scholarly journals Arsenic contamination of groundwater in the Kathmandu Valley, Nepal, as a consequence of rapid erosion

2010 ◽  
Vol 40 ◽  
pp. 49-60 ◽  
Author(s):  
Steven H. Emerman ◽  
Tista Prasai ◽  
Ryan B. Anderson ◽  
Mallory A. Palmer
Keyword(s):  
Geometric Mean ◽  
Sulfide Oxidation ◽  
River System ◽  
Flood Plain ◽  
Kathmandu Valley ◽  
Ganges River ◽  
Transition Elements ◽  
Dug Wells ◽  
The Ganges ◽  
System Water

Elevated levels of arsenic (As) in groundwater in the flood plain of the Ganges River have been well-documented over the past decades. The objective of this study was to measure As and the transition elements normally associated with As in the Kathmandu Valley in Nepal, a heavily populated tectonic valley in the upper reaches of the Ganges River system. Water samples were collected from six shallow tubewells (depth < 50 m), eight deep tubewells and 13 dug wells and stone spouts. Electrical conductivity, temperature and pH were measured on-site and concentrations of As, Fe, Cu, Ni, Co, Mn, Zn and Cr were measured with a spectrophotometer. Five tubewells and four dug wells had As levels exceeding the Nepal Interim Standard (As = 0.05 mg/L). There was no statistically significant clustering of As levels either with depth or horizontal location. Arsenic was uncorrelated with either Fe (R2 = 0.096), Mn (R2 = 0.0004) or any combination of transition elements (R2 < 0.083), which is inconsistent with both the reduction-dissolution and the sulfide oxidation models for As release. The geometric mean As level of groundwater (As = 0.015 mg/L) was indistinguishable from the geometric mean As level of surface water (As = 0.013 mg/L) obtained from 48 river samples from the Kathmandu Valley in a previous study. We are suggesting that elevated groundwater As results not from subsurface redox conditions, but from losing streams with elevated As, which is a consequence of rapid erosion caused by a combination of monsoon climate, tectonic uplift and deforestation.

scholarly journals Support for the fluvial recharge model for arsenic contamination of groundwater in Pokhara Valley, Nepal Himalaya

2013 ◽  
Vol 46 ◽  
Author(s):  
Steven H. Emerman ◽  
Kevin L. Stuart ◽  
Ajit Sapkota ◽  
Sabina Khatri ◽  
Basanta Raj Adhikari ◽  
...  
Keyword(s):  
Surface Water ◽  
Geometric Mean ◽  
Sulfide Oxidation ◽  
Kathmandu Valley ◽  
Ganges River ◽  
Transition Elements ◽  
Nepal Himalaya ◽  
Dug Wells ◽  
Pokhara Valley ◽  
The Ganges

Elevated levels of As in groundwater in the floodplain of the Ganges River have been well-documented over the past 15 years. Recent studies have shown that elevated groundwater As occurs even in Kathmandu Valley in Nepal, a tectonic valley well upstream of the floodplain of the Ganges River. Moreover, studies in Kathmandu Valley showed surface water As to be statistically indistinguishable from groundwater As, which led to the fluvial recharge model in which elevated groundwater As results from losing streams (streams that recharge groundwater) with elevated As, which is a consequence of rapid erosion caused by a combination of monsoon climate, tectonic uplift and deforestation. The objective of this study was to further test the fluvial recharge model and other existing models in Pokhara Valley, another tectonic valley in Nepal Himalaya far upstream from the floodplain of the Ganges River. In November 2010 water samples were collected from 20 hand-dug wells (depths 2-18 m), 12 borings (depths 34-220 m), four springs, 16 streams, three lakes and two caves. Arsenic concentrations in all but one of the 57 samples (a stream) exceeded the WHO As Standard (As= 0.01 mg/L). The As concentration of all surface water (geometric mean As = 0.067 mg/L) was statistically indistinguishable (P = 0.43) from that of all groundwater (geometric mean As = 0.086 mg/L), which is consistent with the fluvial recharge model. Groundwater As was uncorrelated with either sulfate or any combination of the transition elements, which is inconsistent with both the reductive-dissolution and sulfide-oxidation models.

scholarly journals Stable Strontium Isotopic Compositions of River Water, Groundwater and Sediments From the Ganges–Brahmaputra–Meghna River System in Bangladesh

2021 ◽  
Vol 9 ◽  
Author(s):  
Toshihiro Yoshimura ◽  
Shigeyuki Wakaki ◽  
Hodaka Kawahata ◽  
H. M. Zakir Hossain ◽  
Takuya Manaka ◽  
...  
Keyword(s):  
River Water ◽  
Chemical Weathering ◽  
Drainage Basin ◽  
Dissolution Kinetics ◽  
River System ◽  
Ganges River ◽  
Brahmaputra River ◽  
Terrestrial Water ◽  
Stable Strontium ◽  
The Ganges

The Sr isotopic composition of rivers and groundwaters in the Bengal Plain is a major contributor to the global oceanic Sr inventory. The stable strontium isotope ratios (δ88Sr) provide a new tool to identify chemical weathering reactions in terrestrial water. In this study, we investigated the spatiotemporal variations of δ88Sr in samples of river water, bedload sediment, and groundwater collected from the Ganges–Brahmaputra–Meghna drainage basin in Bangladesh, which is known to strongly influence the 87Sr/86Sr ratio in seawater. The average δ88Sr values of waters of the Ganges, Brahmaputra, and Meghna rivers were 0.269, 0.316, and 0.278‰, respectively. Our data showed little difference between seasons of high and low discharge. The δ88Sr values measured in sequential leaching fractions of sediments varied from –0.258 to 0.516‰ and were highest in the silicate fraction, followed in turn by the carbonate fraction and the exchangeable fraction. Both 87Sr/86Sr and δ88Sr of these waters are primarily controlled by the inputs of Sr in weathering products from the Bengal Plain and Sr from the Himalayan rivers (Ganges and Brahmaputra). Values of δ88Sr and Sr/Ca were higher in the Brahmaputra River than in the Ganges River, a difference we attribute to greater input from silicate weathering. The variations of δ88Sr and 87Sr/86Sr were greater in groundwater than in river waters. Mineral sorting effects and dissolution kinetics can account for the large scatter in 87Sr/86Sr and δ88Sr values. The depth profile of δ88Sr showed wide variation at shallow depths and convergence to a narrow range of about 0.31‰ at depths greater than 70 m, which reflects more complete equilibration of chemical interactions between groundwater and ambient sediments owing to the longer residence time of deeper groundwater. We found that δ88Sr values in the groundwater of Bangladesh were almost identical to those of river water from the lower Meghna River downstream of its confluence with the Ganges–Brahmaputra river system, thus confirming that the δ88Sr composition of the groundwater discharge to the Bay of Bengal is very similar to that of the river discharge.

scholarly journals The Influence of Weathering, Water Sources, and Hydrological Cycles on Lithium Isotopic Compositions in River Water and Groundwater of the Ganges–Brahmaputra–Meghna River System in Bangladesh

2021 ◽  
Vol 9 ◽  
Author(s):  
Toshihiro Yoshimura ◽  
Daisuke Araoka ◽  
Hodaka Kawahata ◽  
H. M. Zakir Hossain ◽  
Naohiko Ohkouchi
Keyword(s):  
River Water ◽  
Rainy Season ◽  
Global Climate ◽  
River System ◽  
Mineral Formation ◽  
Ganges River ◽  
Secondary Mineral ◽  
Li Isotope ◽  
Secondary Mineral Formation ◽  
The Ganges

The silicate weathering of continental rocks plays a vital role in determining ocean chemistry and global climate. Spatiotemporal variations in the Li isotope ratio (δ7Li) of terrestrial waters can be used to identify regimes of current and past weathering processes. Here we examine: 1) monthly dissolved δ7Li variation in the Ganges River’s lower reaches; and 2) the spatiotemporal variation of river water of the Brahmaputra, Meghna rivers, and groundwater in Bangladesh. From the beginning to maximum flood discharges of the rainy season (i.e., from June to September), Li concentrations and δ7Li in the Ganges River show remarkable changes, with a large influence from Himalayan sources. However, most Li discharge across the rainy season is at steady-state and strongly influenced by the secondary mineral formation in the low-altitude floodplain. Secondary mineral formation strongly influences the Meghna River’s Li isotopic composition along with fractionation lines similar to the Ganges River. A geothermal input is an additional Li source for the Brahmaputra River. For groundwater samples shallower than ∼60 m depth, both δ7Li and Li/Na are highly scattered regardless of the sampling region, suggesting the variable extent of fractionation. For deep groundwater (70–310 m) with a longer residence time (3,000 to 20,000 years), the lower δ7Li values indicate more congruent weathering. These results suggest that Li isotope fractionation in rivers and groundwater depends on the timescale of water-mineral interaction, which plays an essential role in determining the isotopic signature of terrestrial Li inputs to the ocean.

scholarly journals Message in a bottle: Open source technology to track the movement of plastic pollution

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0242459
Author(s):  
Emily M. Duncan ◽  
Alasdair Davies ◽  
Amy Brooks ◽  
Gawsia Wahidunnessa Chowdhury ◽  
Brendan J. Godley ◽  
...  
Keyword(s):  
Open Source ◽  
Bay Of Bengal ◽  
Animal Movement ◽  
Public Awareness ◽  
River System ◽  
Educational Outreach ◽  
Source Tracking ◽  
Ganges River ◽  
Plastic Pollution ◽  
The Ganges

Rivers worldwide are now acting as major transport pathways for plastic pollution and discharge large quantities of waste into the ocean. Previous oceanographic modelling and current drifter data have been used to predict the movement and accumulation of plastic pollution in the marine environment, but our understanding of the transport and fate through riparian systems is still largely unknown. Here we undertook a proof of concept study by applying open source tracking technology (both GPS (Global Positing System) cellular networks and satellite technology), which have been successfully used in many animal movement studies, to track the movements of individual plastic litter items (500 ml PET (polyethylene terephthalate) drinks bottles) through the Ganges River system (known as the Ganga in India and the Padma and Meghna in Bangladesh, hereafter known as the Ganges) and the Bay of Bengal. Deployed tags were successfully tracked through the Ganges river system and into the Bay of Bengal marine system. The “bottle tags” were designed and built (e.g. shape, size, buoyancy) to replicate true movement patterns of a plastic bottle. The maximum distance tracked to date is 2845 km over a period of 94 days. We discuss lessons learnt from the development of these plastic litter tags, and outline how the potential widespread use of this open source technology has the ability to significantly increase understanding of the location of accumulation areas and the timing of large inputs of plastic pollution into the aquatic system. Furthermore, “bottle tags” may act as a powerful tool for stimulating social behaviour change, informing science-based policy, and as valuable educational outreach tools for public awareness.

scholarly journals Benchmarking wide swath altimetry-based river discharge estimation algorithms for the Ganges river system

2016 ◽  
Vol 52 (4) ◽  
pp. 2439-2461 ◽  
Author(s):  
Matthew G. Bonnema ◽  
Safat Sikder ◽  
Faisal Hossain ◽  
Michael Durand ◽  
Colin J. Gleason ◽  
...  
Keyword(s):  
River Discharge ◽  
River System ◽  
Ganges River ◽  
Estimation Algorithms ◽  
Discharge Estimation ◽  
The Ganges ◽  
Wide Swath

Determination of transfer time for sediments in alluvial plains using 238U-234U-230Th disequilibria: The case of the Ganges river system

2012 ◽  
Vol 344 (11-12) ◽  
pp. 688-703 ◽  
Author(s):  
François Chabaux ◽  
Estelle Blaes ◽  
Mathieu Granet ◽  
Raphaël di Chiara Roupert ◽  
Peter Stille
Keyword(s):  
River System ◽  
Transfer Time ◽  
Ganges River ◽  
The Ganges

scholarly journals The effect of surface lithology on arsenic and other heavy metals in surface water and groundwater in Mustang Valley, Nepal Himalaya

2014 ◽  
Vol 47 (1) ◽  
pp. 1-21 ◽  
Author(s):  
Steven H. Emerman ◽  
Janae R. Nelson ◽  
J. Kade Carlson ◽  
Tracy K. Anderson ◽  
Anusha Sharma ◽  
...  
Keyword(s):  
Surface Water ◽  
Water Samples ◽  
Overland Flow ◽  
Geometric Mean ◽  
Ganges River ◽  
Nepal Himalaya ◽  
Groundwater Samples ◽  
Region I ◽  
The Ganges ◽  
Region Ii

Recent studies have shown that elevated groundwater as occurs even in Kathmandu and Pokhara Valleys in Nepal, two tectonic valleys well upstream of the floodplain of the Ganges River. Moreover, studies in both valleys showed surface water As to be statistically indistinguishable from groundwater As, which led to the fluvial recharge model in which elevated groundwater As results from losing streams with elevated As, which is a consequence of rapid erosion caused by a combination of monsoon climate, tectonic uplift and deforestation. The objective of this study was to further test the fluvial recharge model in Mustang Valley, the third major tectonic valley in Nepal Himalaya far upstream from the floodplain of the Ganges River. In May 2011 water samples were collected from 33 surface water sites (24 directly from streams and 9 from canals, pipes or taps fed by streams) and 24 groundwater sites (10 directly from springs and 14 from pipes or taps fed by springs). The WHO As Standard was exceeded in 47% of surface water samples and 79% of groundwater samples, including all nine functioning water taps in Lo-Manthang, the largest village. Separating samples into a high- As Region I (geometric mean As = 0.071 mg/L) and a low-As Region II (undetectable As for 85% of samples) showed that surface water As and groundwater As were statistically indistinguishable within each region. Only Region I receives overland flow from the exposed Mustang and Mugu Granites. The correspondence between groundwater As and watershed surface lithology is further evidence for the fluvial recharge model.

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