武河湿地碳氮净化长效性及其内源分布与释放

Long-term Effectiveness of Carbon and Nitrogen Purification of Wuhe Constructed Wetland and Their Internal Distribution and Release

实验以运行10年的山东武河人工湿地为例,按照水流方向采集原位水样和柱状沉积物样,对其碳氮的净化能力和沉积物碳氮的分布特征及其内源释放风险进行了分析。结果表明:武河人工湿地稳定运行10年后,对水体中的氮仍具有一定净化能力,TN去除率为35%左右,但对COD基本没有净化效果,出水COD值达70.73 mg/L,水体NH3-N、NO3--N、TN和COD浓度均未能达到地表水Ⅳ类水质的设计目标;武河人工湿地沉积物TN含量较高,表层20 cm平均含量高达3 742.95 mg/kg,为重度污染,NH3-N平均含量为303.06 mg/kg,占TN的比例为8.09%,NO3--N平均含量极低,仅为5.19 mg/kg,沉积物氮主要以有机氮(ON)的形式存在;垂向上,沉积物TN含量为2 755~4 250 mg/kg之间,总体上表现为随深度增加略微减少的趋势,外源氮负荷对沉积物TN起决定作用。静态培养实验显示,武河湿地各点位沉积物同上覆水体NH3-N、TN和COD的交换速率差异较大,但均以吸附为主,4个点位对COD的吸附速率分别为2 921.25、3220.85、3 629.70和5 135.91 mg/(m2·d),人工湿地沉积物对水体NH3-N、TN和COD具有较好的吸附能力。湿地沉积物有机质(LOI)含量为4.57%~11.9%,相关性分析表明,沉积物LOI与NH3-N、NO3--N、TN的含量均呈显著正相关,相关系数分别为0.703、0.748和0.700,沉积物氮负荷与有机质来源相对一致。

Study on long-term running effects of constructed wetlands is very important,but now the related research is less.In this article,taking Wuhe constructed wetland of Shandong Province as an example,in situ water and intack columnar sediments were collected according to the direction of water flow,and the purification ability of carbon and nitrogen in water body,the distribution of sediment carbon and nitrogen and their endogenous release risks were studied.Results showed that after ten years of running,Wuhe artificial wetland still had ability to purify nitrogen in water,the removal rate of TN is about 35%,but had no purification efficiency on COD,with COD of effluent water as 70.73 mg/L,and the concentration of NH3-N,NO3--N,TN and COD failed to achieve the design goal of the quality of the surface waterⅣstandard.Sediment TN of Wuhe artificial wetland was severely polluted,and the average content of surface 20 cm was 3 742.95 mg/kg,the average NH3-N content was 303.06 mg/kg,which accounted for 8.09%of the TN,average NO3--N content was extremely low with only 5.19 mg/kg,and the organic nitrogen was the main form of sediment nitrogen.In vertical,sediment TN content was 2 755~4 250 mg/kg,showing slightly decrease trend with depth increase,and sediment TN content controlled by exogenous nitrogen loads.Static release experiments showed that the sediment NH3-N,TN and COD endogenous release rates were significantly different,and all mainly showed adsorption,the COD adsorption rates were 2 921.25,3 220.85,3 629.70 and 5 135.91 mg/(m2·d),respectively,sediment of Wuhe constructed wetland had good adsorption capacity on NH3-N,TN and COD in water body.The sediment organic matter ranged from 4.57%~11.90%,and correlation analysis showed the LOI was significant correlated with sediment NH3-N,NO3--N and TN,the correlation coefficients were 0.703,0.748 and 0.700,respectively,reflecting that sediment nitrogen and organic matter had the similar source.