Relationships between heavy metal concentrations i

Authors: Chao Ma Rong Zheng Jiale Zhao Xiumei Han Li Wang Xiaojiang Gao Chaosheng Zhang

Publish Date: 2014/09/23

Volume: 15, Issue: 1, Pages: 139-152

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Abstract

Reclaimed coastal wetlands are an important land resource because of the shortage of cultivated land in coastal areas but few studies have focused on contamination of heavy metals in reclaimed agricultural soils especially in soils that have experienced longterm agricultural activities This study was carried out in Chongming Dongtan of the Yangtze Estuary which has undergone largescale reclamation activities with the aim of determining the concentrations and spatial distributions of heavy metals in different reclaimed zonesIn this study 50 soil samples were collected in the study area which was divided into three zones based on the history of reclamation post1998 1990s and 1960s and intertidal flats Soil metals Al Fe Mn Cu Cr Ni Zn and Pb soil pH Eh salinity soil organic matter SOM and grain sizes were analyzed Correlation analysis and factor analysis were employed to extract the main influencing factors on heavy metals in reclaimed soils Alnormalization was used to remove the grainsize effect The enrichment ratio ER was applied to reflect the chronological change of heavy metals after reclamation Inverse distance weighted IDW interpolation was used to create spatial distribution maps of the measured heavy metalsThere were significant positive correlations p  001 between the fine particle fractions 20 μm of soils and metal concentrations Background deposition of metals in the study area increased relative to the reference values of each zone during the last 50 years In zone post1998 the concentrations of Cu Zn and Pb after reclamation were lower than those before reclamation but not for Cr in zone 1960s and 1990s the concentrations of Cu Cr Zn and Pb were higher than those before reclamation In all the zones the reclamation process had little impact on the mobilization of Ni Our results showed that after Alnormalization the differences of heavy metal concentrations between different zones and their spatial distribution patterns were due to the combined effects of both background deposition and anthropogenic processes particularly in zone 1960sThe current heavy metal concentrations were mainly determined by the deposition background in Chongming Dongtan but the reclamation history had certain effects on heavy metal concentrations in the reclaimed soils The desalination leaching effect on heavy metals was mainly found for soils with shortterm reclamation zone post1998 but with longer reclamation history like zone 1960s and 1990s longterm agricultural activities had greatly influenced the concentrations of heavy metals

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