Production And Emission Of Matrix-bound Phosphine And Greenhouse Gas Fluxes In Special Aquatic Environments

The main research areas from sediment profiles in Lake Chaohu of China, surface sediments along the fjord Kongsfjorden of Arctic and the littoral zone in Lake Daming of East Antarctica were studied to investigate the distribution of MBP and greenhouse gases （N₂O、CH₄、 CO₂）. The main research contents and results were as follows:The distribution patterns of Matrix-bound phosphine （MBP）, phosphorus （P） factions and neutral phosphatase activity （NPA） were investigated through the five sediment profiles in Lake Chaohu, China. MBP was found in all the sediment profiles with the concentration range of1.58-50.34ng kg-1. The concentrations of MBP exhibited a consistent vertical distribution pattern in all the profiles, and higher MBP concentrations generally occurred in the surface sediments. MBP concentrations showed a significant positive correlation with P fractions, total nitrogen （TN）, Cu and Zn under lower levels of inorganic phosphorus （＜0.6g kg-1）, organic phosphorus （＜0.2g kg-1）, TN （＜0.13%）, Cu （＜25mg kg-1） and Zn （＜150mg kg-1）, but no statistically significant correlations were obtained under higher levels. The multiple stepwise regression model （[MBP]=1.36[NPA]-6.21[pH]-0.06[Zn]+0.75[Cu]+49.86） was obtained between MBP concentrations and environmental variables, and MBP concentrations showed a strong positive correlation with NPA （P＜0.0001）, indicating that the production of sediment MBP was controlled by the microbially-mediated processes in Lake Chaohu. This model could be used to predict MBP levels in the sediments. Our results indicated that MBP level could not be used as an indicator for the degree of lake eutrophication. The study of sediment MBP, P factions and NPA will improve our understanding of P cycling and their environmental significance in the eutrophic Lake Chaohu.The surface sediments were collected from the glacial bay （GLAC）, the central basin （CENTR） and their transition area （TRANS） along the fjord Kongsfjorden axis on Svalbard, Arctic, and matrix-bound phosphine （MBP）, phosphorus fractions and alkaline phosphatase activity （APA） were analyzed. MBP was found in all the sediments with the concentration range of8.93-59.45ng kg-1dw. The MBP levels in the CENTR sediments were two times higher than those in the GLAC and TRANS sediments, and the yield of phosphine （PH3） as a fraction of total phosphorus ranged from1.78×10-8to3.53×10-8mg PH3mg-1P. The CENTR and TRANS sediments showed higher concentrations of total phosphorus （TP）, organic phosphorus （OP） and APA than the GLAC sediments, indicating that glacial activity had an important effect on the spatial variability in the concentrations of MBP and phosphorus fractions. There existed a significant positive correlation （p＜0.01） between MBP and seawater depths, OP, TP, APA, total organic matter, total nitrogen and total sulfur. The multiple stepwise regression model （[MBP]=16.1[OP]+18.6[APA]-26.1pH+221.3） was obtained between MBP concentrations and environmental variables. This model could be used to predict MBP levels in the sediments. Our results indicated that the production of MBP was associated with OP decomposition and microbially mediated factors in the sediments of Kongsfjorden in Arctic.Nitrous oxide （N2O）, methane （CH4） and carbon dioxide （CO2） fluxes were investigated from the algal-rich littoral zone of Lake Darning, East Antarctica during the summers of2008/09and2009/10, using a static chamber technique. High N2O emissions occurred in the littoral zone with the mean flux range of0.19-7.11mmol N2O m-2h-1.The mean CH4fluxes ranged from2.51-5.32mmol CH4m-2h-1, and they were significantly affected by the lake thermal regime. There were significant differences （P＜0.05） in CH4and N₂O fluxes under the light and dark conditions, and sunlight greatly increased N2O emissions by stimulating the algal photosynthesis, but decreased CH4emissions. Overall the littoral zone represented a weak CO2sink with the mean flux range of-0.3-0.13mmol CO2m-2h-1. The mean ecosystem respiration and photosynthesis rates varied from0.47-2.90mmol CO2m-2h-1and from-0.33to-2.63mmol CO2m-2h-1.The combined global warming potential （GWP） of N2O and CH4fluxes completely counteracted and surpassed CO2uptake by the algal photosynthesis, and high GWP-positive of N2O and CH4emissions might convert an algal-rich lake site with a net CO2uptake into a net radiative forcing source during the ice-free period.