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Yu D.-X.,Chongqing Shapingba Meteorological Bureau | Ma X.-X.,Beijing Guodian Futong Science and Technology Development Co. | Tan B.-Q.,Chongqing Shapingba Meteorological Bureau | Zhao D.-W.,Chongqing Institute of Environmental Science | And 2 more authors.
Huanjing Kexue/Environmental Science | Year: 2014

Although the total emission of sulphure dioxide (SO2) was reduced by more than 10% in the Eleventh Five-Year-Plan (2006-2010) in China, the total emission of nitrogen oxides (NOx) in the same period kept increasing. In order to evaluate the effects of the emission changes on acid depostion, a ten-year monitoring on forest throughfall was carried out from 2001 to 2010 at Tieshanping, Chongqing in Southwestern China. The results indicated there was a significantly decreasing trend of sulphur deposition and an increasing trend of nitrogen deposition, which coincided well with the dicreasing trend of SO2 emission and increasing tread of NOx emission in Chongqing, respectively. As the net effect, acid deposition was reduced by the emission contol. However, the total deposition of sulphur and nitrogen in 2010 was estimated to be 9.9 keq·(hm2·a)-1 and 4.5 keq·(hm2·a)-1, respectively according to the throughfall data, with the former probably overestimated by 28% and the latter underestimated by 50%. Since both the sulphur deposition and nitrogen deposition are higher than the highest levels in the history in Europe and North America, acid deposition is still a serious issue in Chongqing.

Duan L.,Tsinghua University | Ma X.-X.,Tsinghua University | Yu D.-X.,Chongqing Shapingba Meteorological Bureau | Tan B.-Q.,Chongqing Shapingba Meteorological Bureau
Huanjing Kexue/Environmental Science | Year: 2013

The impact of nitrogen deposition on the dynamics of carbon pool in forest soil was studied through a field experiment at Tieshanping, Chongqing in Southwest China. The changes of dissolved organic matter (DOM) concentration in soil water in different soil layers were monitored for five years after addition of ammonium nitrate (NH4NO3) or sodium nitrate (NaNO3) at the same dose as the current nitrogen deposition to the forest floor. The results indicated that the concentration and flux of dissolved organic carbon (DOC) were increased in the first two years and then decreased by fertilizing. Fertilizing also reduced the DOC/DON (dissolved organic nitrogen) ratio of soil water in the litter layer and the DOC concentration of soil water in the upper mineral layer, but had no significant effect on DOC flux in the lower soil layer. Although there was generally no effect of increasing nitrogen deposition on the forest carbon pool during the experimental period, the shift from C-rich to N-rich DOM might occur. In addition, the species of nitrogen deposition, i.e., NH4+ and NO3-, did not show difference in their effect on soil DOM with the same equivalence.

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