Effects Of Exogenous Methane Concentration,pH,Salt Content On Saline-alkali Soil CH₄Uptake

The study site is located within Hetao irrigation area in Bayannur City, in the west of Inner Mongolia. the alkalinity, mild saline soil, strength saline alkali soil and saline soil was chosen as the object of study. A indoor incubation experiment was conducted to study CH4absorption characteristics and influence of exogenous CH4concentration, pH and salt content on CH4absorption characteristics in different saline alkali soil. This study provides the new data for the saline alkali soil in CH4sinks field, then provides reasonable support of theoretical data about the measures the greenhouse gas emission and prediction of climate change.The main results are as follows:1. An indoor incubation experiment was conducted to investigate soil CH4uptake in different intensity of saline-alkali soil. The higher the saline-alkali levels, the smaller CH4uptake. Soil CH4uptake from high to low was ranked mild saline alkali soil, strength saline alkali soil and saline soil. Soil salinization inhibited CH4uptake. The significant negative correlation existed between CH4uptake and salt content (r=-0.9826**,P<0.01), and pH (r=-0.9550*,P<0.01). Soil CH4uptake had a significant positive correlation with TOC (r=0.9273*,P<0.01).2. The concentration of exogenous CH4promoted the ability of CH4uptake of saline alkali soil,all of the saline alkali soil in high concentration CH4were significantly higher than that of the atmosphere in CH4uptake rate and accumulation, accumulation of CH4uptake of soil and content of salt showed a significant negative correlation(r=-0.9410*,P<0.01). The content of CH4uptake from high to low was mild saline soil, strength saline alkali soil and saline soil; concentration of exogenous CH4was significantly correlated with CH4uptake of soil (r=0.9110*, P<0.01).3. Compared mild saline alkali soil and saline soil adjusted pH to5,6,7,12with original soil pH8.11(mild saline alkali soil),8.79(saline soil). the results show that:the uptake of mild saline soil in each pH level were obviously higher than that of saline soil; saline, pH under7, with the increase of pH, CH4uptake increased, pH upon7, with the increase of pH, CH4uptake decreased, but the uptake in pH12was maximum. Mild saline soil, pH under7, with the increase of pH, CH4uptake increased, pH upon7, with the increase of pH, CH4uptake decreased. When pH was7, uptake CH4of mild saline alkali soil and saline soil were the largest.4. To research CH4absorption characteristics in soil, the salt content was controlled at0.1%(mild saline alkali soil background value),0.5%,1%,2%and5%level. The results show that:when the salt content was lower than1%, CH4uptake increased with the increase of salt content. When salt content was higher than1%, CH4uptake decreases with the increase of salt content. Soil salinity was equal to1%, CH4uptake was the maximum. When salt content was at0.1%,0.5%,1%,2%and5%level, CH4uptake were-454.83μg.kg-1,-662.36μg.kg-1,-678.54μg.kg-1,-382.14μg.kg-1and-355.86μg.k-1,respectively.5. Choose0.1%of KC1, NaCl, NH4C1and MgCl2into saline soil, the results show that:after adding the salt, CH4uptake of soil were higher than those without salt, the added salt promoted CH4uptake of soil;CH4absorption characteristics was different after adding different types of salt in saline soil. The cumulative uptake of CH4in soil from high to low was KCl, NaCl, NH4Cl, MgCl2; CH4uptake in saline soil added KCl was the maximum, MgCl2had no significant effect on CH4uptake, CH4uptake in saline soil added NaCl was higher than added NH4Cl.