E. Capri

A monitoring programme for 1,3-dichloropropene and metabolites in groundwater in five EU countries

BACKGROUND 1,3 Dichloropropene (1,3-D) is a preplanting soil fumigant for the control of cyst and free-living nematodes and is currently undergoing a resubmission under Annex 1 listing of Directive 91/414/EEC. The characteristics of 1,3-D are such that the risk of it or its soil metabolites leaching through the soil profile cannot be excluded. As such, groundwater monitoring programmes were established in five EU countries representing a wide range of agricultural, climatic and hydrogeological situations, covering a range of groundwater vulnerability scenarios. All monitoring was conducted in areas where there has been historical use of 1,3-D. RESULTS Over 5000 groundwater samples were analysed for the presence of 1,3-D and its metabolites over a 2 year period. Almost all analyses (for parent and metabolites) yielded concentrations of <0.1 microg L(-1). There were just two detections of >0.1 microg L(-1) (0.12 microg L(-1) and 0.4 microg L(-1)) for the 3-chloroacrylic acid metabolite in shallow groundwater samples of the alluvial gravels of the River Tiétar in the Caceres region of Spain. CONCLUSION Groundwater monitoring programmes have been conducted in the EU in five countries. These have demonstrated that there is negligible contamination of groundwater with 1,3-D or its metabolites across a range of agroclimatic regions where 1,3-D is known to have been used for a number of years. Local scientific knowledge of geological features, hydrology, agricultural practice and specific local issues was essential to the conduct of the study.

Pesticide soil transport models: Model comparisons and field evaluation

Using an experimental data set obtained in a field trial in Italy, three models forecasting pesticide behaviour in root/vadose zone of the soil were tested. PRZM, BAM and LEACHM were used simulating metolachlor and atrazine at different depth of the soil. Input model parameters for the chemodynamic herbicide properties, were obtained from literature data base while weather and soil data were derived from the experimental field. In all cases the results from the models agreed with the observed data in particular for the top soil. In the 30–50 cm ‐ soil depth, the measured and predicted concentrations were much variable and they agreed only in few cases within a magnitude factor of 5–10. The differences between the models were measured mainly in soil hydrological balance.

Higher-tier assessment of the potential for groundwater issues due to the use of 1,3-D soil fumigant; evaluation of the active ingredient, metabolites and potentially related chlorinated compounds.

BACKGROUND 1,3-Dichloropropene (1,3-D, CAS No. 542-75-6) is a broad-spectrum soil fumigant used to control numerous species of soilborne plant-parasitic nematodes. 1,3-D consists of two isomers, (Z)- and (E)-1,3-D. There are a number of low-level chlorinated compounds that could potentially be produced as a part of the 1,3-D manufacturing process. 1,3-D and its metabolites, as well as potentially related chlorinated compounds, represent potential groundwater contaminants. RESULTS This study has investigated the hydrolytic stability, under biotic and abiotic conditions in the laboratory, of an extensive representative list of 1,3-D and potentially related chlorinated compounds in order to predict their environmental fate. All of these compounds showed intrinsic hydrolytic instability under both abiotic and biotic test conditions. Furthermore, a monitoring programme was carried out. Twenty-five wells were monitored in five Italian regions characterised by historical and existing use of 1,3-D. The parent compound, its two major metabolites and potentially related chlorinated compounds were not detected in the well water at > 0.1 µg L(-1) at any sampling location. CONCLUSION The soil fumigant (E,Z)-1,3-D, its metabolites and potentially related chlorinated compounds constitute a low risk to groundwater.