Integrated framework to assess soil potentially toxic element contamination through 3D pollution analysis in a typical mining city

Soil potentially toxic elements (PTEs) pollution of contaminated sites has become a global environmental issue. However, given that previous studies mostly focused on pollution assessment in surface soils, the current status and environmental risks of potentially toxic elements in deeper soils remain unclear. The present study aims to cognize distribution characteristics and spatial autocorrelation, pollution levels, and risk assessment in a stereoscopic environment for soil PTEs through 3D visualization techniques. Pollution levels were assessed in an integrated manner by combining the geoaccumulation index (Igeo), the integrated influence index of soil quality (IICQs), and potential ecological hazard index. Results showed that soil environment at the site was seriously threatened by PTEs, and Cu and Cd were ubiquitous and the predominant pollutants in the study area. The stratigraphic models and pollution plume simulation revealed that pollutants show a decreasing trend with the deepening of the soil layer. The ranking of contamination soil volume is as follows: Cu > Cd > Zn > As > Pb > Cr > Ni. According to the IICQs evaluation, this region was subject to multiple PTE contamination, with more than 60% of the area becoming seriously and highly polluted. In addition, the ecological hazard model revealed the existence of substantial ecological hazards in the soils of the site. The integrated potential ecological risk index (RI) indicated that 45.7%, 10.13%, and 4.15% of the stereoscopic areas were in considerable, high, and very high risks, respectively. The findings could be used as a theoretical reference for applying multiple methods to integrate evaluation through 3D visualization analysis in the assessment and remediation of PTE-contaminated soils.

Persistent pollution of genetic materials in a typical laboratory environment

From the onset of coronavirus disease (COVID-19) pandemic, there are concerns regarding the disease spread and environmental pollution of biohazard since studies on genetic engineering flourish and numerous genetic materials were used such as the nucleic acid test of the severe acute respiratory syndrome coronavirus (SARS-CoV-2). In this work, we studied genetic material pollution in an institute during a development cycle of plasmid, one of typical genetic materials, with typical laboratory settings. The pollution source, transmission routes, and pollution levels in laboratory environment were examined. The Real-Time quantitative- Polymerase Chain Reaction results of all environmental mediums (surface, aerosol, and liquid) showed that a targeted DNA segment occurred along with routine experimental operations. Among the 79 surface and air samples collected in the genetic material operation, half of the environment samples (38 of 79) are positive for nucleic acid pollution. Persistent nucleic acid contaminations were observed in all tested laboratories and spread in the public area (hallway). The highest concentration for liquid and surface samples were 1.92 × 108 copies/uL and 5.22 × 107 copies/cm2, respectively. Significant amounts of the targeted gene (with a mean value of 74 copies/L) were detected in the indoor air of laboratories utilizing centrifuge devices, shaking tables, and cell homogenizers. Spills and improper disposal of plasmid products were primary sources of pollution. The importance of establishing designated experimental zones, employing advanced biosafety cabinets, and implementing highly efficient cleaning systems in laboratories with lower biosafety levels is underscored. SYNOPSIS: STATEMENT. Persistent environmental pollutions of genetic materials are introduced by typical experiments in laboratories with low biosafety level.

Distribution, sources and influencing factors of heavy metals in the Ledong Sea, South China Sea

The Ledong Sea Area is located on the southwest side of Hainan Island. In recent years, with the development of industrialization and urbanization, the problem of heavy metals in marine sediments has gradually become a global problem, and research on this topic is of great significance for nearshore environmental protection and coastal management. This paper analysed the heavy metal content of 97 surface sediments in the Ledong Sea, indicating unpolluted to moderately polluted and low to moderate risk. Cu, Zn, Hg, Pb, Cr, and Cd are highly correlated, with similar origins, and originate from rivers carrying industrial wastewater, domestic sewage, and weathered material from the parent rocks, which are subsequently redistributed under the action of ocean dynamics. The distribution of Hg is mainly influenced by feed and biological metabolites during the farming process. As originates from rivers carrying large amounts of agricultural pesticide and fertilizer residues.

A water quality assessment model involving novel fluorescence technology

The reasonable utilization of water resources and real-time monitoring of water pollution are the core tasks of current world hydrological and water conservancy work. Novel technologies and methods for monitoring water pollution are important means to ensure water health. However, the absence of intuitive and simple analysis methods for the assessment of regional pollution in large-scale water bodies has prevented scientists from quickly grasping the overall situation of water pollution. In this study, we propose a strategy based on the unique combination of fluorescence technology and simple kriging (SK) interpolation (FL-SK) for the first time. This strategy could present the relative magnitude and distribution of the physicochemical indicators of a whole natural lake intuitively and accurately. The unique FL-SK model firstly offers a simple and effective water quality method that provides the pollution index of different sampling points in lakes. The macroscopic evaluation of large-scale water bodies by the FL-SK model primarily relies on the fluorescence response of the RDM-TPE to the comprehensive indicators of the water body, as experimental results have revealed a good correlation between fluorescent responses and six normalized physicochemical indicators. Multiple linear regression and fluorescence response experiments on RDM-TPE indicate that to some extent, the fluorescence signals of the FL-SK model may originate from a certain type of sulfide in the water body. Pattern discovery could enable the analysis of pollution levels in other ecosystems and promote early pollution assessment in the future.

Geochemical evaluation, ecological and human health risk assessment of potentially toxic elements in urban soil, Southern India

Roadside soil contamination is mostly caused by human-caused pollutant deposition. PTEs are among the many substances that are harmful for both humans and the environment. PTE concentrations in roadside soil in Chennai, southern India, have been determined in this study. To evaluate the seriousness of the threats, more environmental and geochemical indices have been applied. 83 soil samples have been obtained from the study regions and focusing on important roads. Elemental analysis has been analyzed with ED-XRF and sieve-filtered samples focused on PTEs such as arsenic, barium, cobalt, chromium, copper, iron, potassium, nickel, lead, thorium, titanium, zinc, and uranium. Significant metallic variations have been found in soil samples around roads by the investigation. The elements this study examined section ascending in the following sequence: Fe > Ti > Zn > Cr > Pb > Cu > Ni > Th > As > U > K. In the research area, the CD classification denotes high contamination, whereas the CF indices show mild to significant pollution. PLI indicates moderate to high pollution, whereas EF suggests excessive enrichment. Igeo demonstrates a range from uncontaminated to highly contaminated. PERI showed high levels in the northern study region, whereas GUFI shows several hot spots indicating moderate to severe pollution. The Hazard Index (HI) values for all metals were less than one, demonstrating the absence of non-carcinogenic risks for both adults and children. Multivariate data show natural and anthropogenic PTEs in roadside soil. In addition, a soil quality monitoring system is needed to mitigate continual contamination risks.

Spatial distribution characteristics and pollution evaluation of soil heavy metals in Wulongdong National Forest Park

To scrutinize the spatial distribution attributes of soil heavy metal content and discern its pollution status within the expanse of Wulongdong National Forest Park, a meticulous investigation is imperative. Three altitude gradients of 900, 1000, and 1069 m were selected on the shady and sunny slopes of Wulongdong National Forest Park, and a total of 300 soil sample points were collected. Soil samples were collected in layers, and the contents of seven soil heavy metal elements, Cr, Cd, Hg, Ni, Se, As, and Pb, were measured. With regard to the national soil element background values, the single factor index method, Nemerow index method, and pollution load index were employed to undertake a thorough assessment of soil heavy metal pollution. (1) The contents of heavy metal elements Cr, Se, As, and Pb in the 0-20 cm soil layer of Wulongdong National Forest Park are lower than the national soil element background value and the Henan soil element background value; the Cd and Hg contents exceed the national soil element background value. The value and Henan soil element background value are 2.2 times and 2.92 times the national soil element background value, and 2.75 times and 9.5 times the Henan soil element background value respectively; Ni content is lower than the Henan soil element background value, but higher than the national soil element background value. The background value is 1.03 times its content. The coefficients of variation of the contents of seven heavy metal elements are all greater than 50%, among which Hg shows extreme variation, and the remaining six are highly variable. (2) In the same soil layer, the Cr and As contents are lower on sunny slopes than on shady slopes, and the contents of Pb, Ni, and Hg are generally higher on sunny slopes than on shady slopes. On sunny slopes, the contents of As, Cd, and Hg decrease with increasing altitude, and the Se content increases with increasing altitude; while on shady slopes, the contents of Cr, Se, and As decrease with increasing altitude, and Pb and Hg content increase with the increase of altitude; the content of heavy metal element As increases with the deepening of the soil layer on shady slopes, and the Hg content decreases with the deepening of the soil layer on sunny slopes. The contents of other heavy metal elements have no obvious regularity among different slope directions, altitudes and soil layers. (3) The single factor index evaluation results show that in the 0 ~ 20c soil layer and on the sunny slope, Hg is heavily polluted, Cd is moderately polluted, Ni is lightly polluted, and Cr, Se, As, and Pb are all non-polluted; On the shady slope, Cd and Hg are moderately polluted, and the other five heavy metal elements are in a non-polluting state. (4) The Nemerow index method evaluation results show that in the 0 ~ 20 cm soil layer, the soil on sunny slopes is significantly more polluted by heavy metals than on shady slopes, and the main pollutants are Ni, Cd and Hg. (5) In the 0 ~ 20 cm soil layer of Wulongdong National Forest Park, the three heavy metal elements Ni, Cd and Hg have reached pollution levels, of which Ni is slightly polluted, Cd and Hg are moderately or above polluted; the sunny slope soil is slightly polluted. Heavy metal pollution, no heavy metal pollution on shady slopes.

Health and ecological risk of heavy metals in agricultural soils related to Tungsten mining in Southern Jiangxi Province, China

Background

Dayu County, a major tungsten producer in China, experiences severe heavy metal pollution. This study evaluated the pollution status, the accumulation characteristics in paddy rice, and the potential ecological risks of heavy metals in agricutural soils near tungsten mining areas of Dayu County. Furthermore, the impacts of soil properties on the accumulation of heavy metals in soil were explored.

Methods

The geo-accumulation index (Igeo), the contamination factor (CF), and the pollution load index (PLI) were used to evaluate the pollution status of metals (As, Cd, Cu, Cr, Pb, Mo, W, and Zn) in soils. The ecological risk factor (RI) was used to assess the potential ecological risks of heavy metals in soil. The health risks and accumulation of heavy metals in paddy rice were evaluated using the health risk index and the translocation factor (TF), respectively. Pearson's correlation coefficient was used to discuss the influence of soil factors on heavy metal contents in soil.

Results

The concentrations of metals exceeded the respective average background values for soils (As: 10.4, Cd: 0.10, Cu: 20.8, Cr: 48.0, Pb: 32.1, Mo: 0.30, W: 4.93, Zn: 69.0, mg/kg). The levels of As, Cd, Mo, and tungsten(W) exceeded the risk screening values for Chinese agricultural soil contamination and the Dutch standard. The mean concentrations of the eight tested heavy metals followed the order FJ-S > QL > FJ-N > HL > CJ-E > CJ-W, with a significant distribution throughout the Zhangjiang River basin. Heavy metals, especially Cd, were enriched in paddy rice. The Igeo and CF assessment indicated that the soil was moderately to heavily polluted by Mo, W and Cd, and the PLI assessment indicated the the sites of FJ-S and QL were extremely severely polluted due to the contribution of Cd, Mo and W. The RI results indicated that Cd posed the highest risk near tungsten mining areas. The non-carcinogenic and total carcinogenic risks were above the threshold values (non-carcinogenic risk by HQ > 1, carcinogenic risks by CR > 1 × 10-4 a-1) for As and Cd. Correlation analysis indicated that K2O, Na2O, and CaO are main factors affecting the accumulation and migration of heavy metals in soils and plants. Our findings reveal significant contamination of soils and crops with heavy metals, especially Cd, Mo, and W, near mining areas, highlighting serious health risks. This emphasizes the need for immediate remedial actions and the implementation of stringent environmental policies to safeguard health and the environment.

Cadmium accumulation in tropical island paddy soils: From environment and health risk assessment to model prediction

Cultivated soil quality is crucial because it directly affects food safety and human health, and rice is of primary concern because of its centrality to global food networks. However, a detailed understanding of cadmium (Cd) geochemical cycling in paddy soils is complicated by the multiple influencing factors present in many rice-growing areas that overlap with industrial centers. This study analyzed the pollution characteristics and health risks of Cd in paddy soils across Hainan Island and identified key influencing factors based on multi-source environmental data and prediction models. Approximately 27.07% of the soil samples exceeded the risk control standard screening value for Cd in China, posing an uncontaminated to moderate contamination risk. Cd concentration and exposure duration contributed the most to non-carcinogenic and carcinogenic risks to children, teens, and adults through ingestion. Among the nine prediction models tested, Extreme Gradient Boosting (XGBoost) exhibited the best performance for Cd prediction with soil properties having the highest importance, followed by climatic variables and topographic attributes. In summary, XGBoost reliably predicted the soil Cd concentrations on tropical islands. Further research should incorporate additional soil properties and environmental variables for more accurate predictions and to comprehensively identify their driving factors and corresponding contribution rates.

Environmental quality assessment of heavy metals in the Rongcheng offshore area, Shandong Peninsula, China

Eighteen surface sediment samples collected from the Rongcheng offshore area of China in 2021 were analyzed for heavy metal concentrations, sources, and pollution status. The Cu, Zn, Cr, Cd, As, and total organic carbon (TOC) distributions were similar. In contrast, the distributions of Pb and Hg were irregular, and high concentrations appeared in two or several areas. Occasional adverse effects were observed from pollution caused by Cu, Pb, and As, and none of the heavy metal concentrations exceeded the probable effect level (PEL). The Pearson's correlation coefficient, geoaccumulation index, and principal component analysis were used to distinguish the sources and assess the pollution risk of heavy metals. The results showed that heavy metals did not pollute the surface sediments in the Rongcheng offshore area and that the metals were mainly derived from natural sources.

Effects of terrestrial input on heavy metals in Zhanjiang Bay, a typical subtropical bay in the South China Sea

Understanding the influence of terrestrial inputs on heavy metals in bays is crucial for the environmental protection of regional estuaries and coastal systems. In this study, the concentrations, temporal and regional distribution characteristics, and fluxes of heavy metals (Cr, Cu, Zn, Cd, Pb) in the surface seawater and terrestrial sewage of Zhanjiang Bay (ZJB) in four different seasons were investigated. The results identified the heavy metal concentrations in the sewage outlet around ZJB had significant seasonal variation. The heavy metals in the surface seawater of ZJB had significant spatiotemporal variations. Terrestrial input, biological activity and hydrodynamics affected the overall distribution. The heavy metal emission fluxes indicated that riverine input was the main influencing factor for heavy metals in ZJB (96.22 %). The fluxes of heavy metals into ZJB increased significantly after the typhoon (Cu: 127 %, Zn: 63 %, Pb: 136 %), it was possible to deteriorate the seawater quality.

Pollution and source-specific risk analysis of potentially toxic metals in urban soils of an oasis-tourist city in northwest China

Source-specific risk apportionment for soil potentially toxic metals (PTMs) is of great significance for contamination prevention and risk management in urban environments. Eighty-five urban soil samples were obtained from an oasis-tourist city, China and examined for eight PTMs (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn). The pollution levels, sources, and ecological risk of soil PTMs were quantified, and their source-specific ecological and human health effects were also estimated using the multi-proxy approaches. The results demonstrated that accumulation of Cd, Hg, Pb, Cr, Cu, and Zn in soils was observed compared to their background levels, and the soils experienced varying degrees of PTMs pollution, especially at sites with high-intensity anthropogenic activities. Natural sources, atmospheric deposition, industrial sources, vehicular emissions, and comprehensive inputs were the principal sources, with contributions of 29.28%, 25.86%, 20.13%, 16.50%, and 8.23%, respectively. The integrated ecological risks of PTMs in soils were moderate at most sites, with atmospheric deposition being the dominant contributor to ecological risks. Children exhibited pronounced non-cancer risks, but adults had no notable non-cancer risks. Moreover, there were potential carcinogenic risks for both children and adults within the study region. Non-cancer and carcinogenic risks were more significant for children than adults, and traffic emissions were the primary contributor to non-cancer risks (adults: 20.53%, children: 20.49%) and carcinogenic risks (adults: 22.95%, children: 22.08%). The industrial and traffic activities were considered as priority control sources for soil pollution control and risk management, with Hg, Cd, Zn, and Pb corresponding to the priority elements. This study highlights the source-specific ecological and human health effects of PTMs pollution in urban soils, thereby providing valuable information for targeted pollution control and priority source management.

Evaluation of metal pollution characteristics using water and moss in the Luanchuan molybdenum mining area, China

Luanchuan is rich in molybdenum resources, and mining activities are frequent, but over-mining can cause serious metal pollution to the local environment. To explore the degree of metal pollution caused by mining activities, the content characteristics and spatial distribution of metals in mining areas were studied by measuring the concentrations of Fe, Mn, Zn, Ba, Mo, Cu, Cr, Co, V, and W in surface water and mosses of mining areas. In addition, the metal pollution index (HPI), contamination factor (CF), and pollution load index (PLI) were used to evaluate metal pollution, and factor analysis was used to analyze the sources of metals. The results of the analysis of surface water at the mine site indicate the most abundant element in surface water, with a maximum concentration of 3713.8 μg/L, and its content far exceeds the water quality standard of Class III of the Environmental Quality Standard for Surface Water. The results of the HPI analysis showed that nearly 90% of the surface water was moderately contaminated (HPI ≥ 15). The results of the analysis of atmospheric deposition at the mine site confirm that the metal elements with a high threat to the atmospheric environment are Mo and W. The results of PLI indicate that the level of atmospheric deposition pollution in the study area is severe (PLI > 4). Factor analysis indicated that rock weathering and mining activities were the main sources of metals. This study provides a theoretical basis for the investigation and control of metal pollution in similar metal mining areas.

Source-sink response analysis of heavy metals and soil pollution assessment in non-ferrous metal industrial agglomeration areas based on decision unit

Soil heavy metals (HMs) pollution is a worldwide concern. In this study, decision units based on "source-sink relationship" were established using multi-source data. The source-sink response of heavy metals in agricultural soils at the regional scale was analyzed using machine learning methods, receptor models, and geospatial analysis. The comprehensive pollution risk score (CRS) was proposed by integrating a variety of key evaluation indicators to evaluate the pollution degree of each decision unit. We divided the study area into 193 decision units, the proportions of sites with concentrations of Cd, Hg, As, Pb, and Cr exceeding the most stringent risk screening values were 16.4 %, 2.2 %, 4.0 %, 7.6 %, and 0.2 %, respectively. Agricultural activities (livestock manure, fertilizer, sewage irrigation), industrial activities (rare earth ore and tungsten‑molybdenum mining and smelting), and soil parent material are the dominant pollution sources of HMs in the study area. The risk of contamination of each element is ranked from largest to smallest according to the CRS as Cd > Hg > Pb > As > Cr. The western and southwestern water pollution decision units are the areas with the highest risk of soil HMs contamination. This quantitative evaluation framework can provide a relatively accurate decision basis for soil pollution management.

Spatial distribution, source identification, and risk assessment of heavy metals in riparian soils of the Tibetan plateau

Riparian soils in the lower sections of the Lhasa River were chosen as the research focus, to examine the characteristics and sources of heavy metals in riparian soils of high-cold regions. To investigate the influence of various factors on the geographical distribution of heavy metals, three horizontal and one vertical profiles were considered. The geoaccumulation index, prospective ecological risk index, and enrichment factor were used to evaluate the extent of soil contamination. Correlation analysis and the positive-matrix-analysis receptor model were used to quantitatively examine the sources of the elements. According to the soil-evaluation, the topsoil was more polluted than the deep soil. Overall, the soil was slightly degraded and posed minor ecological concern. Cd was the primary contributor to the overall contamination, with moderate and considerable risk levels at certain locations. Five sources were identified for the six heavy metals. Transportation and agricultural production were the principal sources of Cd. Ni and Cr were mostly connected to agricultural practices and weathering of parent-soil materials. Pb and Zn were mostly related to geological history, geothermal development, and traffic pollution. Mineral resource development has had a major impact on Cu. Non-carcinogenic risk index of each heavy metal and their total value were <1, indicating they are not harmful to human health. The riparian soil of the Lhasa River Basin contains heavy metals from various sources; therefore, it is important to monitor these heavy metals. This study provides a scientific foundation for the safe utilization and classification of soils in high cold regions.

Characterization of heavy metal content distribution and evaluation of soil pollution in Maqin County, Qinghai Province, China

The Qinghai-Tibet Plateau stands as the loftiest geographical area on our planet, frequently denoted as the "Crown of the Globe." To acquire an exhaustive comprehension of the heavy metal contamination situation in the topsoil of Maqin County, Qinghai Province, a total of 1616 surface soil specimens were gathered across a 6300 km2 area. An examination was carried out on 12 metallic elements to investigate the impact of diverse geological contexts, soil categorizations, and land utilization practices on the levels of heavy metals. Additionally, the fundamental factors contributing to these trends were probed. The findings unveiled that the mean levels of the 12 metallic elements in the topsoil of Maqin County surpassed or equaled the baseline values of soil heavy metal concentrations within the research region. The coefficients of variation (CV) values for Hg, Sb, Ni, and Pb exceeded 30%, with Hg showing strong variation. The overall pollution level in the study area was classified as mild, posing a moderate ecological risk. In this study, we performed a multi-factor analysis of the significant differences in heavy metal concentrations among different geological backgrounds, soil types, and land-use types. The results showed that geological background had extremely significant impacts on elements such as Ba, Be, Cd, Cr, Cu, Hg, Ni, Sb, Tl, and Zn (p < 0.01). Soil type had an extremely significant influence on Be, Cd, Cu, and Zn (p < 0.01), as well as a significant influence on Ba (p < 0.05). Land-use type had an extremely significant impact on Ba (p < 0.01) and a significant impact on Cd (p < 0.05). Building upon the amalgamation of the outcomes from the Pearson correlation analysis, it was inferred that the main source of heavy metals in Maqin County, Qinghai Province, was the geological background.

An integrated approach to identify the source apportionment of potentially toxic metals in shale gas exploitation area soil, and the associated ecological and human health risks

Public awareness of the potential environmental risks of shale gas extraction has increased in recent years. However, the status and environmental risks of potentially toxic metals (PTMs) in shale gas field soil remain unclear. A total of 96 topsoil samples were collected from the first shale gas exploitation area in China. The sources of nine PTMs in the soils were identified using positive matrix factorization and correlation analysis, and the ecological and human health risks of toxic metals from different sources under the two land use types were calculated. The results showed that mean pollution load index (PLI) values for farmland (1.18) and woodland (1.40) indicated moderate pollution, As, Cd and Ni were the most serious contaminants among all nine PTMs. The following four sources were identified: shale gas extraction activities (43.90%), nature sources (31.90%), agricultural and traffic activities (17.55%) and industrial activities (6.55%). For ecological risk, the mean ecological risk index (RI) values for farmlands (161.95) and woodlands (185.27) reaching considerable risk. The contribution ratio of shale gas extraction activities for farmlands and woodlands were 5.70% and 8.90%, respectively. Regarding human health risk, noncarcinogenic risks for adults in farmlands and woodlands were negligible. Industrial activities, agricultural and traffic activities were estimated to be the important sources of health risks. Overall, shale gas extraction activities had little impact on the ecological and human health risk. This study provides scientific evidence regarding the soil contamination potential of shale gas development activities.

Distribution, source, and contamination assessment of heavy metals in surface sediments of the Zhifu Bay in northern China

In this study, 30 surface sediment samples were collected from Zhifu Bay in northern China and analyzed for heavy metals; in addition, their concentrations and pollution status were evaluated. The distributions of Cu and Zn were similar and mainly dominated by fine-grained sediments, whereas the other heavy metal distributions were not very regular. Al was positively correlated with Cu and Zn, and weakly correlated with Pb, As, and Hg. Except for some stations that showed minor enrichment and were unpolluted to moderately polluted by Cr, Cd, and Hg, the overall quality of sediments in the study area was good. Three principal components with eigenvalues >1 were estimated, accounting for 72.06 % of the total variability and representing natural sources, natural and anthropogenic, and anthropogenic sources, respectively.

Pollution status determination using trace metals and organic contaminants of the water column in coastal areas of the Red Sea and the Gulf of Aqaba: A baseline assessment

Herein, we aim to provide a baseline assessment of the pollution status of the water column in coastal areas of Saudi Arabia (Red Sea and the Gulf of Aqaba), using trace metals (Cd, Co, Cr, Cu, Ni, Pb and Zn), total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs), in seawater samples obtained from 71 sampling stations in June-July 2021. Concerning trace metals, the maximum concentrations for Co, Cu and Ni were detected in Al-Shuqaiq, whereas the highest Pb and Zn concentrations were found in the Jeddah lagoon waters. Elevated concentrations of TPHs and the highest sum of PAHs were recorded in surface waters of Al Lith, Jeddah lagoon and Jeddah Mena. Overall, the concentrations of all trace metals, TPHs and individual PAHs for which environmental standards have been stipulated for the Kingdom of Saudi Arabia fall well below the threshold values.

Distribution, source, and contamination assessment of heavy metals in surface sediments of the Old Yellow River Estuary in China

To assess the sources and pollution status of heavy metals, surface sediments from the Old Yellow River estuary were systematically sampled and analyzed to determine the concentrations of seven heavy metals. The Pearson's correlation coefficient, enrichment factor, geoaccumulation index, and principal component analysis were used to distinguish the sources and assess the pollution risk of heavy metals. The results showed that the distributions of Al, Fe, Cu, Pb, Zn, Cr, and As were similar and mainly dominated by fine-grained sediments, whereas the distributions of Cd and Hg were irregular. Al was strongly correlated with Fe, Cu, Pb, Zn, As, and Mz, and positively correlated with Cr. Except for Cr, Cd, and Hg, all the other elements were positively correlated with Mz. Multiple indicators indicated that Cu, Pb, Zn, Cr, and As were mainly derived from natural sources, whereas Hg and Cd were derived from anthropogenic sources.

Extreme rainstorm reshuffles the spatial distribution of heavy metals and pollution risk in sediments along the mangrove tidal flat

Mangroves as typical blue carbon ecosystems exhibit a high level of heavy metal accumulation capability. In this study, we investigated how extreme rainstorm effects the spatial variability and pollution risk of sediment heavy metals (i.e., Fe, Mn, Cr, Cu, Zn, Cd, Pb, As and Hg) at different compartments of a typical tidal flat, including the bare mudflat, mangrove zone, and tidal creek in Shenzhen Bay, China. The results showed that the extreme rainstorm can change the sediment particle size, which further regulated the spatial distribution, and source-sink pattern of heavy metals. Due to the strong rainstorm flushing, the concentrations of most heavy metals increased toward the sea and the comprehensive pollution level increased by 8.3 % after the extreme rainstorm. This study contributes to better understanding of how extreme rainstorm regulates heavy metal behavior in mangrove sediments to achieve sustainable development of mangroves under the pressures of extreme weather events.

Assessing the pollution level of a subtropical lake by using a novel hydrogen sulfide fluorescence technology

Hydrogen sulfide (H₂S) is an important environmental toxin with bi-directional biological effects on organisms. In natural waters, H₂S complexes with heavy metal ions in an anaerobic environment influence heavy metals' bioavailability and induce phosphorus release and eutrophication in water columns. Traditional detection techniques, such as colorimetric, electrochemical, and chromatographic, cannot simultaneously detect H₂S and pollution assessment of subtropical lakes. To address these technical defects, we developed small-molecule fluorescent probes to evaluate the pollution level in natural water bodies. This method relies on the combination of the probes' response signals to raw water and the water quality index, thereby enhancing the accuracy and reliability of water quality assessments. Furthermore, this novel material has a large Stokes shift. It can detect complex levels of H₂S concentrations in natural water bodies by correlating the degree of contamination and fluorescence signals. The development of this visual research tool for detecting environmental H₂S levels in natural water bodies is expected to have meaningful, practical applications.

Pollution and health risk assessment of rare earth elements in Citrus sinensis growing soil in mining area of southern China

Background

Analyzing the pollution and health risk of rare earth elements (REEs) in crop-growing soils around rare earth deposits can facilitate the improvement of REE mining-influenced area. In this study, pollution status, fraction and anomaly, plant accumulation characteristics, and potential risks of REEs (including heavy and light rare earth elements, HREEs and LREEs) in C. sinensis planting soil near ion-adsorption deposits in southern Ganzhou were analyzed. The influence of the soil environment on REEs in soil and fruit of C. sinensis was also explored.

Methods

The geo-accumulation index (Igeo) and ecological risk index(RI) were used to analyze the pollution potential and ecological risks of REEs in soils, respectively. Health risk index and translocation factor (TF) were applied to analyze the accumulation and health risks of REEs in fruit of C. sinensis. The influence of soil factors on REEs in soil and fruit of C. sinensis were determined via correlation and redundancy analysis.

Results

Comparison with background values and assessment of Igeo and RI indicated that the soil was polluted by REEs, albeit at varying degrees. Fractionation between LREEs and HREEs occurred, along with significant positive Ce anomaly and negative Eu anomaly. With TF values < 1, our results suggest that C. sinensis has a weak ability to accumulate REEs in its fruit. The concentrations of REEs in fruit differed between LREEs and HREEs, with content of HREE in fruit ordered as Jiading > Anxi > Wuyang and of LREE in fruit higher in Wuyang. Correlation and redundancy analysis indicated that K2O, Fe2O3 and TOC are important soil factors influencing REE accumulation by C. sinensis, with K2O positively related and Fe2O3 and TOC negatively related to the accumulation process.

Pollution assessment of mercury and other potentially toxic elements in the marine sediments of Mambulao Bay, Jose Panganiban, Camarines Norte, Philippines

In Jose Panganiban, Camarines Norte, small-scale gold miners dispose of untreated tailings into nearby rivers, which eventually flow into Mambulao Bay. In this study, nine (9) marine sediments were collected and analyzed to assess the pollution of potentially toxic elements (PTEs) in Mambulao Bay. Au concentrations in the sediments were also determined. The results showed that the Mambulao Bay sediments have high concentrations of Hg and other PTEs. The average concentrations of potentially toxic elements in the marine sediments were observed in the following order: Zn (638 mg/kg) > Pb (297 mg/kg) > Cr (283 mg/kg) > Cu (209 mg/kg) > Ni (146 mg/kg) > As (35 mg/kg) > Hg (4.4 mg/kg) > Cd (1.4 mg/kg). Geoaccumulation index values suggest that Mambulao Bay sediments close to the Danao River estuary are strongly to extremely polluted by Hg, strongly polluted by Pb, moderately to strongly polluted by Zn, and moderately polluted by Cd, Cu, Cr, Ni, and As. A high average Au concentration (0.42 mg/kg) was also reported in the sediments. The enrichment values suggest that the PTE pollution has an anthropogenic origin, most likely from the artisanal gold mine tailings of Jose Panganiban. Most of the marine sediments have Hg, Pb, Zn, and Cu concentrations above the probable effect levels for PTEs, which can result in occasional adverse biological effects on the aquatic biota of Mambulao Bay. The average Hg content of Mambulao Bay sediments is higher than those of Honda and Agusan Bays, while the average Pb and Zn contents are higher than those of Honda and Butuan Bays, Boac River estuary, and Tañon Strait. These results can help the government address marine pollution in Mambulao Bay for sustainable aquatic resources and coastal management and can serve as a baseline for future monitoring and assessment of the water body.

Distribution and pollution assessment of heavy metals in surface sediments along the Weihai coast, China

In this study, 78 surface sediment samples were collected from the Weihai coastal area and analyzed for heavy metals. Their concentrations and pollution status were evaluated. The distribution of heavy metals was mainly dominated by sediment grain size, and the sediments in the Weihai, Sanggou, and Rushan Bays, which have finer grain sizes, had higher concentrations. The mean geoaccumulation index values for all heavy metals were <0. Expect for Hg, the mean enrichment factor values of the other metals were <1.5, indicating that they are natural sourced. Overall, the environmental quality of the Weihai costal area was relatively good and should be maintained and protected. The heavy metals that had potential impacts on the ecological environment were Cd and Hg, which were mainly distributed west of Weihai Bay and inside Rushan Bay. They are affected by human activities and must be controlled.

Potential risk of co-occurrence of microplastics and chlorinated persistent organic pollutants to coastal wetlands: Evidence from a case study

Microplastic (MP) pollution in coastal wetlands is of a global concern. Little attention has been paid to the co-occurrence and corresponding risk of MPs with pollutants, especially refractory chlorinated persistent organic pollutants (CPOPs). A case study of Zhejiang, China was conducted to investigate the occurrence of MPs and targeted CPOPs in coastal wetlands. MPs were 100% detected, but with the lowest abundance in coastal wetlands (average: 666.1 ± 159.1 items kg^-1), as compared to other 6 terrestrial ecosystems (average: 1293.9 ± 163.7 items kg^-1) including paddy field, upland, facility vegetable field, forestland, urban soil, and grassland. A total of 35 kinds CPOPs were also detected in all studied coastal wetlands, with their concentration almost under 10 μg kg^-1 (90.1%). Both enrichment of MPs and CPOPs was affected by sediment TOC, wetland vegetation and land use simultaneously. Interestingly, the occurrence of MPs was significantly correlated with polychlorinated biphenyls (PCBs) but not organochlorine pesticides (OCPs). Results of co-occurrence pollution assessment of MPs and CPOPs further indicated only Hangzhou Bay showed the ecological risk among all tested wetlands. This would suggest a potential risk of co-occurrence of MPs and modern CPOPs in coastal wetland in economic development area. Possible reason may lie on strong MP vector effect to CPOPs. More attention should thus be paid to other wetlands polluted by MPs and MP-carrying CPOPs in area with relatively great environmental pressure induced by human activity. This study may provide reference for a better understanding with respect to the risk level posed by co-occurrence of MPs and CPOPs to global coastal wetlands.