南四湖内源氮磷释放的对比研究

采用柱状沉积物采样器和Peeper间隙水采集器分别于2011年8月获取南四湖不同湖区原位柱状沉积物和间隙水,通过原柱样静态释放实验及间隙水分子扩散模型对其氮磷释放规律进行了研究.结果表明,南四湖不同湖区夏季氮磷界面交换速率差异显著,静态释放实验沉积物NH4+-N和PO43--P的释放速率分别为3.1～10.3 mg·m-2· d-1和0.3～2.7mg·m-2· d-1,总体呈北高南低的趋势,南阳湖明显大于其他各湖区,这与其距离济宁市区较近,沉积物受污染较重有关.Peeper法与离心法分别获取不同湖区间隙水,利用分子扩散模型计算出NH4+-N和PO43--P的释放速率分别为3.69～4.51 mg·m--2·d-1、0.24 ～0.66 mg·m-2·d-1和2.54～4.16 mg·m-2·d-1、0.04～0.51 mg·m-2·d-1,同一采样点,Peeper法计算出释放速率比传统离心法高出约20％.通过静态释放实验获得的NH4+-N和PO43--P释放速率(R)在空间分布上与间隙水分子扩散模型计算出的结果相一致,但前者明显大于后者,将其进行比较,氮和磷的R/F值分别为0.84 ～2.64和2.03 ～13.79,表明原柱样静态模拟实验进行内源释放速率估算时,可能比分子扩散模型法计算的结果更接近于实际情况.

Comparative study on endogenous release of nitrogen and phosphorus in Nansi Lake, China

Intact sediments and interstitial water were collected by sediment sampler and Peeper (pore water equilibriums) from different zones of Nansi Lake in August 2011, and the release of nitrogen and phosphorus in sediments were studied through static incubation and interstitial water molecule diffusion model. Results showed that nitrogen and phosphorus releasing rates from sediments were significantly different between zones of Nansi Lake in summer, with a general north-to-south decreasing trend. The release rates of NH₄⁺-N and PO₄^3--P through static incubation were 3.1~10.3 mg·m^-2·d^-1 and 0.3~2.7 mg·m^-2·d^-1, respectively. The release rates of NH₄⁺-N and PO₄^3--P from Nanyang Lake were significantly greater than other Lakes and this may be due to the serious pollution from the nearby Jining City to the Northern Nansi Lake. Centrifugation and Peeper method were used to obtain porewater in different sampling areas of Nansi Lake, and the releasing rates of sediment NH₄⁺-N and PO₄^3--P estimated by Fick's Law were 3.69~4.51 mg·m^-2·d^-1, 0.24~0.66 mg·m^-2·d^-1 and 2.54~4.16 mg·m^-2·d^-1, 0.04~0.51 mg·m^-2·d^-1, respectively. The releasing rates calculated by Peeper were about 20% higher than those by conventional centrifugal method. The spatial distributions of NH₄⁺-N and PO₄^3--P releasing rates estimated by static incubations and interstitial water molecule diffusion model were consistent, with the releasing rates of NH₄⁺-N much higher than PO₄^3--P. The R/F value of NH₄⁺-N and PO₄^3--P were 0.84~2.64 and 2.03~13.79, respectively. The results indicated that the release rates obtained by static incubations with intact sediment cores may be closer to the actual situation than those by interstitial water molecule diffusion model.