Browsing by Author "Anderson, Todd A. (TTU)"
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Item Determination of phosphite (HPO3−2) by a new IC/MS/MS method using an 18O-labeled HPO3−2 internal standard(2021) Sadeghi, Sepideh (TTU); Anderson, Todd A. (TTU); Jackson, W. Andrew (TTU)A new method has been developed to determine trace amounts of phosphite (HPO3−2) in environmental samples using ion chromatography with electrospray tandem mass spectrometry (IC-ESI/MS/MS). The method includes the production and use of an 18O-labeled HPO3−2 internal standard (IS). This isotopically labeled IS significantly improved sensitivity and could account for matrix suppression. The method detection limit (MDL) was determined as 0.017 and 0.034 μg L−1 of HPO3−2 (6.5 and 13 ng P L−1) using a 500 and 25 μL injection loop, respectively. Precision (1–10%) and accuracy (recoveries = 96–106%) were established for a range of environmental samples using known (spiked) addition. The impact of ionic interferences was investigated by evaluating the response of the internal standard in the presence of common anions with respect to distilled deionized water. The most significant interference was due to nitrate (100 mg-NO3− L−1) with a 99.99% reduction in IS intensity. The method was successfully applied to wastewater effluent, surface water, tap water, and soil samples. Relatively low concentrations <0.25 μg HPO3−2 L−1 were measured in tap water, surface water and wastewater effluent, and ~1.6 μg kg−1 HPO3−2 in soil samples, using both injection loops. Limited suppression was observed for all matrices. The largest IS peak area suppression (~98%) was observed in WW effluent with 500 μL injection loop; however, this method was able to quantify HPO3−2 with good recoveries and precision despite the mentioned suppression, supporting the ability of theItem Monitoring cyanobacterial toxins in a large reservoir: Relationships with water quality parameters(2019) Subbiah, Seenivasan (TTU); Karnjanapiboonwong, Adcharee (TTU); Maul, Jonathan D. (TTU); Wang, Degeng (TTU); Anderson, Todd A. (TTU)Cyanobacteria are widely distributed in fresh, brackish, and ocean water environments, as well as in soil and on moist surfaces. Changes in the population of cyanobacteria can be an important indicator of alterations in water quality. Metabolites produced by blooms of cyanobacteria can be harmful, so cell counts are frequently monitored to assess the potential risk from cyanobacterial toxins. A frequent uncertainty in these types of assessments is the lack of strong relationships between cell count numbers and algal toxin concentrations. In an effort to use ion concentrations and other water quality parameters to determine the existence of any relationships with cyanobacterial toxin concentrations, we monitored four cyanobacterial toxins and inorganic ions in monthly water samples from a large reservoir over a 2-year period. Toxin concentrations during the study period never exceeded safety limits. In addition, toxin concentrations at levels above the limit of quantitation were infrequent during the 2-year sampling period; non-detects were common. Microcystin-LA was the least frequently detected analyte (86 of 89 samples were ND), followed by the other microcystins (microcystin- RR, microcystin-LR). Cylindrospermopsin and saxitoxin were the most frequently detected analytes. Microcystin and anatoxin concentrations were inversely correlated with Cl-, SO-2 4 , Na+, and NH+4, and directly correlated with turbidity and total P. Cylindrospermopsin and saxitoxin concentrations in water samples were inversely correlated with MgC2 and directly correlated with water temperature. Results of our study are expected to increase the understanding of potential relationships between human activities and water quality.Item Perfluoroalkyl acids in sediment and water surrounding historical fire training areas at Barksdale Air Force Base(2022) Wilkinson, Rebecca S. (TTU); Lanza, Heather A. (TTU); Olson, Adric D. (TTU); Mudge, Joseph F. (TTU); Salice, Christopher J.; Anderson, Todd A. (TTU)Perfluoroalkyl acids (PFAAs) are environmentally persistent components of surfactants that consist of fully fluorinated carbon chains and a terminal sulfonate or carboxylate polar head moiety. Due to their unique amphiphilic properties, PFAAs are used in the manufacturing of products such as aqueous film forming foams (AFFF). There is cause for concern for PFAA contamination resulting from runoff and groundwater infiltration of AFFF that were used during fire training. This study analyzed water and sediment samples that were collected over a 13-month sampling period from bayous upstream and downstream of two former fire training areas located near Barksdale Air Force Base (BAFB); the occurrence and magnitude of PFAAs supported an aquatic ecological risk assessment of potential impacts of PFAAs at the site. Liquid chromatography coupled with mass spectrometry was used for determination of 6 PFAAs listed under the third Unregulated Contaminant Monitoring Rule (UCMR 3). Total PFAA concentrations in surface water and sediment samples ranged from 0 (ND) −7.1 ng/mL and 0 (ND) −31.4 ng/g, respectively. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were the predominant PFAAs detected. In general, perfluorosulfonates were quantified more frequently and at higher concentrations than perfluorocarboxylates. The perfluoroalkyl chain length of PFAAs also showed significant influence on PFAA concentrations when analyzed by Spearman's rank correlation analysis. Some contamination we observed in surface water and sediment samples from reference locations could be a result of local runoff from the use of commercial products containing per- and poly-fluoroalkyl substances (PFAS), but AFFF appears to be the primary source given the close proximity of the historical fire training areas.Item Targeted analysis and Total Oxidizable Precursor assay of several insecticides for PFAS(2022) Lasee, Steven (TTU); McDermett, Kaylin (TTU); Kumar, Naveen (TTU); Guelfo, Jennifer (TTU); Payton, Paxton; Yang, Zhao (TTU); Anderson, Todd A. (TTU)Targeted analysis for 24 Per- and Polyfluoroalkyl Substances (PFAS) was conducted on 10 insecticide formulations used on a United States Department of Agriculture crop research field. Perfluorooctane sulfonic acid (PFOS) was found in 6 of the 10 formulations with concentrations ranging from 3.92 to 19.2 mg/kg. Further analysis of soil and plant samples collected at the site found several additional PFAS, with PFOS being the most prominent. Suspect screening was then conducted on the formulations and provided several suspected PFAS in addition to the 24 targeted analyzed PFAS in 7 of the 10 samples, one of which showed no PFAS during targeted analysis. PFAS-precursor oxidation was then conducted on the two insecticide formulations with the greatest lists of suspected PFAS as validation of potential unknown PFAS in the formulations. This study revealed a previously unknown potential PFAS contamination source for rural and agricultural environments.Item Terrestrial Toxicity of Synthetic Gas-to-Liquid versus Crude Oil–Derived Drilling Fluids in Soil(2020) Arneson Westbrook, Lisa (TTU); Chase, Darcy A. (TTU); Mudge, Joseph (TTU); Hughes, Sarah A.; Lyon, Delina; Dong, Meijun (TTU); Carr, Deborah (TTU); Anderson, Todd A. (TTU)Unlike most other conventional petroleum products that are derived from crude oil, gas-to-liquids (GTLs) are petroleum products that are synthesized from natural gas (methane). This process results in GTL products having no sulfur and low aromatic content, so they should have less impact on human health and the environment compared with crude oil–derived products. The GTL have been registered for use as nonaqueous base fluids (NABF) in drilling muds, which help in the process of drilling wells for oil and gas extraction. It is through these uses and others that they enter terrestrial environments. This study aims to determine whether GTL were less toxic to terrestrial soil biota than conventional NABF used for land-based drilling, e.g., as diesel and low-toxicity mineral oil (LTMO). The fate and impact of these fluids under more realistic soil and aging conditions of a common west Texas (USA) oil-producing region (i.e., sandy loam soil with low organic matter and a hot arid climate) were assessed. Acute terrestrial toxicity studies were conducted on the soft-bodied terrestrial invertebrate earthworm (Eisenia fetida) along with three plant species, alfalfa (Medicago stavia), thickspike wheatgrass (Elymus lanceolatus), and fourwing saltbrush (Atriplex canescens). Changes in microbial community structure of the soils following additions of NABF were examined. The GTL NABF had lower toxicity compared with conventional NABF like diesel and LTMO, as measured by invertebrate toxicity, plant seed germination, and impact on the microbial community.Item Tracking neonicotinoids following their use as cotton seed treatments(2019) Kohl, Kristina L. (TTU); Harrell, Lauren K.; Mudge, Joseph F. (TTU); Subbiah, Seenivasan (TTU); Kasumba, John (TTU); Osma, Etem; Barman, Apurba K.; Anderson, Todd A. (TTU)Neonicotinoids are a leading class of insecticides on the global market, accounting for nearly 25%. They are widely used in both agricultural and residential settings. Causing neuron failure by irreversibly binding to the insect nicotinic acetylcholine receptor, neonicotinoids offer broad spectrum efficacy against a variety of pests. However, because they are non-selective with regard to insect species, there has been some concern with neonicotinoid use over threats to pollinators such as honeybees, and potential indirect effects to migratory waterfowl as a result of invertebrate prey population depletion. In order to study occurrence and fate of neonicotinoids (thiamethoxam and imidacloprid), we analyzed cotton leaves on plants grown from neonicotinoid-treated seeds and corresponding soil samples between cotton rows. Neonicotinoid concentration data from cotton leaves appears to be consistent with the claim that seed treatments protect plants for 3–4 weeks; by 30 days post-planting, neonicotinoid concentrations fell, in general, to 200 ng/g or lower. This represents about a 10-fold decrease from plant concentrations at approximately 2 weeks post-planting. It was found that neonicotinoids used as seed treatments remained present in the soil for months post planting and could be available for runoff. To that end, 21 playa wetlands were sampled; 10 had at least one quantifiable neonicotinoid present, three of which were classified as grassland or rangeland playas, two were urban, and the remaining five were cropland playas. In several instances, neonicotinoid concentrations in playas exceeded EPA chronic benchmarks for aquatic invertebrates.Item Unraveling the relative importance of oral and dermal contaminant exposure in reptiles: Insights from studies using the western fence lizard (Sceloporus occidentalis)(2014) Weir, Scott M. (TTU); Talent, Larry G.; Anderson, Todd A. (TTU); Salice, Christopher J. (TTU)Despite widespread recognition of significant data deficiencies, reptiles remain a relatively understudied taxon in ecotoxicology. To conduct ecological risk assessments on reptiles frequently requires using surrogate taxa such as birds, but recent research suggests that reptiles have significantly different exposure profiles and toxicant sensitivity. We exposed western fence lizards, Sceloporus occidentalis, to the same quantities of three model chemicals via oral (gavage) and dermal (ventral skin application) exposure for either 24 or 48 hours. Three phthalate esters (di-methyl phthalate [DMP], di-iso-butyl phthalate [DIBP], and di-n-octyl phthalate [DNOP]) were chosen as model chemicals because they represent a gradient of lipophilicity but are otherwise structurally similar. Overall, the more lipophilic phthalates (DIBP and DNOP) were found to have higher concentrations in tissues than the less lipophilic DMP. Significant differences in tissue concentrations between DIBP and DNOP were tissue-dependent, suggesting that delivery to a site of action following exposure is not only a simple function of lipophilicity. In dermal treatments, DMP usually had fewer detections (except in ventral skin samples), suggesting that lipophilicity (log Kow>2) is a requirement for uptake across the skin. In general, tissue residues were greater in oral treatments than dermal treatments (significant in adipose and liver tissue), but differences were driven strongly by differences in DMP which did not appear to be absorbed well across skin. When differences in tissue residue concentrations between oral and dermal exposure did occur, the difference was not drastic. Taken together these results suggest that dermal exposure should be considered in risk assessments for reptilian receptors. Dermal exposure may be an especially important route for reptiles as their ectothermic physiology translates to lower energetic demands and dietary exposure compared to birds and mammals. © 2014 Weir et al.