Table 3-7. Sources and Amounts (tons/year) of Volatile Organic Compounds 

 Causing Air Pollution in Maine. a 



Source 



Tons/Year 



Storage, transportation, and marketing 



of petroleum products 

 Industrial processes 

 Industrial surface coating 

 Nonindustrial surface coating 

 Other solvent use 

 Miscellaneous sources (open burning, solid 



waste disposal, and fuel combustion) 

 Mobile sources (e.g., highway vehicles) 



10,600 



905 



2516 



1512 



2426 



10,534 



56,963 



TOTAL 



85,516 



a Maine Department of Environmental Protection 1979. 



Acid rain is the dominant destructive constituent of the human-induced 

 atmospheric pollution that affects natural systems in coastal Maine. Acid 

 rain influences natural systems in four ways: (1) by introducing toxic levels 

 of acidity into the environment, (2) by introducing heavy metals and PCB into 

 the environment (particularly near metal smelters and industrial areas), (3) 

 by introducing plant nutrients into the environment, (4) by introducing 

 organic molecules into the environment. 



The response of natural systems to acid rain is poorly understood at present 

 but is under investigation. The focus of investigative effort concerning the 

 effects of acid rain on natural systems has centered on the impact of acidity 

 and the effect of heavy metals on natural systems. The impact of acid rain on 

 natural systems in coastal Maine is discussed below. 



Acid precipitation . Over the past 30 years, scientists have noted an 

 increase in the acidity of rain in Europe and the United States (Likens et al. 

 1979 and 1972). In the United States, the most noticeable increases have been 

 measured in the Northeast. This trend is due to the rise in emissions of 

 sulfur and nitrogen oxides accompanying the rise in burning of fossil fuels. 

 The increase in acidity has already brought about changes in the ecology of 

 some Maine lakes (changes have not been studied in coastal lakes) and 

 threatens other natural systems. Acid precipitation tends to interfere with 

 critical ecosystem interactions. Changes in acidity accelerate or retard the 

 chemical release and transport of minerals, nutrients, and heavy metals 

 through biota, soils, and water courses. 



A common measure of acidity is pH, which is the negative logarithm of the 

 concentration of hydrogen ions. The pH scale ranges from to 14, with 7 

 being the neutral point. Values lower than 7 are acidic. Since the pH scale 



3-37 



10-80 



