Case study approach to modeling historical disinfection by-product exposure in Iowa drinking waters

In the 1980 s, a case–control epidemiologic study was conducted in Iowa(USA) to analyze the association between exposure to disinfection by-products(DBPs) and bladder cancer risk. Trihalomethanes(THMs), the most commonly measured and dominant class of DBPs in drinking water, served as a primary metric and surrogate for the full DBP mixture.Average THM exposure was calculated, based on rough estimates of past levels in Iowa. To reduce misclassification, a follow-up study was undertaken to improve estimates of past THM levels and to re-evaluate their association with cancer risk. In addition, the risk associated with haloacetic acids, another class of DBPs, was examined. In the original analysis, surface water treatment plants were assigned one of two possible THM levels depending on the point of chlorination. The re-assessment considered each utility treating surface or groundwater on a case-by-case basis. Multiple treatment/disinfection scenarios and water quality parameters were considered with actual DBP measurements to develop estimates of past levels. The highest annual average THM level in the re-analysis was156 μg/L compared to 74 μg/L for the original analysis. This allowed the analysis of subjects exposed at higher levels( 96 μg/L). The re-analysis established a new approach, based on case studies and an understanding of the water quality and operational parameters that impact DBP formation, for determining historical exposure.     

Transport of anthracene and benz(a)anthracene through iron-quartz and three aquifer materials in laboratory columns

In groundwater systems, dissolved natural organic matter (NOM) can influence the mobility of organic contaminants by altering the contaminant behavior in water and solid phases. The transport of anthracene and benz(a)anthracene (B(a)A) was studied in the presence and absence of NOM and/or soil organic matter (SOM) in column experiments. The results show that sorption are related to the properties of polycyclic aromatic hydrocarbons (PAHs), NOM and SOM. In the Fe-quartz media, the amount of NOM (20 mg/l) in solution had a little effect on increasing the apparent solubility of anthracene and countering increased anthracene sorption. In the natural (Bemidji) soil, Suwannee river fulvic acid (SRFA, 20 mg/l) and Suwannee river humic acid (SRHA) in water did not compete with SOM for anthracene, indicating that SOM has higher partition efficiency for anthracene. It was also observed that slow diffusion through an organic phase apparently caused most of the observed tailing in column breakthrough curves (BTCs). Even though the fOC of washed Bemidji sediment was very low, the transport of B(a)A was retarded significantly, however, and the transport of B(a)A was shown to be facilitated by dissolved NOM.     

Sources of polychlorinated biphenyl blank contamination and their impact on fingerprinting

Abstract

The development of high-resolution mass spectrometry methods for the measurement of polychlorinated biphenyls (PCBs) in environmental samples has dramatically reduced detection limits, leading to problems obtaining clean blanks. When PCBs are detected in samples at concentrations similar to the blanks, blank contamination must be addressed before fingerprinting and source apportionment through positive matrix factorization (PMF) can be successful. We tested a variety of blank correction methods using data from a study of water column concentrations of PCBs in the Spokane River, where concentrations of Σ₂₀₉PCBs in whole water samples averaged 171?pg/L without blank correction and Σ₂₀₉PCBs in the blanks averaged 88?pg/L. The results suggest that subtracting blank masses from sample masses can lead to erroneous results. Instead, censoring at one times the batch-specific blank level is a better approach. The sources of PCBs in field and method blanks were investigated by examining their congener profiles via PMF. The results suggest that commercial PCB formulations (in the US, Aroclors) continue to be the primary source of PCBs in blanks forty years after PCB production and use were banned in the United States. Other sources of PCBs to blanks include PCB 11 from pigments; PCBs 44?+?47?+?65, 45?+?51, and 68 arising from polymers cured using bis(2,4-dichlorobenzoyl) peroxide; and PCBs 1, 2, 3, 4, 8, 15 and others arising from silicone products derived from phenylsiloxanes, such as silicone-based adhesives.     

Conflict,controversy, and compromise: The Concho water snake (Nerodia harteri paucimaculata) versus the Stacy Dam and Reservoir

The Colorado River Municipal Water District (CRMWD) of Big Spring, Texas, planned to construct the Stacy Reservoir and Dam on the Colorado River near Paint Rock, Texas, yet needed a Section 404 permit from the US Army Corps of Engineers pursuant to the Clean Water Act. In 1986 the Concho water snake (Nerodia harteri paucimaculata) was listed as threatened under the Endangered Species Act (ESA). Much of its remaining range included the stretch of the Colorado River that would be flooded by the proposed dam. After initially rejecting CRMWD proposals for mitigation, and informing the Corps of Engineers that it would issue a jeopardy opinion regarding the 404 permit pursuant to Section 7 of the ESA, the US Fish and Wildlife Service reversed its stand. The final biological opinion stated that reasonable and prudent alternatives previously rejected as unfeasible would remove the threat of jeopardy. This paper concludes that experimental management techniques proposed by FWS to allow dam construction do not adequately ensure survival of the Concho water snake and an alternative water source should have been found.     

WATER QUALITY MODEL OUTPUT UNCERTAINTY AS AFFECTED BY SPATIAL RESOLUTION OF INPUT DATA1

ABSTRACT: Resolution of the input GIS data used to parameterize distributed‐parameter hydrologic/water quality models may affect uncertainty in model outputs and impact the subsequent application of model results in watershed management. In this study we evaluated the impact of varying spatial resolutions of DEM, land use, and soil data (30 × 30 m, 100 × 100 m, 150 × 150 m, 200 × 200 m, 300 × 300 m, 500 × 500 m, and 1,000 × 1,000 m) on the uncertainty of SWAT predicted flow, sediment, NO₃‐N, and TP transport. Inputs included measured hydrologic, meteorological, and watershed characteristics as well as water quality data from the Moores Creek watershed in Washington County, Arkansas. The SWAT model output was most affected by input DEM data resolution. A coarser DEM data resolution resulted in decreased representation of watershed area and slope and increased slope length. Distribution of pasture, forest, and urban areas within the watershed was significantly affected at coarser resolution of land use and resulted in significant uncertainty in predicted sediment, NO₃‐N, and TP output. Soils data resolution had no significant effect on flow and NO₃‐N predictions; however, sediment was overpredicted by 26 percent, and TP was underpredicted by 26 percent at 1,000 m resolution. This may be due to change in relative distribution of various hydrologic soils groups (HSGs) in the watershed. Minimum resolution for input GIS data to achieve less than 10 percent model output error depended upon the output variable of interest. For flow, sediment, NO₃‐N, and TP predictions, minimum DEM data resolution should range from 30 to 300 m, whereas minimum land use and soils data resolution should range from 300 to 500 m.     

PACIFIC NORTHWEST REGIONAL ASSESSMENT: THE IMPACTS OF CLIMATE VARIABILITY AND CLIMATE CHANGE ON THE WATER RESOURCES OF THE COLUMBIA RIVER BASIN1

ABSTRACT: The Pacific Northwest (PNW) regional assessment is an integrated examination of the consequences of natural climate variability and projected future climate change for the natural and human systems of the region. The assessment currently focuses on four sectors: hydrology/water resources, forests and forestry, aquatic ecosystems, and coastal activities. The assessment begins by identifying and elucidating the natural patterns of climate vanability in the PNW on interannual to decadal timescales. The pathways through which these climate variations are manifested and the resultant impacts on the natural and human systems of the region are investigated. Knowledge of these pathways allows an analysis of the potential impacts of future climate change, as defined by IPCC climate change scenarios. In this paper, we examine the sensitivity, adaptability and vulnerability of hydrology and water resources to climate variability and change. We focus on the Columbia River Basin, which covers approximately 75 percent of the PNW and is the basis for the dominant water resources system of the PNW. The water resources system of the Columbia River is sensitive to climate variability, especially with respect to drought. Management inertia and the lack of a centralized authority coordinating all uses of the resource impede adaptability to drought and optimization of water distribution. Climate change projections suggest exacerbated conditions of conflict between users as a result of low summertime streamfiow conditions. An understanding of the patterns and consequences of regional climate variability is crucial to developing an adequate response to future changes in climate.     

Spatial and behavioral interactions between a native and introduced salamander species

Behavioral interactions with native species may influence the invasiveness of introduced species. The salamanders Plethodon glutinosus and P. jordani in the eastern United States share many life history traits and demonstrate complex interspecific interactions that range geographically from competitive exclusion to sympatry. P. jordani was introduced to Mountain Lake Biological Station, Virginia, USA, between the years 1935 and 1945. We tested whether competition for space may influence the invasion of P. jordani into native P. glutinosus habitat by utilizing data from natural distributions, a field experiment, and controlled laboratory experiments. No environmental variables differed where P. glutinosus and P. jordani were collected in the field at the site of P. jordani introduction. In the field experiment, P. glutinosus was more fully exposed during foraging bouts in cages shared with heterospecifics as opposed to ones shared with conspecific salamanders. Condition (mass relative to body length) of salamanders at the end of the 3 months did not differ between conspecific and heterospecific treatments. In the laboratory, P. glutinosus most often attained the single burrow in the arena, but residency status had no effect. Species cohabited the burrow 50% of the time. Pair-wise encounters in the laboratory indicated that both species spend less than 20% of the time in aggressive behaviors as juveniles. Adults showed no behavior interpreted by us as aggression during pair-wise encounters. Received: 19 December 1999 / Accepted: 18 March 2000     

Evaluation of alternative approaches for screening contaminated sediments and soils for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans

Traditional high resolution mass spectrometry (HRMS) analysis for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) can be time consuming and expensive. Consequently, alternative methods are of great interest to regulatory agencies and others characterizing contaminated sites. One factor that hinders acceptance of alternative methods is a lack of performance information that assesses the alternative method's impacts on analytical results. The U.S. Environmental Protection Agency's Superfund Innovative Technology Evaluation Monitoring and Measurement Technologies Program (EPA SITE MMT) encourages the development and implementation of innovative and alternative monitoring methods by providing performance information on site characterization technologies. This paper presents a comparison of the results obtained from laboratory-based alternative approaches for screening sediment and soil samples for dioxin toxicity equivalents (TEQ(D/F)) to results obtained using traditional HRMS. The laboratory-based approaches included modifying the traditional HRMS analysis to make it more cost-effective (alternate 1613B), analyzing extracts that had been prepared for HRMS using low resolution mass spectrometry, and determining total organic carbon (TOC) content as an indicator of PCDD/F content. These comparisons demonstrated that TEQ(D/F) values generated using toxicity equivalency factors proposed by the World Health Organization in 1998 applied to alternate 1613B and LRMS analyses have a strong linear correlation to the TEQ(D/F) values derived in the same fashion from traditional HRMS analysis. These results would have placed >90% of the samples within the same concentration intervals using ranges of <0.05, 0.05-0.50, 0.50-5, and >5ng TEQ/g. Natural log transformed data for TOC had significantly weaker correlation to TEQ(D/F), indicating that TOC is not a reliable indicator of TEQ(D/F) concentrations.