Carbon balance model of groundwater system –A field application

Abstract

For the wide distribution and huge amount of water, a series of carbon-related water–rock interactions in groundwater recharge, runoff and discharge have an important impact on the global carbon cycle. However, the current research on carbon cycle of groundwater mainly focuses on its emission to surface water. There are few reports on the carbon balance of groundwater system. Hongjiannao basin was taken as an example in this paper. The carbon balance equation of groundwater system was constructed by using mass balance principle and hydrogeochemical simulation method to analyze the carbon budget in groundwater. The result showed that HongJiannao basin was a ‘carbon sink’ with an annual carbon sink of 754.26 t (0.52 t/km2). Dissolution of dolomite and precipitation of calcite were the main hydrochemical reactions affecting carbon balance of groundwater; HCO3– in atmospheric precipitation and carbon dioxide (CO2) in vadose zone were the main sources of carbon in groundwater. The CO2 recharged by the vadose zone to groundwater was 1441.9 tons/a, most of them had hydration and ionization reactions with water. Artificial exploitation and runoff discharge were the main ways of carbon discharge from groundwater in this area. Carbon emissions from artificial exploitation reached 414.16 t/a, accounting for 58 % of the total carbon emissions from runoff.