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

农田使用的农药是对周边地区的污染源，特别是对当地水道的污染源。在降雨期间，农药通过地表径流从施用区域转移到河流中，并附着在被侵蚀的沉积物上。在这些地方水道为饮用水库供水的地方，各种不同的农药最终会进入水库。然而，农药到达的时间及其在水库中的浓度在一年中因降雨量变化和田间施用农药的时间和类型而有所不同。由于目前没有法律要求记录田间农药的使用情况，像Wessex Water这样的公司没有关于集水区季节性动态的信息，这些信息会影响水库中的农药水平。因此，监测和管理水库内的农药水平是一个严重问题，对公众健康具有重要影响。该项目将采用一种基于实地的方法，在这种方法中，流域水文和侵蚀反应将在分层方法中得到表征。研究地点将是杜利集水区，这是威塞克斯的低地农业集水区之一，也是最容易受到农药污染的地区之一。这项工作的第一部分将涉及一项试点研究，从河流的水和沉积物样本中确定持久性农药的类别，并将其与水库中发现的类别进行比较。还将整理和综合有关农药、土地利用和水文的任何现有可用数据，以便对流域内的农药动态有更广泛的历史了解。研究的第二部分将持续12个月，包括每两周对河水和河床沉积物进行空间采样。威塞克斯已经每两周对水库水进行常规采样。将对水和沉积物样本进行分析，以确定试点研究中确定的农药类别，并与水库农药水平有关。该项目的第三部分将以前一年收集的数据为基础，确定农药反应的流域“热点”，并在6个月的时间内，在这些区域内对农药运输进行更详细的描述，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与集水区过程有关的溶解和沉积物结合的农药运输机制。目前，威塞克斯水务公司没有关于沉积物结合农药在其集水区中的作用的信息，但这一成分的潜在严重影响是，通过解吸机制，在它们最初从田间动员后很长一段时间内，作为水库中农药污染的持续来源。这些数据的综合将提供与农药运输机制有关的集水区动态以及这些机制如何影响Durleigh饮用水水库内农药动态的非常需要的详细了解。这种认识将导致对水库进行更好的管理，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，形成一个创新的、可实现的博士培训课程，并在解决紧迫的污染和水质问题方面有很大的实际应用。该学生将受益于布里斯托尔大学和威塞克斯沃特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威塞克斯提供的培训机会。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方面的培训。

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.