Heavy metal contamination and metallothionein mRNA in blood and feathers of Black-tailed gulls (Larus crassirostris) from South Korea

The objectives of this study were to determine levels of heavy metal in the feathers and blood of Black-tailed gulls (Larus crassirostris), to evaluate metallothionein (MT) mRNA level in Black-tailed gulls on three independent islets, and to examine the correlation between heavy metal concentrations and MT mRNA expression. Eleven heavy metals (Al, Cd, Mn, Pb, Cr, Fe, Cu, Zn, Se, Hg, and As) were investigated in blood and feathers of 65 chicks from breeding colonies (Seomando, Hongdo, and Dokdo islet) of South Korea in 2010. Heavy metals were assayed by PerkinElmer NexION 300 inductively coupled plasma mass spectrometry. The mean concentrations of non-essential heavy metals were found to blood containing Cd (0.002?~?0.02 ppm), Pb (0.06?~?0.18) ppm, Hg (0.03?~?0.05) ppm, and As (0.26?~?0.48 ppm), and feather containing Cd (0.05?~?0.30 ppm), Pb (2.47?~?10.80 ppm), Hg (1.18?~?1.57 ppm), and As (0.15?~?0.44 ppm). Chicks on Seomando islet showed the highest levels of metals (Cd, Pb, Mn, Cr, Cu, and Se in blood; Al, As, Mn, Cr, Fe, Cu, and Se in feathers) among the colonies. Concentrations of Pb and Hg in feathers were the highest on Hongdo, and the levels of Cd and Zn in feathers were the highest on Dokdo islet. MT mRNA in the blood of Black-tailed gulls was relatively higher in gulls from Seomando than in gulls from Hongdo and Dokdo islet. MT mRNA level is thus positively correlated to heavy metal concentrations in Black-tailed gulls.     

Assessment of heavy metal contamination in Candarli Gulf sediment, Eastern Aegean Sea

Concentrations of selected heavy metals (Fe, Mn, Ni, Cu, Zn, Pb, Hg, Cr, Al, and As) in surface sediments from 18 stations in the Candarli Gulf were studied in order to understand current metal contamination due to urbanization and economic development in Candarli region, Turkey. The sediment samples were collected by box corer in Candarli Gulf in 2009 to assess heavy metal pollution. Heavy metal concentrations in surface sediment varied from 1.62% to 3.60% for Fe, 0.38?C2.53% for Al, 173?C1,423 for Mn, 8?C100 for Ni, 3?C46 for Cu, 55?C119 for Zn, 16?C138 for Pb, 0.2?C6.3 for Hg, 16?C71 for Cr, and 11?C37 mg kg^???1 for As. This study showed that the concentrations of Mn, Ni, Zn, Pb, Hg, and Cr in the surface sediment layers were elevated when compared with the subsurface layers. Both metal enrichment and contamination factors show that Hg, Zn, and Pb contamination exists in the entire study area and contamination of other metals is also present in some locations depending on the sources.     

Spatial and temporal variability of metals in inter-tidal beach sediment of Mumbai, India

Nine metals were monitored in the beach sediment in Mumbai from May 2011 to March 2012 to evaluate the spatial and temporal distributions. The average heavy metal concentrations exhibited the following order: Fe > Mn > Cr > Co > Ni > Pb > Zn > Cu > Cd for the four sampling sites. The mean concentrations (± SD) of Fe, Mn, Cr, Co, Ni, Pb, Zn, Cu and Cd were estimated to be 31.15?±?10.02 g kg^?1, 535.04?±?76.42, 151.98?±?97.90, 92.76?±?14.18, 67.52?±?11.32, 59.57?±?15.19, 54.65?±?15.01, 32.24?±?8.07 and 18.75?±?1.76 mg kg^?1, respectively. The results indicated that the sediments were polluted with Cd, Cr, Co and Pb due to high anthropogenic influences. Spatial variation of metals revealed that most of the metals were high in Dadar beach and low in Aksa beach. Cd was the highest contaminant metal studied with a mean contamination factor of 93.75. The pollution load indices of the studied beaches ranged from 1.63 (Aksa) to 1.91 (Dadar) and indicated that the beach sediments were polluted with heavy metals. The heavy metal contents increased in relation to monsoon, and most of the heavy metals showed significantly high concentrations in November during the post-monsoon. The statistical analysis revealed significant effect of study site on all the metals studied. Further, there was a significant difference on metal accumulation on bimonthly basis in relation to weather pattern in Mumbai beaches.     

Vertical distribution of heavy metals in soil profile in a seasonally waterlogging agriculture field in Eastern Ganges Basin

The accumulation of heavy metals in soil and water is a serious concern due to their persistence and toxicity. This study investigated the vertical distribution of heavy metals, possible sources and their relation with soil texture in a soil profile from seasonally waterlogged agriculture fields of Eastern Ganges basin. Fifteen samples were collected at ～0.90-m interval during drilling of 13.11 mbgl and analysed for physical parameters (moisture content and grain size parameters: sand, silt, clay ratio) and heavy metals (Fe, Mn, Cr, Cu, Pb, Zn, Co, Ni and Cd). The average metal content was in the decreasing order of Fe?>?Mn?>?Cr?>?Zn?>?Ni?>?Cu?>?Co?>?Pb?>?Cd. Vertical distribution of Fe, Mn, Zn and Ni shows more or less similar trends, and clay zone records high concentration of heavy metals. The enrichment of heavy metals in clay zone with alkaline pH strongly implies that the heavy metal distributions in the study site are effectively regulated by soil texture and reductive dissolution of Fe and Mn oxy-hydroxides. Correlation coefficient analysis indicates that most of the metals correlate with Fe, Mn and soil texture (clay and silt). Soil quality assessment was carried out using geoaccumulation index (I _geo), enrichment factor (EF) and contamination factor (CF). The enrichment factor values were ranged between 0.66 (Mn) and 2.34 (Co) for the studied metals, and the contamination factor values varied between 0.79 (Mn) and 2.55 (Co). Results suggest that the elements such as Cu and Co are categorized as moderate to moderately severe contamination, which are further confirmed by I _geo values (0.69 for Cu and 0.78 for Co). The concentration of Ni exceeded the effects-range median values, and the biological adverse effect of this metal is 87 %. The average concentration of heavy metals was compared with published data such as concentration of heavy metals in Ganga River sediments, Ganga Delta sediments and upper continental crust (UCC), which apparently revealed that heavy metals such as Fe, Mn, Cr, Pb, Zn and Cd are influenced by the dynamic nature of flood plain deposits. Agricultural practice and domestic sewage are also influenced on the heavy metal content in the study area.     

Irrigational impact of distillery effluent on Abelmoschus esculentus L. Okra with special reference to heavy metals

The present study was performed under natural environment to assess levels of different heavy metals in soil and Abelmoschus esculentus plants along with soil microbial population irrigated with five rates of distillery effluent (DE) viz. 10, 25, 50, 75 and 100 % concentration in comparison with control (Bore well water). Results revealed that among various concentrations of DE, irrigation with 100 % DE significantly (P < 0.001) increased Zn (+63.46 %), Cu (+292.37 %), Zn (+3763.63 %), Cd (+264.29 %), Ni (+48.39 %) and Cr (+815.74 %), while decreased total bacteria (?45.23 %), fungi (?17.77 %) and actinomycetes (?42.57 %) in the soil. Enrichment factor of various heavy metals for soil was in the order Ni > Cr > Cd > Zn > Cu, and for A. esculentus plants, it was in the order Ni > Cr > Cu > Cd > Zn after irrigation with distillery effluent. The enrichment factor value was found maximum for Ni in comparison to other metals at 100 % DE concentration as compared with BWW. However, the values of these metals were below the recommended permissible limit.     

Pollution in the urban soils of Lianyungang,China, evaluated using a pollution index,mobility of heavy metals,and enzymatic activities

Soil samples from 16 urban sites in Lianyungang, China were collected and analyzed. A pollution index was used to assess the potential ecological risk of heavy metals and a sequential extraction procedure was used to evaluate the relative distribution of Cu, Zn, Pb, Cd, Cr, and As in exchangeable, carbonate, Fe/Mn oxide, organic/sulfide, and residual fractions. The mobility of heavy metals and urease (URE) activity, alkaline phosphatase (ALP) activity, and invertase (INV) activity of soils was determined. The results showed that the average concentrations of Cu, Zn, Pb, Cd, Cr, and As in Lianyungang soils were much higher than those in the coastal city soil background values of Jiangsu and China. Among the five studied regions (utilities, commercial, industrial, tourism, and roadside), the industrial region had the highest metal concentrations demonstrating that land use had a significant impact on the accumulation of heavy metals in Lianyungang soils. Compared to the other metals, Cd showed the highest ecological risk. According to chemical partitioning, Cu was associated with the organic/sulfides and Pb and Zn were mainly in the carbonate and the Fe/Mn oxide phase. The greatest amounts of Cd were found in exchangeable and carbonate fractions, while Cr and As were mainly in the residual fraction. Cd had the highest mobility of all metals, and the order of mobility (highest to lowest) of heavy metals in Lianyungang soils was Cd > Zn > Pb > Cu > As > Cr. Soil urease activity, alkaline phosphatase activity, and invertase activity varied considerably in different pollution degree sites. Soil enzyme activities had the lowest levels in roadside and industrial regions. Across all the soil data in the five regions, the total Cu, Zn, Pb, Cd, Cr, and As level was negatively correlated with urease activity, alkaline phosphatase activity, and invertase activity, but the relationship was not significant. In the industrial region, alkaline phosphatase activity had significant negative correlations with total Cu, Pb, Cr, Zn, Cd, and heavy metal fractions. This showed that alkaline phosphatase activity was sensitive to heavy metals in heavily contaminated regions, whereas urease and invertase were less affected. The combination of the various methods may offer a powerful analytical technique in the study of heavy metal pollution in street soil.     

Distribution and chemical partitioning of heavy metals in marine near-shore sediment cores: a case study from the Xugou, Lianyungang, China

The concentrations and chemical partitioning of heavy metals (Co, Cr, Ni, Zn, Cu, and Pb) in the marine near-shore sediment cores were investigated. Typically, the mean concentrations from Core B sediment samples were 98.6, 21.1, 47.0, 46.4, 107.6, and 31.9 mg kg^???1 for Cr, Co, Ni, Cu, Zn, and Pb, respectively. The heavy metal concentrations were normalized to commonly used reference elements Al, Li, Sc, and total organic carbon. Based on Pearson coefficients, Li was found to be a good normalizer for Co (r?= 0.974), Cr (r?= 0.967), Ni (r?= 0.898), and Zn (r?= 0.929) in 80 sediment samples from three sampling sites. However, the correlation coefficients between Li and Cu, and Li and Pb were relatively low. Multivariate statistic approaches (Principal Component Analysis and Cluster Analysis) were adopted for data treatment, allowing the identification of two main factors controlling the heavy metal variability in the sediments. Heavy metals in the enrichment sections were evaluated by a sequential extraction method for possible chemical forms in sediments. The results showed that the residual, Fe/Mn oxides and Organic/sulfide fractions were dominant geochemical phases in the enriched sections, indicating low bioavailability of heavy metals in sediments.     

Levels of some toxic elements and frequency of bacterial heavy metal resistance in sediment and sea water

The Golden Horn Estuary located in the Istanbul region of Turkey has been thought to be a heavily polluted area since the 1950s: the concentration of the elements, which include heavy metals such as Cu2+, Mn2+, Ni2+, Zn2+, Pb2+, Cd2+, and Fe2+, was therefore investigated in sediment and water samples of the area. The resistance of Enterobacteriaceae members to some heavy metal salts was investigated to determine levels of metal-resistant bacteria in the Golden Horn Estuary after the environmental restoration project in 1998. The sediment samples were collected with an Ekman-Grab in the period from November 2002 to February 2004 from depths of 4-15 m and analyzed by means of an atomic absorption spectrophotometer. Analyses of average heavy metals of sediment samples yielded the following results: 131.5 ppm Cu, 405.5 ppm Mn, 46.5 ppm Ni, 191.2 ppm Zn, 81.5 ppm Pb and 27668 ppm Fe. As with water, Ni concentrations in sediment were found lower than that in limit values. Frequency of heavy metals resistance to Cu, Zn, Fe, Ni, Mn, Pb and Cd was detected as an average of 65.0%, 64.4%, 62.5%, 38.4%, 37.3%, 36.2% and 28.4%, respectively in a total of 192 strains isolated from sediment samples. It was observed that there was no statistically significant difference among the results of analyses with respect to sampling dates. Despite the environmental restoration project in 1998, our study results showed that heavy metal levels were still high in the sediment and this situation induced the tolerance of bacteria to some heavy metals.     

Spatial Characterization and Prioritization of Heavy Metal Contaminated Soil-Water Resources in Peri-Urban Areas of National Capital Territory (NCT), Delhi

Due to rapid industrialization and urbanization during last two decades, contamination of soils by heavy metals is on an increase globally. Lands under peri-urban agriculture are the worst affected. In NCT, Delhi about 14.4% of land area is chemically degraded. In order to take care of this problem, recently the Supreme Court of India ordered to shift various non-confirming (about 39,000 units) industries to regions outside NCT, Delhi. However in spite of this, there have been several reports and parliamentary debates on the phyto-toxicity and extensive accumulation of heavy metals in the region. Literature review revealed that the basis of these debates is a few studies on some point locations in/around Delhi. It was further observed that information on the distribution and extent of heavy metal pollution problem in the region was completely missing. The present study was thus basically aimed at assessing the spatial distribution/extent and type of heavy metal pollution in the study area, for enabling future designing of appropriate site-specific management measures by the decision makers.For this, detailed spatial information on bio-available heavy metal concentrations in the soils and surface/sub-surface waters of NCT (Delhi) was generated through actual soil/water surveys, standard laboratory methods and GIS techniques. The study showed that concentration of all micronutrients (viz. Zn: 0.05–0.18 ppm; Cu: in traces; Fe: 0–0.5 ppm; and Mn: 0–1.2 ppm) and most heavy metals (viz. Ni: 0–0.7 ppm; Pb: 0–0.15 ppm and Cd: in traces) in the surface/sub-surface irrigation waters were well within permissible limits. However Cr concentrations in irrigation waters of Alipur and Shahdara blocks were far above their maximum permissible limit of 1 ppm. It was further observed that Ni and Cr concentrations in the drinking waters of almost entire test area were far above maximum permissible levels of 0.02 and 0.01 ppm, respectively. Bio-available concentrations of several heavy metals (viz. Pb: 0.1–2 ppm; Cd: traces; Ni: 0.05–2 ppm and Cr: 0–0.4 ppm) in the study area soils were also observed to be well within the maximum permissible limits. However there were point Cu contaminations (5–10 ppm) in the sewage-sludge amended soils of vegetable growing areas near south Shahdara block. This was attributed to increased Cu availability due to oxidized acidic conditions generated by over-irrigation of agricultural lands. Available Mn concentrations in Kanjhawala, western Najafgarh and Alipur soils were also observed to be above maximum permissible limit of 10 ppm. This was observed to be mainly due to the geology (i.e. presence of Mn rich sedimentary rocks) and prevalence of reduced acidic conditions, due to paddy cultivation, in these areas. It was further observed that there is acute zinc (Zn) deficiency (< 0.6 ppm) in paddy growing soils of north Kanjhawala, Alipur and some parts of Najafgarh and Shahdara blocks due to extensive leaching of available Zn fractions to lower soil horizons. Similar available Zn deficiencies in high pH (8.5) soils of areas around Bamnoli village in E-Najafgarh block were also observed.     

Competitive sorption of Cd, Cu, Mn, Ni, Pb and Zn in polluted and unpolluted calcareous soils

The objectives of this study were to investigate competitive sorption behaviour of heavy metals (Cd, Cu, Mn, Ni, Pb and Zn) under different management practices and identify soil characteristics that can be correlated with the retention and mobility of heavy metals using 65 calcareous soil samples. The lowest sorption was found for Mn and Ni in competition with the other metals, indicating the high mobility of these two cations. The Freundlich equation adequately described heavy metals adsorption. On the basis of Freundlich distribution coefficient, the selectivity sequence of the metal adsorption was Cu?>?Pb?>?Cd?>?Zn?>?Ni?>?Mn. The mean value of the joint distribution coefficient (K _dΣsp) was 182.1, 364.1, 414.7, 250.1, 277.7, 459.9 and 344.8 l kg^?1 for garden, garlic, pasture, potato, vegetables, wheat and polluted soils, respectively. The lowest observed K _dΣsp in garden soil samples was due to the lower cation exchange capacity and lower carbonate content. The results of the geochemical modelling under low and high metal addition indicated that Cd, Ni, Mn and Zn were mainly retained via adsorption, while Pb and Cu were retained via adsorption and precipitation. Stepwise forward regression analysis showed that clay, organic matter and CaCO₃ were the most important soil properties influencing competitive adsorption of Cd, Mn, Ni and Zn. The results in this study point to a relatively easy way to estimate distribution coefficient values.     

渭河陕西段表层沉积物重金属污染特征及潜在风险

为了解渭河陕西段表层沉积物重金属的污染特征,采用ICP-MS分析了13个采样断面表层沉积物中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn 8种重金属的含量,并对其来源和生态风险进行了评价。结果表明：渭河陕西段8种重金属的平均含量顺序依次为Mn > Zn > Cr > Cu > Ni > Pb > As > Cd;除Ni外的其余7种重金属的平均含量均超过陕西省A层土壤背景值。各断面表层沉积物重金属的潜在生态风险指数（RI）介于111.4~7 043.7,其中23.1%的断面有极强生态风险,46.2%的断面为中等生态风险,其余为轻微生态风险。Cd污染最为严重,对各断面的潜在生态风险介于较强生态风险与极强生态风险之间,对RI的贡献平均为85.2%;其余7种重金属在所有断面均属于轻微生态危害。渭河陕西段表层沉积物As、Cd、Cu和Zn主要为工业与农业来源;Cr和Ni主要为自然来源;Pb和Mn与城市污水和交通污染来源有关。     

Fractionation of heavy metals and assessment of contamination of the sediments of Lake Titicaca

Chemical weathering is one of the major geochemical processes that control the mobilization of heavy metals. The present study provides the first report on heavy metal fractionation in sediments (8–156 m) of Lake Titicaca (3,820 m a.s.l.), which is shared by the Republic of Peru and the Plurinational State of Bolivia. Both contents of total Cu, Fe, Ni, Co, Mn, Cd, Pb, and Zn and also the fractionation of these heavy metals associated with four different fractions have been determined following the BCR scheme. The principal component analysis suggests that Co, Ni, and Cd can be attributed to natural sources related to the mineralized geological formations. Moreover, the sources of Cu, Fe, and Mn are effluents and wastes generated from mining activities, while Pb and Zn also suggest that their common source is associated to mining activities. According to the Risk Assessment Code, there is a moderate to high risk related to Zn, Pb, Cd, Mn, Co, and Ni mobilization and/or remobilization from the bottom sediment to the water column. Furthermore, the Geoaccumulation Index and the Enrichment Factor reveal that Zn, Pb, and Cd are enriched in the sediments. The results suggest that the effluents from various traditional mining waste sites in both countries are the main source of heavy metal contamination in the sediments of Lake Titicaca.     

Enhanced uptake of heavy metals in municipal solid waste compost by turfgrass following the application of EDTA

Enhancement of multiple heavy metal uptake from municipal solid waste (MSW) compost by Lolium perenne L. in a field experiment was investigated with application of EDTA. EDTA was added in solution at six rates (0–30 mmol kg^???1) after 50 days of plant growth. Two weeks later, plants were harvested for the first crop and then all the turfgrasses were mowed. After another 30 days of growth, EDTA was added again at above six rates to the corresponding sites and the second crop was harvested 2 weeks later. The results showed that EDTA significantly increased heavy metal accumulation in both crops of L. perenne. For the first crop, the concentrations of Mn, Ni, Cd, and Pb in the shoots increased remarkably with increasing EDTA supply, peaked at 25 mmol kg^???1 EDTA, and shoots of 0–5 cm height (shoots from medium surface to 5 cm height) had higher metal concentrations than 5–10 cm and >10 cm shoots. The highest concentration of Mn, Ni, Cd, and Pb was 2.3-, 2.3-, 2.6-, and 3.2-fold, respectively, in 0–5 cm shoots higher than control. For the second crop, the concentrations of Mn, Cu, and Pb in shoots were, in general, less than those in the first crop. However, the second crop was significantly higher (P?< 0.05) than the first crop in dry biomass, so the total amount of metals removed by the second crop was more than the first crop. In addition, EDTA significantly increased the translocation ratios of most heavy metals from roots to shoots. For the first crop, 38% of the total Zn, 51% of Cd, 49% of Pb, 60% Mn, 55% Ni, and 45% Cu taken up by the plant was translocated in the shoots of 0–5 cm height. Turfgrass would have potential for use in remediation of heavy metals in MSW compost or contaminated soils.     

Speciation and assessment of heavy metals in surface sediments of Jinjiang River tidal reach, southeast of China

The concentration and speciation of heavy metals (Cr, Ni, Cu, Zn, Cd, Pb) in surface sediments (??≤ 63 μm) of Jinjiang River tidal reach are determined to evaluate the metal behavior. A modified BCR three-step sequential extraction procedure is carried out, and the residual fraction is undertaken by microwave-assisted acid digestion. The index of geo-accumulation indicates that Cd appeared highest among all these heavy metals in surface sediments, Cr, Cu, Zn lower, and Ni, Pb the least. The percentage of Zn, Cd is comparatively higher in the acid soluble fraction, Pb and Cu higher in the reductive fraction, indicating larger potential danger to the environment. So it is essential for developing the future remediation plans and pollution control strategies.     

Environmentally safe sewage sludge disposal: the impact of liming on the behaviour of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn

Dewatered sewage sludge containing relatively high total concentrations of Cr (945 micrograms ml-1), Cu (523 micrograms ml-1), Ni (1186 micrograms ml-1) and Zn (2950 micrograms ml-1) was treated with quicklime and sawdust for sludge disinfection and post-stabilisation. The mobility of the heavy metals in the sludge samples was assessed by applying a modified five-step Tessier sequential extraction procedure. Water was added as a first step for estimation of the proportion of the easily soluble metal fractions. To check the precision of the analytical work the concentrations of heavy metals in steps 1-6 of the extraction procedure were summed and compared to the total metal concentrations. The mass balance agreed within +/- 3% for Cd, Cu, Cr, and Zn and within +/- 5% for Ni, Pb, Fe and Mn. Data from the partitioning study indicate that in the lime-treated sludge at a pH of 12 the mobility of Cu and Ni notably increased with the solubilisation of these metals from their organic and/or carbonate and Fe and Mn oxide and hydroxide fractions, respectively. Liming slightly decreased the proportion of other heavy metals in the easily soluble fractions while its impact on the partitioning between other sludge phases was almost insignificant. Due to the increased solubility of Ni and Cu as well as potential Cr oxidation at high pH, liming cannot be recommended for sludge disinfection. Addition of sawdust did not change the heavy metal partitioning.     

Contamination assessment of arsenic and heavy metals in a typical abandoned estuary wetland—a case study of the Yellow River Delta Natural Reserve

Coastal and estuarine areas are often polluted by heavy metals that result from industrial production and agricultural activities. In this study, we investigated the concentration trait and vertical pattern of trace elements, such as As, Cd, Ni, Zn, Pb, Cu, and Cr, and the relationship between those trace elements and the soil properties in coastal wetlands using 28 profiles that were surveyed across the Diaokouhe Nature Reserve (DKHNR). The goal of this study is to investigate profile distribution characteristics of heavy metals in different wetland types and their variations with the soil depth to assess heavy metal pollution using pollution indices and to identify the pollution sources using multivariate analysis and sediment quality guidelines. Principal component analysis, cluster analysis, and pollution level indices were applied to evaluate the contamination conditions due to wetland degradation. The findings indicated that the concentration of trace elements decreased with the soil depth, while Cd increases with soil depth. The As concentrations in reed swamps and Suaeda heteroptera surface layers were slightly higher than those in other land use types. All six heavy metals, i.e., Ni, Cu, As, Zn, Cr, and Pb, were strongly associated with PC1 (positive loading) and could reflect the contribution of natural geological sources of metals into the coastal sediments. PC2 is highly associated with Cd and could represent anthropogenic sources of metal pollution. Most of the heavy metals exhibited significant positive correlations with total concentrations; however, no significant correlations were observed between them and the soil salt and soil organic carbon. Soil organic carbon exhibited a positive linear relationship with Cu, Pb, and Zn in the first soil layer (0–20 cm); As, Cr, Cu, Ni, Pb, and Zn in the second layer (20–40 cm); and As, Cr, Cu, Ni, Pb, and Zn in the third layer (40–60 cm). Soil organic carbon exhibited only a negative correlation with Cd (P?I _geo values), which averaged less than 0 in the three soil layers, this finding indicates that the soils have remained unpolluted by these heavy metals. The mean concentrations of these trace elements were lower than Class I criteria. The degradation wetland restoration suggestions have also been provided in such a way as to restore the reserved flow path of the Yellow River. The results that are associated with trace element contamination would be helpful in providing scientific directions to restore wetlands across the world.     

Metal pollution and ecological risk assessment in marine sediments of Karachi Coast, Pakistan

Concentrations of 12 metals (Fe, Mn, Cr, Mo, Ni, Pb, Se, Sr, U, V, Zn, and Zr) in surface sediments of Karachi Coast, Pakistan were determined to evaluate their distribution and pollution assessment. The measured metals in the sediments were found to be in the range of Fe, 0.84–6.96 %; Mn, 300–1,300 μg/g; Cr, 12.0–319.84 μg/g; Mo, 0.49–2.03 μg/g; Ni, 1.53–58.86 μg/g; Pb, 9.0–49.46 μg/g; Se, 0.25–.86 μg/g; Sr, 192–1185 μg/g; U, 0.19–1.66 μg/g; V, 15.80–118.20 μg/g; Zn, 15.60–666.28 μg/g; and Zr, 44.02–175.26 μg/g. The mean contents of the metal studied were: Fe, 3.07 %, Mn, 0.05 %; Cr, 96.75 μg/g; Mo, 1.34 μg/g; Ni, 31.39 μg/g; Pb, 23.24 μg/g; Se, 0.61 μg/g; Sr, 374.83 μg/g; U, 0.64 μg/g; V, 61.75 μg/g; Zn, 204.75 μg/g; and Zr:76.27 μg/g, and arrangement of the metals from higher to lower mean content in this area is: Fe?>?Zn?>?Mn?>?Sr?>?Zn?>?Cr?>?Zr?>?V?>?Ni?>?Pb?>?Mo?>?U?>?Se. There is no significant correlation among most of these metals, indicating different anthropogenic and natural sources. To assess ecotoxic potential of marine sediments, Numerical Sediment Quality Guidelines were also applied. The concentration of Pb in all the sediments except one was lower than the threshold effect concentration (TECs) showing that there are no harmful effects to marine life from Pb. On the other hand, the concentrations of Cr, Ni, and Zn exceeded TEC in three stations, indicating their potential risk. The degree of pollution in sediments for metals was assessed by calculating enrichment factor (EF) and pollution load index (PLI). The results indicated that sediments of Layari River Mouth Area, Fish Harbour, and KPT Boat Building Area are highly enriched with Cr and Zn (EF?>?5). Sediments of Layari River Outfall Zone were moderately enriched with Ni and Pb (EF?>?2). The pollution load index was found in the range of 0.98 to 1.34. Lower values of PLI (≤1) at most of sampling locations imply no appreciable input from anthropogenic sources. However, relatively higher PLI values (>1) at Layari River Mouth Area, Fish Harbour, and KPT Boat Building Area are attributed to increased human activity in the area.     

Speciation and ecological risk of heavy metals in intertidal sediments of Quanzhou Bay, China

The chemical speciation of nine heavy metals in intertidal sediments from Quanzhou Bay was determined using a modified sequential extraction procedure, proposed by the Commission of the European Community Bureau of Reference. The results show that Mn presents the highest percentage in the acid-soluble fraction, and Pb and Cu present the highest percentages in the reducible fraction. The highest percentages of Fe, V, Cr, Ni, Zn, and Co were found in the residual fraction. The mobility order of the heavy metals studied on the basis of the nonresidual content of the elements is Mn > Pb > Cu > Co > Zn > Ni > Cr > V > Fe. The assessment on potential ecological risk indices of some heavy metals indicates that Zn, Ni, and Cr show moderate contamination, while Cu and Pb show slighter contamination. On the whole, the comprehensive potential ecological risk index of Cu, Zn, Ni, Cr, and Pb in the sediments presents moderate degree.     

Total and available heavy metal concentrations in soils of the Thriassio plain (Greece) and assessment of soil pollution indexes

The Thriassio plain is located 25 km west of Athens city, the capital of Greece. Two major towns (Elefsina and Aspropyrgos), heavy industry plants, medium to large-scale manufacturing, logistics plants, and agriculture comprise the main land uses of the studied area. The aim of the present study was to measure the total and available concentrations of Cr, Zn, Ni, Pb, Co, Mn, Ba, Cu, and Fe in the top soils of the plain, and to asses soil contamination by these metals by using the geoaccumulation index (I _geo), the enrichment factor (EF), and the availability ratio (AR) as soil pollution indexes. Soil samples were collected from 90 sampling sites, and aqua regia and DTPA extractions were carried out to determine total and available metal forms, respectively. Median total Cr, Zn, Ni, Pb, Co, Mn, Ba, Cu, and Fe concentrations were 78, 155, 81, 112, 24, 321, 834, 38, and 16?×?10³ mg?kg^?1, respectively. The available fractions showed much lower values with medians of 0.4, 5.6, 1.7, 6.9, 0.8, 5.7, 19.8, 2.1, and 2.9 mg?kg^?1. Though median total metal concentrations are not considered as particularly high, the I _geo and the EF values indicate moderate to heavy soil enrichment. For certain metals such as Cr, Ni, Cu, and Ba, the different distribution patterns between the EFs and the ARs suggest different origin of the total and the available metal forms. The evaluation of the EF and AR data sets for the soils of the two towns further supports the argument that the EFs can well demonstrate the long-term history of soil pollution and that the ARs can adequately portray the recent history of soil pollution.     

Spatial distribution and risk assessment of heavy metals in sediments from a hypertrophic plateau lake Dianchi, China

The sediment in Dianchi Lake, a hypereutrophic plateau lake in southwest China, was investigated and the concentration of heavy metals (Cu, Cr, Ni, Zn, Pb, Fe, Mn, and Cd) in the sediment and sediment properties were determined. Their spatial distribution and sources were analyzed using multivariate statistics. The result indicated that the studied metals exhibited three distinct spatial patterns; that is, Cu, Pb, Zn, and Ni had a similar distribution, with a concentration gradient from the north to the south part of the lake; Cd and Cr presented a similar distribution; Fe and Mn presented a quite different distribution than other metals, which indicated their different sources and geochemistry processes. Correlation and cluster analysis (CA) provided origin information on these metals and the CA result was observed corresponding to those three spatial patterns. Principal component analysis further displayed metal source and driving factors; that is, Cu, Pb, Zn, Ni, Cd, and Cr were mainly derived from anthropogenic sources, and Fe and Mn were mainly the result of natural processes. Sediment assessment was conducted using geoaccumulation index (Igeo), potential ecological risk indices, and USEPA guidelines. The result indicated that, generally, Cd was the most serious risk metal; Pb and Cu posed moderate potential ecological risk; Cr, Zn, and Ni had slight ecological risk; Fe and Mn had little risk. Comparison of the assessment tools showed that each of the methods had its limitation and could bias the result, and the combined use of the methodologies and local knowledge on lithology or metal background value of soil in the practice would give a more comprehensive understanding of the metal risk or pollution. Statistical analysis also indicated that nutrients had different impacts on Fe, Mn, and trace elements, which implied that in the assessment of metal risk, nutrients impact should be taken into consideration especially for eutrophic waters.