[Effect of elevated atmospheric CO concentration and temperature on volatile halogenated organic compound content in soils of and seedlings].

Global changes caused by the increases of atmospheric CO concentration and temperature have important effects on soil biogeochemical processes. The synthesis and release of volatile halogenated organic compounds (VOXs) is an important pathway for soil to participate in the global material cycle and energy flow. In this study, and seedlings in the southern subtropics were selected as the research objects. Four treatments, including control (CK), elevated CO concentration (EC), elevated temperature (ET) and elevated both factors (EC+ET) were set up. The effects of EC and ET on soil VOXs formation were studied by an open-top chamber system coupled with a purging and trapping gas chromatography/mass spectrometry. The results showed that VOXs content in the soil of seedlings was 0.065-0.252 ng·g, which was higher than that of (0.038-0.136 ng·g). At the EC, ET and EC+ET treatments, VOXs contents were reduced in soils of both species. The effect of ET was the most significant, with the decrease rates of 74.2% and 72.1% in both soils, respectively. The change of VOXs content with increasing temperature mainly attributed to the changes of soil moisture and nitrogen content. The content of VOXs in the soils of seedlings decreased more than that of under different treatments. In CK, EC, ET and EC+ET treatment, bromodichloromethane (BDCM) (27.5%, 36.7%, 32.9%, 32.6%) and tetrachloromethane (TCM) (9.0%, 16.8%, 22.7%, 15.8%) were the main VOXs in the soil of seedlings, respectively, while BDCM and dibromomethane (DBM) were the main VOXs in the soil of seedlings. BDCM accounted for 31.9%, 38.2%, 40.9% and 37.2% of the VOXs content in each treatment, and DBM accounted for 17.9%, 16.5%, 19.2% and 16.0% of the VOXs content, respectively. Simulating elevated atmospheric CO concentration and temperature was conducive to more comprehensive reflection of the ecological effect of global climate change, and it could provide data support for improving the VOCs flux model.