Centre for Earth Science Studies, Thiruvananthapuram 695031, Kerala, India.
Environ Monit Assess. 2012 Mar;184(3):1541-57. doi: 10.1007/s10661-011-2059-x. Epub 2011 May 5.
The southwestern coast of India is drained by many small rivers with lengths less than 250 km and catchment areas less than 6,500 km(2). These rivers are perennial and are also the major drinking water sources in the region. But, the fast pace of urbanization, industrialization, fertilizer intensive agricultural activities and rise in pilgrim tourism in the past four to five decades have imposed marked changes in water quality and solute fluxes of many of these rivers. The problems have aggravated further due to leaching of ionic constituents from the organic-rich (peaty) impervious sub-surface layers that are exposed due to channel incision resulting from indiscriminate instream mining for construction-grade sand and gravel. In this context, an attempt has been made here to evaluate the water quality and the net nutrient flux of one of the important rivers in the southwestern coast of India, the Manimala river which has a length of about 90 km and catchment area of 847 km(2). The river exhibits seasonal variation in most of the water quality parameters (pH, electrical conductivity, dissolved oxygen, total dissolved solids, Ca, Mg, Na, K, Fe, HCO(3), NO(2)-N, NO(3)-N, P[Formula: see text], P[Formula: see text], chloride, SO(4), and SiO(2)). Except for NO(3)-N and SiO(2), all the other parameters are generally enriched in non-monsoon (December-May) samples than that of monsoon (June-November). The flux estimation reveals that the Manimala river transports an amount of 2,308 t y(-1) of dissolved inorganic nitrogen, 87 t y(-1) dissolved inorganic phosphorus, and 9246 t y(-1) of SO(4), and 1984 t y(-1) K into the receiving coastal waters. These together constitute about 23% of the total dissolved fluxes transported by the Manimala river. Based on the study, a set of mitigation measures are also suggested to improve the overall water quality of small catchment rivers of the densely populated tropics in general and the south western coast in particular.
印度西南海岸有许多长度小于 250 公里且集水面积小于 6500 平方公里的小河。这些河流常年有水，也是该地区的主要饮用水源。但是，过去四、五十年间城市化、工业化、化肥密集型农业活动的快速发展以及朝圣旅游业的兴起，给许多河流的水质和溶质通量带来了显著变化。由于有机（泥炭）不透水下覆层因河流开采建筑用沙和砾石而被侵蚀，导致其中的离子成分淋溶，这些问题进一步加剧。在此背景下，本文尝试评估印度西南海岸一条重要河流——马尼拉河的水质和净养分通量。该河全长约 90 公里，集水面积 847 平方公里。该河的大多数水质参数（pH 值、电导率、溶解氧、总溶解固体、Ca、Mg、Na、K、Fe、HCO3-、NO2-N、NO3-N、P[Formula: see text]、P[Formula: see text]、Cl-、SO4 和 SiO2）都呈现季节性变化。除了 NO3-N 和 SiO2 外，非季风期（12 月至 5 月）的样本中大多数参数都比季风期（6 月至 11 月）的样本更为丰富。通量估计显示，马尼拉河每年向受纳海域输送 2308 吨溶解无机氮、87 吨溶解无机磷和 9246 吨 SO4 和 1984 吨 K。这些共同构成了马尼拉河总溶解通量的约 23%。基于该研究，还提出了一系列缓解措施，以改善人口稠密热带地区的小流域河流和印度西南海岸的整体水质。
