Temporal patterns and determinants of atmospheric methane in Suzhou, the Yangtze River Delta

Abstract

Methane (CH4), a greenhouse gas with significant global warming potential, has complicate spatial and temporal distributions, especially for area with intense anthropogenic and natural sources. Here, we present the atmospheric CH4 record from three stations in Suzhou, China, which is located in the famous economic developed zone, with wetland coverage about 20%. The study found that although significant variations in CH4 concentrations across different regions within the Suzhou city, the mean values of the three sites could represent the atmospheric CH4 levels in Suzhou. The annual mean CH4 value in 2021 was significantly higher than that in 2020, with a growth of 8.02 ppb yr−1. CH4 followed a seasonal pattern, with low values in the spring and winter, and peak values in the autumn and summer. However, there were trough and surge values over time, which occurred in summer and winter in both year. These results highlighted that huge amounts of OH radicals accumulated when the summer extended a period of drought and heat, aggravating CH4 consumption and lowering concentration. Moreover, methanogens in subtropical areas might not be impacted by winter's lower temperatures. The CH4 significantly decreased exponentially with the increased wind speed, positively correlated with air temperature in spring and negatively correlated with atmospheric pressure. Taihu Lake, lied in the WNW, W, WSW and SW winds sectors with high concentration of CH4, is a local source. The Yellow Sea and the East China Sea where have some distance from Suzhou are important regional sources to the CH4.