摘要:以重庆市近郊中梁山槽谷为研究区，利用气象站和沉降仪获取2017年5月-2018年4月的大气无机氮、硫沉降数据和降水δ¹⁵N-NO₃^-、δ¹⁸O-NO₃^-和δ³⁴S-SO₄^2-、δ¹⁸O-SO₄^2-数据，通过离子浓度比值、同位素值和气团后向轨迹探讨了研究区大气中氮、硫沉降变化特征及其来源。结果表明：（1）大气DIN总沉降量为19.99 kg/hm²，干、湿沉降量分别占11%和89%；大气S总沉降量为32.62 kg/hm²，干、湿沉降量分别占13%和87%。大气氮、硫湿沉降量与降水量均呈正相关（n=12，P < 0.01），氮、硫干湿沉降量具有明显的季节差异。（2）降水NH₄⁺-N/NO₃^--N比值介于0.45-2.2之间，雨季（5-10月）NH₄⁺-N/NO₃^--N>1，旱季（11-次年4月）NH₄⁺-N/NO₃^--N<1，表明雨季氮主要来源于农业源，旱季来源于工业和交通源；降水NO₃^-/SO₄^2-比值介于0.1-1.25之间，平均值为0.63，表明硫来源以固定污染源（燃煤）为主。（3）大气降水δ¹⁵N-NO₃^-、δ¹⁸O-NO₃^-值分别为-3.8‰-3.9‰（平均值为0.4‰±2.6‰）和58.7‰-98.7‰（平均值为76.1‰±14.3‰），夏季偏负，冬季偏正；降水δ³⁴S-SO₄^2-和δ¹⁸O-SO₄^2-变化范围分别为1.3‰-3.2‰（平均值为2.3‰±1‰）和5.3‰-8.5‰（平均值为7.1‰±1.6‰），大气降水中NO₃^-和SO₄^2-主要来源于当地的化石燃料燃烧，同时受到周边污染物的远距离传输影响。（4）气团后向轨迹表明影响研究区氮、硫干湿沉降来源的主要因素是东亚季风，北东-南西走向的川东平行岭谷大地貌格局加剧了季风的影响。



Abstract:Atmospheric inorganic nitrogen and sulfur deposition samples were collected from May 2017 to April 2018 at the Zhongliang mountain trough valley in the suburbs of Chongqing. The ratio of ionic concentrations, isotope value, and air mass backward trajectories model were used to trace the sources of atmospheric nitrogen and sulfur. Our analyses showed that:(1) During the monitoring period, total atmospheric DIN deposition flux was 19.99 kg/hm², among it the dry and wet deposition flux accounted for 11% and 89%, respectively. The total atmospheric S deposition flux was 32.62 kg/hm², among it the dry and wet deposition accounted for 13% and 87%, respectively. The atmospheric N and S dry and wet deposition flux exhibited clear seasonal changes, which were positively correlated with precipitation (n=12, P < 0.01).(2) The ratio of NH₄⁺-N/NO₃^--N was from 0.45 to 2.2, being greater than 1 in the rainy season (May to October) and less than 1 in the dry season (November to April of the following year), indicating that the sources of nitrogen were mainly from agricultural activities in the rainy season, and from industrial and traffic sources in the dry season. The ratio of NO₃^-/SO₄^2- was from 0.1 to 1.25, with a mean value of 0.63, indicating that the source of sulfur was mainly from coal burning. (3) The δ¹⁵N-NO₃^- and δ¹⁸O-NO₃^- values of rainwater were characterized by negative values in summer and positive values in winter, ranging from -3.8 to 3.9‰ (mean 0.4‰±2.6‰) and 58.7 to 98.7‰ (mean 76.1‰±14.3‰), respectively. The δ³⁴S-SO₄^2- and δ¹⁸O-SO₄^2- values of rainwater ranged from 1.3 to 3.2‰ (mean 2.3‰±1‰) and 5.3‰ to 8.5‰ (mean 7.1‰±1.6‰), respectively. Dissolved NO₃^- and SO₄^2- in rainwater were derived mainly from local fossil fuel combustion, but were also affected by transmission of pollutants from surrounding areas. (4) Air mass backward trajectories indicated that East Asian monsoon was the main factor affecting the dry and wet deposition of nitrogen and sulfur in the study area, and the large geomorphic pattern running northeast to southwest of the eastern Sichuan parallel gorge has aggravated the influence of the East Asian monsoon.





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