[Spatial distribution characteristics of Fe and Mn contents in the new-born coastal marshes in the Yellow River estuary].

The spatial distribution characteristics of Fe and Mn contents in soils of nine different vegetation communities, located in the new-born marshes of the northern Yellow River estuary, were studied in May 2009. The results showed that the horizontal distributions of Fe and Mn contents showed an increasing tendency from Sparganiaceae-Potentilla supina marsh to bare flat. The vertical distribution characteristics of Fe and Mn contents in different marsh soils fluctuated significantly with the vegetation succession. The soil parent materials determined the Fe, Mn contents in the new-born marshes, and seawater, vegetations and soil fine particle also had important influences on their contents. Further analysis showed that Fe contents had significant positive correlation with Mn contents (P < 0.01). Fe, Mn contents also showed significant correlations with silt, clay, TN, NO3(-) -N and organic matter (P < 0.05), indicating that Fe and Mn had close relationships with nitrogen, and the contents of soil fine particles and organic matter were the dominant factors affecting the distribution of Fe and Mn in soils. In addition, the Fe contents ranged from 16.49 g x kg(-1) to 33.11 g x kg(-1) and the average was 22.54 g x kg(-1), which was close to the Fe contents in the tidal marshes of north Jiangsu, the Loess Plateau and the China soil background value, but slightly lower than those in the marshes of the Yangtse River estuary, the mangrove swamps and inland lake wetland. The Mn contents ranged from 305.87 mg x kg(-1) to 711.39 mg x kg(-1) and the average was 451.09 mg x kg(-1), which was lower than the Mn contents in the Loess Plateau and the China soil background value. Hydrology and Water Resources Survey Bureau of the Yellow River Estuary, Dongying 257091, China)

[Short-term effects of exogenous nitrogen on CH4 and N2O effluxes from Cyperus malaccensis marsh in the Min River estuary].

Using static chamber-GC techniques, the short-term effects of nitrogen input on the emission fluxes of CH4 and N2O from a Cyperus malaccensis wetland were determined. The results showed that the emission of CH4 was increased by high nitrogen input at all sampling times, whereas the low nitrogen input exhibited different variation characteristics at different time points. Compared to the control treatment, the CH4 emission flux in the two nitrogen input treatments (N1, N2) was increased by -44.35%-1 057.35% and 7.15%-667.37%, respectively. The input of exogenous nitrogen had positive priming effect on N2O emission flux within 24 hours, increased by up to 171.60 folds and 177.79 folds, respectively. After 8 days, the priming effect by the nitrogen input weakened or disappeared. There was no significant effect of nitrogen input on the Ec, pH and Eh of soil at different depths in the salt marsh during the experiment. In the control treatment, the CH4 emission flux was negatively correlated solely with Eh of soil at 5 cm depth, whereas in the N1 treatment, it was negatively correlated solely with soil temperature at 10 cm depth. In the N2 treatment, there was negative correlation between the CH4 emission flux and Ec of soil at 5cm depth, pH of soil at 0, 5 cm depths, and Eh of soil at 0, 5, 10 cm depths. However, no significant correlation between the N2O emission flux and the environmental variables in the wetland was found. This study indicated that the temporal variability should be taken into consideration when examining the effects of nitrogen input on the emission of greenhouse gases in the wetlands.

[Methane fluxes and controlling factors in the intertidal zone of the Yellow River estuary in autumn].

The characteristics of methane (CH4) fluxes from tidal wetlands of the Yellow River estuary were observed in situ with static-chamber and GC methods in September and October 2009, and the key factors affecting CH4 fluxes were discussed. From the aspect of space, the CH4 flux ranges in high tidal wetland, middle tidal wetland, low tidal wetland, bare flat are - 0.206-1.264, -0.197-0.431, -0.125-0.659 and -0.742-1.767 mg x (m2 x h)(-1), the day average fluxes are 0.089, 0.038, 0.197 and 0.169 mg x (m2 x h)(-1), respectively, indicating that the tidal wetlands are the sources of CH4 and the source function of CH4 differed among the four study sites, in the order of low tidal wetland > bare flat > high tidal wetland > middle tidal wetland. From the aspect of time, the ranges of CH4 fluxes from the tidal wetland ecosystems are -0.444-1.767 and - 0.742- 1.264 mg x (m2 x h)(-1), and the day average fluxes are 0.218 and 0.028 mg x (m2 x h)(-1) in September and October, respectively. The CH4 fluxes in each tidal wetland in September are higher than those in October except that the high tidal wetland acts as weak sink in September. Further studies indicate that the changes of environmental factors in the Yellow River estuary are complicated, and the CH4 fluxes are affected by multiple factors. The differences of CH4 fluxes characteristics among different tidal wetlands in autumn are probably related to temperature (especially atmospheric temperature) and vegetation growth status, while the effects of water or salinity condition and tide status on the CH4 flux characteristics might not be ignored.