<![CDATA[Organophosphate pesticide use in rice cultivation may leave residues in soil and water and interact with runoff, erosion, water management, and organic-matter decomposition. This descriptive observational study examined chlorpyrifos residues in water and soil and evaluated paddy-water quality in Lalan District, Musi Banyuasin Regency, South Sumatra. Rice-growing sites in Sari Agung, Mulya Jaya, and Sukajadi villages were selected purposively. Six composite soil samples and three water samples were analysed for chlorpyrifos using liquid chromatography-mass spectrometry according to an internal laboratory method, while nine water samples coded 1A-3C were analysed for total suspended solids (TSS), pH, five-day biochemical oxygen demand (BOD₅), and chemical oxygen demand (COD). Data were summarised descriptively and compared with the Class I river-water criteria applied by the laboratory. Chlorpyrifos was detected in all water samples at 0.0023-0.0560 mg/L and in all soil samples at 5.4175-73.7173 mg/kg. TSS ranged from 20 to 410 mg/L, pH from 3.26 to 5.83, BOD₅ from 0.73 to 19.8 mg/L, and COD from 2 to 60 mg/L. Four of nine samples exceeded the TSS criterion, all samples were below the pH range of 6-9, seven exceeded the BOD₅ criterion, and six exceeded the COD criterion. The findings indicate chlorpyrifos contamination and substantial water-quality pressure. TSS was the most relevant parameter for explaining the potential particle-associated transport of chlorpyrifos, whereas pH, BOD₅, and COD characterised general water conditions and were not compound-specific indicators of organophosphate contamination. Because the residue and water-quality datasets were not paired spatially and temporally, causal relationships and quantitative correlations could not be established.]]>
