Heavy Metals Status in Soils of Ballari District using Atomic Absorption Spectroscopy (AAS)


B. M.Rajeshwari1, PatilS. J.2*

1Department of Physics, Vijayanagara Sri Krishnadevaraya University, Jnana Sagara Campus, Ballari-583105, Karnataka, India

2Department of Life Sciences, School of Science, Garden City University, Bengaluru-560049, Karnataka, India

*Corresponding Author E-mail: shajapatil@gmail.com; sjpatil@gardencitycollege.edu



Current study reveals that, heavy metals statusof agriculture soils of Sandurtalluk, Ballari district, Karnataka, India. Composite soil samples were collected about 100 m2 apart at 0-30 cm (top soil) and 50-60 cm (subsoil) depths from study area during the dry season in January, 2016. The soils were analyzed for pH and total concentration of heavy metals such as Cd, Cr, Cu, Fe, Mn, & Zn by using Atomic Absorption Spectrometer (AAS) Technique. Results show that total mean concentrations of the heavy metals decreased with depth. Whereas, the mean concentrations of the metals in the top and sub soil of Sandur mine increased respectively in the order, Fe > Zn > Cu > Mn > Cd > Cr.


KEYWORDS:Soils, heavy metals, AAS, physicochemical, metals.




Heavy metals are among one of the major pollutants of natural resources, which pose severe threats to the biodiversity with the development of mining, smelting and industries due to manmade accelerated activities. Heavy metal pollution not only affects the productivity of crops, reduce the quality of different water bodies,atmosphereand life of animals and human beings by the way of food chain and it also threatens the entire biodiversity. The pollution caused by heavy metals is long term and irreversible process. The metal species commonly found in the environment as a result of human activities includes, Copper, Zinc, Nickel, Lead, Cadmium, Cobalt, Mercury, Chromium and Arsenic. Some of these metals act as micronutrients at small concentrationsin living organisms for their normal physiological activities, but accumulation in higher concentration becomes toxic to most of the life forms[1, 2].


The soil texture supports the base for almost all natural and manmade activities and as a result it is one of the repositories for anthropogenic wastes. Increasing industrialization has been accompanied throughout the world by the extraction and distribution of mineral substances from their natural deposits [3]. The by products and tailings resulting from such activities usually deposit or leach into the soil. Metals occur in different forms in their ores and their relative abundance in a given location may be exacerbated depending on the soil physciochemical property. Additional inputs from agricultural, mining and quarry activities, emissions from air fallouts, weathering of the parent rocks as well as transportation of accumulated pollutants into soil and water also increase metal load in an environment. Heavy metal load in soil is greatly influenced by metalliferous mining/smelting activities, burning of fossil fuel, waste disposal and industrialization [4].


Heavy metal pollution is not only toxic to plants and it also deteriorates soil optimal bio-productivity, but it is a severe threat to human health especially at elevated level. Some of them as Lead, Mercury, Arsenicare known carcinogens and causes a long term damaging effect on the central nervous system [5]. They are non-biodegradable and they have the tendency to bioaccumulate and biomagnify from one trophic level to another [6]. Plants growing in polluted environment are likely to accumulate toxic metals more than others grown outside such an environment. Studies have shown that vegetables grown in metal contaminated soils accumulate heavy metals at higher level than the uncontaminated soils [7-9]. The heavy metal load in soil and plants from the derelict Enyigba Mine and its environs have been reported [10] and their prevalence in ground and surface water supplies in Ebonyi State have also been assayed [11].Heavy metal contamination of soil may pose risks and hazards to humans and the ecosystem through: direct ingestion or contact with contaminated soil, the food chain (soil-plant-human or soil-plant-animal-human), drinking of contaminated ground water, reduction in food quality (safety and marketability) via phytotoxicity, reduction in land usability for agricultural production causing food insecurity, and land tenure problems [12, 13].


This current study examines the levels of cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) as well as the pH of soils in the anthropogenically activemined areas of Sandurtalluk, Ballari district, Karnataka. The objective was to obtain current data on the metal load using AAS rather than PIXE used by previous researchers and to make comparison on their distribution between the areas. The major disadvantage of AAS is that its application is limited to samples in solution phase and it cannot give a reliable result in contaminated samples due to its high sensitivity. Besides analytes such as Hg and As are present at very low concentrations (nanometer levels) cannot be determined by simple AAS but with ICP-AES [14].



2.1 The study area:

The present study provides a details of Sandurtalluk is located in the central part of Ballari district and eastern part of Karnataka state. It lies between 15°00' and 15°15' N latitude and 76°20' and 76°55' E longitude. The total geographical area is 1,243,95 Sq.kms.The study area is covered by Archean granite and peninsular gneiss. The study area is known for its rich in iron and manganese ore reserves. The minerals are being exploited on a large scale since 1907. The entire region is hilly with varying elevation from 700 to 1100 meters.


2.2 Types of soil:

Soil is a term that has an extremely wide definition and indicates to a loose layer of earth that covers the surface of the planet. Soil is produced when rocks divided into their constituent parts. Because of the quantity of distinctive types of natural and mineral organizations, there are different varieties of soil that experiences different ecological pressures. Basically there are three types of soil, they are clay soil, sandy soil and silty soil.


2.3 Statement of work:

Due to rapid industrialization and urbanization streams flowing along the villages and cities are being contaminated due to discharge of untreated effluents and unscientific practice. Thesurrounding agricultural lands along with the stretch utilizes these lands to cultivate their crops leads to cause heavy metal contamination in soil as well as crops. The absence ofadministration of solid waste management may prompt the soil, water and air contamination because of bioaccumulation, additionally agriculturalists are utilizing this natural resources for agriculture practice, which may have adverse effect on soil quality and physicochemical parameters.



Figure 1 Map showing the sampling area of Sandurtalluk, Ballaridistrict, Karnataka


2.4 Digestion process:

Soil samples of 3 different (three replicates) were collected at surface level (0–30 cm in depth)were collected from various locations to cover different soil of agricultural areas. The collected soil samples were air-dried and sieved into coarse and fine fractions. Well-mixed samples of 2 g each were taken in 250 mL glass beakers and digested with 8 mL of aqua regia on a sand bath for 2 hours [15]. After evaporation to near dryness, the samples were dissolved with 10 mL of 2% nitric acid, filtered and then diluted to 50 mL with distilled water.


2.5 Sample analysis and Atomic Absorption Spectroscopy (AAS) measurement:

The standard working solutions of elements of interest were prepared to make the standard calibration curve. Absorption for a sample solution uses the calibration curves to determine the concentration of particular element in that sample. AVarian AA240FS Atomic Absorption Spectroscopy (AAS) was used for the determination of 6 metals that is, Cd, Cr, Cu, Fe, Mn and Zn. Cathode lamps were used for radiation source. Air acetylene gas was used for all the experiments. This method provides both sensitivity and selectivity since other elements in the sample will not generally absorb the chosen wavelength and thus, will not interfere with the measurement.



The results of the total meanheavy metal concentrations in different places of soil samples are presented in table 1 and range and threshold concentrations of heavy metals for various sourcesshown in table 2. Figure2 represent the distributions of cadmium, chromium, copper, iron, manganese and zinc respectively in the top and sub soil of Sandurtalluk, Ballari district of Karnataka. The plant assimilates essential micronutrients as well as heavy metals from the soil for healthy growth, flowering, fruiting etc. The very low concentration as well as very high concentration shows deficiency and toxicity to the agriculture crops.


Table 1:Range and threshold concentrations of heavy metals for various sources


Range of heavy metals in soils (ppm)

Agricultural soils (ppm) threshold values

Drinking water (ppm) (WHO)

Irrigation water (ppm) (FAO)































Sources [16]


Table 2: Concentration of heavy metals in soil samples of Sandurtalluk, Ballari district (in ppm: n=3)









Sample 1








Sample 2








Sample 3


















Figure2:Concentration of elements in soil samples of Sandurtalluk, Ballari district (in ppm: n=3)


Soil reactivity is expressed in terms of pH and is a measure of the acidity or alkalinity of the soil. More precisely, it is a measure of hydrogen ion concentration in an aqueous solution and ranges in values from 0 to 14 (acidic to basic) but practically speaking for soils in study area shown that mean percentage 7.27, pH ranges from 3.5 to 9.5, as pH values beyond those extremes are toxic to life forms.


Agricultural soils normally contain low background levels of heavy metals. Contamination from industrial activities or byproducts can increase the natural levels of heavy metals in soil, creating a health hazard to people, livestock and plants. Fertilizers and other soil amendments also add small amounts of heavy metals to the soil, which can build up over time with repeated applications.


The actual toxicity of a heavy metal will be affected by soil texture, organic matter, and pH. The health effects of exposure to heavy metals depend on the amount and duration of exposure, i.e. the volume of contaminated soil or food consumed over time [17].


It is not clear exactly what levels of heavy metals in soil are safe or unsafe, so the following information is provided only to help you understand your test results and the relative level of risk they represent. In soils with elevated heavy metal levels, which may pose higher levels of risk, you should consider whether remedial actions are appropriate, or whether crops should be grown at all.


The concentration of heavy metals (Cd, Cr, Cu, Fe, Mn and Zn) in soils varied from 0.0057 to 9.05ppmand the values for majority of metals were within the critical limit of soils when compared to standard range as mentioned by the WHO and FAO for agriculture and consumption purpose (Table 1 & 2). The mean concentration of Cd was very low (0.0057ppm) compared to other heavy metals and ranged from to for standardscompared 0.001-100.00ppm. The mean concentration of Cr is (2.435ppm) standard rangebetween1-1,000ppm, Cumean concentration is (1.036ppm) standard range between 2-100ppm,Femean concentration is (63.37ppm) and standard range between 6-9ppm, Mnmean concentration is (9.053ppm) and standard rangebetween 20-3.000ppm and mean concentration of Zn is (2.90ppm) and standard range between 10-300ppm in the soil samples. Krishna and Govil[18] also reported higher concentrations of Cu (137.7 mg/kg) and Ni (139 mg/kg) in the soil samples collected from Surat, Western India, but these soils were adjacent to industrial areas. From our study, it is evident that soil samples collected from the all the sites under rainfed production systems of selected area vary widely in heavy metal concentrations. The contamination of agricultural soils and crops by heavy metals is of concern due to their potential effects on human health and the sustainability of food production systems in contaminated areas [19]. The presence of heavy metals is of special concern because they are highly persistent and pose potential danger to human and animal health. Ingestion of vegetables grown in soils contaminated with heavy metals poses a possible risk to human health [20]. The main route of exposure to these toxic heavy metals is through food [21]. Agriculture in rainfed areas is uncertain because of its full dependence on rain, and generally, the soils are degraded and low in fertility. Alfisols, Vertisols, Aridisols and Inceptisols are major soil orders, which occur predominantly in rainfed regions of India [22]. Soil pollution in agricultural areas surrounding big cities is a major environmental problem [23].


The levels of heavy metals in terms of iron (Fe) and manganese (Mn) as well as fluoride (F) depending upon the type offormation of iron ore is contributing to the variable values of these parameters.


An analysis of socio-economic impacts shows that there has been adverse impact of mining on agriculture, horticulture and health parameters in the mine affected areas-


a.     There has been increase in fallow land in the district from 2003-04 to 2008-09 mainly due to low productivity of agricultural and tree crops and diversion of agricultural land for mining related activities.

b.    There has been sharp increase in mining related diseases in the area. Acute diarrhoea and respiratory diseases contribute 42% of the total health related problems in the three mining talluks (Ballari, Hospet andSandur).

c.     There has been increase in the numbers of road accidents resulting from poor road conditions and increased density of vehicles on roads[24].



Monitoring of micronutrients in the soil provides efficient way to assess the qualitative and quantitative differences in metal concentrations at distinct locations. It can be concluded that the physicochemical analysis of soil samples under study showed variable concentrations of various parameters. Irregular distributions of micronutrients were recorded during the present investigation, which may be attributed to the added fertilizers during the crop formation.



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Received on 05.05.2018         Modified on 20.06.2018

Accepted on 10.07.2018         © AJRC All right reserved

Asian J. Research Chem. 2018; 11(4):701-704.