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Watershed implementation plans (WIPs) require the development of management actions for a diversity of nitrogen (N) sources. Atmospheric, agricultural and septic system inputs interacting with land-use define how each nonpoint source contributes to the total N load and the load of each nitrogen form. Hence, we will evaluate the performance of older versus newer septic systems and develop organic tracers to track septic system effluents to determine if adjacent watersheds have been impacted by using innovative and new ultrahigh resolution mass spectrometric approaches combined with traditional measurements of nitrogen speciation and other nutrients, determination of optical properties of dissolved organic matter (DOM) and stable isotope signatures. Results from this study will lead an independent evaluation of septic systems including the attempt to develop novel organic septic system tracers. Development of a new source tracking indicators of wastewater will provide a powerful tool for communities seeking to evaluate the biogeochemical response of ecosystems to implementation of the Total Maximum Daily Loads (TMDL).
Water samples will be collected monthly throughout a year directly at the outflow of old and new (denitrification) septic systems. Additionally, water samples will be collected at the same time in adjacent watersheds that contain the old and new septic systems. Reference sites will be also included for comparison. Water chemistry analyses will include N species, DOC, particulate carbon and phosphorus, phosphate, pH and conductivity. To characterize the components of DOM in watersheds and septic system effluents, solid-phase extraction (SPE) will be undertaken and SPE extracts will be measured using ultrahigh resolution mass spectrometry to unambiguously assign molecular formulae to thousands of accurately measured mass peaks and yield unsurpassed molecular details about specific organic constituents. As soon as potential septic system tracers are found, the molecular structure will be determined by the MSn capability of the Thermo LTQ Orbitrap XL mass spectrometer available at CBL. For comparison of these new organic tracers with existing source tracking techniques, we will also analyze optical properties of all samples and the delta15N and delta 18O isotope signatures on selected samples.
As part of the TMDLs, county and municipal offices must submit watershed implementation plans (WIPs) to charter a course towards meeting mandated nutrients and sediment reductions. Coincident with these efforts has been the passage of the Sustainable Growth & Agricultural Preservation Act of 2012 by the MD legislature that limits septic systems for large lots and affects whether rural land use may be transformed into major subdivisions served by septic systems. This “Septic Bill” has met some resistance from rural counties, where the tiered approach to land development may have a greater impact on agricultural communities. There is widespread evidence and understanding how traditional septic systems transmit N to groundwater, but very little of this work has occurred in MD. Hence, it is of great interest to evaluate the effectiveness and impact of new on lot septic systems with advanced N removal technology including the development of novel organic tracers.