Effects of season and sediment-water exchange processes on the partitioning of pesticides in the catchment environment: Implications for pesticides monitoring.

Current and historic pesticide use has potential to compromise e.g. drinking water sources due to both primary and secondary emission sources. Understanding the spatial and temporal dynamics of emissions might help inform management decisions. To explore this potential; water, sediment and soil samples were concurrently collected from the River Ugie, Scotland over four seasons. Occurrence and fate of nine pesticides including four historic-use pesticides (HUPs): simazine, atrazine, isoproturon and permethrin, and five current-use pesticides (CUPs): metaldehyde, chlorpyrifos, chlortoluron, epoxiconazole and cypermethrin were analysed. Concentrations of target pesticides in water, sediments and soils were 4.5-45.6 ng·L-1, 0.9-4.6 ng·g-1 dw (dry weight) and 1.7-8.0 ng·g-1 dw, respectively. Concentrations of pesticides in water were found to significantly differ between seasons (p < 0.05). Significant differences in pesticide concentrations also occurred spatially within sediments (p < 0.01), indicating spatial and temporal associations with pesticide use. Sediment-water exchange showed that the sediment acts as an important secondary emission source particularly for the HUPs, while current local application and sediment emission are both major driving forces for CUPs in the riverine environment. These findings were supported by concentration ratios between different media, which showed potential as a preliminary assessment tool for identifying the source of pollutants in aquatic environments.

Risk estimation and annual fluxes of emerging contaminants from a Scottish priority catchment to the estuary and North Sea.

Emerging contaminants (ECs) such as endocrine-disrupting chemicals (EDCs) and pharmaceuticals and personal care products (PPCPs) attracted global concern during the last decades due to their potential adverse effects on humans and ecosystems. This work is the first study to assess the spatiotemporal changes, annual fluxes and ecological risk of ECs (4 EDCs and 6 PPCPs) by different monitoring strategies (spot and passive sampling) over 12 months in a Scottish priority catchment (River Ugie, Scotland, 335 km2). Overall, the total concentration in water ranged from 1. This suggests that mitigation measures might need to be taken to reduce the input of emerging contaminants into the river and its adjacent estuary and sea.

Evaluation of spot and passive sampling for monitoring, flux estimation and risk assessment of pesticides within the constraints of a typical regulatory monitoring scheme.

In many agricultural catchments of Europe and North America, pesticides occur at generally low concentrations with significant temporal variation. This poses several challenges for both monitoring and understanding ecological risks/impacts of these chemicals. This study aimed to compare the performance of passive and spot sampling strategies given the constraints of typical regulatory monitoring. Nine pesticides were investigated in a river currently undergoing regulatory monitoring (River Ugie, Scotland). Within this regulatory framework, spot and passive sampling were undertaken to understand spatiotemporal occurrence, mass loads and ecological risks. All the target pesticides were detected in water by both sampling strategies. Chlorotoluron was observed to be the dominant pesticide by both spot (maximum: 111.8ng/l, mean: 9.35ng/l) and passive sampling (maximum: 39.24ng/l, mean: 4.76ng/l). The annual pesticide loads were estimated to be 2735g and 1837g based on the spot and passive sampling data, respectively. The spatiotemporal trend suggested that agricultural activities were the primary source of the compounds with variability in loads explained in large by timing of pesticide applications and rainfall. The risk assessment showed chlorotoluron and chlorpyrifos posed the highest ecological risks with 23% of the chlorotoluron spot samples and 36% of the chlorpyrifos passive samples resulting in a Risk Quotient greater than 0.1. This suggests that mitigation measures might need to be taken to reduce the input of pesticides into the river. The overall comparison of the two sampling strategies supported the hypothesis that passive sampling tends to integrate the contaminants over a period of exposure and allows quantification of contamination at low concentration. The results suggested that within a regulatory monitoring context passive sampling was more suitable for flux estimation and risk assessment of trace contaminants which cannot be diagnosed by spot sampling and for determining if long-term average concentrations comply with specified standards.

Simultaneous extraction and determination of various pesticides in environmental waters.

A simple and rapid method was developed for the simultaneous analysis of nine different pesticides in water samples by gas chromatography with mass spectrometry. A number of parameters that may affect the recovery of pesticides, such as the type of solid-phase extraction cartridge, eluting solvent in single or combination and their volumes, and water pH value were investigated. It showed that three solid-phase extraction cartridges (Strata-X, Oasis HLB, and ENVI-18) produced the greatest recovery while ethyl acetate/dichloromethane/acetone (45:10:45, 12 mL) followed by dichloromethane (6 mL) was efficient in eluting target pesticides from solid-phase extraction cartridges. Different water pH values (4-9) did not show a significant effect on the pesticides recovery. The optimized method was verified by performing spiking experiments with a series of concentrations (0.002-10 µg/L) in waters, with good linearity, recovery, and reproducibility for most compounds. The limit of detection and limit of quantification of this optimized method were 0.01-2.01 and 0.02-6.71 ng/L, respectively, much lower than the European Union environmental quality standard for the pesticides (0.1 µg/L) in waters. The proposed method was further validated by participation in an interlaboratory trial. It was then subsequently applied to river waters from north-east Scotland, UK, for the determination of the target pesticides.

Selective pressurized liquid extraction of estrogenic compounds in soil and analysis by gas chromatography-mass spectrometry.

A selective pressurized liquid extraction (SPLE) method, followed by gas chromatography-mass spectrometry (GC-MS), for the simultaneous extraction and clean-up of estrone (E1), 17ß-estradiol (E2), 17α-ethynylestradiol (EE2), estriol (E3) and bisphenol A (BPA) from soil samples is described. The on-line clean-up of soil by SPLE was achieved using different organic matter retainers, including silica, alumina and Florisil, the most effective being silica. Thus, different amounts of silica, in conjunction with different extraction solvents (acetone, ethyl acetate, isohexane and dichloromethane), either alone or in combination, were used to extract the target chemicals from spiked soil samples. It was shown that 3g silica resulted in satisfactory rates of recovery of target compounds and acetone:dichloromethane (1:3, v/v) was efficient in extracting and eluting estrogenic compounds for SPLE. Variables affecting the SPLE efficiency, including temperature and pressure were studied; the optimum parameters were 60°C and 1500 psi, respectively. The limits of detection (LODs) of the proposed method were 0.02-0.37 ng g(-1) for the different estrogenic chemicals studied. The outputs using the proposed method were linear over the range from 0.1 to 120 ng g(-1) for E1, E2, EE2, 0.2-120 ng g(-1) for E3, and 0.5-120 ng g(-1) for BPA. The optimized method was further verified by performing spiking experiments in natural soil matrices; good rates of recovery and reproducibility were achieved for all selected compounds and the method was successfully applied to soil samples from Northeast Scotland, for the determination of the target compounds.