Accumulation of Cadmium and Lead in Soils and Vegetables of Lenjanat Region in Isfahan Province, Iran

Overview

This short ICHMET 2012 conference paper reports total cadmium and total lead concentrations in 130 topsoil samples and 50 vegetable samples drawn from agricultural lands in the 75 km² Lenjanat region of Isfahan province, central Iran — an intensively-cultivated area surrounded by steel and cement factories and lead mining. Total metals were extracted from soils with concentrated HNO₃ and from dry-ashed plant tissue with 3 N HCl, then quantified by flame atomic absorption spectrometry (FAAS). The mean soil cadmium (Cd) concentration (1.34 mg/kg) exceeded the Swiss VBBo 0.8 mg/kg threshold and the United Kingdom 1 mg/kg maximum allowable limit cited by the authors; the mean soil lead (Pb) concentration (14.23 mg/kg) fell below the Swiss VBBo 50 mg/kg threshold. Across the 50-sample vegetable panel, 48 % of samples exceeded the FAO/WHO 0.1 mg/kg dry-weight Cd maximum permissible limit for vegetables and 75 % exceeded the corresponding 0.3 mg/kg Pb limit. The paper does not break out which vegetable species were sampled, the per-species sample sizes, or any replicate structure; species-level interpretation is therefore not possible from the published text.

Key numbers

Descriptive statistics for soil and plant samples (Table 1, p. 3; mg/kg, soils on a basis not stated, plants on a dry-weight basis per the authors’ FAO/WHO comparison):

Soil exceedance pattern (Results and discussion prose, p. 2):

• Cd in 75 % of soil samples exceeded the Swiss VBBo 0.8 mg/kg threshold (FOEFL 1998).
• Cd in 67 % of soil samples exceeded the United Kingdom 1 mg/kg maximum allowable limit cited by the authors (Kabata-Pendias & Pendias 2001).
• Cd in approximately 7 % of soil samples exceeded 2 mg/kg; Cd in more than 1 % of soil samples exceeded 3 mg/kg.
• Pb in approximately 5 % of soil samples exceeded the Swiss VBBo 50 mg/kg threshold (FOEFL 1998); the mean soil Pb (14.23 mg/kg) was well below this threshold.

Vegetable exceedance pattern (Results and discussion prose, p. 2):

• 48 % of the 50 vegetable samples exceeded the FAO/WHO Cd maximum permissible limit of 0.1 mg/kg dry weight for vegetables and fruits.
• 75 % of the 50 vegetable samples exceeded the FAO/WHO Pb maximum permissible limit of 0.3 mg/kg dry weight for vegetables and fruits.
• Vegetable Pb concentrations ranged from 0.04 to 8.15 mg/kg dry weight (Table 1).
• Vegetable Cd concentrations ranged from below the FAAS detection limit (“N.D.”) to 0.9 mg/kg dry weight (Table 1).

Variability framing (Results and discussion prose, p. 2):

• Soil Cd CV (38.81 %) interpreted by the authors as moderate variability.
• Soil Pb CV (110.75 %), vegetable Pb CV (73.88 %), and vegetable Cd CV (111.76 %) interpreted by the authors as high variability, with the highest variability in vegetable Cd.

Comparative context cited by the authors (Results and discussion prose, p. 2):

• Heavy-metal concentrations in this study reported as lower than the corresponding plant concentrations from contaminated soils of the Van region in Eastern Turkey (Turkdogan et al. 2002, as cited).
• Cd and Pb contents in agrichemical fertilisers cited as 0.0005-0.5 mg/kg and 0.0008-0.93 mg/kg respectively (Wang & Ma 2004, as cited).

Methods (brief)

Sample collection. 130 topsoil samples and 50 vegetable samples were collected randomly from agricultural lands across different soil map units within the 75 km² Lenjanat region in Isfahan province, central Iran. The study area is described as intensively-cultivated agricultural land surrounded by steel and cement-making factories and lead mining. Soils are classified as Aridisols. Average annual rainfall is 100 mm and mean annual temperature is 15.5 °C. Sampling year, sampling depth, per-species vegetable counts, vegetable identification, washing and decontamination protocols for vegetable samples, and replicate structure are not stated in the published text.

Soil sample preparation. Total Cd and total Pb were extracted from the topsoil samples using concentrated nitric acid (HNO₃), per Allen, Grimshaw & Rowland (1986).

Plant sample preparation. Vegetable samples were prepared by dry ashing. Heavy metals were extracted from the ash with 3 N hydrochloric acid (HCl). The paper does not state the ashing temperature, the ashing duration, or whether vegetable samples were washed or peeled prior to drying.

Instrumentation. Total Cd and total Pb in both matrices were determined by flame atomic absorption spectrometry (FAAS). The paper does not name the FAAS instrument vendor or model, the wavelengths used, calibration standards, certified reference materials, recovery values, method detection limits beyond the qualitative “N.D.” indicator in Table 1, or replicate-analysis precision.

Statistical analysis. Descriptive statistics (mean, variance, maximum, minimum, coefficient of variation, skewness) were computed using STATISTICA 6.0. No inferential tests, no spatial-statistics computation, and no soil-to-plant transfer-coefficient calculation are reported in the published text.

Reference values used by the authors. Soil thresholds were the Swiss Federal Office of Environment, Forest and Landscape (VBBo) values of 0.8 mg/kg Cd and 50 mg/kg Pb (FOEFL 1998), and the United Kingdom maximum allowable limit of 1 mg/kg Cd cited from Kabata-Pendias & Pendias (2001). Vegetable thresholds were the FAO/WHO maximum permissible limits of 0.1 mg/kg Cd and 0.3 mg/kg Pb for vegetables and fruits on a dry-weight basis (attribution as published).

Speciation. Total Cd and total Pb by FAAS; no speciation. No arsenic (As), mercury (Hg), chromium (Cr), nickel (Ni), or other metals reported. No inorganic arsenic (iAs)/total arsenic (tAs), methylmercury (MeHg)/total mercury (tHg), or hexavalent chromium (Cr-VI)/Cr-III distinction is applicable to this dataset.

Implications

This source contributes Iranian agricultural-land occurrence data for total Cd and total Pb in topsoils and locally-grown vegetables from a single industrial-corridor region (Lenjanat, Isfahan province) in central Iran. Principal contributions to the wiki evidence pool:

• A Cd soil signal in an Iranian agricultural area with mean soil Cd (1.34 mg/kg) exceeding both the Swiss VBBo 0.8 mg/kg threshold and the United Kingdom 1 mg/kg allowable limit cited by the authors, and 75 % of 130 topsoil samples above the Swiss threshold. This is a moderate-to-high agricultural-soil Cd burden compared to the regulatory comparators the authors cite, and the authors attribute it primarily to steel and cement industry emissions and agrichemical inputs (the paper notes the area is surrounded by lead mining as well, but the soil Cd signal exceeds the lead-only attribution).
• A vegetable Cd contamination signal under a dry-weight FAO/WHO 0.1 mg/kg reference, with 48 % of 50 vegetable samples above that ceiling and a panel-mean of 0.17 mg/kg dry weight. The paper does not stratify by vegetable species, so the species composition of the above-ceiling tail cannot be reconstructed from the published text.
• A vegetable Pb contamination signal under a dry-weight FAO/WHO 0.3 mg/kg reference, with 75 % of 50 vegetable samples above that ceiling and a panel-mean of 2.91 mg/kg dry weight — roughly 10× the cited FAO/WHO ceiling, with a maximum of 8.15 mg/kg. The soil Pb mean (14.23 mg/kg) is moderate and below the Swiss 50 mg/kg threshold, so the vegetable Pb signal cannot be accounted for by soil Pb alone in this dataset; the authors propose contributions from irrigation water, fertilisers, road-traffic dusts, and industrial deposition.
• A high-variability vegetable Cd signal (CV 111.76 %) and high-variability vegetable Pb signal (CV 73.88 %) consistent with a heterogeneous sampling pool spanning multiple unenumerated vegetable species and field locations within the 75 km² region.
• A small-panel (n = 50 vegetable samples, no species stratification, single-region, no sampling year stated), conference-proceedings-tier dataset with no certified-reference-material recovery values, no method detection limits beyond qualitative N.D., and no soil-to-plant transfer-coefficient computation. The B-tier classification reflects these limitations; the source should pool with other Iranian agricultural-soil and vegetable surveys for occurrence-distribution purposes rather than anchor any standalone characterisation.

Related evidence

• Cadmium
• Lead
• Vegetables

Update history

No substantive edit history is available in this build. The full commit record is available in git.