摘要
投加硝酸钙是目前河道黑臭底泥原位治理常用的方法,然而,投加硝酸钙会造成底泥硝态氮和氨氮的过量释放,而其影响机制尚未明确。因此有必要对投加硝酸钙后硝态氮在底泥中的迁移转化规律及其促进氨氮释放的机理进行研究。结果发现,硝酸盐在间隙水的迁移距离取决于硝态氮反硝化速率,而在黑臭底泥中硫化物氧化是影响反硝化速率的关键因素。当硝酸钙投加量为20 g/kg时,硝态氮的迁移距离小于6 cm,且在14 d后消耗光;可见,通过控制硝酸钙在底泥中的投加位置可避免硝态氮的二次释放。另一方面,投加硝酸钙会促进底泥氨态氮向间隙水释放,投加当天释放率可高达101%,且会在间隙水中发生累积迁移。其中,氨氮的增加量和底泥氨态氮解吸量呈一级线性关系(r=0.986)、和硝酸钙投加量关系符合cubic曲线;据此可推测,氨氮的急剧释放与钙离子对底泥铵态氮的化学浸提有关。
Calcium nitrate addition has been proved a cost-effective technology for sediment odor control, however, current researches revealed that ammonium release would be greatly accelerated when calcium nitrate was added, although the process and mechanism were remained unclear. Therefore, experiments were conducted in this work to discover the fate of nitrate transfer and transport in sediments interstitial water and the mechanism of ammonium sharp release when calcium nitrate was added. The results show that when 20 g/kg of calcium ni- trate was added and exhausted within 14 days, the transport distance of nitrate was less than 6 cm. This indica- ted that the transport distance of nitrate was mainly depended on its denitrifieation rate, which was controlled by the content of AVS in odorous sediments. In addition, ammonium release was remarkably accelerated by calcium nitrate addition, the release rate could reach up to 101% at the day when calcium nitrate was injected. Moreo- ver, nitrate would accumulated in interstitial water and potentially transport into the overlying water. It was found that the increase amount of ammonium was proportional with the release amount of exchangeable ammonia in sed- iment with r = 0. 986, while the relationship between ammonium release and calcium nitrate injecting dose could be described with cubic curve, suggesting that sharp release of ammonium could be attributed to iron exchange by Ca^2＋. In a word, the secondary release of nitrate could be well controlled by lowering calcium nitrate adding depth under surface sediments, however, combined technology was required for ammonium release control.
出处
《环境工程学报》
CAS
CSCD
北大核心
2015年第8期3625-3632,共8页
Chinese Journal of Environmental Engineering
基金
国家青年基金资助项目(51108196)
广东省自然科学基金资助项目(S2011040001251)
关键词
黑臭底泥
硝酸钙氧化
氨氮
迁移转化
释放机制
black-odorous sediments
calcium nitrate oxidation
ammonium
transfer and transport
release
