橡胶坝对沂河蓄水段底泥氮磷释放风险的影响

Effects of Rubber Dam on Releasing Risk of nitrogen and Phosphorus in Sediment of Yihe River

为探讨小埠东橡胶坝建设对沂河临沂城区蓄水段(沂蒙湖)沉积物内源氮磷释放风险的影响,2013年7月利用柱状沉积物采样器分别在祊河主河道、祊河与沂河交汇处和小埠东橡胶坝前50 m获取原位柱状沉积物,通过原柱样静态释放实验及间隙水分子扩散模型对其内源氮磷释放规律进行了研究。结果表明:蓄水段不同采样点氮磷界面交换速率差异较大,静态释放实验沉积物3个点位NH4+-N和PO43--P的释放速率分别为(6.14±0.58)、(3.13±0.92)、(6.62±1.48)mg/(m2·d)和(1.51±1.45)、(1.27±1.02)、(4.04±0.54)mg/(m2·d),分子扩散模型计算出3个点位NH4+-N和PO43--P的释放速率分别为2.241、2.681、6.382 mg/(m2·d)和0.042、0.046、0.247 mg/(m2·d)。虽然静态释放实验获得的NH4+-N和PO43--P释放速率在数值上明显大于间隙水分子扩散模型计算出的结果,但2种方法均一致表明,小埠东橡胶坝前点位NH4+-N和PO43--P的释放速率最高,具有最大内源氮磷释放风险,这与小埠东橡胶坝的建成促进了坝前沉积物中氮磷营养盐的富集有关,建坝后水动力条件的改变是其富集的主要原因。

In order to study the effects of Xiaobudong Rubber Dam on the endogenesis realease risk of nitrogen and phos-phorus in sediment of Yihe River at Linyi City(Yunmeng Lake), intact core sediments were collected in July 2013 by sedi-ment sampler at sampling site of Benghe riverway, confluence of Yihe River and Benghe River and 50 meters before the rub-ber dam, respectively, and the release rules 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 sediment were significantly different among different zones of Yimeng Lake, and the release rates of NH4+-N and PO43--P at the three sampling sites through static incubation were(6.14±0.58),(3.13±0.92),(6.62±1.48)mg/(m2·d) and(1.51±1.45),(1.27±1.02,).(4.04±0.54)mg/(m2·d), and the releasing rates estimated by Fick's Fist Law were 2.241, 2.681, 6.382 mg/(m2·d) and 0.042,0.046, 0.247 mg/(m2·d), respectively. The releasing rates through static incubations were much greater than those calculated from interstitial water molecule diffusion model, but the results from the two methods were consensus, and indicating that the release rate of NH4+-N and PO43--P at sampling site before the dam was the highest with the biggest releasing risk, which reflecting the Xiaobudong Rubber Dam promotes the enrichment of nitrogen and phosphorus nutrients, and the hydraulic condi-tions' changing after building dam was the main cause.