To what extent can soil moisture and soil Cu contamination stresses affect nitrous species emissions? Estimation through calibration of a nitrification–denitrification model

[摘要] Continental biogeochemical models are commonly used to predict the effect of land use, exogenous organic matter input or climate change on soilgreenhouse gas emission. However, they cannot be used for this purpose to investigate the effect of soil contamination, while contamination affectsseveral soil processes and concerns a large fraction of land surface. For that, in this study we implemented a commonly used model estimating soilnitrogen ( N ) emissions, the DeNitrification DeCompostion (DNDC) model, with a function taking into account soil copper ( Cu )contamination in nitrate production control. Then, we aimed at using this model to predict N 2 O-N , NO 2 -N , NO-N and NH 4 -N emissions in the presence of contamination and inthe context of changes in precipitations. Initial incubations of soils were performed at different soil moisture levels in order to mimic expectedrainfall patterns during the next decades and in particular drought and excess of water. Then, a bioassay was used in the absence or presence of Cu to assess the effect of the single (moisture) or double stress (moisture and Cu ) on soil nitrate production. Data of nitrateproduction obtained through a gradient of Cu under each initial moisture incubation were used to parameterise the DNDC model and to estimatesoil N emission considering the various effects of Cu . Whatever the initial moisture incubation, experimental results showed a NO 3 -N decreasing production when Cu was added but depending on soil moisture. The DNDC- Cu version we proposed was able to reproduce these observed Cu effects on soil nitrate concentration with r 2   >  0.99 and RMSE   10 % for all treatments in the DNDC- Cu calibration range ( >  40 % of the water holding capacity) butshowed poor performances for the dry treatments. We modelled a Cu effect inducing an increase in NH 4 -N soil concentration andemissions due to a reduced nitrification activity and therefore a decrease in NO 3 -N , N 2 O-N and NO x - N concentrations and emissions. The effect of added Cu predicted by the model was larger on N 2 - N and N 2 O-N emissions than on the other N species and larger for the soils incubated under constant than variable moisture. Ourwork shows that soil contamination can be considered in continental biogeochemical models to better predict soil greenhouse gas emissions.

[学科分类] 大气科学