寻找人类活动影响南明河的水化学指纹:Ⅱ.旬际变化

Searching for Hydrochemical Imprints Indicating Human Impacts on the Nanming River: Ⅱ.Ten-Day-Scale Variations

为进一步了解南明河截污沟修建后主城区水化学组成的变化情况,提取人类活动影响南明河的水化学指纹,我们于2008年10月20日至2009年10月20日以10天为间隔或5天为间隔(7月)对南明河主城区进口(四方河)和出口(团坡桥)进行了短时间尺度取样,确证了第一部分所获得的空间变化趋势。出口处Na+、Cl-、NO3-、SO24-分别升高53%、65%、52%和47%;其它离子如K+、Ca2+、Mg2+和HCO3-只是轻微升高,pH温和下降。出口处离子浓度变化趋势继承了入口处离子浓度趋势,但叠加了城区人类活动的明显印记。Na+浓度在6～7月间的显著峰值最有可能起源于2009年为防止禽流感爆发蔓延而广泛使用的次氯酸钠消毒剂,Na+和Cl-具有显著正相关关系可以证明这一推断。另外一个证据是Na+和NO3-较好的反相关关系,说明消毒剂对氨化细菌和硝化细菌具有负面效应,抑制了NO3-的产量。高硫煤的使用则是城区河段高SO24-含量的主要原因。结合离子浓度的均值、变化范围和标准偏差,我们认为Na+、Cl-、NO3-、SO24-可以作为指示城区人类活动影响南明河的水化学指纹。

In this second part, our main purposes are： （1） to further ascertain ten-day-scale variations in hydrochemistry in the downtown section of the Nanming River after sewage interception; （2） to screen out hydrochemical imprints for indicating hu- man impacts on the Nanming River. Sampling sites were arranged at only two sections, e.g. site 1 （the Sifang River, as the in- let of the downtown section） and site 8 （the Tuanpo Bridge, as the outlet of the downtown section）. Water samples were col- lected on a ten-days scale during the period from October 20, 2008 to October 20, 2009. From the inlet to the outlet, some ma- jor ions such as Na＋, Cl-, NO3-, and SOl- increased by 53%, 65%, 52%, and 47%, respectively. The other ions K＋, Ca2＋ , Mg2＋ and HCO3- showed slight elevations while pH displayed a mild decrease. The peak for Na＋ in June and July most possibly resulted from the widespread use of disinfectants （such as sodium hypochlorite） for the control over bird flu epidemic situation, as verified by a very good positive correlation of Na＋ with C1-. Another piece of evidence was the good negative rela- tion between Na＋ and NO3- , demonstrating adverse effects of disinfectants on ammonifying or nitrifying bacteria responsible for the production or conversion of ammonia and ammonium to nitrite and nitrate. Dry and wet acid deposition originating from the burning of high-sulfur coal was regarded as a main reason for increases in SO4^2-. Those ions pertaining to urban activities, such as Na＋ , Cl- , NO3- and SO4^2- , can be used as hydrochemical imprints.