Hydrochemical and Isotopic Characteristics of Irrigation Channel Water in Oil Palm Plantations, Kuala Selangor, Malaysia

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The rapid expansion of oil palm plantation areas in Southeast Asia has brought economic benefits but has also led to substantial environmental challenges due to deforestation and excessive fertilizer use. This study examined the hydro-chemical and isotopic characteristics of water in irrigation channels in oil palm plantations in Kuala Selangor, Malaysia. Water samples demonstrated oxidative environments with pH ranging from 2.67-6.59, EC ranging from 7.27-138 mS/m and DO ranging from 0.46-4.83 mg/L. Channel waters in peatland areas were highly acidic (pH 3.25-3.67), probably because of the presence of humic acids. Isotopic analysis indicated that meteoric water was the primary source of water in the irrigation channels, with isotope fractionation due to water evaporation observed at specific points. The δ¹⁵N and δ¹⁸O values of NO₃^- suggest that the sources of nitrate were primarily ammonia fertilizers and atmospheric deposition. Overall, these findings imply that after precipitation enters the plantation irrigation water, subsequent evaporation and human activities modify water quality. These results highlight the need for sustainable oil palm management practices to safeguard water resources and mitigate the environmental impacts on surrounding ecosystems.