Analysis of Pollution Sources in Erhai Lake Based on Principal Component Analysis and Positive Matrix Factorization

Purpose To analyze the sources of pollutants in Erhai Lake and quantify their contributions, providing a scientific basis for watershed water environment protection.

Methods Based on the water quality monitoring data of Erhai Lake for many years, the pollution characteristics were analyzed, and the principal component analysis (PCA) and positive matrix factorization (PMF) were used to analyze the pollution sources and their contribution rates.

Results The comprehensive nutritional status index of Erhai Lake showed a fluctuating upward trend from 2015 to 2021. The nutritional status index in the rainy season was significantly higher than that in the dry season, and it was at the maximum in September and October. PCA and PMF source analysis results showed that the main reasons for water pollution in Erhai Lake, sorted from the highest contribution rate to the lowest, were agricultural non-point source, livestock and poultry breeding, domestic sewage and meteorological factor.

Conclusion Erhai Lake is in a mesotropher, but the overall trend is trophic. The pollution is mainly concentrated in rainy season, and the pollution prevention and control in the flood season should be strengthened. The main pollution source is agricultural non-point source, and the treatment of agricultural non-point source system should be strengthened to form a whole process prevention and control system of “source reduction-process interception-nutrient reuse-end restoration”. In the source section, the focus is on adjusting the agricultural planting structure, transforming the mode of agricultural production, improving the efficiency of plant nutrient utilization, and the realization of green and high-quality development of agriculture in the basin.