title: Longitudinal data analysis in support of functional stability concepts for leachate management at closed municipal landfills.
abstract: Landfill functional stability provides a target that supports no environmental threat at the relevant point of exposure in the absence of active control systems. With respect to leachate management, this study investigates "gateway" indicators for functional stability in terms of the predictability of leachate characteristics, and thus potential threat to water quality posed by leachate emissions. Historical studies conducted on changes in municipal solid waste (MSW) leachate concentrations over time (longitudinal analysis) have concentrated on indicator compounds, primarily chemical oxygen demand (COD) and biochemical oxygen demand (BOD). However, validation of these studies using an expanded database and larger constituent sets has not been performed. This study evaluated leachate data using a mixed-effects regression model to determine the extent to which leachate constituent degradation can be predicted based on waste age or operational practices. The final dataset analyzed consisted of a total of 1402 samples from 101 MSW landfills. Results from the study indicated that all leachate constituents exhibit a decreasing trend with time in the post-closure period, with 16 of the 25 target analytes and aggregate classes exhibiting a statistically significant trend consistent with well-studied indicators such as BOD. Decreasing trends in BOD concentration after landfill closure can thus be considered representative of trends for many leachate constituents of concern.
authors.affiliation: Center for Health Statistics, University of Chicago, 5841 S. Maryland Avenue, Chicago, IL 60637, USA. Electronic address: rdg@uchicago.edu.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Gibbons
authors.affiliation: Geosyntec Consultants, 10220 Old Columbia Road, Suite A, Columbia, MD 21046, USA. Electronic address: jmorris@geosyntec.com.
authors.forename: Jeremy W F
authors.initials: JW
authors.lastname: Morris
authors.affiliation: Groundwater Protection Program, Waste Management, 1550 Balmer Road, Box 200, Model City, NY 14107, USA. Electronic address: cprucha@wm.com.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Prucha
authors.affiliation: Groundwater Protection Program, Waste Management, 3623 Wilson Road, Humble, TX 77396, USA. Electronic address: mcaldwell@wm.com.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Caldwell
authors.affiliation: Environmental Research and Education Foundation, 3301 Benson Drive, Suite 301, Raleigh, NC 27609, USA. Electronic address: BStaley@erefdn.org.
authors.forename: Bryan F
authors.initials: BF
authors.lastname: Staley
mesh_terms: D012044:Regression Analysis; D018505:Waste Management; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000517:prevention & control*
chemical_list: D014874:Water Pollutants, Chemical
keywords: Functional stability; Landfill; Leachate; Mixed-effects regression; Post-closure