Effects of nitrogen and sulphate addition on methane oxidation in the marsh soil of a typical subtropical estuary (Min River) in China.

Methane (CH4) oxidation plays an important role in regulating the atmospheric CH4 balance. Although nitrogen (N) enhancement and sulphate (<inline-graphic></inline-graphic>) deposition are major environmental problems facing the Min River estuary in subtropical China, the interactive effects of N and <inline-graphic></inline-graphic> on CH4 oxidation remain poorly understood. We conducted an incubation experiment to investigate the effects of N and <inline-graphic></inline-graphic> additions on CH4 oxidation in marsh soils. CH4 oxidation exhibited distinct seasonal variations, which correlated with changes in temperature and soil moisture; in addition, CH4 oxidation rates were enhanced by the addition of nitrate (<inline-graphic></inline-graphic>), but were slightly inhibited by the addition of ammonium (<inline-graphic></inline-graphic>) and <inline-graphic></inline-graphic>. The combined effects of N and <inline-graphic></inline-graphic> on CH4 oxidation were controlled primarily by the form of N, which may imply that inhibition of CH4 oxidation with <inline-graphic></inline-graphic> addition may be counteracted by N addition, especially in estuarine marsh soils with low N and high <inline-graphic></inline-graphic> concentrations. We propose that, although <inline-graphic></inline-graphic> was more effective in stimulating CH4 oxidation and the inhibition caused by <inline-graphic></inline-graphic> and <inline-graphic></inline-graphic> was minor, CH4 oxidation may be inhibited because <inline-graphic></inline-graphic> was dominant and accompanied by strong <inline-graphic></inline-graphic> deposition in the Min River estuary. As such, future CH4 emissions from estuarine wetlands may increase as a result of higher inputs of <inline-graphic></inline-graphic> and <inline-graphic></inline-graphic>. [ABSTRACT FROM AUTHOR]