The environmental chemistry of rainwater in Sri Lanka

Abstract

Rainwater samples collected from different parts of Sri Lanka have been analyzed for their chemical constituents. It was observed that except for minor occurrences, "acid-rain" is still not prevalent in Sri Lanka. Based on the chemical composition, the rainwater of Sri Lanka has been classified chemically into eight different types, the most dominant being Ca/Mg-HCO 3 , Ca-Cl and non-dominant cation-HCO 3 types. The wet zone of Sri Lanka, particularly the areas around the central highlands, form a special zone in that a number of chemically different rainwater types can be found in these regions. In contrast, the dry zone of Sri Lanka receives four distinct types of rainwater and conform to geographical zones.

The influence of water–rock interactions on household well water in an area of high prevalence chronic kidney disease of unknown aetiology (CKDu)

“…4a display an increase in δ 13 C DIC without an increase in 87 Sr/ 86 Sr ratios. While carbonates are not expected to comprise a large portion of the geology in the region, they weather more readily with the input of the naturally weakly acidic rainwater, and thus can be a large source of Sr. Dissanayake and Weerasooriya 54 report weakly acidic rainwater pH values of <5.5 in the study region, which is supported by the pH value of 4.9 observed in sample 30 from 54 . Points above the line indicate enrichment in the major ion compared to chloride, suggesting that the source of the ion is from mineral weathering rather than rainwater.…”

“…The modelled phases were organic matter (CH 2 O), CO 2 (g), hornblende, Mg/Na Ex, MgSiO 3 , SiO 2 , NaCl (from atmospheric sources), biotite, Ca/Na exchange and calcite. The pH and major ion (Ca, Mg, Na, K, Cl and SO 4 ) concentrations from a rainwater sample from Vavuniya, also located within the Dry Zone approximately 23 km north of the study area, was used as the initial water 54 . The system is assumed to be receiving piston flow recharge and the groundwater system is in chemical equilibrium.…”

Model assessment of acid deposition potential by SOx in Sri Lanka

“…In an earlier study, rainwater acidity was not considered as a problem in Sri Lanka. Average rainwater pH values of 5.15 and 5.60 have been determined for the Wet and Dry Zones of Sri Lanka with 66 % of the samples having a pH < 5.60, and hence can be considered as acid rain (Dissanayake & Weerasooriya, 1985).…”

Medical geology - a futuristic scientific discipline

“…Geology, notably the discovery of the "fluoride belt" in the dry zone where fluoride was found in excessive concentrations in the groundwater in large areas of the north central regions, Uva and extending towards the deep south (Dissanayake and Weerasooriya, 1985). This belt coincided with a very high incidence of dental and skeletal fluorosis, the former in large numbers of school children.…”

“…The publication of the book "Introduction to Medical Geology-focus on tropical environments" published by Springer is the first of its kind and has attracted global attention on the new discipline and it is indeed heartening to note that the book is listed as a text book in universities in U.S.A, India and Iran among other countries. A geochemical atlas showing the distribution of chemical species in groundwater or soil is a national need for any country and the first Hydrogeochemical Atlas of Sri Lanka (Dissanayake and Weerasooriya, 1985), has greatly benefitted researchers in several disciplines including dental and medical experts.…”