Abstract
The distribution and assessment of heavy metal pollution in sediments have been extensively studied worldwide. Risk assessment methods based on total content, background values, and sediment quality guidelines are widely applied but have never been compared. We systematically sorted out these evaluation methods, obtained evaluation results using actual monitoring data, and compared their applicability. The results showed that the background values of different metals are significantly different, which may depend on their mobility. Geoaccumulation index (Igeo) and enrichment factor (EF) values invariably decreased with the increase of background values for individual heavy metal enrichment risk assessment. Compared with EF, Igeo also showed a significant positive linear correlation with heavy metal content. Pollution load index (PLI), modified contamination degree (mCd), and potential ecological risk index (RI) showed significant differences in response to background values and evaluation levels for the comprehensive risk of heavy metal enrichment, but their distribution trends along with the sampling points were basically identical. Toxic risk index (TRI), mean ERM quotient (mERMQ), and contamination severity index (CSI) were used to evaluate the damage degree of complex heavy metals to aquatic organisms and shared a similar whole-process distribution trend. The modified hazard quotient (mHQ), which is used to evaluate the toxicity of a single heavy metal to aquatic organisms, showed a significant positive linear correlation with the total content of each heavy metal, indicating that the toxic effect on organisms can be predicted through the direct monitoring. The results of this study have important guiding significance for the selection of evaluation methods for heavy metal pollution in sediments.
Highlights
As one of the main pollutants in the water environment, heavy metals have raised concern regarding their effect on water ecosystem safety and human health
After 2.5 m, heavy metal concentrations basically remained stable, indicating that sediments beyond this depth were barely disturbed by human activities and the diagenesis decreased, which can be verified by isotope dating [36,37]
Risk assessment methods of sediment heavy metals calculated based on total conteHnet,rbeianc,krgisrokuansdsevssamlueens,tamnedthSQodGssowf seeredicmomenptahreedavfyrommetthalespcearlscpuelactteivdeboafsaepdpolincatotitoanl content, background values, and SQGs were compared from the perspective of application by substituted of actual monitoring data
Summary
As one of the main pollutants in the water environment, heavy metals have raised concern regarding their effect on water ecosystem safety and human health. Heavy metals in sediments will be released upward with the change of environmental conditions, causing secondary pollution of the water environment [3]. Various indexes have been developed to assess environmental risks for heavy metals in sediments based on their total contents, bioavailability, and toxicity [5,6,7]. Many researches have highlighted that the morphological content can well reveal the migration and toxicity of heavy metals in sediments, total content can directly reflect the degree and source of contamination [8,9]. Risk assessment based on total concentration calculation remains an indispensable method in the study of heavy metal pollution in water environment and a key pathway to identify pollution sources
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