The Impact Of Leaching Beach Soil On Pore Water Chemical Character And Heavy Metal Bioavailability

In this paper, we collected the beach soil of Pearl River Estuary as our object, through out leaching method of desalination to investigate the influence of salt ions changes in the coexistence on changes of heavy metal speciation and the removal of heavy metals in the soil as well as heavy metal bioavailability, to provide effective foundation for the development and utilization of reclaimed tidal flats of the Pearl River Estuary, and the cultivation on saline and alkaline land.The salinity ion in soil pore water and the heavy metal content in soil as well as the heavy metal speciation were investigated in various stages of desalination during an experiment of leaching beach soil. Results show that salinity ion including Na+, K+, Mg2+, Ca2+, Cl- and SO42-decreased by 80.3%,73.5%,86.6%,90%,81.8%, 98.2% respectively compared to pre-leaching. The pH value of pore water increased with leaching time. The reductions of heavy metals after leaching were:Cd 26.6%, Pb 22.8%, Cu 16.9%, Cr 7.9%, Zn 9.1%. The concentrations of Pb, Cr, Cu, Zn and Cd in carbonate bound form decreased by 77.8%,61.7%,68.4%,67.1% and 7.1% respectively. The contents of Cd and Pb bound to Fe-Mn oxide decreased by 49.1%, 23.5% respectively. The procession of leaching desalination has influenced the chemical forms and migration status of heavy metal in soil.Through out the soil culture experiment of leaching Pearl River estuary beach soil with different salt, we prepared the nutrient solution with the salt and heavy metals closed to which in the soil culture experiment, to study the influence of leaching desalination on crops. The results showed:the salinity decreased was found to bate its uptake by the root of Common Amaranth for Cd,Pb,Cr,Cu and enhance its absorption ability for Ni.The absorption ability of Cd,Pb,Cu in the overground part of Common Amaranth has downtrend. The contents of Cd,Pb,Cr,Ni,Cu in the root of Common Amaranth> the contents of them in the overground part. The translocation abilities of Zn is strongest while to Cr is least. In the experiment of nutrient solution culture, the heavy metal distribution of Cd,Pb,Cr,Zn,Ni in Common Amaranth is the root> overground part in different contents of salinities, while Cu is overground part> the root. With the decreasing of the salinities in the nutrient solution, the contents of Cd,Pb,Cr,Cu have downtrend, but the Zn has uptrend in the overground part of Common Amaranth; the accumulation abilities of Cd,Cu were lower while to Zn,Ni was gather head in the overground part of Common Amaranth; The accumulation abilities of heavy metals in the root were Zn>Cd>Cu≈Ni>Cr>Pb in the root and Zn>Cu>Cd>Ni>Cr>Pb in the overground part of Common Amaranth. Translocation abilities of the overground part of Common Amaranth were Cu>Zn>Cd,Ni,Cr,Pb.