Geochemical partitioning and pollution assessment of Ni and V as indicator of oil pollution in surface sediments from Shadegan wildlife refuge, Iran

Phytoremediation capability of Typha latifolia L. to uptake sediment toxic elements in the largest coastal wetland of the Persian Gulf

The present study evaluated the status of sediment toxicity and pollution, and the phytoremediation capability of Typha latifolia L. (TlL) within the largest coastal wetland in the southwest of Iran, the Shadegan International Wetland. In eight sampling sites, covering the entire wetland, the concentration of six toxic elements (As, Cr, Cu, Ni, Pb, and Zn) in the surface sediment, root, and stem of TlL were measured. The results indicated that mean concentrations of Cr, Cu, Pb, and Zn were found to be higher than those in the local background, which likely indicates anthropogenic sources of these elements. Due to the presence of a nearby landfill, the results of modified pollution index (MPI) and aggregate toxicity index (ATI) indicated a moderately-heavily polluted level and moderate to high toxic degree, respectively. However, the medium-low level of toxicity toward living of organisms (21 % probability) was detected based on the assessment of the Sediment Quality Guidelines (SGQ). The results of our study indicate that the root and stem tissues of TlL are capable of acting as an indicator of Cu/Pb/Zn and Zn pollution in sediment, respectively. Considering the potential of phytoremediation, TlL represented both phytostabilization and phytoextraction capabilities for Pb and Zn and a significant increase was observed in the phytoremediation capability by increasing the distance from the landfill area. According to the results of the metal accumulation index (MAI) and comprehensive bioconcentration index (CBCI), TlL grown in the study area showed an acceptable performance in the accumulation of multiple toxic elements compared to that in Turkey, India, and Poland. Overall, TlL is a good candidate for the phytoremediation of sediments contaminated by Pb and Zn.

Integrating indices based on different chemical extractions and bioaccumulation in Bellamya aeruginosa to assess metal pollution and ecological risk in sediment

Various indices based on metal chemical data are used to evaluate pollution and ecological risk, but the consistency of the assessment results is usually unsatisfactory, and it is unclear if the ecological risk from sediment metals is accurately represented in in situ zoobenthos. Herein, the pollution and ecological risk associated with As, Cd, Cr, Cu, Ni, Pb and Zn in the sediments of two adjacent lakes (Datun (DT) and Changqiao (CQ)) were comprehensively evaluated by integrating metal concentrations, chemical forms and bioaccumulation in Bellamya aeruginosa (B. aeruginosa). The metal concentrations and chemical compositions varied widely in the sediments. Over 50% of the Cd, Pb and Zn in the sediments was present in bioavailable forms, followed by 28% of Cu and less than 25% of As, Cr and Ni. According to the enrichment factor (EF) and concentration enrichment ratio (CER) assessments, Cr and Ni were natural in origin, while the other metals were at minor to extremely high pollution levels, with average EFs of 1.5-77.6 and CERs of 1.1-113.4. The pollution levels for Cd, Cu and Pb from the EF and CER assessments were similar, while those for As and Zn were higher according to CER than EF (p = 0.05), likely due to the baseline underestimation associated with the potential diagenetic remobilization of bioavailable metals. The ecological risk index (Er), sediment quality guidelines (SQGs) and risk assessment code (RAC) showed a high eco-risk for Cd, while no similar risk was found for the other metals. By integrating risk indices with the chemical forms and pollution levels of metals, we deduced high eco-risks for As and Pb and moderate eco-risks for Cu and Zn in DT Lake and moderate eco-risks for As, Pb and Zn in CQ Lake. The other metals in the sediments of the two lakes presented low eco-risks. No significant positive correlations (p = 0.05) between metal accumulation in B. aeruginosa and the indices of pollution and eco-risk were observed except for the case of As, implying that measuring the metal concentrations in B. aeruginosa would not accurately characterize the metal pollution and ecological risk of sediments.

Modeling Sediment Ni and V Spatial Distribution to Identify Hotspots in the Shadegan Wildlife Refuge, at the Head of the Persian Gulf

The distribution and origins of Ni and V were assigned in the surficial sediments from 160 stations in Shadegan international wetlands with 537,700 ha. The findings showed that the mean total content of Ni and V in the surface sediments were 45.08 ± 12.09 and 25.25 ± 20.8 μg g^-1 dw, respectively. According to the analysis chemical speciation, the Ni and V residual fraction in the surface sediments were calculated for > 80% of the total level of metals, indicating that the metals may be an indicator for the input of natural resources. The analysis of the interpolation maps according to their chemical fractionation manifested that the Ni and V pollution hotspots have been happened in the northern, southern, and western points. Interpolation maps also highlighted that Ni and V are often controlled by natural factors like parent material; however, anthropogenic inputs have also caused the accumulation of these metals in the sediment.

Assessment of potential human health risk due to heavy metal contamination in edible finfish and shellfish collected around Ennore coast, India

This study aims to estimate anthropogenic sources of pollutants such as heavy metals that pollute or poison the commercial marine finfish and shellfish present around the Ennore coastal area and to identify, quantify and manage the associated risks for the betterment of society. The levels of toxic heavy metal concentrations from monitoring and surveillance of copper, chromium, cadmium, mercury, lead and zinc heavy metals were estimated from water, sediment and commercial marine finfish and shellfish samples that were collected for study. The individual mean bioaccumulation index (IMBI) and Metal Pollution Index (MPI) values varied between finfish and shellfish. Target hazard quotient (THQ) index values were calculated, and copper and zinc were found to be elevated at levels affecting children in particular. Thus, efforts are urgently needed to resolve the current and potential risks associated with the negative impact of heavy metal intake from seafood on human health. This study attempts to identify levels of metal contamination and corresponding risk factors with regard to human health.

Total mercury and methylmercury concentrations in native and invasive fish species in Shadegan International Wetland, Iran, and health risk assessment

Human exposure to mercury (Hg) mainly occurs through consumption of aquatics, especially fish. In aquatic systems, the bioaccumulation of Hg across trophic levels could be altered by invasive species through changing community composition. The present study is aimed at measuring total mercury (T-Hg) and methylmercury (MeHg) concentrations in non-native (redbelly tilapia (Tilapia zillii)) and native (Benni (Mesopotamichthys sharpeyi) and common carp (Cyprinus carpio)) fish species throughout Shadegan International Wetland and comparing health risk of their mercury contents to the local population. The concentrations were measured using a direct mercury analyzer (DMA 80). The average values of T-Hg and MeHg for native fishes were 19.8 and 10.49 μg/kg. These concentrations for the invasive fish were 28 and 14.62 μg/kg respectively. Despite having less length and weight than the native fish species, tilapia showed significantly higher T-Hg content, yet the lowest concentration of MeHg was observed in common carp with larger body length and weight. Concerning mercury health risk to consumers, tilapia demonstrated the highest estimated weekly intake (EWI) and percentages of tolerable weekly intake (%TWI) for both T-Hg and MeHg, while the highest hazard quotient (HQ) values were obtained for tilapia and Benni. Taken together, the mercury concentrations in the two native and non-native fishes were acceptable according to the international safety guidelines although the local people shall be warned for consumption of tilapia. Furthermore, the low calculated value of tissue residue criterion (TRC) for the wetland fishes sounds a warning.

Geochemical characteristics, partitioning, quantitative source apportionment, and ecological and health risk of heavy metals in sediments and water: A case study in Shadegan Wetland, Iran

Heavy metal concentrations were investigated in water and sediments of Shadegan Wetland southwest of Iran to assess the fate, partitioning, and risk assessment and also to quantify the sources of heavy metals using MLR-APCS (multiple linear regression of absolute principal component scores) receptor model. The relatively high values of K_d (partition coefficient) for Pb, Zn, Ni, As, and V revealed their affinity for being enriched in sediments while Sb, Mo, and Se exhibited greater partitioning towards water. Enrichment factors of Se, Cd, Pb, Mo, Co, Zn, and Cu revealed significant to moderate contamination and should be of some concern. Application of the modified ecological risk index (MRI) revealed sediments moderate to high risk. Hazard index values for Hg were found less than the safe level. MLR-APCS model indicated that anthropogenic sources in sediments were responsible for 80.9%, 73.2%, 73.1%, 88.6% and 74.2% of Se, Mo, Hg, Pb, and Zn, respectively.

Sediment pollution in an urban water supply lake in southern Brazil

Urbanization and anthropogenic activities create many environmental issues in urban water supply reservoirs, especially in metropolitan regions. Thus, this study was carried out aiming to evaluate the variance in the physical-chemical characteristics of bottom sediment along the Lake Guaíba, Brazil. Lake Guaíba is a freshwater lake situated in a metropolitan region in southern Brazil, being the main water supply to the region. Surface sediment was evaluated to pH, electrical conductivity, particle-size, total organic carbon and nitrogen, metals and inorganic elements (Fe, Al, Ca, Ba, Sr, Co, Tl, Zn, Cu, Cr, Ni, Pb, Cd, and Hg), and organic compounds. The sediments in the Lake Guaíba show a wide range in the physical-chemical characteristics. Metals Zn, Cu, Cr, and Ni appear in higher concentrations near to the margin of southern Porto Alegre, where there was also more clay plus silt. Sediments of Lake Guaíba have physical-chemical variability by the settle tendency and water flow from the riverine to lacustrine areas. The sediment in Lake Guaíba had a median of: Zn, 132; Cu, 78; Cr, 42; Ni, 28; Pb, 33; Cd, 0.3; and Hg, 0.07 μg/g. Bed sediments of Lake Guaíba are polluted with Zn, Cu, Cr, and Ni, major in the east margin (near to Porto Alegre). The potential toxic metals and organic compounds found in Lake Guaíba are commonly reported in urban regions around the world. Those elements and compounds derive from many anthropic activities, as industries, sewage, and vehicles. With diffuse sources in the region, the pollution control in Lake Guaíba is very complex.

First report of geochemical fractionation distribution, bioavailability and risk assessment of potentially toxic inorganic elements in sediments of coral reef Islands of the Persian Gulf, Iran

Metal contamination is a serious environmental concern in the Middle East. Herein, geochemical fractionation distribution and potential sources of thirteen metals (Fe, Al, Mn, Zn, Cu, Co, Cr, Ni, V, As, Hg, Pb and Cd) were investigated in sediments from ten coral reef Islands in the Persian Gulf, Iran. To properly assess availability and mobility of elements, enrichment factor (EF), pollution load index (PLI), pollution index (PI), contamination index (CI), sediment pollution index (SPI) and ecological risk assessment were provided. Sediment grain size showed an outstanding role in controlling the levels of potentially toxic inorganic elements (PTIEs). The highest values of total organic matter (TOM) were detected in Kharg and Lavan Islands. Different metals fractionation distribution was found across sites. As was noticed in carbonate (F₂), exchangeable (F₁), Fe-Mn oxy-hydroxide (F₃), organic (F₄) and residual (F₅) fractions, Hg primarily associated with F₂ and F₁, whereas Pb and Cd with F₂, followed by F₁, F₃, F₅ and F₄. Conversely, Ni and V accumulated in F₁, suggesting their high mobility and bioavailability, and thus environmental risk to aquatic biota. All metals (except Al, Fe and As) had geological and anthropogenic sources. Based on modified risk assessment analysis, the sediments from Kharg, Lavan, Siri and Lark Islands showed medium adverse effects. Overall, results from this study corroborate that petroleum industry is the main source of pollution of PTIEs in the Persian Gulf, and offer a scientific basis for monitoring and preventing metal pollution in the environment.