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Heavy Metal Content in Different Vegetables Grown in Industrially Polluted and Non-polluted Areas (2015-2016)

H. M. NASER
Soil Science Division, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur, Bangladesh

S. SULTANA
Soil Science Division, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur, Bangladesh

S. AKHTER
Soil Science Division, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur, Bangladesh

R. A. BEGUM
Soil Science Division, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur, Bangladesh

Abstract/ Executive Summary:

The content of four toxic heavy metals, lead (Pb), cadmium (Cd), nickel (Ni), and chromium (Cr) in three popular leafy vegetables namely kankon ((Ipomoea reptants) indian spinach (Basella alba L., B. rubra L), and taro (Colocasia esculenta) and in the rhizosphere soils of the respective crops from two locations viz, waste water-irrigated and clean water-irrigated areas were assessed using atomic absorption spectrophotometer. Regardless of locations, there were significant differences (P <0.05) in the average Pb, Cd, Ni, and Cr concentrations in different vegetable species and the soils in which they were grown. The accumulation of metal in the plants was two to three folds higher at the waste water-irrigated site compared to concentrations were recorded at clean water-irrigated site. The mean value of metals content in the roots and shoots ranged from 0.40 to 0.89, 0.35 to 0.66, 16.0 to 43.4, and 21.7 to 61.4 µg g^-1, respectively in Pb, Cd, Ni and Cr in the waste water-irrigated site and it was 0.24 to 0.0.34, 0.25 to 0.30, 5.23 to 17.4, and 12.3 to 28.8 µg g^-1 for the clean water-irrigated site. Results of the study show that among the three spices, the maximum concentration of Pb and Cd was found in kankon whereas Ni and Cr concentration was in Indian spinach and taro, respectively. The concentrations of metal in plants followed the rules that Cr > Ni > Pb > Cd. In soil and in the plants, the concentration of Pb and Ni not exceeding the maximum permissible limit of 5 and 20 µg g^-1, respectively for food and foodstuff provided by FAO/WHO at both the sites. But Cd and Cr exceeding the maximum permissible limit. Therefore, the soil is said to be alarming to contaminate by anthropogenic inputs and requires continuous monitoring of this area.

Keywords: Heavy metal, Soil fertility, Vegetables, Pollution,

Location: Kalakoir, Konabari, Gazipur district, Bangladesh

Start Date: 00-00-2015

End Date: 00-00-2016

Program Area: Crop-Soil-Water Management

Commodity: Vegetables, Contamination of soil, Heavy metal

Objectives:

(i) To investigate the concentration of heavy metals (Pb, Cd, Ni, and Cr) in commonly grown vegetables and (ii) to examine the heavy metal status of soils under varying levels of pollution.

Methodology:

Plant materials and soils: Three species of plants namely kankon (Ipomoea reptants) indian spinach (Basella alba L., B. rubra L), and taro (Colocasia esculenta) and the rizosphere soils of the respective spices were collected from farmers’ field of Kalakoir, Konabari, Gazipur. The samples in this area were taken from the side irrigated with the Turag river water regarded as waste water-irrigated site (polluted area). The river Turag is highly polluted by industrial effluents, sewage sludge, municipal waste water and urban pollution. And the same vegetable samples were collected from Bangladesh Agricultural Research Institute, Gazipur, regarded as clean water-irrigated site (non-polluted area). Samples collected from different plots in each area were treated as replicates.

Preparation and preservation: Plant samples were collected carefully without any disturbance to the root system. Samples were placed in polyethylene bags and brought to the laboratory for analysis. All samples were washed with tap water followed with DDI (double de-ionized distilled water) after keeping them on a 2.5-mm-mesh sieve to remove the soil particles adhering to the roots. The samples were separated into root, shoot parts and were air-dried and placed in an electric oven at 65°C for 72–96 h depending on the sample size. Soil samples from rhizosphere of respective plants (0–15 cm) were collected with a stainless steel auger from the same locations simultaneously. The distance from one sampling point to another was approximately 100 m. About 300–400 g of the soil was sampled and transferred to polyethylene bags. Collected soil samples were air-dried for several days over Pyrex petry dishes. After drying, the samples both plant and soils were ground into powder form used mrtal analysis.

Digestion and determination: The samples were digested with HNO₃ and HClO₄ (5:1 volume) for total metal estimation as described by Misra and Chaturvedi (2007)]. One gram of each sample was weighed into 50-ml beaker, followed by the addition of 10 ml mixture of analytical grade acids HNO₃: HCIO₄ in the ratio 5:1, and left overnight for complete contact of material. Next day, the digestion was performed at a temperature of about 190ºC for 1.5 h. After cooling, the samples were transferred into 50 ml volumetric flask and the solution was made up to a final volume raised up to the mark with distilled water. The metal concentrations were determined by atomic absorption spectrometry using a VARIAN model AA2407 Atomic Absorption Spectrophotometer (AAS). Analysis of each sample was carried out three times to obtain representative results and the data reported in µg g^-1 (on a dry matter basis). Statistical differences were judged by Tukey’s multiple comparisons test by using Excel Statistics version 4.0 (Esumi Co. Ltd., Tokyo, Japan).

Pollution Index

The pollution index (PI) was calculated by the following formula (Rai et al., 2011): PI = Ci/Si

Ci: Heavy metal content in a soil sample (µg kg^-1);

Si: Permitted standard of the same metal (µg kg^-1).

Source of Information: Annual Research Report 2015-2016, Soil Science Division, Bangladesh Agricultural Research Institute, Joydebpur, Gazipur, Bangladesh

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Industrial effluents and urban pollution associated with sewage sludge, municipal wastewater increased the levels of Pb, Cd, Ni, and Cr intake of the vegetables and soils. All these metals have toxic potential effects, but the detrimental impact would become apparent after decades of exposure. Monitoring of heavy metals in plant tissues is essential in order to prevent excessive build-up of these metals in the human food chain. To avoid the entrance of metals into the food chain, industrial discharges should not be drained into rivers and farmlands without prior treatment. Considering human health hazards, it is recommended that these types of plants should not be cultivated in farms and fields irrigated by industrial wastewater or water contaminated by heavy metals. These findings suggest further work by more controlled experiments, which should take into consideration of variations in uptake between different plant species, cropping history, fertilization and the levels of metals present in the soils and atmosphere.

Knowledge Management: Report/Proceedings