INVESTIGATION OF TEMPORAL VARIATION OF NEPHROTOXINS IN GROUNDWATER, NORTH CENTRAL PROVINCE, SRI LANKA

Annually 1400 people in Sri Lanka fall victim to kidney failure and untimely death due to Chronic Kidney Disease of Unknown etiology (CKDU), almost exclusively in areas where groundwater supplies the majority of drinking and cooking water. It is estimated about 22,000 people have died over the past two decades only in the North Central Province (NCP) of Sri Lanka.. The cause of CKDU remains uncertain despite 25 years of study, although medical analysis of affected kidneys points to environmental nephrotoxins. Earlier studies suggested affected patients exhibit elevated levels of As and Cd in hair and urine, but not in grab samples of food or ground water. Later studies failed to corroborate this link. No studies have yet investigated the temporal variation of ground water chemistry. Via monthly monitoring of groundwater chemistry, our study examines the possibility that annual variations in groundwater nephrotoxins may be a contributing factor. Studies elsewhere observed annual As concentration fluctuations of an order of magnitude (100 to 1200 µg/L, Jianghan Plain China, Schaefer et al, 2016). The NCP region experiences two wet and two dry periods annually, and we expect cycling of subsurface redox state and nephrotoxin mobility can be driven by extreme recharge variation between monsoon and dry season.

In the endemic CKDU area groundwater salinity (Total Dissolved Solids, TDS) ranges from 460 ppm to 888 ppm. Wells typically extend to 100 m depth, the upper 25 m in alluvium and the remainder in fractured and weathered metamorphic bedrock. Field tests found no evidence for bacterial contamination, except in one reservoir frequented by water buffalo. Residents are fearful of consuming groundwater, and have turned to small Reverse Osmosis (RO) plants for drinking water supply. RO waste water (TDS 949 ppm) is dumped at the ground surface for disposal, potentially raising groundwater TDS locally, and more importantly magnifying any shallow groundwater contaminant risk. Initial monitoring indicates TDS is remarkably variable with time in NCP wells, except near one RO plant where near-constant moderately elevated TDS may be controlled by RO brine disposal.