere and land cover influence on stream water quality in Central Asia's glacierized catchments

This work helps address recent calls for systematic water quality assessment in Central Asia and considers how nutrient and salinity sources, and transport, affect water quality along the continuum from the cryosphere to the lowland plains. Spatial and, for the first time, temporal variations in stream water pH, temperature, electrical conductivity, and nitrate and phosphate concentrations are presented for four catchments (485-13,500 km2), all with glaciers and major urban areas. The catchments studied were: Kaskelen (Kazakhstan), Ala-Archa (Kyrgyzstan), Chirchik (Uzbekistan) and the Kofarnihon (Tajikistan). Measurements were made in cryosphere, stream water, groundwater, reservoir and lake samples over a 22-month period at fortnightly intervals from 35 sites. The results highlight that glacier, permafrost and rock glacier outflows were primary and secondary nitrate sources (>1 mg N L-1) to the headwaters, and there were major increases in salinity and nitrate concentrations where rivers receive inputs from agriculture and settlements. Overall, the water quality complied with national and World Health Organization standards, however there were pollution hot-spots with shallow urban groundwaters contaminated with nitrate (>11 mg N L-1) and stream electrical conductivity above 800 μS cm-1 in some agricultural areas indicative of high salinity. Phosphate concentrations were generally low (<0.06 mg P L-1) throughout the catchments, though elevated (>0.2 mg P L-1) in urban areas due to effluent contamination. A melt water dilution effect along the main river channels was discernible, in the electrical conductivity and nitrate concentration seasonal dynamics, 100 s of km from the headwaters. Thus, the input of relatively clean water from the cryosphere is an important regulator of main channel water quality in the urban and farmed lowland plains adjacent to the Tien Shan and Pamir. Improved sewage treatment is needed in urban areas.

The Mechanisms of Cadmium Stress Mitigation by Fungal Endophytes from Maize Grains

Maize is a crucial staple crop that ensures global food security by supplying essential nutrients. However, heavy metal (HM) contamination inhibits maize growth, reduces output, and affects food security. Some endophytic fungi (EFs) in maize seeds have the potential to enhance growth and increase dry biomass, offering a solution to mitigate the negative effect of HM contamination. Using these functional EFs could help maintain crop production and ensure food safety in HM-contaminated areas. In the present study, the diversity of EFs in corn grains from various HM-contaminated areas in China was studied through culture-dependent and culture-independent methods. We tested the plant growth-promoting (PGP) traits of several dominant culturable isolates and evaluated the growth-promoting effects of these twenty-one isolates through pot experiments. Both studies showed that HM contamination increased the diversity and richness of corn grain EFs and affected the most dominant endophytes. Nigrospora and Fusarium were the most prevalent culturable endophytes in HM-contaminated areas. Conversely, Cladosporium spp. were the most isolated endophytes in non-contaminated areas. Different from this, Saccharomycopsis and Fusarium were the dominant EFs in HM-contaminated sites, while Neofusicoccum and Sarocladium were dominant in non-contaminated sites, according to a culture-independent analysis. PGP trait tests indicated that 70% of the tested isolates (forty-two) exhibited phosphorus solubilization, IAA production, or siderophore production activity. Specifically, 90% of the tested isolates from HM-contaminated sites showed better PGP results than 45% of the isolates from non-contaminated sites. The benefit of the twenty-one isolates on host plant growth was further studied through pot experiments, which showed that all the isolates could improve host plant growth. Among them, strains derived from HM-contaminated sites, including AK18 (Nigrospora), AK32 (Beauveria), SD93 (Gibberellia), and SD64 (Fusarium), had notable effects on enhancing the dry biomass of shoots and roots of maize under Cd stress. We speculate that the higher ratio of PGP EFs in corn grains from HM-contaminated areas may explain their competitiveness in such extreme environments. Fusarium and Cladosporium isolates show high PGP properties, but they can also be phytopathogenic. Therefore, it is essential to evaluate their pathogenic properties and safety for crops before considering their practical use in agriculture.

Ultrasensitive detection of trace Hg(Ⅱ) in acidic conditions using DMABR loaded on sepiolite: Function, application and mechanism studies

Fast and real-time detection of trace Hg(Ⅱ) by fluorescent probes under acidic conditions is urgently required due to the high toxicity and accessibility to creatures and human being. However, fluorescent probes for Hg(Ⅱ) detection in environmental samples are rarely reported due to the protonation potential of acidic mercury sources. In this study, the SD probe was developed by 5-(p-dimethylaminobenzylidene) rhodanine (DMABR) loaded on sepiolite by hydrothermal treatment, and showed excellent Hg(Ⅱ) detection performances for mercury sources at pH 4-10 due to buffering ability of the hyperconjugated lactam rings. Sepiolite functioned as the support skeleton to decrease intermolecular transition, and thus increased the sensitivity. At pH 4, the SD probe showed high selectivity and sensitivity for Hg(Ⅱ) among various species, with low LOD and binding constant of 4.78 × 10-9 M and 1.34 × 106 M-1, respectively. Through DFT calculations, MAS 1H NMR and 2D-COS analysis, the detection mechanism was demonstrated as SN1 substitution of the spontaneous leaving H on amino groups in the transient state during tautomeric equilibrium, rather than the expected high-affinity sulphydryl. Additionally, the SD probe exhibited promising potential in quantifying water-soluble and bioavailable Hg(Ⅱ) in acidic polluted soil and water samples. Moreover, real-time detection was realized by paper-based strips.

Intelligent micro/nanorobots based on biotemplates

Intelligent micro/nanorobots based on natural materials as biotemplates are considered to be some of the most promising robots in the future in the microscopic field. Due to the advantages of biotemplates such as unique structure, abundant resources, environmental friendliness, easy removal, low price, easy access, and renewability, intelligent micro/nanorobots based on biotemplates can be endowed with both excellent biomaterial activity and unique structural morphology through biotemplates themselves and specific functions through artificial micro/nanotechnology. Thus, intelligent micro/nanorobots show excellent application potential in various fields from biomedical applications to environmental remediation. In this review, we introduce the advantages of using natural biological materials as biotemplates to build intelligent micro/nanorobots, and then, classify the micro/nanorobots according to different types of biotemplates, systematically detail their preparation strategies and summarize their application prospects. Finally, in order to further advance the development of intelligent micro/nanorobots, we discuss the current challenges and future prospects of biotemplates. Intelligent micro/nanorobots based on biotemplates are a perfect combination of natural biotemplates and micro/nanotechnology, which is an important trend for the future development of micro/nanorobots. We hope this review can provide useful references for developing more intelligent, efficient and safe micro/nanorobots in the future.

How the Water-Sediment Regulation Scheme in the Yellow River affected the estuary ecosystem in the last 10 years?

The Yellow River, renowned as the most sediment-laden river globally, grapples with sediment deposition issues compromising reservoir functionality and elevating downstream riverbeds, posing threats to human life and property safety. In response, the Water-Sediment Regulation Scheme (WSRS) has been innovatively implemented to address these challenges. While effectively mitigating sediment deposition, WSRS has concurrently disrupted the equilibrium of the estuarine ecosystem. This paper addresses the understudied but crucial topic of the interannual impact of WSRS on the estuarine ecosystem. Drawing upon physical, chemical, and biological data gathered through field surveys conducted before, during, and after WSRS from 2011 to 2022, the analysis delves into the interannual changes in the estuarine environment, fish eggs and larvae abundance, and species diversity under the influence of WSRS. The findings reveal an interannual decreasing trend in terrestrial material input due to WSRS, juxtaposed with an interannual increasing trend in fish eggs and larvae around the estuary, as well as the species diversity index. Notably, these trends became more pronounced post-2014. Compared to pre-2014, nutrient concentrations experienced a ~20 % decrease, chlorophyll-a concentration increased by 44 %, fish eggs proliferated approximately 1 time, and the species diversity index transitioned from a declining trend to an ascending trajectory. After 12 years of continuous WSRS implementation, the impact on the estuarine ecosystem has demonstrably diminished. This research aims to furnish reference experience and scientific basis for water and sediment regulation in major rivers around the world in terms of estuarine ecology.

Assessing the Influence of Hand-Dug Well Features and Management on Water Quality

Underground water quality can be affected by natural or human-made influences. This study investigates how the management and characteristics of hand-dug wells impact water quality in 3 suburbs of Kumasi, Ghana, using a combination of qualitative and quantitative research methods. Descriptive analysis, including frequency and percentages, depicted the demographic profiles of respondents. Box plot diagrams illustrated the distribution of physicochemical parameters (Total Dissolved Solid [TDS], Electrical Conductivity [EC], Turbidity, Dissolved Oxygen [DO], and Temperature). Factor analysis evaluated dominant factors among these parameters. Cluster analysis (hierarchical clustering) utilized sampling points as variables to establish spatial variations in water physicochemical parameters. Cramer's V correlation test explored relationships between demographic variables and individual perceptions of water management. One-way ANOVA verified significant mean differences among the physicochemical parameters. Logistic regression models assessed the influence of selected well features (e.g., cover and apron) on TDS, pH, Temperature, Turbidity, and DO. The findings revealed that proximity to human settlements affects water quality, and increasing turbidity is associated with unmaintained covers, significantly impacting water quality (P < .05). Over 80% of wells were located within 10 to 30 m of pollution sources, with 65.63% situated in lower ground and 87.5% being unmaintained. Other significant contamination sources included plastic bucket/rope usage (87.50%), defective linings (75%), and apron fissures (59.37%). Presence of E. coli, Total coliform, and Faecal coliform rendered the wells unpotable. Factor analysis attributed 90.85% of time-based and spatial differences to organic particle decomposition factors. However, Cramer's V correlation analysis found establishing association between demographic factor associations with individual perceptions of hand-dug well management difficult. It is encouraged to promote hand-dug well construction and maintenance standards to ensure that wells are properly built and protected from contamination sources.

Eco-Friendly Spiking Approach Based on Microfluidics for Preparation of Matrix Reference Materials

Medicated bath is the most common spiking method used in the development of matrix reference materials for aquatic products; however, the environmental issues caused by the treatment of waste liquid after medicated bath cannot be ignored. We proposed an environmentally friendly spiking method based on microfluidics, which significantly improved the drug utilization rate without the need for subsequent drug residue treatment. Finely processed minced fish samples were fully mixed with quinolone drugs, and minced fish gel microspheres were prepared by microfluidic technology, utilizing the gel's water-locking function to enhance the drug-loading capacity. The results showed that this method can significantly increase the drug-loading capacity of the matrix (2.33-4.03 times) compared with the traditional spiking methods. In addition, the matrix reference material prepared by this method has good stability, and the drug concentration was adjustable and controllable.

A critical review and bibliometric analysis of methylene blue adsorption using leaves

The rapid development of the industrial world causes wastewater containing dyes to continue to increase. Even in recent years, the food, textile, cosmetic, plastic, and printing industries have developed the use of dyes. Methylene blue (MB) is one of the cationic dyes widely used in dyeing silk, wood, and cotton because of its absorbency and good fastness to materials. The adsorption process is the best technique and preferred in removing dyes from wastewater due to excellent selectivity, high efficiency from high-quality treated effluent, flexibility in design, and simplicity. Therefore, there is a growing interest to identify low-cost alternative adsorbents that have reasonable adsorption efficiency, especially natural materials such as leaves. In this study, research on MB adsorption using leaves was analyzed using bibliometric analysis. Information of bibliometric is extracted from the Scopus database with the keyword "Methylene Blue", "Adsorption or Desorption", and "Leaves or leaf". The results showed that India, Desalination and Water Treatment, and SASTRA Deemed University were the country, journal, and institution that contributed the most publications on this topic. Therefore, it is expected that with the use of bibliometrics, the use of leaf-based MB adsorption processes in their potential for MB dye removal can be investigated especially for large-scale development.

Recent advances in clay minerals for groundwater pollution control and remediation

Clay minerals are abundant on Earth and have been crucial to the advancement of human civilization. The ability of clay minerals to absorb chemicals is frequently utilized to remove hazardous compounds from aquatic environments. Moreover, clay-based adsorbent products are both environmentally acceptable and affordable. This study provides an overview of advances in clay minerals in the field of groundwater remediation and related predictions. The existing literature was examined using data and information aggregation approaches. Keyword clustering analysis of the relevant literature revealed that clay minerals are associated with groundwater utilization and soil pollution remediation. Principal component analysis was used to assess the relationships among clay mineral modification methods, pollutant properties, and the Langmuir adsorption capacity (Qmax). The results demonstrated that pollutant properties affect the Qmax of pollutants adsorbed by clay minerals. Systematic cluster analysis was utilized to classify the collected data and investigate the relationships. The pollution adsorption mechanism of the unique structure of clay minerals was investigated based on the characterization results. Modified clay minerals exhibited changes in surface functional groups, internal structure, and pHpzc. This review provides a summary of recent clay-based materials and their applications in groundwater remediation, as well as discussions of their challenges and future prospects.

Responses of sediment n-alkanes to climate factors and anthropogenic disturbances from three lakes with different elevations, arid Central Asia

Biomarkers n-alkanes and pertinent indices in lake sediments are frequently used to infer past changes in climate and environmental conditions in and around lakes. Interpretation of n-alkane records can be confounded by a lack of understanding of the multiple factors that control n-alkanes in sediments. Here, we studied n-alkanes in sediment cores from two alpine lakes, Lakes Son-Kul and Issyk-Kul, and from terminal Lake Balkhash, in arid Central Asia to identify natural and human-mediated influences on sediment n-alkane profiles. Altitudinal differences in climate, as well as in lake trophic status, proved to be important drivers of n-alkane compositional differences in the lake sediments. In the alpine lakes, the distribution of n-alkanes was biased toward long-chain components (n-C29, n-C31, and n-C33), and showed higher carbon preference index (CPIH) values, which come from dense terrestrial plant communities, promoted by greater precipitation. In contrast, n-alkanes in the core from the terminal lake displayed higher proportions of short-chain n-alkanes (n-C17, n-C19, and n-C21) because a greater proportion of the organic matter (OM) input to the sediments was derived from algae, a consequence of higher temperatures and trophic status. In recent decades, increasing nutrient inputs from human activities have caused greater accumulation of short-chain n-alkanes in sediments of alpine, oligotrophic Lake Issyk-Kul. In Lake Balkhash, n-C20 and n-C22 alkanes are exceptionally abundant, suggesting large contributions from microbial reworking of terrestrial OM. In all three study lakes, ∑(n-C29-n-C33) was elevated in sediments that correspond to periods of intense agricultural exploitation. Moreover, expansion of agriculture from low to high altitudes resulted in both synchronous and asynchronous peaks in ∑ (n-C29-n-C33) in the studied cores, suggesting the n-alkanes faithfully record the history of agricultural expansion. These findings provide insights into applications of n-alkane proxies and the response of the lake system to climate and anthropogenic impacts.

Profound regional disparities shaping the ecological risk in surface waters: A case study on cadmium across China

The scientific advancement of water quality criteria (WQC) stands as one of the paramount challenges in ensuring the security of aquatic ecosystem. The region-dependent species distribution and water quality characteristics would impact the toxicity of pollutant, which would further affect the derivation of WQC across regions. Presently, however, numerous countries adhere to singular WQC values. The "One-size-fits-all" WQC value for a given pollutant may lead to either "over-protection" or "under-protection" of organisms in specific region. In this study, we used cadmium(Cd) pollution in surface waters of China as a case study to shed light on this issue. This study evaluated critical water quality parameters and species distribution characteristics to modify WQC for Cd across distinct regions, thus unveiling the geographical variations in ecological risk for Cd throughout China. Notably, regional disparities in ecological risk emerged a substantial correlation with water hardness, while species-related distinctions magnified these regional variations. After considering the aforementioned factors, the variation in long-term WQC among different areas reached 84-fold, while the divergence in risk quotient extended to 280-fold. This study delineated zones of both heightened and diminished ecological susceptibility of Cd, thereby establishing a foundation for regionally differentiated management strategies.

Membrane-based technology in water and resources recovery from the perspective of water social circulation: A review

In this review, the application of membrane-based technology in water social circulation was summarized. Water social circulation encompassed the entire process from the acquirement to discharge of water from natural environment for human living and development. The focus of this review was primarily on the membrane-based technology in recovery of water and other valuable resources such as mineral ions, nitrogen and phosphorus. The main text was divided into four main sections according to water flow in the social circulation: drinking water treatment, agricultural utilization, industrial waste recycling, and urban wastewater reuse. In drinking water treatment, the acquirement of water resources was of the most importance. Pressure-driven membranes, such as ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) were considered suitable in natural surface water treatment. Additionally, electrodialysis (ED) and membrane capacitive deionization (MCDI) were also effective in brackish water desalination. Agriculture required abundant water with relative low quality for irrigation. Therefore, the recovery of water from other stages of the social circulation has become a reasonable solution. Membrane bioreactor (MBR) was a typical technique attributed to low-toxicity effluent. In industrial waste reuse, the osmosis membranes (FO and PRO) were utilized due to the complex physical and chemical properties of industrial wastewater. Especially, membrane distillation (MD) might be promising when the wastewater was preheated. Resources recovery in urban wastewater was mainly divided into recovery of bioenergy (via anaerobic membrane bioreactors, AnMBR), nitrogen (utilizing MD and gas-permeable membrane), and phosphorus (through MBR with chemical precipitation). Furthermore, hybrid/integrated systems with membranes as the core component enhanced their performance and long-term working ability in utilization. Generally, concentrate management and energy consumption control might be the key areas for future advancements of membrane-based technology.

An efficient multi-functional ternary reusable nanocomposite based on chitosan@TiO2@Ag NP immobilized on cellulosic fiber as a support substrate for wastewater treatment

To effectively remove heavy metals, organic contaminants, and pathogenic bacteria from wastewater, an efficient multi-functional ternary nanocomposite based on chitosan (CS), titanium dioxide (TiO2 NP), and silver nanoparticles (Ag NP) was prepared. Different tools were used to confirm the successful synthesis of the CS/TiO2 NP/Ag NP nanocomposite. Then, the CS/TiO2 NP/Ag NPnanocomposite was immobilized on the cellulosic fiber as a support substrate for its easy removal and reuse. On a lab scale, CS/TiO2 NP/Ag NP nanocomposite@cellulosic fiber was used to remove Cu (II) ions, methyl orange (MO), and methylene blue (MB), as well as inhibit microbes. The results demonstrate that the greatest removal of Cu (II) ions was 95 % at a concentration of 50 mg/L, pH 5, a temperature of 25 °C, an agitation speed of 200 rpm with 1 g adsorbent dose, and a contact time of 150 min. The pseudo-second-order model explained the batch adsorption kinetics well, while the Langmuir model explained the adsorption isotherm well with an adsorption capacity of 7.71 mg/g. Adsorption thermodynamic parameters revealed that adsorption is a spontaneous, exothermic, increased randomness, and non-specific chemisorption approach. The photodegradation of MO and MB by CS/TiO2 NP/Ag NP nanocomposite@cellulosic fiber was investigated. The results reveal that at pH 3, the MO dye showed the highest photodegradation percentage (90 %), while the MB dye displayed the highest photodegradation percentage (94 %) at pH 11, after an irradiation time of 120 min under visible light. The rate constants for MO and MB were 0.01218 and 0.01412 min-1, respectively. The results antimicrobial activities showed that the CS/TiO2 NP/Ag NP nanocomposite@cellulosic fiber showed excellent antibacterial activity against S. aureus (95 ± 2 %) and E. coli (93 ± 3 %) as well as good antifungal activity against C. albicans (77 ± 2 %).

Enhanced photo-Fenton-like performance of biotemplated manganese-doped cobalt silicate catalysts

Cobalt-based catalysts are one of the preferred materials for effective activation of hydrogen peroxide, and metal element doping and active site dispersion are effective methods to enhance their catalytic activity. In this work, manganese-doped cobalt silicate@diatomite composites with enhanced photo-Fenton-like oxidation performance were prepared and used for degradation of methyl orange (MO) dyes. Experiments showed that manganese doping increased the specific surface area of the samples and decreased the band gap energy of the materials. Moreover, the samples doped with manganese elements had better photo-Fenton-like properties. The degradation of methyl orange by Co0.25MnSi@DE/H2O2-UV reached more than 95%. In addition, density-functional theory (DFT) calculations showed that the Mn-doped samples were more prone to activate H2O2 than non-manganese-doped samples, and the synergistic effect from using a bimetallic catalyst increased the photo-Fenton oxidation activity in the system. ESR spectroscopy and bursting tests indicated that the possible degradation mechanism consisted of hydroxyl radicals and superoxide radicals generated by the synergistic effect of cobalt ions and manganese under UV radiation. This study thus presents a feasible idea for the preparation of cobalt-based photo-Fenton catalysts that also provides a basis for understanding the catalytic mechanism analysis of other types of bimetallic catalysts.

Adsorption potential of orange rind-based nanosorbents for the removal of cadmium(II) and chromium(VI) from contaminated water

Heavy metals (HMs) in water are highly poisonous and carcinogenic agents for human health. To alleviate the toxic impacts of HMs, green remediation technologies are the need of the hour. In this regard, different nanosorbents (CMCG@ORP, ORAC, NiO/NPs, and NiO@ORAC/NCs) were synthesized in the present study, and the percentage removal of heavy metals [chromium(VI) and cadmium(II) ions] was evaluated. The nanosorbents were characterized by using FTIR, SEM, UV-Vis spectroscopy, and XRD. UV-Vis spectroscopy confirmed the synthesis of nanosorbents such as NiO/NPs and NiO@ORAC/NCs at 330.5 nm and 352.55 nm, respectively. The characterization studies show that the surface of synthesized nano-sorbents was highly coarse, uneven, and abrasive. XRD pattern deduced that the sample was of single phase, and no other impurity was detected except the face-centered cubic-phase peak of NiO. The maximum adsorption of Cd (91%) and Cr (92%) was found at initial concentrations of 100 and 60 ppm respectively at contact time = 180 min, temperature 25 °C, and with an adsorbent dose of 0.5 g. Isothermal, kinetic, and thermodynamic studies were also performed to evaluate the adsorption mechanisms and feasibility of the process. Adsorption mostly followed Freundlich isotherm which indicates the multilayer adsorption phenomenon and the negative value of Gibb's free energy showed the spontaneous nature and feasibility of the adsorption reaction. Surface complexation, ion exchange, surface precipitation, and the phenomenon of physical adsorption occurred on the sorbent surface which led to the attachment of Cd and Cr to the tested nanosorbents. In conclusion, NiO@ORAC/NCs were the most effective in the alleviation of Cd(II) and Cr(VI) ions in contaminated water.

Hydrogeochemical evolution of groundwater impacted by acid mine drainage (AMD) from polymetallic mining areas (South China)

Mining activities have long-term impacts on the groundwater of surrounding areas and deserve in-depth analysis and study. Herein, the geochemical mechanisms of acid mine drainage (AMD)-affected groundwaters were examined, and groundwater quality was assessed through water quality indices. 15 water samples from 7 domestic and 4 groundwater monitoring wells were tested for physical and chemical parameters in 2022, and multivariate statistical analysis was carried out with monitoring data from 21 domestic wells in 2010. The groundwater chemical composition varied from a predominantly Ca-HCO3 type in 2010 to a Ca-SO4 type in 2022. The isotopic values of δ18O and δD indicate that groundwater has not been significantly affected by evaporation. Changes in groundwater sulfate and total dissolved solids (TDS) levels over the twelve-year period confirmed the AMD infiltration impact on groundwater quality. The groundwater chemical properties changed more slowly than those of surface waters affected by AMD based on a cumulative increase in sulfate concentration of 29.94 mg/L. Changes in groundwater quality were investigated, namely, the spatiotemporal distribution of potentially toxic elements (PTEs), including Fe, Mn, Cd, Pb, and As. Mn concentrations in upstream groundwater areas near the mine decreased by 61.8% between 2010 and 2022. Conversely, groundwater in midstream areas had Mn concentrations of 2.25 mg/L and arsenic concentrations of 11.8 μg/L, both exceeding the WHO, 2022 standard. According to multivariate statistical analysis, Mn, Cd, and Pb originated from polymetallic minerals, whereas As was likely derived from the reduction of Fe/Mn hydroxyl oxides. AMD remediation improved contaminated upstream groundwater quality over 12 years, with a 36.8% improvement in WQI values. PTE distribution determined water quality changes; therefore, PTE contamination should be treated in mid- and downstream regions while contaminated groundwater should be treated upstream.

Synthesis of calcium carbonate-loaded mesoporous SBA-15 nanocomposites for removal of phosphate from solution

Removal of phosphate from water is very crucial for protecting the ecological environment since massive phosphorus fertilizers have been widely used and caused serious water deterioration. Thus, we fabricated a series of calcium carbonate-loaded mesoporous SBA-15 nanocomposites with different Ca:Si molar ratio (CaAS-x) as phosphorus adsorbents via a simple wet-impregnation method. The multiply approaches including X-ray diffraction (XRD), N₂ physisorption, thermogravimetric mass spectrometry (TG-MS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) were used to characterize the structure, morphology, and composition of mesoporous CaAS-x nanocomposites. The phosphate adsorption efficiency of the CaAS-x nanocomposites was studied through adsorption and desorption batch tests. Results showed that the increases of Ca:Si molar ratio (rCa:Si) improved the phosphate removal capacity of CaAS nanocomposites, especially CaAS with the optimum synthesis molar ratio of Ca:Si as 0.55 showed the high adsorption capacity of 92.0 mg·g^-1 to high concentration of phosphate (> 200 mg·L^-1). Note that the CaAS-0.55 had a fast exponentially increased adsorption capacity with increasing the phosphate concentration and correspondingly showed a much faster phosphate removal rate than pristine CaCO₃. Apparently, mesoporous structure of SBA-15 contributed to high disperse of CaCO₃ nanoparticles leading to the monolayer chemical adsorption complexation formation of phosphate calcium (i.e., =SPO₄Ca, =CaHPO₄^-, and =CaPO₄Ca⁰). Therefore, mesoporous CaAS-0.55 nanocomposite is an environmental-friendly adsorbent for effective removal of high concentration of phosphate in neutral contaminated wastewater.

Surface Adsorption Mechanism between Lead(II,IV) and Nanomaghemite Studied on Polluted Water Samples Collected from the Peruvian Rivers Mantaro and Cumbaza

Real water remediation is an important issue that requires the development of novel adsorbents with remarkable adsorption properties, permitting reusability. In this work, the surface and adsorption properties of bare magnetic iron oxide nanoparticles were systematically studied, before and after the application of a maghemite nanoadsorbent in two real Peruvian effluents severely contaminated with Pb(II), Pb(IV), Fe(III), and others. We were able to describe the Fe and Pb adsorption mechanisms that occurred at the particle surface. ⁵⁷Fe Mössbauer and X-ray photoelectron spectroscopy results together with kinetic adsorption analyses gave evidence for two involved surface mechanisms: (i) surface deprotonation of maghemite nanoparticles (isoelectric point of pH = 2.3), forming Lewis sites bonding Pb complexes; and (ii) the formation of a thin inhomogeneous secondary layer of iron oxyhydroxide and adsorbed Pb compounds, as favored by surface physicochemical conditions. The magnetic nanoadsorbent enhanced the removal efficiency to values of ca. 96% and provided adsorptive properties with reusability due to the conserved morphological, structural, and magnetic properties. This makes it favorable for large-scale industrial applications.

Viologen-functionalized magnetic material for the removal of Iodine and benzanthracene in an aqueous solution

The development of magnetically active adsorbents for effective iodine removal would be highly desirable to address environmental pollution and remediation. Herein, we demonstrated the synthesis of Vio@SiO₂@Fe₃O₄ as an adsorbent via surface functionalisation of electron-deficient bipyridium (viologen) units on the surface of magnetically active silica-coated magnetite (Fe₃O₄) core. This adsorbent was characterised thoroughly using various analytical techniques, such as field emission scanning electron microscopy (FESEM), thermal gravimetric analysis, Fourier transform infrared spectroscopy (FTIR), field emission transmission electron microscopy (FETEM), Brunauer-Emmett-Teller (BET) analysis and X-ray photon analysis (XPS). The removal of triiodide from the aqueous solution was monitored via the batch method. It revealed that the complete removal was achieved upon stirring for 70 min. The thermally stable and crystalline Vio@SiO₂@Fe₃O₄ displayed efficient removal capacity even in the presence of other competing ions and at different pHs. The adsorption kinetics data were analysed following the pseudo-first-order and pseudo-second-order models. Further, the isotherm experiment showed that the maximum uptake capacity of iodine is 1.38 g/g. It can be regenerated and reused over multiple cycles to capture iodine. Further, Vio@SiO₂@Fe₃O₄ displayed a good removal capacity toward toxic polyaromatic, Benzanthracene (BzA) pollutant with an uptake capacity of 2445 μg/g. This effective removal of toxic pollutants iodine/benzanthracene was attributed to the strong non-covalent electrostatic and π-π interaction with electron-deficient bipyridium units.

Spatial and temporal evolution of mine dust research: visual knowledge mapping analysis in Web of Science from 2001 to 2021

Dust pollution control is the basic guarantee of mine safety production, which has been widely concerned by scholars. Based on a total of 1786 publications collected by the Web of Science Core Collection (WOSCC) from 2001 to 2021, this paper analyzes the spatial-temporal distribution characteristics, hot topics, and frontier trends of the international mine dust field during the past 20 years by using Citespace and VOSviewer knowledge graph technology. The research shows that the study of mine dust can be divided into three stages: initial period (2001 ~ 2008), stable transition period (2009 ~ 2016), and boom period (2017 ~ 2021). The journals and disciplines which belong to mine dust research mainly focus on environmental science and engineering technology. A stable core group of authors and institutions have been preliminarily formed in the dust research field. The main themes of the study contained the whole process of mine dust generation, transport, prevention, and control, as well as the consequences of disaster. At present, the hot research fields mainly focus on mine dust particle pollution, multi-stage dust prevention, and emission reduction technologies, and mine occupational protection, monitoring, and early warning. In the future, the research should focus on the mechanism of dust production and transportation, the theory of efficient prevention and control, the technology and equipment of precise prevention and control of dust, and the high-precision monitoring and early warning of dust concentration. Future research should be concerned with dust control in underground mines and deep concave open-pit mines with complicated and treacherous environments, and strengthen research institutions, interdisciplinary cooperation, and interaction so as to promote the integration and application of mine dust and automation, information, and intelligent technology.

Groundwater Quality and Health: Making the Invisible Visible

Linking groundwater quality to health will make the invisible groundwater visible, but there are knowledge gaps to understand the linkage which requires cross-disciplinary convergent research. The substances in groundwater that are critical to health can be classified into five types according to the sources and characteristics: geogenic substances, biogenic elements, anthropogenic contaminants, emerging contaminants, and pathogens. The most intriguing questions are related to quantitative assessment of human health and ecological risks of exposure to the critical substances via natural or induced artificial groundwater discharge: What is the list of critical substances released from discharging groundwater, and what are the pathways of the receptors' exposure to the critical substances? How to quantify the flux of critical substances during groundwater discharge? What procedures can we follow to assess human health and ecological risks of groundwater discharge? Answering these questions is fundamental for humans to deal with the challenges of water security and health risks related to groundwater quality. This perspective provides recent progresses, knowledge gaps, and future trends in understanding the linkage between groundwater quality and health.

Seasonal assessment of the distribution, source apportionment, and risk of water-contaminated polycyclic aromatic hydrocarbons (PAHs)

The research aims to evaluate the seasonal differences in the distribution, source, and risks of water-contaminated PAHs. The PAHs were extracted by the liquid-liquid method and analyzed with GC-MS, and a total of eight PAHs were detected. There was a percentage increase in the average concentration of the PAHs from the wet to the dry season in the range of 20 (Anthracene)-350 (Pyrene)%. Total PAHs (∑PAHs) range from 0.31 to 1.23 mg/l in the wet period and from 0.42 to 1.96 mg/l in the dry period. The distribution of the average PAHs in mg/l showed that Fluoranthene ≤ Pyrene < Acenaphthene < Fluorene < Phenanthrene < Acenaphthylene < Anthracene < Naphthalene in wet period and while Fluoranthene < Acenaphthene < Pyrene < Fluorene < Phenanthrene < Acenaphthylene < Anthracene < Naphthalene in the dry period. The children were exposed to non-carcinogenic risk through non-dietary ingestion due to the accumulative effect (HI) of the PAHs in the dry period. Furthermore, the naphthalene was responsible for ecological and carcinogenic risk in the wet period, while the fluorene, phenanthrene, and anthracene were responsible for ecological and carcinogenic risk in the dry period. However, while adults and children are both susceptible to carcinogenic risk through the oral channel during the dry period, only children are susceptible to non-carcinogenic risk through this pathway. The multivariate statistical analysis revealed the influence of physicochemical parameters on the detected PAHs and also showed the PAHs' sources to be mainly combustion, pyrolysis, and vehicular emission.

Chitosan-supported metal nanocatalysts for the reduction of nitroaromatics

The second most abundant natural polymer in the earth's crust is chitosan (CS). The unique physical, chemical, structural, and mechanical features of this natural polymer have led to its increased application in a variety of fields such as medicine, catalysis, removal of pollutants, etc. To eliminate various pollutants, it is preferable to employ natural compounds as their use aids the removal of contaminants from the environment. Consequently, employing CS to eliminate contaminants is a viable choice. For this aim, CS can be applied as a template and support for metal nanoparticles (MNPs) and prevent the accumulation of MNPs as well as a reducing and stabilizing agent for the fabrication of MNPs. Among the pollutants present in nature, nitro compounds are an important and wide category of biological pollutants. 4-Nitrophenol (4-NP) is one of the nitro pollutants. There are different ways for the removal of 4-NP, but the best and most effective method for this purpose is the application of a metallic catalyst and a reducing agent. In this review, we report the recent developments regarding CS-supported metallic (nano)catalysts for the reduction of nitroaromatics such as nitrophenols, nitroaniline compounds, nitrobenzene, etc. in the presence of reducing agents. The metals investigated in this study include Ag, Au, Ni, Cu, Ru, Pt, Pd, etc.

Advances in two-dimensional engineered nanomaterials applications for the agro- and food-industries

Two-dimensional nanomaterials, such as graphene, transition metal dichalcogenides, MXenes, and other layered compounds, are the subject of intense theoretical and experimental research for applications in a wide range of advanced technological solutions, given their outstanding physical, chemical, and mechanical properties. In the context of food science and technology, their contributions are starting to appear, based on the advantages that two-dimensional nanostructures offer to agricultural- and food-related key topics, such as sustainable water use, nano-agrochemicals, novel nanosensing devices, and smart packaging technologies. These application categories facilitate the grasping of the current and potential uses of such advanced nanomaterials in the field, backed by their advantageous physical, chemical, and structural properties. Developments for water cleaning and reuse, efficient nanofertilizers and pesticides, ultrasensitive sensors for food contamination, and intelligent nanoelectronic disposable food packages are among the most promising application examples reviewed here and demonstrate the tremendous impact that further developments would have in the area as the fundamental and applied research of two-dimensional nanostructures continues. We expect this work will contribute to a better understanding of the promising characteristics of two-dimensional nanomaterials that could be used for the design of novel and feasible solutions in the agriculture and food areas. © 2023 Society of Chemical Industry.

Environmental hazards posed by mine dust, and monitoring method of mine dust pollution using remote sensing technologies: An overview

The over-exploitation of mineral resources has led to increasingly serious dust pollution in mines, resulting in a series of negative impacts on the environment, mine workers (occupational health) and nearby residents (public health). For the environment, mine dust pollution is considered a major threat on surface vegetation, landscapes, weather conditions and air quality, leading to serious environmental damage such as vegetation reduction and air pollution; for occupational health, mine dust from the mining process is also regarded as a major threat to mine workers' health, leading to occupational diseases such as pneumoconiosis and silicosis; for public health, the pollutants contained in mine dust may pollute surrounding rivers, farmlands and crops, which poses a serious risk to the domestic water and food security of nearby residents who are also susceptible to respiratory diseases from exposure to mine dust. Therefore, the second section of this paper combines literature research, statistical studies, and meta analysis to introduce the public mainly to the severity of mine dust pollution and its hazards to the environment, mine workers (occupational health), and residents (public health), as well as to present an outlook on the management of mine dust pollution. At the same time, in order to propose a method for monitoring mine dust pollution on a regional scale, based on the Dense Dark Vegetation (DDV) algorithm, the third section of this paper analysed the aerosol optical depth (AOD) change in Dexing City of China using the data of 2010, 2014, 2018 and 2021 from the NASA MCD19A2 Dataset to explore the mine dust pollution situation and the progress of pollution treatment in Dexing City from 2010 to 2021. As a discussion article, this paper aims to review the environmental and health risks caused by mine dust pollution, to remind the public to take mine dust pollution seriously, and to propose the use of remote sensing technologies to monitor mine dust pollution, providing suggestions for local governments as well as mines on mine dust monitoring measures.

Investigation of Cu Adsorption and Migration with Spectral Induced Polarization in Activated Carbon

In this paper, the adsorption process of copper ions on activated carbon (AC) was simulated in a column test. It was deduced that it is consistent with the pseudo-second-order model. Cation exchange was observed to be the major mechanism of Cu-AC interactions through scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) measurements. Adsorption isotherms were fitted well using the Freundlich model. Adsorption thermodynamics at 298, 308, 318 K demonstrated that the adsorption process is spontaneous and endothermic. Spectral induced polarization (SIP) technique was used to monitor the adsorption process, and the double Cole-Cole model was used to analyze the SIP results. The normalized chargeability was proportional to the adsorbed copper content. Two measured relaxation times from the SIP testing were converted into the average pore sizes of 2, 0.8, 0.6, 100-110, 80-90, and 53-60 µm by the Schwartz equation, which are consistent with the measured pore sizes from both mercury intrusion porosimetry and scanning electron microscopy (SEM). The reduction in the pore sizes by SIP during the flow-through tests suggested that the adsorbed Cu²⁺ gradually migrated into small pores as with continued permeation of the influent. These results showcased the feasibility of using SIP technique in engineering practice involving the monitoring of copper contamination in land near a mine waste dump or in adjacent permeable reactive barriers.

Evaluation of dissolved and acid-leachable trace element concentrations in relation to practical water quality standards in the Syr Darya, Aral Sea Basin, South Kazakhstan

The Syr Darya is one of the major rivers supplying the Aral Sea with freshwater. Soviet programs aimed at maximizing agricultural productivity in the Syr Darya basin increased diversion of water drastically affecting its water quality with significant consequences to its suitability for irrigation, fisheries and other uses. While water quality standards for trace elements are typically measured in the dissolved phase, there is evidence that adsorbed phases may also be relevant. Here we report potentially available heavy metals and metalloid concentrations in the Syr Darya water through the treatment of unfiltered waters samples with dilute nitric acid. Significant differences were found for most studied elements (Mann-Whitney U Test, p < 0.05) between their dissolved and acid-leachable concentrations. For Sr and Se in both sampling campaigns, no significant differences were found between their dissolved and acid-leachable concentrations, indicating their low geochemical reactivity. Dissolved V concentrations and acid-leachable Ni and Zn were found to exceed Kazakhstan Maximum Permissible Concentrations (MPC) values for the protection of fishery water quality. Our study evaluates the importance of considering regulatory issues of measuring trace metal concentrations to assess the water suitability for fisheries and irrigation.

Research progresses on the application of perovskite in adsorption and photocatalytic removal of water pollutants

The problem of global water pollution and scarcity of water resources is becoming increasingly serious. Multifunctional perovskites can well drive adsorption and photocatalytic reactions to remove water pollutants. There are many advantages of perovskites, such as abundant oxygen vacancies, easily tunable structural morphology, stable crystal state, highly active metal sites, and a wide photo response range. However, there are few reviews on the simultaneous application of perovskite to adsorption and photocatalytic removal of water pollutants. Thus, this paper discusses the preparation methods of perovskite, the factors affecting the adsorption of water environmental pollutants by perovskite, and the factors affecting perovskite photocatalytic water pollutants. The particle size, specific surface area, oxygen vacancies, electron-hole trapping agents, potentials of the valence band, and conduction band in perovskites are significant influencing factors for adsorption and photocatalysis. Strategies for improving the performance of perovskites in the fields of adsorption and photocatalysis are discussed. The adsorption behaviors and catalytic mechanisms are also investigated, including adsorption kinetics and thermodynamics, electrostatic interaction, ion exchange, chemical bonding, and photocatalytic mechanism. It summarizes the removal of water pollutants by using perovskites. It provides the design of perovskites as high-efficiency adsorbents and catalysts for developing new technologies.

Heavy metals in Chinese freshwater fish: Levels, regional distribution, sources and health risk assessment

China is a major producer and consumer of freshwater fish, which can provide nutrients to the human body but is also of great concern because of the bioaccumulation and amplification of heavy metals that are directly related to human health. In this paper, we reviewed the accumulation and distribution patterns of lead (Pb), arsenic (As), mercury (Hg), cadmium (Cd), and chromium (Cr) in freshwater fish from 2010 to 2020 in nine basins of China (Yangtze River, Pearl River, Yellow River, Haihe River, Huaihe River, Songhua and Liaohe River, Continental, Southeast, and Southwest basins), assessed the health risks, and compared them with those in Chinese marine fish, international freshwater fish, Chinese wild freshwater fish, and artificially cultured freshwater fish. The results showed that 1) the pollution status of the five heavy metals in freshwater fish from nine basins in China is at an intermediate level internationally; 2) the magnitude of heavy metal concentration in four types of artificially farmed freshwater fish and wild freshwater fish is ranked as follows: rice-farmed fish < cage-farmed fish < pond-farmed fish < lake-farmed fish < wild fish; 3) the noncarcinogenic risk factors for heavy metals in freshwater fish in the nine major basins in China were <1 for adults, but the noncarcinogenic risk factors for heavy metals in freshwater fish in the Yellow River, Yangtze River, Pearl River, Songhua and Liaohe River, and Huaihe River basins were all >1 for children.

Use of Wild Rice (Zizania palustris L.) in Paddy-Scale Bioassays for Assessing Potential Use of Mining-Influenced Water for Irrigation

As surface water resources become more intensely used, and occasionally non-useable, consideration of non-conventional water resources for anthropogenic use has become more prevalent. Potentially critical non-conventional water sources include flooded mine-pit lakes. However, water in these lakes can contain potentially problematic concentrations of contaminants of concern. We evaluated the potential use of elevated sulphate (SO₄) mining-influenced waters with low to non-detect metals concentrations for irrigation of wild rice (Zizania palustris L.; WR), a culturally and economically important species. Two flow-through in-situ paddies were developed adjacent to two mine-pit lakes with differing chemical water characteristics; specifically, Pit A contained ≈350 mg SO4 L^-1 and Pit C contained ≈1350 mg SO4 L^-1. Throughout the course of multiple consecutive growing seasons, no adverse WR responses to these mining-influenced water exposures were observed. Based on data and observations from this study, potential use of mining-influenced waters containing elevated SO₄ as the primary contaminant for appropriate irrigation purposes is supported. However, site-specific conditions and potential environmental risks must be considered prior to use of mining-influenced waters for anthropogenic applications.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10230-022-00908-0.

Occurrence, sources and spatial distribution of n-alkanes in surface soils from the Amu Darya Delta, Uzbekistan, arid Central Asia

Central Asia (CA) has attracted global attention because of either water scarcity or ecosystem degradation. The Amu Darya Delta (ADD), one of the most important oases in CA, is endowed with valuable wetlands and biological resources that provide good ecosystem services to inhabitants. However, the region has experienced climate warming and large-scale anthropogenic changes since the last century. To assess the influences of anthropogenic interventions on the soil environment in this area, surface soil samples collected from the ADD were analysed for aliphatic hydrocarbon fractions and five heavy metals (HMs; including Cd, Zn, Cu, Ni and V). The results indicated that the n-alkanes extracted from surface soils were composed of homologous series from C14 to C35. Relatively high abundances of short-chain n-alkanes (<n-C21) were observed in cluster 1 samples (mainly from the lakeshore of the Aral Sea), while significantly high abundances of mid-chain (n-C21 to n-C25) and long-chain (n-C26 to n-C32) n-alkanes were found in cluster 3 samples, which were distributed in urban and agricultural drainage areas. In addition, very-long-chain n-alkanes (>n-C33) occurred in most surface soils, which might be a sign of a hot and arid climatic environment. Notably, almost all samples presented a clear even carbon dominance of short-chain n-alkanes, especially for cluster 1, which possibly represented the influence of hydrocarbon contamination and highly saline carbonate environments in addition to bacterial degradation. The biomarker indices and HM enrichment index indicated greater effects of crude oil pollution on cluster 1 (specifically samples 2, 4, 5, 6, 13, 16 and 34) and anthropogenic activities such as traffic emissions and agricultural drainage on cluster 3 samples. The results of this study provide evidence that the n-alkane composition and abundance in surface soils respond sensitively to anthropogenic interventions, arid climate and petroleum hydrocarbon pollution.

Advances from conventional to real time detection of heavy metal(loid)s for water monitoring: An overview of biosensing applications

The rapid growth of the industrial sector has expedited the accumulation of heavy metal(loid)s in the environment at hazardous levels. The elements such as arsenic, lead, mercury, cadmium and chromium are lethal in terms of toxicity with severe health impacts. With issues like water scarcity, limitations in wastewater treatment, and costs pertaining to detection in environmental matrices; their rapid and selective detection for reuse of effluents is of the utmost priority. Biosensors are the futuristic tool for the accurate qualitative and quantitative analysis of a specific analyte and integrate biotechnology, microelectronics and nanotechnology to fabricate a miniaturized device without compromising the sensitivity, specificity and accuracy. The characteristic features of supporting matrix largely affect the biosensing ability of the device and incorporation of highly sensitive and durable metal organic frameworks (MOFs) are reported to enhance the efficiency of advanced biosensors. Electrochemical biosensors are among the most widely developed biosensors for the detection of heavy metal(loids), while direct electron transfer approach from the recognition element to the electrode has been found to decrease the chances of interference. This review provides an insight into the recent progress in biosensor technologies for the detection of prevalent heavy metal(loid)s; using advanced support systems such as functional metal-based nanomaterials, carbon nanotubes, quantum dots, screen printed electrodes, glass beads etc. The review also delves critically in comparison of various techno-economic studies and the latest advances in biosensor technology.

The mechanism of arbuscular mycorrhizal enhancing cadmium uptake in Phragmites australis depends on the phosphorus concentration

Arbuscular mycorrhizal fungi (AMF) is a vital strategy to enhance the phytoremediation of cadmium (Cd) pollution. However, the function of AMF was influenced by phosphorus (P) concentration. To reveal the effect of AMF on the Cd accumulation of host plants under different P concentrations and how the AMF and P interact, this study comparatively analyzed the regulatory effects of AMF on the Cd response, extraction, and transportation processes of Phragmites australis (P. australis) under different P levels, and explored its physiological, biochemical and molecular biological mechanisms. The study showed that AMF could induce different growth allocation strategies in response to Cd stress. Moreover, AMF promoted plant Cd tolerance and detoxification by enhancing P uptake, Cd passivation, Cd retention in the cell wall, and functional group modulation. Under P starvation treatments, AMF promoted Cd uptake by inducing Cd to enter the iron pathway, increased the transport coefficient by 493.39%, and retained Cd in stems. However, these effects disappeared following the addition of P. Additionally, AMF up-regulated the expression of ZIP, ZIP, and NRAMP genes to promote cadmium uptake at low, medium, and high phosphorus levels, respectively. Thus, the Cd response mechanism of the AMF-P. australis symbiotic system was P dose-dependent.

Use of whole-cell bioreporters to assess bioavailability of contaminants in aquatic systems

Water contamination has become increasingly a critical global environmental issue that threatens human and ecosystems’ health. Monitoring and risk assessment of toxic pollutants in water bodies is essential to identifying water pollution treatment needs. Compared with the traditional monitoring approaches, environmental biosensing via whole-cell bioreporters (WCBs) has exhibited excellent capabilities for detecting bioavailability of multiple pollutants by providing a fast, simple, versatile and economical way for environmental risk assessment. The performance of WCBs is determined by its elements of construction, such as host strain, regulatory and reporter genes, as well as experimental conditions. Previously, numerous studies have focused on the design and construction of WCB rather than improving the detection process and commercialization of this technology. For investigators working in the environmental field, WCB can be used to detect pollutants is more important than how they are constructed. This work provides a review of the development of WCBs and a brief introduction to genetic construction strategies and aims to summarize key studies on the application of WCB technology in detection of water contaminants, including organic pollutants and heavy metals. In addition, the current status of commercialization of WCBs is highlighted.

Facile Synthesis and Life Cycle Assessment of Highly Active Magnetic Sorbent Composite Derived from Mixed Plastic and Biomass Waste for Water Remediation

Plastic and biomass waste pose a serious environmental risk; thus, herein, we mixed biomass waste with plastic bottle waste (PET) to produce char composite materials for producing a magnetic char composite for better separation when used in water treatment applications. This study also calculated the life cycle environmental impacts of the preparation of adsorbent material for 11 different indicator categories. For 1 functional unit (1 kg of pomace leaves as feedstock), abiotic depletion of fossil fuels and global warming potential were quantified as 7.17 MJ and 0.63 kg CO₂ equiv for production of magnetic char composite materials. The magnetic char composite material (MPBC) was then used to remove crystal violet dye from its aqueous solution under various operational parameters. The kinetics and isotherm statistical theories showed that the sorption of CV dye onto MPBC was governed by pseudo-second-order, and Langmuir models, respectively. The quantitative assessment of sorption capacity clarifies that the produced MPBC exhibited an admirable ability of 256.41 mg g^-1. Meanwhile, the recyclability of 92.4% of MPBC was demonstrated after 5 adsorption/desorption cycles. Findings from this study will inspire more sustainable and cost-effective production of magnetic sorbents, including those derived from combined plastic and biomass waste streams.

The Role of Conventional Methods and Artificial Intelligence in the Wastewater Treatment: A Comprehensive Review

Water pollution is a severe health concern. Several studies have recently demonstrated the efficacy of various approaches for treating wastewater from anthropogenic activities. Wastewater treatment is an artificial procedure that removes contaminants and impurities from wastewater or sewage before discharging the effluent back into the environment. It can also be recycled by being further treated or polished to provide safe quality water for use, such as potable water. Municipal and industrial wastewater treatment systems are designed to create effluent discharged to the surrounding environments and must comply with various authorities’ environmental discharge quality rules. An effective, low-cost, environmentally friendly, and long-term wastewater treatment system is critical to protecting our unique and finite water supplies. Moreover, this paper discusses water pollution classification and the three traditional treatment methods of precipitation/encapsulation, adsorption, and membrane technologies, such as electrodialysis, nanofiltration, reverse osmosis, and other artificial intelligence technology. The treatment performances in terms of application and variables have been fully addressed. The ultimate purpose of wastewater treatment is to protect the environment that is compatible with public health and socioeconomic considerations. Realization of the nature of wastewater is the guiding concept for designing a practical and advanced treatment technology to assure the treated wastewater’s productivity, safety, and quality.

Graphene oxide-based nanomaterials for the treatment of pollutants in the aquatic environment: Recent trends and perspectives - A review

Graphene oxide can be used to store energy, as electrodes and purify industrial and domestic wastewater as photocatalysts and adsorbents because of its remarkable thermal, electrical, and chemical capabilities. Toward understanding graphene oxide (GO) based nanomaterials considering the background factors, the present review study investigated their characteristics, preparation methods, and characterization processes. The removal of contaminants from wastewater has recently been a focus of attention for materials based on GO. Progress in GO synthesis and surface modification has shown that they can be used to immobilize enzymes. It is possible to immobilize enzymes with varying characteristics on graphene-oxide-based substrates without sacrificing their functioning, thus developing a new environmental remediation platform utilizing nano biocatalysts. GO doping and co-doping with a variety of heterogeneous semiconductor-based metal oxides were included in a brief strategy for boosting GO efficiency. A high band-gap material was also explored as a possibility for immobilization, which shifts the absorption threshold to the visible range and increases photoactivity. For water treatment applications, graphene-based nanomaterials were used in Fenton reactions, photocatalysis, ozonation, photo electrocatalysis, photo-Fenton, and a combination of photon-Fenton and photocatalysis. Nanoparticles made from GO improved the efficiency of composite materials when used for their intended applications. As a result of the analysis, prospects and improvements are clear, especially when it comes to scaling up GO-based wastewater treatment technologies.

The research trend on arsenic pollution in freshwater: a bibliometric review

We conducted a quantitative and qualitative bibliometric analysis based on 8740 research articles from the Web of Science Core Collection published in the last 20 years (2000-2020) for a better understanding of the research progress and development trend of arsenic pollution in freshwater (FAP). The results showed a significant increase in the number of publications from 2007 to 2020, especially after 2015. Four of the top 10 productive authors are from China. Two of the top three research institutions are from China, and the publications of Chinese Academy of Sciences accounted for 5.40% of the total. China is also the center of the national cooperation network, indicating a greater influence of China in this scientific research field. The top three journals included Science of the Total Environmental, Environmental Science Technology, and Journal of Hazardous Materials. Besides arsenic, the high-frequency keywords in this field included adsorption, contamination, groundwater, removal, detection, and geochemistry. The researchers mainly focused on the groundwater environment, as well as the pollution hazards of arsenic in water bodies, remediation techniques, detection, migration, and transformation. Studies should pay more attention to the application and development of phytoremediation technology in the field of FAP in the future.

Application of Cement Paste in Mining Works, Environmental Protection, and the Sustainable Development Goals in the Mining Industry

Cement paste is an already well-known material used in ore mining. It is mainly used to fill excavation areas and the tailings from the surface return to underground mines. In this way, the amount of deposited material and degradation of the surface of the terrain are reduced. The paste itself can be used as an artificial barrier between mining works and underground watercourses. Significant economic and environmental benefits can be expected from using cement paste, which would contribute to sustainable development. The basic materials that make up cemented paste backfill (CPB) are flotation tailings, cement, and water. For CPB to be adequately and safely applied to the filling of excavation spaces and indirectly to the protection of the groundwater, environment, and sustainable development of the mining industry, it must meet certain physical–mechanical, physicochemical, and deformation properties. This paper presents the results of synthesized and analyzed samples of different compositions based on flotation tailings (from the production of ZiJin Copper in Bor, Serbia), cement, and water. The methods used for chemical and mineralogical tests include inductively coupled plasma atomic emission spectroscopy (ICP-AES), atomic absorption spectroscopy (AAS), X-ray diffraction analysis (XRD), and nephelometric turbidity units (NTUs; turbidimetry). The results prepared with CPB consisting of 5% cement, 24% water, and 71% flotation tailings were the most acceptable.

Polarimetry-inspired feature fusion spectroscopy (PIFFS) for ammonia sensing in water

The sustainable use of water resources is inseparable from water pollution detection. The sensing of toxic ammonia nitrogen in water currently requires auxiliary reagents, which may cause secondary pollution. Benefiting from the ability of substances to change light characteristics, this work proposes polarimetry-inspired feature fusion spectroscopy (PIFFS) to detect ammonia. The PIFFS system mainly includes a light source, a quarter-wave plate (QWP), a linear polarizer (LP) and a fiber spectrometer. The target light containing substance information is polarization modulated by adjusting the QWP and LP angles. Then, the Stokes parameters of target light can be calculated by appropriate modulations. The feasibility of PIFFS method to detect ammonia nitrogen is verified by experiments on both standard water samples and environmental water samples. Experimental results show that inspired by the first Stokes parameter, the fused features provide superiority in classifying ammonia concentration. The results also demonstrate the effectiveness of support vector machine-based concentration classification and random forests-based spectral selection. The interaction between light and substances ensures that the proposed PIFFS method has the potential to detect other pollutants.

The effect of phosphate mining activities on rhizosphere bacterial communities of surrounding vegetables and crops

The effects of phosphate mining on rhizosphere bacteria in surrounding vegetables and crops, including Lactuca sativa, Glycine max, and Triticum aestivum, are assessed in this study. As results, phosphate mining significantly increased the contents of some large elements, trace elements, and heavy metals in the surrounding agricultural soil, including phosphorus, magnesium, boron, cadmium, lead, arsenic, zinc, and chromium (P < 0.05). The community richness and diversity of bacteria in rhizosphere of the three crops were significantly reduced by phosphate mining (P < 0.05). Abundances of Sphingomonas and RB41 in the rhizosphere soil of phosphate mining area improved compared with the baseline in the non-phosphate mining area. Beta diversity analysis indicated that phosphate mining led to the differentiation of bacterial community structure in plant rhizospheres. Bacterial metabolic analysis indicated that different plant rhizosphere microbial flora developed various metabolic strategies in response to phosphate mining stress, including enriching unsaturated fatty acids, antibiological transport systems, cold shock proteins, etc. This study reveals the interaction between crops, rhizosphere bacteria, and soil pollutants. Select differentiated microbial strains suitable for specific plant rhizosphere environments are necessary for agricultural soil remediation. Additionally, the problem of destruction of agricultural soil and microecology caused by phosphate mining must be solved.

Designing Multi-Stage 2 A/O-MBR Processes for a Higher Removal Rate of Pollution in Wastewater

Multi-stage A/O-MBR processes were designed to improve wastewater treatment efficiency; three different designs were carried out and compared in this study. The 2(A/O)-MBR process, i.e., with two sets of anoxic/oxic tanks in series, showed better effluent quality than A/O-MBR and 3(A/O)-MBR processes. The removal rates of COD, NH4+-N, TP and TN were 95.29%, 89.47%, 83.55% and 78.58%, respectively, complying satisfactorily with China’s urban sewage treatment plant pollutant discharge standards. In terms of membrane fouling, the 3(A/O)-MBR process demonstrated the lowest fouling propensity. The microbial community structure in each bioreaction tank was analyzed, the results from which matched with the process efficiency and fouling behavior.

Distribution, Genesis, and Human Health Risks of Groundwater Heavy Metals Impacted by the Typical Setting of Songnen Plain of NE China

Heavy metals pollution in groundwater and the resulting health risks have always been an environmental research hotspot. However, the available information regarding this topic and associated methods is still limited. This study collected 98 groundwater samples from a typical agricultural area of Songnen Plain in different seasons. The pollution status and sources of ten heavy metals (As, Ba, Cd, Co, Cr (VI), Cu, Fe, Mn, Ni, Pb, and Zn) were then analyzed and compared. In addition, the human health risks assessment (HHRA) model was used to calculate human health risks caused by heavy metals in groundwater. The results revealed that heavy metals were mainly distributed in the northwest of the study area and along the upper reaches of the Lalin river and that the concentrations of heavy metals were higher during the wet season than the dry season. Industrial and agricultural activities and natural leaching are the main sources, and each kind of heavy metal may have different sources. Fe and Mn are the primary pollutants, mainly caused by the native environment and agricultural activities. The exceeding standard rates are 71.74% and 61.54%, respectively based on the Class III of Quality Standard for Groundwater of China (GB/T 14848-2017). The maximum exceeding multiple are 91.45 and 32.05, respectively. The health risks of heavy metals borne by different groups of people were as follows: child > elder > young > adult. Carcinogenic heavy metals contribute to the main risks, and the largest risks sources are Cr and As. Therefore, the government should appropriately restrict the use of pesticides and fertilizers, strictly manage the discharge of enterprises, and control man-made heavy metals from the source. In addition, centralized water supply and treatment facilities shall be established to prevent the harm of native heavy metals.