In the second of this two-part series in our Cleaning Up The Mess space, Dr AZAD MOHAMMED Eco-toxicologist and UWI lecturer tells us public indifference to pollution, lack of appropriate legislation and enforcement of existing laws have added to the ever growing problems that continue to plague out environment.
Little is being done to assess the true extent of pollution in our natural environment but I have provided a list of obvious pollutants.
Nutrients
The main potentially-polluting nutrients include nitrogen, ammonia (a gas containing nitrogen and hydrogen), phosphorus and sulphur. They arise from the natural breakdown of plant residues and soil organic matter, fertilisers, urine and manure, silage, landfill sites, wastewater and industrial effluents, power generation and sewage. Much of the nutrients that enter our environment is generated from animal rearing operations, non-functional sewage treatment plants and agricultural runoff.
Pesticides
These include herbicides, insecticides and fungicides that are used in gardens, in agriculture, on roadside and trackside maintenance, and in golf courses. Current usage patterns in Trinidad and Tobago are largely unregulated.
Heavy metals
Heavy metals are widely-used ingredients for chemical compounds used in industry and also exist naturally in soils at low concentrations. Industrial contaminated land can be a source of heavy metals leaching into the environment. They can be found in fuel, chemicals, waste materials and batteries. In high concentrations they are toxic to humans, animals, fish and plants.
Solid waste
Materials, such as tyres, used appliances, beverage containers, plastics and bottles, all contribute to land and water pollution. Many of these find their way into rivers, temporary dumps along roadsides and in coastal marine areas.
Suspended and settle able solids
Suspended solids are mineral and organic particles that remain suspended in water. They sink very slowly or are easily re-suspended by water turbulence. Suspended solids might be eroded soil or decayed leaves. Wastewater from sewage works and industry might also carry suspended solids into water bodies. Suspended solids cause water to be turbid and this cloudiness reduces light levels.
Turbidity can also be a sign of other pollution since nutrients, pesticides and metals can be attached to the suspended particles. Settleable are mineral or organic solids which can settle onto the beds of rivers and lakes where they can prevent fish spawning and kill bottom dwelling animals.
Oxygen depleting substances
Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) tests are analytical methods for measuring the amount of oxygen consumed during the microbial or chemical breakdown of oxygen-depleting substances in water, such as sewage and farm slurry. High levels of BOD and COD indicate a heavily polluted water body making it less suitable for aquatic life.
Pathogens
These are present in faeces from human and animal sources, including wildlife and includes bacteria, fungi, and viruses. They can enter water through poor wastewater management or poor handling of manures, slurry and other farm wastes. They may also be carried directly off fields by heavy rainfall or enter water bodies where stock and wildlife have direct access for drinking purposes or where people use river for recreational purposes. Some of the most common pathogens include fecal coliforms, E.coli, cholrea vibrio.
Hydrocarbons
These include vegetable and mineral oils (including petrol, diesel, white spirit, heating and lubricating oil), and chlorinated solvents, such as dry cleaning fluids, motor oil, wastewater from petroleum refining.
Persistent organic pollutants (POPs)
These are chemicals that are capable of long-range transport, accumulate in human and animal tissue, and have a significant impact on human health and the environment, even at low concentrations. They include such substances as dioxin, PCBs, pesticides and flame retardants. Various studies on the west coast of Trinidad has already shown the presence of many of these POPs in sediments and fish tissues.
Landfill sites
Landfill sites can be a source of pollution into the aquatic environment through several mechanisms. Rainfall enters a site while waste is being deposited and, as it passes through the waste, it collects polluting compounds including ammonia, heavy metals, chloride and oxygen-depleting substances.
Waste itself contains water and this is released during degradation processes that occur after the landfill has been sealed. As materials decompose it also generate gaseous materials, such as methane, carbon dioxide and other toxic air pollutants.
Contaminated land
Contaminated land is largely an historical legacy from former industrial activity conducted previously.
The nature of the contamination can vary greatly from heavy metals, hydrocarbons and organic chemicals. Water contamination from these sites occurs largely as a result of rainfall which flushes chemicals, contaminated sediment and dissolved compounds into nearby streams or into groundwater beneath a site. Contamination of groundwater and surface waters can also occur where there is poor storage and handling of chemicals such as solvents or oils giving rise to spillage.
Road runoff and urban stormwater discharge
Roads, drive ways and car parks are large runoff-producing areas in the urban environment. This runoff is often contaminated with sediment, litter, chemicals, oil and petrol, and with toxic metals from motor vehicles. Water carrying these contaminants run off into drains and nearby watercourses where effects can manifest in various organisms.
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