石臼漾湿地冬季有机质的可生化性

在冬季,石臼漾构筑根孔湿地对有机质的去除率不高.若设想这只是一个表观现象,实际上湿地在冬季能够有效地去除水体中难降解有机质,但释放部分易生化的有机物质.为了验证这一假设,研究了冬季石臼漾湿地岸边带和植物床-沟壕系统中有机质可生化性的空间分布.结果表明:湿地内部其有机质可生化性r(BOD₅/COD_Cr)为0.26~0.84,80%数据高于可生化性下限值(0.30),远超过源水(0.0999).经过湿地净化,水体中有机质的性质发生了显著的变化.湿地内部其r(COD_Cr/TOC)比值(0.85~2.57,平均值1.90)远低于源水(5.41),大量的还原性有机物质及部分芳香族类化合物被湿地拦截和持留.这说明即使在冷季,石臼漾湿地仍对源水中的有机质具有较好的去除效果.以人工湿地生态根孔技术为核心的植物床-沟壕系统是整个湿地中水质净化特别是有机质去除的关键区域.

Biodegradability of organic matter in Shijiuyang wetland during winter

In winter, the removal of organic matter in Shijiuyang root channel wetland was low. We suggested that it was only an apparent phenomenon and hypothesized that in cold season, the constructed root channel wetland could remove the non-biodegradable organic matter effectively from source water and release certain amount of biodegradable organic matters, thus resulting in low removal rates for organic matter. To test this hypothesis, we examined the spatial distribution of biodegradability of organic matter in the riparian zones and plant-bed/ditch systems in Shijiuyang wetland during winter. Results showed that the biodegradability of organic matter within the wetland was much more than that of source water. The classic ratio r(BOD₅/COD_Cr), reflecting the biodegradability of organic matter in water, ranged between 0.26~0.84 with 80% of data exceeding the lower limit (0.30) of biodegradability within the wetland and much higher than that of source water (0.0999). After the wetland treatment, the organic matter feature in the water changed significantly. The ratio r(COD_Cr/TOC), reflecting the relative composition of organic matter, ranged between 0.85~2.57 with a mean of 1.90 within the wetland, significantly less than that of source water (5.41). It was suggested that a large quantity of reducible organic matter was removed. Results also showed that part of aromatic compounds were intercepted and retained by the wetland. These results demonstrated that in cold season, Shijiuyang wetland could exhibit a relatively high efficiency for the removal of organic matter from source water. The crisscrossed plant-bed/ditch systems and the core of constructed root channel technology were the key area for the water quality improvement of the wetland.