Md. Nahid Mahmud

Recent industrialisation around Dhaka Export Processing Zone (DEPZ) in Savar, Bangladesh has offered great economic possibilities. Nevertheless, this development has given rise to a severe risk, i.e., the pollution of farmland soils with heavy metals (HMs), which may seriously threaten the safety of food production and human health and impede sustainable farming. An extensive literature review reveals the combined effect of industrial pollution and seasonal climatic conditions upon soil quality and crop safety within this area.
My one research that has been published by Elsevier that highlights DEPZ vicinity soils are enriched with the heavy metals including arsenic (As), lead (Pb), cadmium (Cd), chromium (Cr) mercury(Hg), zinc(Zn) and copper(Cu) at higher concentrations than safety criteria. These poisonous metals are primarily the result of untreated or inadequately treated industrial waste-water and solid waste produced by factories in the zone. Heavy metals are not degradable in the environment and will accumulate in soil for long term, thereby causing additional effects on soil fertility and crop growth.
The concern with contamination is the seasonal variation in metal level, with seasonal changes causing variation in metal levels. During dry periods, there is lower rainfall and therefore there is less leaching or movement of the contaminant through the soil. This means that during the dry periods, higher amounts of heavy metals will accumulate in the topsoil than during the wet periods. In contrast, heavy rainfall during the monsoon period will move some of the metals from surface to deeper depths in the soil or wash them into surface waters, thereby temporarily reducing the surface concentration of metals. However, this process of rainfall-produced leaching does not remove the metals from the surface of the soil or remove them from the environment; rainfall merely redistributes contaminants within the soil profile, and may also provide vectors for the spread of contaminants to other locations through runoff water.
The Geo-Accumulation Index (Igeo), the Contamination Factor (CF), and the Pollution Load Index (PLI) are examples of indices which measure how polluted a specific area is. Research has shown soils in the vicinity of DEPZ to fall into classifications of moderate to extreme contamination, based on Igeo, CF and PLI scores, for both arsenic and mercury during all seasons. In addition, these results indicate how serious the pollution issue is as well as providing evidence of an ongoing ecological risk at all times.
Heavy Metals in Soil have a well-established pattern of entering the Food Chain through crops that are grown in contaminated areas. The Presence of Toxic Metals in the soil surrounding the DEPZ would result in the absorption of these metals by Vegetables and Rice, causing them to accumulate in the edible portions of the Vegetable or Rice that are consumed by Humans. As a result of the regular consumption of contaminated food, Humans may be exposed to serious health problems resulting from exposure to Toxic Metals, including Damage to the Kidneys, Neurological Disorders, Developmental Problems, Cancer, etc. particularly for Examples of Cadmium and Arsenic, which are known to be highly Toxic to humans and have no safe level of exposure.
From a regulatory standpoint, the review indicates that Bangladesh is in need of improved governance and enforcement structures to better manage the release of industrial waste into the environment. This requires the establishment of a zero-discharge ETP for all wastewater produced by industry, as well as regular monitoring of both soil and crops, as well as the implementation of sustainable waste disposal practices by industry. If steps are not taken immediately, heavy metals will continue to cause environmental harm to agriculture and health to many agricultural communities in Bangladesh.
Furthermore, the study highlights some potential remediation and mitigation techniques that would reduce levels of metals in soil, including phytoremediation (plant-assisted absorption of contaminants from the soil) and bioremediation (microbe-assisted detoxification of the soil). Both options provide a sustainable, non-chemical or non-physical clean-up alternative. However, these techniques will need to complement the existing regulatory initiatives and require long-term monitoring in conjunction with active engagement of the local community by all parties involved.
Eventually , agricultural soil contamination in the vicinity of the DEPZ presents not only an environmental problem, but a potential public health and food security crisis. Seasonal variability may alter the patterns of contaminant distribution, however, the underlying issue will continue throughout the year. Policymakers, farmers and industry stakeholders, along with civil society, need to work together to mitigate future heavy metal contamination to protect the agricultural land that supports millions of people.

The writer  is a researcher and Agricultural Sciences learner at IUBAT- International University of Business Agriculture and Technology , Dhaka 1230, Bangladesh.He can be reached at  nahidmahmudiubat@gmail.com