Water Footprint Analysis Of Winter Wheat-summer Maize Rotation System In North China Plain

Water scarcity has become a serious environmental problem in China.Agricultural production requires a huge amount of water and causes severe non-point source pollution.North China Plain is a major farming area in China,with severe contradiction between supply and demand of water resources.The main crop products in North China Plain are winter wheat and summer maize,and the major cropping system is winter wheat-summer maize rotation system.Water footprint is a comprehensive indicator,with capability to assess water consumption and water degradation by anthropogenic activities.In this study,a life cycle assessment-based water footprint analysis of winter wheat-summer maize rotation system in North China Plain was conducted.Six midpoint categories(i.e.carcinogens,non-carcinogens,freshwater ecotoxicity,water scarcity,aquatic eutrophication,and acidification)and two endpoint categories(i.e.human health and ecosystem quality)were selected in this study.Characteristic factors of each category were obtained from widely used and commonly recommended models and methods.The Chinese process-based life cycle inventory database was selected as the background inventory database.In 2017,the water footprint caused by 1 ton of winter wheat produced in North China Plain was 3.10×10-4?3.84×10-4 DALY in the human health category,and 34.04?40.28 PDF.m2.yr in the ecosystem quality category,respectively;the water footprint caused by 1 ton of summer maize was 1.82×10-4?2.26×10-4 DALY in the human health category,and 29.26?29.80 PDF.m2.yr,respectively.The midpoint categories water scarcity and carcinogens were the dominant contributor to human health category;midpoint category aquatic eutrophication accounted for the most percentage of ecosystem quality category results.Diesel production and irrigation were key processes to human health category;direct emission was the dominant contributor to aquatic eutrophication and ecosystem quality categories;diesel production and fertilizer production were key processes to carcinogens and freshwater ecotoxicity categories;diesel production was key process to-non-carcinogens category.Key substance analysis showed that chemical oxygen demand and total phosphorus were key substances to ecosystem quality;fresh water,chromium and arsenic were the main contributor to human health category.Sensitivity analysis indicated that 5%reduction of irrigation water or diesel could create environmental benefit of approximately 2%of human health damage reduction;by reducing 5%of pollutants emitted to water,ecosystem quality score decreased by over 3.8%.Improving irrigation efficiency,reducing fertilizer application amount and using efficient agricultural machines are effective measures to reduce direct and indirect water footprints.Utilization approaches of crop straw can bring considerable environmental benefits of water footprint reduction from the perspective of the whole life cycle.