Yu Qian, Wang Wenjia, Chang Jiale, Li Han, Zhang Zimeng, Ke Piaopiao, Duan Lei, Zhang Lei, Zhao Yu
State Key Laboratory of Pollution Control & Resource Reuse and School of Environment, Nanjing University, Nanjing, China.
Institute for Atmospheric and Earth System Research (INAR) / Physics, Faculty of Science, University of Helsinki, Helsinki 00014, Finland.
Sci Total Environ. 2024 Nov 15;951:175701. doi: 10.1016/j.scitotenv.2024.175701. Epub 2024 Aug 22.
Wetlands are widely recognized as hot spots for the emission or deposition of biogenic sulfur gases, including hydrogen sulfur (HS) and sulfur dioxide (SO), which significantly affect air quality and climate change. With the expansion of urban wetlands, it is critical to know the roles that urban wetlands played in atmospheric HS and SO budget. In this study, the surface-air exchange fluxes of HS and SO were measured by the Dynamic Flux Chamber (DFC) method in a typical urban wetland in eastern China from Sep 2022 to July 2023. It was found that the urban wetland did not have the expected high HS emission, might be caused by the relatively high pH value and low sulfate concentration in the soil. Although HS showed emission in the daytime of spring and summer, an overall HS flux of -0.04 kg S ha yr was observed throughout the year. Meanwhile, the urban wetland presented a net sink of SO, with a deposition flux of 0.14 kg S ha yr. The negative peaks of SO flux corresponded to the suddenly elevated SO concentration in the ambient air especially in spring and winter. Through linear fitting of SO flux and concentration, the concept of SO "compensation point" was proposed. The compensation point is the concentration level at which the observed SO flux equals zero. The "compensation point" changed with the season and was related to temperature and humidity. The "compensation point" in summer and autumn were larger, being 2.37 ppb and 1.40 ppb, respectively, while they were 1.07 ppb and 0.86 ppb in spring and winter respectively. Our results suggest that the urban wetland expansion may have little risk of increasing air HS but could act as a significant sink of SO with high SO concentration in the urban region.
湿地被广泛认为是生物源硫气体排放或沉积的热点地区，这些气体包括硫化氢（HS）和二氧化硫（SO），它们对空气质量和气候变化有显著影响。随着城市湿地的扩张，了解城市湿地在大气中HS和SO收支中所起的作用至关重要。在本研究中，于2022年9月至2023年7月期间，采用动态通量室（DFC）方法在中国东部一个典型城市湿地中测量了HS和SO的地表-空气交换通量。研究发现，城市湿地并未出现预期的高HS排放，这可能是由于土壤中相对较高的pH值和较低的硫酸盐浓度所致。尽管HS在春季和夏季的白天表现为排放，但全年观测到的HS通量总体为-0.04 kg S ha yr。同时，城市湿地呈现出SO的净汇，沉积通量为0.14 kg S ha yr。SO通量的负峰值对应于环境空气中SO浓度的突然升高，尤其是在春季和冬季。通过对SO通量和浓度进行线性拟合，提出了SO“补偿点”的概念。补偿点是观测到的SO通量等于零时的浓度水平。“补偿点”随季节变化，与温度和湿度有关。夏季和秋季的“补偿点”较大，分别为2.37 ppb和1.40 ppb，而春季和冬季分别为1.07 ppb和0.86 ppb。我们的研究结果表明，城市湿地扩张可能对增加空气中的HS风险较小，但在城市地区SO浓度较高时，可能成为SO的重要汇。
