Acid Deposition Long-Term Trends (1986) / Chapter Skim
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7. Streams and Lakes
7. Streams and Lakes
Pages 231-299
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From page 231... ...
Johnson, Richard B Alexander, and Gary OehZert INTRODUCTION Various attempts have been made to assess changes in the acidity of surface waters that may have occurred over the past 50 years.
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From page 232... ...
Throughout much of the remainder of the country, SO2 emissions have increased and trends in stream sulfate, alkalinity and alkalinity/total cation ratios are consistent with a hypothesis of increased acid deposition. There are, however, several acknowledged problems in the interpretation of "historical n lake water chemistry
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From page 233... ...
Methyl orange, a commonly used indicator for measuring the alkalinities of lake waters in the 1930s, undergoes subtle color changes over a range of pH values, and the exact endpoint used by analysts is often not clearly specified in the historical records. In this chapter, we review some of these records and assess trends based on the most likely endpoints employed in the historical studies.
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From page 234... ...
show a similar relationship in eastern Canada. To link sulfate ion concentration in atmospheric deposition to the sulfate ion concentration of surface waters, a direct relationship must exist between atmospheric and lake sulfate fluxes for a steady state assumption.
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From page 235... ...
The study of sulfate-driven changes in surface water chemistry is accomplished with the aid of a general paradigm that links acidic deposition to changes in the water quality in watersheds with acidic soil. Finally, we compare pH and alkalinity data of lakes taken at discrete time intervals, i.e., from the 1920s and 1930s to the 1970s and l980s.
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From page 236... ...
sulfate in wet precipitation. In our analysis, we compare sulfate input fluxes in wet deposition with the estimated sulfate output fluxes from 626 lakes in New York, New England, Quebec, Labrador, and Newfoundland.
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The apparent lake sulfate output flux normalized to the wet-only precipitation sulfate input flux is analyzed by geographic region in Table 7.1. Deficiencies in lake sulfate outputs compared with inputs from wet-only deposition Generally occur in remote regions such as Newfoundland and Labrador, whereas excesses occur in more populated areas such as New York, Connecticut, and Massachusetts.
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9 m~2 yr 1 FIGURE 7.1 (a) Comparison of sulfate input fluxes to lakes from wet-only deposition with sulfate output fluxes from lakes in the northeastern United States and eastern Canada.
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of sulfate fluxes to lakes from wet-only deposition with the logarithm (base e) of sulfate fluxes from lakes in the northeastern United States and eastern Canada.
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The multipliers mi' are regionally specific. Thus lake sulfate output flux y is estimated to be a multiple of precipitation sulfate input flux x.
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FIGURE 7.3 Regional relationships between inputs and outputs of sulfate for lakes in northeastern North America assuming that the only source of sulfate input is from wet deposition. volcanics, and basalts are associated with sulfide minerals, it is quite possible that the excess sulfur in lakes with these associations are due to contributions from sulfide minerals.
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From page 243... ...
in the system of interest and especially in the pH range of interest. The proton condition is the ion balance condition for protolytes (e.g., Stumm and Morgan 1981, pp.
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From page 244... ...
2. Sulfate concentrations in surface waters increase 3.
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. Acidification of the upper soil horizons does not necessarily translate into acidified surface waters because a mobile anion is needed to transport the protolytes.
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From page 246... ...
The overall result of soil acidification from natural biogenic processes is that the soil solution becomes more acidic with lower concentrations of nonprotolytic cations. As a first approximation, alkalinity trends in surface waters can be due to changes in strong-acid anion flux plus changes in internal processes in accordance with Eq.
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From page 247... ...
In strongly acid forest soils, the annual ionic input is generally a very small fraction of the exchangeable pool, so the effect of atmospheric deposition in changing bulk soil chemistry would likely be slowly realized in most cases in the United States. In summary, the pathways by which changes in surface water alkalinity may occur are through changes in the deposition of mobile anions and, under appropriate hydrologic conditions, changes in soil acidity, which can be natural or promoted by acidic deposition.
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From page 248... ...
may have introduced some bias into the analysis, we do not believe that this limitation is serious. Sulfate output from the Bench Mark wafer sheds was estimated as the product of discharge-weighted mean sulfate concentrations and mean basin runoff for the 2-year period from 1980 and 1981.
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From page 249... ...
249 Input from Atmosphere (wet + dry deposition) Reduction to H2S < Output to Surface Waters 4 Above-ground Biomass =, 14 ,, 1 Dry deposition washoff, sulfate leaching from foliage = Inorganic S Soil Solution = Organic S Geochem ice I Sulfur (Subsoil/Geological substrate)
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From page 250... ...
. As a result, any explanation of the cause of trends in stream sulfate is subject to uncertainty since trends in internal sources and sinks as well as trends in atmospheric deposition may contribute to trends in surface water SOi~.
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Ratios of sulfate input to output at the western sites are variable, and they are difficult to account for in many cases given the information available on geological and soil characteristics. Trends in Stream-Water Sulfate in Bench-Mark Streams Figure 7.6 shows trends in stream sulfate concentrations over the periods of record for the watersheds that were judged not to have dominating internal S sources.
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From page 252... ...
By contrast, stations in the northeastern quarter of the nation show either no trend or decreases in sulfate concentrations during the same period. This geographical pattern of trends occurs more or less independently of the significance criteria used in trend testing (Smith and Alexander 1983)
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Thus, surface waters are expected to respond to increasing sulfate flux by both reduction of alkalinity and increases in non
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From page 254... ...
Nitrate is also a strong acid anion added from the atmosphere, and, although NO3 is apt to be strongly retained in the terrestrial ecosystem by plants and soil organisms in most cases, changes in NO3 concentrations in surface waters must be considered along with sulfate changes in interpreting alkalinity changes. For cases in which changes in strong-acid anion flux drive changes in stream chemistry, the relationship between changes in strcng-acid anions, alkalinity, and cation concentrations given in Eq.
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From page 255... ...
Their values will differ from one geochemical setting to another and provide a measure of the ability of a basin to accommodate short-term changes in sulfate flux by supplying base cations. Estimates of the derivatives for Bench-Mark stations were obtained from linear regressions of major cation concentrations and alkalinity on sulfate plus nitrate concentration.
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From page 256... ...
·SC DISC WASHe NY · · OR PA- · WYO _ . _ -1 .0 / 0.0 0.2 · NC LA:/ ·MS 0.4 0.6 0.8 1.0 d ~ BASE CATIONS/d ~ ACID ANIONS FIGURE 7.8 Plot of rate of change in base cation concentrations versus rate of change in alkalinity per unit change in acid anion concentration for stations with mean alkalinities less than 500 peq/L.
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From page 257... ...
257 o .= ._ ._ u, ct ._ —a.
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From page 258... ...
Figure 7.10(a) chows trend slopes for alkalinity minus base cations plotted against trend slopes in sulfate plus nitrate for the 12 stations that display charge balance (Eq.
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From page 259... ...
FIGURE 7.10 (a) Trend in alkalinity minus trend in base cations versus trends in sulfate plus nitrate.
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From page 260... ...
On the other hand, increasing alkalinity in streams of the Northeast can be accounted for almost entirely by the reduction in sulfate deposition within the error constraints of the analysiS. PROTOLYTIC CHEMISTRY OF SURFACE WATERS OF NEW HAMPSHIRE, NEW YORK, AND WISCONSIN Extensive sets of historical and recent data exist for lakes in New Hampshire, New York, and Wisconsin from which conclusions may be drawn regarding changes in the acidic status of poorly buffered lakes.
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From page 261... ...
. The exact values of pH at which the color changes appear, as well as which color changes were used in particular circumstances, are not always evident (vice infra)
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. The correction, simply made as the difference between the hydrogen-ion concentration at the indicator endpoint (about 10 4 N)
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From page 263... ...
The true endpoint values of pH for [Alk ]
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repeated the MO titration on a low-alkalinity sample; independent technicians following the Standard Methods (1933) procedure with the "faintest pink n directive found the pH for the color change to be 4.04.
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From page 265... ...
E Towne, New Hampshire Water Supply and Pollution Control Commission, personal communication, 1983)
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From page 266... ...
x of 10 4 04 and 10-4-19 peq/L. It is possible that the pH of color change may lie outside this range for specific cases owing to differences in human perception of the color change as well as other factors, such as analytical set-up, sample color interference, and the overall lack of sensitivity of the method.
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From page 267... ...
by difference. Colorimetric pH must also be corrected because the pH indicator dyes are weak acids and bases and alter the actual pH of a poorly buffered solution.
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From page 268... ...
fundamental principles of ion balance are applied to a carbonate ion system in order to derive definitions of alkalinity and acidity; these concepts are also used to reevaluate data titrated to the uncorrected endpoint as well as to adjust calorimetric pH data.
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From page 269... ...
1930, 1940-50 N.H. 1970s Wisconsin 1925-41 Wisconsin 1980 Surface Profile Profile Surface Profile Surface 269 TABLE 7.4 Analytical Aspects of Lakes Data from New York, New Hampshire and Wisconsin Data Set Type of Sample N.Y.
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From page 270... ...
are met. The recent alkalinity data for New York and Wisconsin were not adjusted since the Gran method was used.
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From page 271... ...
In choosing the three data bases described here the primary consideration was the existence of data on pH, alkalinity, and free Cod acidity and detailed records of sampling and anaylsis that allowed us to check the internal consistency of the data and to evaluate their quality. Another important consideration, to which we have paid less attention, is representativeness, i.e., the degree to which the chosen lakes in a given region reflect the characteristics (morphology, water quality, history of land use in the watershed, etc.)
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From page 272... ...
Table 7.5 gives the results for the replication studies using New Hampshire data. The column headed MO refers to the average variations in alkalinity determined by MO titration.
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From page 273... ...
273 TABLE 7.5 Vanation in Replicate Samples from Historic New Hampshire Lake Surveys Sample Sample Alkalinity (,u~eq/L) by Size MO pHc/CO2 Acidity Depth replicate Duplicate profile averages, same date 10 10 21 14 53 Duplicate profile averages, 21 67 different date 10 91 92 70 NOTE: Results are shown for different groupings.
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ThuS the same criterion of 50 peq/L was used for Wisconsin data. There were no replication studies available for historical New York lakes data.
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From page 276... ...
Recent data for New Hampshire, New York, and Wisconsin could not be screened for consistency because of the lack of replicate data or redundant protolyte measurements. The New Hampshire alkalinity data were adjusted for a fixed pH endpoint of 4.5, as discussed earlier.
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. Since the latter two studies refer specifically to the Wisconsin data set, we assumed that the pa of 4.19 was the best estimate to use in the compilation of historical values of pH and alkalinity in Wisconsin lakes.
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From page 278... ...
by the choice of the recent data set. When an endpoint pH of 4.04 is assumed and the historical data are compared with the 1984 data set, the median value for the change in alkalinity is +1 peq/L, and the median value for the change in pH is -0.12 unit.
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From page 279... ...
, regardless of the choice of recent data set. To test whether liming activities may have biased our results, we examined the liming histories of New York lakes (data were provided through the courtesy of F
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From page 280... ...
Employing a nonparametric chi-square statistical test, we concluded that there is no evidence of such bias. The major effect of using consistent data only is demonstrated for alkalinity changes in New York lakes, assuming an MO endpoint value of 4.19 (see Figure 7.15)
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109 ~ ,~ 90% I I (,ueq/L) -600 -400 -200 0 +200 +400 /\ ALK (recent alkalinity minus historical alkalinity)
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Average variation in the analyses of duplicate lake profiles collected at different times over short time periods (up to 2 years) was compared with variation in duplicate lake profiles collected on the same date.
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From page 283... ...
:-:.:: :::-.:: ::.: ::-:::::.::::::.:::::.::.:.:-:::::-: -.:-:: :-:::$-: :.:.:.:.:-:.: I ~ ~~ ~~ I (,ueq/L) So% -200 -100 0 +100 +200 ~ ALK (recent alkalinity minus historical alkalinity)
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From page 284... ...
50% = -69 peq/L +200 +400 n pH (MO) = 4.19 n= 248 all the data v v -600 -400 -200 0 +200 +400 /& ALK (recent alkalinity minus historical alkalinity)
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From page 285... ...
Valentine Pond (5-0370) Wisconsin: Dog Lake Goodyear Lake Virgin Lake Big Crooked Lake Booth Lake Cranberry Lake Diamond Lake Frank Lake Garth Lake Katherine Lake Little Arbor Vitae Lake Little Muskie Lake Little Portage Lake Mill Lake Silver Lake Spirit Lake Squash Lake Sumach Lake Yawley Lake + + + + + + + + + + + + + + NOTE: The magnitudes of changes are greater than 100,ueq/L for New Hampshire and Wisconsin and 200 ,ueq/L for New York.
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From page 286... ...
286 200 150 _ _ 100 ~ ~ 40 my 20 _ .~ -20 _ 1 1 1 · Beebe P n=6, O Bourne P n=7, · Branch P n=8, O Hardwood P n=6, · Kettle P n=7, ~ Osmore P n=5, * Stratton P n=7, ~ X Wheller P n=5, ~ \ \ 1/ 1 1 1 1 1 1 1 1 1 0~ in In/ \: ~ \ 01 03 1 1 1 05 07 09 11 07 09 11 1 982 1983 DATE (months)
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From page 287... ...
SUMMARY Relationship Between Sulfate Input Flux to Lakes from Wet Deposition and Sulfate Output Flux from Lakes In a large area of northeastern North America the mathematical relationship between fluxes of sulfate to lakes from wet deposition and fluxes of sulfate output from lakes is significantly linear when the data are examined on the basis of smaller contiguous regions (southern New England, New York, northern New England, Quebec, Newfoundland, and Labrador)
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From page 288... ...
This result supports the contention that changes in strong-acid anion fluxes affect surface water alkalinity in watersheds that have acid soils. Alkalinity and nonprotolytic cation changes in lowalkalinity Bench-Mark streams over the 15- to 20-year period of record are consistent with changes caused by a changing flux of strong-acid anions from the atmosphere, but there is also evidence suggesting that internal watershed processes or in-stream processes govern trends in nonprotolytic cations and alkalinity.
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From page 289... ...
, New York lakes, on average, appear to have increased substantially in acidic status over the past 50 years, as reflected in reductions in both alkalinity and pH. Alternatively, if a value of the pH endpoint close to 4.0 is assumed and if the historical data are compared with the 1984 data set, then there appears to have been little change, on average, in the acidic status of New York lakes over the past 50 years.
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From page 290... ...
1981. Acidification of surface waters in two areas of the eastern United States.
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From page 291... ...
1984. Predictive modeling of acidic deposition on surface waters.
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From page 292... ...
In The Acidic Deposition Phenomenon and Its Effects. Critical Assessment Review Papers.
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From page 293... ...
1982. Techniques of trend analysis for monthly water quality data.
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From page 294... ...
1972. Biological survey of the lakes and ponds in Coos Grafton and Car rol Counties.
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From page 295... ...
1932. Biological Survey of the Upper Hudson Watershed, Vol VII.
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From page 296... ...
1983. Atmospheric sulfur deposition, neutralization and ion leaching in two deciduous forest ecosystems.
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From page 297... ...
1982. Sulfate in lakes of eastern Canada: calculated atmospheric loads compared with measured wet deposition.
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From page 298... ...
1983. Past and present pH and alkalinity of New Hampshire lakes and ponds, New Hampshire Water Supply Pollution Control Commission, Concord.
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From page 299... ...
1976. Acid precipitation: changes in the chemical composition of lakes.
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