Methane emission from a landfill and the methane oxidising capacity of its covering soil

Abstract

Methane emission from a small covered landfill site showed, seasonally varying fluxes, ranging from −5.9 to 914.3 mg CH 4 m −2 d −1. The moisture content of the CH 4-oxidising cover soil was thought to cause this variation. Comparing gross and net CH 4 emission rates, it was found that the cover soil, due to its CH 4 oxidising capacity, had a large mitigating effect on the CH 4 emission. In laboratory experiments the effects of soil moisture, temperature and different ammonium amendments on CH 4 oxidation were investigated. When the moisture content and temperature were combined, CH 4 oxidation rates between 0.88 and 10.86 ng CH 4 g −1 h −1 were observed. The optimum moisture content ranged between 15.6 and 18.8% w/w ( ±1 2 WHC ). The optimum incubation temperature (30-20°C) decreased with increasing moisture contents. For the oxidation rates at 10 and 20°C, we found an average Q 10 value of 1.88 ± 0.14. The activation energy for moisture contents between 5 and 25% was 83.0 ± 4.4 kJ mol −1. Increased ammonium additions reduced the CH 4-oxidising capacity. This reduction decreased with increasing moisture contents. A high correlation (R 2 > 0.98) was found between the moisture content and the reduction of the CH 4 uptake rate mg −1 NH 4 + −N kg −1 added. Because the nitrification rate was also lower at higher moisture contents, it was thought that the CH 4 oxidation rate was more closely connected with the NH 4 + turnover rate than with its actual concentration. Multiple linear regression analysis of the CH 4 oxidation rates under the different incubation conditions showed the following decreasing effect on the CH 4-oxidising capacity of the soil: amount of NH 4 + added > moisture content > incubation temperature.