EVALUATION OF THE LEVELS OF PHTHALATE ESTERS IN WATER, SEDIMENT AND PRAWN (Macrobrachium vollenhovenii) FROM OVIA RIVER, EDO STATE

ABSTRACT

Phthalate esters (PEs) are widely used industrial raw materials that are established environmental contaminants which consequently have adverse endocrine disrupting effects on aquatic organisms and on human health. This study was carried out to evaluate the levels of PEs in water, sediment and prawn (Macrobrachium vollenhovenii) samples from Ovia River. Water, sediment and prawn samples were collected monthly from August 2020 to January 2021 from three sampling stations. Analysis of the levels of dimethyl phthalate (DMP), diethyl phthalate (DEP), di-butyl phthalate (DBP), di-ethyl hexyl phthalate (DEHP), butyl benzyl phthalate (BBP) and di-n-octyl phthalate (DnOP) in the environmental samples was done using Gas Chromatography/Mass Spectrometer (GC/MS). Physicochemical parameters (Temperature, pH, Dissolved Oxygen and Conductivity) of the water samples were measured and the correlation between the parameters and the concentrations of PEs were determined using standard methods. The values obtained were used to calculate bio-concentration factor (BCF), biota sediment accumulation factor (BSAF) and phthalate pollution index (PPI) in the samples. BBP was not detected in all samples. The total phthalate level in different stations ranged between 0.82µg/L and 1.76µg/L, 1.39mg/kg and 3.28 mg/kg, and 0.18mg/kg and 0.68mg/kg in water, sediment and M. vollenhovenii respectively. It was found that Station 2 had the highest total phthalates concentrations in water and sediment samples while Station 3 had the highest total phthalates in M. vollenhovenii. The concentrations of individual phthalates from highest to lowest followed the pattern DBP > DEP > DEHP > DMP > DnOP in water samples while sediment samples followed a pattern DEP > DEHP > DBP > DMP > DnOP. There was a slight change in the pattern of individual phthalates in M. vollenhovenii because DEHP was not detected in Station 1. It followed the pattern such that DBP > DEP > DMP > DEHP > DnOP. The correlation between water parameters and the concentration of phthalates showed that there were positive and negative correlations at 0.05 significance level. Temperature and i conductivity showed a positive correlation while DO and pH showed a negative correlation with the concentrations of individual phthalates. The BCF and BSAF values which showed low concentration of DEHP in M. vollenhovenii confirmed that DEHP accumulates easily in the sediments more than DBP and DEP. BCF and BSAF values were highest in DBP, 0.45 and 0.29 respectively and lowest in DEHP, 0.08 and 0.03 respectively. The mean PPI values were significantly higher in sediment (PPI = 0.52) and lowest in M. vollenhovenii (PPI = 0.10). This study revealed that individual phthalates concentration in most stations was low compared to the total phthalate concentrations. Phthalates levels in the water, sediments and M. vollenhovenii is low but a progressive rise in the concentrations may be detrimental to aquatic organisms and human health. Conclusively, the results obtained in this study showed that high phthalate levels in the river suggests obvious implications on environmental and human health, hence the need for future pollution monitoring study in Ovia River.