Organic rainwater

The pH of rainwater in equUibrium with atmospheric CO2 is 5.6, a value frequendy cited as the natural background pH. However, in the presence of other naturaUy occurring species such as SO2,, NH, organic acids, sea salt, and alkaline cmstal dust, the natural values of unpoUuted rainwater vary... 

In addition to the acid—base components shown in Figure 9, various organic acids are often found. Many of these acids are by-products of the atmospheric oxidation of organic matter released into the atmosphere. Of special interest are formic, acetic, oxaUc, and benzoic acids, which have been found in rainwater in concentrations occasionally exceeding a few micromoles per Hter. 

Methyl parathion has been released to the environment mainly as a result of its use as an insecticide on crops. It is applied to agricultural crops by aerial or ground spraying equipment. Methyl parathion has been detected in surface waters and sediments, rainwater, aquatic organisms, and food. There are no known natural sources of the compound. Methyl parathion has been identified in at least 16 of the 1,585 hazardous waste sites on the NPL (HazDat 2001). 

A variety of chemicals may be leached from the aerial portions of plants by rainwater or by fog-drip (16) including organic acids, sugars, amino acids, pectic substances, gibberellic acids, terpenoids, alkaloids, and phenolic compounds. Colton and Einhellig (17) suggested that leaf leachates of velvetleaf (Abutilon theophrasti) may be inhibitory to soybean (Glycine maxT We have recently discovered specialized hairs on the stems of velvetleaf plants which exude toxic chemicals. 

Kawamura K, Kaplan IR. 1983. Organic compounds in the rainwater of Los Angeles. Environ Sci Techno1 17 497-501. 

Rainwater Groundwater, lakes, rivers, seas, and oceans Carbon dioxide, nitrogen, oxygen, dust Sand (silica) and soil particles chlorides, bicarbonates, and sulfates, mainly of calcium, sodium, magnesium, and iron ions organic Air pollutants Rocks and soil, microorganisms, plant and animal... 

Sulfur Dioxide. Sulfur dioxide and nitrogen oxides, which are produced in modern society when coal, gas, and oil are burned in cars, power plants, and factories, react with water vapor in the air to form acids that negatively affect organic materials and even metals and stone when dissolved in airborne rainwater, the oxides of sulfur and nitrogen are the main cause of the formation of acid rain (see below). 

Rainwater recharges the top of the profile and reacted water drains from the bottom. We take discharge through the soil to be 4 m yr-1 and assume the dispersivity or (see Chapter 20) is 1 cm. The rainwater is dilute and in equilibrium with the CO2 fugacity of the atmosphere, 10-3 5. Within the soil, however, the soil gas is taken to contain additional CO2 as a result of the decay of organic matter, and root respiration. The pore fluid is assumed to maintain equilibrium with the soil gas and CO2 fugacity within the soil is held constant over the simulation, at 10-2. 

As regards the pollutants monitoring, from the measurements available so far it could be concluded that acid rain is coming to be a major problem in Asia. In many industrially developed and new developed countries such as Japan, China, Taiwan, South Korea, Thailand etc., values of pH <5 are encountered at many sites, and they represent more than 50% of monitored rain events on a regional scale. In some developing countries of South-East Asia (Myanmar, Laos, Cambodia) most rainwater pH measurements tend to be around 5.6, the pH of natural rainwater, and the acid rain precipitation is mainly due to localized industrial pollution. There is some evidence that pH values below 5 at unpolluted sites may be due to the contribution of weak organic acids, such as formic and acetic acids (Radojevic, 1998). 

The alkali in these water pools reacts with organic matter such as algae and moss growing on the stone. The most common of these reactions is saponification (see p. 240), which causes naturally occurring esters to split, to form the respective carboxylic acid and an alcohol. Once formed, this carboxylic acid reacts with more alkaline rainwater to form a metal carboxylate, according to... 

Case in which losses of organic compounds by rainwater elution, volatilization and degradation run in parallel with gains in organic contaminated levels in soil caused by sewage addition... 

If P% represents the annual loss of organic compounds caused by rainwater leaching etc. then... 

But Smith s research had relatively little impact on the scientihc community over the next seven decades. During this time, acid deposition continued to be of some minor interest to scientists in parts of Europe. For example, the Swedish biologist J. R. Erichsen-Jones reported in the late 1930s that acid from rainwater dissolved aluminum in soil and that that dissolved aluminum was toxic to certain types of aquatic organisms. 

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