Dataset on assessment of pollution level of selected trace metals in farming area within the proximity of a gold mine dump, Ekuhurleni, South Africa

Food security remains an important aspect of human lives and the vital role of soil in the global agricultural and food crops production is obvious. The quality of agricultural products which is being consumed by human through the food chain is dependent on the condition of the soil. Previous gold mining activities resulted in the discharge of tailing materials containing various hazardous trace metals such as manganese (Mn), nickel (Ni), arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), chromium (Cr), lead (Pb), and zinc (Zn). 20 representative soil samples were collected from the Gold one Mine tailing dump located in Ekuhurleni, Gauteng Province, South Africa and used in describing the prevalence and concentrations of selected trace metals using inductively coupled plasma optical emission spectrometry (ICP-OES). The concentration of identified trace metals in decreasing order is as follows: Cr > Al > As > Fe > Pb > Co > Ni > Ti > Cd > Zn > Cu. Contamination levels of trace metals in the soils were evaluated using various pollution indices such as contamination factor, degree of contamination, geo-accumulation index, pollution load index and the United States Environmental Protection Agency. These evaluations revealed a high degree and the ultra-high degree of contamination classes of soils. Based on the observed concentrations of trace metals and contamination levels, this study strongly support the call for analysis of the nearby stream and drinking water quality, including the staple crops that are cultivated within the vicinity of the dump site, to ascertain the levels of heavy metals within such crops. Stringent mitigation plans or conversion of the tailing dump into value-added products should be considered.


a b s t r a c t
Food security remains an important aspect of human lives and the vital role of soil in the global agricultural and food crops production is obvious. The quality of agricultural products which is being consumed by human through the food chain is dependent on the condition of the soil. Previous gold mining activities resulted in the discharge of tailing materials containing various hazardous trace metals such as manganese (Mn), nickel (Ni), arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), chromium (Cr), lead (Pb), and zinc (Zn). 20 representative soil samples were collected from the Gold one Mine tailing dump located in Ekuhurleni, Gauteng Province, South Africa and used in describing the prevalence and concentrations of selected trace metals using inductively coupled plasma optical emission spectrometry (ICP-OES). The concentration of identified trace metals in decreasing order is as follows: Cr > Al > As > Fe > Pb > Co > Ni > Ti > Cd > Zn > Cu. Contamination levels of trace metals in the soils were evaluated using various pollution indices such as contamination factor, degree of contamination, geo-accumulation index, pollution load index and the United States Environmental Protection Agency. These evaluations revealed a high degree and the ultra-high degree of contamination classes of soils. Based on the observed concentrations of trace metals and contamination levels, this study strongly support the call for analysis of the nearby stream and drinking water quality, including the staple crops that are cultivated within the vicinity of the dump site, to ascertain the levels of heavy metals within such crops. Stringent mitigation plans or conversion of the tailing dump into value-added products should be considered. © 2019 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).

Data
Abandoned mine tailing dumps have remained a global subject of discuss in the field of mining, metallurgy and the built environment. South Africa lies on the southernmost part of the African continent, and is known to have renowned varied topography, great natural beauty, and cultural diversity. It is a medium-sized country, with a total land area of 1,219,090 square kilometres. Ekurhuleni falls within the East Rand region in the Gauteng province and is characterized by rainfall known to be Specifications Table   Subject Environmental pollution Specific subject area Soil pollution and monitoring Type of data

Value of the Data
This data presents heavy metal contaminations in soil of a farming area located within the proximity of an abandoned mine dump. Farmers, government agencies, individuals as well as academic researchers stand to benefit by understanding potential dangers to the surrounding environment and humans in general emanating from abandoned mine dump sites. The data can be used to determine the extent and impact of toxic metals on plants and animals within farming communities.
The data serves as a reference material in comparison with similar areas and for future scientific research for the planning, design and development of mitigation techniques.
typical to the Highveld summer rainfall, which occurs from October to April. The average annual rainfall varies from 715 mm to 735 mm an indication that the study area has a distinct moisture deficit. The data provided here is targeted towards monitoring of certain trace metals such as Cr, Al, As, Fe, Pb, Co, Ni, Ti, Cd, Zn, and Cu in the mining town of Blesbokspruit, Ekuhurleni, Gauteng province, South Africa. Fig. 1 shows the study area while Table 1 describes the locations of the gold mine tailing dump   Table 5. Sieve analysis and geochemical properties of soil from gold mine tailing dump are shown in Tables 6e7. Trace metal concentrations, Contamination factor (CF) and Degree of contamination, Geo-accumulation index (I geo ) and Pollution load index (PLI) of soils from gold mine tailing dump were presented in Tables 8e10.

Sampling procedure
To assess the level of trace metal contamination in the soil, about 2 kg of 20 representative soil samples were obtained from the dump site which currently serves as an informal settlement for over Table 4 Classification for the geo-accumulation index (Igeo) [10].
CF Description CF < 1 Low contamination factor 1 CF < 3 Moderate contamination factor 3 CF < 6 Considerate contamination factor CF ! 6 Very high contamination factor Table 3 Terminologies used to describe contamination degree for soil [9].
CD Description CD < 6 Low contamination degree 6 CD < 12 Moderate contamination degree 12 CD < 24 Considerate contamination degree CD ! 24 Very high contamination degree 200 individuals. Preceding the removal of top tailing samples (2 cm) using an auger cleaned with 70% ethanol, soil samples were taken at a depth of 0e20 cm for every 50 m interval. The collected soil samples (tailing) were kept cool in an icebox (<4 C) and transported to the laboratory for further analyses in sterile plastic bags, pre-treated with 70% ethanol to remove any traces of heavy metal contaminants. Using a GPS gadget, the precise location of each sample point was determined.   Table 9 Contamination factor (CF) and Degree of contamination of soil from gold mine tailing dump.

Analytical methods
Tailing samples were oven dried at 100 C for 24 hours and passed through a 2 mm sieve. Aliquots of approximately 2 g of the various tailing samples were weighed into a Teflon crucible and moistened with 100 mL of 1 M HCl acid for the determination of the HCl-soluble fraction of trace metals. The mixtures were covered and placed on a shaker for 12 hours at 130 rpm. The solutions were filtered through a Whatmann filter paper, and the filtrates were stored in sterile bottles prior to analysis of metals using inductively coupled plasma-optical emission spectrometry (ICP-OES).
The trace metals were determined using ICP-OES (Model -GBC Quantima Sequential) operated under specific conditions of 1300 W RF power, 15 L min À1 plasma flow, 2.0 L min À1 auxiliary flow, 0.8 L min À1 nebulizer flow, 1.5 mL min À1 sample uptake rate. Metal determination was done using Axial view, while 2-point background correction and 3 replicates were employed in the measurement of analytical signal. The emission intensities were determined for the most sensitive lines free of spectral interference. By diluting the stock multi-elemental standard solution (1000 mg L À1 ) in 0.5% (v/v) nitric acid, the calibration standards were prepared. The calibration curves for all the studied elements were in the range of 0.01e1.0 mg L À1 .
Physicochemical properties such as pH and EC (electrical conductivity) of the soil samples (tailing) were measured in a soil-to-water suspension (1:2.5, w/w) and a 1:5 tailings-to-water suspension using a Crison multimeter (model MM 41) respectively [1]. The grain size distribution of tailing samples was determined using the hydrometer method [2].

Soil pollution assessment
The level of trace metal pollution in an environment can be ascertained from the surrounding sediments by comparing the pollutant metal concentration with an unpolluted reference material. Thus, the average shale concentration as an International standard reference for unpolluted sediment was utilised [3]. This study applied pollution indices such as (i) metal contamination factor, (ii) contamination degree, (iii) index of geo-accumulation, and (iv) pollution load index using Eqs. (1)e(4) [4e7].
PLI ¼ ðCF 1 xCF 2 xCF 3 x…xCF n Þ 1=n (4) where Cn is the measure of the metal concentration in the examined metal n in the sediment, Bn is the background concentration of the element (average shale concentration) or reference value of the metal n, and 1.5 is the correction factor due to the lithogenic effect that could result in variations in the background values for a given metal in the environment.