The Transportation of Heavy Metals with Various Particle Size Fractions From Irrigation Canal Into Farmland.

Heavy metals can transport from irrigation canal into soil system through the solution or colloid-facilitated processes. However, the relative importances of these two processes remain obscure. In this study, the soil particle fractions were separated with ultrasonic, in order to preserving the original properties of soils. And the preliminary results show that the distribution of heavy metals is related to various soil fractions. Most of the heavy metals of soils closed to gateway are contributed by sand and silt. With increasing soil depth and distance the contribution of heavy metals of sand will decrease but the silt and clay will increase. In the other word, sediments contained heavy metals were transported with irrigation water. The larger particles (sand) deposited near the gateway, but the smaller (silt and clay) could transport to long distance. Therefore, the concentration of heavy metals will decrease very quickly with the increasing distance from the entrance. This result indicates the importance of clay in transportation of heavy metals.