Analyses And Evaluation Of Characteristics And Behaviors Of Heavy Metals In Soils Developed From Alluvial Deposits On Coastal Areas In Shanghai, China

An investigation of the behavior and availability of heavy metals, i.e., Cu, Zn, Ni, Pb, Cr, and Cd, based on the analysis of correlation between heavy metals and physical and chemical properties of coastal soils developed from alluvial deposits in Shanghai, China, has been conducted, in order to reveal the effect of the soil formation and development and the unsuited human activities on the activities and mobility of heavy metals in agricultural soils; Meanwhile, the activity and availability of the five chemical fractions, i.e., exchangeable (F1), carbonate-bound (F2), Fe/Mn oxide-bound (F3), organic matter-bound (F4), residual (F5), has been investigated by way of a sequential extraction technique, in order to analyze the relationship of the formation and development of coastal soils with the fractions of heavy metals; An investigation on heavy metal sources was conducted using multivariate statistical methods (principal component analysis, clustering analysis, and correlation analysis); A three-way data (sampling sites, heavy metals, heavy metal fractions) set was analyzed using multi-way (two-way and three-way) principle component analysis (PCA) method with the purpose of revealing the associations of heavy metals and their chemical fractions within their spatial distribution. The multi-way chemometric model Tucker3 was applied to this data set.The results showed that i) the soils still meet the needs of plant growth due to the moderate fertility with a soil texture of silty loam although the content of organic matters is lower, ii) total heavy metal content had a increase trend from the inland area to the coastal area, indicating the impact of alluvial deposits related to the soil formation on the distribution of heavy metals; iii) a significant positive correlation was found between heavy metals and some soil properties (i.e., clay content, cation exchange capacity, organic matters, total Phosphorous content, etc.), indicating that the regulation of these properties could give some great effect on the behavior and availability of heavy metals; iv) the positive correlation among Cu, Zn, Ni, and Cd, and between Pb and Cr is very significant, suggesting the most similar, if not the same, origins of heavy metals;The results from the heavy metals fractions indicated that: i) the Fe/Mn oxide bound were between 7-41%; ii) the organic matter bound were between 7-34%; iii) the residual were≥30%; iv) the carbonate bound and the exchangeable were≤10%. It was necessary to control the amount of exchangeable and carbonate-bound heavy metals due to the much easier transformation into the soluble ones.Significant positive correlation was found between certain fractions of heavy metals and some soil properties, i.e., Fe2O3 content, pH, electronic conductivity, and organic matters. Some negative correlation was also found, e.g., clay content, cation exchange capacity and the amount of bacteria etc.All the results of the multivariate analysis showed that: i) Cu, Ni, Pb, and Cd had anthropogenic sources (e.g., overuse of chemical fertilizers and pesticides, industrial and municipal discharges, animal wastes, sewage irrigation, etc.); ii) Zn and Cr were associated with parent materials and therefore had natural sources (e.g., the weathering process of parent materials and subsequent pedo-genesis due to the alluvial deposits). The effect of heavy metals in the soils was greatly affected by soil formation, atmospheric deposition, and human activities.The result showed that the three-way PCA successfully provided in-depth information about the sampling sites, heavy metals, and heavy metal fractions. And the analysis and assessment on heavy metal pollution was concluded based on these results of modeling method.These findings are helpful to the soil remediation, fertility adjustment, and plant cultivation. It is very helpful to reveal the effect of the soil formation and development and the unsuited human activities on the activities and mobility of heavy metals in agricultural soils. And it also provided essential information on the possible sources of heavy metals which would contribute to the monitoring and assessment process of agricultural soils in worldwide regions.