Rainfall Rainwater

Biological acid production (bicarbonate leaching) Excess base uptake by roots =1.1 Acid rainfall (rainwater pH = 4.3-4.4) = 0.67 KCl-exchangeable acidity = 100-275 Total titratable acidity = 500-800... 

A critical situation arises in summer when the tank is heated by strong radiation, then cooled by sudden rainfall. Heavy rainfall results in a rapid drop in ambient temperature and the formation of a rainwater nlm that flows on the top of the tank and down the tank wall. The wall and, with a certain lag, the gas in the tank are cooled, and air must flow into the tank to prevent a significant pressure difference from arising between the inside and outside of the tank. If vapors in the tank are condensed, more air must flow into the tank. 

Consider a lake with a smaU watershed in a forest ecosystem. The forest and vegetation can be considered as an acid concentrator. SO2, NO2, and acid aerosol are deposited on vegetation surfaces during dry periods and rainfalls they are washed to the soil floor by low-pH rainwater. Much of the acidity is neutralized by dissolving and mobilizing minerals in the soil. Aluminum, calcium, magnesium, sodium, and potassium are leached from the soil into surface waters. The ability of soils to tolerate acidic deposition is very dependent on the alkalinity of the soil. The soil structure in the... 

What would be the approximate sulfate concentration of rainwater globally for the following cases (assume that rainfall is uniformly 75 cm/yr) ... 

A worst-case scenario for delivery of pollutant to the Mississippi River would entail the assumptions that (1) The rainfall on all lagoons becomes saturated with the contaminant (2) all contaminated rainwater reaches the river, and (3) characteristic river flow is at an historic low. 

Atmospheric deposition is an important source of mercury for surface waters and terrestrial environments that can be categorized into two different types, wet and dry depositions. Wet deposition during rainfall is the primary mechanism by which mercury is transported from the atmosphere to surface waters and land. Whereas the predominant form of Hg in the atmosphere is Hg° (>95%), is oxidized in the upper atmosphere to water-soluble ionic mercury, which is returned to the earth s surface in rainwater. In addition to wet deposition of Hg in precipitation, there can also be dry deposition of Hg°, particulate (HgP), and reactive gaseous mercury (RGM) to watersheds [9-11]. In fact, about 90% of the total Hg input to the aquatic environment is recycled to the atmosphere and less than 10% reaches the sediments [12]. By current consensus, it is generally accepted that sulfate-reducing bacteria (SRB)... 

The boundaries of surface runoff-producing areas will be dynamic both in and between rainfalls. During a rainfall, area boundaries will migrate upslope as rainwater input increases. In dry summer months, the runoff-producing area will be closer to the stream than during wetter winter months, when the boundaries expand away from the stream channel. 

SIMCA modeling was utilized to determine the separability of the samples collected at the three different sites. The results presented In Table IV Indicate the model cannot separate the samples from the West Seattle and Maple Leaf sites. Since both of these sites are located downwind of the major regional emission sources and experience similar meteorology their rainwater composition Is similar. The Tolt reservoir site Is separated from the Seattle sites with 79 percent of the samples collected there correctly classified by the SIMCA model. This site Is believed to be Influenced by the same emission sources as the other two sites but experiences different meteorological conditions (primarily longer transport times and more frequent and larger quantity of rainfall) due to Its location In the foothills of the Cascade Mountains (elevation 550 meters). Considering the uncertainty In the reported concentrations (see Table VII) and the similar air pollution emission sources the SIMCA results are reasonable. 

Because of the increasing contamination of the atmosphere by organic pollutants, there is also a growing concern about the quality of rainwater. In this context, it is interesting to know how well a given compound is scavenged from the atmosphere by rainfall. Although for a quantitative description of this process, more sophisticated models are required, some simple equilibrium calculations are quite helpful. 

Four replicate columns were run, and all produced the same type of elution curve. Lyophilized samples of another aliquot of the same soil used in the columns yielded soil water with a tritium concentration the same as that in the first aliquot drawn from the column. The first aliquot was equivalent to 1 inch of rain on the column and represents about one-third of the free water in the original soil material in the column. Zimmerman (13) reported a similar phenomenon when he used tritiated water to trace pulses of rainwater in soil systems. He found a relatively discrete front associated with the tritium injection after rainfall had occurred and eluted the tritium pulse into the soil profile. The frontal movement of high specific activity tritiated water from the surface layers in ejecta strata Sedan accounts for the peak tritium concentrations observed at depths just below the maximum penetration of rainfall. 

If the above explanation is correct, the rainwater disintegration rates of other airborne radionuclides should also decrease with increasing rainfall rate. However, the atmospheric activities of the longer lived radionuclides change with time, making it difficult to compare the activities in different rainwater samples. The 7Be activity in rainwater ap-... 

Watering the two tanks was made by rainwater, but required the addition of tap water to satisfy expected L/S ratios. Based on a 4-month time period for experiments, additional inflow of water was calculated according to the total volume required and on average rainfall normally associated over this period. Total water addition was meant to produce 2 m3 of percolates per ton of dry BA and 7.5 m3 of percolates per ton of dry 2SL. On the whole, three P fractions were recovered from each rack in situ and were analyzed for pH and conductivity before being sent to the laboratory. These P fractions were defined as follows ... 

The effects of anthropogenic sulfur dioxide on the remote marine atmosphere may be evident from rainwater studies by Chukhrov et al. (60) in which the isotopic composition of sulfur in rain was studied systematically at great distances from the continent. Rainwater sulfate ranged from +12.1 to +15.0 0/00 over the Atlantic and from +9.5 to +16.2 0/00 over the Pacific, with a one month average value of +13.3 0/00 for the two oceans. Their study included measurements of rainwater sulfate from a wide variety of continental areas and found that most inland 634S values were significantly lower than those over the oceans. The oceanic rainfall sulfate was most likely a mixture of the isotopically lower continental sulfate and the more enriched marine sulfate. 

The rainwater of Bermuda is in near equilibrium with atmospheric Pc02 = 10-3.5 atm., and contains small amounts of sea salt (0.07 wt. % seawater). The rainfall of 147 cm y1 is seasonally distributed. The rain enters the saturated zone by two main paths direct rainfall on marshes and ponds, and percolation downward from the vadose zone as vadose seepage and flow through rocks during times of soil water excess (Vacher, 1978). Total annual recharge of the saturated zone is about 40 cm y-1 (Vacher and Ayers, 1980). The residence time of the groundwater has been calculated as 6.5 years, and the average age of the sampled water as 4 years (Vacher et al., 1989). Such estimates are necessary for calculations of carbonate mineral stabilization rates, as shown in a later section. 

Acid rain was at one time an important point of contention between the United States and Canada. Much of this acid was the result of the emission of sulfur oxides by coal-fired electricity generating plants in southern Indiana and Ohio. These sulfur oxides, when dissolved in rainwater, formed sulfuric acid and hence acid rain. How many metric tonnes of Indiana coal, which averages 3.5% sulfur by weight, would yield the H2S04 required to produce a 0.9 in. rainfall of pH 3.90 precipitation over a 104 mile2 area ... 

Total organic chlorine in the rainwater was 0.3 p.p.b., with atrazine and the 2,4-D ester amounting to about 0.1 p.p.b. each. Since the soil one mile away contained 6 p.p.m. of atrazine, it can be calculated that no more than 16-17 mg. of soil per liter of rainfall would be sufficient to yield the 0.1 p.p.b. of atrazine actually found in the rain, and 16 to 17 mg. of suspended solids in a rain sample is not unusual. 

Their data suggest, however, that pesticide-laden dust in the atmosphere also must have been precipitated to earth by sedimentation and by rainfall. The average concentration found in the rainwater samples collected by exposing a sample collector for 1 month during the period November 1964 to February 1965 was for y-BHC 100, for dieldrin 20, and for p, p -DDT 3 parts per 1012 parts of rainwater (parts per trillion), whereas the samples collected only during periods of rainfall in January and March of 1965 averaged 29, 9, and 3 parts per 1012 parts of rainwater, respectively. 

Rainwater is the consequence of several steps in the water cycle brought about by evaporation, condensation, and precipitation. The water in the atmosphere has a residence time of approximately 8-9.6 days before precipitating as rainfall. As mentioned above, in this cycling the global volume of precipitation that falls onto the Earth each year is of the order of 5.8 x 105 km3, from which approximately 21% falls onto the land and about 79% onto the sea (see Figure 6.2). 

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