IREES colloquium: Crop grey water footprints in China: the impact of pesticides on water pollution| Junjie Yi, PhD student

Speaker | Junjie Yi, PhD student at IREES.

Title | Crop grey water footprints in China: the impact of pesticides on water pollution.

Summary | Human water pollution is a significant challenge, especially in China, a rapidly growing economy. The grey water footprint (WF) is a tool for evaluating freshwater pollution. It expresses water pollution in volumetric units identifying the pollutant that theoretically needs most water to be diluted to accepted water quality standards. Previous agricultural grey WF studies focused on nitrogen (N) and phosphorus (P), while a limited number included pesticides. This study assesses grey WFs based on N and 1513 pesticide combinations of the twelve main crops and two crop categories grown in 31 Chinese provinces. Grey WFs, including the pesticide component, are far larger than grey WFs estimated before, dominating total WFs (green, blue, and grey). The total grey WF of agriculture in China (4,856×109 m3 year-1) is mainly determined by pesticides, while the grey WF related to N is 341×109 m3 year-1, a difference of fourteen.

The provinces Heilongjiang, Inner Mongolia, Hebei, Henan, and Shandong are hotspots contributing 37% to the total grey WF. A limited number of pesticides used for maize, vegetables, fruits and potato (Mancozeb a fungicide, Acetochlor a herbicide and Cypermethrin an insecticide) dominate total grey WFs, representing 80% of the total. Substituting the most polluting pesticides by pesticides with a similar function but lower grey WFs reduces water pollution by 20-50%. This study is the first national grey WF assessment related to pesticides in agriculture. It offers valuable insights not only to farmers but also to policymakers, providing a window of opportunity for the enhancement of water quality in China and beyond.