Characteristics and influencing factors of livestock residue nitrogen, phosphorus, and organic matter discharge and spatial distribution of pollution potential: Case study in the Yellow River Delta, China

Abstract

The Yellow River Delta, characterized by intense land-sea interactions, has a highly sensitive and fragile environment. Livestock residue, transported through runoff and infiltration, exacerbates soil and water contamination, posing a threat to offshore waters. Thus, mitigating the environmental risks associated with livestock residue in the delta is urgent. This study integrated field measurements and model analysis to provide new insights into livestock residue pollution control. It examined discharge characteristics in soil and aquatic environments and assessed the spatial distribution of pollution potential. In the Yellow River Delta, total nitrogen and total phosphorus levels in livestock residue exceeded the Ministry of Ecology and Environment’s limits by 3–6 times and 7.2 times, respectively. Large-scale breeding primarily reduced pollutant loads by increasing flushing. Shortening the distance between farms and rivers, along with adopting wet cleaning methods, mitigated nitrogen, phosphorus, and organic matter pollution risks. Compared to anaerobic digestion, aerobic composting reduced pollutant levels in manure but increased organic matter in slurry. Soil pollution was severe near farms, with total nitrogen and organic matter concentrations 2.0 and 2.1 times higher than those along the vertical transect from farms to rivers, while water pollution was relatively benign. High-risk non-point source pollution areas were concentrated in the northwest and south of the Yellow River Delta. Even low-risk waterways, such as the Yellow River and Xianxian Ditch, posed potential threats to the Bohai Sea. Optimizing breeding scale, flushing intensity, manure cleaning and treatment methods, and farm-river distances can effectively reduce pollution risks.