Unabated pollution: People at riskAs populations in the world continue to grow and pressures on environment from land-based and marine human activities increase, land, atmosphere, river, coastal and marine living resources and their habitats are being lost or damaged in ways that are also affecting human lives on earth. There have been severe pollutions already recorded to date by the industrially developed countries. But environmental issues can never be local or regional, must be global.
For the present, let us have a look at how the pollution process is being taken place in the aquatic ecosystem.
Phytoplankton: Phytoplankton is considered as the heart of water bodies (primary energy and food source). Planktonic algae are waterborne single-cell algae. Planktonic algae (algae bloom) usually occurs as a result of increased levels of nutrients and carbon dioxide in water, combined with the energy of sunlight.
Effect of increased nutrient level in surface water
A. Surface water environment (Pelagic ecosystem):
Because of their tiny sizes, total oxygen production and carbon dioxide uptake are often thought half of the global plant production and uptake respectively. Nutrient loads (nitrogen, phosphorous and silica) from various sources (land fertilizer usage for rice and other food grains, often urea mixed water directly from different fertiliser companies, raw chemicals directly from garment industries, leather industries, hospitals etc.) are being daily loaded. These increased nutrient loads taken up as dissolved form of nitrogen, phosphorous and silica (nitrate-nitrogen, ammonia-nitrogen, phosphate-phosphorous and silicon dioxide) by phytoplankton cause phytoplankton bloom. Water colour gets changed (red tide) with noxious smell and water body becomes toxic. Excess growth of such phytoplankton help create phytoplanktonic species shift (diatom -- primary food source of fishes, zooplankton, shrimps and other animals shift to dinoflagettes) that severely affects in aquatic ecosystem's food chain, lowers the dissolved oxygen, increases dissolved carbon dioxide. Massive surface water environmental pollution taken place by such increased nutrient levels especially by nitrogen, phosphorous and silica has been an important issue for global warming and public health.
B. Bottom water environment (Benthic ecosystem):
Excess growth of surface water phytoplankton owing to increased nutrients is being sunk to the surface of sediment as particulate organic matter in the benthic ecosystem. This accumulated organic matter is being released to the water column as inorganic nutrients (nitrate-nitrogen, ammonia-nitrogen, phosphate-phosphorous and silicon dioxide) available again for phytoplankton growth after bacterial decomposition. Therefore sediment and water column bacteria take up sufficient oxygen for the degradation of the produced organic matter that in turn cause benthic animals suffer from oxygen. In Bangladesh, the recently measured surface water oxygen content in different rivers is about 3-5 mg L-1 (minimum level must be 5 mg L-1 for the existence of life in water body). Besides, sedimentation rate each year in Bangladesh is very high. Such hazardous condition cause death of benthic animals (fishes, mollusks, bivalves, polychaetes, shrimps etc.).
Interestingly, some attached phytoplankton (morphology and physiology is different from surface water phytoplankton) inhabiting on the few millimeter surface sediment provide not only important food source for benthic animals but also produce oxygen. Attached phytoplankton algal management has lately been initiated by the first world countries. Therefore, it is still a long way for Bangladesh.
Effect of heavy metals
The Hazaribagh tannery complex and other industries, primarily the glue and paint industries in the same general location, have affected water and air quality in a large poorly drained area locked behind a nine meters high flood control embankment constructed in 1989-1990 in south-west Dhaka City. Up until the time of embankment construction, the contaminants were washed to the Buriganga river by annual flooding. At present, the existing sewage outfalls, the sewage lift operations consisting of 16 pumps and local residential drains are not adequate to properly and efficiently remove all the waste products generated by the factories and population of the area. This is partly a maintenance problem but an environmental problem has been created by the discharging of wastewater with an excessively high solids content and a dangerous level of chromium among other heavy metals and toxic materials.
Beginning in late 2000 an unknown quantity of the tannery effluent which previously had remained in stagnant waters and drains in the lowlands behind the Dhaka Flood Protection Embankment was being released through large underground pipes into the Buriganga River at Katasur near the Rayerbazar memorial. Tannery solid wastes have accumulated in the sludge deposits of drains since the construction of the embankment. However, these drains are flushed during the rainy season, the sludge being carried along as suspended sediment. During the dry season the area is submerged by tannery wastewater and the contaminated wastewater pond areas are now approximately 8-10 times larger than that of the pre-embankment period. It is quite possible that toxic sludge is accumulating on the bottom of the large ponds where it is unlikely to be pumped out.
The glue and paint industries also create pollutants which affect this area. No effort has been made to distinguish the impact of these two industries. There is a lesser problem related to the disposal of household wastes as only 32 per cent of local residences are connected to the sewer system.
Toxic chemicals and chromium: The Hazaribagh tanneries follow the practice of chrome-tanning used by 80 per cent of the tanneries in South Asian and African countries. In traditional chrome tanning practice only 50-60 per cent of the chromium applied is taken by the leather and the balance is discharged as waste. A multitude of hazardous chemicals are used for leather and dye treatment including: ammonium bicarbonate, chromic acetate, ethylene glycol, monoethyl ether, methylamine, o-nitrophenol, toluene diamine, 2, 4, 5-trichlorphenol, zinc hydrosulfite, zinc sulphate, tert-butylamine, among others. Chromium solutions are used to tan leather and most of the tanneries in the Hazaribagh area, save one or two, do not recover their chrome although this can be done at relatively low cost. Chrome can be recovered using MgO as an alkali to precipitate chromium as a thick high density slurry while the supernatant fluid is decanted. The recovered chromium is reused in many Indian tanneries. This system was introduced in India under a TNO (The Netherlands)-CLRI (India) cooperation agreement. The chrome recovery cost is only 30-40 per cent of the cost of fresh chromium and the pay back period of the entire system is 2-4 years. Chromium solution is however being loaded to the ponds and open waters through drains, channels and rain water. This certainly affects aquatic and terrestrial ecosystem in addition to ground water.
Chromium, one of the most common elements in the earth's crust and seawater, exists in our environment in several oxidation states, principally as metallic (Cr0), trivalent (+3), and hexavalent (+6) chromium. The latter is largely synthesized by the oxidation of the more common and naturally occurring trivalent chromium and is highly toxic. Trivalent chromium, found in most foods and nutrient supplements, is an essential nutrient with very low toxicity. However, hexavalent (+6) chromium (VI) [Cr(VI)] is a ubiquitous environmental and industrial contaminant loading from the tannery and absorbed in our body (through drinking water, eating fish, vegetables, fruits and other food grains) is strongly associated with a higher incidence of human lung cancer. It also affects in human renal system particularly of diabetic patients. Therefore, it is very easy to come up with a conclusion that the toxic discharge from factories in Bangladesh had worsened the quality of life and have a serious affect on public health (out breaks of different diseases).
Effect of pesticidesPesticides are designed to (in most cases) kill pests (insects). But indiscriminate use of pesticides (over doses) especially in the agriculture for high yield and DDT in dry fish industries has posed a serious threat to the environment. Many pesticides can also pose risk to humans. However, to determine risk, one must consider both the toxicity or hazard of the pesticide and the likelihood of exposure. A low level of exposure to a very toxic pesticide may be more dangerous than a high level of exposure to a relatively low toxicity pesticide.
Pesticides commonly use in Bangladesh are, Furadan (Carbofuran pesticide) is in the category of highly hazardous. Moderately hazardous pesticides are Marshal 6G & 20EC (Carbosulfan), Suntap 50SP (Cartap), Ripcord 10EC (Cypermethrin), Sumithion (Fenitrothion), KAP 50EC (Phenthoate), Sevin 10% Dust (Carbaryl), Ustad 10EC (Cypermethrin), Sumibus 75EC (Fenitrothion + BPMCS) and Thiovit 80WP ( sulfur) in the category of acute hazard. Most of them are categorized as moderately hazardous. In addition, the excessive applications of these pesticides create further threat to the safety of the human and animal health. Let us go back to newspaper reports published in the Manabzamin (6th September, 1999), Bhorer Kagaz (1st September 1999) and Inqilab (2nd September, 1999). The day was 31st August, 1999. In the village Dakatia of Jessore, people watched mass death of sparrows in vegetable fields. A preliminary estimate of the villagers said that bodies of about 5,000 sparrows could be counted. There were more. In the early morning, it was seen that in the eggplant field, several hundreds of sparrows were lying in a restless condition, flickering wings with no strength. It was a painful process of death that brought tears in the eyes of many people around.
If precautionary and curative measures are not taken against these pollution, days are not far that an unpredicted catastrophe may occur in Bangladesh and we follow the sparrows.
Some proposalsGovernment should get amended existing environmental policy and implement environmental management techniques practically with the development of annual monitoring system and evaluation for each section (for example fisheries, livestock, agriculture, coastal, marine, river, underground water, meteorology, geology etc).
Coordinate each section with data sharing followed by top down/bottom up method.
Get all municipal corporations involved very much actively in the environmental issues providing particular urbanisation planning for the real estate companies. Help create public motivation through mass media -- television, radio, rally, advertisement, meeting, festivals etc. Make it obligatory for all NGOs, industries and companies to get themselves involved environmental issues and its protection following the environmental policy. Provide financial aid (small scale) to NGOs and other environmental companies with a proper monitoring system. Suggest each national and public university to conduct applied research on environmental issues for future decision making. Make a proper plan to keep sustainable environmental ecosystem in the Bay of Bengal (July 13, 2007Md. Jahangir Sarker, Ph.D. is a Post Doctoral Researcher, National Institute of Advanced Industrial Science and Technology (AIST), Ministry of Economics and Trade, Japan) Top of page
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