Mertens Jan, Vanderborght Jan, Kasteel Roy, Pütz Thomas, Merckx Roel, Feyen Jan, Smolders Erik
Soil and Water Management, K.U. Leuven, Celestijnenlaan 200E, B-3001 Heverlee, Belgium.
J Environ Qual. 2007 Mar 1;36(2):597-606. doi: 10.2134/jeq2006.0368. Print 2007 Mar-Apr.
The flux of dissolved organic carbon (DOC) in soil facilitates transport of nutrients and contaminants in soil. There is little information on DOC fluxes and the relationship between DOC concentration and water flux in agricultural soils. The DOC fluxes and concentrations were measured during 2.5 yr using 30 automatic equilibrium tension plate lysimeters (AETPLs) at 0.4 m and 30 AETPLs at 1.20-m depth in a bare luvisol, previously used as an arable soil. Average annual DOC fluxes of the 30 AETPLS were 4.9 g C m(-2) y(-1) at 0.4 m and 2.4 g C m(-2) y(-1) at 1.2 m depth. The average leachate DOC concentrations were 17 mg C L(-1) (0.4 m) and 9 mg C L(-1) (1.2 m). The DOC concentrations were unrelated to soil moisture content or average temperature and rarely dropped below 9 mg C L(-1) (0.4 m) and 5 mg C L(-1) (1.2 m). The variability in cumulative DOC fluxes among the plates was positively related to leachate volume and not to average DOC concentrations at both depths. This suggests that water fluxes are the main determinants of spatial variability in DOC fluxes. However, the largest DOC concentrations were inversely proportional to the mean water velocity between succeeding sampling periods, suggesting that the maximal net DOC mobilization rate in the topsoil is limited. Elevated DOC concentrations, up to 90 mg C L(-1), were only observed at low water velocities, reducing the risks of DOC-facilitated transport of contaminants to groundwater. The study emphasizes that water flux and velocity are important parameters for DOC fluxes and concentrations.
土壤中溶解有机碳（DOC）的通量促进了土壤中养分和污染物的迁移。关于农业土壤中DOC通量以及DOC浓度与水流通量之间的关系，目前所知甚少。在2.5年的时间里，利用30个自动平衡张力板渗压计（AETPLs）在0.4米深度处以及30个AETPLs在1.20米深度处，对一块先前用作耕地的裸土淋溶土中的DOC通量和浓度进行了测量。30个AETPLs在0.4米深度处的年均DOC通量为4.9克碳每平方米每年，在1.2米深度处为2.4克碳每平方米每年。渗滤液中DOC的平均浓度分别为17毫克碳每升（0.4米深度）和9毫克碳每升（1.2米深度）。DOC浓度与土壤含水量或平均温度无关，且很少低于9毫克碳每升（0.4米深度）和5毫克碳每升（1.2米深度）。各渗压计之间累积DOC通量的变异性与渗滤液体积呈正相关，而与两个深度处的平均DOC浓度无关。这表明水流通量是DOC通量空间变异性的主要决定因素。然而，最大的DOC浓度与连续采样期之间的平均水流速度成反比，这表明表层土壤中最大的净DOC迁移速率是有限的。仅在低水流速度下才观察到DOC浓度升高至90毫克碳每升，这降低了DOC促进污染物向地下水迁移的风险。该研究强调水流通量和速度是DOC通量和浓度的重要参数。
