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Mikkelson K.M.,Colorado School of Mines | Dickenson E.R.V.,Colorado School of Mines | Dickenson E.R.V.,Water Quality Research and Development Division | Maxwell R.M.,Colorado School of Mines | And 2 more authors.
Nature Climate Change | Year: 2013

Increased ecosystem susceptibility to pests and other stressors has been attributed to climate change1, resulting in unprecedented tree mortality from insect infestations2. In turn, large-scale tree die-off alters physical and biogeochemical processes, such as organic matter decay and hydrologic flow paths, that could enhance leaching of natural organic matter to soil and surface waters and increase potential formation of harmful drinking water disinfection by-products3,4 (DBPs). Whereas previous studies have investigated water-quantity alterations due to climate-induced, forest die-off5,6, impacts on water quality are unclear. Here, water-quality data sets from water-treatment facilities in Colorado were analysed to determine whether the municipal water supply has been perturbed by tree mortality. Results demonstrate higher total organic carbon concentrations along with significantly more DBPs at water-treatment facilities using mountain-pine-beetle-infested source waters when contrasted with those using water from control watersheds. In addition to this differentiation between watersheds, DBP concentrations demonstrated an increase within mountain pine beetle watersheds related to the degree of infestation. Disproportionate DBP increases and seasonal decoupling of peak DBP and total organic carbon concentrations further suggest that the total organic carbon composition is being altered in these systems. Copyright © 2013 Macmillan Publishers Limited. Source

Holady J.C.,Water Quality Research and Development Division | Trenholm R.A.,Water Quality Research and Development Division | Snyder S.A.,University of Arizona
American Laboratory | Year: 2012

An analytical method for detecting nitrosamines was demonstrated in various water matrices, finished drinking, surface, and treated wastewater effluent. The method uses automated solid-phase extraction (ASPE) followed by analysis with GC-MS/MS using positive chemical ionization (PCI), quantitation was performed using isotope dilution. N-nitrosodimethylamine (NDMA) occurrence was evaluated in effluent from an Australian facility over a three-month period and ranged from 11 to 14 ng/L. Automated flow rates and solvent switching systems are more consistent than manual systems. The automated programming provides a batch run time of 1 hr, 45 min. ASPE achieves a high degree of sample throughput and maintains reproducibility. The technique demonstrates improved sample throughput over traditional methods of extraction. Source

Woods G.C.,Water Quality Research and Development Division | Woods G.C.,HDR | Dickenson E.R.V.,Water Quality Research and Development Division
Water Research | Year: 2016

N-Nitrosodimethylamine (NDMA) is a disinfection by-product (DBP) that is potentially carcinogenic and has been found to occur in drinking water treatment systems impacted with treated wastewater. A major gap in NDMA research is an understanding of the persistence of wastewater-derived precursors within the natural environment. This research sought to fill this knowledge gap by surveying NDMA precursors across the length of a wastewater effluent-dominated wash. Significant precursor reduction (17%) was found to occur from introduction into the wash to a point 9 h downstream. This reduction translates into a half-life of roughly 32 h for bulk NDMA precursors. Further laboratory experiments examining rates of photolysis, biodegradation and loss to sediments, illustrated that both photolytic and biological degradation were effective removal mechanisms for NDMA precursors. Loss to sediments that were acquired from the wash did not appear to reduce NDMA precursors in the water column, although a control conducted with DI water provided evidence that significant NDMA precursors could be released from autoclaved sediments (suggesting that sorption does occur). Microbial experiments revealed that microbes associated with sediments were much more effective at degrading precursors than microbes within the water column. Overall, this study demonstrated that natural processes are capable of attenuating NDMA precursors relatively quickly within the environment, and that utilities might benefit from maximizing source water residency time in the environment, prior to introduction into treatment plants. © 2015 Elsevier Ltd. Source

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