水溶性有机物在水旱轮作土壤剖面中的分馏现象

水溶性有机物(DOM)是有机物质中最为活跃的组成部分，在陆地生态系统物质的迁移转化过程中起重要作用．通过田间试验和室内理化分析证明了DOM在土壤剖面迁移过程中存在明显的“分馏”现象，随着土层深度的增加，对照、施化肥和施污泥处理土壤DOM的浓度分别由145．8、117．7和114．8mg·kg^-1降到21．57、23．23和13．78mg·kg^-l；不施肥和施化肥处理的土壤DOM随着深度的增加，极性物质所占的比例分别由19．01％和18．47％增至34．97％与44．37％，呈上升趋势，而非极性组分所占比例相应降低；施污泥处理则出现相反的规律，极性组分由36．96％降到17．07％，非极性组分由63．04％增为82．93％．土壤DOM的生物降解率由上到下对照和施化肥处理分别由24．38％和24．00％增大到54．74％和53．81％，而施污泥处理的变化规律则相反，由53．19％降到30．75％．DOM的生物降解率与DOM中极性物质的含量呈正相关关系．紫外光谱进一步证实了这一结果．

Vertical fractionation of dissolved organic matter in soil profile under water-dry cultivation

Dissolved organic matter (DOM) is the most active component of organic matters, and plays an important role in the translocation and transformation of pollutants and nutrients in terrestrial ecosystem. In this paper, the vertical fractionation of DOM in a yellow brown soil under water-dry cultivation was investigated by field experiment and physico-chemical analyses. The results showed that in treatments CK, chemical fertilizer and sewage sludge, the DOM concentration decreased from 145.8, 117.7 and 114.8 mg x kg(-1) to 21.57, 23.23 and 13.78 mg x kg(-1) with soil depth, respectively. In control and fertilizer-treated soils, the hydrophilic fraction of DOM was increased respectively from 19.01% and 18.47% to 34.97% and 44.37% with soil depth, and the biodegradable rate of DOM also increased with soil depth. In sludge-treated soil, a reverse tendency was found for the concentration of hydrophilic DOM and its biodegradable rate. Hydrophilic fraction decreased from 36.96% to 17.07%, the increase of hydrophobic fraction was from 63.04% to 82.93%, and the biodegradable rate decreased from 53.19% to 30.75% with soil depth. The biodegradable rate of DOM was positively correlated to the hydrophilic fraction of DOM, and UV spectra analysis also suggested this.