STUDIES ON THE EFFECTS OF ARSENIC ON FARMLAND ECOSYSTEM
Yang Jurong Ge Jiaman (Institute of Environmental Science, Beijing Normal University)
The effects of arsenic on crops, soil organisms, soil animals and soil microbes in the farmland ecosystem are described in this paper. Pot experiments show that arsenic may affect the growth of crops obviously. The production of crops decreases as the concentration of arsenic in-creases. The seneitiv-ity of different crops to arsenic are different. Paddy rice is the most sensitive to is, spring wheats and maizes more sensitive. The effects of different states of arsenic are rot alike either. Ortho arsenite is the most poisonous, arsenate more and arsenic sulfide less.The activities of bacteriostasia in soil layers are obviously checked by arsenic so that the total number of soil microbes decreases. The total number of soil microbes descends when we add 5ppm of soduim arsenite and 10ppm of soduim biarsenite, which restrain the behaviour of peripheral soil bacteria, such as azotobacter, sulphate-decomposing bacteria and cellulose-decomposing bacteria (Cellvibrio). Their survival rate declines, the activity and respiratory rate of arsenic-polluted soil decline, too.The number and distribution of earthworms are varied in different layers of arsenic-polluted soil. 50-80% of earthworms died off in soil with 100ppm of arsenic. Arsenic concentration within earthworm's bodies increases and its concentrated coefficient may be 1.32-7.44 .