United States soil orders

Why is this important It is important because it has a direct impact on the meaning of USDA certified organic foods. In order to receive a USDA certification as an organic food, the food producer must not have used pesticides for the previous three years. However, as evidenced by the food data collected by the FDA, banned pesticides persist in the soil to this very day. Furthermore, the vast majority (i.e., about 95 percent) of the food sold in the United States is grown and produced in the United States. This means that those foods found to contain banned pesticides had to come from farms in the United States. 

The radium-228 content of fly ash has varied from 1.8 to 3.1 pCi/g (0.07 to 0.12 Bq/g) (Eisenbud and Petrow 1964). If it is assumed that the total radium content of fly ash is 5 pCi/g (0.19 Bq/g), and that 1% of the ash generated at all coal-fired power plants in the United States escapes into the atmosphere, then an order-of-magnitude estimate of the amount of radium released each year would be 2.2 Ci (81,000,000 kBq) (Roy et al. 1981). Eisenbud and Petrow (1964) estimated that a single 1000-megawatt coal-fired power plant will discharge about 28 mCi (1,037,000 kBq) of total radium per year. Radium-226 has been detected in soils in industrial regions at levels up to 8.1 pCi/g (0.30 Bq/g) (Jaworowski and Gryzbowska 1977). 

Finally, because hyperaccumulators can accumulate relatively large quantities of heavy metals from the substrate, they could be used as decontaminating agents. A research group in the United States has already carried out trials with a Co hyperaccumulator in order to try to remove radioactive Co from contaminated soil. 

Strontium discharged into the atmosphere from the operation of coal fired power plants depends on the strontium concentration in coal, the amount of coal burned, and the efficiency of fly ash recovery. Approximately 90% of coal mass is consumed during the combustion process, leaving 10% as a residual nonvolatile material (fly ash) containing 100-4,000 ppm Strontium (or mg/kg) (Furr et al. 1977). Atmospheric concentrations of strontium emitted from coal fired power plants have been found to range from 17 to 2,718 mg/m3 in the western United States and are approximately 9,786 mg/m3 in the eastern United States (Ondov et al. 1989 Que Hee et al. 1982). Phosphate fertilizers are known to contain between 20 and 4,000 pg strontium/g solid by weight (Lee and von Lehmden 1973 Raven and Loeppert 1997). Strontium can be released into the atmosphere in windblown soil to which phosphate fertilizers have been applied. Pyrotechnic displays release low levels of strontium on the order of 5 mg/m3 in the immediate environment of the display (Perry 1999). 

The factors of soil formation (Section 7.3) determine the SOM content of soils. The order of importance of the factors that determine the organic matter (and nitrogen) contents of well-drained soils in the United States is climate > vegetation > topography = parent material > age. 

To put these numbers into perspective, they should be compared with natural radioactivity already contained in the crust of the earth. We consider a layer of soil all over the United States that is 1 m thick. Its volume is of the order of 10 m . With an average uranium concentration of 3 ppm, its uranium content is very roughly 3 X lO MT, corresponding to a total radioactivity of 10 Ci. This corresponds to about 1500 MT of U in the 1-m layer, a nuclide whose relative ingestion hazard resembles that of Pu within one order of magnitude. 

In a recent study, Clark et al. have compiled and analyzed measured concentration data of six phthalate esters in seven environmental media including water, sediment, soil, air, dust, food, wastewater, sewage sludge, and rainwater. The data are predominantly from Europe, the United States, Canada, and Japan. The complete database, with references, was presented in a report to the American Chemistry Council. The reported concentrations vary widely as an example, the overall mean concentration of BMP in surface water in Canada (1.40 /rg/1) is three orders of magnitude higher than that found in the U.S. (0.0017 /rg/1). The authors consider that this wide distribution is due to several factors including analytical error, sample contamination, and proximity to a variety of past and present phthalate sources. 

Scientists have developed computer models that depict the physical, chemical and biological processes within forest watersheds. Watershed acidification models can be used as research and management tools to investigate factors responsible for the historical acidification of soil and water as well as the ecosystem response to anticipated future changes in acidic deposition. In order to effectively predict the pH, ANC and aluminum concentrations in streams, all major chemicals must be accurately simulated (e.g., sulfate, nitrate, calcium, magnesium). The acidification model PnET-BGC was used for this assessment because it has been rigorously tested at Hubbard Brook and other sites in the northeastern United States, and it allows the user of the model to consider the ecosystem response to multiple chemicals simultaneously. Other frequently used acidification models include MAGIC (Cosby et al. 2001), and NuCM (Lui et al. 1992). 

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