The Ganga river basin is the fifth largest in the world (1,060,000 km2) and is the main source of freshwater for about half the population of India and Bangladesh (c. 750 million people).  As a consequence of rapid population growth, urbanisation, industrialisation and agricultural development since the 1960s following India’s ‘Green Revolution’, the Ganga river and its major tributaries most notably the Yamuna have become increasingly polluted with a cocktail of persistent organic pollutants, plasticizers and heavy metals.

River sediments are the major pathway whereby contaminants and microbes are dispersed and stored in freshwater aquatic systems.  The source-pathway-receptor relationships of some sediment-associated contaminants, most notably heavy metals released into the environment in large quantities since the Industrial Revolution, are now generally well understood.  However, in the past two decades as a result of the refinement of analytical techniques a new group of emerging contaminants (ECs) – pharmaceuticals, steroids and hormones, flame retardant micro-plastics – have been identified as posing a risk of harm to human and animal health.  In particular, there is a growing concern that antibiotic-resistant microbes (AMs) released into the environment from various sources (e.g. treated and untreated sewage, hospital waste, agricultural runoff and aquaculture discharge), pose a threat to biotic systems. Furthermore, it is now recognised that the environment represents a major pool of antibiotic resistant genes (ARGs) and that aquatic systems can play a key role in the transportation, occurrence and evolution of ARGs as well as influence the prevalence at which ARGs are exchanged amongst bacteria through horizontal gene transfer. Despite this the large-scale and long-term environmental fate of ECs (including AMs and ARGs) in river systems, including their transformation pathways and products, and how river systems affect microbial population dynamics and the dispersal dynamics and biogeography of ARGs across ecosystems, has not been thoroughly explored, particularly within the densely populated large river systems of the Global South.

Our project undertakes the first event-based and catchment-scale (mountain-to-ocean) investigations of sediment-associated ECs, and microbial population dynamics, in river channel and floodplain environments in the Ganga basin, including its major tributaries – Yamuna, Ghaghara and Son rivers.