Assessment of heavy metals, pH and EC in effluent run-off, river and adjacent soil around a floriculture industry in Holeta, Wadera district, Ethiopia

Abstract

Heavy metal contents from effluent run-off, neighboring Holeta River, and adjacent soils around floriculture greenhouses in Holeta town, Ethiopia were determined using Atomic Absorption Spectrophotometer (AAS) to assess their potentialities as pollutants. Samples were taken from four sites for the effluent, two river bank locations and two soil locations about 10 meters apart. The evaluated metals were Cu, Fe, Ni, Mn, Cr, Zn, Cd, Co, and Ag. The pH, EC, TDS, DO were determined in the effluent, river and soil samples while particle size and total carbon contents were determined in the soil sample. Results showed that levels of heavy metals were higher in the soil sample than in the effluent and river samples. The metal concentrations ranged from 5.6-1309 mg/kg in soil, 0.31-3.43 mg/L in the river sample and 0.09-0.93 mg/L in the effluent. Highest concentration of Fe (1309 mg/kg), Ni (132 mg/kg), Mn (129 mg/kg), Cu (78 mg/kg), Cd (28.5 mg/kg), Co (5.6 mg/kg) and Zn (0.52 mg/kg) were recorded for the soil samples. These values were above permissible levels for agricultural soils. The findings reveal that the effluent and river samples contained low levels of heavy metals, but the high heavy metal concentrations in the soil could seriously influence soil characteristics by contaminating the soil. Since scanty information is available on the impact of floriculture effluent on agricultural soil in this region, the result of this work could provide baseline data for future monitoring of pollution from the floriculture enterprises

Key words: Heavy metals, AAS, contamination, floriculture and effluents.