School of Oceanographic Studies, Jadavpur University, 188 Raja S. C. Mullick Road, Kolkata, West Bengal, 700032, India.
Coastal and Estuarine Environment Research Group, Port and Airport Research Institute, 3-1-1, Nagase, Yokosuka, Kanagawa, 239-0826, Japan.
Environ Sci Pollut Res Int. 2020 Aug;27(24):30093-30107. doi: 10.1007/s11356-020-09254-6. Epub 2020 May 24.
Urbanized rivers flowing through polluted megacities receive substantial amount of carbon from domestic sewage and industrial effluents which can significantly alter the air-water CO flux rates. In this regard, we quantified the partial pressure of CO in the surface water (pCO(water)), air-water CO fluxes, and associated biogeochemical parameters in the Hooghly River, India, flowing through two of the most polluted cities of the country, Kolkata and Howrah, over a complete annual cycle during spring tidal phase (SP) and neap tidal phase (NP). This urbanized part of Hooghly River was always supersaturated with CO having an annual mean pCO(water) and air-water CO flux of ~ 3800 μatm and ~ 49 mol C m year, respectively. Significant seasonal variability was observed for both pCO(water) and air-water CO flux (pre-monsoon, 3038 ± 539 μatm and 5049 ± 964 μmol m h; monsoon, 4609 ± 711 μatm and 7918 ± 1400 μmol m h; post-monsoon, 2558 ± 258 μatm and 4048 ± 759 μmol m h, respectively). Monthly mean pH and total alkalinity varied from 7.482 to 8.099 and from 2437 to 4136 μmol kg, respectively, over the annual cycle. pCO(water) showed significant positive correlation with turbidity and negative correlation with electrical conductivity and gross primary productivity (GPP). High water discharge could have facilitated high turbidity, especially during the monsoon season, which led to depletion in GPP and enhancement in pCO(water) which in turn led to very high CO effluxes. The CO efflux rate in this urbanized riverine stretch was substantially higher than that observed in previous studies carried out in the less urbanized estuarine stretch of Hooghly. This indicates that the presence of highly urbanized and polluted metropolis potentially enhanced the pCO(water) and CO effluxes of this river. Similar observations were made recently in some Asian and Australian urban rivers.
流经污染严重的特大城市的城市化河流从生活污水和工业废水中吸收大量碳，这会显著改变空气-水 CO 通量。在这方面，我们量化了印度胡格利河在春季潮汐阶段（SP）和小潮潮汐阶段（NP）期间通过该国两个污染最严重的城市加尔各答和豪拉的空气-水 CO 通量和相关生物地球化学参数的地表水（pCO（water））、空气-水 CO 通量和相关的生物地球化学参数。胡格利河的这个城市化部分始终处于 CO 过饱和状态，其年度平均 pCO（water）和空气-水 CO 通量分别约为 3800 μatm 和 49 mol C m year。pCO（water）和空气-水 CO 通量都表现出显著的季节性变化（前季风期为 3038 ± 539 μatm 和 5049 ± 964 μmol m h；季风期为 4609 ± 711 μatm 和 7918 ± 1400 μmol m h；后季风期为 2558 ± 258 μatm 和 4048 ± 759 μmol m h）。整个年度周期内，每月平均 pH 值和总碱度分别在 7.482 到 8.099 之间和 2437 到 4136 μmol kg 之间变化。pCO（water）与浊度呈显著正相关，与电导率和总初级生产力（GPP）呈显著负相关。高水流可能促进了高浊度，尤其是在季风季节，这导致 GPP 消耗和 pCO（water）增加，从而导致 CO 排放通量非常高。这条城市化河流的 CO 排放率明显高于之前在胡格利河非城市化河口段进行的研究中观察到的排放率。这表明高度城市化和污染严重的大都市的存在可能会增强这条河流的 pCO（water）和 CO 排放。最近在一些亚洲和澳大利亚的城市河流中也观察到了类似的情况。
