TECHNICAL REPORTS 263 Mined gypsum has been beneficially used for many years as an agricultural amendment. A large amount of flue gas desulfurization (FGD) gypsum is produced by removal of SO 2 from flue gas streams when fuels with high S content are burned. e FGD gypsum, similar to mined gypsum, can enhance crop production. However, information is lacking concerning the potential environmental impacts of trace metals, especially Hg, in the FGD gypsum. Flue gas desulfurization and mined gypsums were evaluated to determine their ability to affect concentrations of Hg and other trace elements in soils and earthworms. e study was conducted at four field sites across the United States (Ohio, Indiana, Alabama, and Wisconsin). e application rates of gypsums ranged from 2.2 Mg ha −1 in Indiana to 20 Mg ha −1 in Ohio and Alabama. ese rates are 2 to 10 times higher than typically recommended. e lengths of time from gypsum application to soil and earthworm sampling were 5 and 18 mo in Ohio, 6 mo in Indiana, 11 mo in Alabama, and 4 mo in Wisconsin. Earthworm numbers and biomass were decreased by FGD and mined gypsums in Ohio. Among all the elements examined, Hg was slightly increased in soils and earthworms in the FGD gypsum treatments compared with the control and the mined gypsum treatments. e differences were not statistically significant except for the Hg concentration in the soil at the Wisconsin site. Selenium in earthworms in the FGD gypsum treatments was statistically higher than in the controls but not higher than in the mined gypsum treatments at the Indiana and Wisconsin sites. Bioaccumulation factors for nondepurated earthworms were statistically similar or lower for the FGD gypsum treatments compared with the controls for all elements. Use of FGD gypsum at normal recommended agricultural rates seems not to have a significant impact on concentrations of trace metals in earthworms and soils. Effects of Gypsum on Trace Metals in Soils and Earthworms Liming Chen, Dave Kost, Yongqiang Tian, Xiaolu Guo, Dexter Watts, Darrell Norton, Richard P. Wolkowski, and Warren A. Dick* G ypsum (CaSO 4 ·2H 2 O) has a number of beneficial functions as a soil amendment in agriculture (Chen and Dick, 2011; EPRI, 2006; Wallace, 1994). It is a soluble source of the essential plant nutrients Ca and S and can improve overall plant growth. Gypsum amendments can also improve the physical and chemical properties of some soils. Physical properties improved by application of gypsum include promotion of soil aggregation, reduced dispersion of soil par- ticles, reduced surface crust formation, promotion of seedling emergence, increased water infiltration rates, deeper movement of Ca and S through the soil profile, and reduced erosion losses of soils and nutrients. Chemical properties improved by appli- cation of gypsum include those associated with subsoil acidity and Al toxicity. is can enhance deep rooting and the ability of plants to take up adequate supplies of water and nutrients during drought periods. Gypsum is also a commonly used amendment for sodic soil reclamation. A large amount of flue gas desulfurization (FGD) gypsum is produced by removal of SO 2 from flue streams when energy sources (generally coal) containing high concentrations of S are burned (American Coal Ash Association, 2011). Flue gas desulfurization gypsum has a higher CaSO 4 ·2H 2 O content and lower concentrations of many trace elements than commercially available mined gypsum (Dontsova et al., 2005; Srivastava and Jozewicz, 2001). Flue gas desulfurization gypsum may be used beneficially in agriculture (EPRI, 2006; Chen and Dick, 2011; Fisher, 2011). However, FGD gypsum contains higher concentrations of Hg and Se (Dontsova et al., 2005). In terms of agricultural function, the source of gypsum is not important. A potential constraint controlling use of a particular gypsum for agriculture is its trace element content. e higher concentrations of Hg and Se in FGD gypsum than in soils and mined gypsum have been identified as potential elements of concern when using FGD gypsum as an agricultural amendment (EPRI, 2011). Arsenic (As) is also cited as a potential element of concern due to its toxicity, although concentrations in FGD Abbreviations: EC, electrical conductivity; FGD, flue gas desulfurization. L. Chen, D. Kost, Y. Tian, X. Guo, and W.A. Dick, School of Environment and Natural Resources, The Ohio State Univ./The Ohio Agricultural Research and Development Center, Wooster, OH 44691; Y. Tian, Dep. of Vegetable Science, College of Agronomy and Biotechnology, China Agricultural Univ., Beijing, 100193, China; X. Guo, Key Laboratory of Advanced Civil Engineering Materials, Tongji Univ., Shanghai, 200092, China; D. Watts, USDA–ARS, National Soil Dynamics Lab., Auburn, AL 36832; D. Norton, USDA–ARS, National Soil Erosion Research Lab., West Lafayette, IN 47907; R.P. Wolkowski, Dep. of Soil Science, Univ. of Wisconsin- Madison, Madison, WI 53706. Assigned to Associate Editor Géraldine Sarret. Copyright © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. J. Environ. Qual. 43:263–272 (2014) doi:10.2134/jeq2012.0096 Received 5 Mar. 2012. *Corresponding author (dick.5@osu.edu). Journal of Environmental Quality SUSTAINABLE USE OF FGD GYPSUM IN AGRICULTURAL SYSTEMS SPECIAL SECTION