Spatial and temporal variation in the major ion composition of the waters in the Brahmaputra River has been measured to understand chemical weathering and the factors controlling these processes. Samples were collected from the Brahmaputra mainstream at five stations Pasighat, Dibrugarh, Tezpur, Guwahati and Dhubri during monsoon and post monsoon seasons. The total dissolved solids in the waters of the Brahmaputra system ranges between 62.5 and 192.5 mgl -1. The (Total dissolved solids) TDS of the Brahmaputra measured in this study are less than the values reported by earlier workers. Gibbs plot was plotted to investigate the dominant process controlling the water chemistry of the Brahmaputra. The plots of TDS vs. (Na + K)/(Ca + Na + K) and TDS vs. indicate that rock weathering is the main process controlling the chemistry of water in the Brahmaputra River. Factor analysis was done to study the factors controlling the water chemistry of the Brahmaputra.
The Brahmaputra is one of the world’s largest rivers, with drainage area of 580,000 sq. km. (50.5% in China, 33.6% in India, 8.1% in Bangladesh and 7.8% in Bhutan). In India, its basin is shared by Arunachal Pradesh (41.9%), Assam (36.3%), Meghalaya (6.1%), Nagaland (5.6%), Sikkim (3.8%) and West Bengal (6.3%). It is a unique river which drains such diverse environments as the cold dry plateau of Tibet, the rain-drenched Himalayan slopes, the landlocked alluvial plains of Assam and the vast deltaic lowlands of Bangladesh. The Brahmaputra, one of the major river systems of the world, is characterized by very high rates of basin erosion, sediment yield, and channel change [
In this study we tried to find spatial and temporal variation in the major ion composition of the waters in the Brahmaputra River to understand water geochemistry, chemical weathering and the factors controlling these processes.
The Brahmaputra drains the Tibetan Plateau of China and is dominated by upland tributaries originating in the Himalayas. The Brahmaputra flows through various rock types including Precambrian metamorphics (high-grade schists, gneisses, quartzites, and metamorphosed limestones), felsic intrusives, and Paleozoic?Mesozoic sandstones, shales and limestones [
The drainage basin of the Brahmaputra System can be divided into five geologically and climatically different sub basins (
1) the high plateau of Tibet;
2) the Eastern Syntaxis;
3) the Mishmi Hills or the Eastern Drainage;
4) the Himalaya Mountains;
Sampling | Coordinates | Monsoon | Post monsoon |
---|---|---|---|
Pasighat | 95˚16'16.79"E 28˚5'57.66"N | 31/07/2013 | 11/01/2014 |
Dibrugarh | 94˚51'48.18"E 27˚27'57.37"N | 31/07/2013 | 26/01/2014 |
Tezpur | 92˚51'23.75"E 26˚36'14.57"N | 31/07/2013 | 26/01/2014 |
Guwahati | 91˚44'36.75"E 26˚11'41.00"N | 31/07/2013 | 12/01/2014 |
Dhubri | 90˚3'18.92"E 25 ˚59'21.72"N | 31/07/2013 | 14/01/2014 |
5) the Indo-Myanmar and Naga-Patkoi Ranges or the Southern Drainage;
6) the plains of Assam and Bangladesh.
Water samples from the Brahmaputra mainstream at five stations (
Soon after their collection, two separate aliquots of 500 ml water were filtered using 0.45 µm nylon membrane Millipore filters. One of the filtered aliquots was acidified with double-distilled HNO3 for cations analysis and the other aliquot was preserved unacidified for anion measurements. In addition, one sample of 250 ml water was collected and stored unfiltered for alkalinity measurements. Temperature and pH of the water samples were measured at site. The water samples were brought to the laboratory for further analysis. Alkalinity was measured by acid titration; Cl, and SO4 by titration; K and Na by flame AAS; and Al, Pb, Fe Ca, Mg, and Si using ICP-AES.
The various parameters measured are given in
The TDS of the Brahmaputra measured in this study is less than the values reported by earlier workers.
Place | Name | pH | EC | Alkalinity | TDS | Hardness | Cl− | Reactive silica | Ca | Fe | Mg | Na | K | Al | Pb | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Pasighat Monsoon | PAS.M | 6.2 | 132.5 | 130.2 | 62.5 | 16.28 | 185 | 56.8 | 2.16 | 22.81 | 1.48 | 3.75 | 2.74 | 1.42 | 1.27 | 0.022 |
Pasighat Post Monsoon | PAS.PM | 7.7 | 221 | 155.4 | 102.5 | 22.21 | 100 | 63.9 | 3.79 | 27.8 | 0.09 | 5.33 | 3.49 | 2.04 | 0.46 | 0.003 |
Dibrugarh Monsoon | DIB.M | 6.2 | 97.5 | 115.4 | 47 | 6.43 | 185 | 71 | 2.4 | 13.52 | 0.23 | 2.3 | 2.17 | 2.34 | 0.38 | 0.013 |
Dibrugarh Post Monsoon | DIB.PM | 7.6 | 187 | 180.6 | 89 | 12.14 | 90 | 71 | 5.49 | 25.41 | 0.11 | 5.51 | 3.25 | 3.23 | 0.43 | 0.001 |
Tezpur Monsoon | TEZ.M | 6.1 | 134 | 180.4 | 63.5 | 11.07 | 157.5 | 60.35 | 1.24 | 4.89 | 0.22 | 0.9 | 0.96 | 1.87 | 0.64 | 0.001 |
Tezpur Post Monsoon | TEZ.PM | 7.2 | 195 | 205.4 | 90.5 | 14 | 90 | 46.15 | 4.72 | 24.6 | 0.17 | 5.43 | 3.42 | 2.65 | 0.52 | 0.002 |
Guwahati Monsoon | GHY.M | 6.1 | 130 | 205 | 63.5 | 11.14 | 185 | 67.45 | 3.27 | 18.2 | 1.91 | 3.44 | 3.03 | 2.78 | 2.15 | 0.022 |
Guwahati Post Monsoon | GHY.PM | 3.3 | 816.5 | 180 | 194.5 | 19.92 | 95 | 37.28 | 5.78 | 27.49 | 0.003 | 6.13 | 3.47 | 2.87 | 0.38 | 0.003 |
Dhubri Monsoon | DHU.M | 6.1 | 88.5 | 217.5 | 44 | 10 | 187.5 | 56.8 | 3.12 | 19.36 | 2.93 | 3.94 | 2.54 | 2.15 | 1.53 | 0.016 |
Dhubri Post Monsoon | DHU.PM | 5.4 | 212.5 | 230 | 98.5 | 14.64 | 90 | 49.2 | 3.88 | 28.29 | 0.06 | 6.78 | 3.43 | 2.82 | 0.39 | 0.001 |
Mean Monsoon | 6.13 | 116.5 | 177.7 | 56.1 | 10.98 | 180 | 62.48 | 2.45 | 15.76 | 1.36 | 2.86 | 2.29 | 2.11 | 1.19 | 0.017 | |
Mean Post Monsoon | 5.67 | 196.06 | 171.1 | 93.44 | 12.69 | 129.8 | 54.07 | 3.26 | 19.58 | 0.81 | 3.97 | 2.63 | 2.23 | 0.83 | 0.009 | |
Standard deviation monsoon | 0.07 | 21.73 | 35.67 | 9.74 | 3.533 | 12.6 | 6.45 | 0.82 | 6.92 | 1.16 | 1.26 | 0.81 | 0.51 | 0.71 | 0.005 | |
Standard deviation post monsoon | 2.09 | 203.64 | 51.12 | 98.4 | 5.22 | 57.5 | 18.12 | 1.56 | 8.01 | 0.95 | 1.91 | 0.94 | 0.74 | 0.57 | 0.008 |
Location | Date | TDS (mg/l) | Reference |
---|---|---|---|
Pasighat | Jul-13 | 62.5 | This study |
Jan-14 | 102.5 | This study | |
Dibrugarh | Apr-82 | 107 | [ |
Oct-99 | 128 | [ | |
Jul-13 | 97 | This study | |
Jan-14 | 119 | This study | |
Guwahati | Jul-79 | 101 | [ |
Jul-00 | 112 | [ | |
Apr-82 | 91 | [ | |
Apr-00 | 111 | [ | |
Dec-82 | 144 | [ | |
Dec-00 | 164 | [ | |
Oct-99 | 102 | [ | |
Jul-14 | 102 | This study | |
12-01-2014 | 194.5 | This study | |
Goalpara | Apr-82 | 92 | [ |
Dec-82 | 147 | [ | |
Dhubri | Jul-00 | 106 | [ |
Aug-13 | 64 | This study | |
Jan-14 | 98.5 | This study |
5. Hu et al., 1982; 4. Chen and Guan, 1981; 7. Sarin et al., 1989; 8. Galy and France-Lanord, 1999; 9. Singh et al., 2005.
In
Gibbs plot [
From the ternary plots (
On the anion plot the samples cluster towards
From factor analysis of various parameters in monsoon and post monsoon showed 4 probable sources with most of the Sodium, Lead, Sulphate, Magnesium, Iron, Aluminum, Calcium, and Chromium coming from source 1. Lead has 3 probable sources and Silicon and Aluminum coming from the same source.
In monsoon Factor 1 explaining 46.95% of the total variance had strong positive loadings (> 0.80) for Sodium, Lead, Sulphate, Magnesium, Iron, Aluminum, Calcium, Chromium. Factor 2 accounts for 23.8% and have strong positive loadings (> 0.70) on Potassium, Chlorine, and hardness and moderate positive loadings on pH and Silicon. Factor 3 accounts for 17.82% of the total variance and shows positive loadings for EC and alkalinity. Factor 4 accounts for 11.3% of the total variance.
For post monsoon 4 factors were obtained through factor analysis, Factor 1 accounted for 40.76% of the total variance and have strong positive loadings with EC, alkalinity, TDS, Sodium, Sulphate, Calcium and Chromium. Factor 2 accounts for 28.79% of the total variance, with positive loadings on Aluminum, Sulphate, Chlorine, and hardness, Lead, Sodium and TDS. Factors 3 correspond to 18.18% of the total variance and have positive loadings on Calcium, Silicon, Aluminum, Iron and hardness. Factor 4 accounts for 12.25% of the total variance and have positive loadings on Silicon, Potassium, Chlorine and hardness.
Spatio-temporal variation of the water chemistry of the Brahmaputra River was studied by measuring the physicochemical parameters carried out over a period of 1 year (monsoon and post-monsoon seasons). Though such studies were carried out in the past but none of the studies had recorded both monsoon and post monsoon variations within a year and some studies [
Factor analysis of the various parameters in monsoon-component matrix | ||||
---|---|---|---|---|
Component | ||||
1 | 2 | 3 | 4 | |
Mg | 0.96 | −0.218 | −0.159 | |
Na | 0.947 | 0.215 | −0.286 | |
Ca | 0.902 | −0.177 | −0.159 | −0.359 |
Si | 0.887 | 0.456 | ||
Cr | 0.881 | −0.116 | 0.399 | 0.226 |
Fe | 0.869 | −0.323 | 0.373 | |
Pb | 0.859 | −0.329 | 0.315 | −0.233 |
Al | 0.856 | −0.136 | 0.309 | 0.391 |
SO42- | 0.832 | 0.301 | −0.168 | −0.435 |
TDS | 0.298 | −0.95 | ||
K | 0.273 | 0.79 | 0.471 | 0.283 |
Cl | −0.155 | 0.741 | 0.572 | −0.316 |
Hardness | −0.155 | 0.741 | 0.572 | −0.316 |
EC | −0.184 | −0.7 | 0.688 | |
Alkalinity | −0.127 | −0.669 | 0.724 | 0.106 |
pH | 0.3 | 0.428 | 0.852 | |
% of variance | 46.957 | 23.815 | 17.829 | 11.399 |
Factor analysis of the various parameters in post monsoon-component matrix | ||||
---|---|---|---|---|
Component | ||||
1 | 2 | 3 | 4 | |
EC | 0.866 | −0.339 | 0.236 | 0.282 |
Alkalinity | 0.862 | −0.342 | 0.239 | 0.289 |
Fe | −0.805 | 0.254 | 0.403 | −0.355 |
TDS | 0.786 | 0.613 | ||
Na | 0.771 | 0.362 | −0.11 | −0.513 |
Pb | 0.77 | 0.516 | 0.375 | |
Hardness | −0.686 | 0.492 | −0.197 | 0.497 |
Cl | −0.686 | 0.492 | −0.197 | 0.497 |
K | −0.313 | −0.856 | 0.404 | |
Sulphate | 0.585 | 0.786 | 0.197 | |
pH | −0.235 | −0.699 | −0.32 | −0.595 |
Ca | 0.607 | 0.139 | −0.781 | |
Cr | 0.452 | −0.341 | 0.761 | −0.317 |
Mg | 0.312 | −0.648 | −0.667 | −0.196 |
Si | 0.142 | −0.54 | 0.598 | 0.575 |
Al | −0.489 | 0.476 | 0.579 | −0.446 |
% of variance | 40.764 | 28.79 | 18.189 | 12.258 |
controlling the chemistry of water in the Brahmaputra River. Higher concentration of Calcium and Bicarbonate suggest chemical weathering of carbonates is the predominant process resulting in the production of these ions. From the ternary plot it was found that most of the samples fall towards the Ca apex indicating the dominance of Ca in the cation budget of the Brahmaputra. On the anion plot the samples cluster towards
The authors are thankful to the staff of Department of Environmental Science, Tezpur University for helping in carrying out all the analysis.
Handique, S., Sharma, P., Baruah, K.K. and Tripathi, J.K. (2017) Study on the Spatial and Temporal Variations in the Geochemistry of the Brahmaputra River Water. International Journal of Geosciences, 8, 756-765. https://doi.org/10.4236/ijg.2017.85042