Effect Of Salinity On Environmental Behaviors Of Heavy Metals In Wetland Soil From The Pearl River Estuary

In this paper, we collected the soils from the Pearl River estuary which enduring double effects from salinity and heavy metals, and studied the effect of salinity on environmental behaviour of heavy metals, to provid effective foundation for the development and utilization of reclaimed tidal flats of the Pearl River Estuary, and the cultivation on saline and alkaline land.1.Using laboratory incubation experiment, five forms of added heavy metals were extracted by Tessier sequential extraction procedure. The effects of salinity on their chemical forms in spiked wetland soils were studied. The results showed that very few of the added heavy metals were changed into residual form after eight month incubation. With increasing loads of heavy metals in the soils, the percentage of residual form decreased, while the percentage of the other four fractions increased. The spiked Cu, Pb, Ni, Cr, and Zn were preferentially transformed into Fe-Mn oxides bonded fraction. The spiked Cd was mostly transformed into exchangeable and carbonate fractions. At relatively lower level salinity of soil, the percentages of exchangeable fractions for Cu, Zn, Cd and Pb in soils increased with increasing salinities.2. Plants growed in soils with varying salininies to study the effect of salinity on heavy metal bioavailability.The results showed:the salinity was found to enhance its uptake by plants for Cr,Pb. The translocation ability for Ni in Common Amaranth inceased with increasing salinity. The distribution of Cr,Ni,Pb in different parts of tomato was root>stem>leaf>fruit, root≈stem>leaf≈fruit, root≈leaf>stem>fruit respectively, while they were all root>overground part for Common Amaranth. The accumulation abilities of heavy metals in the root, stem, leaf and fruit of tomato were Cr>Pb,Ni, Ni>Cr accumulation>Pb, Pb>Ni,Cr, Ni>Cr>Pb, while they were Cr>Pb >Ni, Pb>Ni>Cr for root, overground part of Common Amaranth respactively. The translocation abilities of root-stem, stem-leaf, stem-fruit were Ni> Cr>Pb, Pb>Cr>Ni, Cr,Ni>Pb; For Cr,Ni, the translocation abilities were root-stem>stem-leaf>stem-fruit, while it was stem-leaf>root-stem>stem-fruit for Pb. The migration for Ni,Pb between root and overground part of Common Amaranth was greater than Pb, and the translocation ability between root and Overground Part of Common Amaranth was larger than that between soil and root.