Sources and fate of glyphosate and aminomethylphosphonic acid in field crops soils

在过去的二十年里，全球大田作物农业中与耐草甘膦作物有关的草甘膦类除草剂(GBH)的使用量呈指数级增长。因此，在环境中普遍检测到草甘膦及其主要降解产物氨基甲基膦酸(AMPA)。这一DG研究计划的长期愿景侧重于了解草甘膦和AMPA在各种农业实践中的动态，并确定土壤中的生物和非生物成分在降解、再动员或积累这些化学物质方面所起的作用。最终，它的目的是强调保护性农业的最佳做法，限制GBH的使用，同时加强GBH的降解。目前的发现号研究计划是基于我的环境地球化学实验室开发的两项分析突破，即使用GC-ECD常规分析土壤和植物中的草甘膦和AMPA，以及使用新获得的LC-IRMS测量草甘膦和AMPA的化合物特定d13C。通过与农民的长期合作，将在整个计划中追求三个补充的短期研究目标：1)估计草甘膦和AMPA在土壤中的降解和持久性。为此，将进行实验室和露地实验，以跟踪农业作业中草甘膦和AMPA含量以及土壤中d13C特征的演变。2)分别用GBH和Biosolid评价土壤中草甘膦和AMPA的输入。废水生物固体改良剂可能是土壤中草甘膦和AMPA的来源之一。使用具有不同于生物固体中草甘膦和AMPA的草甘膦d13C特征的GBH批次的实验环境应允许区分这两种化合物由生物固体或GBH带到农业土壤中的相对动态。3)确定有机耕作系统中草甘膦和AMPA的来源。在长期建立的有机大田作物系统的土壤中检测到草甘膦和AMPA。对各种农场投入物(如粪便)中的草甘膦和AMPA d13C信号的测量将有助于确定这些化合物在有机耕作土壤中的来源和持久性。使用GBH控制免耕杂草，和/或回收城市生物固体作为肥料残留物，作为保持或恢复土壤功能、维持生物多样性和应对气候变化的管理措施被提出。只有当草甘膦和AMPA在土壤中的持久性很短时，这种关于大田作物系统可持续性的论点才是有效的。因此，了解这些化学物质在土壤中的消散机制是非常重要的。该计划将为HQP提供一个刺激的环境，将复杂的分析技术培训与对复杂和战略性农业环境问题的广泛理解相结合。

The usage of glyphosate-based herbicides (GBH) in association with glyphosate tolerant crops increased exponentially in field crop agriculture throughout the world for the past two decades. Consequently, glyphosate and its main degradation product, aminomethylphosphonic acid (AMPA), are ubiquitously detected in the environment. The long-term vision of this DG research program focuses on understanding the dynamics of glyphosate and AMPA with respect to various agricultural practices, and on identifying the role played by the soil biotic and abiotic constituents in degrading, remobilizing or accumulating, those chemicals. Ultimately, it is intended to highlight best practices in conservation agriculture limiting GBH usage while enhancing GBH degradation. The present Discovery research program is based on two analytical breakthroughs developed in my Environmental Geochemistry Laboratory, i.e. routinely analyzing traces of glyphosate and AMPA in soils and plants using a GC-ECD, and measuring compound-specific d13C of glyphosate and AMPA with a newly acquired LC-IRMS. Three complementary short-term research objectives will be pursued throughout the program with the benefit of long-term collaboration with farmers: 1) Estimate the degradation and persistence of glyphosate and AMPA in soils. To do so, laboratory and open field experiments will be conducted to follow along with agricultural operations the evolution of glyphosate and AMPA contents and d13C signatures in soils. 2) Evaluate the respective soil inputs of glyphosate and AMPA by GBH and biosolids. Wastewater biosolid amendments could represent a source of glyphosate and AMPA to soils. An experimental setting using GBH lots with a glyphosate d13C signature distinct from that of glyphosate and AMPA in biosolids should allow distinguishing the relative dynamics of both compounds brought to agricultural soils either by biosolids or by GBH. 3) Identify the source of glyphosate and AMPA in organic farming systems. Glyphosate and AMPA are detected in soils of long-established organic field crop systems. Measurements of glyphosate and AMPA d13C signatures in various farm inputs such as manure will allow identifying the sources and persistence of these compounds in organic farming soils. Using GBH to control weeds with no-till practices, and / or recycling municipal biosolids as fertilizer residual are presented as management practices keeping or restoring soil functions, maintaining biodiversity and fighting climate change. This argument towards sustainability of field crops systems is only valid if glyphosate and AMPA's persistence in soil is short. Understanding the mechanisms responsible for the dissipation of these chemicals in soils is thus of utmost importance. The program will offer a stimulating environment for HQP, combining training on sophisticated analytical techniques with the broad understanding of complex and strategic agri-environmental issues.