Dissolved greenhouse gas concentrations and the influencing factors in Nansi Lake during winter water diversion period
In order to understand the dissolved concentrations and emission fluxes of greenhouse gases(GHGs)in the surface water of Nansi Lake during the water diversion period,gas samples and surface water samples were collected at 63 sampling sites distributed in the four sub-lakes and the inlet area of the main rivers.Concentrations of carbon dioxide(CO2),methane(CH4)and nitrous oxide(N2O)and the physicochemical properties of surface water were analyzed,and the emission fluxes at the surface water-air interface were calculated by using the thin boundary layer equation(TBL).The influencing factors on the dissolved concentrations of GHGs were discussed by using the correlation analysis and linear regression analysis between the GHG concentrations and the water physicochemical properties.The average concentrations of CO2,CH4 and N2O were(23.0± 6.13)nmolL-1,(0.15±0.10)μmol·L-1 and(52.4±11.4)μmol·L-1,respectively.The GHGs were highly saturated,and the average emission fluxes were(0.22±0.18)μmol·m-2·h-1 for CO2,(3.95± 2.73)μmol·m-2·h-1 for CH4 and(658±336)μmol·m-2·h-1 for N2O,respectively,indicating that Nansi Lake mainly acted as the source of GHGs during the water diversion period;moreover,the concentrations and fluxes were similar to those of other lakes,but lower than those of the plain river network in winter.In general,the concentrations,saturations and fluxes of the three GHGs showed a decreasing trend from the north(the Nanyang Lake)to the south(the Weishan Lake).Higher GHG concentrations were in the inlet area of the rivers and in the area near the second level dam,in addition,there were belt-shaped high concentrations of N2O and CO2 but lower CH4 concentrations in the center of Weishan Lake.The concentrations of GHGs had some significant correlations with the water quality parameters(P＜0.05)indicating that the water quality should have some impact on the dissolved concentrations of the GHGs.Specifically,N2O was positively correlated with NO3 and NO2-,and CH4 was negatively correlated with TN;while CO2 had negative correlations with pH and SD but positive correlation with DOC.The results provide basic data support for the assessment of the influence of the lake on atmospheric greenhouse gases during the water diversion period.
greenhouse gasesdissolved concentrationsspatial distribution characteristicsinfluencing factorswater diversion periodNansi Lake
NETL
NSTL
万方数据
