Multivariate Statistical Analysis and Risk Assessment of Heavy Metals Monitored in Surface Sediment of the Luan River and its Tributaries,China

In this study, a total of 84 sites in the Luan River Basin of China and its tributaries were monitored in 2012 for seven heavy metals (Cu, Ni, Pb, Zn, Cd, Cr, Hg) in the surface sediments. Cluster analysis (CA), principal component analysis (PCA), correlation analysis, and pollution indices were applied to the interpretation of the monitoring results. The results show that: (1) sampling sites in the mainstream are classified into two groups, upstream and downstream, with downstream representing higher levels of heavy metals and degrees of pollution; (2) three clusters were identified for the 10 tributaries, the downstream having the highest levels of heavy metals’ pollution; (3) the PCA suggests there are significant correlations among Zn, Cu, and Pb between Cr in the basin. Sediment pollution assessment was carried out using Pollution Index (PI) and Geo-Accumulation Index (I_geo). Mercury was the metal with the highest contamination level, followed by Cd and Cr. The results provide an overview of the current status of sediment contamination with measured data and support future policy development for the protection of water quality in the Luan River Basin.     

Phytoremediation of Heavy Metals in Contaminated Water and Soil Using Miscanthus sp. Goedae-Uksae 1

The aim of this study is to characterize the heavy metal phytoremediation potential of Miscanthus sp. Goedae-Uksae 1, a hybrid, perennial, bio-energy crop developed in South Korea. Six different metals (As, Cu, Pb, Ni, Cd, and Zn) were used for the study. The hybrid grass effectively absorbed all the metals from contaminated soil. The maximum removal was observed for As (97.7%), and minimum removal was observed for Zn (42.9%). Similarly, Goedae-Uksae 1 absorbed all the metals from contaminated water except As. Cd, Pb, and Zn were completely (100%) removed from contaminated water samples. Generally, the concentration of metals in roots was several folds higher than in shoots. Initial concentration of metals highly influenced the phytoremediation rate. The results of the bioconcentration factor, translocation factor, and enrichment coefficient tests indicate that Goedae-Uksae 1 could be used for phytoremediation in a marginally contaminated ecosystem.     

Accumulation of Heavy Metals in Potatoes Grown on Calcareous Soils of the Hamedan,Western Iran

This study was conducted to investigate heavy metal contamination in agricultural soils and their transfer in a soil-potato system. A total of 59 pairs of potato and soil samples, representing different locations were collected from Hamedan, western Iran and subjected to heavy metals analysis. Average concentrations of Cd, Cu, Fe, Mn, Ni, Pb, and Zn were 1.2, 13.1, 161.4, 13.2, 3.2, 19.5, and 41.5 mg kg^?1 dry weight in potato tubers, respectively. A sequence of decreasing plant transfer factors values: Cd > Pb > Cu > Zn > Ni ≥ Mn > Fe was obtained. Furthermore, the health risk index (HRI) values were within the safe limit (<1) except for Cd and Pb. HRI values for Cd and Pb were higher than 1, indicating potential health risk, especially for children. The results indicated that daily intakes of Cd and Pb in potato in the study area may present a future hazard.     

Assessment of Heavy Metal Contamination in the Sediments of the Shuangtaizi Estuary Using Multivariate Statistical Techniques

In order to assess heavy metal pollution of sediment samples collected from Shuangtaizi estuary, contamination factor (CF) and multivariate statistical analyses, including principal component analysis (PCA), cluster analysis (CA) and correlation analysis, are carried out in this paper. CF confirms that Pb, Cu and Hg concentrations are very low and all fall within the range of background, while Zn and Cd demonstrate moderate contamination (in A10, A13, A15, A16 and A17 sites) and very high contamination (in A10, A13, A15 and A17 sites), respectively. The PCA indicates that four significant principal components (PCs) are extracted, explaining 88.959% of total variance, which suggests that Pb, Cu and Zn are mainly associated with organic carbon (OC). The result from CA is consistent with that obtained from PCA, classifying that the heavy metals in two clusters derive from different sources. Correlation analysis supports the conclusions from PCA and CA, elucidating the relationships between heavy metals and particle sizes of the sediments.     

Pollution Assessment and Potential Sources of Heavy Metals in Agricultural Soils around Four Pb/Zn Mines of Shaoguan City,China

A total of 455 agricultural soil samples from four nonferrous mines/smelting sites in Shaoguan City, China, were investigated for concentrations of 10 heavy metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, and Zn). The mean concentrations of the metals were 72.4, 5.16, 13.3, 54.8, 84.5, 1.52, 425, 28.2, 529, and 722 mg kg^?1, respectively. The values for As, Cd, Hg, Pb, and Zn were more than 8 and 1.5 times higher than their background values in this region and the limit values of Grade II soil quality standard in China, respectively. Estimated ecological risks based on contamination factors and potential ecological risk factors were also high or very high for As, Cd, Hg, and Pb. Multivariate analysis (Pearson's correlation analysis, hierarchical cluster analysis, and principal component analysis) strongly implied three distinct groups; i.e., As/Cu/Hg/Zn, Co/Cr/Mn/Ni, and Cd/Pb. Local anomalies for As, Cu, Hg, and Zn by a probably anthropogenic source (identified as mining activity), Co, Cr, Mn, and Ni by natural contribution, and a mixed source for Cd and Pb, were identified. This is one of the few studies with a focus on potential sources of heavy metals in agricultural topsoil around mining/smelting sites, providing evidence for establishing priorities in the reduction of ecological risks posed by heavy metals in Southern China and elsewhere.     

Assessment of Pollution-Induced Microbial Community Tolerance to Heavy Metals in Soil Using Ammonia-Oxidizing Bacteria and Biolog Assay

This study attempted to investigate if the tolerance of soil bacterial communities in general, and autotrophic ammonia-oxidizing bacteria (AOB) in particular, evolved as a result of prolonged exposure to metals, and could be used as an indigenous bioindicator for soil metal pollution. A soil contaminated with copper, chromium, and arsenic (CCA) was mixed with an uncontaminated garden soil (GS3) to make five test soils with different metal concentrations. A modified potential ammonium oxidation assay was used to determine the metal tolerance of the AOB community. Tolerance to Cr, Cu, and As was tested at the beginning and after up to 13 months of incubation. Compared with the reference GS3 soil, the five CCA soils showed significantly higher tolerance to Cr no matter which form of Cr (Cr³⁺, CrO₄ ^2?, or Cr₂O₇ ^2?) was tested, and the Cr tolerance correlated with the total soil Cr concentration. However, the tolerance to Cu²⁺, As³⁺, and As⁵⁺ did not differ significantly between the GS3 soil and the five CCA soils. Community level physiological profiles using Biolog microtiter plates were also used to examine the chromate tolerance of the bacterial communities extracted after six months of exposure. Our results showed that the bacterial community tolerance was altered and increased as the soil Cr concentration was increased, indicating that the culturable microbial community and the AOB community responded in a similar manner.     

Spatial Assessment of Heavy Metals in Surface Soil from Klang District (Malaysia): An Example from a Tropical Environment

Heavy metals (Al, Cd, Co, Cr, Cu, Fe, Pb, Zn) in surface soil of Klang district were determined and multivariate analysis was used to understand their potential sources. The total and bioavailability of concentrations were used in identifying the potential risks to the ecology and human health. The means for the total heavy metal concentrations were found to be in the order of Fe > Al > Zn > Pb > Cu > Cr > Co > Cd, while the means for the bioavailability concentrations were found to be in the order of Al > Fe > Zn > Cu > Co > Cd > Pb > Cr. Principal Component Analysis showed Principal Component 1 as being of natural origin whereas Principal Components 2, 3, and 4 were associated with mixed anthropogenic sources, such as traffic and industrial emissions, organic matter, and granulometric fractions. Potential ecological risk assessment indicated an overall low ecological risk. Spatial assessment of non-carcinogenic risks showed that the Hazard Index values were more than one in Johan Setia, due to biomass burning of peat swamps exploited for agricultural development. While for spatial assessment of carcinogenic risks, the Lifetime Cancer Risk values were in the limit (1 × 10^?5), indicating low cancer inducing risks. Nevertheless, with intense development pressure in the Klang district could overlap pollution inputs in the future.     

Characterization of Heavy Metals in Soil by High Gradient Magnetic Separation

In recent years forecasting soil cleaning efficiencies of polluted soil, especially those contaminated with heavy metals, has become an important issue. Failure of the methods to predict the right efficiency has resulted in financial losses and penalties. This article describes an addition to the traditional characterization methods for soils contaminated by heavy metals, improving the quality of the basic decisions to be made. The method is based on magnetic separation using a Frantz Isodynamic Separator (FIS) for this study. The FIS isolates soil particles containing heavy metals so that these particles, which are relevant for soil cleaning, can be studied in more detail. Four contaminated soils were tested, for example, soils that were a problem for the soil-cleaning industry. The experiments indicate that each soil has its own magnetic properties that should be regarded as a fingerprint. Density measurements of two soils show that densities approach the quartz density separated at moderate and high magnetic fields suggesting that some of the heavy metals cannot be removed by density separation techniques. A pilot plant scale test supports this conclusion. It also shows that a part of the heavy metals are found in particles lighter than quartz. Based on the results, a qualitative model is proposed to account for the presence of the heavy metals in soil.     

Heavy Metals and Trace Element Concentrations in Intertidal Soils of Four Estuaries of SW Iberian Peninsula

Soils from four estuaries of SW Iberian Peninsula, affected by anthropogenic influence (urban, industrial and agricultural activities), were analyzed for the occurrence of a variety of metals and trace elements including Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S and Zn. The soils presented very high levels of salinity (high concentrations of Na, K and Mg), organic matter and, consequently, of C and N concentrations. In contrast, very low values of CaCO₃, Ca and P were found. In addition, it should be highlighted that in certain localities (Piedras 1 and 2 and Guadiana in Huelva, Spain, and Ria Formosa, Faro, Portugal) the concentrations of Pb, S and Zn were extremely high, reaching levels of pollution.     

Spatial Distribution and Uncertainty Assessment of Potential Ecological Risks of Heavy Metals in Soil Using Sequential Gaussian Simulation

The objective of this study is to assess the spatial distribution and uncertainty of the potential ecological risks of heavy metals in soil using sequential Gaussian simulation (SGS) and the Hakanson potential ecological risk index (PERI). We collected 130 soil samples in an area of 150 km² in the High-Tech Park of Wuhan, China, and measured the concentrations of five heavy metals in soil (i.e., Cd, Cr, Cu, Pb, and Zn). We then simulated the spatial distribution of each heavy metal using SGS, and calculated Hakanson PERIs for individual metals and multiple metals based on the simulated realizations. The spatial uncertainty of the Cd PERI and its occurrence probabilities in different risk grades were further assessed. Results show that the potential ecological risks of Cr, Cu, Pb, and Zn are relatively low in the study area, but Cd indeed reaches a serious level that deserves much attention and essential treatment. The total PERI of multiple heavy metals indicates a moderate grade in most of the study area. In general, combining SGS and the Hakanson PERI appears to be an effective method for evaluating the potential ecological risks of heavy metals in soil and the priority areas for remediation.     

Comparison of Source Identification of Metals in Road-Dust and Soil

Source identification of toxic metals is very critical for pollution prevention and human health protection. Many studies only use either road dust metal data or soil metal data to evaluate metal contamination and identify pollution sources, and this may lead to the exclusion of some important information. In this study, the differences of metal spatial distribution and source identification between road dust and associated soil in an industrial area were investigated.

Results indicate the metal concentrations in road dust were generally higher than those in soil. Based on the average concentrations, the order for dust metal concentrations was Fe>>Zn>>Pb>Cu>Cr>Ni. The order for soil metal concentrations was slightly different, namely Fe>>Zn>>Cu～Pb>Ni>Cr. The spatial distributions of metals in the road dust were very different from those in the soil, except for Fe. The GIS results indicate that elevated levels of Fe, Zn, and Pb were present in road dust near a steel plant. High concentrations of Cu, Cr, and Ni appeared at a road intersection. Elevated metal concentrations of Fe, Zn, Pb, Cu, and Cr were present in soil around the steel plant. A coal-fired power plant did not seem to be a significant metal source in this study. Significant correlations for dust metals imply that these were well mixed in the study area. The metal sources identified by PCA with soil metal data were obviously different from those identified with road dust metal data. When road dust metal data were used, the changes of PCA analyzed areas slightly influenced the source identification. The PCA results were obviously influenced by changes of analyzed areas when soil metal data were used.     

Behavior of Enzyme Activities Exposed to Contamination by Heavy Metals and Dissolved Organic Carbon in Calcareous Agricultural Soils

To investigate the relevance of biochemical parameters in biogeochemical mechanisms of the soil, it is important to gather data related to different soil types under different pedogeoclimatic conditions. In this study, we investigated on the calcareous agricultural soils in the Saiss plain (North Morocco). Four agricultural soils exposed to multi-metal (Cr, Cu, Zn, and Ni) and organic matter (OM) contamination as a result of irrigation with Oued Fez and Oued Sebou waters that are affected by urban and industrial activities around the city of Fez were studied and compared to a reference site irrigated with uncontaminated water. The study concerned soil physicochemical properties and the activity of a range of enzymes [phosphatase (PHOS), arylsulfatase (SULF), urease (UREA), arylamidase (AMID), β-galactosidase (GALA), glucosidase (GLUC), and laccase (LACA)] related to nutrients cycles. Pearson's correlations between these parameters showed that soil enzymatic activities (PHOS, SULF, UREA, GALA, GLUC, and LACA) were correlated positively with heavy metals (Cu, Zn, and Cr) concentrations in the soil and also with dissolved organic carbon (DOC), and negatively with the aromaticity (AROM) of these compounds. Interestingly, analysis of intra-site correlations showed strong relationships among enzyme activities in the reference soil, while in contaminated soils, these activities were largely unrelated to each other. It was concluded that soil irrigation with heavy-metal- and OM-contaminated watercourses over decades has resulted in soils with high enzymatic activities function and nutrient turnover but altered relationships among geochemical cycles.     

Phytoextraction of Heavy Metals from Highly Contaminated Soils Using Sauropus androgynus

It has been found that Sauropusandrogynus has a strong adaptive capacity in multiple heavy-metal-contaminated soils. Field trials in highly heavy-metal-contaminated soils were conducted to investigate the extraction efficiency of Cd, Cu, Pb, and Zn by S. androgynus. The yield of S. androgynus could reach 10.01 t ha^?1, and the amount of Cd, Cu, Pb, and Zn extracted by the plant was 57.36, 218.57, 2078.11, and 19.64 g ha^?1, respectively. S. androgynus removed 0.35%, 0.01%, 0.03%, and 1.37% of the total soil Cd, Cu, Pb, and Zn in one growing season, respectively. By comparing the extracting capability and yield with some hyperaccumulators reported in the literature, S. androgynus was considered to be a highly effective plant to extract heavy metals (Cd, Cu, Pb, and Zn). The plant should be useful for phytoextraction of soils contaminated by the heavy metals.     

Optimization of Operating Parameters for the Selective Flotation of Heavy Metals from Contaminated Fine Sediment Using Response Surface Model

In this study, the effect of different flotation operating variables, such as pH, pulp density, collector concentration, impeller speed, frother concentration, and air flow rate, on selective flotation of heavy metals, especially Cu, from fine dredged sediment has been evaluated. Parameter optimization was done using the single parameter at a time method and response surface method (RSM) using Box-Behnken design and was assessed in terms of metal removal, metal recovery, metal concentration factor, and mass recovery. Among the operating variables studied, pulp pH, collector concentration, pulp density, and impeller speed were found to have significant effect on metal flotation selectivity. A validation study of the response surface model showed its aptness to predict the optimum values of operating parameters and their interactions on flotation responses which evaluate flotation performance. Flotation experiments under optimum operating parameters showed good flotation selectivity for Cu (3.3 ± 0.2) with a mass recovery of (mass of sediment in the froth) 14.1 ± 1 and Cu removal of 37.4 ± 3.6%.     

Nematodes as Sentinels of Heavy Metals and Organic Toxicants in the Soil

Field and laboratory research has repeatedly shown that free-living soil nematodes differ in their sensitivity to soil pollution. In this paper, we analyze whether nematode genera proved sensitive or tolerant toward heavy metals and organic pollutants in six long-term field experiments. We discuss overlaps between nematode physiological responses to heavy metals and to organic pollutants, which may explain why nematodes can exhibit co-tolerance toward several contaminants. We propose a simple method for separating direct effects of soil contamination on nematode populations from indirect effects mediated through the food chain. Finally, we analyze the extent to which nematodes exhibited consistent responses across the experiments analyzed. Our results show that (a) indirect effects of pollution were generally strong; (b) fewer nematode genera were tolerant than sensitive; (c) many genera, including practically all Adenophorea, exhibited a common response pattern to contaminants; and (d) several genera of the Secernentea exhibited differential tolerance toward particular pollutants. We conclude that bioindication of soil contamination should preferentially be based on tolerant, and less on sensitive, nematodes. We provide a list of nematode genera that may potentially serve as differential bioindicators for specific soil contaminants.     

Quantification of Heavy Metals in Mining Affected Soil and Their Bioaccumulation in Native Plant Species

Several anthropogenic and natural sources are considered as the primary sources of toxic metals in the environment. The current study investigates the level of heavy metals contamination in the flora associated with serpentine soil along the Mafic and Ultramafic rocks northern-Pakistan. Soil and wild native plant species were collected from chromites mining affected areas and analyzed for heavy metals (Cr, Ni, Fe, Mn, Co, Cu and Zn) using atomic absorption spectrometer (AAS-PEA-700). The heavy metal concentrations were significantly (p < 0.01) higher in mine affected soil as compared to reference soil, however Cr and Ni exceeded maximum allowable limit (250 and 60 mg kg^?1, respectively) set by SEPA for soil. Inter-metal correlations between soil, roots and shoots showed that the sources of contamination of heavy metals were mainly associated with chromites mining. All the plant species accumulated significantly higher concentrations of heavy metals as compared to reference plant. The open dumping of mine wastes can create serious problems (food crops and drinking water contamination with heavy metals) for local community of the study area. The native wild plant species (Nepeta cataria, Impatiens bicolor royle, Tegetis minuta) growing on mining affected sites may be used for soil reclamation contaminated with heavy metals.     

Extraction of Arsenic and Heavy Metals from Contaminated Mine Tailings by Soil Washing

In this study, the soil washing technique has been used to treat mine tailings contaminated heavily with arsenic and heavy metals at Jingok mine, which is one of the abandoned mines in Korea. The results showed that phosphoric acid, citric acid, oxalic acid, and sodium metabisulfite were highly effective in extracting arsenic and heavy metals. Among them, oxalic acid was the most effective (especially for Pb, Cu, and Zn), as even a residual fraction of arsenic was partly extracted. The optimum concentration of washing reagent and the ratio between the mine tailings and washing reagent were found to be 0.5 M and 1:20, respectively. In addition, the extraction kinetics of arsenic and heavy metals was fast, in which the reaction time of 30 minutes was deemed to be a sufficient contact time. From the results, it may be concluded that the low pH of washing solution and the amount of dissolved Fe may be considered as the most important factors in the extraction of arsenic and heavy metals.     

The National Distribution Pattern and Factors Affecting Heavy Metals in Sediments of Water Systems in China

Heavy metal discharge has become one of the most serious environmental problems due to extensive industrialization. Sixty eight sediment samples from four wetlands were collected to analyze the regional factors affecting metal deposition. Meanwhile, a national sediment data collection based on relevant publications was developed covering the period from 2000 to 2016 to study the metal distribution in China. Principal metals assessed in this study are Cr, Cd, Cu, Pb, Zn, As, and Ni. At regional scale, the accumulation of Pb and Cd is significantly higher in surface than in subsurface sediments. At the national scale, heavy metals tend to increase with the increase in precipitation from 600 to 1500 mm. Further, metal deposition in the main river basins in China shows an increase trend from northern to southern China, and follows the order of: Pearl River > Yangste River > Yellow River > Hai River and Liao River. Cluster analyses show that these river basins contribute a large proportion of heavy metals to coastal metal deposition, which follows the order of: South Sea > East Sea > Bohai Sea > Yellow Sea. In general, metal deposition in sediments of water systems increases from northern to southern China irrespective of in-land area or coastal seas.     

Migration and Stabilization of Multiple Heavy Metals in an Aged Contaminated Soil under a Constant Voltage Electric Field

With the aim of metal decontamination, migration and stabilization of multiply heavy metals in an aged contaminated soil under a constant 1 V cm^?1 parallel-plate electric field were investigated through monitoring the metal migration in the anolyte, as well as analyzing their species distribution residual in soil. Besides anionic Cr(VI), cationic metals were also found in the anolyte, primarily by the concentration-gradient-driven diffusion of free ions, especially when the produced H⁺ considerably increased their levels in the soil. After 295 h, parts of Cu, Cr, Ni, and Zn were found to electro-migrate into the intermediate area, but no obvious Pb migration was observed, likely ascribed to its own great inertia and precipitation with the present Cr(VI). However, in the whole, only 5.3% of Zn and 2.7% of Ni were separated, while the release of other heavy metals was almost ignorable. Although Pb mobility in the soil near the anode even increased three times, the overall metal mobility in all sample locations was found to significantly reduce under the electric field, indicating an effective stabilization approach. Moreover, compared with the bottom soil, the top soil near the anode was found to have a lower pH, higher moisture, lower heavy metal concentrations, and less soil oxidant demand; these phenomena may be due to a faster electro-migration of charged ions, especially H⁺, in the top soil. Therefore, such a divergence may considered to improve the current simulation approach for a realistic estimation of the actual metal and H⁺ electro-migration rate and the associated behavior under an electric field.     

Multivariate relationships and spatial distribution of geochemical features of soils in Jamaica

Abstract

Concentrations of 31 chemical elements in 165 soil samples from the tropical island of Jamaica were analyzed during the island-wide soil survey. Multivariate outliers were detected and remedied for quality control of the database. Multivariate analyses including principal component analysis (PCA), cluster analysis, and analysis of variance (ANOVA), and a geographic information system (GIS) were applied to study the geochemical features of element associations and sample clusters. The results show that rare earth elements, most of the heavy metals and trace elements (including As, Al, Cd, Ce, Co, Cr, Dy, Eu, Fe, Hf, Hg, La, Lu, Mn, Pb, Sb, Sc, Sm, Th, Ti, U, V, Yb, Zn) are enriched in the bauxitic soils relative to the non-bauxitic soils, and closely correlated with one another. Negative correlations between the bauxite-enriched elements and the mobile alkali and alkaline earth elements including Ca, Sr, Mg and Na are observed, showing the opposite tendencies of enrichment of the immobile elements and leaching of the mobile elements during the soil formation processes. The halogen elements of Br and I are also relatively enriched in the bauxitic soils, but they appear to be rather affected by sea-spray. Copper has poor correlations with all the other elements, which is likely to be related to mineralization. Significantly different concentrations of the bauxite-enriched elements are observed between the bauxitic and non-bauxitic soils.