Spatial and Temporal Variation of Inorganic Nitrogen Wet Deposition to the Yangtze River Delta Region, China
2009
Zhao, Xu | Yan, Xiaoyuan | Xiong, Zhengqin | Xie, Yingxin | Xing, Guangxi | Shi, Shulian | Zhu, Zhaoliang
Two-year (June 2003-May 2005) precipitation samples were collected from three monitoring sites with similar economy development level in the Yangtze River Delta Region of China to investigate the spatial-temporal variation of inorganic N wet deposition. The results showed that the Yangtze River Delta Region had higher inorganic N wet deposition than the northwestern, northern, or southern China. There was spatial variation of inorganic N wet deposition. The positive relationship between inorganic N deposition and precipitation suggested that rainfall amount might be an important factor influencing the wet deposition of inorganic N. Deposition of inorganic N occurred mainly in the spring and summer season (March-August; 70% of the annual total), which was in accord with seasonal distribution of precipitation. However, a negative logarithmic relation between rainfall and inorganic N concentration in rainwater indicated the dilution effect of rainwater on inorganic N concentration. Distinguished variation of NH₄ ⁺/NO₃ ⁻ ratio in wet deposition existed in the different time scale. NH₄ ⁺/NO₃ ⁻ ratio evidently decreased from 6 in 1980s to 1.2 in 2003/2005 and greatly varied between 0.3 and 9.9 within a year. NH₄ ⁺/NO₃ ⁻ ratio peaked in accordance with nitrogen-fertilizing time during crop growing season. Annual alternate appearance of the ¹⁵N-enriched and ¹⁵N-depleted periods coincided with the temporal variation of NH₄ ⁺/NO₃ ⁻ ratio, which was closely related to the timing of fertilization and seasonal climate changes, suggesting the effect of NH₄ ⁺ sources in the wet deposition.
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