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Assessment Of Pesticides Contamination In A Catchment By Polar Organic Chemical Integrative Sampler

Congress: 2015
Author(s): Zulin Zhang, Mark Osprey, Christine Kerr
The James Hutton Institute1

Keyword(s): Sub-theme 2: Surface water and groundwater,
AbstractIntroduction
Every year 3 million tons of pesticides are used for crop protection worldwide, which if not used would result in a 40% decrease in food production (CropLife, http://www.croplifeamerica.org/). However, pesticide use also raises a number of environmental concerns. Over 95% of pesticides reach a destination other than their target species, including non-target species, air, soil and water (Miller 2004). Pesticides have both beneficial and adverse effects. Assessment of the relative risks and benefits requires understanding of the transport and fate of these chemicals in the environment. Passive samplers (including integrative or kinetic and equilibrium samplers) are relatively new emerging tools for sampling micro-pollutant in waters. Since the appearance of the first passive sampler for surface waters, these tools have quickly become widespread for micro-pollutant monitoring and water quality assessment. In this study, the main objective is to employ passive sampling technique (e.g. polar organic chemical integrative sampler, POCIS) for seasonal assessment of pesticides contamination in a priority catchment (Ugie catchment) of Northeastern Scotland (SEPA 2010). Also, it is to assess how the pesticides transport after their usage and entering the aquatic environment.
Method and Materials
Monthly passive sampling (POCIS) and spot sampling (water) were conducted at 3 sites (North Ugie, South Ugie and Inverugie) from the Ugie River of Northeast Scotland. Both water and POCIS were sampled in triplicate. Water samples were extracted by Solid Phase Extraction (SPE) and POCIS samplers were extracted by ethyl acetate. A broad range of pesticides (Metaldehyde, Isoproturon, Simazine, Chlorotoluron, Atrazine, Epoxiconazole, Chlorpyrifos, Cypermethrin and Permethrin) with different physico-chemical properties (LogKow: 0.12-6.1) were determined by GC-MSD (Lefebver 2013; Zhang et al., 2014). Water depth, temperature, dissolved oxygen and pH values were measured when sampling in the field.
Results and Discussion
Overall, the results showed that Chlortoluron (CTU) was the most significant pesticide detected in the Ugie River, Scotland (CTU: Chlortoluron (CTU) is an extensively used herbicide to kill weed and it is frequently detected in the catchment (SEPA 2010). It is interesting to find that both spot and passive monitoring data suggested that there are peak concentrations of CTU in November, which is associated with increased rainfall in November. In general, CTU would be largely applied in the agriculture field in summer (e.g. June-August) to kill weeds. This retardant runoff in autumn-winter (October-December) could be due to (1) CTU tends to retain in the soils particularly at the very beginning of use, this is also suggested by our laboratory soil column experiments which showed that approximate over 90% of CTU retains in the soils after 100 hours running. And the data suggested that the pesticide CTU primarily stays in the top layer of soils. (2) In summer, there is not much rainfall to cause pesticides leaching off. With increased rainfall in November, it results in surface runoff. However, in the following year (winter-spring), CTU levels fell whilst rainfall remained high. This is due to a lack of further CTU inputs in the winter and spring time.
Conclusion
Future work is needed to investigate different pesticides transfer in the soil-water system with long time experiment, to further understand different climate changes (e.g. rainfall) and soil properties (e.g. structure) effect on the pesticides behavior and their potential risk to the water quality and food chain risk.
Acknowledgements This work was funded by the Scottish Governments' Rural and Environment Research and Analysis Directorate.
1. CropLife. Benefits of Pesticides and Crop Protection Chemicals: http://www.croplifeamerica.org/.
2. Lefebvre T. (2013) Determination of pesticides in Waters and Soils/sediments by GC-MS. Internship Report.
3. Miller GT. (2004) Sustaining the Earth, 6th edition. Thompson Learning, Inc. Pacific Grove, California. Chapter 9: 211-216.
4. Scottish Environment Protection Agency (SEPA) (2010) Diffuse Pollution Priority Catchment: Technical Summary (River Ugie).
5. Zhang ZL, Lefebvre T, Kerr C, Osprey M. (2014, Sub) Simultaneous extraction and determination of various pesticides in environmental waters.
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