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

Abstract

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 SO42− (11∼4,127 μeq L−1). Consequently, Ca2+, Mg2+, SO42− 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 SO42−, 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.

Influence of Monsoonal Driving Factors on the Secondary Inorganic Aerosol over Ambient Air in Dhaka

“…These ratios were also higher than the reference value for seawater. A similar observation was reported in refs , , where the emission of Cl – , SO 4 2– , and NO 3 – was significantly affected by anthropogenic human activities. As shown in Figure c, the low Mg 2+ /Ca 2+ ratio may indicate the dissolution of calcite during the weathering process on Ca 2+ and Mg 2+ .…”

Riverine Hydrochemical Characteristics of a Typical Karst Urban Watershed: Major Ion Compositions, Sources, Assessment, and Historical Evolution

“…In addition, Mg 2+ , Ca 2+ , and HCO 3 – mainly come from the dissolution of dolomite and limestone, which is consistent with the main rock types in the study area. , However, there is no large exposure of sulfate rocks in the Nanming watershed. According to Zeng and Han, Ca 2+ and SO 4 2– account for the largest percentage in cations and anions, respectively. Since the study area is located in the center of the acid rain area in southwest China, SO 4 2– may be related to local atmospheric acid deposition .…”

“…48 Besides weathering processes and atmospheric precipitation, SO 4 2− in urban rivers usually comes from human activities (industrial wastewater, medical wastewater, domestic wastewater, etc.). 2,49 As the main wastewater receiver 46 Liu et al, 45 Han et al, 30 and Qin et al, 47 of Guiyang, the concentrations of SO 4 2− in the Nanming River may be influenced by natural weathering and human activities. According to Figure 2, the concentrations of SO 4 2− in the Nanming River are similar to the rainwater in the Guiyang and Wujiang Rivers, but there is the phenomenon that the concentrations of SO 4 2− in Guiyang groundwater were higher than those in other rivers.…”

“…54,55 However, there is no large exposure of sulfate rocks in the Nanming watershed. According to Zeng and Han, 46 Ca 2+ and SO 4 2− account for the largest percentage in cations and anions, respectively. Since the study area is located in the center of the acid rain area in southwest China, SO 4 2− may be related to local atmospheric acid deposition.…”

“…Figure 2. Piper diagrams showing anion and cation compositions in the Nanming River, Guiyang rainwater, Guiyang groundwater, Wujiang River, and Chongqing rivers (data reported by Zeng and Han,46 Liu et al,45 Han et al,30 and Qin et al,47 respectively).…”