Analysis of Greenhouse Gas Emission Characteristics and Their Influencing Factors in the Algae Zone of Lake Taihu

Abstract

In order to identify CH4 and CO2 emission flux characteristics and their impact factors in the algal lake zone of Lake Taihu, CH4 and CO2 fluxes were observed by the improved closed chamber method in Meiliang Bay in Lake Taihu. The relationships between CH4 and CO2 flux and meteorological factors were analyzed. The results showed that CH4 and CO2 fluxes had obvious diurnal variations. The CH4 flux in the daytime was higher than that in the nighttime in spring; however, the CH4 flux in the nighttime was higher than that in the daytime in summer. The CO2 uptake flux in the daytime was higher than that in the nighttime in spring and summer. The algae zone of Lake Taihu was a CH4 source for the atmosphere. The average CH4 flux was 4.047 nmol ·(m2 ·s)-1 and 40.779 nmol ·(m2 ·s)-1 in spring and summer, respectively. The zone was the CO2 sink for the atmosphere in spring and summer. The average CO2 flux was -0.160 μmol ·(m2 ·s)-1 and -0.033 μmol ·(m2 ·s)-1 in spring and summer, respectively. On an hourly scale, the CH4 emission flux was positively correlated with air temperature and water temperature (r=0.20, P<0.01 and r=0.34, P<0.01, respectively). When wind speed was lower than 6 m ·s-1, the CH4 flux was positively correlated with wind speed (r=0.71, P<0.01). The CO2 uptake flux had a significant positive correlation with air temperature and wind speed (r=0.14, P<0.01 and r=0.33, P<0.05, respectively). However, the CO2 uptake flux was negatively correlated with air pressure and solar radiation (r=-0.41, P<0.01 and r=-0.35, P<0.01, respectively). The CO2 efflux had a significant positive correlation with wind speed (r=0.40, P<0.05). The CO2 efflux was negatively correlated with solar radiation (r=-0.35, P<0.01). On a daily scale, the CH4 emission flux had a significant positive correlation with air temperature and water temperature (r=0.83, P<0.01 and r=0.78, P<0.01, respectively).