Understanding pesticide dynamics at the catchment scale for the management of drinking water reservoirs

农田上使用的杀虫剂是周围地区，特别是当地水道的污染源。在降雨期间，农药通过地表径流从施肥区向河流输送，并附着在被侵蚀的沉积物上。在这样的当地水道向饮用水水库供水的地方，各种不同的杀虫剂最终会进入水库。然而，杀虫剂到达水库的时间和浓度在全年都是不同的，这既取决于降雨量的变化，也取决于田间施药的时间和类型。由于目前没有立法要求记录田间农药的使用情况，威塞克斯水务公司等公司没有关于集水区内影响其水库内农药水平的季节性动态的信息。因此，监测和管理水库内的杀虫剂水平是一个严重的问题，对公众健康具有重要影响。该项目将采用一种以实地为基础的方法，在这种方法中，集水、水文和侵蚀的反应将以分级办法为特点。研究地点将是杜利集水区，这是威塞克斯郡的低地农业集水区之一，也是最容易受到杀虫剂污染的地区之一。这项工作的第一部分将涉及一项试点研究，将从河流的水和沉积物样本中识别与水库中发现的类别有关的持久性农药类别。任何现有的关于农药、土地利用和水文学的数据也将被整理和综合，以便更广泛地了解流域内的农药动态。研究的第二部分将在12个月内进行，包括每两周对河水和河床沉积物进行空间采样。韦塞克斯已经每两周对水库水进行例行采样。将对水和沉积物样本进行分析，以确定在试点研究中确定的与水库农药水平有关的农药类别。该项目的第三部分将以前一年收集的数据为基础，以确定农药反应的集水区“热点”，并在6个月的时间内，在这些数据中更详细地描述农药运输的特征，特别是在个别降雨事件和个别农场系统规模内。该项目的一个特别创新的方面是比较了溶解和沉积物结合的农药在集水过程中的输送机制。目前，Wessex Water没有关于沉积物结合杀虫剂在其集水区内所起作用的信息，但这种成分通过解吸机制可能在最初从田间动员很长时间后，成为水库中农药污染的持续来源，这一点具有严重影响。这些数据的综合将提供与农药运输机制有关的集水动态的迫切需要的详细了解，以及这些机制如何影响Durleigh饮用水水库内的农药动态。这一理解将导致更好的水库管理做法，并最终在农场一级设计缓解措施。该项目将不同的研究方向结合在一起，形成了一个创新的、可实现的博士培训课程，并对紧迫的污染和水质问题进行了大量的实际应用。这名学生将受益于布里斯托尔大学和韦塞克斯水务大学的导师提供的不同专业知识。学生将受益于与威塞克斯水务公司建立联系，以及在威塞克斯大学提供的培训机会。水样的农药分析将在威塞克斯实验室进行，学生将接受分析技术培训。

Pesticides applied on farmland are a source of pollution for the surrounding areas and in particular for local watercourses. During rainfall events pesticides are transported away from the area of application towards the rivers via surface runoff and attached to eroded sediment. Where such local watercourses supply water to drinking-water reservoirs, a variety of different pesticides ultimately end up in the reservoirs. However, the timing of pesticide arrival and their concentrations in the reservoir, vary throughout the year as a function of both rainfall variability and the timing and type of pesticide application on fields. Because at present there is no legislative requirement to record pesticide application on fields, companies such as Wessex Water have no information on the seasonal dynamics within the catchment that will affect the pesticide levels within their reservoirs. Hence, monitoring and managing pesticide levels within the reservoirs are a serious problem with important implications for public health. The project will adopt a field-based methodology in which the catchment hydrological and erosion responses will be characterised within a hierarchical approach. The study site will be the Durleigh catchment which is one of Wessex's lowland agricultural catchments and one which is most prone to pollution from pesticides. The first part of the work will involve a pilot study in which classes of persistent pesticides will be identified from water and sediment samples from the rivers in relation to classes found in the reservoir. Any existing available data on pesticides, land use and hydrology will also be collated and synthesised for a broader historical understanding of the pesticide dynamics within the catchment. The second part of the study will be carried out over 12 months and will involve spatial sampling of river water and riverbed sediment every two weeks. Wessex already carries out routine sampling of the reservoir water every two weeks. Both water and sediment samples will be analysed for the classes of pesticides identified in the pilot study and related to the reservoir pesticide levels. The third part of the project will build on the data collected in the previous year to identify catchment 'hotspots' of pesticide response and, over a 6-month period, carry out within those a more detailed characterisation of pesticide transport, particularly within individual rainfall events and at the individual farm system scale. A particularly innovative aspect of the project is the comparison between the dissolved and sediment-bound pesticide transport mechanisms in relation to catchment processes. Currently, Wessex Water has no information on the role of sediment-bound pesticides within their catchments but there are serious implications of the potential for this component, through desorption mechanisms, to act as a sustained source of pesticide pollution in the reservoir long after their initial mobilisation from the fields. The synthesis of these data will provide a much needed detailed understanding of catchment dynamics in relation to pesticide transport mechanisms and how these affect the pesticide dynamics within the Durleigh drinking-water reservoir. This understanding will lead to better management practices of the reservoir and ultimately to the design of mitigation measures at the farm level. The project combines different strands of investigation into an innovative and achievable course of doctoral training with great practical application to a pressing pollution and water-quality problem. The student will benefit from the different expertise offered by the supervisors both at the University of Bristol and Wessex Water. The student will benefit from establishing contacts with Wessex Water as well from the training opportunities offered at Wessex. The pesticide analyses of the water samples will be carried out in the Wessex labs and the student will have training in analytical techniques.