Chlorine anthropogenic sources

Article 5 (Measures to reduce or eliminate releases from unintentional production ) of the convention generally aims at regulating the reduction of total releases derived from anthropogenic sources (combustion/burning of organic material and chlorine at the same time) of the so called Annex C chemicals, which are HCBs, PCBsand PCDD/PCDF as well as their continuous minimisation and (where feasible) ultimate elimination. 

Second, reaction 8.9 and other relevant reactions appear to occur preferentially on available solid surfaces, which are often ice crystals but may also be particles of sulfate hazes from volcanic eruptions or human activity. Third, volatile bromine compounds are even more effective (via Br atoms) than chlorine sources at destroying ozone methyl bromide is released into the atmosphere naturally by forest fires and the oceans, but anthropogenic sources include the use of organic bromides as soil fumigants (methyl bromide, ethylene dibromide) and bromofluorocarbons as fire extinguishers (halons such as CFsBr, CF2BrCl, and C2F4Br2). 

All three chloroacetic acids (chloroacetic acid [MCA], dichloroacetic acid [DCA], and trichloroacetic acid [TCA]) are naturally occurring (7), with TCA being identified in the environment most frequently (reviews (278, 405 108)). However, these chlorinated acetic acids also have anthropogenic sources. The major source of natural TCA appears to be the enzymatic (chloroperoxidase) or abiotic degradation of humic and fulvic acids, which ultimately leads to chloroform and TCA. Early studies (409) and subsequent work confirm both a biogenic and an abiotic pathway. Model experiments with soil humic and fulvic acids, chloroperoxidase, chloride, and hydrogen peroxide show the formation of TCA, chloroform, and other chlorinated compounds (317, 410-412). Other studies reveal an abiotic source of TCA (412, 413). 

There are many anthropogenic sources of photolyzable chlorine (CI2, HOCl). These include cooling towers (chlorine is used to prevent bacterial growth within the system), water treatment and swimming pools, and industrial processes. Inventories for these processes are only available for limited regions and are urgently needed. 

In an international effort, the Reactive Chlorine Emissions Inventory (Keene et al., 1999, and references therein) was compiled which includes chlorine emissions from the following four source-type classes (i) oceanic and terrestrial biogenic emissions (ii) sea salt aerosol production and dechlorination (iii) biomass burning and (iv) exclusively anthropogenic sources like industry, fossil fuel combustion, and incineration. They provide numbers from atmospheric burdens and fluxes for the individual species and sources. 

In order to understand the full extent of the mercury problem in these times, one has only to consider the enormous loss rates. From the total of 2865 tons of mercury purchased in the U.S. in 1968, 76% or 2160 tons were lost to the environment. According to calculations of Kemp et al. (1974), the Lake Ontario reservoir contained a mass of 500 to 600 metric tons of "excess" mercury, i.e. discharged from anthropogenic sources. With the improvements in the methods of chlor-alkali electrolysis and by subsequent purification of waste streams the mercury loss has been reduced from 100 g per metric ton of manufactured chlorine to approx. 2 g per ton or less (Anon., 1973). The effect of these measures can be seen from concentration profiles of mercury in sediment cores taken off the mouth of Niagara River by Mudroch (1983), where a very distinct decrease from formerly approx. 4-7 ug Hg/g to less than lug Hg/g in recent years has occurred (Figure 2-6). 

From the standpoint of air pollution, halogenated hydrocarbons are particularly significant, especially the group of chlorinated hydrocarbons from anthropogenic sources, which include chemicals for plant protection, industrial solvents, cleansers and fire extinguishing agents. Among natural sources, forest fires also contribute to the emissions of chlorinated hydrocarbons. 

Chloroform is one of the chlorinated derivatives of methane, supplied into the atmosphere only from anthropogenic sources. It may be formed as a side product during the water chlorination by the following reactions [49] ... 

Among various natural sources, the largest amounts of chlorinated hydrocarbons are supplied into the air by forest fires. In the combustion of cellulose, 2.2 mg of methyl chloride are formed per 1 g of substance burnt. Anthropogenic sources include the combustion of PVC (polyvinyl chloride) wastes, burning of plants in agriculture and uncontrolled fires resulting from human activity. 

It is interesting that the Cl and Na patterns are not well correlated and that for most of the 24 hours the Cl/Na ratio is much greater than the seawater value of 1.8. In the Livermore study (6) the patterns were well correlated, and the variation of the Cl/Na ratio was a factor of two with a maximum value of 1.6. The anomalous Na and Cl behavior for December 9-10 was repeated in Benicia on other days. This indicates the possible presence of an anthropogenic source of chlorine (Cl) in the area. 

Chemically, chloramines can form in the atmosphere and may be washed out in rainfall chlorine contributed by anthropogenic sources of industrial origin can combine with ammonia in precipitation resulting in the formation of a fairly stable oxidizing agent. 

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