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Mine reclamation with biosolids increases revegetation success but nutrient addition well in excess of vegetation requirements has the potential to increase leaching of NO3 and other biosolids constituents. A 3-yr water quality monitoring study was conducted on a Pennsylvania mine site reclaimed with biosolids applied at the maximum permitted and standard loading rate of 134 Mg ha. Zero-tension lysimeters were installed at 1-m depth 1 yr before reclamation: three in the biosolids application area, one in a control area (no biosolids). Before reclamation, all water samples had pH in the range 4.7 to 6.2, acidity ,20 mg L, and very low levels of all other measured parameters. Following reclamation, percolate water in the biosolidstreated area had lower pH and greater acidity than the control area. Acidity was greatest during the first winter following biosolids application, decreased during the spring, and showed a similar pattern but with much smaller concentrations the second year. Maximum firstyear leachate NO3 concentrations were |300 mg L 21 and half as large the second year. Estimated inorganic N leaching loss during the first 2 yr after biosolids application was 2327 kg N ha. Aluminum, Mn, Cu, Ni, Pb, and Zn followed similar leaching patterns as did acidity, and their mobilization appeared to be the result of the increased acidity. These results indicate that large applications of low-C/N-ratio biosolids could negatively impact area water quality and that biosolids reclamation practices should be modified to reduce this possibility. BIOSOLIDS generated by municipal wastewater treatment facilities are commonly used for reclamation of surface-mined lands in the Appalachian Region of the USA. In a review of the literature, Haering et al. (2000) cited numerous studies documenting that the use of biosolids as a mine soil amendment increases the success of reclamation efforts relative to amendment with inorganic fertilizer and limestone, particularly if available topsoil is low in organicmatter or if overburden materials are used as topsoil substitutes. Extensive research on the use of biosolids in mine reclamation in the Appalachian Region was conducted in Pennsylvania in the late 1970s and 1980s (Sopper, 1993; Sopper and Kerr, 1982) and also in Virginia (Roberts et al., 1988a, 1988b; Daniels and Haering, 1994). In the Pennsylvania research, the biosolids application rates used were generally in the range of 80 of 134 Mg ha, with most sites receiving amounts at the upper end of the range. Much of the research was conducted with a 1:1 (by volume) mixture of anaerobically digested biosolids cake and composted biosolids cake containing wood chips known as “mine mix” that was produced by the City of Philadelphia. These application rates were found to promote long-term plant growth by supplying inorganic and slow-release organic N and P to low-fertilitymine soils. The large amount of addedorganic material was found to promote topsoil development, increase water holding capacity, and stimulate microbial activity and nutrient cycling (Seaker and Sopper, 1988a, 1988b). At these application rates, total N added was generally in the range of 650 to 1100 kg ha (|0.8 as organic N, |0.2 as NH4, and only trace amounts of NO3). Anaerobically digested biosolids cake generally has aC/N ratio ,10:1 and it is generally assumed that 20% of organic N in anaerobically digested biosolids cake will be mineralized in the first year following application (USEPA, 1995). Composted biosolids mineralize more slowly and generally 10% availability of organic N is assumed for the first year. Because the “mine mix” used in most of this research also contains wood chips, the overall C/N ratio of the material is generally .25:1 and is expected to have slower mineralization rates and possibly some N immobilization due to the added organic C (Haering et al., 2000). While some evidence of NO3 leaching following biosolids application at these rates was observed (Sopper and Kerr, 1982; Murray and Giddings, 1982; Carello, 1990; Cravotta, 1998), the increases were either relatively small or were limited to the first few months following biosolids application. Research conducted in Virginia has largely corroborated the work done in Pennsylvania (Haering et al., 2000), where superior revegetation success (both quantity and diversity) and soil development were achieved with biosolids compared with inorganic fertilizer. Philadelphia mine mix material was used at rates up to 552 Mg ha (equivalent to 150 Mg ha of biosolids only) but only limited evidence of NO3 leaching was observed and only during the first winter following application. The absence of significant N loss was attributed to the high C/N ratio of the mine mix and the added organic C provided by the wood chips. This was confirmed in later investigations of NO3 leaching at gravel mines reclaimed with biosolids cake at rates up to 98 Mg ha (Daniels et al., 2001; Schmidt et al., 2001). Leachate NO3 concentrations increased up to 100 mg L 21 with increasing biosolids cake applications, but NO3 leaching was greatly reduced when the biosolids was combined with sawdust to increase the C/N ratio to 20:1. Based largely on the Pennsylvania research, the Pennsylvania Department of Environmental Protection presently allows a one-time application of biosolids for mine reclamation at rates up to 134 Mg ha of biosolids (dry weight equivalent of biosolids excluding wood chips); however, this rule is applied to any biosolids, regardless of N content or C/N ratio, and most mine reclamation with biosolids in recent years has been done with anaerobically digested biosolids cake. FurtherCrop and Soil ScienceDepartment, The Pennsylvania StateUniversity, University Park, PA 16802-3504. Received 25Apr. 2005. *Corresponding author ([email protected]). Published in J. Environ. Qual. 35:1118–1126 (2006). Technical Reports: Vadose Zone Processes and Chemical Transport doi:10.2134/jeq2005.0134 a ASA, CSSA, SSSA 677 S. Segoe Rd., Madison, WI 53711 USA R e p ro d u c e d fr o m J o u rn a l o f E n v ir o n m e n ta l Q u a lit y . P u b lis h e d b y A S A , C S S A , a n d S S S A . A ll c o p y ri g h ts re s e rv e d . 1118 Published online May 31, 2006