Sensitivity to acidification

Zobrist, J., and J. I. Drever (1990), "Weathering Processes in Alpine Watersheds Sensitive to Acidification", in M. Johannessen, R. Mosello, and H. Barth, Eds., Air Pollution Research Report 20 "Acidification Processes in Remote Mountain Lake", CEC, Brussels, 149-161. 

At present two of 20 studied high Alpine lakes are still acid (Aik <0 meq P ), 13 are sensitive to acidification (0 acid sensitive (0.05 meq 1 < AUc <0.2 meq 1 ). In the 1980s the number of acid, acid sensitive, and not acid sensitive lakes was 4, 14 and 2, respectively. Because of the increase in aluminium dissolution a pH decrease below 6 can become critical for the biology of lakes. Today only three lakes from 20 have an average pH below 6. In the 1980s there were seven. 

Acid rain primarily affects sensitive bodies of water, that is, those that rest atop soil with a limited ability to neutralize acidic compounds (called buffering capacity ). Many lakes and streams examined in a National Surface Water Survey (NSWS) suffer from chronic acidity, a condition m which water lias a constant low (acidic) pH level. The survey investigated tlie effects of acidic deposition in over 1,000 lakes larger than 10 acres and in thousands of miles of streams believed to be sensitive to acidification. Of the lakes and streams surveyed in the NSWS, arid rain has been determined to cause acidity in 75 percent of the acidic lakes and about 50 percent of tlie acidic streams. Several regions in the U.S. were identified as containing many of the surface waters sensitive to acidification. They include, but are not limited to, the Adirondacks. the mid-Appalachian highlands, the upper Midwest, and the high elevation West. 

Fig. 5.7 Rates of acid deposition (contours of imol H+1 ) and areas most sensitive to acidification (shaded) based on their rock type (a) Europe, (b) North America. Modified from Likens et at. (1979), with kind permission of A.M. Tomko IIL...

Baker In the DRG, one mode shifter appeared to be change in pH, in as much as late current is very sensitive to acidification (Baker Bostock 1999). If you acidify, the late currents disappear. In part, this seems to be due a change in gating rather than just simply proton block. I would suggest that pH is one way in which gating mode can be modulated. 

Working groups under the MOI picked up where the BRCG had left off, and eventually produced reports (United States-Canada 1983). The MOI, however, ultimately proved not to be the kick-start to the negotiation process that Ottawa, at least, had intended it to be. In early 1982 Canada proposed formally that SO2 emissions be reduced by 50% in both countries. This target was designed to achieve a level of deposition of no more than 20 kg of wet sulphate per hectare per year in areas sensitive to acidification. The United States rejected the proposal, firmly. The Reagan administration made clear its conviction that action was premature and, for the rest of the decade, consistently took the position that more research had to be done on the problem of acid rain before control actions could be considered. 

The calcium/aluminium ratios that are especially sensitive to acidification in the root substrate and should be reduced by acidification, have not fallen. Also, in the experiments referred to with pines, the aluminium and manganese contents of the needles did not increase between 1969 and 1979. Ulrich found that in his experimental areas, in Southern Germany where fir deaths occurred, aluminium concentrations in the soil leachate were 2-5 mg/1. The extent of the damage has not yet been correlated with these aluminium values. In fact, under a healthy stand of firs, similar alximinixim concentrations in the soil leachate of 2-4 mg/1 would be expected."... 

ERA in general is a process, as is EIA (Environmental Impact Assessment), and not the occasional report or document that is published at various steps. The framework for the orderly process, which has been developed for various environmentally sound projects can be applied also for acidification oriented projects and especially for an evaluation of ecosystem sensitivity to acid deposition and critical load calculations. Central management of the process is an essential feature. 

The Critical concentrations with respect to the soil organisms should be related to a low effect level on the most sensitive species. The effects on the process of metabolism and other processes within the organisms should be considered and also the diversity of the species, which is most sensitive to the heavy metals, has to be accounted. Critical limits must refer to the chronic or accumulated effects. For assessment of the critical concentrations in crops and in drinking water, human-toxicological information is required. In general, for establishing critical loads we should also account the additive effects of the different metals and combination effect between the acidification and biogeochemical mobilization of the heavy metals in soils and bottom sediments. 

Sato, K., Wakamatsu, K., Takahashi, A. (1998). Changes in distribution of aluminum species in soil solution due to acidification // Bashkin, V. N., Park, Soon-Ung (Eds.). Acid Deposition and Ecosystem Sensitivity in East Asia. New York Nova Science Publishers, Ltd., pp. 125-142. 

Equation (4.36) shows that two H+ ions are produced for each mole of Fe + oxidized, i.e. the reaction is accompanied by acidification. In aqueous solution, the rate is found to be very sensitive to pH and at near neutral pH the reaction is accelerated 100-fold if the pH is raised by one unit. The following empirical rate law applies in the pH range 5-8 (Stumm and Lee, 1961 Wehrli, 1990)... 

The yellow solution of chromate salt on acidification turns orange due to formation of dichromate ion. Both the ions are in equilibrium, sensitive to pH change ... 

Ammonium nitrite is explosive and very sensitive to heating. Explosive decomposition can occur even when an aqueous solution is heated to 60-70°C. Acidification of an aqueous solution with a drop of concentrated hydrochloric, sulphuric or nitric acid produces a spontaneous decomposition even at room temperature. 

The acidification problem in both the United States and Canada grows in magnitude if episodic acidification (brief periods of low pH levels from snowmelt or heavy downpours) is taken into account. Lakes and streams throughout the United States, including high-elevation western lakes, are sensitive to episodic acidification. In the Mid-Appalachians, the Mid-Atlantic Coastal Plain, and the Adirondack Mountains, many additional lakes and streams become temporarily acidic during storms and snowmelt. Episodic acidification can cause large-scale fish kills. ... 

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