| Popis: |
Snowmelt collected from snow cores taken from the 1982 spring snowpack in the Wasatch Mountains of northern Utah lacked mineral acidity and retained enough buffering capacity in the form of calcium and magnesium bicarbonates to titrate additional inputs of strong acid equivalent to the amount apparently already neutralized. While acid anion concentrations were higher than those found in pristine areas, they were much lower than those reported for winter precipitation in other western areas experiencing acidification of precipitation. Snowmelt pH ranged from 5.62 to 6.88 (mean = 6.17), and sulfate was relatively more important than nitrate, showing an average equivalent ratio of 3.1:1. Patterns of pH indicated decreasing pH with distance from sources of soil-derived buffering capacity in the semiarid valleys to the east. Although acid anion concentration patterns failed to point to pollution sources along the Wasatch Front, chloride concentration patterns indicated that the Salt Lake Valley airshed influenced snow chemistry in the mountains. Snowmelt studies carried on in the laboratory and at a field site in Logan Canyon indicated that, for the alkaline snow typical of 1982, the first melt fractions had a higher pH (less acidity) than did the bulk snow. The opposite situation is typically found for acid snow. Although no acidity was present, snow pH increased by 13 percent as a result of contact with organic litter on the soil surface of a 22 m, 32 percent slope. The pH increased even more rapidly in a nearby intermittent stream 9to 7.78 at the edge of the snowpack). Difficulties in interpreting the data from the snow cores in this study include the effects of an unusually wet winter, uncharacteristically low levels of industrial activity due to economic factors, uncertainty about the relative amounts of acidity and buffering capacity reaching the sensitive Uintah Mountain watersheds to the east, and failure to distinguish between soil and acid derived sulfates. Analysis of these difficulties suggests taht offsetting factors would tend to cancel effects of precipitation amount during wet-to-normal winters. the remaining factors require additional research. |
