Mean Effects Range-median Quotient Research Articles

Metal Pollution Chronology and Ecological Risk Assessment in Marine Sediments of Perama - Salamina strait, Saronikos gulf, Greece

Three marine sediment cores were studied in terms of lithology, organic carbon content and heavy metal concentrations, aiming to address potential pollution loads in the area between Perama (Attica) and the island of Salamina (Saronikos gulf), which has been subjected for many decades to multisource environmental stress. Statistical analysis, combined with 210Pb sediment dating, was used to investigate pollution sources through time. Ecological risk assessment was based on the Enrichment Factor, Geoaccumulation Index, Pollution Loading Index, mean Effect Range Median quotient and potential ecological Risk Index indices. Results revealed that the upper 40cm sediment layer experience contamination in the following metals: Ag, As, Cd, Cu, Ni, Pb, Sn and Zn, deposited during the past 65 years approximately, under high sedimentation rates and from different metal sources. A slight reduction trend of the heavy metal accumulation into the study area is noted for the most recent years.

Assessment of parent and alkyl -PAHs in surface sediments of Iranian mangroves on the northern coast of the Persian Gulf: Spatial accumulation distribution, influence factors, and ecotoxicological risks

Spatial patterns, potential origins, and ecotoxicological risk of alkylated (APAH) –and parent –(PPAH) polycyclic aromatic hydrocarbons (PAHs) were studied in mangrove surface sediments along the northern coasts of the Persian Gulf, Iran. The mean total concentrations (ngg−1dw) ∑32PAH, ∑PPAHs and ∑APAHs in sediments were 3482 (1689–61228), 2642 (1109–4849), and 840 (478–1273), respectively. The spatial variability was similar among these PAH groups, with the highest levels occurring in Nayband National Marine Park (NNMP). Physicochemical environmental factors, such as sediment grain size, and total organic carbon (TOC) contents, are significant factors of PAH distribution. These findings suggest that PAH pollution level is moderate-to-high, supporting the current view that mangrove ecosystems are under intensive anthropogenic impacts, such as petrochemical, oil and gas loads, port activities, and urbanization. Non-parametric multidimensional scaling (NPMDS) ordination demonstrated that NNMP mangrove is the critical site exhibiting high loading of PAH pollutants. Here, for the first time in this region, Soil quality guidelines (SQGs), Toxic equivalency quotient (TEQ), Mutagenic equivalency quotient (MEQ), and composition indices comprising Mean maximum permissible concentration quotient (m-MPC-Q), and Mean effect range median quotient (m-ERM-Q) methods were used to have a comprehensive risk assessment for PAH compounds and confirmed medium-to-high ecological risks of PAHs in the study area, particularly in the western part of the Gulf, highlighting the industrial impacts on the environment.

Assessing the ecological and health risks associated with heavy metal pollution levels in sediments of Big Giftun and Abu Minqar Islands, East Hurghada, Red Sea, Egypt

This study assessed pollution levels, ecological and health risk, and spatial distribution of eight heavy metals in sediments of Big Giftun and Abu Minqar Islands, Red Sea, Egypt. Iron (Fe) and manganese (Mn) had the highest contents in both island sediments, while cobalt (Co) in Big Giftun and cadmium (Cd) in Abu Mingar had the lowest values. The obtained PCA data exhibited positively significant loadings of Cd, Co, copper (Cu), nickel (Ni), and zinc (Zn) with 51.03 % of data variance in Big Giftun, and lead (Pb), Cu, Mn, Ni, Zn, and Fe (37.7 %) in Abu Minqar sediments. The contamination factor (CF) showed low contamination for all metals, except cadmium; Cd (moderate). The geo-accumulation index (Igeo) values showed uncontaminated (Cd, Co), moderately (Cu), extremely contaminated (Fe, Mn) (Igeo > 5) in Big Giftun, and uncontaminated (Cd), moderately to strongly contaminated (Cu, Ni), and extremely contaminated (Fe, Mn, and Zn) in Abu Minqar sediments. The pollution load index (PLI) values indicated baseline level of contamination (PLI <1), and degree of contamination (DC) indicated low degree of contamination (DC < n) in all sediments. Nemerow pollution index (NPI) showed unpolluted sediments in Abu Minqar (NPI ≤1) and slight pollution (1 < NPI ≤2) in Big Giftun. Cd showed moderate potential ecological risk (40 ≤ Eri < 80) in Big Giftun sediments. Potential ecological risk index (PERI) indicated low risk sediments (PERI <150). Mean effects range median quotient (MERMQ) indicated low-priority risk of toxicity (MERMQ ≤0.1), and toxic risk index (TRI) showed no toxic risk in all sediments (TRI <5). The modified hazard quotient (mHQ) indicated very low severity of contamination (mHQ <0.5). The hazard quotient (HQ) levels of all metals were below the safe value (HQ <1). The hazard index (HI) levels indicated that no chronic risks occur (HI <1). The total cancer risk (TCR) for all metals were below the safe level (1 × 10−4) of the United States Environmental Protection Agency (U.S. EPA) guidelines.

Application of machine learning and multivariate approaches for source apportionment and risks of hazardous elements in the cropland soils near industrial areas in Bangladesh

Quick industrial and urban development accelerates the hazardous elements (HEs) content in agricultural soil which is a matter of concern for ecological and public health. This present study investigates the HEs content (As, Pb, Cd, Cr, Ni, and Cu) in agricultural fields near industrial areas of Bangladesh to assess the metal concentration, distribution, sources apportionment, and their probable ecological and human health impacts using an integrated approach of machine learning and multivariate indices. Principal component analysis (PCA) showed about 28.9% of spatial variation of HEs in the study area. Metal concentrations were compared to international soil quality standards (ISQSs) and found that Cd, Ni, and Cu exceeded the ISQSs while about 80% and 100% of samples surpassed the Toxic reference value for Cd, Cr, Ni, and Cu, respectively. All HEs contents exceeded the background value excluding As. According to Positive matrix factorization (PMF) analysis, three possible sources controlled HEs content in the study area: (i) anthropogenic (Cd; 79%); (ii) mixed sources (Cu; 76%), (Ni; 51%), (Cr; 48%), and (As; 39%); and (iii) atmospheric fallout (Pb; 67%), that is corresponding by self-organizing map (SOM), and random forest (RF). The pollution load index indicated that about 77% area was polluted by studied HEs. Additionally, other pollution evolution indices including mean Effect Range Median quotient (0.31 ± 0.05), Nemerow pollution index (2.64 ± 1.13), Degree of contamination (8.20 ± 2.16), and Modified hazard quotient (1.69 ± 0.19), exhibited moderate contamination of HEs in soil samples. Based on ecological risk about 20–53% of samples were moderate to high risk, while the descending order of HEs was Cd > Pb > Ni > As > Cr > Cu. For the public health aspect, no significant non-carcinogenic health risks (THI < 1) for adults (female = 1.03E-01 and male = 9.50E-02) and children (6.83E-01), while moderate carcinogenic health risks for adults (female = 2.65E-05and male = 2.36E-05), and children (4.37E-05). Overall, this study area soils are polluted with HEs mainly by anthropogenic activities, which have significant health hazards for the inhabitants.

Environmental hazard assessment and metal contamination in coastal sediments

In order to reduce contamination levels from diverse sources, it is important to understand the factors affecting the natural ecosystems that are impacted by coastal and marine pollution. In this study, we used GIS and remote sensing techniques to investigate and evaluate the distribution of heavy metals (Fe, Mn, Zn, Cr, Pb, Co, and Cu) in surface sediments along Tamil Nadu's East Coast (from Besant Nagar to Sathurangapattinam). The CF and Igeo of metals indicate that sediments contain no evidence of Fe, Mn, or Zn metal pollution in the sediments, with only mild contamination from Co, Cu, and Pb. In contrast, the sediment samples were found to be significantly contaminated with Cr. Heavy metal contamination occurs in the following order, according to our research: Cr > Pb > Cu > Co > Mn > Zn > Fe. Except for sites 8, 10, 11, and 13, where PLI>1 implies that there is no pollution in this area, the PLI values show that most of the locations are contaminated. The ecological risk index (ERI) values for five metals in the study areas are as follows: Cr > Pb > Cu > Mn > Zn. The sediment samples fall into the low-risk and highly polluted to dangerous sediment categories for SPI, according to the Risk index (RI). Based on the Mean Effect Range-Median Quotient (M-ERM-Q), Cu, Pb, Zn, and Cr metals in the research region have a 9–21% probability of being harmful. Statistical approaches show that the majority of heavy metals in sediments are of natural origin. The spatial distribution of heavy metals in surface sediments provides the conceptual framework for practical strategies to protect coastal areas. Many shreds of evidence indicate that anthropogenic inputs from the surrounding land area are primarily responsible for the deposition of these heavy metals in the coastal zone.

An integrated overview of metals contamination, source-specific risks investigation in coal mining vicinity soils.

Heavy metals in soil are harmful to natural biodiversity and human health, and it is difficult to estimate the effects accurately. To reduce pollution and manage risk in coal-mining regions, it is essential to evaluate risks for heavy metals in soil. The present study reviews the levels of 21 metals (Nb, Zr, Ag, Ni, Na, K, Mg, Rb, Zn, Ca, Sr, As, Cr, Fe, Pb, Cd, Co, Hg, Cu, Mn and Ti) in soils around Barapukuria coal-mining vicinity, Bangladesh which were reported in literature. An integrated approach for risk assessments with the positive matrix factorization (PMF) model, source-oriented ecological and health hazards were applied for the study. The contents of Rb, Ca, Zn, Pb, As, Ti, Mn, Co, Ag, Zr, and Nb were 1.63, 1.10, 1.97, 14.12, 1.20, 3.13, 1.22, 3.05, 3.85, 5.48, and 7.21 times greater than shale value. About 37%, 67%, 12%, and 85% of sampling sites posed higher risks according to the modified contamination factor, Nemerow pollution index, Nemerow integrated risk index, and mean effect range median quotient, respectively. Five probable metal sources were computed, including industrial activities to coal mining (17%), agricultural activities (33%), atmospheric deposition (19%), traffic emission (16%), and natural sources (15%). Modified Nemerow integrated risk index reported that agricultural activities, industrial coal mining activities, and atmospheric deposition showed moderate risk. Health hazards revealed that cancer risk values computed by the PMF-HHR model with identified sources were higher than the standard value (1.0E-04) for children, adult male, and female. Agricultural activities showed higher cancer risks to adult male (39%) and children (32%) whereas traffic emission contributed to female (25%). These findings highlight the ecological and health issues connected to potential sources of metal contamination and provide useful information to policymakers on how to reduce such risks.

Multi-dimensional approach for an environmental health assessment of a deltaic mangrove ecosystem, Sundarbans

The largest contiguous tract of tidal halophytic mangroves in Bangladesh is about 10,000 km2. It has a wide range of physiochemical and nutritional qualities, as well as ecological health. To understand the hazardous and heavy metal concentrations, ten heavy metals concentrations were examined in both water and sediment. Indices for pollution and contamination, such as Modified Hazard Quotient (mHQ), Degree of Contamination (Cd), Geo-Accumulation Index (Igeo), Mean Effect Range Median Quotient (M-ERM-Q), Nemerow's Pollution Index (NPI), Heavy Metal Evaluation Index (HEI) give a more accurate diagnostic result for water and sediment in the Sundarbans mangroves. The Water Quality Index (WQI) and Mangrove Quality Index (MQI) are also evaluated for a final statement. The nutrient concentrations average of NO3, PO4, NH3, and SiO2 are found 0.59 ± 0.05, 0.09 ± 0.01, 0.23 ± 0.02 and 1.72 ± 0.17 (mg/L), respectively in water. Pb, Cd, Hg, As, Cr, Mn, Fe, Ni, Cu, and Zn have average concentrations of 19.1 ± 1.62, 1.1 ± 0.11, 0.48 ± 0.04, 1.19 ± 0.11, 83.27 ± 8.3, 35.45 ± 2.95, 282.73 ± 30.82, 33.85 ± 2.95, 6.09 ± 0.54, and 172.18 ± 17.15 (µg/L) in surface water and 19.57 ± 1.25, 0.16 ± 0.005, 0.026 ± 0.0009, 1.48 ± 0.08, 36.38 ± 4.31, 456.66 ± 76.76, 42.36 ± 2.57, 53.81 ± 1.93, 20.67 ± 1.24, and 43.60 ± 6.09 (mg/kg) for sediments. According to the heavy metals analysis indices, we discovered very little contamination. The WQI indicates that the water quality in the Sundarbans Mangroves is generally protected but occasionally deteriorates. The MQI categorizes the Sundarbans as a moderate mangrove, falling into category 3. Despite being controlled the heavy metal pollution is getting worse as the Mongla port's economy grows. A more seasonal and in-depth approach to this topic can be achieved by collecting more samples over a year. The deltaic Sundarbans mangrove ecosystem is currently in moderate to an acceptable condition, with low or non-significant pollution levels and fair water quality, according to this study, except for certain constraints.

Assessment of seasonal variation in distribution, source identification, and risk of polycyclic aromatic hydrocarbon (PAH)-contaminated sediment of Ikpoba River, South-South Nigeria.

The study aims to assess the seasonal variation in distribution, source identification, and risk of 20 polycyclic aromatic hydrocarbons (20 PAHs) in the sediment of the Ikpoba River, south-south Nigeria. The PAHs were extracted in an ultrasonic bath with a mixture of n-hexane and dichloromethane (1:1 v/v). The extract was cleaned by silica-alumina gel mixed with anhydrous Na2SO4 in a chromatography column, eluted by n-hexane, and analysed by gas chromatography-mass spectrometry. The range of the average PAHs in mg.kg-dw was 0.15 (Nap)-0.54 (Acy) and 0.13 (D.al.P)-0.99 (Acy) in wet and dry periods correspondingly, indicating an increase in concentration from wet to dry period. However, the rings of the average concentration of the PAHs show 6 and 3 rings to be the highest values during the wet and dry seasons, respectively. Based on the human health risk analysis, the hazard quotient (HQ) and hazard index (HI), and carcinogenic risk indices showed low non-carcinogenic and carcinogenic risk for both seasons. The ecological risk analysis showed the mean effect range median quotient (mERMQ) recorded a medium-low effect on the biota of the locations, except in AS3 during the wet season and also in WS8 and WS9 during the dry season. The minimum value of the toxic equivalent quotient (TEQ) was > 0.2mg/kg, which indicated a recommendation for the clean-up of the Ikpoba River. The isomer ratio and the principal component analysis (PCA) revealed the sources of the PAHs to be majorly combustion, followed by pyrolytic and petrogenic sources for both seasons.

Distribution, risk assessment, and quantitative source apportionment of heavy metals in surface sediments from the shelf of the northern South China Sea

The concentration of heavy metals (Cu, Pb, Zn, Cr, Co, and Ni) from 421 sediment samples from the shelf of the northern margin of the South China Sea (SNSCS) was analyzed. The heavy metal content and calculated potential ecological indicators (Eri < 40 and RI < 160) indicate that there is low potential ecological risk of heavy metal pollution in the SNSCS. The mean effects range-median quotient (M-ERM-Q) and hazard quotient (HQ) values of sediment toxicological characteristics indicate that heavy metals are a potential toxicological risk. The high-risk area is mainly distributed in the southwest of the nearshore SNSCS. The positive matrix factorization (PMF) analysis results showed that major contributors to heavy metal pollution were natural sources and anthropogenic activities in the SNSCS. The government should pay particular attention to the monitoring of heavy metals in the nearshore southwest of the SNSCS.

Distribution, sources, and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in Kaokaowusu river sediments near a coal industrial zone.

This study systematically analyzed the contents, compositions, and sources of polycyclic aromatic hydrocarbons (PAHs) in river sediments near an important energy and chemical base in northwest China. In addition, their possible adverse effects on the ecology and human health were assessed. The PAH concentrations in this study area ranged from 2641.28 to 16783.72 (ng/gdw). PAHs of medium molecular weight (3-ring and 4-ring) showed the largest proportion, followed by PAHs of higher molecular weight (5-ring and 6-ring). The results of molecular diagnostic ratios and principal component analysis revealed that PAHs in the region have complex sources, with incomplete combustion of local fossil fuels and traffic exhaust factors being the main sources. The total toxic equivalent concentration of PAHs varied from 10.05 to 760.26ng/g, and according to the sediment quality guidelines, PAHs have high potential ecological risk in the lower reaches of the river. The mean effect range-median quotient for the region was 0.46, and the combined ecological risk was at moderate to high levels (21% probability of toxicity). The lifetime carcinogenic risks for adults and children exposed to PAHs were 2.95 × 10-3 and 1.87 × 10-2, respectively, which are much higher than the limit of 10-4, indicating moderate to high potential cancer risks. Therefore, the local government should consider taking some environmental remediation measures. This study can provide theoretical support for pollution prevention measures and ecological restoration strategies for rivers in resource-rich areas.

Comparing the applicability of ecological risk indices of metals based on PCA-APCS-MLR receptor models for ports surface sediments

This study collected surface sediments from seven ports in Taiwan and analyzed their characteristics along with 10 metals. Enrichment factor (EF), relative EF (REF), potential ecological risk index (PERI), and mean effect range median quotient (m-ERM-q) were used to evaluate the levels of metal contamination and ecological risks in sediments. Principal component analysis (PCA) and the absolute principal component score-multiple linear regression (APCS-MLR) model were applied to quantify the main factors affecting the variations in sediment metals. The different normalization techniques that vary between indexes significantly affect the estimates of risk levels for sediment metals. APCS-MLR model confirmed the significant difference among the sediment quality indices in the degree of anthropogenic pollution, ranging in the order of REF (normalized with reference site and Fe, 97.0 %), PERI (normalized with reference site, 85.5 %), EF (normalized with crust and Fe, 79.4 %), and m-ERM-q (not normalized, 56.6 %).

Distribution, sources and ecological risk assessment of polycyclic aromatic hydrocarbons in waters and sediments from Olt River dam reservoirs in Romania

This study provides important data on the distribution, sources and ecological risks of polycyclic aromatic hydrocarbons (PAHs), in surface waters and sediments collected from dam reservoirs on middle and lower course of the Olt River, the main tributary of the Danube, until the discharge into the Black Sea. A wide variation range of total PAHs concentrations in water (from 1.3 to 46.2 ng/L) and sediment (from 1.78 to 614.04 μg/kg) samples was emphasized by the results. The highest average PAHs concentration in water was recorded in the cold season and the lowest in the summer. In sediments, no differences were observed depending on the sampling period. Spatial distribution of PAHs in waters and sediments was correlated with the main anthropogenic activities along the river course. Regardless of the method used to attribute PAH sources (diagnostic ratios of specific PAHs, principal component analysis and hierarchical cluster analysis), it was confirmed that the potential anthropogenic sources of PAHs were both pyrogenic (incomplete combustion of biomass and coal) and pyrolytic (incomplete combustion of liquid fossil fuels and vehicle exhaust emissions), with a dominant pyrolytic input. Ecological risk assessment based on environmental quality standards, mean effect range-median quotient (m-ERM-Q), toxic equivalency factors (TEFs) and risk quotient (RQ) methods indicated potentially low ecological risks from PAHs. The ecological status of the Olt river waters poses no potential risk, and pollution of surface sediments can be classified as low polluted, except for two sites near industrial activities classified as moderately polluted. Therefore, a regular monitoring of PAHs concentration in the waters and sediments should be performed to prevent further contamination of PAHs in the studied area, especially in densely populated industrial areas.

Seasonal congener survey for polychlorinated biphenyls in sediments of south-western rivers, Nigeria: Occurrence, sources, and ecotoxicological risks

In this work, sediment samples from major rivers within southwestern Nigeria were collected to study the seasonal distribution, transport, and ecological risk assessment of polychlorinated biphenyls (PCB) using gas chromatography coupled with an electron capture detector (GC–ECD). The ΣPCB concentrations ranged from 9.86–77.56 μg/kg and 11.88–80.76 μg/kg in dry and wet seasons respectively. The most predominant PCBs congener in all the sediments was 2,2’,4,5,5’-PeCB(#101) with mean concentrations of 4.35 ± 2.96 and 6.10±3.38μg/kg across all locations in dry and wet seasons respectively. Relevant guidelines including sediments quality guidelines (SQGs) mean effect range-median quotient (m-ERM-Q), and toxic equivalent factor (TEF) were used for risk assessment and to evaluate the ecological risks of PCBs across the rivers. The toxic equivalent quantity (TEQ) ranged from 0.044–0.807 μg-TEQ/kg and 0.055–0.825 μg-TEQ/kg for the dry and wet seasons respectively. The non-ortho PCBs congeners constituted ≥ 99.8% of the ∑TEQ values. The seven indicators PBCs for evaluating non-dioxin-like PCBs ranged from 3.70–32.69 μg/kg across the seasons and accounted for 33.4%, 39.8%, 36.8%, 37.9%, 41.4%, and 40.4% of the ∑PCBs at Asejire, Odo Ona, Ogbese, Ogun, Ikorodu rivers and Third Mainland Bridge Ocean respectively. In two out of six rivers, the ∑PCBs exceeded the Canadian SQG threshold effect level of 21.5 and 34.1μg/kg for fresh and marine sediments respectively. The results of the study call for a concerted effort toward holistic monitoring of PCB residues in rivers in Nigeria to ensure ecological integrity and the protection of human health.

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%, 648ppm, 12ppm, 12ppm, 16ppm, and 25ppm, respectively, while core C-2 revealed their average concentration as 1.34%, 709ppm, 10ppm, 11ppm, 13ppm, and 28ppm respectively. In core C-3, an average concentration of Fe, Mn, Cu, Co, Ni, and Zn was 1.72%, 907ppm, 14ppm, 13ppm, 18ppm, and 31ppm 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 (Igeo) 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.

Sources, Toxicity, Health and Ecological Risks of Polycyclic Aromatic Hydrocarbons (PAHs) in the Sediment of an Osogbo Tourist River

ABSTRACT This study investigated twenty-three polycyclic aromatic hydrocarbons (PAHs) in the sediment of Osun River, spanning through both the peri-urban and urban areas of the river, to estimating their sources, ecological and health hazards. The sampling locations covered those beside major roads and agricultural farms. They were analyzed by gas chromatography-mass spectrometry. The concentrations of the PAHs ranged 88–1900 ng/g (average, 731 ng/g) with the predominance (56%) of benzo(e)pyrene (BeP). Though the PAHs had a similar trend of distribution in the sediment at both peri-urban and urban portions, total PAHs concentration at the peri-urban area was three times higher than that obtained in the urban area of the river due to relatively lower photo-degradation process caused by the thick rain forest in the area. Pyrolytic processes such as coal/wood burnings and emissions from gasoline and diesel engines were the PAHs sources. No dermal carcinogenic or non-carcinogenic health concerns were posed by the individual PAH; cancer risk and hazard quotient values were <10−6 and <1.0, respectively. The sediment PAHs posed a low ecological risk in all the sampling locations as the mean effects range-median quotient of the individual USEPA priority PAHs was ≤0.04. The potential environmental toxicity of the priority PAHs showed that benzo(a)pyrene (BaP) and indeno[1,2,3-cd]pyrene (IDcdP) dominated, accounting for 37% and 44% of the total toxicity, respectively. The low health and ecological risks posed by the PAHs sediment became significant given the number of tourists Osun River attracts annually festival, as well as the effects on the river ecosystem.

Contamination and ecological risk assessment of trace metals in surface sediments from coastal areas (El Jadida, Safi and Essaouira) along the Atlantic coast of Morocco

Concentrations of four trace metals (Cd, Cr, Cu and Zn) in surface sediments were quantified seasonally to evaluate the metal contamination and to determine the possible environmental risks at three coastal areas in northwest Morocco (El Jadida, Safi and Essaouira). Sampling was conducted quarterly at six intertidal stations with two stations per area (north to south: El Jadida: S1 vs. S2; Safi: S3 vs. S4 and Essaouira: S5 vs. S6). The trace metal concentrations were generally found to be greater in wet seasons for all sampling stations, and their mean values were arranged in the following decreasing order: Zn (28.35–136.10 μg g−1 dry weight) > Cr (6.50–130.90 μg g−1) > Cu (5.00–83.40 μg g−1) > Cd (0.02–5.95 μg g−1). As expected, the highest metal concentrations were recorded at stations exposed to the polluting point-source discharges from important industrial phosphate plants near El Jadida (S2-Jorf Lasfar) and Safi (S4-Jorf Lihoudi), which greatly exceeded the geochemical background values (Cd: 0.3 μg g−1 dry weight, Cr: 90 μg g−1, Cu: 45 μg g−1 and Zn: 95 μg g−1). All of the four trace metals were significantly correlated with each other, implying the same source of contamination and a similar pollution history. This was mainly derived from industrial waste generated by these huge phosphate industry plants. Meanwhile, results from hierarchical cluster analysis confirmed the findings from the correlations. This ecotoxicological evidence was primarily associated with untreated industrial discharge. The contamination Factor, degree of Contamination, and modified Degree of Contamination indices confirmed that these two stations were the metal contamination hotspots, and the most affected in this region, especially for Cd. Moreover, Pollution Load Index and Geo-accumulation Index reflected a spatial distribution of pollution following the decreasing sequence S4 > S2 > S1 > S6 > S3 > S5. Based on the Potential Ecological Risk Index, Cd concentrations indicated a moderate to very high potential ecological risk at all sampling stations, except at one pristine station S5 (Bhibeh). The spatial distribution of Mean-Effect Range Median-Quotient (M-ERM-Q) showed a negligible ecological risk at Cap Beddouza (S3) and Bhibeh. The mean values of Toxic Units (Σ TU) were found in the following decreasing order Cd > Cu > Cr > Zn, with a major contribution to the Σ TU coming from Cd (35.42%) and Cu (24.99%). Comparison of the current results with those found in other areas around the world revealed that the metal levels obtained here are in general low, except for Cd, which appeared to be in higher concentrations. Concentrations of Cd, Cr and Cu in sediments at S2 and S4 exceeded either the Threshold Effect Level of the Canadian sediment quality guidelines and Effect Range Low of the US National Oceanic and Atmospheric Administration, which demonstrated that these trace elements posed environmental risks while Zn appeared to present no environmental threat at all of the studied areas.

Distribution, sources and risk assessment of PAHs in soil from the water level fluctuation zone of Xiangxi Bay, Three Gorges Reservoir.

Information on PAH distribution in the water level fluctuation zone (WLFZ) of Three Gorges Reservoir is limited. In this study, we investigated PAH distribution and sources and assessed PAH risks, over one annual water level fluctuation cycle (June 2017-June 2018) at four elevations spanning the WLFZ (145m, 155m, 165m and 175m) at seven locations in the water level fluctuation zone along Xiangxi River. The mean total PAH concentration in June 2018 (953ngg-1) was significantly higher than in June 2017 (494ngg-1), and the horizontal and vertical distributions of PAHs changed significantly. The changes in distribution patterns provided evidence for the cause of increased PAH levels, which were attributed to construction of the Xiangxi River Bridge. Thus, this study of PAH dynamics in the WLFZ soils of Xiangxi Bay also provided valuable information on the impact of bridge construction on WLFZ soils. The change in PAH levels among stations implicated sediment disturbance resulting from bridge construction as the major contributor to the increased PAH levels. Source characterization, based on the ratios of certain PAHs, indicates that PAHs are mainly from the combustion of petroleum fuels, biomass and coal. These ratios indicated that the proportion of PAHs from fuel combustion increased from 2017 to 2018, implicating the heavy equipment used during bridge construction as another source of the increased PAH levels. The incremental lifetime cancer risk (ILCR) model was used to assess the health risk of the PAHs and the range among all age groups (10-5-10-4) indicates a potential health risk. The mean effects range-median quotient (M-ERM-Q) was used to assess the ecological risk of PAHs and the range (0.1-0.5) indicates low to medium risk. The increase in PAH levels from 2017 to 2018 increased the risk to public health and the environment. The results of this investigation provide a reference for ecological restoration of the WLFZ and support development of effective policies for environmental and public health. Further, the results provide information on the impact of bridge construction on WLFZ soils and identify research needed to more fully understand PAH dynamics in WLFZ soils.

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.

Spatial distribution, source analysis, and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the sediments from rivers emptying into Jiaozhou Bay, China

Sediment samples had been collected from five major rivers into Jiaozhou Bay, China to study the spatial distribution, sources, and ecological risks of 16 priority polycyclic aromatic hydrocarbons (PAHs) in April 2018. Results showed that the contents of PAHs in the sediments from the five rivers were significantly different. The distribution trend was Dagu < Yang < Licun < Baisha < Moshui River. The contents of PAHs in the eastern rivers were higher than those in the western portions. The contribution rate of HMW-PAHs was higher than LMW-PAHs in the sediments, with the majority of PAHs being four rings. PAHs in sediments were mainly derived from combustion sources, including the incomplete combustion of petroleum, coal, and wood. The benzo[a]pyrene toxic equivalent method (TEQ) showed that Moshui River had a high risk of carcinogenesis. The evaluation results of Effects Range Low(ERL), Effects Range Median (ERM) and Mean- Effects Range Median-quotient (M-ERM-Q) showed that PAHs in the sediments of Moshui River would occasionally have adverse biological effects, as well as possible medium and low ecological risks. The ecological risks of PAHs in the sediments of the other four rivers were low. Hence, we should focus on and control the input of PAHs in the Moshui River.

Spatial distribution and level of contamination of potentially toxic elements in sediments and soils of a biological reserve wetland, northern Amazon region of Ecuador

This study quantifies the degree of pollution and assess the ecological risk of As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, V and Zn in sediments and soils of the Limoncocha Biological Reserve (Ecuador), identified as a Ramsar site with high ecological and socioeconomic value. The hydrologic system of the Reserve is mainly formed by two rivers that drain into the Limoncocha lagoon, which occupies only five percent of the protected area but support a high anthropic influence. Local statistical baseline of studied potentially toxic elements is established using cumulative frequency method, and Al is selected as reference element due to the good correlation with the studied elements. The grade of pollution and the potential ecological risk are evaluated applying three individual (Contamination Factor, Geo-accumulation Index and Enrichment Factor) and six integrated (Degree and modified degree of contamination, Pollution Load Index, Nemerow and modified Nemerow pollution indexes and potential ecological risk index) indices. Results analysis are based on the combined application of traditional statistics, multivariate data analysis and self organizing maps. Outcomes suggest to classify sediments and soils as “moderate contamination and enrichment” due mainly to the concentrations of Cu (66.4–110 mg/kg) and Cd (0.0262–0.808 mg/kg), derived from domestic wastewaters and agricultural activities, and in a lesser extent due to Mo (0.822–4.37 mg/kg), Ni (10.3–25.8 mg/kg), Co (7.27–24.8 mg/kg) and V (60.3–178 mg/kg), derived from oil field drilling activities. The distributions of As (0.328–8.83 mg/kg), Ba (143–1100 mg/kg), Pb (7.20–26.5 mg/kg), Zn (60.1–276 mg/kg) and Cr (10.1–48.6 mg/kg) are heterogeneous in the studied sampling sites. Sediments located next to the pier and at the central area of the Limoncocha lagoon, show moderate potential risk and according to sediment quality guidelines, the calculated mean Effect Range Median quotient (mERMq) classify the sites as medium-low priority risk level. A three-level classification of a mean quotient based on soil quality and soil potential uses is proposed. Soil sites with high anthropogenic activities show low to moderate potential ecological risk being classified as poor soil quality sites but with all potential soil uses allowed according to the legal limits for land uses in Ecuador.