Effect of refuse dumps on the physico-chemical properties of surface water, ground water and soil in Owo township, Ondo state, Nigeria

Abstract

The pollution effect of refuse dumps at Owo township was investigated. The pH of soil samples from refuse dumping sites were 8.0, 9.0, 8.0, 8.0 with the last value serving as a control. The concentrations of organic matter were 1.10, 1.60, 2.0, and 0.7%, respectively, while the nitrogen concentrations were 0.3, 0.4, 0.6, and 0.2%. The soil concentrations (mg kg⁻¹) of the 12 elements, namely, P, Ca, Mg, Na, K, Pb, Cu, Fe, Mn, Zn, Cr, and Ni for the respective four sites were P (4.1, 17.6, 55.0, 31.3); Ca (3040, 3720, 2840, 1467); Mg (624, 1704, 480, 175); Na (7613, 12, 13); K (48, 435, 81, 68); Pb (0.5, 0.4, 0.4, 0.6); Cu (0.8, 0.5, 05, 06); Fe (2.2, 0.5, 7.8, 3.3); Mn (0.5, 1.8, 7.8, 3.3); Zn (19.8, 17.5, 10.3, 16.3); Cr (0.3, 0.0, 0.0, 0.4); and Ni (0.0, 0.0, 0.0, 0.0,). Physico-chemical parameters were obtained from two streams and three wells, with two of the wells very close to the dumping sites and the third well serving as a control. The respective values obtained were of temperature (26.8°C, 26.5°C, 26.9°C, 26.5°C, 26.9°C) and pH (6.0, 7.1, 6.2, 6.7, 5.6). Other values in mg L⁻¹ were TDS (40, 60, 31, 167, 125); TH (80.0, 104.0, 78.0, 92.0, 38.7); Cl (31.0, 36.4, 30.0, 43.5, 20.4); ALK (26.7, 25.0, 25.0, 25.0, 20.0); TSS (95, 100, 160, 154, 105); TS (135, 160, 482, 320, 240); Acidity (1.00, 0.20, 1.70, 1.40, 0.30); Free CO₂ (0.4, 0.6, 0.6, 3.0); DO (1.4, 2.0, 2.0, 1.0, 3.0); BOD (144, 120, 120, 136, 102), Na (7.0, 8.0, 12.0, 8.0, 8.0); K (26.0, 32.0, 32.0, 32.7, 11.0); Pb (0.0, 0.4, 0.4, 0.0, 0.4); Cu (0.4, 0.4, 0.2, 0.4, 0.2); Fe (1.2, 1.1, 0.9, 0.7, 1.4); Mn (0.4, 0.0, 0.3, 0.0, 0.0); Zn (2.0, 1.9, 2.8, 4.3, 2.5); NO⁻ ₃ –N (31.0, 24.0, 10.0, 16.7,10.0); PO³⁻ ₄ –P (0.01, 0.12, 0.70, 0.70, 0.02); SO²⁻ ₄ –S (48.0, 59.0, 12.0,12.0, 16.7). The microbial load was 343.01, 882.0, 578.0, 1368.7, 532 cfu cm⁻¹ and electrical conductivities were 30, 45, 200, 150, 100 µs cm, respectively. All experiments were carried out in triplicate. The organic matter of the soil in all sites falls within the FAO standard of 1.5–3.0%. The values of organic nitrogen of all sites were higher than the FAO standard, which ranged from 0.08 to 0.15%. This indicates soil pollution at the sites. The streams and wells were not highly polluted possibly because the wells were reasonably deep and the streams were flowing water, which constantly washed away the pollutants. Microbial load is very high in all the water samples. Water from the stream and wells therefore needs to be chemically treated before being suitable for drinking.

Keywords:

• soil
• surface
• refuse
• ground
• water
• dumping