Abstract
Sediments in estuary areas are recognized as the ultimate reservoirs for numerous contaminants, e.g., toxic metals. Multivariate analyses by chemometric evaluation were performed to classify metal ions (Cu, Zn, As, Cr, Pb, Ni and Cd) in superficial sediments from Lingdingyang Bay and to determine whether or not there were potential contamination risks based on the BCR sequential extraction scheme. The results revealed that Cd was mainly in acid-soluble form with an average of 75.99% of its total contents and thus of high potential availability, indicating significant anthropogenic sources, while Cr, As, Ni were enriched in the residual fraction which could be considered as the safest ingredients to the environment. According to the proportion of secondary to primary phases (KRSP), Cd had the highest bioavailable fraction and represented high or very high risk, followed by Pb and Cu with medium risks in most of samples. The combined evaluation of the Pollution Load Index (PLI) and the mean Effect Range Median Quotient (mERM-Q) highlighted that the greatest potential environmental risk area was in the northwest of Lingdingyang Bay. Almost all of the sediments had a 21% probability of toxicity. Additionally, Principal Component Analysis (PCA) revealed that the survey region was significantly affected by two main sources of anthropogenic contributions: PC1 showed increased loadings of variables in acid-soluble and reducible fractions that were consistent with the input from industrial wastes (such as manufacturing, metallurgy, chemical industry) and domestic sewages; PC2 was characterized by increased loadings of variables in residual fraction that could be attributed to leaching and weathering of parent rocks. The results obtained demonstrated the need for appropriate remediation measures to alleviate soil pollution problem due to the more aggregation of potentially risky metals. Therefore, it is of crucial significance to implement the targeted strategies to tackle the contaminated sediments in Lingdingyang Bay.
Highlights
Rapid industrialization and urbanization have resulted in a large growth in consumption of sources of energy and severe environmental contamination
To have a better understanding of potential bioavailability, mobility and chemometric toxicity of metals in sediments which largely depend on the physicochemical form [9,10], the BCR sequential extraction technique was applied to the sediments collected from the studied area
The fractions from the first step of sequential extraction bound to acid-soluble fractions (F1) included water soluble, ion exchange and carbonate binding states, which were absorbed in clay and soil humus and were vulnerable to environmental changes and easier to be transformed and migrated under acidic conditions
Summary
Rapid industrialization and urbanization have resulted in a large growth in consumption of sources of energy and severe environmental contamination. Among the different types of pollutions, heavy metal contamination in soils has become an increasing environmental problem throughout in China. Marine sediment contains metal ions in several different types of physicochemical fractions that function as reservoirs of metals. High contents of heavy metals in coastal sediments may result from several anthropogenic activities, such as industrial and urban effluents [4]. It is reasonable that the measurement of metal fractionation has become increasingly significant since both the bioavailability and mobility of metal ions rely heavily on their specific chemical speciation and ways of tying to each of the diverse soil stages [3]. There has been considerable interest in understanding the associations between particulate metals and solid phase
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