胶州湾滨海湿地土壤溶解性有机碳淋溶特征

[目的]在山东省青岛市胶州湾滨海湿地采集光滩、碱蓬、芦苇和米草4种不同植被类型土壤,探究滨海湿地土壤溶解性有机碳淋溶特征。[方法]通过室内土柱淋溶试验,测定土壤淋出液溶解性有机碳(DOC)浓度,利用紫外—可见分光光度法对土壤淋出液DOC结构进行分析。[结果]土壤淋出液DOC浓度随土层深度增加而增加;芦苇湿地的土壤淋出液DOC浓度最高,为23.12mg/L,其次分别为碱蓬湿地,米草湿地和光滩湿地,分别为15.22mg/L,14.44mg/L与8.38mg/L。4种土壤淋出液DOC光谱特征值存在一定的差异性,碱蓬湿地土壤淋出液DOC的芳香性和腐殖化程度最高,米草湿地土壤淋出液DOC的分子量和团聚化最大;随土层深度的增加土壤淋出液DOC的芳香性、腐殖化程度增大,分子量以及团聚化程度逐渐减小。[结论]植被残体的分解以及土壤的解吸附能力的差异是造成不同土层土壤淋出液DOC浓度差异的主要原因;而植被类型是影响土壤淋出液DOC结构变化的关键因素。

Leaching Characteristics of Soil Dissolved Organic Carbon in Coastal Wetlands of Jiaozhou Bay

[Objective] To collect soil samples covered by four different types of vegetation (mudflat, Suaeda glauca, Phragmites australis and Spartina alterniflora) around Jiaozhou Bay coastal wetland in Qingdao City, Shandong Province, in order to explore the leaching characteristics of soil dissolved organic carbon (DOC) in coastal wetland. [Methods] The DOC contents of soil leachate from the soil samples were determined by soil column leaching test in laboratory, and the DOC structure was analyzed by UV-visible spectrophotometry. [Results] The DOC content in soil leachate increased with the increase of soil depth. The highest DOC content was 23.12 mg/L in soil leachate from P. australis, followed by the S. glauca (15.22 mg/L), S. alterniflora (14.44 mg/L) and mudflat (8.38 mg/L). The aromaticity and humification of DOC in the soil leachate of the S. glauca was the highest, and the molecular weight and aggregation degree of DOC in the soil leachate of S. alterniflora was the largest. With the increase of soil depth, the aromaticity and humification of DOC in the soil leachate increased, while the molecular weight and aggregation degree decreased. [Conclusion] The decomposition of vegetation residues and the difference in soil desorption capacity are the main factors influencing the DOC concentration of leachate in different soil layers. The vegetation type is the key factor affecting the DOC chemical structure in soil leachate.