Calculation and uses of mean sediment quality guideline quotients: a critical review

Deciphering patterns in whole fish nitrogen isotopes on a continental scale

Nitrogen isotopes (δ15N) have been used as an indicator of anthropogenic nitrogen loading at local and regional scales. We examined δ15N in fish from estuaries across the continental United States. In the summer of 2015, the U.S. Environmental Protection Agency's National Coastal Condition Assessment (NCCA) collected fish in 136 coastal waterbodies throughout the United States. Whole fish were analyzed by NCCA for metals, organic contaminants, and lipids. For this study, we also analyzed these fish for isotopes of nitrogen (N). NCCA collected water quality, nutrients, chlorophyll a, and sediment chemistry at each site. We used these data, along with fish life history and watershed land use, to examine how whole fish δ15N was related to these environmental variables using random forest regression models at national and ecoregional scales. At the national scale, fish δ15N were negatively related to total N:total phosphorous (P) ratios (TN:TP) in surface water and reflected differences between the P-limited, δ15N depleted sites in the Floridian ecoregion to sites in other regions. δ15N was lower on the Atlantic relative to the Pacific coast. When considered by region, TN:TP was an important predictor of fish δ15N in 4 of 9 ecoregions, with higher δ15N observed with increasing N limitation (lower TN:TP) Fish life history was also an important predictor of fish δ15N at both the national and ecoregional scale. Whole fish δ15N was positively associated with bioaccumulative contaminants such as PCBs and mercury. Although land use was related to δ15N in fish, it was location specific. This study showed that N stable isotopes reflected ecological conditions at both regional and continental scales.

Distribution, levels, sources and risk assessment of polycyclic aromatic hydrocarbons in the bottom sediments of a Mediterranean river under multiple anthropopressures (Soummam River), Algeria

The Soummam River, a vital watercourse in Algeria is threatened by anthropogenic activities despite its protected wetland status. This study is the first to assess sediment pollution in the Soummam River, examining levels, compositions, sources of 16 PAHs and their effects on the environment and human health. Analysis employing Principal Component Analysis (PCA) and molecular diagnostic ratios pointed to petrogenic sources, likely stemming from petroleum leaks originating from aging pipeline and vehicles, as well as pyrogenic sources arising from vehicle exhaust and biomass combustion. Environmental and health risks were assessed through risk quotients (RQ), Sediments Quality Guidelines (SQG) and Total Lifetime Cancer Risk (TLCR). Ecological risk was found to range from moderate to high, with anticipated biological impacts, while cancer risk was deemed low. Toxicity assessment, measured by TEQ, revealed that the majority of monitoring stations exceeded safe levels. Consequently, urgent action by local authorities is warranted to implement ecosystem rehabilitation measures.

Turbid Waters and Clearer Standards: Refining Water Quality Criteria for Coastal Environments by Encompassing Metal Bioavailability from Suspended Particles

Suspended particulate matter (SPM) carries a major fraction of metals in turbid coastal waters, markedly influencing metal bioaccumulation and posing risks to marine life. However, its effects are often overlooked in current water quality criteria for metals, primarily due to challenges in quantifying SPM's contribution. This contribution depends on the SPM concentration, metal distribution coefficients (Kd), and the bioavailability of SPM-bound metals (assimilation efficiency, AE), which can collectively be integrated as a modifying factor (MF). Accordingly, we developed a new stable isotope method to measure metal AE by individual organisms from SPM, employing the widely distributed filter-feeding clam Ruditapes philippinarum as a representative species. Assessing SPM from 23 coastal sites in China, we found average AEs of 42% for Zn, 26% for Cd, 20% for Cu, 8% for Ni, and 6% for Pb. Moreover, using stable isotope methods, we determined metal Kd of SPM from these sites, which can be well predicted by the total organic carbon and iron content (R2 = 0.977). We calculated MFs using a Monte Carlo method. The calculated MFs are in the range 9.9-43 for Pb, 8.5-37 for Zn, 2.9-9.7 for Cu, 1.4-2.7 for Ni, and 1.1-1.6 for Cd, suggesting that dissolved-metal-based criteria values should be divided by MFs to provide adequate protection to aquatic life. This study provides foundational guidelines to refine water quality criteria in turbid waters and protect coastal ecosystems.

Distribution, sources and health risk assessment of DDT and its metabolites in agricultural soils in Zhejiang Province, China

Dichlorodiphenyltrichloroethane (DDT) is well known for its harmful effects and has been officially banned as a pesticide around the world. However, DDT pollution still exists in natural environments in China because DDT degrade very slowly. In this study, 60 soil samples were collected from Cixi, Zhejiang Province, and the levels of DDTs and its metabolites in soil and health risks were investigated. The results showed that the detection rate of DDT in soil samples were 100%, and the total DDTs residue in soil ranged from 0.007 to 1.208 mg/kg, with an average of 0. 113±0. 035 mg/kg, which exceeded the second-level Chinese soil environmental quality standard for farmland soil. The average residuals of p,p'-DDT, p,p'-DDE (dichlorodiphenyldichloroethylene), p,p'-DDD (dichlorodiphenyldichloroethane) and o,p'-DDT accounted for 34.8%, 50.9%, 8.0% and 6.3% of the total DDTs, respectively. The DDD/DDE ratios indicated a dehydrochlorination of DDT to DDE under aerobic conditions at most sampling sites. The ratios of (p,p'-DDE+p,p'-DDD)/p,p'-DDT and o,p'-DDT/p,p'-DDT indicating the DDT in the field were mainly introduced via industrial DDT and dicofol, including historical residue and fresh input. The health risk assessment showed that DDT-contaminated sites do not pose a non-carcinogenic risk to humans, and pose a very low risk of cancer to children and a low risk of cancer to adults. Overall, this study helps to understand the distribution, sources and health risks of DDT in typical soils.

Geochemical elements in suspended particulate matter of Ensenada de La Paz Lagoon, Baja California Peninsula, Mexico: Sources, distribution, mass balance and ecotoxicological risks

The present study aimed to evaluate multi-element concentrations (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr) in suspended particulate material (SPM) collected from Ensenada de La Paz (ELP) lagoon, Baja California Sur, Mexico in two different periods (September and May) to comprehend their origin, geochemical behavior, mass transfer and associated ecotoxicological risks. The 24 hr variation coefficient of volumetric SPM levels were found to be 51.7% in September and 40.5% in May, signifying the effects of oceanic waters. The calculated enrichment factor (EF) values for all the studied elements were of higher magnitude because of the high surface area and oxide nature of SPM, and in this study, Mo had the highest EF of 46.77 probably due to its origin from continental weathering. From the ecotoxicological perspective, the integrated toxic risk index revealed low toxic risk to the benthic community. However, the mean-ERM-Quotient calculated using the particulate concentrations of As, Cd, Cr, Cu, Ni, Pb indicated 9% probability of toxicity to biota. The comprehensive geochemical and ecotoxicological assessment of particulate metal concentrations in the ELP lagoon signify low to moderate contamination.

Geographical distribution of metals and metalloids along the estuary of the Oka River in the biosphere reserve of Urdaibai, Spain

Sediments sampled at the estuary of the Oka River in the biosphere reserve of Urdaibai, Spain were analyzed for trace elements. Sediments were collected at 45 points of the estuary and the concentration of 14 elements was measured. The geoaccumulation indexes (Igeo), Normalized Average Weighted Concentrations (NAWC) and mean Effect Range-Median quotients (mERMq) were calculated. The results obtained were complementary and allowed intra- and inter-estuary comparison. According to the present findings, the estuary was classified as healthy, since the anthropogenic contribution of metals and metalloids was generally small. However, shipping and fishing activities at the ports of Bermeo and Mundaka and urban and industrial wastes from Gernika were regarded as the major pollution sources. Nevertheless, only slightly contaminated and toxic sediments, especially related to Ni and Cu, were found in the towns of Gernika and Mundaka.

Potentially toxic metals in seawater, sediment and seaweeds: bioaccumulation, ecological and human health risk assessment

This study assesses the bioaccumulation, ecological, and health risks associated with potentially toxic metals (PTMs), including Pb, Hg, Cd, As, and Cr in Hare Island, Thoothukudi. The results revealed that the concentration of PTMs in sediment, seawater, and S. wightii ranged from 0.095 to 2.81 mg kg-1, 0.017 to 1.515 mg L-1, and 0.076 to 5.713 mg kg-1, respectively. The highest concentrations of PTMs were found in the S. wightii compared to seawater and sediment. The high bioaccumulation of Hg and As in S. wightii suggests that it can be used as a bioindicator for these elements in this region. The ecological risk indices, which include individual, complex, biological, and ecological pollution indices, suggest that Hare Island had moderate contamination with Hg and Cd. However, there are no human health risks associated with PTMs. This study examines the current ecological and health risks associated with PTMs and emphasizes the importance of regular monitoring.

Effect of typhoons on spatiotemporal patterns of multi-group persistent organic pollutants in sediment of Chinese southeastern coastal estuaries

Estuaries are susceptible to both anthropogenic disturbances and global climate changes. Impacts may be discriminated by pollution patterns of widely quantified persistent organic pollutants (POPs), though data are scarce for extreme climate events. This study quantified four groups of POPs, i.e., polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), and hexachlorocyclohexanes (HCHs), in sediments from seven Chinese coastal estuaries across a gradient of socioeconomic development in their watersheds with comparisons among the pre-typhoon, typhoon, and post-typhoon periods during 2016-2019. The maximal average concentrations, up to 1561 μg PAHs kg-1, 235 μg DDTs kg-1, and 38.9 μg HCHs kg-1, were quantified in the Jiulong River estuary and 7.61 μg PCBs kg-1 in the Jiao River estuary. Anthropogenic activities contributed to the distinctive spatial distributions of four groups of POPs in estuaries with non-agricultural gross domestic product (NAGDP) per capita significantly relating to sedimentary concentrations of PAHs and PCBs and agricultural gross domestic product (AGDP) per capita relating to DDTs and HCHs. Seasonality and typhoons led to less temporal variations in sedimentary POPs concentrations, whose spatial heterogeneity was remarkably reduced in the post-typhoon period rather than in the pre-typhoon and typhoon periods. The results of this study suggested that fingerprinting legacy POPs in spatial and temporal distributions contributed to identifying the effects of anthropogenic disturbances and climate changes on estuarine sediment quality.

Occurrence and patterns of metals in mangrove forests from the Oman Sea, Iran

Concentrations of selected metals were investigated in roots, stems, leaves and sediments from mangrove forests situated along the coast of the Oman Sea, Iran. Results showed that the overall average concentrations of lead, nickel, copper, and zinc in sediments were 47.90, 54.12, 42.13 and 44 μg/g dry weight (dw) and 3.81, 16.41, 29.23 and 25 μg/g dw in plant tissues, respectively. In addition, the bioconcentration factors (BCFs) of root, stem and leaf ranged from 0.5 to 1.7, 0.2 to 1.5, and 0.4 to 1.3, respectively. Pollution indices showed that all investigated sites were in the category of low to moderate pollution (pollution load index: 1.5-0.11), with a 21 % probability of biological toxicity.

Spatiotemporal patterns of multiple pesticide residues in central Argentina streams

Pollution of surface waters is a global threat, with particular concern about pesticides due to their severe negative effects on ecosystem functioning and human health. The aims of this study were to identify the spatiotemporal patterns of water and sediment quality, and the key variables related to the variation in pesticide pollution (122 compounds), in headwater streams (surrounding land uses: crop or mixed crop-livestock systems) and floodplain streams (surrounding land uses: urban development or natural wetland) of the Paraná River basin in the central area of Argentina. We found significant differences in water and sediment quality related to local land uses among headwater streams, but not among floodplain streams. These differences were more noticeable during spring than during autumn. Pesticides were widespread in all the streams, independently of the surrounding land use, reflecting the combination of local inputs and the role of floodplain hydrological connectivity in transporting pollutants from upstream sources. The most frequently detected compound was atrazine (75 %), whereas the highest concentration of an individual compound was observed for the glyphosate metabolite aminomethylphosphonic acid (AMPA, up to 4 μg L-1). The significant explanatory variables for pesticide pollution were turbidity, chromophoric dissolved organic matter (CDOM), sub-basin area, side slope of streams (positive relations), wetland cover, and precipitations (negative relations). Our results can be useful for the design of monitoring programs that capture the spatial and temporal variability of pesticide pollution.

Spatial distribution of heavy metals in the sediments of River Ganges, India: Occurrence, contamination, source identification, seasonal variations, mapping, and ecological risk evaluation

Present study analyzed the seasonal and spatial distribution patterns, sources, and ecological risks of seven heavy metals (Cr, Fe, Ni, Cu, Zn, Cd and Pb) in the sediments of River Ganges, finding that the majority of concentrations were lithologic, except for Cd, which was significantly higher than background standards. Elevated values of geochemical indices viz. Igeo, CF, RI, Cd, mCd, HQ, mHQ, and PN suggest moderate to high ecological risk in the benthic environment and its organisms due to the synergistic effect of heavy metals. The PEC-Qmetals revealed 8-10 % toxicity in the upstream and downstream sites, due to the influence of agricultural activities. Multivariate statistical techniques (PCM and PCA) indicated that Cd and Pb predominantly originated from anthropogenic sources, while other metals primarily derived from geological background. These geochemical findings may help to understand the potential risks and recommend strategies to mitigate the effects of metallic contamination in river sediments.

Improving toxicity prediction of metal-contaminated sediments by incorporating sediment properties

For the purpose of sediment quality assessment, the prediction of toxicity risk-levels for aquatic organisms based on simple environmental measurements is desirable. One commonly used approach is the comparison of total contaminant concentrations with corresponding water and sediment quality guideline values, serving as a Line of Evidence (LoE) based on chemistry-toxicity effects relationships. However, the accuracy of toxicity predictions can be improved by considering the factors that modify contaminant bioavailability. In this study we used paired chemistry-ecotoxicity data sets for sediments to evaluate the improvement in toxicity risk predictions using bioavailability-modified guidelines. The sediments were predominantly contaminated with metals, and measurements of sediment particle size, total organic carbon (TOC) and acid volatile sulfide (AVS) were used to modify hazard quotients (HQ). To further assess the predictive efficacy of the bioavailability-modified guideline models, sediments with differing contamination levels were tested for toxicity to a benthic amphipod's reproduction. To account for differences between laboratory exposure and field exposure scenarios, where the latter creates greater dilution, both static-renewal and flow-through test procedures were employed, and flow-through resulted in lower dissolved metal concentrations in the overlying waters. We also investigated how lower AVS concentration by oxidation modified the toxicity. This study reaffirmed that consideration of factors that influence contaminant bioavailability improves toxicity risk predictions, however the improvements may be modest. The sediment particle size data had the greatest influence on the modified HQ, indicating that higher percentage of fine particle size (<63 μm) contributed most to a lower predicted toxicity. The comparison of the static-renewal and flow-through test results continue to raise important questions about the relevance of static or static-renewal toxicity test results for risk assessment decisions, as both these test designs may cause unrealistically high contributions of dissolved metals in overlying waters to toxicity. Overall, this study underscores the value of incorporating outcomes from simple and routine sediment analysis (e.g., particle size, TOC, and consideration of AVS) to enhance the predictive efficacy of toxicity risk assessments in the context of sediment quality risk assessment.

Methods for a composite ecological suitability measure to inform cumulative restoration assessments in Gulf of Mexico estuaries

Ecosystem management requires a systematic, holistic approach that considers ecological and social outcomes. Effective restoration practices promote a balance of ecological and social goals by addressing ecological integrity, efficiently maximizing benefits while minimizing investment, and encompassing collaborative stakeholder engagement. Socio-ecological assessments can inform adaptive management and be utilized to prioritize restoration activities and monitor restoration effectiveness. In estuarine systems, socio-ecological assessments should evaluate the ability of habitats to support both ecologically and locally important species. The composite measure presented utilizes a combination of ecological and social measures to characterize ecological suitability for individual and multiple Gulf of Mexico estuarine species. The ecological suitability value (ES) for a given spatial unit is based on a suite of biophysical measures of the quality and extent of suitable habitat for each species, the species' trophic importance in a food web context, and the importance of each species in relation to stakeholder values and benefits. ES values for individual spatial units can be aggregated to estimate the distribution of ecological suitability at the estuarine scale. The ES values are calculated using examples for each step in the process. The information provided by ecological suitability characterizations can support restoration prioritization decisions for Gulf of Mexico estuaries and can provide a baseline measure to gauge restoration effectiveness over time to inform cumulative restoration assessments.

Spatio-temporal Sediment Quality Risk Assessment by Using Ecological and Statistical Indicators: A Review of the Upper Sakarya River, Türkiye

In this study, heavy metal accumulation levels (Cu, Zn, Cr, Pb, As) in biotic [Carassius gibelio (Bloch, 1782), Squalius pursakensis (Hankó 1925)] and abiotic (sediments) components in a significant freshwater ecosystem in Türkiye were investigated on the basis of seasonal variations using geographic information systems (GIS) and some ecotoxicological risk assessment indices [PLI (pollution load index), PERI (potential ecological risk index), Igeo (geo accumulation index), CF (contamination factor) and BRI (Biological Risk Index)]. GIS-based maps were utilized to depict the distribution of ecotoxicological risk assessment indices to provide a visual explanation by using the Inverse Distance Weighted (IDW) as an estimation method. Samples were collected seasonally from 12 stations selected on the Upper Sakarya River Basin, which is one of the longest fluvial ecosystems in Türkiye. As a result of applied indices, cadmium was found as the most hazardous heavy metal in terms of PERI and CF, nickel was found as the most hazardous heavy metal in terms of BRI and arsenic was found as the most hazardous heavy metal in terms of Igeo. As a result of applied PCI, 2 statistically significant factors explained 81.31% of the total variance. It was also determined that levels of almost all the investigated heavy metals (except Zn) in muscle tissues of fishes were under the permissible limits of Turkish legislation and the FAO.

Spatial distribution and potential ecological risk assessment of heavy metals in the sediments of fishing ports along the coasts of the Yellow Sea and Bohai Sea

More than 1,154 fishing ports are widely distributed in China's coastal areas. To date, however, few studies on the pollution and ecological risks of heavy metals in these fishing ports have been reported. In this study, the heavy metals of 148 sediment samples collected from 37 fishing ports along the coasts of the Yellow Sea and Bohai Sea were detected. The results showed that the average contents of Cu, Pb, Zn, and Cd were 53.58 ± 44.53, 27.90 ± 18.10, 143.52 ± 74.72 and 0.28 ± 0.15 mg/kg, respectively. Based on the geoaccumulation index (Igeo) and the potential ecological risk index (RI), we found that fishing ports were the most severely polluted by Cu, but Cd had the highest ecological risk, and most of fishing ports were in moderate potential ecological risk. The positive correlation between heavy metals and total organic carbon indicated that heavy metals in fishing ports were mainly affected by anthropogenic activities.

Geochemical and mineralogical characterization of Ria de Aveiro (Portugal) saltpan sediments for pelotherapy application

The present study aims to characterize sediments textural, geochemical and mineralogical composition used in a SPA for pelotherapy applications. Six samples were collected in two areas of an open-air saline SPA, a former saltpan in Ria de Aveiro (Portugal). Sampling areas are predominantly composed by recent alluvium that had been affected by chemical industrial effluents for over 50 years. Samples < 2000, 63, and 2 µm fractions were analyzed by X-ray Diffraction (XRD) and X-ray Fluorescence (XRF), for identification of mineral phases and chemical composition. SEM analysis was used for individual particles morphological characterization and chemical semi-quantification. Texture, mineral phases and chemical composition showed the influence of SPA pond beneficiation works. The two SPA areas revealed distinct mineral phases, one with higher quartz content, and the other with higher halite content, consistent with their environmental conditions. Illite constituted the most abundant mineral phase of the clay fraction. Preliminary results suggested concentrations of potential toxic elements (e.g., As, Cd) above reference values, representing a risk to the ecosystem and humans.

Effect of past century mining activities on sediment properties and toxicity to freshwater organisms in northern Sweden

The release of toxic metals from local mining activities often represents a severe environmental hazard for nearby lake ecosystems. Previous studies on the impact of mining have primarily focused on single lakes, with less emphasis on spatial and temporal recovery patterns of multiple lakes within the same catchment, but with different hydrological connection and distance to the pollutant source. This knowledge gap prevents us from assessing the real environmental risk of abandoned mines and understanding ecosystem recovery. This study explores the intensity and spatial patterns of sediment contamination and the potential for ecosystem recovery in three lakes in close vicinity of a lead (Pb) and zinc (Zn) mine in Sweden that has been inoperative for >20 years. Dated (²¹⁰Pb and ¹³⁷Cs) sediment cores from each lake were used to reconstruct temporal patterns in trace element deposition and relate those with past mining activities. Results show that all lakes were affected by mining, indicated by increasing Pb and Zn concentrations and decreasing organic matter content, at the onset of mining. However, the extent and timing of mining impact differed between lakes, which was partly ascribed to differences in the historical use of tailings and settling ponds. Assessment of toxicity levels in sediments, based on normalized Probable Effect Concentration Quotient (PEC-Q) to organic matter content, provided more consistent results with the historical mining than conventional methods, showing a decreasing impact in lakes once the operations ceased. Still, sediment Pb concentrations were > 10 times higher than pre-mining values, evidencing the urgent need for remediation actions in the study lakes. This study highlights the importance of considering spatial heterogeneity in metal deposition, sediment organic matter content, and hydrological connectivity with tailings when risk assessments are performed in mining-impacted lakes. The use of normalized PEC-Q in toxic assessments is also recommended.

Distribution, sources and risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Yellow Sea coast, China

To study the distribution, sources, ecological/health risks, and the impact of regional economic variations on polycyclic aromatic hydrocarbons (PAHs) contaminations along the coast of the Yellow Sea in China, sediments from a broad coastal coverage were collected and analyzed. The total contents of 16 priority PAHs varied between 1.4 and 1675.9 ng/g except in the site of H18 (3191.4 ng/g) adjacent to Qingdao City, with an average value of 295.7 ng/g. PAH pollution along the coast presented a distinctive geographical feature, which was closely linked to local human activities, such as Rongcheng with industrial zones and aquacultural areas, and Yancheng Wetland with developed aquaculture. The source analysis results indicated that PAHs were mainly from pyrolytic sources, with smaller contributions from petroleum spills and combustion. Risk assessment suggested that PAH pollution along the Yellow Sea coast showed negligible biological risks and health risks in most areas.

Polycyclic aromatic hydrocarbons in a Natural Heritage Estuary influenced by anthropogenic activities in the South Atlantic: Integrating multiple source apportionment approaches

Polycyclic aromatic hydrocarbons (PAHs) were analysed in the sediments of one of the most well-preserved estuaries in South Brazil, the Paranaguá Estuarine System (PES), using several source apportionment tools. The ∑PAH ranged from < DL to 125.6 ng g^-1 dw (dry weight) (average 29.9 ± 26.1 ng g^-1 dw), and the lowest levels detected were similar to those found in other protected areas of the world. In general, the PAH concentrations indicated excellent environmental quality for the entire estuary. Principal component analysis indicated that fine sediments and total organic carbon were the main factors controlling PAH concentrations in the PES. Multiple PAH sources were identified in the study area; biomass burning and fossil fuel combustion predominated but considerable amounts of petrogenic residues were also observed. We identified evidence of a contribution from an adjacent watershed resulting from the construction of interconnections between large rivers and from years of intense deforestation in the local Atlantic Forest.

Distribution, Multi-Index Assessment, and Sources of Heavy Metals in Surface Sediments of Zhelin Bay, a Typical Mariculture Area in Southern China

The occurrence, multi-index assessment, and sources of heavy metals in surface sediments of Zhelin Bay were investigated. Average heavy metal concentrations (mg/kg) were 81.89 (Cr), 770.76 (Mn), 16.81 (Co), 62.25 (Ni), 96.30 (Cu), 162.04 (Zn), and 73.40 (Pb), with the concentrations of studied seven heavy metals being significantly higher than their corresponding background values. Geo-accumulation index (I_geo) and pollution load index (PLI) were implemented to assess degree of heavy metal contamination. The I_geo and PLI indicated that Cr, Mn, Co, Zn, and Pb were slightly polluted, and Cu and Ni were moderately polluted in the region. Potential ecological risk index (RI) and mean possible effect level (PEL) quotient were conducted to assess ecological risk. The RI and mean PEL quotient demonstrated that surface sediments of Zhelin Bay were slight ecological risks and exhibited a 21% probability of toxicity. Principal component analysis (PCA) combined with the correlation analysis (CA) and hierarchical cluster analysis (HAC) revealed that the heavy metal contamination in Zhelin Bay might originate from three type sources.

The last 50 years of organic contamination of a highly anthropized tributary of the Po River (Italy)

We examined the temporal profiles of many organic micropollutants analysed in a sediment core sampled from a highly anthropized tributary of the Po River, the Lambro River. Analysed for extractable organic halogens (EOX), total petroleum hydrocarbons (C₁₀-C₄₀TPH), polycyclic aromatic hydrocarbons (PAHs), common legacy pollutants (DDTs, PCBs), halogenated flame retardants (PBDEs, DBDPE, TBBPA-bis, TCBPA, TBBPA, HBCDs), organotins (TBT, TPhT), antimicrobials (TCS, TCC), fragrances (AHTN, HHCB) and phthalates (DMP, DEP, DnBP, BBP, DEHP, DnOP), the dated sediment core revealed the historical record of 50 years of chemical contamination discharged into the Lambro and thereby the Po River. In this regard, the peak levels of PCBs and DDTs found in Lambro sediments were also identified in other sediment cores collected from the Po River prodelta in the Adriatic Sea, thus hundreds of kilometres downstream (Combi et al., 2020). The highest risk to aquatic organisms was associated with decades of high levels of C₁₀-C₄₀ TPH, PBDEs, PCBs, PAHs, DDTs, EOX, TCC, AHTN and DEHP, which in different periods of the contamination history, showed exceedances of guideline/threshold values. C₁₀-C₄₀ TPH and TCC, for example, were very high in the 1960s, whereas PCBs, DDTs, and PBDEs, peaked from the 1980s onward. The corresponding sums of PEC quotients ranged between 0.48 and 28.63, with a mean value (±SD) for the entire recording period of 10.62 ± 9.83. Environmental legislations and improved wastewater treatments were the main drivers of the recent downward trends observed for most of the chemicals investigated. Floods in turn resulted in macroscopic yet temporary improvements in the chemical quality of the tributary, conveying contaminated sediments into the Po River.

Sediment pollution: An assessment of anthropogenic and geogenic trace element contributions along the central Algerian coast

Sediment cores from the central Algerian coast were collected to investigate the distribution, sources and risk of trace metals. The local geochemical background of metals was defined from the core S collected in an uncontaminated area of the coast. The anthropogenic inputs in Algiers Bay elevated Ag, Cd, Pb and Zn concentrations as their maximum were 3.1, 3, 2.1 and 1.8 times the background values, respectively. Meanwhile, increased contents of Arsenic (up to 21.1 mg/kg) were detected in all sites. Correlations and PCA suggest that lithogenic sources controlled metal deposition, while most sediment arsenic was agriculture-derived. Organic matter acted as a sink or source for some trace metals. According to EFs, the study area showed slight to moderate enrichment with respect to Ag, As, Pb, Cd, Zn and Cu, whereas they remained uncontaminated with Cr, V, Co and Ni. This study provides a needed baseline for future environmental investigations.

Assessing the relative importance of stressors to the benthic index, M-AMBI: An example from U.S. estuaries

M-AMBI, a multivariate benthic index, has been used by European and American (U.S.) authorities to assess estuarine and coastal health and has been used in scientific studies throughout the world. It has been shown to be related to multiple pressures and stressors, but the relative importance of individual stressors within a multiple stressor context has not generally been assessed. In this study, we assembled data collected between 1999 and 2015 by the U.S. Environmental Protection Agency using consistent methods. These data included sediment and water quality measures and benthic invertebrate data which were used to calculate M-AMBI. We further assembled watersheds for all US estuaries with benthic data and calculated land use metrics. Random forest (RF) was used to identify those variables most strongly related to M-AMBI. Because RF is a compilation of multiple, nonlinear models, we then assessed which of these variables had a direct relationship with M-AMBI. The resulting variables were then assessed using RF to identify the subsets of variables that produced an effective and parsimonious model. This process was conducted at the national and ecoregional scale and the variables identified as being most important to predict M-AMBI were compared with literature reports of ecological patterns in a given area. At the national scale, better condition was correlated with clearer waters, lower amounts of agriculture in the watershed, and lower carbon and metal concentrations in estuarine sediments. Other stressors were identified as being important at the ecoregional scale, although sediment metal concentrations and watershed agriculture were identified as being important in most ecoregions. Our results suggest that this technique is useful to identify the most important variables impacting M-AMBI at broad spatial scales, even when the percentage of sites in Bad or Poor condition is low. This technique also provides an initial identification of important stressors that can be used to target more intensive local studies.

Potentially Toxic Elements in Water, Sediments and Fish from the Karstic River (Raša River, Croatia) Located in the Former Coal-Mining Area

The assessment of the environmental quality of a sensitive karst aquatic system under the centuries-long anthropogenic influence of the coal mining industry is important for both improving the quality of water resources and protecting aquatic wildlife and human health. In this study, we investigated the anthropogenic impact on the aquatic environment of the upper and middle course of the Raša River through the analysis of a suite of metal(loid)s in three aquatic compartments (water, sediment, fish) using inductively coupled plasma mass spectrometry (ICP-MS). Concentrations of inorganic constituents in water were low, while the chemical composition of stream sediments mainly reflected the geological background of the area, indicating the origin of metal(loid)s from predominantly natural sources. Although comparison with PEC-Q values indicated that existing sediment quality conditions could pose a threat to benthic organisms with regard to Cr and Ni, the constant vertical profiles of these elements suggested their natural origin from the weathering of flysch. Element levels in the muscle of targeted fish species were in accordance with the values typical for low-contaminated freshwater systems, while levels of Cd, Pb and Hg were mostly below the European regulatory limits for toxic elements in foods, indicating that the low concentrations of most contaminants in muscles of fish from the Raša River do not present a risk to humans or other consumers. The obtained data indicated a generally low contamination status of the western part of the Raša River basin with regard to the analyzed inorganic elements.

Early diagenetic behavior of trace metals along with estimation of their diffusive fluxes: Ecological risk assessment in pore water and sediment of Bizerte Lagoon, Tunisia

Bizerte Lagoon is a vital Mediterranean ecosystem subjected to intense anthropogenic pressure. The potential ecological risk caused by certain metals (Zn, Cu, Cr, Cd, Ni, Pb and Mn) is assessed from the data carried out in the sediment and pore water at two sites along with identifying the effects of diagenetic processes on the vertical distribution of these metals and their resulting diffusive fluxes. Using various ecological indices our results reveal a high ecological risk to benthic organisms from metals chiefly Cd, Pb and Ni accumulated in the sediment at both sites. Metals derived from organic matter degradation (Cu and Cd) and/or reduction of Mn-Fe-oxyhydroxydes (Pb, Ni, Zn, Cr) due to early diagenetic processes in sediment. The resulting concentration gradients between pore water and overlying water induce diffusive fluxes of metals to the water column. The estimation of the potential ecological risk caused by dissolved metals in pore waters by application of the Interstitial Water Criteria Toxic Units index indicates a slight ecological risk by Cu that was not identified in sediment. The ecological risk posed by dissolved metals is evidenced from -6 cm depth, which reduces the possibility of contamination of benthic species living above the water-sediment interface by diffusive fluxes of these metals.

Deriving freshwater sediment quality guidelines of polycyclic aromatic hydrocarbons using method of species sensitivity distribution and application for risk assessment

Contamination of polycyclic aromatic hydrocarbons (PAHs) in sediment has long been of great concern because of their toxic effects to benthic organisms. Sediment quality guidelines (SQGs) are the basis to evaluate the potential ecological risks of PAHs in sediments. Species sensitivity distribution (SSD) has been widely applied in deriving water quality criteria, but seldom employed in SQGs. In this study, SSD was used to derive the freshwater SQGs for four representative PAHs (naphthalene, phenanthrene, pyrene and benzo[a]pyrene) based on the sediment toxicity results. A linear relationship between the SQGs and octanol-water partition coefficient (log K_OW) was developed, and applied to predict the SQGs of other twelve PAHs. The obtained SQGs were in the range of 0.46 - 1.79 mg/kg with a geometric mean of 0.97 mg/kg, which was proposed as the SQGs for total PAHs. Based on these SQGs, the risk quotients of PAHs in the sediments collected from Haihe River of China were calculated, and the toxic effects were also tested using three representative benthic organisms. As the risk quotients of the PAHs and heavy metals in the sediments were summed up, good correlations were found (p = 0.074 and 0.018) between them and the observed toxicities of the sediments. The SQGs developed for PAHs was promising in ecological risk assessment for contaminated freshwater sediments.

Risks Assessment of Potentially Toxic Elements’ Contamination in the Egyptian Red Sea Surficial Sediments

The potential impact of tourism, industrial, and urban activities on Egypt’s Red Sea coastline, which is well-known for its economic and environmental importance, was investigated at fifteen coastal sites. In the present study, the concentration of cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) in marine sediments from these sites, was determined using Inductively Coupled Plasma Mass Spectrometers (ICP-MS). In detail, various pollution indices, statistical analyses, and spatial distribution patterns were used to assess the pollution status, impacts of human activities, ecological risks, and sources of potentially toxic elements (PTEs) in surface marine sediment. A detailed comparison with up-to-date data was conducted. These sediments were composed predominantly of fine and very fine sands. Mean grain size distribution typically depends on the source of the sediment from the following two prime sources: terrigenous (autochthonous) and biogenic (allochthonous). The detected PTE mean concentrations were as follows: Fe > Mn > Zn > Cr > Ni > Pb > Co > Cu > Cd. Multivariate statistical analysis results revealed their close distribution and association. Cd and Pb levels in the studied area have been slightly impacted by anthropogenic inputs. According to the calculated pollution indices, although a minimal or moderate contamination degree was detected in the study area, it was determined that there was a low to moderate ecological risk. The slightly high degree of contamination and risk centered in the middle of the study area around phosphate mining and related activities. More attention should be given to the concentrations and sources of Cd, Ni, and Pb as the main pollution factors.

The geochemical and environmental characteristics of trace metals in surface sediments of the river estuarine mouths around the Taiwan Island and the Taiwan Strait

The trace metals species in surface sediments of the Taiwanese river estuarine mouths and the Taiwan Strait were examined by sequential extraction method. Based on the metal species present in sediments, trace metals can be divided into three groups: (1) Co, Cr, Fe, Ni and Zn; (2) Cu and Hg; and (3) Mn and Pb. The total concentrations of trace metals in the first two groups are dominated by the residual fraction. While, Cu and Hg their organic species also contributes a significant percentage and reduces the residual fraction portion. Lead and Mn are dominated by the labile fraction. The total metal concentrations in the analyzed sediments seem to be influenced by Fe oxides, TOC and grain size. The metals contamination status assessed by three environmental indices suggests that the analyzed sediments are minor contaminated by trace metals, with a few exceptions of Cu and Hg at some stations.

Accumulation potential of heavy metals at different growth stages of Pacific white leg shrimp, Penaeus vannamei farmed along the Southeast coast of Peninsular India: A report on ecotoxicology and human health risk assessment

This study compared the heavy metal concentration in water, sediment, and shrimp at different growth stages of culture and subsequently evaluated the ecotoxicological and human health risk status. Total trace element concentration in the water, sediment and shrimp ranged from not detected (ND) (Hg) to 91.05 (Fe) μg/L, 0.01 (Hg) to 19, 246.33 (Fe) mg/kg, and ND (Hg) to 13.98 (Fe) mg/kg, respectively. Toxic metals such as, Cd, Hg, and Pb in shrimps ranged from ND to 2.11 mg/kg, ND to 0.158 mg/kg, ND to 0.088 mg/kg, and ND to 0.469 mg/kg, respectively. Toxic heavy metals at all the growth stages of shrimps (days of culture (DOC)-01 to DOC-90) were found below the maximum residual limit (MRL) of 0.5 mg/kg set by the European Commission (EC). Similarly, Cu, Zn, and As concentrations in shrimp were also far below the MRLs of 30 mg/kg, 100 mg/kg, and 76 mg/kg set by the World Health Organization and Food Safety and Standard Authority of India, respectively. The concentration of heavy metals increased from DOC-01 to DOC-90 and was positively correlated with the length and weight of the shrimps (p < 0.05). The risk assessment was estimated for both Indians and Americans and found no carcinogenic (lifetime cancer risk (LCR) < 10^-4) and non-carcinogenic (THQ and TTHQ<1) health risks through consumption of shrimp cultured in this region. The hazard quotient (HQ_dermal < 1), hazard index (HI < 1), and LCR (<10^-4) values of the heavy metals indicated that the dermal absorption might not be a concern for the local fishermen and marine fish/shrimp farmworkers. Water and sediment quality indices were applied to assess the surface water and sediment quality, and their results were found nil to low levels of heavy metal contamination at all the sampling sites. All heavy metals studied in sediments were < effect range low (ERL) and < threshold effect level (TEL), indicating no adverse biological effects on aquatic organisms. Therefore, regular monitoring of the shrimp aquaculture system throughout the crop will provide evidence of heavy metals bioaccumulation in shrimps. This research will provide baseline data to help farmers establish the optimal aquaculture practices and regulatory authorities to formulate legislation and strategies to reduce heavy metal biomagnification in shrimps from farm to fork.

Multivariate tools to investigate the spatial contaminant distribution in a highly anthropized area (Gulf of Naples, Italy)

The Gulf of Naples located in a high anthropized coastal area is subjected to an infrastructural intervention for the installation of a submarine power pipeline. In order to evaluate the distribution of contaminants in the seafloor sediments, a preliminary study has been conducted in the area using multivariate techniques. The statistic approach was performed to gain insights on the occurrence of organic and inorganic contaminants within the area, aiming to identify the relevant hot spots. Three geographical sub-areas influenced by different contaminant association were recognized: Torre Annunziata (TA), Capri (CA), and middle offshore (MO). TA and CA resulted marked by a severe contamination pattern due to anthropogenic pressures. In addition, the influence of the depositional basin in governing the contamination trend has been pointed out. The supervised technique PLS_DA resulted to be a powerful tool in addressing the complexity of the huge dataset acquired during the marine survey, highlighting the main trends in the variability of quality indicators, orienting thus the deeper investigations during follow-up monitoring activities.

Heavy Metals in River Sediments: Contamination, Toxicity, and Source Identification-A Case Study from Poland

This study investigated the spatial distribution, contamination, potential ecological risks and quantities of pollutant sources of six heavy metals (HMs) in sediments of 47 rivers. The catchments of the investigated rivers are situated in Poland, but some of them are located in Slovakia, the Czech Republic, and Germany. Cluster analysis was applied to analyze the spatial distribution of Cd, Cr, Cu, Ni, Pb, and Zn in river sediments. Moran I and Getis-Ord Gi* statistics were calculated to reveal the distribution pattern and hotspot values. Principal component analysis (PCA) and positive matrix factorization (PMF) were used to identify pollution sources. Furthermore, geochemical indices and sediment quality guidelines allowed us to assess sediment contamination and potential toxic effects on aquatic biota. The results showed that in 1/3rd of the rivers, the HM pattern and concentrations indicate sediment contamination. The EF, PLI, and MPI indices indicate that concentrations were at a rather low level in 2/3rd of the analyzed rivers. Only in individual rivers may the HMs have toxic effects on aquatic biota. Spatial autocorrelation analysis using the Moran I statistic revealed a random and dispersed pattern of HMs in river sediments. PCA analysis identified two sources of HMs' delivery to the aquatic environment. Cr, Cu, Ni, Pb, and Zn originate from point and non-point sources, while Cd concentrations have a dominant natural origin. The PMF identified three sources of pollution. Among them, urban pollution sources are responsible for Cu delivery, agricultural pollution for Zn, and industrial pollution for Ni and Cr. Moreover, the analysis showed no relationship between catchment land-use patterns and HM content in river sediments.

Physico-Chemical and Ecotoxicological Evaluation of Marine Sediments Contamination: A Case Study of Rovinj Coastal Area, NE Adriatic Sea, Croatia

Comprehensive spatial and temporal data on sediment quality in the Adriatic Sea are lacking. Therefore, prior to planned anthropogenic interventions in the local marine environment, such as deepening of the Rovinj harbour, the results of physicochemical and ecotoxicological analyses of five local coastal sediments were compared with regional averages and SQGs of neighbouring countries. Analyses of sediment grain size, content of metals and heavy metals, PAHs and PCBs were performed according to standard protocols. Sediment quality was classified according to French legislation (N1 and N2 level) and sediment guidelines. The phytotoxicity of the eluates was studied by flax seed germination tests. The logistic regression models P_max and P_avg were used to estimate the probability of toxic effects. Except for the open sea (S5), all other sediments had concentrations slightly higher than the N1 for some metals (Cu, Ni, Hg, Cr) or ΣPAHs, while the Rovinj harbour (S1) reached the N2 value for mercury. The phytotoxicity assay with sediment eluates showed inhibition of germination, root length and root biomass production, with an average phytotoxicity index (PI) ranging from 6.06% to 42.00%. Significant correlations of P_avg and P_max values with phytotoxicity and other specific parameters were found. In general, according to the applied SQGs, there are no potential ecological impacts on the marine environment at any of the investigated sites, with the exception of site S1.

Metal enrichment in sediments and bioaccumulation in edible bivalve Saccostrea cucullata from mudflats of a tropical estuary, India: a study to investigate toxicity and consumption suitability

Mudflat sediment cores from lower (C-1), middle (C-2), and lower regions of upper (C-3) Chapora Estuary were investigated for grain size composition, total organic carbon, total and bioavailable Fe, Mn, Cu, Co, Ni, and Zn to assess metal contamination. Accumulation of metals by Saccostrea cucullata was studied to understand metal toxicity. In core C-1, Fe, Mn, Cu, Co, Ni, and Zn showed an average concentration of 1.73%, 648 ppm, 12 ppm, 12 ppm, 16 ppm, and 25 ppm, respectively, while core C-2 revealed their average concentration as 1.34%, 709 ppm, 10 ppm, 11 ppm, 13 ppm, and 28 ppm respectively. In core C-3, an average concentration of Fe, Mn, Cu, Co, Ni, and Zn was 1.72%, 907 ppm, 14 ppm, 13 ppm, 18 ppm, and 31 ppm respectively. Metals in sediments varied within the estuary due to hydrodynamics, discrepancies in metal sources and sand mining-induced remobilization of metals. Correlation and principal component analysis revealed Fe oxides as the key regulator of trace metal distribution in sediments along with clay and total organic carbon. Enrichment factor (EF) and geo-accumulation index (I_geo) showed more or less moderate contamination of Mn in core C-3. Also, the potential contamination index (PCI) indicated moderate contamination of Mn in core C-3 using the shale value as background concentration, whereas the application of upper crustal value revealed moderate contamination of Fe, Mn, Cu, Co, and Ni in core C-1, Mn, Co, and Ni in core C-2 and of Cu, Co, and Ni in core C-3. Mn was severely to very severely contaminated in core C-3. The mean probable effect level quotient and mean effect range median quotient showed medium to low-level contamination of Cu, Ni, and Zn. Metals were considerably allied to Fe-Mn oxide and organic/sulphide fractions which revealed their bioavailability. Mn was 36% in labile form (lower estuary) and indicated a high risk to biota. Mn, Ni, and Zn in Saccostrea cucullata exceeded the permissible limit and suggested toxicity and non-suitability for human consumption.

Geo-Environmental Characterisation of High Contaminated Coastal Sites: The Analysis of Past Experiences in Taranto (Southern Italy) as a Key for Defining Operational Guidelines

Despite its remarkable geomorphological, ecological, and touristic value, the coastal sector of the Apulia region (Southern Italy) hosts three of the main contaminated Italian sites (Sites of National Interest, or SINs), for which urgent environmental remediation and reclamation actions are required. These sites are affected by intense coastal modification and diffuse environmental pollution due to the strong industrialisation and urbanisation processes that have been taking place since the second half of the XIX century. The Apulian coastal SINs, established by the National Law 426/1998 and delimited by the Ministerial Decree of 10 January 2000, include large coastal sectors and marine areas, which have been deeply investigated by the National Institution for the Environmental Research and Protection (ISPRA) and the Regional Agency for the Prevention and Protection of the Environment (ARPA) with the aim of obtaining a deep environmental characterisation of the marine matrices (sediments, water, and biota). More recently, high-resolution and multidisciplinary investigations focused on the geo-environmental characterisation of the coastal basins in the SIN Taranto site have been funded by the “Special Commissioner for the urgent measures of reclamation, environmental improvements, and redevelopment of Taranto”. In this review, we propose an overview of the investigations carried out in the Apulian SINs for the environmental characterisation of the marine matrices, with special reference to the sea bottom and sediments. Based on the experience gained in the previous characterisation activities, further research is aimed at defying a specific protocol of analysis for supporting the identification of priority actions for an effective and efficient geo-morphodynamic and environmental characterisation of the contaminated coastal areas, with special reference to geomorphological, sedimentological, and geo-dynamic features for which innovative and high-resolution investigations are required.

Are the tourist beaches safe for swimming? A case study of health risks of polycyclic aromatic hydrocarbons (PAHs) in tourist beaches of Bushehr City

The aims of the present research were to evaluate the health risk of long-term exposure to polycyclic aromatic hydrocarbons (PAHs) concerning the human, ecotoxicological risk for marine biota, and identify their possible sources. Surface sediment bioassay samples were collected from 15 stations of tourist beaches surrounding Bushehr City and analyzed using high performance liquid chromatography (HPLC). The results indicated the concentrations of ∑PAH ranged from 193.5 to 725.5 ng g^-1 with mean value of 351.1 ± 155.2 ng g^-1, which could be considered as moderate level of pollution. Measured levels of PAH in sediments were compared with sediment quality guidelines (SQGs), indicating low to medium ecotoxicological risk on marine organisms. Moreover, mean ERM quotient (M-ERM-Q) and mean PEL quotient (M-PEL-Q) were implemented, demonstrating potentially biological adverse effects. A preliminary evaluation of human health risk using incremental lifetime cancer risk (ILCR) and toxic equivalent quotient (TEQ^carc) indicated that PAH-contaminated sediment in some stations of touristic beaches of Bushehr City would induce potential carcinogenic effects especially for children. Composition and diagnostic analysis indicated that PAHs originated from both pyrogenic and petrogenic, with higher portion of incomplete combustion PAHs.

Impacts of Fishing Vessels on the Heavy Metal Contamination in Sediments: A Case Study of Qianzhen Fishing Port in Southern Taiwan

Routine maintenance of fishing vessels and wastewater discharges are primary sources of heavy metals in fishing ports. Sediment pollution assessment is necessary in fishing port management, including sediment dredging and disposal, sewage treatment facility construction, and pollution source control. In this study, sediment heavy metal contents in Qianzhen Fishing Port, the largest pelagic fishery port in Taiwan, were investigated to assess the contamination levels and related potential ecological risks using multiple sediment pollution indices. Normalization methods were applied to identify the potential sources of heavy metals in fishing port sediments. Results showed that Cu, Zn, Pb, and Cr contents in the sediments of the inner fishing port (averages of 276, 742, 113, and 221 mg/kg, respectively) were 3–5 times greater compared to those along the port entrance and outside, indicating the strong impacts of anthropogenic pollution (EFCu: 5.6–12.5; EFZn: 2.8–4.3; EFPb: 2.4–5.4; EFCr: 1.1–3.2). Copper pollution was more severe, with high maxima contamination factor (CFCu: 15.1–24.8), probably contributed by copper-based antifouling paints used in fishing vessels. The sediments in the inner fishing port are categorized as having considerable ecological risk and toxicity (mERMq: 0.61–0.91; ΣTU: 7.5–11.7) that can potentially cause adverse effects on benthic organisms. Qianzhen Fishing Port sediments can be characterized as high Cu/Fe and Pb/Fe, moderate Zn/Fe, and high total grease content, indicating that the potential sources of heavy metals are primarily antifouling paints and oil spills from the fishing vessels. This study provides valuable data for pollution control, remediation, and environmental management of fishing ports.

Potentially Toxic Elements and Pb Isotopes in Mine-Draining Meža River Catchment (NE Slovenia)

In the present study it was observed that Pb, Zn, Cd and As are still present at elevated concentrations in the environment of the upper Meža Valley. In particular, the concentrations of Pb indicate possible new sources have emerged. The main objective of this study was to determine the Pb isotope composition in both the water and the sediments (fractions < 0.150 and <0.063 mm) from the Meža River and its tributaries for the first time and then use them as identifiers of Pb pollution sources. In addition, by calculating the PEC-Q values, the potential hazard of the present concentrations of Pb, Zn, Cd and As to the river environment was evaluated. The results showed elevated Pb and Zn concentrations in the water and sediments at the majority of sampling sites. In general, higher concentrations of Pb, Cd and As were determined in the <0.063 mm fraction, while Zn was higher in the <0.150 mm fraction. The isotope composition of Pb in both fractions differed slightly, indicating an additional Pb source.

Legacy organochlorines in estuarine sediment in relation to socioeconomic pattern in multi-coastal watersheds

Estuarine sediment quality is highly associated with anthropogenic activities in watersheds. This study attempts to couple socioeconomic patterns with estuarine sediment quality via legacy organochlorines in 14 Chinese coastal watersheds. Sedimentary concentrations of HCHs, DDTs, and PCBs showed a significant spatiality in estuary, up to 48.7 ± 15.1, 89.0 ± 46.4, and 54.5 ± 17.2 ng g-1, which were predominated by β-HCH, p,p'-DTs, and tri- to penta-PCBs, respectively. Ecological risk of organochlorines was negligible except few moderate risks for DDTs and PCBs against the first class quality of the marine sediment quality guidelines of China. Sedimentary DDT and PCB concentrations were significantly delineated by an environmental Kuznets curve model as a function of non-agricultural GDP per capita in watersheds, while HCHs by an increasing linear model. Findings of this study provide a tool to quantify the contribution of anthropogenic development in watershed to environmental change in estuary across the world.

Sediment spiking and equilibration procedures to achieve partitioning of uranium similar to contamination in tropical wetlands near a mine site

The derivation of sediment quality guideline values (SQGVs) presents significant challenges. Arguably the most important challenge is to conduct toxicity tests using contaminated sediments with physico-chemistry that represents real-world scenarios. We used a novel metal spiking method for an experiment that ultimately aims to derive a uranium SQGV. Two pilot studies were conducted to inform the final spiking design, i.e. percolating a uranyl sulfate solution through natural wetland sediments. An initial pilot study that used extended mixing equilibration phases produced hardened sediments not representative of natural sediments. A subsequent percolation method produced sediment with similar texture to natural sediment and was used as the method for spiking the sediments. The range of total recoverable uranium (TR-U) concentrations achieved was 8-3200 mg/kg. This reflected the concentrations found in natural wetlands and water management ponds found on a uranium mine site and was above natural levels. Dilute-acid extractable uranium (AE-U) concentrations were >80% of total concentrations, indicating that much of the uranium in the spiked sediment was labile and potentially bioavailable. The portion of TR-U extractable as AE-U was similar at the start and end of the 4.5-month field-deployment. Porewater uranium (PW-U) analyses indicated that partition coefficients (Kd) were 2000-20,000 L/kg, and PW-U was greater in post- than pre-field-deployed samples when TR-U was ≤1500 mg/kg, indicating the binding became weaker during the field-deployment period. At higher spiked-U concentrations, the PW-U was lower post-field-deployment. Comparing the physico-chemical data of the spiked sediments with environmental monitoring data from sediments in the vicinity of a uranium mining operation indicated that they were representative of sediments contaminated by mining and that the U-spiked sediments had a clear U concentration gradient. This confirmed the suitability of the spiking procedure for preparing sediments that were suitable for deriving a SQGV for uranium.

Trace metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls in the surface sediments from Sanya River, China: Distribution, sources and ecological risk

The urban inland river ecosystems are now facing comprehensive pollution and governance pressures. Up to now, few works related to the multiple pollution assessment of trace metals, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) for the urban inland river sediments have been reported in China. Our study investigated the spatial distribution, ecological risk and potential sources of trace metals, PAHs and PCBs in surface sediment collected from 20 sampling sites of Sanya River, Hainan Province, China. The pollution status and potential ecological risk of trace metals were evaluated using the contamination indexes including geoaccumulation index (I_geo), individual potential ecological risk (E_rⁱ), potential ecological risk index (RI) and pollution load index (PLI). Considering the carcinogenicity and toxicity of PAHs and PCBs to human health and the ecological environment, we also analyzed the distributions, sources and adverse biological effects of PAHs and PCBs according to the sediment quality guidelines (SQGs), principal component analysis (PCA) and other source analysis. This study revealed that the surface sediments in Sanya River were extremely slight pollution and showed a very low ecological risk according to I_geo, E_rⁱ, PLI and RI results for trace metals. Besides, PAHs and PCBs pollution detected may not pose considerable adverse biological effect to ecological environment in a foreseeable period on the basis of comprehensive research results. The overall surface sediments quality of the Sanya River not seem to pose a serious pollution and ecological risk based on the evaluation results of multiple pollution factors. The study provided detailed information on the multiple pollution status and location of surface sediments, one of the key environmental indicators of international tourism cities, in the Sanya River, which would be useful for the water quality improvement of Sanya River and the environmental remediation of the other coastal ecosystems from different regions.

Environmental quality assessment in a marine coastal area impacted by mining tailing using a geochemical multi-index and physical approach

Mining has been described as an important source of contaminants to the coastal zone worldwide, which is greatly intensified in the case of tailing dam ruptures. This study assessed the environmental quality of the marine coastal area impacted by a mining disaster (Fundão Mine dam collapse on 05 November 2015, Southeast Brazil) by applying a geochemical multi-index and physical approach over 18 months (from October 2018 to March 2020). Nutrients, metal(oid)s and Polycyclic Aromatic Hydrocarbons (PAHs) were integrated by quality indexes: Canadian Council of Ministers of the Environment Water Quality Index (CWQI) and the Pollution Load Index (PLI) for water quality; Sediment Quality Guideline Quotients (SQG-q metal(oid)s and SQG-q PAHs) for sediment quality. Three scenarios regarding river discharge and wave-heights (Hs) were considered: 2018/2019-wet, 2019-dry, 2019/2020-wet. An Environmental Risk Assessment framework was built to describe the overall environmental quality in regards to water and sediment quality indexes as well as physical conditions. Here we show that the worsening of environmental quality is highly associated with the decrease of water quality by metal(oid)s (total forms of As and Ni; dissolved forms of Co and Fe) during the 2019-dry scenario when river discharge was at the lowest and the highest Hs occurred. Resuspension of fine sediment and suspended Fe(III) oxy-hydroxide nanoparticles by waves seem to be the main processes for releasing metal(oid)s into the water column. CWQI and PLI showed marginal and polluted conditions for water quality, respectively, and SQG-q for metals and PAHs indicated moderate impact in the sediment during the 2019-dry period. Toxicity to pelagic and benthic fauna is expected to occur in those conditions. Recovery of environmental quality occurred during the 2019/2020-wet scenario, which could be explained by alongshore and offshore transport of sediment and the dilution of aqueous metal(oid)s by intense river discharge on the continental shelf.

Low levels of persistent organic pollutants in sediments of the Doce River mouth, South Atlantic, before the Fundão dam failure

The Doce River mouth (DRM) was severely impacted by the rupture of the Fundão Dam in 2015, considered the greatest Brazilian environmental tragedy in terms of tailings volume released (>40 million m³) and traveled distance (~600 km until the Atlantic Ocean). Environmental monitoring has been performed since then, but background levels are scarce or absent to Persistent Organic Pollutants (POPs), making impact assessments difficult. In the current study, we presented the baseline levels, inventories, and risk assessment of the POPs polychlorinated biphenyl (PCBs) and organochlorinated pesticides (OCPs), in surface sediment of the DRM. Samples were collected in December 2010 and July 2011, i.e., four years before the Fundão dam failure. The total PCBs and the OCPs (Aldrin, HCHs, and Chlordanes) were detected in both sampling campaigns, with levels up to 9.50 and 1.64, 0.28, and 0.63 ng g^-1, respectively. The decrease of the Doce River flow was the main factor contributing to seasonal variations in the spatial distribution, and to a slight decline in the levels and frequency of the analyzed POPs in sediments collected in the dry season (July 2011). Environmental risk assessment, inventories, and total mass results suggest a low potential of PCBs and OCPs accumulation before the dam failure. This is the first POPs assessment in the study area that helped identify some unexpected impacts of the Fundão dam failure and contributed to the understanding of POPs cycles in the Southern Atlantic, data that are still scarce in the region.

Environmental Background Values and Ecological Risk Assessment of Heavy Metals in Watershed Sediments: A Comparison of Assessment Methods

The distribution and assessment of heavy metal pollution in sediments have been extensively studied worldwide. Risk assessment methods based on total content, background values, and sediment quality guidelines are widely applied but have never been compared. We systematically sorted out these evaluation methods, obtained evaluation results using actual monitoring data, and compared their applicability. The results showed that the background values of different metals are significantly different, which may depend on their mobility. Geoaccumulation index (Igeo) and enrichment factor (EF) values invariably decreased with the increase of background values for individual heavy metal enrichment risk assessment. Compared with EF, Igeo also showed a significant positive linear correlation with heavy metal content. Pollution load index (PLI), modified contamination degree (mCd), and potential ecological risk index (RI) showed significant differences in response to background values and evaluation levels for the comprehensive risk of heavy metal enrichment, but their distribution trends along with the sampling points were basically identical. Toxic risk index (TRI), mean ERM quotient (mERMQ), and contamination severity index (CSI) were used to evaluate the damage degree of complex heavy metals to aquatic organisms and shared a similar whole-process distribution trend. The modified hazard quotient (mHQ), which is used to evaluate the toxicity of a single heavy metal to aquatic organisms, showed a significant positive linear correlation with the total content of each heavy metal, indicating that the toxic effect on organisms can be predicted through the direct monitoring. The results of this study have important guiding significance for the selection of evaluation methods for heavy metal pollution in sediments.

Co-occurrence and potential ecological risk of parent and oxygenated polycyclic aromatic hydrocarbons in coastal sediments of the Taiwan Strait

Thirty-two surface sediment samples, collected from the Taiwan Strait (TWS), were investigated for the occurrence, composition profile, and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs). PAHs were ubiquity in the TWS with a total concentration (∑PAHs, excluding naphthalene due to its high volatility) ranging from 17.8-213 ng g^-1. Benzo[b] fluoranthene, fluoranthene, phenanthrene, and pyrene were the predominant PAHs. Also, eight OPAHs were detected, having a cumulative concentration range (∑OPAHs) of 10.5-118 ng g^-1, predominated by anthraquinone and 6H-Benzo[c,d]Pyren-6-one. Higher concentrations of ∑PAHs and ∑OPAHs were detected at sampling sites adjacent to the mainland and in the northwest part of the TWS. The results suggested important continental input, and particle sedimentation under the specific hydrodynamic conditions of the region. Based on the measured concentrations and sediment quality guidelines, PAHs had a limited ecological impact on the area.

Metallic contamination of global river sediments and latest developments for their remediation

This review article represents the comparative study of heavy metal concentration in water and sediments of 43 important global rivers. The review is a solitary effort in the area of heavy metal contamination of river-sediments during last ten years. The interpretation of heavy metal contamination in sediments has been verified with different indices, factors, codes and reference guidelines, which is based on geochemical data linked to background value of metals. It is observed that health hazards arise due to dynamics of movement of metals between water and sediments, which is primarily influenced by several factors such as physical, chemical, biological, hydrological and environmental. Also, the reason behind accumulation and assimilation of heavy metals on river water system is explained with appropriate mechanisms. Several factors e.g. pH, ORP, organic matter etc. are mainly involved in the distribution, accumulation and assimilation of metals in the sediment phase to water phase. Remediation technologies such as in-situ and ex-situ have been discussed for the removal of heavy metals from contaminated sediments. We have also compared the performance efficiencies of the technologies adopted by different researchers during the period 2003 to 2019 for the removal of metal bound sediments. Many researchers have preferred in-situ over ex-situ remediation due to low cost and time saving remediation effects. In this work we have also incorporated the safety measures and strategies which can prevent the metal accumulation in sediments of river system.

Spatial distribution and consequences of contaminants in harbour sediments - A case study from Richards Bay Harbour, South Africa

Richards Bay Harbour (RBH) is situated in the industrialized area on the northeast coast of South Africa. To decipher recent human activities and accompanying environmental degradation, surface sediment was collected across RBH and analysed for granulometric and elemental composition, microfaunal assemblages, and microplastics. Microplastics occur most abundantly near recreational areas, whereas metal contamination relates to activities at bulk goods terminals from which they are imported or exported. In particular, Cr and Cu concentrations in surface sediment near bulk goods terminals exceed South African sediment quality guidelines. In metal contaminated sediment, bioindicators reflected stress and were noticeably impacted. A transect of short sediment cores reflects spatial and historical metal contamination and allows quantification of the load of metals within the sediment column. The volume of metal (Cr) contaminated sediment was estimated at almost 2 million m³.

Spatial distribution, contamination assessment and potential ecological risk of some trace metals in the surface sediments of the Gulf of Tunis, North Tunisia

To evaluate the trace metals contamination status in the Gulf of Tunis, forty one sediment samples were analyzed using different approaches. According to certain contamination and ecological risk indices (Contamination Factor, Geoaccumulation index and Ecological risk index), Hg has the highest contamination level while pollution by Ni, Pb, Cd and Cr was absent. The highest concentrations of trace metals were found in sediments collected from the offshore and coastal areas located opposite the main exchange points with the gulf particularly, the Mejerda and Meliane Rivers, the Khalij Channel, Ghar El Melh and El Malah lagoons, Tunis Lake and Sebkhat Ariana. However, further ecological indices (Potential ecological risk index, Toxic unit and Mean effect-range median quotient) and comparison with sediment quality guidelines suggest that in addition to Mercury, Cr, Pb and Ni concentrations are detrimental to biota in both the offshore and areas near to the exchange points with the gulf. Moreover, in these areas the results from sequential extraction and individual contamination factor calculation pointed to the mobility and bioavailability of Cr, Pb and Ni.

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.

Efficiency of Fez WWTP: multi-parameter evaluation of water and sediment quality

In order to assess the impact of the proper functioning of wastewater treatment plants (WWTPs) and sanitation networks on the quality of water and surface sediments of the Oued Fez River and its tributaries, and ultimately their outlet in the Sebou River, physico-chemical, geochemical and mineralogical analyses were performed. The components were studied in high- and low-water regimes at eight sites. Seven heavy metals (As, Cd, Cr, Cu, Ni, Pb and Zn) were investigated in the sediments, with a decreasing trend being identified as Zn > Cu > Pb > Cr > As > Ni > Cd, and a mobility sequence as Cu > Pb > Zn > Ni > Cr. A comparison of the total heavy metal concentrations in the Oued Fez and Sebou River sediments with those of previous studies indicated a reduction in the harmful and polluting contribution of the Oued Fez to the Sebou River. The heavy metal assessment was achieved using environmental indices and sediment quality guidelines. The obtained results indicate that the presence of heavy metals in the sediment mainly comes from anthropogenic activities. Based on these results and their comparison with those from previous studies, the contribution of WWTPs and sanitation networks to improving the water quality of the middle Sebou River is clearly noteworthy.