沟渠湿地水体和底泥中有机质时空分布规律研究

Mineralization and accumulation of organic matters in water phase and sediment of ditch wetlands

通过分析沟渠湿地水体和底泥中有机质浓度的时空分布规律,发现在芦苇和茭草湿地,40cm以下深度底泥中有机质含量高,是同一层次农田土壤的3倍左右,即底泥对有机质有显著的累积效应.湿地水体中的CODCr浓度随季节发生很大变化,最高浓度出现于1～3月,远超地表水Ⅴ类水质标准,有很大的污染性;而在其余季节含量较低.有机质的这种年度变化主要由植物生长和残体分解引起.死亡的植物茎叶沉积在底泥表层,引起底泥有机质矿化速率发生变化,9月至次年6月芦苇底泥有机质的矿化速率为21 3～133 6g/(m3·d-1),茭草底泥为30 4～119 6g/(m3·d-1).

An analysis was given to the spatial and temporal variation of organic matters in water phase and the sediment of ditch wetlands. It is found that the content of organic matters is high in the sediment below 40?cm in wetlands grown with Phragmites communis Trin and Zizania latifolia Turcz, which is about 3 times as high as that in cropland soil of the same layer. Therefore, the sediment has high ability to accumulate organic matters. The concentration of COD_(Cr) in water phase of the wetlands varies greatly with seasons, the highest concentration occurring from January to March, which is far beyond the concentration of V-class water quality standard, so the pollution in water phase is very serious, but in other months, the concentration of COD_(Cr) is low. The annual rise and fall of the concentration of COD_(Cr) is induced by the growth of plants and decomposition of their remains. The deposition of dead stems and leaves in the surface of the sediment results in the variation of mineralized rate of organic matters in the sediment. The mineralized rates of organic matters in the sediment grown with Phragmites communis Trin and Zizania latifolia Turcz vary in the ranges of 21.3—(133.6?g/(m^3·d^(-1))) and 30.4—119.6?g/(m^3·d^(-1)) respectively from September of a year to June of the next year.