[Characteristics of Dissolved CH4 and N2O Concentrations of Weihe River in Xinxiang Section in Spring].

Distributions of CH4 and N2O concentrations in Weihe River in Xinxiang City were monitored in spring of 2015, and their influencing factors were discussed. The result showed that CH4 and N2O were super-saturated in surface water of Weihe River. The variation ranges of two gases' saturations in the surface water of Weihe River were 147.59-2667.85 (CH4) and 4.06-188.25 (N2O). In the urban area, significant correlation existed between N2O and NH4⁺-N concentrations (P < 0.01), but in the new district, dissolved N2O concentration showed sharp increase because of the water input from the urban sewage plants, illustrating that the controlling mechanism on N2O production varied as pollutant characteristics changed. Stepwise regression analysis showed that CH4 concentrations could be explained by NH4⁺-N concentrations and water temperature, and CH4 concentrations in the surface water of Weihe River was significantly correlated with NH4⁺-N concentrations (R² = 0.70, P < 0.01), suggesting that NH4⁺-N was the key factor in regulating the production and assumption of CH4oxidation in Weihe River in spring. Besides, this study showed that when there was less NO3⁻-N but more NH4⁺-N in river water, CH4and N2O concentrations would be positively correlated, indicating that different nitrogen sources would impact the coupling mechanism of CH4and N2O productions.

[Seasonal dynamics of soil organic carbon and active organic carbon fractions in Calamagrostis angustifolia wetlands topsoil under different water conditions].

The experiment was carried in Sanjiang Plain in the northeast of China during the growing season in 2009. Soil organic carbon (SOC), as well as the soil active organic carbon fractions in the 0-20 cm soil layer of Calamagrostis angustifolia wetland under different water conditions were on monthly observation. Based on the research and indoor analysis, the seasonal dynamics of light fractions of soil organic carbon (LFOC) and microbial biomass carbon (MBC) were analyzed. The results indicated that the SOC contents had significantly seasonal dynamics, and the hydrological circle had apparently driving effect on LFOC and MBC during the growing season, especially under the seasonal flooded condition. The freeze-thaw process reduced the SOC, LFOC, MBC contents, with the decreases of 74.53%, 80.93%, 83.09%, while both carbon contents of light and heavy fractions were reduced at the same time. The result also showed that the seasonal flooding condition increased the proportion of LFOC in topsoil, which was larger in marsh meadow (13.58%) than in wet meadow (11.96%), whilst the MBC in marsh meadow (1 397.21 mg x kg(-1)) was less than the latter (1 603.65 mg x kg(-1)), proving that the inundated environment inhibited the mineralization and decomposition of organic matter. But the microbial activity could be adaptive to the flooding condition. During the growing season the MBC soared to 1 829.21 mg x kg(-1) from 337.56 mg x kg(-1) in July, and the microbial quotient was 1.51 times higher than that in June, indicating the high microbial efficacy of soil organic matter. Meanwhile, there was a significant correlation between the contents of LFOC and SOC (r = 0.816), suggesting that higher LFOC content was favorable to the soil carbon accumulation. Moreover, in the seasonal flooded Calamagrostis angustifolia wetland the soil LFOC content was significantly correlated with MBC (r = 0.95), implying that the available carbon source had more severe restriction on the microbial activity under the flooding environment.