EVALUATION OF 4 CHEMICAL EXTRACTANTS FOR METAL DETERMINATIONS IN WETLAND SOILS

Wetland soils (hydric soils) are unique in their chemical characterist ics compared to upland soils. It is known that they are capable of rem oving a variety of wastes from polluted water entering the wetland inc luding metals and potentially toxic heavy metals. When these metals ar e determined in wetland soils, it is necessary to use the proper chemi cal extractant(s). Four commonly used chemical extractants (Mehlich 1, Mehlich 3, 0.1M HCl, and DTPA) for soil fertility evaluation were sel ected to measure metal concentrations of three different wetland soils /spoils. Soil samples were collected from the constructed wetland cell s which were lined with Abernathy silt loam topsoil and two different mine spoil materials [collected from active coal strip-mined sites in Alabama (pH 5.9) and Tennessee (pH 3.2)]. Mehlich 3 extracted the most zinc (Zn), iron (Fe), manganese (Mn), calcium (Ca), magnesium (Mg), p otassium (K), sodiumm (Na), and aluminum (Al), while 0.1M HCl extracte d more cadmium (Cd), copper (Cu), and lead (Pb). Extractants followed the same trend in removing quantities of the metals from the three soi l/spoil materials, with DTPA generally extracting the least amount of the metal (the trend was Mehlich 3 > 0.1N HCl > Mehlich 1 > DTPA). How ever, DTPA removed larger quantities of metals from Tennessee spoil co mpared to Alabama spoil and topsoil, suggesting the higher effectivene ss of DTPA under acidic conditions. Metal concentrations in plant tiss ue did not show a definite trend in correlation with metals extracted by the four chemical extractants.