comparisons of three methods for organic and inorganic carbon in calcareous soils of northwestern china比较三种方法的有机和无机碳在中国西北地区石灰性土壤.pdf

Comparisons of Three Methods for Organic and Inorganic Carbon in Calcareous Soils of Northwestern China Xiujun Wang1,2*, Jiaping Wang1,3, Juan Zhang1,3 1 State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, Xinjiang, China, 2 Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland, United States of America, 3 Graduate University of Chinese Academy of Sciences, Beijing, China Abstract With increasing interest in the carbon cycle on arid land, there is an urgent need to quantify both soil organic carbon (SOC) and inorganic carbon (SIC) thus to assess various methods. Here, we present a study employing three methods for determinations of SOC and SIC in the Yanqi Basin of northwest China. We use an elemental analyzer for both SOC and SIC, the Walkley-Black method for SOC, a modified pressure calcimeter method for SIC, and a simple loss-on-ignition (LOI) procedure for determinations of SOC and SIC. Our analyses show that all three approaches produce consistently low values for SOC (1–14 g kg21) and high values for SIC (8–53 g kg21). The Walkley-Black method provides an accurate estimate of SOC with 100% recovery for most soil samples. The pressure calcimeter method is as accurate as the elemental analysis for measuring SIC. In addition, SOC and SIC can be accurately estimated using a two-step LOI approach, i.e., (1) combustion at 375uC for 17 hours to estimate SOC, and (2) subsequent combustion at 800uC for 12 hours to estimate SIC. There are strong linear relationships for both SOC and SIC between the elemental analysis and LOI method, which demonstrates the capability of the two-step LOI technique for estimating SOC and SIC in this arid region. Citation: Wang X, Wang J, Zhang J (2012) Comparisons of Three Methods for Organic