Boxes rainwater

Diked or Unitized Secondary Containment. Small tanks can have a secondary-containment dam built integrally into the tank. This is essentially within a steel box. These tanks may be either vertically or horizontally oriented in both cylindrical and rectangular shapes. The secondary-containment dikes may be open or closed. Closing the dikes makes access to the primary-containment tank more difficult, but keeps out rainwater. 

The bulk properties of a polymer ean often be altered considerably by the incorporation of additives. Probably the most well-known examples of this occur in rubber technology where variations in the choice of additives can produce such widely differing products as tyres, battery boxes, latex foam upholstery, elastic bands and erasers. It is also possible to achieve variations as extensive as this amongst plastics materials, in particular with PVC from which rigid rainwater piping, baby pants, conveyor belting, footballs and domestic insulating flex may all be prepared. 

Sometimes we need to know how the concentrations of the ions present in a solution of a polyprotic acid vary with pH. This information is particularly important in the study of natural waters, such as rivers and lakes (Box 10.1). For example, if we were examining carbonic acid in rainwater, then, at low pH (when hydronium ions are abundant), we would expect the fully protonated species (H2C03) to be dominant at high pH (when hydroxide ions are abundant), we expect the fully deprotonated species (C032 ) to be dominant at intermediate pH, we expect the intermediate species (HC03, in this case) to be dominant (Fig. 10.20). We can verify these expectations quantitatively. 

Rainwater is naturally slightly acidic due to the dissolved carbon dioxide. Acid rain results when acidic sulfur and nitrogen oxides produced during the combustion of coal and oil react with rainwater (see Box 10.1). 

Nesting box bark mulch rain barrel to collect and recycle rainwater. 

From a shop-fabricated tank manufacturer s perspective, a diked AST generally refers to a steel tank within a factory-fabricated steel box, or dike. An example of a diked AST is the STl F911 standard, providing an open-topped steel rectangular dike and floor as support and secondary containment of a UL 142 steel tank. The dike will contain 110 percent of the tank capacity as rainwater may already have collected in the dike, the additional 10 percent acts as freeboard should a catastrophic failure dump a full tank s contents into a dike. Many fabricators offer steel dikes with rain shields to prevent precipitation from collecting. 

Box 15-1 Systematic Error in Rainwater pH Measurement The Effect of Junction Potential... 

Hydrogen peroxide (H202) and 03 are the natural strong oxidants present in rainwater. These oxidants can potentially oxidize nearly all the S02 in a parcel of air. Box 3.8 shows that under such conditions rainfall may well have pH values lower than 3. This illustrates the high acid concentrations possible in the atmosphere as trace pollutants are transferred from the gas phase to droplets. Liquid water in the atmosphere has a volume about a million times smaller than the gas phase thus a substantial increase in concentration results from dissolution. 

In Box 3.4 we saw the way reactions affect the solubility of gases. It is possible for some gases to undergo more complex hydration reactions in water, which influence its pH (see Box 3.5). The best known of these is the dissolution of carbon dioxide (C02), which gives natural rainwater its characteristic pH. 

Continental water contains dissolved species that render it acidic. The acidity comes from a variety of sources from the dissociation of atmospheric C02 in rainwater—and particularly from dissociation of soil-zone C02 (Section 4.4.2)— to form H2C(and natural and anthropogenic sulphur dioxide (S02) to form H2S03 and H2S04 (see Boxes 3.7 3.8). Reaction between a mineral and acidic weathering agents is usually called acid hydrolysis. The weathering of CaCO, demonstrates the chemical principle involved ... 

The smaller Cw values are also connected with water deficiency in Steppe and Desert ecosystems. However, the concentration of various chemical species in rainwater of background regions is higher that that in the Forest ecosystem belt. The major reason is the wind deflation of the soil s surface owing to lack of tree species and only a lean protective layer of grasses and half-shrubs. A large mass of soil particles becomes entrained into the air migration. The most characteristic example is connected with the Yellow sand phenomenon (see Box 7). 

The owner (Milwaukee, WI) built an elevated—about 5 ft high—composite deck completely enclosed with the same composite boards, thereby creating a box perfectly insulated from any air movement. There were no windows in the box. The top of the box, that is, the deck itself, was pretty warm on a warm day, and rainwaters dripping into the box created a warm and very humid environment. The ceiling of the box, that is, the bottom side of the deck, was warm to touch from the inside of the box. After several months, the owner noticed small dark spots on the ceiling of the box, when she looked from the inside of her house through a small door, normally closed. There were no spots on the sidewalls of the box. 

Junction potential. A junction potential exists at the porous plug near the bottom of the electrode in Figure 15-7. If the ionic composition of analyte is different from that of the standard buffer, the junction potential will change even if the pH of the two solutions is the same. This factor gives an uncertainty of at least 0.01 pH unit. Box 15-1 describes how junction potentials affect the measurement of the pH of rainwater. 

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