Atmosphere-Biosphere Interactions Toward a Better Understanding of the Ecological Consequences of Fossil Fuel Combustion (1981) / Chapter Skim
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8 Acid Precipitation
8 Acid Precipitation
Pages 140-182
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From page 140... ...
Congress on August 2, 1979, as "one of the most serious global pollution problems associated with fossil fuel combustion," rivaled only by the buildup of carbon dioxide in the atmosphere. The topic, generally known as "acid rain," has been of much international concern because acids are deposited far from the sources of their precursors.
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From page 142... ...
While SO2 emissions have not changed greatly for several decades, owing to a switch from coal to other fuels and to increased control of gaseous sulfur emissions, there was unquestionably a great increase in anthropogenic sulfur emissions in the 20th century, causing increased sulfate deposition in remote regions (see Figure 8.1~. Despite the relative constancy of annual SO2 emissions during the past century, three technological changes may cause the emissions to produce acid precipitation more efficiently.
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From page 143... ...
1. Volcanoes, producing locally acid rain Fires in deposits of fossil fuel such as coal or lignite Forest fires, entraining alkaline particulates into the atmosphere Dust storms, entraining alkaline soil particles into the atmosphere
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From page 145... ...
145 6-.0 Q 5.8 5.4 pH 5.0 4.6 4.2 5.8 5.4 pH 5.0 4.6 4.2 5.8 5.4 pH 5.0 5.0 4.2 I I 1 1 1955 1960 1965 1970 YEAR (a) — Roba~ksdalen I_.
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From page 146... ...
1956 1960 1964 1968 1972 1976 FIGURE 8.4 Average stack height and tallest stack reported among power plants burning fossil fuels (bituminous coal, lignite, oil) included in biannual design surveys of new power plants, 1956-1978.
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From page 147... ...
As a solution of bicarbonate -- such as a lake -- is titrated by a constant addition of strong acid there is little resulting change in pH until 80 to 90 percent of the bicarbonate has been consumed according to the reaction: H+ + HCO3 -, H2CO3 ~ H2O + CO2 Once the bicarbonate has been converted into carbon dioxide and lost to the atmosphere, the acid (hydrogen ions) accumulates and the pH decreases rapidly (Figure 8.5~.
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From page 148... ...
148 Bir:~rhc~n~t`? Transition Lakes 7.0 pH 6.05.04.0; Acid Lakes \ ..............
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From page 149... ...
The bog moss, Sphagnum, generates in its cell walls polyuronic acids (Clymo 1964) , whose hydrogen ions are exchanged for metal cations from precipitation (Gorham and Cragg 1960~.
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From page 150... ...
2 ~ on Goof ~ ~11-/ ~ 11' o %....
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From page 151... ...
. I 1 970 Biological Acidification Induced by Man's Activities Normal Background of Biological Acidif ication l Anth ropogen ic Mineral Acids _ .
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From page 152... ...
(1980) found that 70% of the lake's alkalinity had been depleted before pH values decreased detectably below normal.
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From page 153... ...
While this may be due in part to the co-deposition of hydrogen ion and trace metals emitted from anthropogenic sources (discussed in Chapter 4) , ion exchange from acidified soils and lake sediments are more important sources in many cases.
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From page 154... ...
t 250 (,uEq1-') O average for 170 lakes in the Sierra Nevada, California x average for 109 lakes in the Experimental Lakes area, northwestern Ontario average for 216 lakes in the Adirondack Mountains, New York average for 11 years at Hubbard Brook, New Hampshire (Schof ield, personal commu nication)
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From page 155... ...
155 Alk.
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From page 156... ...
..: ·~ ~ I 4.0 5.0 6.0 7.0 pH FIGURE 8.10 The pH values and aluminum contents in lakes on the Swedish west coast, 1976.
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From page 157... ...
Dickson (1980) has shown that increased aluminum concentrations precipitate phosphorus from lake water, particularly in the pH range 4.5 to 6.0 (Figure 8.111.
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From page 158... ...
Fifty and 100 ,ug of orthophosphate were added to one-liter samples from Lake Horsikan (clear lake water with an initial pH of 4.1 and containing 0.5 mg aluminum per liter) , and 100,ug of orthophosphate was added to one-liter samples of humic lake water (with an initial pH of 6.2 and containing 0.2 mg aluminum per liter that is mainly complexed with dissolved humic sum stances)
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From page 159... ...
I ~ 7.0 8.0 5.0 6.0 pH . 5.0 6.0 7.0 8.0 pH FIGURE 8.12 Metals in 16 lakes on the Swedish west coast with similar metal deposition but with different pH, December 1978.
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From page 160... ...
Ct UJ ~ _ J ~ 40— LU ~ 30— _~Q (CH3) 2 Hg \ A 1 1 — 5 6 7 8 9 10 pH FIGURE 8.13 Formation of mono- and dimethyl mercury in organic sediments at different pH levels during 2 weeks, with a total mercury concentration of 100 ppm in sum strafe.
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From page 161... ...
While theory predicts that acidification should negatively affect microbial denitrification, ammonification, and Vitrification, as observed in terrestrial ecosystems, no evidence on these effects is currently available. Silica has been thought to be unaffected over a pH range of 2 to 8 (Birkeland 1974, Driscoll 1980~.
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From page 162... ...
162 1.50 1.00 0.50 _ @ @ 1 it 7.0 4.0 4.5 5.0 55 pH 6.0 6.5 FIGURE 8.14 Concentration of silicon in relation to pH level in 20 Swedish west coast leek August 1978. SOURCE: Dickson (1980t
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From page 163... ...
163 15 oh LL aid 1 0 In LL o LL 1 l i No Species ./ Present / All Species Present (snails, mussels, crustaceans)
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From page 164... ...
The effects of heavy metals are negligible at such high pH values, and thus the direct toxicity of hydrogen ion is implicated. Fish have been more extensively studied than other aquatic organisms in acidified lakes.
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From page 166... ...
166 SPECIES YELLOW PERCH PUMPKINSEED ROCK BPiSS WHIT E SUCK ER NORTHERN PIKE LAKE HERRING BLUEG ILL LAKE WHITEFISH SMALLMOUTH BASS LARGEMOUTH BASS LAKE TROUT BROWN BULLHEAD GOLDEN SHINER IOWA DARTER JOHNNY DARTER COMMON SHINER BLUNTNOSE MINNOW pH NUMBER of LAKES 4.0 4.5 5.0 5 5 6.0 6S 7.0 11 19 13 8 10 0 OCCURRENCE _ 40 37 29 25 20 23 6 6 19 7 9 7 10 20 1 1 6 9 populations appear unaffected populations showing stress, or are very small lowest pH recorded for the species FIGURE 8.17 Occurrence of fish species in six or more La Cloche lakes, in relation to pH. SOURCE: Harvey (1980)
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From page 167... ...
(1980) found that simulated rain at pH 4 and below the caused number of seed pods per plant to be reduced and thus the seed mass of soybeans produced was significantly decreased.
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From page 168... ...
3.0 Reduced growth (wt.) 3.0 Reduced yield and cabbage, quality 3.0, 4.0 and pepper Reduced growth and yield 3.0 Corvallis 5 of 35a Foliar symptoms 4.0 Environmental 28 of 35a Foliar symptoms 3.5 Research 31 of 35a Foliar symptoms 3.0 Laboratory 5 of 28a Decreased yield 3.0, 3.5, 4.0 6 of 28a Increased yield 3.0, 3.5, 4.0 Oak Ridge National Red kidney Foliar symptoms 3.2 Laboratory bean Reduced growth 3.2, 4.0 aNumber of species exhibiting effect out of total number exposed.
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From page 169... ...
North Carolina State University (rain and simulated rain) Tomato, pepper, snapbean, cucumber Soybean, "Davis" Soybean "Wells" No effect on seed mass Increase in seed size No foliar symptoms or 3.1 effects on growth Soybean, Decreased growth, yield, and seed quality (germination)
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From page 170... ...
However, at low acid-rain input, the metal output is substantially in excess of the retention of hydrogen ions, because where rain is not strongly acid, natural inputs of hydrogen ions from such processes as decomposition and root respiration are of relatively greater importance than anthropogenic inputs ~n mobilizing metals. Chelation may also be significant where the effects of acid rain are not predominant (see references cited by Gorham et al.
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From page 171... ...
~ ~ ' \ ~ Qua ~ i of ~ o ht \ hi_ it,, fib ~ C'0 / \ ~$ 171 ~5~ i;~ a\ he\ J O ~ b fib god\ I
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From page 172... ...
Such coarse soils are moderately to highly saturated by "basic" cations such as Ca++, Mg++, K+, and Na+, which are leached away as they are replaced by "acid" cations such as hydrogen ions, aluminum ions, and hydroxy-aluminum ions. As the exchange complex becomes dominated increasingly by the "acid" cations, the pH of the soil declines.
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From page 173... ...
, in which purely organic mor humus layers (Romell 1932, 1935, Lutz and Chandler 1946) from Swedish spruce forests were leached in the laboratory by simulated rain acidified to 5 different pH levels.
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From page 174... ...
174 pH 2 1400 800700 600 N ~ 500 a) 400 300 200100 O-100 ~ pH4 oH 3 control, not watered Ca Mg K I: K,Mg,Ca ~ _ ~ .
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From page 175... ...
175 35So2- S adsorbed 3 0 25 50 75 100 125 1 1 1 1 ' 1 E ~ P Bsl Bs2 Bc .
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From page 176... ...
Elucidation of the influence of acid precipitation upon the release of polyvalent metals from mineral soils will be greatly complicated by the fact that organic acids and polyphenols produced by organisms are also of much importance in the mobilization of oxides of aluminum, iron, and manganese from soils, and breakdown of these oxides will release the many trace metals adsorbed by them (several references in Russell 1973~. Presumably acid rain -- with its strong mineral acids -- will have some effect upon the weathering action of the organic acids and polyphenols, the latter being known to reduce iron more strongly in acid than in neutral conditions (Russell 1973~.
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From page 177... ...
Left-hand graphs represent unpolluted humus layers; righthand graph represents humus layers polluted from a brass mill.
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From page 178... ...
I78 00 50 40 30 20 10 o V= 12.Sx-47.2 r= 0.~ , i./ 3 4 @ e 6 7 pH FIGURE 8.22 CoIIelation Bitten denitdOcation Ivies and sod pH.
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From page 179... ...
As time goes on and upland soils become more acid, they also become less susceptible to further acidification by acid rain, because exchange sites within the soil are already highly saturated by hydrogen ions. In this situation, substantial amounts of acid will percolate to the receiving waters of streams and lakes, which consequently undergo a pronounced decline in pH.
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From page 180... ...
Near Sheffield in the southern Pennines the pH of bog pools was only 3.25, and the concentration of SO4 reached 46 mg/1. Although it is impossible to ascribe with certainty the disappearance of the bog moss from the southern Pennines to acid precipitation, recent experiments with the same Sphagnum species indicate that either acid rain or SO2 fumigation alone have detrimental effects consistent with the observed disappearance (Ferguson, Lee, and Bell 1978~.
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From page 181... ...
and the mechanisms by which acid deposition alters ecosystem function. Some of these studies could be conducted on watersheds exposed to ambient levels of acid rain, while other studies, in relatively unpolluted areas, could subject whole ecosystems to experimental acidification.
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From page 182... ...
Many of the objections to liming will also apply to nutrient additions. SUMMARY Acid deposition, due to the further oxidation of sulfur and nitrogen oxides released to the atmosphere by anthropogenic sources, is causing widespread damage to aquatic ecosystems, including loss of bicarbonate, increased acidity, and higher concentrations of toxic metals.
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