Investigation of heavy metals contaminant in downstream landfilling site of Ardebil municipal waste

Introduction
Landfilling sites of wastes including big volume of waste. In recent years lack correct management caused that landfilling sites of municipal waste taken as one of main source pollution effluence at environmental. From between diverse contaminants heavy metals because of environmental stability, biogeochemical process, poison biology, sorption and desorption, redox potential, sedimentation, dissolve, ciliate and hazardous of habitat are more important. Heavy metals prevalent in leachate are include As, Cd, Cr, Co, Cu, Pb, Hg, Ni and Zn. The traditional method of landfills was to directly stack wastes in valley and watercources that are naturally formed or in artificial pits and pounds without any treatment to prevent wastes from diffusion and transference is caused during filling, the wastes will release leachate of high concentration due to self-zymosis and rain fall washing as well as dipping in both surface and ground water, which will flow slowly with groundwater, polluting its surroundings for decades, even hundreds of years. The problem and major environmental concerns associated with the dispersal or disposal of industrial and urban wastes generated by human activities is the contamination of the soil. Groundwater pollution from landfills can depend on several factors, such as hydraulic conductivity of the strata underneath the landfill site, depth of vadose zone, type of soil in vadose zone, hydraulic gradient of aquifer and the type of landfill. Faults and gaps of rock bed can course for leachate infiltration in groundwater. Main purpose from this study, investigative contaminant heavy metal derived from waste landfilling on soils and waters downstream landfilling site of Ardebil municipal waste.

Materials and method
Ardebil municipality is a city located in the northwest Iran in central part of Ardebil province in zone west Alburz – Azarbaijan. The landfilling site of Ardebil municipal waste located between 48° 13´ 40″ longitudinal east and 38° 26´ 33″ latitudinal north. Landfilling site of Ardebil municipal waste with an area of about 50 hectare and at an altitude of 1575 m above the sea level is located in distance 22km west north of Ardebil city. Daily 300 ton municipal waste is disposing in this site with traditional method and without any preservative. The location of the study area is shown in the Figure. 1.


Figure. 1 Location of the study area

The annual average amount of precipitation and evaporation are determined 320-810 mm, respectively. The area is determined to have a semiarid climate. Open dump areas located in the unit Eocene Trachyandesite. Depth soil is very shallow with outstanding rock without cover of soil and texture soil is sandy. Groundwater levels in the surrounding landfilling site are 30-60 m.
In preliminary area is investigated from aspect topographically, surface and groundwater position, soil texture, soil depth and genus of rock bed. In order to investigate concentration some heavy metals in downstream soils landfilling site of Ardebil municipal waste, 1 sample control was taken from distance 400m upstream from landfilling site and 11 sample were taken from distances 50 to 1300m from landfilling site in downstream. To avoid from influence various arbitrary surface conditions, the selected depth of sampling is from 10 cm to 20 cm below the surface. After determine soil texture and PH in the laboratory elements of Cu, Fe, Mn, Co, Ni, Cd, Zn and Pb were measured using atomic absorption spectrophotometer (AAS). To assess soil samples pollution the metals concentration in the soil samples compared with the reference values recommended by United State Environmental Protection Agency and enrichment factor and geoaccumulation index calculated for all samples. Based on enrichment factor can estimate elements concentration relative to their natural concentrations. This factor calculating from under formula:

EF = Sc/ Rc

Where EF is the enrichment factor, Sc concentration of element in soil and Rc is concentration of element in reference material. Bhuiyana et al (2010) divided contamination into different categories based on EF values. These categories shown in Table 1.



Table 1: classification of enrichment factor values













Geoaccumulation index (Igeo) introduced by Muller (1969) and calculating from under formula:

Igeo= log2 [(Cn) / (1.5Bn)]

Where Cn is the measured concentration of the element n and Bn is the geochemical background value element n in average crust. Muller divided geoaccumulation index values into classes four (Table 2).


Table 2: classification of geoaccumulation factor values











Because of devoid of perpetual surface waters sampling didn't from surface water. To sampling from ground waters source 1 sample control were taken from upward landfilling site and 4 samples from downward in dry and wet season. Then measuring general parameters (EC, PH, COD, BOD, and TDS) and heavy metals (Cu, Fe, Mn, Co, Ni, Cd, Zn and Pb) of water was done in laboratory.

Results and discussion
In the all samples sand particle was very high and soil texture is sandy. The PH values in the samples ranged from 6.84 to 8.11 and The EC values in the samples ranged from 9818 to 17532. Result comparing element concentration of soil samples with the reference values recommended by United State Environmental Protection Agency show that Cu in 1 and 2 samples is above the standard limits. Fe and Mn in 1 sample are above the standard limits. Co in 1 and 7 samples is above the standard limits. Pb, Zn and Cd in all samples are above the standard limits. Results calculating enrichment factor and geoaccumulation index show that Pb, Cd and Zn have the most enrichment and accumulation.
Soils downstream shows high contamination from Cd, Zn and Pb elements. Considering these elements in control sample is higher from United State Environmental Protection Agency standard but these elements concentration in control sample is lower relative to downstream samples so these metals derived from anthropogenic and lithologic of sources. Lithologic source the elements derived from igneous rocks collection of inner and volcanic in the area. Anthropogenic source the elements derived from colored plastic, battery, medicine apparatus, electronic apparatus and toiletries of wastes. Because of soils are sandy richment heavy metal is lower.
Result comparing water samples analysis with the reference values recommended by World Health Organization show that EC and TDS in downward samples are above the standard limits. PH, BOD, COD, Fe and Cu in the all samples are low the standard limits. Zn and Pb in the all samples are above the standard limits. Co, Ni and Cd were not detected in none from samples. In none from water samples exist not meaningful difference between elements concentration in control sample with downward samples that indictor pollution derived from leacate. High concentrations Zn and Pb elements derived from condition of lithology and geology area.

Conclusion
Considering results analysis samples of soil and water deduced that soils of downstream was polluted from Pb, Zn and Cd elements and agricultural lands downstream was polluted. Considering in landfilling site slope is very high and soil very sandy, leacate can effluence in vast surface and was caused area soil pollution. Results analysis of water samples didn't explain pollution in 5 water samples was collected. Considering Ardebil landfilling site located in elevation and wells sampled located in distance more from landfilling site leacate cannot pollute those. Locating the site on rock layer of very fragile and without soil cover will cause serious hazardous. For more study:
1-Determining leacate pollution index (LPI)
2- Air analysis for determining air contaminants
3- Chemical analysis farm product for determining cancinogen metals concentration
4- Diging pizometers in appropriate sites for monitoring of groundwaters pollution
5- Determining origin of lithologic Zn and Pb elements.
Keywords: Ardebil, landfilling site, heavy metal, soil pollution, water pollution