Rainwater chemistry observation in a karst city: variations, influence factors, sources and potential environmental...

The rainwater chemistry and related air contaminants are used to investigate the rainwater ions sources, variations, and influence factors from 2012 to 2014 in Guiyang city (the typical karst urban area of Southwest China). According to temporal rainwater ion concentrations, the obvious variations were presented in the study period, such as Ca²⁺ (125∼6,652 μeq L^-1) and SO₄ ^2- (11∼4,127 μeq L^-1). Consequently, Ca²⁺, Mg²⁺, SO₄ ^2- and Cl^- are considered as the leading ions. Three critical influencing factors of rainwater ions concentrations, including sources variations, rainfall amount and long-distance migration (rainfall amount > 100 mm) are identified. Based on the typical ionic ratios, source identification suggested that anthropogenic inputs mainly contributed to F^-, NO₃ ^- and SO₄ ^2-, while the dusts (crustal sources) are the primary sources of Mg²⁺, Ca²⁺ and K⁺. Cl^- Enrichment in long-distance transport is the main contributor of Cl^-. According to the observation of high level of total wet acid deposition, the more detailed spatio-temporal monitoring of rainfall-related acid deposition (particularly sulfur deposition) is required to understand its potential environmental effects in the aquatic ecosystem of the earth surface.