Agricultural Activities and Carbon Cycling in Karst Areas in Southwest China:Dissolving Carbonate Rocks and CO2 Sink
Received date: 2011-09-05
Revised date: 2012-02-18
Online published: 2012-04-10
HOBO automatic weather station，WGZ-1 photoelectric digital water table gauge and CTDP300 on-line water quality analyzer were set up to monitor rainfall, hydrochemistry and water stage at an agriculture dominated karst catchment, which is Qingmuguan underground river systemin Chongqing China. The groundwater were sampled and analyzed monthly for hydrochemistry, Dissolved Inorganic Carbon(DIC) concentration and stable carbon isotopes (δ13C-DIC) in 2010. Hydrochemistry and stable carbon isotopes can verify that sulphuric acid and nitric acid take part in dissolving carbonate rocks, and the concentrations of dissolved inorganic carbon in underground river are due to the weathering of carbonate minerals by carbonic acid, sulphuric acid and nitric acid. The contribution rate that carbonic acid dissolving carbonate rocks making DIC largely varies from seasons, showing 62.98% in wet season and 74.86% in dry season，between 55.53% and 81.25%. In Qing Muguan catchment, the flux of DIC due to carbonic acid dissolving carbonate rocks is 14.67×106 mol/a, accumulating carbon sink of 7.335×106 mol/a, the flux of DIC due to carbonate rocks weathering by sulphuric acid and nitric acid is 7.48×106 mol/a, amounting to a third of total DIC of ground water. Sulphuric acid and nitric acid dissolving carbonate rocks contribute to increasing DIC of 1.89×106 mol/a every square kilometers of cultivated land. This result is obviously less than the values calculated by predecessors. This work shows that sulphuric acid and nitric acid derived from human activities involve in dissolving carbonate rocks and changing carbon cycling.
Zhang Xingbo, Jiang Yongjun,Qiu Shulan, Cao Min,Hu Yijun . Agricultural Activities and Carbon Cycling in Karst Areas in Southwest China:Dissolving Carbonate Rocks and CO2 Sink[J]. Advances in Earth Science, 2012 , 27(4) : 466 -476 . DOI: 10.11867/j.issn.1001-8166.2012.04.0466
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