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Environmental factors affecting choice of disposal sites for harzadous and toxic substances

2020-02-16T08:43:00.001+01:00

Considering the effects that harzadous waste disposal sites exert on their surrounding ecosystem and environment, these sites should be located in places with the minimum destructive effects and the lowest environmental impacts.

The following are methods used for the disposal of hazardous wastes; land disposal of wastes, incineration, dumping in the sea, underground disposal, and deep well injection.

Landfill siting for harzadous and toxic waste is an extremely difficult task to accomplish because the site selection process depends on different factors and regulations.

Environmental factors are very important because the landfill may affect the surrounding biophysical environment and the ecology of the area.

The following geological environmental factors affect choice of disposal sites for hazardous and toxic wastes;

Land Use: The landfill footprint must not be located within 500m of an existing or planned sensitive land use (EPA, 2000). Sensitive land uses include, but are not limited to: schools, residences, hotels, restaurants, food processing facilities, churches, and municipal parks. Land uses such as heavy industry, forestry operations, mining, railways/rail yards, etc. are not considered sensitive land uses.

Ecological value of the flora and fauna: The direct and indirect spatial use of a landfill will destroy the actual vegetation and fauna. When making a decision, the ecological value of the actual vegetation and fauna should be evaluated carefully for the candidate area. Ecological value is based on diversity, naturalness and characteristic feature. An example of indirect use is the disturbance of the quietness in the surroundings caused by the activities on the landfill.

Topography: This has to do with the natural and physical features of the area. It is desirable to have a topographic surface that tends to shed water in order to reduce ponding and infiltration. Karst topography is a landscape formed by the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. Sanitary landfills should not be constructed on karst topography.

Steep Slope: A completely flat area is exposed to accumulations of water during raining seasons and a very steep slope can be easily eroded. If the slope is too steep, it is difficult and costly to construct the landfill. Slope is a very important factor when siting a landfill; hence higher slopes would increase surface runoff of pollutants from the landfill and thereby contaminate areas that are further away. The landfill area having steep gradient (where stability of slope would be problematic) should not be selected.

Groundwater level and Surface water bodies: The groundwater level of a designated site for landfill construction should be sufficiently below the base of excavation. Also landfills should be sited in areas where beneficial uses of groundwater is minimal because groundwater contamination by leachate is difficult to remediate. Landfills should not be sited close to surface water because contamination of water bodies could be hazardous to aquatic lives.

In essence, distance from surface and groundwater, access routes, residential areas, industries, power transmission lines, flood-proneness, faults, slope, and distance from gardens and agricultural lands are all geographical environmental factors that are considered during site selection for hazardous and toxic wastes so as to prevent or minimize the harmful effects of such wastes on the environment.

Classification of pesticides

2020-02-14T02:43:00.001+01:00

According to the World Health Organization (WHO), pesticides are chemical compounds that are used to kill pests, including insects, rodents, fungi and unwanted plants (weeds). Pesticides can be classified or grouped in many different ways some of which are outlined below.

CLASSIFICATION OF PESTICIDES BASED ON;

TARGET ORGANISM

Pesticides can be grouped based on the different types of organisms that they control. This class of pesticides include;

Insecticides - These are pesticides that specifically target and kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Examples of insecticides include parathion, malathion, diazinon, methyl parathion etc.

Fungicides - Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. Examples of fungicides include carbendazim, mencozeb, merpan, hexanconazole etc.

Bactericides - These are substances that kill bacteria. Bactericides are disinfectants, antiseptics or antibiotics. Examples of bactericidal are daptomycin, fluorquinolones, metronidazole, nitrofurantoin, contrimoxazole etc.

Herbicides - These are substances that are toxic to plants and used to destroy unwanted vegetation. Selective herbicides kill certain targets while leaving the desired crop relatively unharmed. Examples of herbicides include Dicamba, Glufosinate ammonium, atrazine, simazine etc.

2. CHEMICAL STRUCTURE (SOURCE)

Pesticides are also classified based on their source or chemical structure. This class of pesticides include;

Synthetic Pesticides - These are pesticides manufactured by man. They do not occur in nature. Examples of synthetic pesticides are organochlorines (toxaphene, dieldrin, aldrin), organophosphates (Diazinon, glyphosphate, malathion), Carbamates (Carbofuran, aldicarb, carbaryl) and pyrethroids (fenpropanthrin, deltamethrin, cypermethrin).

Organic Pesticides - These refers to pesticides produced from animal or plant parts. Organic pesticides are made from naturally occurring substances or self-made mixtures made from organic soaps and/or ethanol. Examples are pyrethrin, lime sulfur, sabadilla, garlic, onions, tobacco water, rotenone etc.

3. PHYSICAL STATE

Pesticides can also be classified based on their physical state or how they are formulated. Pesticides are formulated (prepared) in liquid, solid and gaseous forms. This class of pesticides is comprised of;

Liquid Pesticides - These include suspensions (flowables), solutions, emulsifiable concentrates, microencapsulated suspensions and aerosols.

Solid Pesticides - Includes dusts, particulates, granular, pellets, soluble granules, soluble powders, baits, tablets, dry flowables and wettable powders.

Gaseous Pesticides - These are typically fumigants.

4. TARGET RANGE

Pesticides can also be classified based on the range of pests they are capable of targeting. This class of pesticides include;

Broad Spectrum Pesticides - These are chemicals that kill a wide range of pests. They are also called non-selective pesticides and they target entire groups or species of organisms. Examples include organophosphate, carbamate, acetamiprid, pyrethroid and neonicotinoid insecticides.

Selective Pesticides - These are chemicals that kill only a specific pest or group of pests. These pesticides have a minimal impact on organisms that are not targeted by the pesticide. Examples include Primicarb, Bt, NPV and Indoxacarb.

The effects of deforestation on the environment.

2020-01-30T07:31:00.002+01:00

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