Characterization of the Particle Size Fraction associated with Heavy Metals in Suspended Sediments of the Yellow River

Exploring the temporal toxicity signature: A baseline evaluation of the heavy metal concentration in estuarine core sediments in the coastal region of cauvery delta, bay of bengal

Globally, the concentration of heavy metals and sediment toxicity analysis are significant liabilities to aquatic environments. This scrutiny outlines the sediment textures, heavy metals and toxicity status associated with environmental pollution indices in the core sediment of the Cauvery and Vettar estuaries, East coast of India. The impact of rapid industrialization, urbanization, harbour activities and agricultural activities influences on the twain estuary is a significant concern to designate the environment. The contamination status of the sediments affects the potential biodiversity, ecological risks and human health. A total of two core sediments were recovered from the Cauvery and Vettar estuaries in March 2023 to decipher the environmental pollution status. Meticulous observation of the textural studies underscores the prevalence of sand content in Cauvery, and Vettar sediments consist of predominate clay content and minor silt contents. Furthermore, the organic matter is augmented in the Vettar River due to the higher input of waste disposal, seaweeds and algae due to the surrounding landmass. Twain core sediments argue that heavy metal concentration is decreasing in order as Fe > Zn > Ni > Pb > Cu > Cr by using portable X-ray fluorescence (pXRF) spectrometry. Remarkable results of environmental pollution indices such as Igeo, Ef, Cf, Cd and mCd state very highly polluted, extreme enrichments, high contamination and very high degree of contamination. Furthermore, the potential ecological risk indices such as PLI, SQGs, and PERI argue polluted, medium to high toxicity and moderate adverse ecological risk to the estuarine regions. Statistical analysis of the heavy metal affirms the enrichment of Fe metals may derive from lithogenic and/or anthropogenic influences, and the other studied metals such as Cu, Ni, Zn, Pb and Cr may be influenced by the anthropogenic activities in the aspect of point and non-point pollution sources. This could result from both estuaries undergoing higher pollution, in which the Vettar estuary is a considerable environmental risk zone compared to the Cauvery river due to the impact of industrial effluents and rapid urbanization activities. This finding underscores the urgent need for enhanced estuarine sediment quality study and comprehensive assessment of sediment toxicity, regulating the beneficial acumen for the government to follow the suitable remediation on the embellish policy of river and marine environments.

A Critical Review of the Crucial Role of the Yellow River's Sediment in the Interfacial Migration and Fate of Pollutants and Prospects for the Application of Environmental Sediment Restoration

Considering the increasing sediment content and increasing sediment flux of the Yellow River over the years, it is of significance to investigate the potential interfacial force mechanism between pollutants and Yellow River sediment. This article has reviewed the current research on the Yellow River sediments' mineral structures while investigating the potential interaction force between sediment and pollutants in the water environment. This article has conducted a comprehensive analysis of the influence of sediment on the migration of pollutants in the water environment. What is more, the authors have provided an outlook on the future applications of sediment in ecological environmental systems. Yellow River sediment mainly included minerals and some clay phases, while its irregular surface provided sites for the interface adsorption of pollutants. The interface force between the sediment and pollutants is mainly attributed to promoting bacterial growth on the surface of sediments, physisorption, and chemisorption forces. The sediments carry and transport pollutants during the long-distance water flow migration process. The sediment should be effectively utilized and better integrated into ecological or environmental restoration systems. This article provides a reference for studying the behavior of Yellow River sediment and the direction of future efficient utilization.

To breathe or not to breathe: Inhalational exposure to heavy metals and related health risk

This study reviewed scientific literature on inhalation exposure to heavy metals (HMs) in various indoor and outdoor environments and related carcinogenic and non-carcinogenic risk. A systematic search in Web of Science, Scopus, PubMed, Embase, and Medline databases yielded 712 results and 43 articles met the requirements of the Population, Exposure, Comparator, and Outcomes (PECO) criteria. Results revealed that HM concentrations in most households exceeded the World Health Organization (WHO) guideline values, indicating moderate pollution and dominant anthropogenic emission sources of HMs. In the analyzed schools, universities, and offices low to moderate levels of air pollution with HMs were revealed, while in commercial environments high levels of air pollution were stated. The non-carcinogenic risk due to inhalation HM exposure exceeded the acceptable level of 1 in households, cafes, hospitals, restaurants, and metros. The carcinogenic risk for As and Cr in households, for Cd, Cr, Ni, As, and Co in educational environments, for Pb, Cd, Cr, and Co in offices and commercial environments, and for Ni in metros exceeded the acceptable level of 1 × 10-4. Carcinogenic risk was revealed to be higher indoors than outdoors. This review advocates for fast and effective actions to reduce HM exposure for safer breathing.

Influence of global warming and industrialization on coral reefs: A 600-year record of elemental changes in the Eastern Red Sea

The Red Sea has been recognized as a coral reef refugia, but it is vulnerable to warming and pollution. Here we investigated the spatial and temporal trends of 15 element concentrations in 9 coral reef sediment cores (aged from the 1460s to the 1980s AD) to study the influence of global warming and industrialization on the Eastern Red Sea coral reefs. We found Na, Ca, Cr, Fe, Co, Ni, and Sr concentrations were higher in the northern Red Sea (i.e., Yanbu), whereas Mg, P, S, Mn, and Cd concentrations were higher in the southern Red Sea (i.e., Thuwal & Al Lith) reef sediments. In the central (i.e., Thuwal) to southern (i.e., Al Lith) Red Sea, the study revealed diverse temporal trends in element concentrations. However, both reef sedimentation rates (-36.4 % and -80.5 %, respectively) and elemental accumulation rates (-49.4 % for Cd to -12.2 % for Zn in Thuwal, and -86.2 % for Co to -61.4 % for Cu in Al Lith) exhibited a declining pattern over time, possibly attributed to warming-induced thermal bleaching. In the central to northern Red Sea (i.e., Yanbu), the severity of thermal bleaching is low, while the reef sedimentation rates (187 %), element concentrations (6.7 % for S to 764 % for Co; except Na, Mg, Ca, Sr, and Cd), and all elemental accumulation rates (190 % for Mg to 2697 % for Co) exponentially increased from the 1970s, probably due the rapid industrialization in Yanbu. Our study also observed increased trace metal concentrations (e.g., Cu, Zn, and Ni) in the Thuwal and Al Lith coral reefs with severe bleaching histories, consistent with previous reports that trace metals might result in decreased resistance of corals to thermal stress under warming scenarios. Our study points to the urgent need to reduce the local discharge of trace metal pollutants to protect this biodiversity hotspot.

Insight into the relationships between total suspended particles and mercury in meltwater in a typical glacierized basin in the inland Tibetan Plateau

Mercury (Hg) released by melting glaciers is likely to bind to suspended particles in meltwater runoff, posing potential risks to downstream ecosystems. The rapidly receding glaciers on the Tibetan Plateau promote the export of total suspended particles (TSP), increasing the uncertainty of Hg export released by glacier melting. To investigate the relationships between TSP and Hg, a multimedia sampling campaign was conducted in July 2020 in the Kuoqionggangri glacier region of the Lhasa River Valley No. 1 glacierized basin located in the inland Tibetan Plateau. Samples from glacier snow/ice, supraglacial rivers, subglacial rivers, proglacial lakes, and meltwater runoff were obtained, and the relationships between TSP and Hg and their transport in glacier meltwater runoff in the context of glacier retreat were explored. The average TSP concentration of different environmental samples ranged from 9.51 mg/L to 399. 27 mg/L, showing significant differences. The average total Hg (THg) concentrations ranged from 0.52 ng/L to 58.81 ng/L and decreased in the order of snow/ice >runoff> subglacial river > proglacial lake > supraglacial river. Both TSP mass concentration and number concentration have an impact on the diurnal variation in meltwater runoff Hg, and the influence of TSP number concentration is stronger than that of concentration. Sites with high TSP concentrations and quantities tended to have higher Hg concentrations, while TSP particle size had no significant effect on Hg concentration or spatial distribution. Our study further divided the glacier recharge basin into the glacier cover zone, the periglacial zone, and the downstream zone and discussed the potential impact of TSP on Hg transport in each zone. Our analysis highlights that the periglacial zone will expand and activate the resuspension process of river sediments in the warming future, which may increase the export of TSP and Hg downstream.

Changes of active particulate uranium under the Water-Sediment Regulation Scheme in the lower Yellow River: Potential impact to the uranium flux into the global ocean

With the annual Water-Sediment Regulation Scheme (WSRS) transporting large amounts of suspended particulate matter (SPM) to the sea within several days, the behavior of uranium in the Yellow River during the WSRS is crucial to better understand the uranium flux. In this study, the active forms (the exchangeable, carbonate bounded, Fe/Mn oxides bounded, organic matter bounded) and the residual form of particulate uranium were extracted by the sequential extraction method and their uranium contents were measured respectively. Results show that the content of total particulate uranium was 1.43-2.56 μg/g and the active forms accounts for 11-32 %. Particle size and redox environment are the two main factors controlling the active particulate uranium. The flux of active particulate uranium at Lijin was 4.7 tons during 2014 WSRS, which was about 50 % of the dissolved uranium flux for the same period. Thus, the terrestrial uranium flux is significantly modified by artificial regulation.

Grain size analysis and ecological risk assessment of metals in the sediments of Konsin River and Igboho dam reservoir, Oyo State, Nigeria, under agricultural disturbances

A large amount of agrochemicals and organic manures are applied on agricultural lands which is one of the major pathways of metal contamination in sediments. The present study was an attempt to appraise the grain-size of sediments and metal status of the Konsin River and Igboho dam reservoir sediments using several indexes as contamination factor (CF), degree of contamination (DC), geo-accumulation index (I_geo), enrichment factor (EF), potential ecological risk index (PERI), pollution load index (PLI), and statistical analysis. A total of seven sampling sites were chosen based on prevalent anthropogenic features and analyzed for the concentration of metals, viz., Cd, Cr, Pb, Mn, Fe, Cu, and Zn. The finding from this study showed high presence of very rough grains at the upstream and sand particles at the downstream. The average values of Cd, Cr, Pb, Mn, Fe, Cu, and Zn range from 0.00 - 2.00, 19.50 - 49.90, 20.80 - 65.30, 593.90 - 2532.90, 22,133.60 - 46,058.60, 19.60 - 66.10, and 81.60 - 191.30 mg/kg, respectively. The concentrations of metals in the sediments followed the increasing order of Cd < Cu < Cr < Pb < Zn < Mn < Fe. The observation from this study showed higher affinity of metals to less particle size. The mean concentrations of Cd, Cr, Pb, Mn, Fe, Cu, and Zn were above the toxicity reference value. The I_geo and EF indicated that most of the sites were moderately to strongly polluted due to Cd while the calculated PLI showed progressive deterioration of the environment in most sites. The Pearson's correlation analysis revealed that the presence of metals in the sediments were from anthropogenic and unidentified sources. The status of metals in the study area portends a serious ecological threat to the sediment biota and occupants of the agrarian communities that depend on the water and its produce for survival.

Health and environmental impact assessment of landfill mining activities: A case study in Norfolk, UK

The release of fine particles during mechanical landfill mining (LFM) operations is a potential environmental pollution and human health risk. Previous studies demonstrate that a significant proportion (40–80% wt) of the content of fine soil-like materials within the size range <10 mm to <4 mm recovered from such operations originate from municipal solid waste (MSW) landfills. This study evaluates the potential health risks caused by emissions from LFM activities. MSW samples recovered from the drilling of four different wells of a closed UK landfill were analysed for physical, chemical, and biological properties to determine the extent of potential contaminant emissions during LFM activities. The results show that fine particles (approximately ≤1.5 mm) accounted for more than 50% of the total mass of excavated waste and contained predominantly soil-like materials. The concentrations of Zn, Cu, Pb, Cd, As, and Cr exceed the permissible limits set by the current UK Soil Guideline Values. The highest geoaccumulation index and contamination factor values for Cu were 2.51 and 12.51, respectively, indicating a moderate to very high degree of contamination. Unsurprisingly, the pollution load index was >1, indicating the extent of pollution within the study area. The hazard quotient values indicated high exposure-related risks for Pb (16.95), Zn (3.56), Cd (1.47), and As (1.46) for allotment land use and As (1.96) for residential land use. The cancer-related risk values were higher than the acceptable range of 1.0 × 10⁻⁶ to 1.0 × 10⁻⁴. The cancer risk factor indicated that Cr and As were the major human health risk hazards.

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Potentially toxic elements and organics associated with waste fine fractions.

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Novel method for assessing potential human health risk of heavy metals achieved.

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Landfill poses major risk to human health and environment if LFM occurs.

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Pb highest contributor to the non-carcinogenic risk.

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Cr most prominent metal with respect to carcinogenic effect.

Spatial distribution of soil iron across different plant communities along a hydrological gradient in the Yellow River Estuary wetland

Iron is an important element and its biogeochemical processes are vital to the matter and energy cycles of wetland ecosystems. Hydrology greatly controls characteristics of soil property and plant community in wetlands, which can regulate the behavior of iron and its oxides. However, it remains unclear how the spatial distribution of iron and its forms in estuarine wetlands responses to hydrological conditions. Five typical plant communities along a naturally hydrological gradient in the Yellow River Estuary wetland, including Phragmites australis in freshwater marsh (FPA), Phragmites australis in salt marsh (SPA), Tamarix chinensis in salt marsh (TC), Suaeda salsa in salt marsh (SS) and Spartina alterniflora in salt marsh (SA), as sites to collect soil samples. The total iron (FeT) and three iron oxides (complexed iron, Fep; amorphous iron, Feo; free iron, Fed) in samples were determined to clarify the spatial distribution of iron and explore its impact factors. The mean contents of FeT, Fep, Feo and Fed were 28079.4, 152.0, 617.2 and 8285.3 mg⋅kg–1 of soil at 0–40 cm depth in the different sites, respectively. The means were significantly different across communities along the hydrological gradient, with the higher values for SA on the upper intertidal zone and for SPA on the lower intertidal zone, respectively. Iron and its forms were positively correlated with the total organic carbon (TOC), dissolved organic carbon (DOC), total nitrogen (TN) and clay, and negatively correlated with electrical conductivity (EC). The indexes of iron oxides (Fep/Fed, Feo/Fed and Fed/FeT) were also different across communities, with a higher value for SA, which were positively correlated with soil water content (WC) and TOC. The results indicate that a variety of plant community and soil property derived from the difference of hydrology might result in a spatial heterogeneity of iron in estuarine wetlands.

Zinc transport and partitioning of a mine-impacted watershed: An evaluation of water and sediment quality

Watershed systems influenced by mining waste products can persist for many years after operations are ceased, leading to negative impacts on the health of the surrounding environment. While geochemical behaviors of these trace metals have been studied extensively at the benchtop-scale, much fewer studies have looked at controls on their distributions at the watershed-level. In this study, trace metals (As, Cd, Cr, Cu, Ni, and Zn) were reported from water and stream bed sediments at eight sites between the years 2014-2018 along a watershed undergoing active remediation efforts. Zn was determined to be the only trace metal analyzed with concentrations above EPA and Kansas Department of Health guidelines for both water and sediment in the watershed, and thus was the primary focus for determining the health of the watershed system. Controls on trace metal pollution distribution over the watershed were investigated to determine where remediation efforts should be focused. Surface cover seemed to have the highest effectivity with pasture lands having a strong positive correlation to Zn concentrations. Initial remediation efforts were assessed by calculating the geoaccumulation index (Igeo) and the contamination factor (Cf-sediment) from sediments and contamination factor from water (Cf-water) after decades of chat pile removal efforts. Most of the sites showed significant reduction in metal concentration values compared to previous studies in the watershed for water and sediment, with four sites still reporting concentrations that reveal potential health risks. Results from this study will inform management and policy makers for areas to focus their remediation efforts on the Spring River Watershed as well as providing a framework for assessing pollution at a watershed scale.

Tracing of Heavy Metals Embedded in Indoor Dust Particles from the Industrial City of Asaluyeh, South of Iran

Assessment of indoor air quality is especially important, since people spend substantial amounts of time indoors, either at home or at work. This study analyzes concentrations of selected heavy metals in 40 indoor dust samples obtained from houses in the highly-industrialized Asaluyeh city, south Iran in spring and summer seasons (20 samples each). Furthermore, the health risk due to exposure to indoor air pollution is investigated for both children and adults, in a city with several oil refineries and petrochemical industries. The chemical analysis revealed that in both seasons the concentrations of heavy metals followed the order of Cr > Ni > Pb > As > Co > Cd. A significant difference was observed in the concentrations of potential toxic elements (PTEs) such as Cr, As and Ni, since the mean (±stdev) summer levels were at 60.2 ± 9.1 mg kg−1, 5.6 ± 2.7 mg kg−1 and 16.4 ± 1.9 mg kg−1, respectively, while the concentrations were significantly lower in spring (17.6 ± 9.7 mg kg−1, 3.0 ± 1.7 mg kg−1 and 13.5 ± 2.4 mg kg−1 for Cr, As and Ni, respectively). Although the hazard index (HI) values, which denote the possibility of non-carcinogenic risk due to exposure to household heavy metals, were generally low for both children and adults (HI < 1), the carcinogenic risks of arsenic and chromium were found to be above the safe limit of 1 × 10−4 for children through the ingestion pathway, indicating a high cancer risk due to household dust in Asaluyeh, especially in summer.

Potentially toxic elements in cascade dams-influenced river originated from Tibetan Plateau

Rivers originated from Tibetan Plateau are of great significance due to their environmental sensibility and fragility. However, the pollution of suspended particulate matter (SPM) in these rivers is rarely reported, in particular, the potentially toxic elements (PTEs) contamination. To clarify the status, sources, behavior, and risks of PTEs in SPM, a full investigation was conducted in dams-influenced Lancangjiang River basin. The findings revealed that the PTEs content (mg kg^-1) ranked Mn (766) > V (151.7) > Zn (131.0) > Cr (94.6) > Ni (44.2) > Pb (36.7) > Cu (29.4) > Co (14.6) > Sb (2.6) > Mo (1.6) > Tl (0.78) > Cd (0.48). The multi-index assessment suggested that Sb and Cd were moderately severe to severe enriched PTEs with the enrichment factor values of 10.0 and 8.8 and the geo-accumulation index values of 2.2 and 2.0, respectively, while the rest of PTEs were minor/no enrichment. In contrast, Cr and Ni were major toxic elements in SPM which contributed 25 ± 10%, 24 ± 8% to the total toxic risk index. The high partition coefficients (e.g., 6.1 for Cr) were observed in most PTEs and resulted in the 96.3% of Cr, 85.2% of Zn, 83.6% of Pb, 77.8% of Ni, and 63.2% of Cu transportation in the SPM form. Natural inputs (e.g., soil erosion) are the main source (53.6%∼61.9%) of V, Cr, Mn, Co, Ni, and Tl, while fuel burning contributed 40.9% of Zn, 32.5% of Pb, and 37.3% of Cd. Moreover, 51.2% of Sb was attributed to industrial waste source, while porphyry copper/molybdenum deposits related milltailings were the co-source of Mo (54.4%) and Cu (34.8%). Overall, the PTEs geochemistry of SPM showed the potential in tracing regional environmental change.

Catchment Soil Properties Affect Metal(loid) Enrichment in Reservoir Sediments of German Low Mountain Regions

Sediment management is a fundamental part of reservoir operation, but it is often complicated by metal(loid) enrichment in sediments. Knowledge concerning the sources of potential contaminants is therefore of important significance. To address this issue, the concentrations and the mobile fractions of metal(loid)s were determined in the sediments and the respective catchment areas of six reservoirs. The results indicate that reservoirs generally have a high potential for contaminated sediment accumulation due to preferential deposition of fine particles. The median values of the element-specific enrichment factor (EF) demonstrates slight enrichments of arsenic (EF: 3.4), chromium (EF: 2.8), and vanadium (EF: 2.9) for reservoir sediments. The enrichments of cadmium (EF: 8.2), manganese (EF: 3.9), nickel (EF: 4.8), and zinc (EF: 5.0) are significantly higher. This is enabled by a diffuse element release from the soils into the impounded streams, which is particularly favored by soil acidity. Leaching from the catchment soils partially enriches elements in stream sediments before their fine-grained portions in particular are deposited as reservoir sediment. We assume that this effect is of high relevance especially for reservoirs impounding small streams with forested catchments and weakly acid buffering parent material of soil formation.

Determination of heavy metal baseline levels and threshold values on marine sediments in the Bay of Biscay

Several international institutions have defined background or baseline levels to assess heavy metal concentrations on marine sediments in order to use these values as a reference for sediment quality indices. This criterion for marine sediment quality is applied to evaluate the potential risk of pollutants in aquatic ecosystems. However, those values were established using samples collected in large areas which present specific geochemical conditions. Then there may be a lack of accuracy in the results when using these parameters in other areas. In this context, 15 sediment cores (8 cm diameter; 2 m length) were recovered along the 400 km Asturian coastline, which is an area with representative lithological conditions for the Bay of Biscay, to determine more precise baseline levels for marine sediments from the Bay of Biscay. An evaluation of statistical and empirical methods was done to determine which method delivers the best results. Statistical methods such as mean±2SD and median±2* Median Absolut Deviation (MAD) are strongly influenced by outliers and data distributions which make these approaches less robust. Graphic techniques such as Cumulative Distribution Function (CDF) avoid the problems that asymmetrical data distributions may cause but introduce a certain level of subjectivity in the results due to the baseline values obtained depending on the researcher's experience. Finally, the Probability Curve (CP) method solves issues which may occur when using other techniques and allows one to establish baseline levels based on different percentiles. Regarding the features of the data analysed in this study, the baselines obtained via the CP method with the 95th percentile appear to be the most accurate for the Bay of Biscay. A wide variation has been found between the new baseline values and other international and national levels. Disparity between those levels and the baselines obtained in this study can be generated by granulometric and geological factors. The notable increase in Hg baseline values with respect to OSPAR Background Concentration values (BCs) (0.05 μg g^-1 and 0.6 μg g^-1 respectively) and the huge different with CEDEX levels and new threshold levels (0.35 μg g^-1 and 1.2 μg g^-1 respectively) emphasised the relevance of defining specific baselines and threshold levels, as the ones obtained in this study, not only to obtain more precise criteria for marine sediment quality to be used in environmental assessments, but also to propose new threshold levels for the evaluation of dredged material before dumping into ocean sites.

Transport and partitioning of metals in river networks of a plain area with sedimentary resuspension and implications for downstream lakes

This study showed that metal transport and partitioning are primarily controlled by suspended solids with seasonal flow regimes in plain river networks with sedimentary resuspension. Eight metal species containing iron (Fe), manganese (Mn), cadmium (Cd), chrome (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn), in multiple phases of sediments, suspended solids (>0.7 μm), colloids (1 nm-0.7 μm) and dissolved phase (<1 nm) were analysed to characterize their temporal-spatial patterns, partitioning and transport on a watershed scale. Metal concentrations were associated with suspended solids in the water column and decreased from low flow to high flow. However, metal partitioning between particulate phase (suspended solids) and dissolvable phases (colloids and dissolved phase) was reversed and increased from low flow to high flow with decreased concentration of total suspended solids and median particle size. Partition coefficients (k_p) showed differences among metal species, with higher values for Pb (354.3-649.0 L/g) and Cr (54.2-223.7 L/g) and lower values for Zn (2.5-25.2 L/g) and Cd (17.3-21.0 L/g). Metal concentrations in sediments increased by factors of 1.2-3.0 from upstream to downstream in watersheds impacted by urbanization. The behaviours of metals in rivers provide deeper insight into the ecological risks they pose for downstream lakes, where increased redox potential and organic matter may increase metal mobility due to algal blooms. Areas with heavy pollution of metals and the transport routines of metals in the river networks were also revealed in our research.

Macronutrients, trace metals and health risk assessment in agricultural soil and edible plants of Mahshahr City, Iran

In this study, we evaluate the geochemistry of macro- (Fe, P, Ca, S, K, Na, Mg) and micronutrients (Mo, Cu, Pb, Zn, Co, Mn, Cd, Sr, Cr, Hg, Se), along with possible health risks of heavy metals contamination in agricultural soils and vegetables of the Mahshahr industrial port in Iran. Calculation of geochemical coefficients revealed the low pollution load of Mahshahr agricultural soils. Most of the investigated elements exhibited lower concentrations in soil than international standards. Element concentrations in plant samples were far below the permissible values set by environmental agencies. Based on permissible values, there was deficiency of several soil elements, including Cu, in vegetables because they are mostly present in the soil residual phase. An exception was Mn, which is the most mobile element in soil. The transfer factor (TF) of elements showed the following trend: K > Na > P > S > Mo > Hg > Se > Zn > Cd > Cu > Mg > Mn > Ca > Cr > Co ≈ Fe = Pb. There was high transfer of major elements from soil to plants, and lower values for micronutrients and heavy metals. The calculated daily intake (DIM) and health risk index (HRI) for ten plant species for adults were < 1, while the HRI was larger than 1 for Mn via radish consumption. According to geochemical investigations and statistical tests such as principal component analysis, Kruskal-Wallis, and correlation coefficient calculations, plant species play the most important role in elemental uptake by plants.

Assessing the sewage discharge effects on soft-bottom macrofauna through traits-based approach

We assessed the effect of sewage-derived materials on the structural and functional attributes of the soft-bottom macrofauna at an increasing distance from the entire diffusion area. Our results showed clear spatial changes of macrofaunal density and biomass along the distance gradient from the main outfall. High values of biodiversity, species composition, and species linked to organic enrichment near the duct suggested that moderate organic stress affected this community. The traits analysis abundance-based, compared to biomass-based one, distinguished most clearly sewage contamination conditions. Functional diversity displayed spatial patterns with higher values in the less impacted sites and was significantly related to species numbers and the biotic indices (like M-AMBI). This approach is ideal for detecting macrofaunal functional changes due to sewage contamination. Thus, we infer that traits analyses could offer great potential for environmental assessment and monitoring of coastal areas influenced by human activities.

Evaluating Spatial Regression-Informed Cokriging of Metals in Soils near Abandoned Mines in Bumpus Cove, Tennessee, USA

Inorganic contaminants, including potentially toxic metals (PTMs), originating from un-reclaimed abandoned mine areas may accumulate in soils and present significant distress to environmental and public health. The ability to generate realistic spatial distribution models of such contamination is important for risk assessment and remedial planning of sites where this has occurred. This study evaluated the prediction accuracy of optimized ordinary kriging compared to spatial regression-informed cokriging for PTMs (Zn, Mn, Cu, Pb, and Cd) in soils near abandoned mines in Bumpus Cove, Tennessee, USA. Cokriging variables and neighborhood sizes were systematically selected from prior statistical analyses based on the association with PTM transport and soil physico-chemical properties (soil texture, moisture content, bulk density, pH, cation exchange capacity (CEC), and total organic carbon (TOC)). A log transform was applied to fit the frequency histograms to a normal distribution. Superior models were chosen based on six diagnostics (ME, RMS, MES, RMSS, ASE, and ASE-RMS), which produced mixed results. Cokriging models were preferred for Mn, Zn, Cu, and Cd, whereas ordinary kriging yielded better model results for Pb. This study determined that the preliminary process of developing spatial regression models, thus enabling the selection of contributing soil properties, can improve the interpolation accuracy of PTMs in abandoned mine sites.

Impacts of Sediment Particle Grain Size and Mercury Speciation on Mercury Bioavailability Potential

Particle-specific properties, including size and chemical speciation, affect the reactivity of mercury (Hg) in natural systems (e.g., dissolution or methylation). Here, terrestrial, river, and marine sediments were size-fractionated and characterized to correlate particle-specific properties of Hg-bearing solids with their bioavailability potential and measured biomethylation. Marine sediments contained ∼20-50% of the total Hg in the <0.5 μm size fraction, compared to only 0.5 and 3.0% in this size fraction for terrestrial and river sediments, respectively. X-ray absorption spectroscopy (XAS) analysis indicated that metacinnabar (β-HgS) was the main mercury species in a marine sediment, whereas organic Hg-thiol (Hg(SR)₂) was the main mercury species in a terrestrial sediment. Single-particle inductively coupled plasma time-of-flight mass spectrometry analysis of the marine sediment suggests that half of the Hg in the <0.5 μm size fraction existed as individual nanoparticles, which were β-HgS based on XAS analyses. Glutathione-extractable mercury was higher for samples containing Hg(SR)₂ species than β-HgS species and correlated well with the amount of Hg biomethylation. This particle-scale understanding of how Hg speciation and particle size affect mercury bioavailability potential helps explain the heterogeneity in Hg methylation in natural sediments.

Vertical profiles of trace elements in a sediment core from the Lambro River (northern Italy): Historical trends and pollutant transport to the Adriatic Sea

River sediments generally act as a sink for trace elements but, when resuspended, they contribute to long-term downstream transport of contamination, which may finally reach the marine environment. This study analyzed these processes in a complex aquatic system that includes a contaminated tributary, the Lambro River (Northern Italy) and its recipient and main Italian watercourse, the Po River, with the prodelta in the Adriatic Sea. The study was conducted from a historical perspective which, covering the last 50 years, examined the main driving events such as the inputs of contaminants, the construction of WWTPs and the evolution of environmental legislation. The time trend of trace element contamination was analyzed in a sediment core collected in the Lambro River and dated 1962-2011. The highest enrichments were found for Hg, Zn, Cu, Pb and Cd, which showed similar trends, with EF maxima in the '60s-'90s (172, 56, 40, 28 and 21, respectively), following industrial and urban development, and a general decreasing pattern after the late '90s. Only in the 2000s the ecological risk associated with metal contamination showed mean PEC Quotients stably below 1. The results of a literature survey on sedimentary trace elements in the Po River and the prodelta for the last 50 years were then compared to the Lambro sediment core. A significant contribution to Cu, Zn, Pb, Hg and Cd contamination was proved to derive from Lambro sediment transport. In the prodelta, increasing Ni and Cr concentrations were also evidenced, likely as a result of enhanced soil erosion in the Po basin. This study highlights the key role of WWTPs, of lower-impact industrial processes and of environmental legislation in reducing contaminant inputs. It also emphasizes the active contribution of riverine sediment-bound contamination to long-distance marine sediment quality.

Impact of anthropogenic activities on an urban river through a comprehensive analysis of water and sediments

The aim of this study was to assess the impact of urban and industrial areas on an urban river through a comprehensive analysis of water and sediments. Six different sites along the San Luis River, Argentina, were characterized by measuring 12 physical-chemical parameters and nine heavy metals according to standard protocols. Metal pollution in sediment samples was evaluated with several indices. Cluster analysis was applied to standardized experimental data in order to study spatial variability. As, Cu, Cr, Mn, Pb, and Zn were the main contributors to sediment pollution, and the industrial zone studied showed moderate enrichment of Co, Cu, and Zn, probably due to anthropogenic activities. Cluster analysis allowed the grouping of the sites: sediment samples were classified into two clusters according to the metal content; water samples were arranged into three groups according to organic matter content. The results were compared with sediment and water quality guidelines. They indicated progressive deterioration of water and sediment quality compared with the background area, mainly in the sites following the industrial park and domestic discharge areas. Moreover, the results showed that the analysis of both water and sediment should be considered to achieve a watershed contamination profile.

Concentrations, Distribution, and Pollution Assessment of Metals in River Sediments in China

This study conducted a review on the concentrations, spatial distribution and pollution assessment of metals including As, Hg, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn in 102 river sediments in China between January 2008 and July 2020 based on the online literature. The geo-accumulation index (Igeo) and potential ecological risk index (RI) were used for the pollution assessment of the metals. The results showed that the ranges of metals were: 0.44 to 250.73 mg/kg for As, 0.02 to 8.67 mg/kg for Hg, 0.06 to 40 mg/kg for Cd, 0.81 to 251.58 mg/kg for Co, 4.69 to 460 mg/kg for Cr, 2.13 to 520.42 mg/kg for Cu, 39.76 to 1884 mg/kg for Mn, 1.91 to 203.11 mg/kg for Ni, 1.44 to 1434.25 mg/kg for Pb and 12.76 to 1737.35 mg/kg for Zn, respectively. The median values of these metals were descending in the order: Mn > Zn > Cr > Cu > Pb > Ni > Co > As > Cd > Hg. Compared with the SQGs, As and Cr manifested higher exceeding sites among the metals. Metals of river sediments manifested a significant spatial variation among different regions, which might be attributed to the natural weathering and anthropogenic activity. The mean Igeo values of the metals presented the decreasing trends in the order: Cd > Hg > Zn > Cu > As > Pb > Ni > Co > Cr > Mn. Cd and Hg manifested higher proportions of contaminated sites and contributed most to the RI, which should be listed as priority control of pollutants. Southwest River Basin, Liaohe River Basin, and Huaihe River Basin manifested higher ecological risks than other basins. The study could provide a comprehensive understanding of metals pollution in river sediments in China, and a reference of the control of pollutant discharge in the river basins for the management.

Processes driving seagrass soils composition along the western Mediterranean: The case of the southeast Iberian Peninsula

Seagrasses are distributed all along the coast of the Mediterranean Sea being Posidonia oceanica and Cymodocea nodosa the most common species. They promote sedimentation, leading to the formation of well-structured soils. Over the last decade, a growing attention has been paid to their role as CO₂ sinks in the form of organic carbon (C_org) and to their use as environmental archives. However, most of the knowledge about pedogenetic processes in these soils refer to the rhizosphere. This study aims to understand seagrass soils biogeochemistry in the rhizosphere and below, which in turn can help to understand their long term formation processes. Fifteen cores were strategically sampled along a 350 km stretch of the Southeast Iberian coast, and analyzed for elemental composition (XRF core-scanning), magnetic susceptibility, C_org content and gran size distribution. The cores were dated by ²¹⁰Pb and ¹⁴C-AMS techniques to estimate soil accretion. Principal component analysis was used to explore the main geochemical processes linked to soil formation. The results showed that terrestrial runoff plays a key role in meadow soil composition. Furthermore, C_org accumulation did not follow any general depth trend in our soil records, suggesting that temporal variation in C_org inputs is an important factor in determining carbon depth distribution within the soil. We obtained evidence that the establishment of well-developed, stable C. nodosa meadows in the Mediterranean Sea may be promoted by adverse environmental conditions to P. oceanica settlement. Metal's behavior within the meadow deposit and their interaction with organic matter and carbonates is unclear. The results presented in this paper highlight the importance of the influence of land-based inputs in the characteristics of seagrass meadow deposits, highly determining their C_org content, as well as the need for further studies on metal behavior, to understand their full potential as environmental records.

Identification and uncertainty analysis of high-risk areas of heavy metals in sediments of the Yangtze River estuary, China

In this study, ordinary kriging (OK) and indicator kriging (IK) were used to analyze the uncertainty associated with high-risk areas of seven heavy metals (As, Cd, Cr, Cu, Hg, Pb, and Zn) in sediments of the Yangtze River estuary during four seasons. The OK results showed that the high-risk areas of Cd, Cr, Cu, Hg, and Pb had a high proportion, with the highest corresponding to Cr pollution (up to 60%). Predictions based on IK revealed that the proportion of high-risk areas of Cr, Cd, and Hg pollution were high, especially that of Cr was higher than 90%. However, there were uncertainties between the OK and IK results. The uncertainty results revealed that the uncertainty areas of Cr pollution were relatively large, accounting for about 30%, while those of Cd, Cu, and Hg pollution were lower than 10%.

Budget and fate of sedimentary trace metals in the Eastern China marginal seas

To achieve a better understanding of global biogeochemical cycle and budget of trace metals (TM) in the world's ocean, a comprehensive study of the level, fate and burial flux of TM in surface sediment from the Eastern China Marginal Seas (ECMS) was conducted. The results indicated that Pb, Zn, Cu, and Cr were highly concentrated in mud deposits and primarily controlled by the natural processes of sediment composition and regional hydrodynamics, whereas As had a close association with Mn and was mainly derived from anthropogenic activity. The sediment mass inventories of Pb, Zn, Cu, Cr, and As in the ECMS (~220,780 km²) were estimated to be 28,324, 92,192, 23,434, 94,560 and 11,968 t/yr, respectively. A mass budget model revealed that riverine runoff, coastal erosion input and atmospheric deposition (dry and wet) constituted 62-76%, 15-37% and 2-9% of the total Pb, Zn and Cr influxes, respectively, while more than 4,690 t of Cu annually outflowed to the open seas to balance the budget. More importantly, we found that the sum of the estimates of these contributions tended to fall short of the calculated depositional fluxes of As, implying that anthropogenic activities probably have altered the natural geochemical cycle of As. Our results suggest that the ECMS constitutes a major final repository of TM at the Asia scale; however, the burial fluxes of trace metals are expected to decrease due to enhanced environmental investments by the Chinese government and decreased suspended particulate TM loads from the Chinese major rivers.

Immobilization of Heavy Metals in Contaminated Soils—Performance Assessment in Conditions Similar to a Real Scenario

Soil “health” is becoming an increasing concern of modern societies, namely, at the European level, considering its importance to the fields of food, clean water, biodiversity, and even climate change control. On the other hand, human activities are contributing more and more to induce contamination in soils, especially in industrialized societies. This experimental work studies different additives (carbon nanotubes, clay, and Portland cement) with the aim to evaluate their effect on heavy metals, HMs (lead, cooper, nickel, and zinc) immobilization in a contaminated soil in conditions similar to a real scenario. Suspension adsorption tests (fluid-like condition) were performed aiming to supply preliminary information about the adsorption capacity of the soil towards the different HMs tested, while percolation tests (solid-like conditions) were performed aiming to evaluate the HMs immobilization by different additives in conditions similar to a real situation of soil contamination. Results showed that soil particles alone were able to retain considerable amounts of HMs (especially Pb and Cu) which is linked to their fine grain size and the soil high organic matter content. In conditions of good dispersion of the additives, addition of carbon nanotubes or clay can rise the HMs adsorption, except in the case of Zn2+ due to its low electronegativity and high mobility. Moreover, the addition of cement to the soil showed a high capacity to immobilize the HMs which is due to the chemical fixation of the HMs to binder hydration products. In this case, HMs immobilization comes associated with a soil stabilization strategy. The results allow to conclude that the additives, carbon nanotubes and clay, have the potential to minimize HMs mobility in contaminated soils and can be a valid alternative to the usual additive, Portland cement, when tested in conditions similar to a real on-site situation, if the objective is not to induce also soil stabilization, for instance, to enable its use for construction purposes. The results obtained can help designers and decision-makers in the choice of the best materials to remediate HMs contaminated soils.

Incorporating oral bioaccessibility into human health risk assessment due to potentially toxic elements in extractive waste and contaminated soils from an abandoned mine site

The waste rock, tailings and soil around an abandoned mine site in Gorno (northwest Italy) contain elevated concentrations of potentially toxic elements (PTE) exceeding the permissible limits for residential uses. Specifically, the maximum concentrations of As, Cd, Pb, and Zn were 107 mg/kg, 340 mg/kg, 1064 mg/kg, and 148 433 mg/kg, respectively. A site-specific human health risk assessment (HHRA) was conducted for residential and recreational exposure scenarios, using an approach based on Risk Based Corrective Action (RBCA) method, refined by incorporating oral bioaccessibility data. Oral bioaccessibility analyses were performed by simulating the human digestion process in vitro (Unified BARGE Method). Detailed analysis of oral bioaccessible fraction (BAF i.e. ratio of bioaccessible concentrations to total concentrations on <250 μm fraction) indicated BAF of As (5-33%), Cd (72-98%), Co (24-42%), Cr (3-11%), Cu (25-90%), Ni (17-60%), Pb (16-88%) and Zn (73-94%). The solid phase distribution and mineralogical analyses showed that the variation of BAF is attributed to presence of alkaline calcareous rocks and association of PTE with a variety of minerals. The HHRA for ingestion pathway, suggested that bioaccessibility-corrected cancer risk reached up to 2.7 × 10^-5 and 0.55 × 10^-5 for residential and recreational senarios respectively (acceptable level is 1 × 10^-5). The hazard index (HI) recalculated after incorporation of oral bioaccessible concentrations for a residential scenario ranged from 0.02 to 17.9. This was above the acceptable level (>1) for 50% of the samples, indicating potential human health risks. This study provides information for site-specific risk assessments and planning future research.

Effects of soil particle size on the adsorption, distribution, and migration behaviors of heavy metal(loid)s in soil: a review

In recent years, toxic pollution from heavy metal(loid)s in soil has become a severe environmental problem worldwide. The migration and transformation of heavy metal(loid)s in soil have become hot topics in the field of environmental research. Soil particle size plays an important role in influencing the environmental behavior of heavy metal(loid)s in soil. This review collates and synthesizes the research on the adsorption, distribution, and migration of heavy metal(loid)s in soil particles. There is no unified method for soil particle separation, since the purposes of different studies are different. Regardless of adsorption or distribution characteristics, fine soil particles generally exhibit a higher capacity to combine heavy metal(loid)s; however, certain studies have also observed a contrary phenomenon, according to which heavy metal(loid)s were more enriched in coarser particles. The adsorption and distribution of heavy metal(loid)s in soil particles were essentially determined by the physicochemical properties of the soil particles. Land use obviously affected the distribution of heavy metal(loid)s in the soil particles. Organic matter had an important influence on the distribution and availability of heavy metal(loid)s in agricultural and forest soils, while for urban soils and sediments, clay minerals or metal (hydr)oxides may play the dominant role. Preferential surface migration of fine particles during erosion processes did not always lead to the enrichment of heavy metal(loid)s in the lost soil. Further research should be conducted to explore the relationships among the soil aggregates, organic matter, heavy metal(loid)s, and soil microorganisms; the association between the distribution and availability of heavy metal(loid)s and the properties of soil particles; and the migration patterns of heavy metal(loid)s in soil particles at different scales.

Accumulation of As, Cd, Pb, and Zn in sediment, chironomids and fish from a high-mountain lake: First insights from the Carnic Alps

Though mountain lakes are generally much less influenced by human activities than other habitats, anthropogenic threats can still alter their natural condition. A major source of global environmental pollution in mountain ecosystems is trace element contamination. For this study we investigated for the first time the accumulation of As, Cd, Pb, and Zn in sediment, Diptera Chironomidae (prey), and bullhead Cottus gobio (predator) in a typical high-mountain lake (Dimon Lake) in the Carnic Alps. Significant differences in trace element levels were observed between sediment, Diptera Chironomidae, and C. gobio liver and muscle samples (Kruskal-Wallis test; p < .03 for all elements). As and Pb levels were highest in sediment, Cd and Zn levels were highest in Diptera Chironomidae, and the lowest values for all elements were measured in C. gobio muscle and liver. Bioaccumulation factor values were much higher in Diptera Chironomidae than fish muscle and liver, with the highest values recorded for Cd (5.16) and Zn (4.37). Trophic transfer factor values were very low for all elements in fish muscle and liver, suggesting a biodilution effect along the food chain. Further studies are needed to expand on these first findings that provide useful insights to inform environmental monitoring and policy in remote high-mountain lakes.

Hydrodynamic Controls of Particulate Metals Partitioning Along the Lower Selenga River—Main Tributary of The Lake Baikal

In this study, the downstream effects of pollutants spreading due to hydromorphological gradients and associated changes in sediment transport conditions along the braided-meandering and deltaic distributary reach of a large river downstream section are discussed. We demonstrate the significance of hydrodynamic control for sediment-associated metal partitioning along the river. Typically, the downward decline of the sediment and metals spreading towards Lake Baikal is observed due to buffer effects in the delta. During peak flow, the longitudinal gradients in heavy metal concentration along the distributary delta reach are neglected due to higher concentrations delivered from the upper parts of the river. In particular, significant variations of heavy metal concentrations associated with the river depth are related to sediment concentration and flow velocity profiles. Various particulate metal behavior in silt-sand delta channels and the sand–gravel Selenga main stem emphasize the importance of near-bottom exchange for particles spreading with the river flow. Using empirically derived Rouse numbers, we found quantitative relationships between the ratio of particulate metals sorting throughout depth in a single river channel and the hydrodynamic conditions of sediment transport.

Assessment of the Possible Reuse of Extractive Waste Coming from Abandoned Mine Sites: Case Study in Gorno, Italy

Supply of resources, a growing population, and environmental pollution are some of the main challenges facing the contemporary world. The rapid development of mining activities has produced huge amounts of waste. This waste, found in abandoned mine sites, provides the potential opportunity of extracting raw material. The current study, therefore, focuses on testing the validation of a shared methodology to recover extractive waste from abandoned mines, and applies this methodology to a case study in Gorno, northwest Italy. The methods focused on: (1) analyzing the impact of tailings and fine fraction of waste rock (<2 mm) on plants (Cress - Lepidium Sativum) to assess usability of both as soil additive, and (2) recovering raw materials from tailings and coarse fraction (>2 mm) of waste rock, by means of dressing methods like wet shaking table and froth flotation. The results indicated that the fine fraction of waste rock and tailings did not have detrimental effects on seed germination; however, there was marked decrease in plant growth. As for the recovery of raw materials, the coarse waste rock samples, crushed to <0.5 mm, produced a recovery of Cd, Ga, and Zn—as much as 66%, 56%, and 64%, respectively—using the wet shaking table. The same samples when crushed to 0.063–0.16 mm and used for froth flotation produced a recovery of Cd, Ga, and Zn of up to 61%, 72%, and 47%, respectively. The flotation experiment on tailings showed a recovery of Cd, Ga and Zn at pH 7 of 33%, 6% and 29% respectively. The present investigation highlights the methodologies used for extracting raw materials from extractive waste.

Mercury in sediment cores from the southern Gulf of Mexico: Preindustrial levels and temporal enrichment trends

Spatial and temporal variability of mercury concentrations in sediments was evaluated in ²¹⁰Pb-dated sediment cores from offshore and intertidal areas in the southern Gulf of Mexico. In offshore cores, mercury concentrations were comparable (11.2-69.2 ng g^-1), and intermediate between concentrations in intertidal cores from the eastern (6.0-34.4 ng g^-1) and the western (34.9-137.7 ng g^-1) inlets of Términos Lagoon. The enrichment factor (EF) indicated minimal contamination (EF < 2) in most offshore cores, whereas in some intertidal cores steadily increasing mercury enrichment and fluxes were observed along the past century. No evidence of oil industry related mercury contamination was found, as the minor but increasing enrichment in intertidal cores is most likely related to land-derived sources such as catchment eroded soils and waste water runoff. Results highlight the importance to control catchment erosion and untreated sewage releases to reduce mercury loadings to the coastal zone.

Levels and human health risk assessment of heavy metals in surface soil of public parks in Southern Ghana

This study evaluates the extent to which humans may be exposed to health risk from heavy metals in surface soils of public parks in Southern Ghana during outdoor activities. The study investigated surface soils of 56 public parks from seven metropolitan cities in Southern Ghana. Heavy metals (Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) were determined using microwave-assisted HNO₃-HF acid digestion and atomic absorption spectroscopy with flame, graphite furnace, and cold vapor options. All parks studied registered the presence of heavy metals with mean concentrations following the order: Mn > Zn > Cr > Pb > Cu > Ni > Cd > Hg. Whereas the mean concentrations of Zn (221.92 mg/kg) and Cr (107.01 mg/kg) respectively exceeded the Canadian (200 mg/kg; 64 mg/kg) and the EU (100-200 mg/kg; 50-100 mg/kg) standards, the ranges of Cu (14.27-138.85 mg/kg) and Pb (6.46-628.31 mg/kg) also exceeded their EU range of 50-100 mg/kg. The results indicated that there was no immediate risk to Ni and Hg on the public parks studied; however, Pb, Cd, Zn, Cu, and Cr may pose some adverse effects as they exceed their respective guideline limits in soil. The ranges of non-carcinogenic risk for adults and children were 0.0186-0.0787 and 0.0197-0.0850 respectively while the corresponding ranges for carcinogenic risks were 3.75 × 10^-7-1.28 × 10^-6 and 4.17 × 10^-7-1.31 × 10^-6. Even though risk assessment suggested low and acceptable health risk levels to patrons, there is the need for close monitoring since Pb, Cd, Zn, Cu, and Cr have shown tendency of accumulating beyond acceptable limit.

Spatial distribution and ecological risk assessment of trace metals in surface sediments of Lake Qaroun, Egypt

A suite of trace metals was determined in twenty surface sediments collected from Lake Qaroun, which is designated as a natural reserve in 1989 to examine their spatial distribution and their potential environmental impact on the lake. Contamination factor (C_f), enrichment factor (EF), geoaccumulation index (I_geo), and pollution load index (PLI) are applied to evaluate the quality of the lake. The highest concentrations were detected in the eastern portion of the lake near Al-Bats drain. The levels of Ba exceeded the toxicity reference value (TRV) (20 ng/g dw) set by US EPA for all sediments, while sediments collected from Al-Bats region exceeded the TRV for Zn (68 ng/g dw). Arsenic, Ba, Sn, Co, Cu, and Hg are poorly correlated with background value of Fe suggesting anthropogenic activities over the entire lake. The values of C_f and I_geo confirmed that the eastern portion of the lake has been found moderately to considerably contaminated by As, Sn, and Zn. Sediments collected from the eastern location (S1) were very highly enriched of Sn (22.47); however, the other eastern locations were highly enriched of Sn, As, Cd, Co, and Ba. It is clear that sites near Al-Bats and El-Wadi drains are hot spots, which got immense amounts of domestic, agricultural, and industrial wastes. Behind the influence of these discharges, concentrations are decreased. The PLI over the entire lake ranged from 0.247 to 0.801 for all sites, which reflect unpolluted status.

Heavy Metals in Suspended Particulate Matter of the Zhujiang River, Southwest China: Contents, Sources, and Health Risks

To investigate the abundance, water/particle interaction behavior, sources, and potential risk of heavy metals in suspended particulate matter (SPM), a total of 22 SPM samples were collected from the Zhujiang River, Southwest China, in July 2014 (wet season). Nine heavy metal(loid)s (V, Cr, Mn, Ni, Cu, Zn, As, Cd and Pb) in SPM were detected. The results show that the selected heavy metal(loid)s in SPM appear in the following order: Mn (982.4 mg kg⁻¹) > Zn (186.8 mg kg⁻¹) > V (143.6 mg kg⁻¹) > Cr (129.1 mg kg⁻¹) > As (116.8 mg kg⁻¹) > Cu (44.1 mg kg⁻¹) > Ni (39.9 mg kg⁻¹) > Pb (38.1 mg kg⁻¹) > Cd (3.8 mg kg⁻¹). Furthermore, both the enrichment factor (EF) and geo-accumulation index (I_geo) indicate that SPM is extremely enriched in metal(loid)s of Cd and As, while SPM is slightly enriched, or not enriched, in other heavy metals. According to the toxic risk index (TRI) and hazard index (HI), arsenic accounts for the majority of the SPM toxicity (TRI = 8, 48.3 ± 10.4%) and causes the primary health risk (HI > 1), and the potential risks of V and Cr are also not negligible. By applying a correlation matrix and principal component analysis (PCA), three principal components (PC) were identified and accounted for 79.19% of the total variance. PC 1 (V, Cr, Mn, Ni, Cu, and Pb) is controlled by natural origins. PC 2 (As and Cd) is mainly contributed by anthropogenic origins in the basin. PC 3 (Zn) can be attributed to mixed sources of natural and anthropogenic origins. Moreover, all the partition coefficients (lgK_d) exceeded 2.9 (arithmetical mean value order: Mn > Pb > Cd > V ≈ Cu > Cr ≈ Ni), indicating the powerful adsorptive ability of SPM for these heavy metal(loid)s during water/particle interaction.

Evaluation of floor-wise pollution status and deposition behavior of potentially toxic elements and nanoparticles in air conditioner dust during urbanistic development

The study was undertaken to investigate deposition behaviors of various size-segregated particles and indoor air quality using dust accumulated on the air conditioner filter acting as a sink for PTEs and nanoparticles that can pose a significant health risk. However, the particulate matter size and chemical composition in AC dust and its relationship with PTEs remains uncertain. Current study aims to investigate the PTEs and nanoparticles composition of AC dust using different analytical approaches including ICP-MS, XRD, XPS, SEM/TEM along with EDS and Laser Diffraction particle size analyzer. The mean concentration of PTEs like Al, As, Cd, Cu, Li, Pb, Sb, Se, Sn, Ti, V and Zn exceeded the corresponding background value. Pb, As, Sn, Sb, Cd were categorizing under geo-accumulation index class IV. Most of the particles were found to be > 100 μm and it decreased significantly with increase in floor altitude. A significantly negative correlation was found between particles size and PTEs concentration showing a significant increase in PTEs content with decrease in particles size. The XPS results showed dominant peaks for TiO₂, Ti-O-N, As₂O₃, Fe⁺³, Fe⁺², Al-OH and Al₂0₃. Additionally, As, Pb, Si and Fe were dominant metallic nanoparticles identified using SEM/TEM along with EDS.

Linking oral bioaccessibility and solid phase distribution of potentially toxic elements in extractive waste and soil from an abandoned mine site: Case study in Campello Monti, NW Italy

Oral bioaccessibility and solid phase distribution of potentially toxic elements (PTE) from extractive waste streams were investigated to assess the potential human health risk posed by abandoned mines. The solid phase distribution along with micro-X-ray fluorescence (micro-XRF) and scanning electron microscopy (SEM) analysis were also performed. The results showed that the total concentrations of PTE were higher in <250 μm size fractions of waste rock and soil samples in comparison to the <2 mm size fractions. Mean value of total concentrations of chromium(Cr), copper (Cu), and nickel (Ni) in waste rocks (size fractions <250 μm) were found to be 1299, 1570, and 4010 mg/kg respectively due to the parent material. However, only 11% of Ni in this sample was orally bioaccessible. Detailed analysis of the oral bioaccessible fraction (BAF, reported as the ratio of highest bioaccessible concentration compared with the total concentration from the 250 μm fraction) across all samples showed that Cr, Cu, and Ni varied from 1 to 6%, 14 to 47%, and 5 to 21%, respectively. The variation can be attributed to the difference in pH, organic matter content and mineralogical composition of the samples. Non-specific sequential extraction showed that the non-mobile forms of PTE were associated with the clay and Fe oxide components of the environmental matrices. The present study demonstrates how oral bioaccessibility, solid phase distribution and mineralogical analysis can provide insights into the distribution, fate and behaviour of PTE in waste streams from abandoned mine sites and inform human health risk posed by such sites .

Lead contamination in sediments in the past 20 years: A challenge for China

Lead (Pb) contamination was recognized in China early in the 1920s. However, the response of Pb contamination in sediments to China's rapid economic and social development remains uncertain to date. We conducted a literature review of over 1000 articles from 1990 to 2016 and the first national-scale survey of Pb contamination in China. A literature review showed that available research in China focused on the economically highly developed river basins, including the Pearl River Basin (PRB), Yellow River Basin (YRB), and Yangtze River Basin (YtRB), whereas those in the less developed southeastern, southwestern, and northwestern river basins received limited attention. The YtRB and YRB had higher Pb contamination levels than other basins, corresponding with the rapid economic development in those regions. However, the less economically developed river basins in the southeastern and northwestern regions of China were also contaminated by Pb. Analysis of 146 studies in the PRB, YRB, and YtRB revealed that Pb contamination in PRB sediments showed a tendency to improve over time, whereas that from the YtRB exhibited a tendency to worsen. For the YRB, there was a slight increase from 1990 to 2006 and a decreasing trend from 2007 to 2014. The overall temporal trend in Pb levels in PRB and YRB sediments corresponded with that of the Pb discharged in wastewater in the surrounding cities, indicating that industrial wastewater discharge was possibly one of the main anthropogenic sources of Pb in those sediments. For the YtRB, the increasing trend in Pb concentrations was related to the considerably high atmospheric Pb emissions in the surrounding cities and its geographical characteristics. These findings suggested that China should develop systematic and consistent approaches for monitoring Pb contents in sediments and adopt a regional economic development policy focusing on pollution prevention.

The comparison of selenium and lead accumulation between contaminated muddy and sandy sediments from four estuaries along the Persian Gulf: effect of grain size

Persian Gulf is one of the most important water sources in the economically developed south part of Iran, and metal pollution is a major concern for the Gulf. The bioavailability and distribution of selenium (Se) and lead (Pb) between muddy and sandy sediments from four estuaries along the Persian Gulf were analyzed. The geoaccumulation index and enrichment factor for metals and correlation between particles size with metals concentration were studied. The average concentration of metals in sediment was ranged 0.08-1.14 µg/g for Se and 0.32-4.37 µg/g for Pb in all estuaries, with the highest concentrations in Musa estuary. The results showed there was positive correlation between particles size of sediment with metals concentration. The highest of metal concentration was absorbed in silt (< 63 μm) sediment, followed by extremely fine sand (63-125 μm), fine sand (125-250 μm), medium sand (250-500 μm) and coarse sand (500-1000 μm), respectively. The organic matter and carbonate in the muddy sediment are higher than sandy sediment, and they had high specific storage capacity for accumulation of heavy metals. The result of Pearson correlation (r) for organic matter and metal was 0.78 for Se and 0.67 for Pb, and for carbonates and metal was 0.54 for Se and 0.61 for Pb. The values of EF in all estuaries show that the enrichment of sediment by heavy metals was by anthropogenic activities such as discharge of petrochemical and oil industrial. Geoaccumulation index indicates that the sediment in the Ahmadi and Ghanam estuaries was unpolluted to moderately polluted, while in the Arvand river is moderately to strongly polluted, and in the Musa estuary is extremely polluted.

Impact of Suspended Solids on the Use of LuminoTox to Detect Toxicity of Micropollutants

There is an increasing need for tools to monitor toxicity of contaminants of emerging concern (CECs) in wastewater. The purpose of this work was to assess interferences in the presence of total solids (TS) and total suspended solids (TSS) in the LuminoTox at concentrations typical of those found in municipal secondary effluent (SE) and to evaluate a simple sample enrichment method for increased CEC sensitivity. 4 or 10 µg/L atrazine in different TS concentrations and in corresponding filtrates (TSS removed) exhibited equivalent toxicities. Because the only difference between these two fractions is the TSS, this result demonstrates that, generally, this fraction does not induce toxicity nor interfere with the bioassay. At constant medium-low TS, the LuminoTox was able to detect the presence of 4 µg/L of atrazine but could not distinguish the change in atrazine concentration between 4 and 6 µg/L. No inhibition was observed in the presence of a mix of 14 CECs each at 0.23 µg/L. However, upon sample enrichment by lyophilization (50×), an inhibition of 81 ± 3% was observed. The enriched SE alone (not spiked with CECs) led to an inhibition of 49 ± 1%, indicating the detection of the CEC contribution to toxicity after sample preconcentration. The LuminoTox is a promising tool for monitoring SE; however, if the intent is to detect CECs, enrichment method optimization is required.

The effect of a massive wastewater discharge on nearshore ocean chemistry

An opportunity to study the effect of a massive wastewater discharge on a nearshore ocean environment arose in 2015 over a 42-day period when the City of Los Angeles diverted 9.4 billion gal of treated wastewater effluent from an outfall located 5 mi in the Pacific Ocean to a 1-mi backup in the Santa Monica Bay (SMB). SMB is a heavily used waterbody and is home to many marine organisms. To understand the impact of this diversion on human health and on SMB ecosystem, samples of the wastewater effluent, the receiving seawater, and sediments from around the backup outfall were analyzed, among others, for metals, semivolatile organic compounds (SVOC), nutrients, and total organic carbon (TOC) during the diversion project. Results show that these parameters were present at levels below local water quality guidelines (i.e., not enough to cause health or environmental concerns). In the effluent, metal levels were < 10 μg/L except Zn (23 ± 9.9 μg/L); phosphate, ammonia-nitrogen, organic-nitrogen, and TOC levels were 3.48 ± 0.37, 42.7 ± 5.3, 4.7 ± 1.4, and 19.0 ± 4.9 mg/L, respectively. In seawater and sediments around the backup outfall, metal levels were < 1.5 μg/L and < 25 mg/kg, respectively. Apart from 4,4'-DDE, SVOCs were not detected in sediments. To assess whether changes to native levels of pollutants in SMB occurred due to the diversion project, pre-diversion and post-diversion datasets were compared statistically. No significant differences were found between the two datasets (p > .05, paired t test), meaning the diversion did not change the SMB chemistry.

Size partitioning and mixing behavior of trace metals and dissolved organic matter in a South China estuary

The Jiulong River estuary, located in the southeastern China, suffered from metal pollution due to industrial effluent releases. Mixing of effluent and estuarine water may have significantly affected the size distribution of trace metals and their environmental fate. In the present study, colloidal size distribution of organic matter and selected metals were quantified using asymmetric flow field-flow fractionation (AF4) and ICP-MS. We demonstrated a dominance of dissolved metals in the 1-10kDa fraction, and metals such as Cu, Zn, Ni, Co, Pb, Cd and Mn were mostly regulated by terrestrial fulvic acid. The larger inorganic colloids played a limited role, although Fe reduction was likely to affect the size partitioning of colloidal Mn. The holding pond represented a source of trace metals and chromophoric and humic-like dissolved organic matter to the estuary. Scavenging or removal behavior became evident following the intermittent mixing, and the small sized colloidal organic complexes were responsible for binding and stabilizing trace metals. Variations in particle size distributions indicated different sources, fates and geochemical controls of the metals. Our results highlighted the impacts of both natural and anthropogenic processes on the transformation of trace metals among phases in this dynamic estuary system.