DISTRIBUTION OF TRACE METALS IN ABANDONED WASTES IN SOIL POLLUTION IN EKITI STATE
The distribution of trace metals (Pb, Zn, Cd, Cr, Fe, Cu, and As) presumably present in abundance wastes that are usually emptied into the ground was monitored for 3 months precisely June to August, 2011, using Atomic Absorption spectrophotometric method. Samples collected from four sample locations within the study area were used for the study. An irregular distribution pattern of trace metals was generally observed in both sample types. Hydrodynamics and characteristics features of wetlands which some of the study area is characteristically one, also point to the fact that some extrinsic and intrinsic factors consequent upon anthropogenic inputs may have played important parts to the observed picture.
Key words: Trace metals, soil pollution, anthropogenic influences.
Environmental contamination by several trace metals has been of great concern in the last decade because these metals can constitute a hazard to man and other organisms when accumulated within the biological system (Marcus, 2008). According to Battisan (1993), the determination of their total concentration is inadequate in completely representing particular elements present in the environment. However, this knowledge is important in better understanding of trace elements, but provides no information covering the activities of elements in terms of their interaction with other components within their environment, bioavailability or resultant toxicity.
Allowary and Davies (1990) respected that trace metals have great significance due to their toxicity and accumulative behaviour. If not biodegradable, may undergo a global ecological cycle. Sediments may act as carriers and possible sources of pollution, since the mobility of these trace metals is such that they remain in the upper layer without regard to type of soil sediment. According to Scokart (1983), these metals are not permanently fixed ad can be released by changes in environmental conditions such as rainfall and the PH. The work of people (2006) and Boover (1979) revealed that nearly all metal contents in aquatic environment reside in water sediments, while the fractions in biota are small. They further indicated that sediments are the major repository of metal in some cases holding over 98% of the total amount of a metal present in the system.
Pollution is the introduction of contaminants into environment that causes instability, disorder, harm or discomfort to the ecosystem, that is, physical systems or living organisms (Gari, 2002). Pollution can take the form of chemical substances or energy, such as noise, heat or light. Pollution imposes a ride ranges of direct and indirect adverse effects on economics activity. Pollution comes from both natural and man made sources. Though globally man made pollutants from combustion, construction, mining, agriculture and warfare are increasingly significant in the air pollution equation (Spenger, 1983) some of the more common soil contaminants are chlorinated hydrocarbons (CFH), heavy metals such as chromium, cadmium, zinc, arsenic and benzene. In 2001, a series of press reports culminating in a book titled “Fateful Harvest” unveiled a widespread practice of recycling industrial by products fertilizer, resulting in the contamination of to soil with various metals.
The effects of pollution on environment are numerous, biomagnifications describes situations where toxins, such as heavy metals may pass through trophic levels. Carbon dioxide emission causes ocean acidification, the on going decrease in the PH of the earth’s ocean as C02 become dissolved. Sulphur dioxide and nitrogen oxides can cause acid rain which lowers the PH values of soil. To protect the environment from the adverse effects of pollution, many nations worldwide have enacted laws to regulate various typed of pollution as well as to mitigate the adverse effects of pollution. This paper highlights the distribution of pollutant such as trace metals-cadmium, chromium, Zinc, Fe, Pb, Cu, Arsenic and benzene present in water and soil sediment in Ekiti State.
2.0 MATERIALS AND METHODS
Analyses for the trace metals were carried out within the period of three (3) months, June to August, 2009 on samples (soil sediments) collected from four (4) sample locations. The sample locations are Okerorin and Okebedo Street at Ilawe-Ekiti in Ekiti South West Local Government Area. and Okekere and Okeosun Street at Ikere-Ekiti in Ikere Local Government Area. the samples were coded-Eksw1(TMET) Ekss2(TMET) and IKE1(TMET) IKE2 (TMET) where TMET in parenthesis represents trace metals. All the samples were collected, using grab method and parked inside separate dark 1000cm3 ploythene containers which had been thoroughly, washed, rinsed with deionised water. Samples were pretreated as prescribed by AWWA (1980) in readiness for analysis. Solutions of the samples were then taken for analysis using atomic absorption sepctrophotomer (AAS). Then the mean values of the various composite samples collected within the stated period were determined as shown in the result
Hollow Atomized Monochromator
fig1: schematic of an atomic absorption experiment
Lionization sputtering Excitation Erussion
+ + + +
– – – –
Fig 2: Schematic diagram of Atomic Absorption spectroscopes work
Source Chopper Furnace Monochromator Detector Meter
Fig 3: Spectrometer diagram of Atomic Absorption Spectrometer
Table 1: Mean concentrations of soil sediment
Samples collected between June and August 2009 in ppm
Pb / Ppm 0.4
0 1 2 3 4
Fig 4: Graph Pb concentration in EKSW1 vs station position in EKW1 station position
Zn / Ppm 0.4
0 1 2 3 4
Fig 5: Graph of Zn concentration versustation position in EKW1
Cd / Ppm 0.4
0 1 2 3 4
Fig 6: Graph of Cd concentration versus station position in EKSW 2
Cd / Ppm 0.4
0 1 2 3 4
Fig 7: Graph of Cr concentration versus station position in EKSW2
Fe / Ppm 0.8
0 1 2 3 4
Fig 8: Graph of Fe concentration versus station position in IKE1
Cu / Ppm 0.4
0 1 2 3 4
Fig 9: Graph of Cu concentration versus station position in IKE1
Zn / Ppm 3
0 1 2 3 4
Fig 10: Graph of Zn concentration versus station in position IKE2
Ars / Ppm 0.4
0 1 2 3 4
Fig 11: Graph of Ars concentration versus station position in IKE2
According to the result presented in table 1, in EKSW1, the mean concentration of Pb in soil sediment is higher in station 2 than other three stations, that is, station 1 = 0.50 ppm, station 4 = 0.62 ppm while station 3 has the least value of 0.30ppm. this indicates that there is a probable dereasing level of trace metals from the stations. The 3 may be due to the fact that during the peak of raining season, the trace metal (Pb) were below detection level. It is the mean of what was obtained at other times that is being reported. This implies that dilution effect among other factors, by rainfall at that time may have been responsible for these low values. The same reasons applicable to the lower values of mean concentrations of Zn in soil sediment in all the four stations in EKW1. in EKSW2, the mean concentrations of cadmium (cd) and chromium (Cr) in soil sediment are 0.52 and 0.65 ppm respectively in station 4 and station 2 in other stations, the values are very small which may be due to the reasons highlighted above.
Also, in both IKE1 and IKE2 had appreciable concentration of Fe and Zn in sample stations 2, 3 and 1, 2, 4 respectively while Cu and As concentrations were very low. It is of interest to mention that the presence of these trace metals evidently points to the fact that the refuse dropping grounds are actually sources of trace metals. According to Hugget et al (1976), some of these sources include among others, waste water discharge and cooling tower blow down.
The distribution of the eight trace metals presumably present in soil sediment under investigation was an irregular one, and this may have been influence by notable factors such as weather, hydrodynamics of wet lands and their characteristic physical, biological and chemical processes. The anthropogenic factor in all these is also evident. The several values obtained for all metals in sediments point to pollution tendencies
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