_Appl. Sci._**2012**, \(2\), 584-601; doi:10.3390/app2030584  
_applied sciences_  
**ISSN 2076-3417**  
www.mdpi.com/journal/applsci  
Assessment of Heavy Metal Contamination of Agricultural Soil around Dhaka Export Processing Zone (DEPZ), Bangladesh: Implication of Seasonal Variation and Indices  
**[PERSON] 1,*, [PERSON] 1, [PERSON] 1, [PERSON] 2, [PERSON] 2 and [PERSON] 2**  
1 Department of Environmental Sciences, Jahangirnagar University, Dhaka 1342, Bangladesh; E-Mails: [EMAIL_ADDRESS] (D.K.); [EMAIL_ADDRESS] (T.M.A.)  
2 Analytical Research Division, Bangladesh Council of Scientific and Industrial Research (BCSIR) Laboratories, Dhaka 1205, Bangladesh; E-Mails: [EMAIL_ADDRESS] (M.S.I.); [EMAIL_ADDRESS] (M.A.A.); [EMAIL_ADDRESS] (M.A.A.)  
* Author to whom correspondence should be addressed; E-Mail: [EMAIL_ADDRESS] (S.H.R.); Tel.: +88-02-779-1045 to 51 (ext. 1370); Fax: +88-02-779-1052.  
_Received: 20 April 2012; in revised form: 11 June 2012 / Accepted: 12 June 2012 / Published: 2 July 2012_  
**Abstract:** Intense urbanization, large scale industrialization and unprecedented population growth in the last few decades have been responsible for lowering environmental quality. Soil contamination with metals is a serious concern due to their toxicity and ability to accumulate in the biota. The present work assessed the heavy metal contamination of agricultural soil in the close vicinity of the Dhaka Export Processing Zone (DEPZ) in both dry and wet seasons using different indices _viz._, index of geoaccumulation (I\({}_{\text{geo}}\)), contamination factor (C\({}_{\text{f}}^{\text{I}}\)), degree of contamination (C\({}_{\text{d}}\) ), modified degree of contamination (\(mC_{d}\)) and pollution load index (PLI). Samples were collected from the surface layer of soil and analyzed by Atomic Absorption Spectrophotometer (AAS). The trend of metals according to average concentration during the dry and wet seasons was As \(>\) Fe \(>\) Hg \(>\) Mn \(>\) Zn \(>\) Cu \(>\) Cr \(>\) Ni \(>\) Pb \(>\) Cd and As \(>\) Fe \(>\) Mn \(>\) Zn \(>\) Hg \(>\) Cu \(>\) Ni \(>\) Cr \(>\) Pb \(>\) Cd, respectively. Because of seasonal rainfall, dilution and other run-off during the wet season, metals from the upper layer of soil were flushed out to some extent and hence all the indices values were lower in this season compared to that of the dry season. I\({}_{\text{geo}}\) results revealed that the study area was strongly and moderately contaminated with As and Hg in the dry and wet seasons respectively. According to C\({}_{\text{f}}^{\text{I}}\), soil was classified as moderately contaminated with Zn, Cr, Pb and Ni, considerably contaminated with Cu and highly contaminated with As and Hg. The general trend of the mean \(\mathrm{C_{f}^{1}}\) was \(\mathrm{Hg>As>Cu>Zn>Ni>Cr>Pb>Fe>Mn>Cd}\) and \(\mathrm{As>Hg>Cu>Cd>Zn>Ni>Pb>Fe>Mn}\) in dry and wet seasons, respectively. The \(m\mathrm{C_{f}}\) values in the dry and wet seasons were 575.13 and 244.44 respectively indicating an ultra high degree of contamination. The \(\mathrm{C_{d}}\) values in both seasons were associated with a very high degree of contamination. PLI results indicated immediate intervention to ameliorate pollution in both seasons. The main sources of metals included effluents from wastewater treatment plants, treated and untreated wastewater from surrounding industrial establishments as well as agricultural activities. Protecting the agricultural soil is a formidable challenge in the study area, which requires modernization of industries, thereby improving the recovery and recycling of wastewater. Indices analysis presented in the present work could serve as a landmark for contemporary research in toxicology.  
index of geoaccumulation; contamination factor; degree of contamination; pollution load index; heavy metal; zero discharge system ETP; bioaccumulation; Bangladesh