The problem of pollution of the oceans. OBZhD

BASICS OF SAFE LIFE
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The problem of pollution of the oceans. Basics of safe life

Fundamentals of Safe Life Activities (OBZhD)

Oil and oil products. Oil is a viscous oily liquid that is dark brown in color and weakly fluorescent. Oil consists primarily of saturated aliphatic and hydroaromatic hydrocarbons. The main components of oil - hydrocarbons (up to 98%) - are divided into 4 classes:

Paraffins (up to 90% of the total composition) are stable substances whose molecules are expressed by a straight and branched chain of carbon atoms. Light paraffins have maximum volatility and solubility in water.

Cycloparaffins (30-60% of the total composition) are saturated cyclic compounds with 5-6 carbon atoms in the ring. In addition to cyclopentane and cyclohexane, bicyclic and polycyclic compounds of this group are found in oil. They are very stable and poorly biodegradable.

Aromatic hydrocarbons (20-40% of the total composition) are unsaturated cyclic compounds of the benzene series, containing 6 less carbon atoms in the ring than cycloparaffins. Oil contains volatile compounds with a molecule in the form of a single ring (benzene, toluene, xylene), then bicyclic (naphthalene), polycyclic (pyrene).

Olefins (up to 10% of the total composition) are unsaturated non-cyclic compounds with one or two hydrogen atoms at each carbon atom in a straight or branched chain molecule.

Oil and petroleum products are the most common pollutants in the World Ocean. By the beginning of the 80s. About 6 million tons of oil entered the ocean annually, which accounted for 0,23% of world production. The greatest oil losses are associated with its transportation from production areas. Emergency situations, tankers draining washing and ballast water overboard - all this causes the presence of permanent fields of pollution along sea routes. In 1962-1979 As a result of accidents, about 2 million tons of oil entered the marine environment.

Over the past 40 years, since 1964, about 2000 wells have been drilled in the World Ocean, of which 1350 were equipped in the North Sea alone. Due to minor leaks, 0,1 million tons of oil are lost annually. Large masses of oil enter the seas through rivers, domestic wastewater and storm drains. The volume of pollution from this source is 2 million tons/year. 0,5 million tons of oil are lost annually through industrial waste. When oil enters the marine environment, it first spreads as a film, forming layers of varying thickness. By the color of the film, you can determine its thickness, and this value makes it possible to determine the amount of oil in the water (Table 1).

The oil film changes the composition of the spectrum and the intensity of light penetration into water. The light absorption of thin films of crude oil is 1-10% (280 nm), 60-70% (400 nm). A film with a thickness of 30-40 microns completely absorbs infrared radiation.

When mixed with water, oil forms two types of emulsion: direct ("oil in water") and reverse ("water in oil"). Direct emulsions, composed of oil droplets with a diameter of up to 0,5 microns, are less stable and are characteristic of oils containing surfactants. When volatile fractions are removed, oil forms viscous inverse emulsions that can remain on the surface, be transported by currents, washed ashore and settle to the bottom.

Table 1. Determination of the amount of oil in seawater by film thickness

Appearance	Thickness, microns	Amount of oil, l/km2
Barely noticeable	0,038	44
silver reflection	0,076	88
Traces of coloring	0,152	176
Brightly colored stains	0,305	352
Dull-colored	1,016	1 170
dark colored	2,032	2310

Pesticides. This is a group of artificially created substances used to control plant pests and diseases. Pesticides are divided into the following groups:

insecticides - to combat harmful insects;
fungicides and bactericides - against fungal and bacterial plant diseases;
herbicides - to kill weeds.

It has been established that pesticides, while destroying pests, harm many beneficial organisms and undermine the health of biocenoses. In agriculture, there has long been a problem of transition from chemical (polluting) to biological (environmentally friendly) methods of pest control. Currently, more than 5 million tons of pesticides are supplied to the world market. About 1,5 million tons of these substances have already become part of terrestrial and marine ecosystems through ash and water.

Industrial production of pesticides is accompanied by the emergence of a large number of by-products that pollute wastewater. Representatives of insecticides, fungicides and herbicides are most often found in the aquatic environment. Synthesized insecticides are divided into three main groups: organochlorine, organophosphorus and carbonates. Organochlorine insecticides are produced by chlorination of aromatic and heterocyclic liquid hydrocarbons. These include DDT and its derivatives, in whose molecules the stability of aliphatic and aromatic groups increases in the joint presence, as well as all kinds of chlorinated derivatives of chlorodiene (eldrin). These substances have a half-life of up to several decades and are very resistant to biodegradation.

In the aquatic environment, polychlorinated biphenyls are often found - derivatives of DDT without an aliphatic part, numbering 210 homologues and isomers. Over the past 40 years, more than 1,2 million tons of polychlorinated biphenyls have been used in the production of plastics, dyes, transformers, and capacitors. Polychlorinated biphenyls (PCBs) enter the environment as a result of industrial wastewater discharges and the combustion of solid waste in landfills. The latter source supplies PCBs into the atmosphere, from where they fall with precipitation in all regions of the globe. Thus, in snow samples taken in Antarctica, the PCB content was 0,03-1,2 kg/l.

Synthetic surfactants (surfactants). Detergents (surfactants) belong to a large group of substances that reduce the surface tension of water. They are part of synthetic detergents (CMC), widely used in everyday life and industry. Together with wastewater, surfactants enter continental waters and the marine environment. CMCs contain sodium polyphosphates in which detergents are dissolved, as well as a number of additional ingredients that are toxic to aquatic organisms: fragrances, bleaching agents (persulfates, perborates), soda ash, carboxymethylcellulose, sodium silicates. Depending on the nature and structure of the hydrophilic part, surfactant molecules are divided into anionic and cationic, amphoteric and nonionic. The latter do not form ions in water. The most common surfactants are anionic substances. They account for more than 50% of all surfactants produced in the world.

The presence of surfactants in industrial wastewater is associated with their use in processes such as flotation concentration of ores, separation of chemical technology products, production of polymers, improving conditions for drilling oil and gas wells, and combating equipment corrosion. In agriculture, surfactants are used in pesticides.

Compounds with carcinogenic properties. Carcinogenic substances are chemically homogeneous compounds that exhibit transforming activity and the ability to cause carcinogenic, teratogenic (disruption of embryonic development processes) or mutagenic changes in the body. Depending on the conditions of exposure, they can lead to growth inhibition, accelerated aging, disruption of individual development and changes in the gene pool of organisms. Substances with carcinogenic properties include chlorinated aliphatic hydrocarbons, vinyl chloride, and especially polycyclic aromatic hydrocarbons (PAHs).

The maximum amount of PAHs in sediments of the World Ocean (more than 100 μg/kg of dry matter weight) was found in tentonically active zones subject to deep thermal effects. The main anthropogenic sources of PAHs in the environment are the pyrolysis of organic substances during the combustion of various materials, wood and fuels.

Heavy metals. Mercury, lead, cadmium, zinc, copper, and arsenic are heavy metals and are common and highly toxic pollutants. They are widely used in various industrial processes, therefore, despite treatment measures, the content of heavy metal compounds in industrial wastewater is quite high. A large number of compounds enter the ocean through the atmosphere. For marine biocenoses, the most dangerous are mercury, lead and cadmium.

Mercury is transported to the ocean by continental runoff and through the atmosphere. The weathering of sedimentary and igneous rocks releases 3,5 thousand tons of mercury annually. Atmospheric dust contains about 12 thousand tons of mercury, a significant part of which is of anthropogenic origin. About half of the annual industrial production of this metal (910 thousand tons / year) ends up in the ocean in various ways. In areas polluted by industrial waters, the concentration of mercury in solution and suspended matter increases greatly. At the same time, some bacteria convert chlorides into highly toxic methylmercury. Contamination of seafood has repeatedly led to mercury poisoning of coastal populations. By 1977, there were 2 victims of Minomata disease, which was caused by waste from vinyl chloride and acetaldehyde production plants that used mercuric chloride as a catalyst. Insufficiently treated wastewater from factories flowed into Minomata Bay.

Lead is an element found in all components of the environment: rocks, soils, natural waters, atmosphere, living organisms. Finally, lead is actively dissipated into the environment during human economic activity. These are emissions from industrial and domestic wastewater, from smoke and dust from industrial enterprises, and from exhaust gases from internal combustion engines. The migration flow of lead from the continent to the ocean occurs not only with river runoff, but also through the atmosphere. With continental dust, the ocean receives 20-30 tons of lead per year.

Discharge of waste into the sea for the purpose of disposal (dumping). Many countries with access to the sea conduct marine disposal of various materials and substances, in particular, dredging soil, drilling slag, industrial waste, construction waste, solid waste, explosives and chemicals, and radioactive waste. The volume of burials is about 10% of the total mass of pollutants entering the World Ocean.

The basis for dumping is the ability of the marine environment to process large quantities of organic and inorganic substances without much damage to water. However, the possibilities of the environment are not unlimited. Therefore, dumping is considered as a necessary measure due to imperfect technology.

Industrial slag contains a variety of organic substances and heavy metal compounds. Household waste on average contains (by dry matter weight) 32-40% organic matter, 0,56% nitrogen, 0,44% phosphorus, 0,155% zinc, 0,085% lead, 0,001% mercury, 0,001% cadmium. During discharge (the passage of material through a column of water), some of the pollutants go into solution, changing the quality of the water, while others are sorbed by suspended particles and pass into bottom sediments. At the same time, the turbidity of the water increases. The presence of organic substances often leads to the rapid consumption of oxygen in water and often to its complete disappearance, dissolution of suspended matter, accumulation of metals in dissolved form, and the appearance of hydrogen sulfide.

The presence of a large amount of organic substances creates a stable reducing environment in the soil, in which a special type of silt water appears, containing hydrogen sulfide, ammonia, and metal ions. Benthos organisms and others are exposed to varying degrees to the effects of discharged materials. In the case of the formation of surface films containing petroleum hydrocarbons and surfactants, gas exchange at the air-water interface is disrupted.

Pollutants entering the solution can accumulate in the tissues and organs of hydrobionts (marine living organisms) and have a toxic effect on them. The discharge of dumping materials to the bottom and prolonged increased turbidity of bottom water lead to death from suffocation of sedentary forms of benthos. In surviving fish, mollusks and crustaceans, their growth rate is reduced due to deteriorating feeding and breathing conditions. The species composition of a given community often changes.

When organizing a control system for waste discharges into the sea, locating dumping areas and determining the dynamics of pollution of sea water and bottom sediments is of decisive importance. To determine the possible volumes of discharge into the sea, it is necessary to carry out calculations of all pollutants in the gross discharge.

So, the effects of anthropogenic impact on the aquatic environment are manifested at the individual and population-biocenotic levels. The long-term effect of pollutants leads to a simplification of the ecosystem.

Authors: Aizman R.I., Krivoshchekov S.G.

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