Quantifying and understanding uptake of plant protection products from soil into plants

该项目将先正达的产品安全部和雷丁大学的土壤研究中心结合在一起，以解决植物从土壤溶液中吸收农药的问题。这项合作解决了2013年在约克举行的EUregPUF研讨会上提出的关于确定植物吸收因子(PUF)的标准化协议和先正达呼吁确定的主题领域的建议，即农药在真菌、植物和昆虫中的新陈代谢、运输和吸收(包括建模和预测)以及土壤中化学物质的移动和根吸收。目的是建立植物在水培溶液中的吸收与在土壤中的吸收之间的关系。通过量化田间变异性和简化模型结构来改进环境命运模型。实验该项目将使用Sweeney等人开发的协议。从水培溶液中测定一系列具有不同理化特性的农药的PUF。关于PUF是否可以大于或小于1，以及水培系统是否是植物从土壤中吸收的现实替代品，还存在一些争论。协议将略微修改，以提供更现实的情况，即以沙子为基质，通过添加养分来促进根的生长，以确保植物的生命力。在蒸渗仪/小块田块中，将检查选定的有效成分，以测量植物在土壤中的吸收和命运。土壤孔隙水浓度将在现场(PECAM和TECAM)和非现场(离心机技术)进行测量。这些测量将在离植物一定距离的范围内进行，以确定根部对固定土壤区域的影响，从而确定整个田地的整体值。来自现场气象站的数据将被用来计算植物蒸腾作用，当乘以PUF时，将确定作物去除的杀虫剂的质量。将比较田间和实验室的值，并确定导致植物吸收的主要差异的因素，它们的变异性将被记录在模拟阶段。模拟在模拟土壤中的农药的命运时，有相当大的差距需要解决。例如，模型的复杂性经常是不合理的，验证很少使用独立的数据集，并且使用单个参数值时不知道它们的可变性。通常，欧盟内部用于监管目的的模型，如PEAR和PELMO，使用单个参数来表示由于从土壤中提取水分以满足蒸散需求而导致的植物吸收。这种简单的方法没有考虑土壤孔隙水的pH值(众所周知，pH值影响可电离化合物的吸收)，也没有考虑吸收到根和转运到地上部之间的分裂。特别令人感兴趣的是土壤吸附和农药转化参数，这些参数比农药淋洗通量中的水流参数敏感一个数量级。该项目将使用现有的先正达模型组，并确定其中的敏感参数。实验研究的数据将被用来确定现有的环境命运模型在多大程度上准确地反映了田间土壤中观察到的杀虫剂吸收情况。将使用灵敏度和不确定度分析来改进模型。结果在项目结束时，先正达将拥有一个独立验证的农药PUF测定系统，这些值的稳健性将根据田间数据进行测试。后者将为模型验证和校准工作奠定基础，以提高先正达预测田间应用杀虫剂命运的能力。

This project brings together the Product Safety Division of Syngenta and Soil Research Centre at the University of Reading to address the uptake of pesticides by plants from soil solution. The collaboration addresses issues raised at the EUregPUF workshop, York, 2013 regarding a standardized protocol for the determination of the plant uptake factor (PUF) and subject areas identified in the Syngenta call for proposals i.e. Pesticide metabolism, transport and uptake in fungi, plants and insects (inc.modelling & prediction) and Movement of chemicals in soil and uptake into roots.AimsTo establish the relationship between plant uptake in hydroponic solution against that in soil.To improve environmental fate models by quantifying field variability and streamlining model structure.ExperimentalThe project will use the protocol developed by Sweeney et al. to determine the PUF of a range of pesticides with varying physicochemical characteristics from hydroponic solution. There is some debate whether the PUF can be greater or less than 1 and whether hydroponic systems are a realistic surrogate for uptake by plants from soil. The protocol will be marginally altered in order to provide more realism i.e. sand as the substrate to improve root growth with nutrients added to ensure plant vitality.In lysimeters/small field plots selected active ingredients will be examined to measure the plant uptake and fate in soil. Soil pore water concentration will be measured both in-situ (PECAM and TECAM) and ex-situ (centrifuge technique). The measurements will be taken at a range of distances from the plant to determine the root influence across a fixed area of soil enabling an integrated value for a whole field to be determined. Data from an on-site meteorological station will be used to calculate the plant transpiration which when multiplied by the PUF determines the mass of pesticide removed by the crop.The field and laboratory values will be compared and the factors responsible for the primary differences in plant uptake identified, their variability will be recorded for the modelling phase.ModellingThere are considerable gaps to be addressed when modelling the fate of pesticides in soils. For example; model complexity is frequently not justified, the validation rarely uses an independent data set and single parameter values are used without knowledge of their variability. Frequently, models used for regulatory purposes within the EU such as PEARL and PELMO use a single parameter to represent plant uptake as a result of abstraction of water from soil to satisfy evapotranspiration demand. Such a simple approach does not take into consideration the pH of soil pore water (pH is known to affect uptake of ionisable compounds) and the split between adsorption to roots and translocation into shoots. Of particular interest are soil sorption and pesticide transformation parameters which are an order of magnitude more sensitive than water flow parameters in pesticide leaching fluxes.The project will use the existing Syngenta suite of models and determine the sensitive parameters within these. The data from the experimental studies will be used to establish the extent to which existing models of environmental fate accurately represent the observed uptake of pesticides from soil in the field. Sensitivity and uncertainty analyses will be used to improve the models.OutcomeAt the conclusion of the project Syngenta will have an independently validated system for the determination of pesticide PUFs and the robustness of these values will have been tested against field data. The latter will underpin a model validation and calibration exercise to improve Syngenta's capability to predict the fate of field applied pesticides.