## 1 Introduction  
The role of heavy and trace elements in the soil system is increasingly becoming an issue of global concern at private as well as governmental levels, especially as soil constitutes a crucial component of rural and urban environments [1], and can be considered as a very important \"ecological crossroad\" in the landscape [2]. Agricultural soil contamination with heavy metals through the repeated use of untreated or poorly treated wastewater from industrial establishments and application of chemical fertilizers and pesticides is one of the most severe ecological problems in Bangladesh. Although some trace elements are essential in plant nutrition, plants growing in the close vicinity of industrial areas display increased concentration of heavy metals, serving in many cases as biomonitors of pollution loads [3]. Vegetables cultivated in soils polluted with toxic and heavy metals take up such metals and accumulate them in their edible and non-edible parts in quantities high enough to cause clinical problems both to animals and human beings consuming these metal-rich plants as there is no good mechanism for their elimination from the human body [4; 5; 6]. Toxic metals are known to have serious health implications, including carcinogenesis induced tumor promotion, and hence the growing consciousness about the health risks associated with environmental chemicals has brought a major shift in global concern towards prevention of heavy metal accumulation in soil, water and vegetables [7; 8]. Heavy metals and trace elements are also a matter of concern due to their non biodegradable nature and long biological half-lives. Wastewater from industries or other sources carries appreciable amounts of toxic heavy metals such as Cd, Cu, Zn, Cr, Ni, Pb, and Mn in surface soil which create a problem for safe rational utilization of agricultural soil [9; 10; 11; 12; 13]. Long-term use of industrial or municipal wastewater in irrigation is known to have a significant contribution to the content of trace and heavy elements such as Cd, Cu, Zn, Cr, Ni, Pb, and Mn in surface soil [12]. As a result, excessive accumulation of trace elements in agricultural soils through wastewater irrigation may not only result in soil contamination but also affect food quality and safety [14; 15; 16].  
The Dhaka Export Processing Zone (DEPZ) being the 2 nd EPZ and the largest industrial belt of Bangladesh at present houses 92 industrial units which are categorically the leading pollution creators. These industrial units include cap/accessories/garments; textile/knitting plastic goods; footwear/leather goods; metal products; electronic goods; paper products; chemicals and fertilizers and miscellaneous products [17,18]. Industrial activities discharge untreated or poorly treated industrial wastewater, effluent and even sludge into the surrounding environment that can decrease soil quality by increasing concentrations of pollutants such as heavy metals, resulting in adverse effects on macrophytes, soil fauna and human health [7,8,19,20]. So it is a nerve-racking issue to find out the present status of toxic and heavy metals in this surface soil, redress the affected subsequent environmental problems and adopt a future mitigation strategy. The present work is aimed at investigating seasonal and spatial variation of the contamination levels of different heavy metals (Fe, As, Mn, Cu, Ni, Pb, Zn, Hg, Cr, Cd) in the agricultural soil around DEPZ using different indices such as the index of geoaccumulation, contamination factor, degree of contamination, and the pollution load index. This approach would help adopt an effective effluent management strategy towards control over enhanced metal levels with recycling of effluents for toxic metal separation and soil remediation and reclamation. The data generated in this work may help to work out an effluent management strategy towards control over effective treatment of the DEPZ discharges in terms of toxic and heavy metal contents.