Polluting agents
Contenido
Existen diferentes tipos de contaminantes que pueden ser químico, físico o biológico, que se definen por sus distintos tipos a la presencia que se da en la contaminación, pero se ve que cada una es considerado como un agente contaminante.
Dumping of urban solid waste
Domestic solid waste generates enormous amounts of waste (organic 30%, paper 25%, plastics 7%, glass 8%, textiles 10%, minerals 10%, metals 10%). It is a priority to make economic and social development compatible with the protection of nature, avoiding attacks on living ecosystems and the environment in general. Recycling or waste minimization is extremely necessary to avoid the continuous consumption of exhaustible raw materials and their polluting discharge into nature.[71].
Common municipal landfills are a source of chemicals entering the soil environment (and sometimes underground water layers), emanating from the wide variety of accepted waste, especially substances illegally dumped there, or from old landfills from before the 1970s when light controls were implemented in the United States or the European Union. There has also been an unusual release of polychlorinated dibenzodioxins, commonly called Dioxins for simplicity, such as TCDD").[72].
Organic waste is biodegradable. Naturally, these wastes can be recovered and used, for example, to manufacture an effective and beneficial fertilizer for crops.
One cause of organic pollution is animal waste from animal farms. Animal excrement and slurry generate significant pollution; there are a large number of research studies to convert these contaminants into usable and safe products.[73].
Human waste is generally treated in treatment plants"), but in underdeveloped countries with few resources and that do without these plants, they release their untreated waste, contaminating the environment and mainly sources of drinking water, this brings many diseases to the population, such as cholera. Therefore, although waste of human origin degrades on its own over time, it is advisable to treat it for the sake of the health of the population.
Chemical agents
Currently, there are around 70,000 synthetic chemicals, with an increase of about 200 to 1,000 new chemical substances each year.[74] The effects produced by these substances are in some cases known, but in others little is known about their potential long-term effects on humans and the environment.[75] Thus, cancer caused by a chemical can, in some cases, take 15 to 40 years to resolve. manifest.
The agriculture sector is one of the sectors that indirectly produces the most pollution. The causes of pollution are the fertilizers and pesticides used for soil fertility and to fumigate crops from pests that reduce production. Through rain and irrigation, these products contaminate surface waters and aquifers.[73].
According to the Stockholm Convention on Persistent Organic Pollutants, nine of the 12 most hazardous and persistent organic compounds are pesticides.[76][77].
In 2001, a series of reports culminated in a book called Fateful Harvest"), which exposed the widespread practice of recycling industrial byproducts into fertilizers, contaminating the soil with various metals and substances.[78].
Dioxins are a series of chemical compounds that are very resistant to chemical or biochemical degradation and therefore end up accumulating in living organisms. They originate from the reaction of chlorine with organic matter and oxygen at high temperature. In 1940 dioxins did not exist, but the industrialization of organic chemical products associated with economic development that has occurred in the last seven decades has led to their appearance in certain plastics, pesticides, insecticides, among others, that contain significant amounts of chlorine.[79].
Heavy metals represent an important form of anthropogenic pollution. There are a series of heavy metals essential in the life cycle of living beings, the so-called trace elements. Other heavy metals have no biological function. From certain concentrations in living beings they can be dangerous. The main toxic metals found dispersed in any medium are mercury "Mercury (element)"), cadmium, lead, copper, zinc, tin, chromium, vanadium, bismuth and aluminum. Metals, similar to other polluting agents, are easily diluted in water. In the sea they are dispersed by marine currents, although some are deposited in the benthos. The actions of these metals on some marine organisms can affect their growth, inhibit their reproduction and even become lethal.
Lead is found in paints "Paint (material)" with lead, aviation fuel") and, although its use has been reduced in most countries, it is still used in gasoline as an anti-knock product. The atmospheric pollution that has caused the combustion of leaded gasoline has made this metal reach the sea. It is known that lead is deposited in the gills of fish, causing serious respiratory problems.
Mercury is the main marine polluting metal. It accumulates in fish and reaches humans through consumption, who are more sensitive to its toxicity and can suffer from mercury poisoning. The maximum legal limits in Spain in fish products is 0.5 mg/kg of mercury. In 2005, the Rovira i Virgili University of Tarragona published an application to evaluate, based on personal consumption, the risks of consuming fish due to its concentration of contaminants, compared to the benefits due to its nutrients.[80][81].
Cyanide is an anion of representation CN and consists of a carbon atom with a triple bond with a nitrogen atom. Cyanides are most commonly referred to as salts with the anion CN.[82][83] Most cyanides are highly toxic.[84] Cyanide poisoning occurs when an organism is exposed to an ion-emitting compound (CN) dissolved in water. Cyanide has many uses, currently it is used in industry, to exterminate pests, and even in medicine. Under controlled use it may be safe.
In mining it is used to extract gold, copper, zinc and silver, using a very controversial process[85] and due to this its use is prohibited in several countries and territories.[86] This is due to several ecological disasters that have occurred due to cyanide spills or leaks from mines or the collapse of tailings dams. And because through the gold cyanidation process, apart from obtaining the required metals, heavy metals of little economic importance are also extracted and deposited in the tailings dams and sometimes these are abandoned without carrying out remediation processes.
A notorious case was the Baia Mare spill on January 30, 2000 in northern Romania, when 130,000 m³ of cyanide diluted in water was spilled and then reached the Danube and Tisza rivers through tributary rivers.[87] The high concentration of cyanide in that spill resulted in the almost total destruction of aquatic fauna and flora in the Someş River and then in the Tisza. The effects of the spill reached the Black Sea. Hungary filed a complaint against the Australian company Esmeralda, majority shareholder of the shares of the company Aurul from Baia Mare.
The consumption of detergents is constantly increasing in the world. In 1995, 10.2 million tons were consumed and estimates for 2005 were 13.8 million tons.
Oil dispersants are liquids used in oil spills and perform the function of making the oil soluble in water, and transferring it from the water surface to the water column "Water column (ecology)"). There are several brands of dispersants, one of the best known is Corexit, used in the Exxon Valdez environmental disasters and the recent Deepwater Horizon spill. One quality of dispersants is that they are sometimes more toxic to the environment and health than oil itself and to bioaccumulate in the tissues of living beings.[88][89] In addition, the fact that dispersants transfer floating oil into the water column means a serious risk for beings that live under the sea and for the seabirds that feed on them.
Oil
Petroleum is one of the hydrocarbons of fossil origin, the result of the transformation of organic matter from zooplankton and algae that, deposited in large quantities on the anoxic bottoms of seas or lake areas in the geological past, were subsequently buried under heavy layers of sediment.
Petroleum is a homogeneous mixture of organic compounds, mainly hydrocarbons insoluble in water. Many of these compounds are highly toxic and cause cancer (carcinogens). Oil is very lethal to fish, killing them quickly at a concentration of 4000 parts per million (ppm)[90] (0.4%). "Only one-quarter (volume unit)" of gasoline is enough to make 250,000 gallons of seawater toxic to wildlife."[91] It is equivalent to the concentration of 1 ppm of petroleum or petroleum distillates to cause congenital diseases in birds.[92].
Benzene, present in petroleum and gasoline, is known to cause leukemia in humans.[93] The compound is known to reduce leukocytes in human blood, leaving people exposed to this compound more susceptible to infections.[93] "Studies have linked benzene exposures in the low parts per billion (ppb) range to terminal leukemia, Hodgkin's disease, and other diseases of the blood and immune system with exposures of between 5 to 15 years".[94].
Oil drilling is simply removing oil from a reservoir. This is often recovered as an oil-water emulsion, and demulsifying chemicals are used to separate the oil from the water. Oil extraction is expensive and often damages the environment. Extraction has evolved a lot since its beginnings, adding a wide variety of techniques and new technologies to the extraction process, but in some cases it is still polluting. For example, the case of the Lago Agrio oil fields in Ecuador where the soil and water of the region were contaminated and caused many health problems for the population. This was because the company in charge of the exploitation of the oil wells did not treat the produced water (contaminated water from inside the well), and accumulated it in outdoor pools without any prior treatment, this caused these contaminated waters to leak into the soils, rivers and underground water tables of the region.
Among domestic waste, plastics are one of the main components, accounting for 7% of its total weight and 20% of its volume. They are materials that are very resistant to the degradation imposed by nature and have a very high half-life. In 1955 it was a non-existent waste in most countries and today it has gained great prominence.[71].
They are known by their English acronyms: polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), high-density polyethylene (PDPE), low-density polyethylene (LDPE), etc.[71].
Given its high resistance to degradation and how useful its use is, currently practically indispensable, the way to reduce its proliferation as waste would be recycling. But to do so, it faces the problem that each plastic object has a different composition, which prevents its recycling. The ideal thing would be to homogenize the collection by type of plastic, but at the moment this problem has not been resolved.[71].
ionizing radiation
The unwanted presence of radioactive substances in the environment is called radioactive contamination and does not give an indication of the magnitude of the risks inherent to this contamination. This contamination can come from natural or artificial radioisotopes.
Natural sources come from certain chemical elements and their isotopes and cosmic rays, the latter are responsible for 80% of the dose received by people in the world (on average), the other percentage comes from medical sources such as X-rays. Low doses of radiation are not dangerous, the problem occurs when a person is exposed to these doses for a long time. Or you are exposed to high doses of radiation.
Artificial sources may come from spills or accidents in the production or use of radioisotopes, to a lesser extent radioactive fallout from atomic bombs and nuclear tests, other sources are spills or accidents with radioisotopes from nuclear medicine or xenon that is released during nuclear reprocessing of already used nuclear fuel, another is due to accidents in nuclear power plants.
The contamination levels can be low or high, when they are low they can still be detected by the instruments, and the radioisotopes are allowed to decay (lose their radioactivity if they are short-lived), but if they are slow to decay, cleaning is carried out, since low radiation for very long periods of time can be harmful to health.
High levels of radiation are more dangerous for people and the environment. People can be exposed to lethal levels of radiation, both externally and internally, due to accidents or deliberately involving large amounts of radioactive material. The biological effects of external exposure to radioactive contamination are no different from radiation sources such as X-ray machines, and are dependent on the absorbed dose.
The biological effects of radioisotope deposition depend largely on the activity (of the radioisotope) and the biodistribution and elimination rates of the radioisotopes, also depending on the chemical element. The effects also depend on the chemical toxicity of the deposited material, regardless of its radioactivity. Some radioisotopes are distributed throughout the body and are quickly removed, as is the case with tritiated water. Some organs concentrate certain elements and also the radioisotopes of their radioactive variants. This leads to a lower elimination rate of the radioisotopes. For example, the thyroid gland accumulates a large percentage of iodine that enters the body. Large amounts of radioactive iodine can damage or destroy the thyroid, while other tissues are affected to a lesser extent. Radioactive iodine is a common product of nuclear fission; It was one of the largest radioactive components released in the Chernobyl accident, leaving nine pediatric cases of thyroid cancer and hypothyroidism. During the Fukushima I nuclear accident, the Japanese government gave doses of iodine to the affected population to prevent cases of thyroid cancer.[107] On the other hand, radioactive iodine is used in the treatment of many thyroid diseases precisely because of how receptive the thyroid is to iodine.
Polluting gases
Vehicle engine emissions are one of the leading causes of air pollution.[117][118][119] China, the United States, Russia, Mexico, and Japan lead the world in emissions of air pollutants.
Air pollution from agriculture comes from the cutting and burning of natural vegetation, as well as from the spraying of pesticides and herbicides.[120].
They are gases in the atmosphere that absorb "Absorption (optical)") and emit solar radiation within the infrared range. This process is the fundamental cause of the greenhouse effect.[121] The main greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrogen oxides "Nitrogen oxide (I)"), and ozone. In the solar system, the atmospheres of Venus, Mars#Atmospheric_Characteristics "Mars (planet)"), and Titan#Atmosphere "Titan (satellite)") also contain greenhouse gases. Greenhouse gases strongly affect the Earth; Without them, the Earth's surface would be 33 °C (59 °F)[122] colder than today.[123][124][125].
Although all of them—except for some compounds such as CFCs—are natural, since they have existed in the atmosphere since before the appearance of human beings.
Since the beginning of the industrial revolution, the burning of fossil fuels has contributed to the increase in nitrogen oxides and carbon dioxide in the atmosphere, the latter from 280 ppm to 390 ppm, despite the absorption of a large part of the emissions through various natural "sinks" present in the Carbon Cycle.[126][127] It is estimated that methane is also increasing its presence for anthropogenic reasons (due to activity human). Furthermore, other problems are added to this increase in emissions, such as deforestation, which have reduced the amount of carbon dioxide retained in organic matter, thus indirectly contributing to the anthropogenic increase in the greenhouse effect. Likewise, excessive carbon dioxide is acidifying the oceans and reducing phytoplankton.
The Kyoto Protocol attempts to reduce emissions of six greenhouse gases (CO, CH, NO, as well as three fluorinated industrial gases: Hydrofluorocarbons, Perfluorocarbons) and Sulfur Hexafluoride to 1990 levels. By November 2009, 187 states had ratified the protocol.[128] However, this protocol expires in 2012.
The gases that deplete the ozone layer are of two types: of natural origin and of human origin. Natural ones are due to the presence of free radicals such as nitrogen monoxide (NO), nitrous oxide (NO), hydroxyl (OH), atomic chlorine (Cl), and atomic bromine (Br)) that are released into the atmosphere from natural sources.
The gases of human origin are chlorofluorocarbons (abbreviated as CFCs), they are gases that reduce the ozone present in the atmosphere, causing the ozone hole at the Earth's poles, through a photochemical reaction that occurs in the stratosphere due to the presence of solar UV-C rays. CFCs were used as refrigeration gases and in aerosol propellants.