The Applications of Chemical Analyses of Sediments and Soils in ...

Lead in soil is relatively unavailable to plants as shown by tracer studies(Committee on Biologic Effects of Atmospheric Pollutants,1972,p 30). Lead falling onplant leaves may be bound by local ligands and hence cannot be washed off (NationalResearch Council, 1974).Lead shot pellets have been found to cause enormous casualties among ducksby lead poisoning (IJC, 1974).Lead molybdate (PbMoO 4)is an important reaction product controlling thesolubility of molybdenum in soil (Lindsay, 1975). MoO 4 2- was controlled by Pb 2+ activitywhich in turn was controlled by SO 4 2- , PO 43-or CO 32-depending on pH.COPPER AND MOLYBDENUMCopper is highly toxic to algae. The addition of only 5 µg/L to Lake Ontario waterdepressed photosynthesis by 50 percent (Chan et al, 1970). Ligands in natural waterscan mask added Cu 2+ ions reducing their toxicity (Gächter et al, 1973).High levels of copper and molybdenum from atmospheric fall-out causing injuryto plants have been noted (Cannon and Anderson, 1971) with highest levels nearsmelters. There is an interaction between copper, molybdenum and sulphate. Theconcentration of copper in the liver correlate with dietary intake (Underwood, 1971)and inversely by MoO 4 and SO 4 .13