Carbon Dioxide and Methane Emissions from Kaoping River and Chenchin Lake in Southern Taiwan

Abstract

To quantify the greenhouse gas emissions from rivers and lakes, environmental conditions, water qualities, carbon dioxide and methane emissions were determined in the up-, mid- and down-stream areas of Kaoping River and Chenching Lake. Atmospheric carbon dioxide concentrations were 292-430, 295-453, 328-476 and 302- 449 ppm, respectively, and atmospheric methane concentrations were 1.70-2.09, 1.71-3.10, 1.70-2.86 and 1.18- 3.60 ppm, respectively. By using the headspace method with brown color bottle, carbon dioxide concentrations were determined as 198-5,437, 1,077-8,584, 3,977-10,839 and 1,537-9,902 ppm, respectively, and methane concentrations fell into the range of 2.8-231.0, 38.9-881.2, 75.3-983.1 and 31.5-4,321.5 ppm, respectively. By using the static-chamber method, carbon dioxide emission rates were -51.3-209.3, -9.6-232.4, -25.7-265.8 and -155.9-217.1 mg m^(-2) h^(-1), respectively, and methane emission rates were 0.05-1.52, 0.05-4.50, 0.26-6.12 and 0.02- 2.68 mg m^(-2) h^(-1), respectively. There is a positive correlation between methane concentration with the headspace method and emission rate with the static-chamber method. Methane emission was very significantly negativelycorrelated with dissolved oxygen (DO), significantly negatively-covrelatived with redox potential (Eh), and very significantly positively-correlated with methane concentration, carbon dioxide concentration using the head-space method, total alkalinity (ALK), and conductivity (CD) in the tested river. Carbon dioxide emission in the tested river had positive correlation with methane concentration by the head-space method. Methane emission in the test lake had very significantly positive correlation with alkalinity (ALK), significantly positive correlation with redox potential (Eh), biological oxygen demand (BOD) and chemical oxygen demand (COD). The annual carbon flows from Kaoping River into ocean from 2003 to 2007 were estimated between 3.7 × 10^5 and 1.7 × 10^6 tons.