Development of a Passive Sampling Technique for Measuring Pesticides in Waters and Soils

Abstract

It is essential to monitor pesticides in the environment to help ensure water and soil quality. The diffusive gradients in thin-films (DGT) technique can measure quantitative in situ labile (available) concentrations of chemicals in water, soil, and sediments. This study describes the systematic development of the DGT technique for nine current pesticides, selected to be representative of different classes with a wide range of properties, with two types of resins (HLB (hydrophilic-lipophilicbalanced) and XAD 18) as binding layer materials. The masses of pesticides accumulated by DGT devices were proportional to the deployment time and in inverse proportion to the thickness of the diffusive layer, in line with DGT theoretical predictions. DGT with both resin gels were tested in the laboratory for the effects of typical environmental factors on the DGT measurements. DGT performance was independent of the following: pH in the range of 4.7−8.2; dissolved organic matter concentrations <20 mg L −1 ; and ionic strength from 0.01 to 0.25 M, although it was slightly affected at 0.5 M in some cases. This confirms DGT as a sampler suitable for controlled studies of environmental processes affecting pesticides. Field applications of DGT to measure pesticides in situ in waters and controlled laboratory measurements on five different soils (prepared at fixed soil/water ratios) demonstrated DGT is a suitable tool for environmental monitoring in waters and for investigating chemical processes in soils.

Use of the Dynamic Technique DGT to Determine the Labile Pool Size and Kinetic Resupply of Pesticides in Soils and Sediments

“…D of ATR at 25 °C was taken as 5.67 × 10 −6 cm 2 s −1 , based on a previous study. 34 With increasing deployment time, the interfacial concentration of the labile analyte, C i , tends to decline due to depletion, which induces the desorption of the pesticide from the solid phase to resupply C i . This contributes to the flux of pesticides measured by DGT.…”

“…32,33 Validated DGT methods have been developed previously for this compound. 15,34 The purpose of this paper was to use DGT to investigate the in situ kinetic exchange of organic pollutants between solution phase and solid phase in two different environments. In the soil experiments, realistic agricultural treatment levels and reported contaminated levels of ATR were used, while an intact sediment core from a natural lake was used for in situ fine scale DGT measurements.…”

“…The soil concentration of ATR after application may typically be ∼3–6 mg kg –1 as a result of a normal application rate of 1.12–2.24 kg ha –1 . However, in some contaminated soils, following handling, spillages, accidents, etc., the concentration of ATR could be 100s to 1000s mg kg –1 , requiring remediation. − Its half-life in soils is usually reported as weeks to months, , but it has also been detected in soils >20 years after application. , Validated DGT methods have been developed previously for this compound. , …”

Trends in the use of passive sampling for monitoring polar pesticides in water

“…One solution to protect the hydrogel layers during deployments is the inclusion of a protective filter or membrane. A range of membranes (cellulose acetate, cellulose ester, Nylon and PES) has been evaluated and were found to suppress uptake [80,81]. Commenting on use of protective membranes, Guibal et al [70] proposed two points to consider before use: "1: target analytes and their potential interaction with the membrane (several compounds are often targeted and there is no "universally" inert membrane).…”

Smarter Sediment Screening: Effect-Based Quality Assessment, Chemical Profiling, and Risk Identification

“…12,14 Moreover, the concentrations obtained this way allow for subsequent comparison with environmental quality standards or effect concentrations for the water phase, which are much more readily available for water than for sediments. 15 A variety of methods for the determination of bioavailable contaminant concentrations in sediment has been described; 14,16−19 however, the manipulation of sediments (e.g., sieving and homogenization) that is required for application in toxicity tests and especially for bioavailability-based extractions leads to altered sediment characteristics, affecting layering and pore water concentrations of contaminants, 20 which can lead to over- or underestimation of sediment toxicity. 21−24 Hence, the use of undisturbed sediments in laboratory toxicity testing mimics the natural situation most closely, increasing the realism of the sediment quality assessment.…”