Heavy metals in sediments of the Yarlung Tsangbo and its connection with the arsenic problem in the Ganges–Brahmaputra Basin

Abstract

The Yarlung Tsangbo (YT) is a large river running across southern Tibet and has significant effects on its lower reaches, the Ganges-Brahmaputra Basin. In order to investigate the geochemical features of the YT, 18 surface sediment samples were collected; ten trace element concentrations were measured for bulk sediments and two fine grain size fractions. Meanwhile, basic physicochemical parameters and element concentrations of river water were also analyzed. Results indicated that the river water was alkaline (pH 8.42) and that dissolved oxygen was mainly controlled by river water temperature. Some elements (e.g., Zn and Ni) showed close negative relationship to mean grain size of the sediments. Concentrations of most heavy metals, except As of the YT bulk sediments, were similar to those of Upper Crustal Concentration and its lower reaches, indicating almost no anthropogenic impact. Arsenic of the YT sediments was derived fundamentally from the parent rocks of the YT Basin and was far higher than that of its lower reaches. This indicates that relatively small amounts of As from the study area were transported down to the Brahmaputra River under present, relatively dry climatic conditions. However, more YT sediments might have been transported to its low reaches during the Holocene due to the wet climate, giving high As concentration in Holocene sediments of the Ganges-Brahmaputra Basin. Thus, As transported by the YT may produce important influence on the Ganges-Brahmaputra Basin and contribute to its high As concentration in groundwater.

Present to future sediment transport of the Brahmaputra River: reducing uncertainty in predictions and management

“…This consistency, despite different methods and input data, builds confidence in the expected relative changes and implies that management applications where such information is sufficient to enable future adaptive measures should at least consider these values as appropriate starting points. Some examples of areas where confidence in relative changes may allow a first-order planning for adaptation include agricultural practices [such as rice plantations that need sediment deposition for fertilization (Prokop and Ploskonka 2014)], mobilization of upstream arsenic sediments (Li et al 2011), and siltation of the river, which puts pressure on riverine ecology. Compared to other basins, the Brahmaputra is still rather unchanged by anthropogenic activities and has a very large potential for incorporating environmental protection into development plans.…”

Evaluating ecological risks and tracking potential factors influencing heavy metals in sediments in an urban river

“…River sediments have been identified as important carriers and sinks for the heavy metals discharged into the aquatic systems [4,5]. Heavy metals in river sediments mainly stem from rock weathering, soil erosion, runoff from agriculture, sewage treatment, and atmospheric precipitation [6,7]. The heavy metals loaded into the river environment can be transferred to and concentrated in sediments together with organic matter, Fe/ Mn oxides, and sulfides by adsorption and accumulation on suspended fine-grained particles, however they cannot be permanently fixed in sediments [8][9][10].…”

Ecological risk evaluation in bottom-surface sediments and sub-surface water in the subtropical Meghna estuarine system

“…Among the three rivers, the Meghna river is in the lower part and connected to the Bay of Bengal. Almost all the rivers and tributaries' of Bangladesh and even Indian rivers are connected to the Meghna river ( Li et al., 2011 ). Besides, all the sediment and wastage falling have a final destination: rivers, including the Meghna river, ultimately to the Bay of Bengal.…”