Environmental Risks Assessment of Livestock and Poultry Non- Point Source Pollution in Shiyan City Based on Arable Land Carrying Capacity

Shiyan city was the core water source area of the middle route of the South-to-North Water Transfer Project, a comprehensive understanding of the current situation of livestock and poultry pollution and its potential threat to farmland would provide a basis for strengthening environmental risk control.

This paper used the livestock manure environmental risk assessment model to quantitatively analyze the source structure of livestock and poultry manure in different areas of Shiyan city in 2020, and the environmental risk from the perspective of the balance between planting and raising was comprehensively evaluated.

The total amount of livestock and poultry manure reached 306.85×10⁴ t in 2020, and it was mainly distributed in Yunyang district, Danjiangkou city and Fangxian county. COD production was the highest (57.00×10⁴ t), followed by TN (2.63×10⁴ t), and TP production was less (0.65×10⁴ t). The total equivalent standard pollution load was 15.532×10¹⁰ m³, and the source structure was obviously inconsistent in different regions. TP was the primary pollutant in livestock and poultry breeding, and its equivalent standard pollution load accounts for 41.68% of the total load, followed by TN with the pollution load rate of 33.85%, and the lowest equivalent standard pollution load rate of COD was 24.47%. Cattle was the primary source of non-point source pollution in livestock and poultry production in Shiyan city, contributing 49.47% to the total pollution load of the equivalent standard, followed by poultry (21.60%). According to the result of environmental pollution risk assessment, the load of animal excretion per hectare of arable land in Shiyan city was 10.15 t·hm^-2, the alarm value was 0.338 and the risk level was Ⅰ, indicating the environmental pollution was “no risk”. The load intensity of TN and TP was 0.09 and 0.02 t·hm^-2, respectively, and the environmental risk index was 1.023 and 1.223, respectively, but there were obvious spatial differences among regions. More than half of the whole city had the potential pollution risk of livestock and poultry breeding, among which Maojian district and Yunyang District were the most serious. With phosphorus as the measurement standard, the total amount of breeding in Shiyan city was close to saturation, the total amount of livestock and poultry must be reduced by 98.51×10⁴ pigs equivalent on the existing basis.

It was of great significance to maintain a reasonable scale of poultry breeding (≤441.00×10⁴ pigs equivalent) and take measures of pollutant abatement, in order to promote the balance of planting and breeding and orderly development of livestock and poultry breeding in Shiyan city.