Atmospheric fallout comes from a multiplicity of emission sources to air - industrial processes, vehicles emissions, incineration of domestic waste and others. Dioxins are the most important EDSs via this route. The permitted particulate quantities (Yes there are permitted amounts that can be released to air) settling on buildings, road, land, etc. In heavy rains these are washed off into the storm drain system that enter directly into the rivers with little or no processing. It is my opinion that the quantities of dioxins entering the river systems are likely to rise over the next 10-20 years due to recent Government pronouncements. They (Government) would like to see 160 new large incinerators built nationally, to tackle the waste problem and the impending EU directives on landfilling.
Again there are regulations on air emissions for incinerators. However, some quantities of dioxins are released to air (Space doesn’t allow me to go into more detail.).
Landfill leachate enters the river systems and some stillwaters (Yes stillwater anglers it’s your problem as well!) by direct and indirect leaching - streams, brooks, rivers, water table and groundwater. Historically landfills came into being because there was an available hole in the ground created through some form of extraction for minerals - shale, gravel, clay, rock, etc. Large number of these being found, in, or near river valleys with the above connections to a major river system. Until the late 70s early 80s most were not lined or had any ground engineering works to avoid leaching. Compounding the problem, before the above date, co-disposal of domestic and potentially toxic waste took place routinely. A study of landfills nationally in the early 90s by Friends of the Earth, found that 1300 waste tips were seeping poisons into the ground water. Clearly then, many substances containing EDSs were disposed of in such tips, one of the most serious being PCB’s. What is not known about this type of co-disposal, is the chemical reaction between the many substances when subjected to long-term heating as happens in landfills.
Modern engineered landfills are not immune from emitting EDSs as the aqueous discharge from them is collected on site in an underground storage tank, which at a later date, tankered off to the sewage plant for processing (no stripping remember) and final disposal. The water being returned to the river system, and some of the sewage sludge being used on agricultural and low-grade land as fertilizer. However, because of the levels of contamination of the sludge with heavy metals etc., regulations have be brought in on how much can be used on such land. Inevitably though, some run off from the treated land is likely to occur, which in turn will enter the surrounding watercourses and connecting river(s) adding to the EDSs load of them.