Influence of meteorological variables and human activities on precipitation chemistry in the Guanzhong Plain, Northwest China

Precipitation chemistry can reflect the impacts of both anthropogenic and natural sources on air quality and provide insights into material cycles between the Earth's surface and atmosphere. We explored the chemical characteristics of precipitation in relation to meteorological and environmental factors in Weinan, a key hub for agriculture and ecological protection on the Guanzhong Plain in Northwest China. Precipitation samples (n = 291) collected in Weinan from 2021 to 2022 were analyzed for their chemical compositions using chemometric analysis, correlation analysis, the positive matrix factorization (PMF) model, and the backward trajectory model. The findings revealed that the primary ions in the precipitation were Ca²⁺, NH₄⁺, SO₄²⁻ and NO₃⁻. The concentrations of most ions were higher in winter and lower in summer due to changes in precipitation amount, humidity, PM_2.5 and PM₁₀. The PMF analysis identified six ion sources in precipitation, including crustal sources (24.9 %), secondary formation (20.7 %), waste incineration (16 %), marine sources (15 %), industrial emissions (11.8 %), and biomass burning (11.5 %). The backward trajectory analysis showed that water vapor transport varies seasonally and is primarily influenced by westerly, monsoonal, and regional circulations. The westerly circulation predominantly affects ion concentrations by transporting dust and anthropogenic pollutants to Weinan. The monsoonal circulation carries large amounts of water vapor and contributes the most to precipitation (54.38 %). This study reveals the impacts of natural factors, human activities, and water vapor sources on precipitation chemistry and offers decision support for air quality management and pollution control in Northwest China.