Influence of Adjuvants on Pesticide Soil-Air Partition Coefficients: Laboratory Measurements and Predicted Effects on Volatilization

A solid-phase fugacity meter was used to measure the soil–air partition coefficients of three semivolatile pesticides (chlorpyrifos, pyrimethanil, and trifluralin) in the absence of additional adjuvants (Ksoil–air,AI), as part of commercial formulations (Ksoil–air,formulation), and as formulation mixtures with an additional spray adjuvant added (Ksoil–air,formulation+spray adjuvant). Chlorpyrifos Ksoil–air,formulation values were also measured over 15–30 °C, allowing for the change in internal energy of the phase transfer reaction (Δsoil–airU) to be calculated and compared to the Δsoil–airU for Ksoil–air,AI from the literature. Measured Ksoil–air values were then used as input parameters in a pesticide volatilization model to understand how their variability affects pesticide volatilization rates under different conditions. Initial experiments conducted at ∼24 °C indicated that all pesticides volatilized more readily in the presence of adjuvants than in their absence and that the additional spray adjuvant had minimal impact. The Δsoil–airU values were 328 and 90 kJ/mol for chlorpyrifos in the absence and presence of formulation adjuvants, respectively, suggesting that adjuvants may weaken or disrupt intermolecular attractions between pesticide molecules and soil. At temperatures below 24.5 °C, modeled chlorpyrifos volatilization rates were higher in the presence of adjuvants than in their absence; however, the opposite occurred at temperatures above 24.5 °C

Measuring in situ reductive dechlorination rates in trichloroethene-contaminated groundwater

Trichloroethene (TCE) is the most frequently detected organic contaminant in groundwater, is classified as a probable human carcinogen, and exhibits toxicological effects on the human endocrine, immune, developmental, and reproductive systems. While significant research efforts have been devoted to the development of strategies for remediating TCE-contaminated groundwater, their advancement is currently hindered by limitations in current methodologies for measuring in situ reductive dechlorination rates, especially for sorbing solutes. This dissertation describes the development, evaluation, and demonstration of a method for measuring in situ reductive dechlorination rates that utilizes single-well, "push-pull" test technology. Initial field tests indicated that trichlorofluoroethene (TCFE) could be used as a surrogate for TCE in push-pull tests since (a) TCE and TCFE were transported similarly and (b) TCFE underwent reductive dechlorination by a pathway analogous to that of TCE while retaining the fluorine label. Because TCFE and TCE experienced sorption at the selected field site, a novel data analysis technique called "forced mass balance" (FMB) was developed to obtain in situ transformation rates of sorbing solutes from push-pull test data. The FMB technique was evaluated by quantifying errors in rates derived by applying FMB to push-pull test data generated by a numerical model. Results from simulated tests indicated that an example in situ rate for the reductive dechlorination of TCFE, which was obtained by applying FMB to field data, was underestimated relative to the true in situ rate by 10%. The utility of the rate-determination method presented in this dissertation was demonstrated by using it to evaluate the effectiveness of a chemical amendment, namely fumarate, at enhancing in situ reductive dechlorination rates in TCE-contaminated groundwater. Reductive dechlorination rates increased following three consecutive additions of fumarate in all five of the tested wells. The development of the rate-determination method described in this dissertation advances the state of bioremediation technology because methods for measuring in situ transformation rates are needed to both assess the potential for natural attenuation and to quantify the effects of bioremediation techniques in the field

Comparison of Accelerated Solvent Extraction (ASE) and Energized Dispersive Guided Extraction (EDGE) for the Analysis of Pesticides in Leaves

Various techniques have been evaluated for the extraction and cleanup of pesticides from environmental samples. In this work, a Selective Pressurized Liquid Extraction (SPLE) method for pesticides was developed using a Thermo Fisher Scientific Accelerated Solvent Extraction (ASE) system. This instrument was compared to the newly introduced (2017) extraction instrument, the Energized Dispersive Guided Extraction (EDGE) system, which combines Pressurized Liquid Extraction (PLE) and dispersive Solid Phase Extraction (dSPE). We first optimized the SPLE method using the ASE instrument for pesticide extraction from alfalfa leaves using layers of Florisil and graphitized carbon black (GCB) downstream of the leaf homogenate in the extraction cell (Layered ASE method). We then compared results obtained for alfalfa and citrus leaves with the Layered ASE method to those from a method in which the leaf homogenate and sorbents were mixed (Mixed ASE method) and to similar methods modified for use with EDGE (Layered EDGE and Mixed EDGE methods). The ASE and EDGE methods led to clear, colorless extracts with low residual lipid weight. No significant differences in residual lipid masses were observed between the methods. The UV-Vis spectra showed that Florisil removed a significant quantity of the light-absorbing chemicals, but that GCB was required to produce colorless extracts. Recoveries of spiked analytes into leaf homogenates were generally similar among methods, but in several cases, significantly higher recoveries were observed in ASE extracts. Nonetheless, no significant differences were observed among pesticide concentrations in field samples when calculated with the isotope dilution method in which labelled surrogates were added to samples before extraction. The extraction time with the ASE methods was ~45 minutes, which was ~4.5 times longer than with the EDGE methods. The EDGE methods used ~10 mL more solvent than the ASE methods. Based on these results, the EDGE is an acceptable extraction instrument and, for most compounds, the EDGE had a similar extraction efficiency to the ASE methods

Fate of the Organophosphate Insecticide, Chlorpyrifos, in Leaves, Soil, and Air Following Application

A field study was conducted to further our understanding about the fate and transport of the organophosphate insecticide, chlorpyrifos, and its degradation product, chlorpyrifos oxon. Leaf, soil and air sampling was conducted for 21 days after chlorpyrifos application to a field of purple tansy (Phacelia tanacetifolia). Air samples were collected using a high-volume air sampler (HVAS) and seven battery-operated medium-volume active air samplers placed around the field and on a 500-m transect extending away from the field. Chlorpyrifos was detected every day of the sampling period in all matrices, with concentrations decreasing rapidly after application. Chlorpyrifos oxon was only detected in air samples collected with the HVAS during the first three days after application. Wind direction played a significant role in controlling the measured air concentrations in near-field samples. The SCREEN3 model and chlorpyrifos’ Characteristic Travel Distance (CTD) were used to predict modelled chlorpyrifos concentrations in air along the transect. The concentration trend predicted by the SCREEN3 model was similar to that of measured concentrations whereas CTD-modelled concentrations decreased at a significantly slower rate, indicating that downwind chlorpyrifos concentrations in air were primarily controlled by air dispersion. The SCREEN3-predicted chlorpyrifos concentrations were \u3e5 times higher than measured concentrations, indicating that simple approaches for calculating accurate pesticide volatilization fluxes from agricultural fields are still needed. Finally, we found that measured concentrations in air on Days 0–2 at locations up to 500 m from the field were at levels considered concerning for human health

Current-Use Pesticides in New Zealand Streams: Comparing Results From Grab Samples and Three Types of Passive Samplers

New Zealand uses more than a ton of pesticides each year; many of these are mobile, relatively persistent, and can make their way into waterways. While considerable effort goes into monitoring nutrients in agricultural streams and programs exist to monitor pesticides in groundwater, very little is known about pesticide detection frequencies, concentrations, or their potential impacts in New Zealand streams. We used the ‘Polar Organic Chemical Integrative Sampler’ (POCIS) approach and grab water sampling to survey pesticide concentrations in 36 agricultural streams in Waikato, Canterbury, Otago and Southland during a period of stable stream flows in Austral summer 2017/18. We employed a new approach for calculating site-specific POCIS sampling rates. We also tested two novel passive samplers designed to reduce the effects of hydrodynamic conditions on sampling rates: the ‘Organic-Diffusive Gradients in Thin Films’ (o-DGT) aquatic passive sampler and microporous polyethylene tubes (MPTs) filled with Strata-X sorbent. Multiple pesticides were found at most sites; two or more were detected at 78% of sites, three or more at 69% of sites, and four or more at 39% of sites. Chlorpyrifos concentrations were the highest, with a maximum concentration of 180 ng/L. Concentrations of the other pesticides were generally below 20 ng/L. Mean concentrations of individual pesticides were not correlated with in-stream nutrient concentrations. The majority of pesticides were detected most frequently in POCIS, presumably due to its higher sampling rate and the relatively low concentrations of these pesticides. In contrast, chlorpyrifos was most frequently detected in grab samples. Chlorpyrifos concentrations at two sites were above the 21-day chronic ‘No Observable Effect Concentration’ (NOEC) values for fish and another two sites had concentrations greater than 50% of the NOEC. Otherwise, concentrations were well-below NOEC values, but close to the New Zealand Environmental Exposure Limits in several cases

Common variants near FRK/COL10A1 and VEGFA are associated with advanced age-related macular degeneration

Despite significant progress in the identification of genetic loci for age-related macular degeneration (AMD), not all of the heritability has been explained. To identify variants which contribute to the remaining genetic susceptibility, we performed the largest meta-analysis of genome-wide association studies to date for advanced AMD. We imputed 6 036 699 single-nucleotide polymorphisms with the 1000 Genomes Project reference genotypes on 2594 cases and 4134 controls with follow-up replication of top signals in 5640 cases and 52 174 controls. We identified two new common susceptibility alleles, rs1999930 on 6q21-q22.3 near FRK/COL10A1 [odds ratio (OR) 0.87; P = 1.1 × 10−8] and rs4711751 on 6p12 near VEGFA (OR 1.15; P = 8.7 × 10−9). In addition to the two novel loci, 10 previously reported loci in ARMS2/HTRA1 (rs10490924), CFH (rs1061170, and rs1410996), CFB (rs641153), C3 (rs2230199), C2 (rs9332739), CFI (rs10033900), LIPC (rs10468017), TIMP3 (rs9621532) and CETP (rs3764261) were confirmed with genome-wide significant signals in this large study. Loci in the recently reported genes ABCA1 and COL8A1 were also detected with suggestive evidence of association with advanced AMD. The novel variants identified in this study suggest that angiogenesis (VEGFA) and extracellular collagen matrix (FRK/COL10A1) pathways contribute to the development of advanced AMD

Pressurized Liquid Extraction of Polycyclic Aromatic Hydrocarbons From Silicone Rubber Passive Samplers.

Silicone rubber passive samplers effectively concentrate organic contaminants from water and are simple-to-use and robust. However, during the extraction of analytes from the samplers with organic solvents, oligomers associated with the rubber are inevitably extracted and this creates analytic challenges. Additionally, extraction methods that use Soxhlet or shaking are time-consuming and use large volumes of solvent. We evaluated a new method for the extraction of polycyclic aromatic hydrocarbons from silicone rubber passive samplers that uses pressurized liquid extraction with gel permeation chromatography. Extraction with dichloromethane at 100 °C provided better recoveries compared to that of 50 °C. The recoveries of 14 individual PAHs ranged from 81% to 102% and the mean recovery was 93% (standard deviation = 7). Relative to comparable methods in which Soxhlet or shaking were used for the extraction, this method uses considerably less solvent and time

Selective Pressurized Liquid Extraction of Halogenated Pesticides and Polychlorinated Biphenyls Form Pine Needles.

Pine needles are an ideal matrix for the long-term monitoring of semi-volatile organic compounds in the atmosphere because they are naturally occurring and distributed worldwide. However, typical extraction methods result in the co-elution of matrix-interfering compounds and thus require time-consuming clean-up steps. A selective pressurised liquid extraction method (S-PLE) for extracting current-use pesticides, historic-use pesticides and polychlorinated biphenyls (PCBs) from pine needles that does not require additional clean-up steps was developed and validated. The selective extraction was achieved by packing the extraction vessel with a fat retainer, Florisil, down-stream of the pine needle matrix. A fat to fat-retainer ratio of 0.0057 (corresponding to 35 g of Florisil per 10 g of pine needle sample) was selected to minimise the co-elution of matrix-interfering compounds. Three 5-min extractions were performed using 25:75 (v/v) dichloromethane:n-hexane and a solvent flush of 150%. The mean recovery of spiked current-use pesticides, historic-use pesticides and PCBs using this method was 71%, 72%, and 84%, respectively. The method was validated by comparing target analyte concentrations measured in a pine needle sample using the optimised S-PLE method to those obtained using a conventional PLE method with external clean-up. The method detection limits and reproducibility were similar for the two methods; however, sample preparation time was 67% shorter when using the S-PLE method

Contributions of Long-Range and Regional Atmospheric Transport on Pesticide Concentrations Along a Transect Crossing a Mountain Divide.

Twenty-one halogenated legacy and current-use pesticides and pesticide degradation products were measured in pine needles along a coast-to-coast transect that crossed the Southern Alps of New Zealand. Concentration profiles of nine pesticides were used to determine the influence of geographic sources on the atmospheric pesticide burden at the mountain sites. Pesticide concentration profiles were calculated for each source and mountain site by normalizing concentrations (adjusted for temperature at the site and air–needle partitioning) to the sum of all pesticide concentrations at the site. Each mountain site profile was compared to varying mixtures of the potential source profiles to determine the percent contribution of each source. The highest elevation mountain sites were primarily influenced by long-range, synoptic-scale northwesterly winds. Westerly upslope winds had little influence on any of the mountain sites. Easterly upslope winds from the Canterbury Plains, an agricultural region, strongly influenced the mountain sites within close proximity and had progressively less influence with distance