Browsing by Subject "SPME"
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Item Evaluating sediment cap performance with PDMS profilers : field study of McCormick and Baxter Superfund Site(2010-08) Kuriakose, Liz; Reible, Danny D.During the Fall of 2009, a pilot study was conducted at the McCormick and Baxter (M&B) Superfund Site to evaluate polydimethylsiloxane (PDMS) profilers as a method for sediment cap performance monitoring. The profilers are shielded solid phase microextraction fibers, silica rods coated with polydimethylsiloxane (PDMS) as the sorbent. The deployment explored whether profiling PDMS could be used as a low impact, highly sensitive, long term monitoring strategy at M&B since the sediment operable unit will be transitioning to the “Operable & Maintenance” phase of Superfund cleanup. To evaluate sediment cap performance, a good understanding of the flux of contaminants from the sediment is required. While surface waters can illustrate this flux, they can also contain contaminants originating from upstream sources. The existing sampling plan at M&B uses a conventional porewater pumping sampling technique that measures both dissolved and particulate fractions. PDMS profilers measure only the freely dissolved fraction which has been shown to be a good indicator of bioavailability. These profilers also have lower detection limits (ng/L) and the ability to measure vertical concentration gradients which can help identify sources and mechanisms of the contamination. Each sampler was analyzed at three depths for the USEPA Priority Pollutant List of 16 polycyclic aromatic hydrocarbons (PAHs). PDMS measurements showed clear vertical profiling with large reductions in PAH concentrations through the sediment cap offshore. Nearshore, uniform concentration profiles were observed indicating increased vertical mixing as a result of tidal smearing. Further, ANOVA and Tukey-Kramer HSD analysis of sample variability revealed PAH concentrations were statistically different at two locations compared to the remainder of the sampling locations- indicating areas requiring closer attention. PDMS profilers were co-located at 13 of the 22 conventional porewater extraction sampling locations. The correlation of PDMS and conventional porewater extraction techniques was limited due to the low detection frequency by conventional porewater extraction methods as a result of the higher detection limits by that method. The correlation was good for light molecular weight PAHs with most measurements of the same order of magnitude and improved with increasing depth (due to the greater number of detections). 72% of the direct comparisons between PDMS-derived and conventionally-derived porewater concentrations were of the same order of magnitude. Any comparison between the two datasets is necessarily limited especially for the higher molecular weight PAHs, however, due to the large number of non-detects in the conventionally collected data.Item Evaluation of Sediment Toxicity Using a Suite of Assessment Tools(2010-01-15) Kelley, Matthew AAccurate characterization of risk of adverse ecological effects related to contaminated sediment presents a particularly difficult challenge. A series of studies has been conducted to investigate the utility of various tools for assessment of sediment toxicity. The goal of this research was to provide information which could help increase the accuracy with which predictions of toxicity could be made at hazardous sites. A calibration study was conducted using model PAHs, PCBs, a binary PAH mixture and a coal-tar mixture. This study was a collaborative effort among five university-based Superfund Research Programs (SRPs). Each program, with the help of funding through the NIEHS Superfund Research Program, has developed a chemical-class specific assay to estimate toxicity of contaminants in sediment. This suite of bioassays expands the range of data typically obtained through the use of standard aquatic toxicity assays. A series of caged in situ exposure studies has been conducted using juvenile Chinook salmon and Pacific staghorn sculpin in the Lower Duwamish Waterway. The study aimed to investigate the utility of selected biomarkers in evaluating the relationship between contaminants present in environmental samples and response in receptors following an in situ caged exposure. Results found that DNA adducts detected in exposed fish were significantly higher than controls in 2004 and 2006, and DNA adducts appear to be a reliable indicator of exposure, although no dose-response relationship was present. Western blot analysis of CYP1A1 was not indicative of exposure levels. The final study conducted was concerned with evaluating the utility of using solid phase microextraction (SPME) fibers in situ to evaluate contaminated sediment. Levels of PAHs and PCBs in sediment often exceeded sediment quality guidelines; however, results from aquatic toxicity bioassays using Hyalella azteca were mostly negative, thus levels of contaminants detected on SPME fibers could not be associated with adverse effects in Hyalella. However, regression analysis of total PAHs present in sediment and levels of PAHs detected in porewater SPME fiber samplers, which were placed 5 cm into the sediment for 30 days, revealed a strongly correlated linear relationship (R2 = .779). Normalization of the sediment data to total organic carbon was performed to determine if the trend would remain present, and the linear relationship was again confirmed (R2 =.709).