Geochemical characteristics of groundwater in different climatic zones of Sri Lanka

Abstract

Sri Lanka is characterized by well-demarcated climatic zones based on the rainfall pattern known as wet zone, dry zone and intermediate zone. Groundwaters in these three zones are extracted mainly for drinking and irrigation from metamorphic hard rock aquifers and saprolite developed on metamorphic rocks. Detailed hydrogeochemical investigations were carried out covering these three climatic zones in order to characterize the groundwater. A total of 166 groundwater samples were collected representing three climatic zones and analyzed for their major and trace element geochemistry. The results indicate a clear difference in the geochemistry of groundwater between climatic regions, whereas semiarid dry zone groundwater is characterized with higher dissolved mineral contents compared that of the wet and intermediate zones.Low pH levels were noticed in the wet zone areas, while high calcium and fluoride contents were observed in the dry and intermediate terrains. Remarkably, high phosphate contents were observed in all three regions, indicating the influence of fertilizer application on groundwater. Particularly in the dry zone regions, the groundwater chemistry is mainly controlled by rock-water interactions and ion exchange processes in which high mineral contents are added from underlying metamorphic rocks to the drinking and irrigation water. The results indicate that groundwater in the dry zone area is under stress compared to other climate areas, but in the wet zone groundwater shows remarkable influence of anthropogenic activities.

Classification of Groundwater Suitability for Irrigation in the Ulagalla Tank Cascade Landscape by GIS and the Analytic Hierarchy Process

“…Hence, the mineral composition depends mainly on the metamorphic rocks. This indicates the influence of mineral dissolution associated with seasonal rainfall and anthropogenic activities [47]. Cl − content showed wide variation (20 to 2120 mg/L; Table 4).…”

“…This result shows the "first-flush" phenomenon. Particularly in dry zones, salts tend to accumulate on the soil surface with evaporation [47]. This situation was aggravated at the end of the Yala season, as no rainfall was recorded in August or September (Figure 7).…”

“…This situation was aggravated at the end of the Yala season, as no rainfall was recorded in August or September (Figure 7). These accumulated salts washed off in the heavy rain during the period October-November, when heavy rain can fall in thunderstorms on many parts of the island [47], causing a clear deterioration in irrigation water quality ( Figure 6). A similar pattern was observed during the Yala season.…”

Fluoride and hardness in groundwater of tropical regions - review of recent evidence indicating tissue calcification and calcium phosphate nanoparticle formation in kidney tubules

“…This needs further study, supported by geochemical mapping of Ca 2+ and Mg 2+ and their ratios in the groundwater. In the dry zone of Sri Lanka where the CKDu prevalence is high, the average Mg 2+ content in the groundwater is 35.7 mg/L as compared to the Mg 2+ content of 9.65 mg/L in wet zone where the CKDu incidence is insignificant (Rubasinghe et al, 2015). This indicates the need for a detailed study of Mg and its role in CKDu.…”

“…3under physiological conditions. In the case of Sri Lanka, PO 4 3levels in groundwater are high due to the alarmingly excessive application of phosphate fertilizers (Dissanayake and Chandrajith, 2009b;Rubasinghe et al, 2015). Since the drinking water of the affected population of the dry zone of Sri Lanka consume large quantities of such water, their body burden of the ions may be excessive and which may have a significant impact on kidney tubular damage.…”