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门和雷丁大学的土壤研究中心联合起来，解决植物从土壤溶液中吸收农药的问题。此次合作解决了2013年约克EUregPUF研讨会上提出的关于确定植物吸收因子（PUF）的标准化方案的问题，以及先正达征求建议书中确定的主题领域，即真菌、植物和昆虫的农药代谢、运输和吸收（包括建模和预测）以及土壤中化学物质的运动和根部吸收。目的建立水培溶液中植物吸收与土壤吸收的关系。通过量化场变率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等人开发的协议来确定水培溶液中具有不同物理化学特性的一系列农药的PUF。对于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，存在一些争论。为了提供更多的真实感，该方案将被略微改变，即沙子作为基质，以促进根系生长，并添加营养物质，以确保植物的活力。在溶渗仪/小块田地中，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。土壤孔隙水浓度将就地测量（PECAM和TECAM）和异地测量（离心技术）。测量将在距离植物一定距离的范围内进行，以确定根对固定土壤区域的影响，从而确定整个田地的综合价值。来自现场气象站的数据将用于计算植物蒸腾量，该蒸腾量乘以PUF可确定作物去除农药的质量。将比较田间和实验室的值，确定造成植物吸收主要差异的因素，并在建模阶段记录它们的可变性。在模拟农药在土壤中的命运时，有相当大的差距需要解决。例如;模型复杂性经常不合理，验证很少使用独立的数据集，并且在不知道其可变性的情况下使用单个参数值。通常，欧盟内部用于监管目的的模型，如PEARL和PELMO，使用单一参数来表示植物从土壤中提取水分以满足蒸散需求的结果。这种简单的方法没有考虑到土壤孔隙水的pH值（已知pH值会影响可电离化合物的吸收）以及吸附到根和转运到芽之间的分裂。特别令人感兴趣的是土壤吸收和农药转化参数，它们在农药淋溶通量中比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套件，并确定其中的敏感参数。来自实验研究的数据将用于确定现有的环境命运模型在多大程度上准确地代表田间土壤中所观察到的农药吸收情况。敏感性和不确定性分析将用于改进模型。项目结束后，先正达将拥有一个独立验证的系统，用于确定农药puf，并将根据现场数据对这些值的稳健性进行测试。后者将支持模型验证和校准工作，以提高先正达预测田间施用农药命运的能力。

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.