Novel research identifies fresh 'mixers' in river pollution 'cocktail'


Date:
January 25, 2022
Source:
University of Birmingham
Summary:
Water quality in rivers is affected by underpinning 'natural'
hydrogeological and biogeochemical processes, as well as
interactions between people and their environment that
are accelerating stress on water resources at unprecedented
rates. Pollutants can move at different speeds and accumulate
in varying quantities along rivers where the mix of the complex
'cocktail' of chemicals that is making its way towards the ocean
is constantly changing, a new study reveals.



FULL STORY ==========================================================================

========================================================================== Water quality in rivers is affected by underpinning `natural'
hydrogeological and biogeochemical processes, as well as interactions
between people and their environment that are accelerating stress on
water resources at unprecedented rates.

Pollutants can move at different speeds and accumulate in varying
quantities along rivers where the mix of the complex `cocktail' of
chemicals that is making its way towards the ocean is constantly changing,
a new study reveals.

Researchers have discovered characteristic breakpoints - often found when
a tributary joins the main river or significant point sources exist -
can change the behaviour of some compounds, causing the concentration
of these chemicals to change drastically, depending on where they are
on their journey down the river.

Experts discovered the phenomenon after piloting a new, systematic
approach to understanding hydrogeochemical dynamics in large river systems along the entire length of India's River Ganges (Ganga) - from close to
its source in the Himalayas down to the Indian Ocean.

This new research approach proven successful at the iconic Ganga can
be applied to other large river systems across the world - hopefully
shedding new light on how to tackle the global challenge of aquatic
pollution by multiple interacting contaminants.

Publishing its findings in Water Research, the international research
team, which includes experts from the Universities of Birmingham and
Manchester and other Indian and UK collaborators, reveals that chemicals including nitrate, chloride, sulfate, calcium, sodium and strontium are
cut and boosted in different proportion by a series of breakpoints along
the Ganga.

They found that mixing, dilution and weathering are key processes
controlling major hydrochemistry - identifying four major breakpoints
which alter the concentration of at least four chemicals in the
river. Five minor breakpoints affect the water mix of 2-3 chemicals,
with two `single' locations impacting on just one parameter.

Stefan Krause, Professor of Ecohydrology and Biogeochemistry at the
University of Birmingham, commented: "Large river systems, such as
the Ganga, provide crucial water resources with important implications
for global water, food and energy security. Understanding the complex
dynamics of such systems remains a major challenge.

"The breakpoints we have identified in India change the behaviour of
some compounds, altering the composition of the cocktail of chemicals
flowing down the Ganga to the ocean.

"Breakpoint analysis could be a game changer in understanding how
pollutants travel along major watercourses - allowing us to identify the `hotspots' which will shed new light on the behaviour of aquatic pollution
and how better to tackle this global challenge." Informed by a 2019 post-monsoonal survey of 81 bank-side sampling locations, researchers identified five major hydrogeochemical zones - characterised, in part,
by the inputs of key tributaries, urban and agricultural areas, and
estuarine inputs near the Bay of Bengal.

Dr Laura Richards, the study's lead author from the University
of Manchester, commented: "Our research helps to understand the
downstream transitions in the chemistry of the River Ganga providing
important baseline information and quantification of solute sources and controls. In addition to improving the understanding of a river system
as environmentally and societally important as the Ganga, the systematic approach used may also be applicable to other large river systems."
The researcher's novel research approach brings systematic insight into
the factors controlling key geochemistry in the Ganga - one of the world's largest and most important river systems, flowing over 2,500 km from the Himalayas to the Bay of Bengal, through one of the world's most densely populated areas.

As a major source of livelihood, the river is a key water source
to more than 400 Million people and very important to many social
and religious traditions in India, but faces increasing environmental challenges associated with rapid development, climate change, increasing urbanisation, water demand and agricultural intensity.

This work was undertaken as part of a partnership between Indo-UK
projects and the following support is acknowledged: NERC-DST Water Quality Projects FAR- GANGA NE/R003386/1 & DST/TM/INDO-UK/2K17/55(C) & 55(G) to
Polya et al; Water Quality TEST NE/R003106/1 & DST/TM/INDO-UK/2K17/30 to Reynolds et al.; NE/ R000131/1 to Jenkins et al.; and 100 Plastic Rivers
(The Leverhulme Trust) to Krause et al.

========================================================================== Story Source: Materials provided by University_of_Birmingham. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Laura A. Richards, Bethany G. Fox, Michael J. Bowes, Kieran
Khamis, Arun
Kumar, Rupa Kumari, Sumant Kumar, Moushumi Hazra, Ben Howard,
Robin M.S.

Thorn, Daniel S. Read, Holly A. Nel, Uwe Schneidewind, Linda K.

Armstrong, David J.E. Nicholls, Daniel Magnone, Ashok Ghosh,
Biswajit Chakravorty, Himanshu Joshi, Tapan K. Dutta, David
M. Hannah, Darren M.

Reynolds, Stefan Krause, Daren C. Gooddy, David A. Polya. A
systematic approach to understand hydrogeochemical dynamics in
large river systems: Development and application to the River
Ganges (Ganga) in India. Water Research, 2022; 211: 118054 DOI:
10.1016/j.watres.2022.118054 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220125092959.htm

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