Chemical characteristics, deposition fluxes and source apportionment of precipitation components in the Jiaozhou Bay, North China

To systematically illustrate the chemical characteristics, deposition fluxes and potential sources of the major components in precipitation, 49 rainwater and snow water samples were collected in the Jiaozhou Bay from June 2015 to May 2016. We determined the pH, electric conductivity (EC) and the concentrations of main ions (Na+, K+, Ca2 +, Mg2 +, NH4+, SO42 −, NO3−, Cl− and F−) as well as analyzed their source contributions and atmospheric transport. The results showed that the precipitation samples were severely acidified with an annual volume-weighted mean (VWM) pH of 4.77. The frequency of acid precipitation (pH < 5.6) reached up to 71.4%, and the mean EC value was relatively higher at 64.9 μS cm− 1, all of which suggested a higher atmospheric pollution level over the Jiaozhou Bay. Surprisingly, NH4+ (40.4%), which is higher than Ca2 + (29.3%), is the dominant species of cations, which is different from that in most areas of China. SO42 − was the most abundant anions, and accounted for 41.6% of the total anions. The wet deposition fluxes of sulfur (S) was 12.98 kg ha− 1 yr− 1. Rainfall, emission intensity and long-range transport of natural and anthropogenic pollutants together control the concentrations and wet deposition fluxes of chemical components in the precipitation. Non-sea-salt SO42 − and NO3− were the primary acid components while NH4+ and non-sea-salt Ca2 + were the dominating neutralizing constituents. The comparatively lower rainwater concentration of Ca2 + in the Jiaozhou Bay than that in other regions in Northern China likely to be a cause for the strong acidity of precipitation. Based on the combined enrichment factor and correlation analysis, the integrated contributions of sea-salt, crustal and anthropogenic sources to the total ions of precipitation were estimated to be 28.7%, 14.5% and 56.8%, respectively. However, the marine source fraction of SO42 − may be underestimated as the contribution from marine phytoplankton was neglected. Therefore, the precipitation components in the Jiaozhou Bay present complex chemical characteristics under the combined effects of natural changes and anthropogenic activities.