Combined assessment of methane oxidation and nitrification: an indicator of air-borne soil pollution?

摘要

Soil nitrification and CH4 oxidation activity were measured in six forested soils in a region of south-western Poland differently affected by heavy metals and hydrocarbon contamination from a coke production plant, road traffic and general urban sources. A multivariate analysis of data from 80 sites within the six forested areas investigated identified Ni and an unidentified hydrocarbon (H1) as negatively affecting nitrification and CH4 oxidation in a model (P=0.02) that also included soil organic matter and pH. Univariate statistical analysis of these two suspected toxicants demonstrated a negative influence of Ni on nitrification (P<0.05) within the two areas in which soil Ni concentrations were highest. In addition, it revealed a negative influence of H1 on CH4 oxidation (P<0.06) at the two sites with the highest soil concentrations of H1 among those sites where CH4 oxidation occurred. The distribution of nitrification and CH4 oxidation were inversely related, as would be expected from their contrasting responses to soil disturbances and inorganic N levels. Among sites where at least one of the two processes occurred, Ni or H1 levels were high in only 18% of them, which is significantly lower than the frequency of high pollutant concentrations (67%) among sites where neither nitrification nor CH4 oxidation occurred (P<0.05). The apparent ubiquity with which at least one of the two processes occurs in unpolluted soil samples suggests that combined measurement of nitrification and CH4 oxidation could serve as a useful pollution indicator compared with processes which are selected more randomly for toxicological studies.