Nitrogen concentration of rainfall in Dalian, China

Abstract

Wet atmospheric deposition samples were collected in rainy days from 2004 to 2008 in Dalian of Liaoning Province, Northeast of China, which were measured by rain gauge and analyzed for total inorganic nitrogen (TIN) concentration. The mean annual volume of rainfall was from 438.25 to 850.94 mm, and the concentration of TIN was 3.47 mg/L, which showed negative correlation with the volume of rainfall. The order of TIN concentration among seasons was: winter > spring > autumn > summer. Increased use of fertilizers in agricultural areas or widespread use of private transportation led to the increase of TIN fluxes. Variations of TIN concentration among years were significantly different; the annual precipitation TIN inputs were positively related to the volume of rainfall and were surprisingly high with the deposition flux ranging from 10.24 to 25.17 kg N/(hm2·a). The maximum mean annual flux was 25.17 kg N/(hm2·a) which is equal to 53.94 kg N/(hm2·a) usage of CO(NH)2 (an amount that could have caused changes in terrestrial life). The fluxes of TIN also showed a different seasonal fluctuation during the course of our study, and we found that majority of TIN deposition occurred in summer (from June to August), which accounted for 56.44% of total annual precipitation and 40.06% of total annual deposition flux. Annual TIN fluxes decreased considerably after the rainy season and reached the lowest level (1.39 kg N/(hm2·a)) in winter.