The Effect of Flue Gas Desulfurization Residue on Corn (Zea mays L.) Growth and Leachate Salinity: Multiple Season Data from Amended Mesocosms

Abstract

The environmental effects of applying a weathered flue gas desulfurization residue (FGD) to soil was monitored in a mesocosm experiment conducted over several cropping periods. Dry biomass and elemental composition of crop plants were measured, as well as the quality and chemical composition of soil and leachate collected from treated mesocosms. Data collected in the first year following FGD amendment showed no effect on the germination of corn (Zea mays L. var Dekalb DK-683), soybean (Glycine max L. Merr. Var. Haskell Pupa 94), radish (Raphanus sativus L. var. Sparkler), and cotton (Gossypius hirsutus L. var. Deltapine 51) and a significant stimulation in biomass. Metal and metalloid enrichment of plant tissues, specifically As, B, Se and Mo was also significant. Application of FGD residue drastically altered the pH of the soil and the salinity of the leachate. Studies were continued into a second season to monitor the duration of beneficial and deleterious effects arising from FGD amendment, as it is expected that the majority of environmental effects will occur in the initial season following application. Second season data using a monoculture of corn showed no significant stimulation or inhibition of biomass, in contrast to findings of the initial year. Concentrations of metals and metalloids within plant tissues in the second season were lower, although still elevated above control concentrations. Electrical conductivity of mesocosm leachate; elevated from a control level of 0.05 dS m−1 to 3.4 dS m−1 with addition of 100 tons FGD acre −1, was still elevated 550 days after application. Repeated monitoring of leachate salinity showed evidence of only a slight decline 928 days after application. Soil data collected at the end of the second growth season showed that Se concentration had fallen below detection limits, and levels of As had also fallen by approximately 29%. The duration of environmental effects from FGD residue application can be summarized in terms of their half-lives, i.e. the length of time required for a 50% reduction in altered environmental parameters toward control levels. When half-lives for plants, soil and leachate are compared, the increase in soil pH and leachate salinity have the longest half-lives, and stimulation of plant biomass the shortest.