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<br /> <br />s <br /> <br />Effects of Atmospheric Deposition <br />on the Quality of <br />Ground Water and Surface Water <br /> <br />In areas where soils have little capacity to buffer <br />acids in water, acidic precipitation can be a problem because <br />the infiltrating acidic water can increase the solubility of <br />metals, which results in the flushing of high concentrations <br />of dissolved metals into surface water. Increased concentra- <br />tions of naturally occurring metals such as aluminum may <br />be toxic to aquatic organisms. Studies of watersheds have <br />indicated that the length of subsurface flow paths has <br />an effect on the degree to which acidic water is buffered <br />by flow through the subsurface. For example, studies of <br /> <br />Figure 5-1. Acidity is higher (pH is <br />lower) in streams when most 01 the flow is <br />contributed by shallow soif water because <br />the water has had less time to be neutral- <br />ized by contact with minerals compared <br />to water that has traversed deeper <br />flow paths. (Modified from Robson, A., <br />Beven, K.J., and Neal, C., 1992, Towards <br />identifying sources of subsurface flow- <br />A comparison of components identified <br />by a physically based runoff model and <br />those determined by chemical mixing <br />techniques: Hydrological Processes, <br />v. 6, p. 199-214.) (Reprinted with <br />permission from John Wiley & Sons <br />Limited.) <br /> <br /> <br />7 <br /> <br />:; <br />:;; 6 <br />a: <br />.... <br />'" <br />~ <br />o <br />:J: 5 <br />~ <br /> <br />4 <br />o <br /> <br />ci <br />5: ~ 24 <br />0'" <br />~a:w <br />~w"" <br />w...." <br />~~~16 <br />~>:; <br />~~ffi <br />"'''0. <br /><Ow.... <br />~ ~ttl 8 <br />~....~ <br />~z~ <br />0" <br />I-ffi 0 <br />0. 0 <br /> <br /> 1.0 <br />~;: <br />oS <br />z~ <br />Ow <br />~~ 0.5 <br />a:~ <br />Oa: <br />0." <br />0", <br />a: <0 <br />0." <br />'" <br /> 0 <br /> 0 <br /> <br />watersheds in England have indicated that acidity was <br />higher in streams during storms when more of the sub- <br />surface flow moved through the soil rather than through <br />the deeper flow paths (Figure &--1). Moreover, in a study <br />of the effects of acid precipitation on lakes in the Adirondack <br />Mountains of New York, the length of time that water was <br />in contact with deep subsurface materials was the most <br />important factor affecting acidity because contact time <br />determined the amount of buffering that could take place <br />(Figure S-2). <br /> <br /> <br />100 <br /> <br />200 <br /> <br />500 <br /> <br />800 <br /> <br />900 <br /> <br />600 <br /> <br />300 <br /> <br />400 <br /> <br />700 <br /> <br />100 <br /> <br /> <br />700 <br /> <br />~\...) ,! <br /> <br />800 <br /> <br />900 <br /> <br />400 <br /> <br />500 <br /> <br />600 <br /> <br />200 <br /> <br />300 <br /> <br /> <br />1",,-'" <br />..,~ <br /> <br />~'A{' <br />0J'Vi "'. ~ <br />, / "tv'" V~ 1'" <br /> <br />(\ Deeper wa1er '\( <br /> <br />100 <br /> <br />400 500 600 <br />HOURS <br /> <br />800 <br /> <br />900 1,000 <br /> <br />200 <br /> <br />300 <br /> <br />700 <br /> <br />74 <br /> <br />1,000 <br /> <br /> <br />1,000 <br />