The soil sample

If the designer is to do the job properly, it is important to have accurate data on which to base calculations. That is why test borings and proper laboratory analysis to determine the E value of the soil sample are essential. An arbitrary textbook selection of a soil modulus should always be avoided. However, if a pipe is to be buried deeper than the sampling zone that underwent laboratory testing to determine E and if the test bore shows the deeper material to be equal or better, then the designer may increase the E value proportionally to the square root of the differential soil stress. 

In random samples of soil taken from five Alabama counties, only 3 of 46 soil samples contained methyl parathion. The concentration in these samples was <0.1 ppm (Albright et al. 1974). Aspartofthe National Soils Monitoring Program, soil and crop samples from 37 states were analyzed for methyl parathion during 1972. Methyl parathion was detected in only 1 soil sample, at a concentration of <0.1 ppm and taken from South Dakota, out of 1,246 total samples taken from the 37 states (Carey et al. 1979). In soil and sediment samples collected from a watershed area in Mississippi, methyl parathion was not detected in the soil samples. In three wetland sediment cores, however, measurable concentrations of methyl parathion were detected during application season (Cooper 1991). 

Perhaps the most serious possibility for error at this stage of the sampling process Is In discarding of vegetation, sod, or other non-soil material collected along with the soil sample as well as the discarding of other materials retained on the sieve. It Is recommended that for approximately 10% of all samples where vegetation, sod, or other non-soil material Is discarded, all discarded material... 

Air-dried soil samples were screened through a 2-mm sieve, then the water content in the soil was calculated after holding the soil samples for 5h at 105 °C. 

The soil residue level is determined from the relative responses of the analytes to the internal standards. A five-point calibration curve is analyzed in triplicate, and the data are analyzed by a weighted 1 /x linear regression model. The calculated slope and intercept from the linear regression are used to calculate the residue levels in the soil samples. A 20% aliquot of the sample extract receives 10 ng of each internal standard... 

For wheat grain, extract the concentrate three times with 10 mL of chloroform-methanol (3 1, v/v). For the soil sample, extract the aqueous layer after washing with n-hexane twice with 60 mL of chloroform-methanol (3 1, v/v). Dry the chloroform-methanol layer with anhydrous sodium sulfate [for wheat grain, use a small amount (about 8 g) of anhydrous sodium sulfate] and collect the dried solution in a 200-mL round-bottom flask. Evaporate the solvent under reduced pressure and proceed to ion-exchange column chromatography. 

Transfer the concentrate from Section 6.1 to a 200-mL separatory funnel with 50 mL of water and add 10 mL of saturated aqueous sodium chloride solution. Extract twice with 100 mL of n-hexane. Dry the n-hexane extract by passing through about 80 g of anhydrous sodium sulfate on a glass funnel into a 500-mL separatory funnel for the rice samples and into a 500-mL round-bottom flask for the soil sample. Wash the anhydrous sodium sulfate with 30 mL of n-hexane and combine the washings into the vessel. The n-hexane extract of soil sample is evaporated to dryness under reduced pressure, then the soil residue is processed as described in Section 6.3.2. 

Dissolve the residue in 3 mL of n-hexane-ethyl acetate (6 1, v/v) and adsorb on the top of an alumina column bed. Rinse the flask three times with 1 mL of the same solvent mixture and transfer the rinsings to the column. Elute interfering substances with 50 mL of the same solvent mixture and discard the eluate. Then elute pyriminobac-methyl with 150 mL of the same solvent mixture. Collect the eluate in a 300-mL pear-shaped flask and evaporate to dryness under reduced pressure. The residue of the soil sample is dissolved in an appropriate volume of acetone for GC analysis. 

For soil, acetone-1 N sulfuric acid (4 1, v/v) is added to the soil sample and the mixture is refluxed. The subsequent procedures are as for cottonseeds. 

The soil sample is prepared by manually removing stones and plant material and passing through a 5-mm sieve. 

For soil samples, shake 20 g of a prepared air-dried soil sample with methanol-1 N hydrochloric acid [50 mL, 3 1 (v/v)] on a mechanical shaker for 30 min. Centrifuge the sample at 3500 rpm for 5 min and decant the supernatant into a round bottom flask (250-mL). Add a second 50 mL of methanol-1 N hydrochloric acid (3 1, v/v) to the soil sample and shake the mixture on a mechanical shaker for another 30 min. Centrifuge the sample at 3500 rpm for 5 min and then decant the supernatant into the same round-bottom flask (250-mL), combining the extracts. 

The soil samples are extracted by refluxing with a mixture of acetone and water. Mepanipyrim in the extract is purified by silica gel column chromatography and determined by GC/NPD. 

Weigh 40 g (dry weight basis) of the soil sample into a 500-mL round-bottom flask and add 200 mL of acetone-water (3 1, v/v) mixture. Attach a condenser to the flask and perform reflux extraction at 80 °C for 1 h. Filter the extract through a Alter paper on a Buchner funnel with suction into a 500-mL round-bottom flask. Rinse the residue on the funnel with 130mL of acetone, and Alter in the same manner. Combine and concentrate the extract under reduced pressure to 50 mL. Transfer the concentrate into a 200-mL separatory funnel with 10 mL of saturated aqueous sodium chloride... 

Weigh 50 g (dry weight) of the soil sample into a 500-mL Erlenmeyer flask and extract with 150 mL of acetone by shaking for 30 min. Filter the extracts by suction through a Buchner funnel using Whatman 934-AH filter paper and collect the extracts in a 500-mL round-bottom flask. Concentrate the organic extracts at 40 °C under reduced pressure. 

For soil. Extract 50 g (dry weight, containing about 5 g of the water) of the soil sample similarly as described above, using 95 mL of the distilled water. 

It was necessary to analyze the soil samples as soon as possible to avoid loss of ethylene dibromide. 

Representativeness of the soil sample being tested is the most crucial factor. Two case histories illustrate the importance and the difficulty of obtaining representative samples. 

Loessial soils contained 0.01-0.32 mg/kg bioavailable Mo (extracted with an oxalate buffer at pH 3.3) with an average of 0.06 mg/kg (n = 419). Seventy-four percent of the soil samples contained less than 0.10 mg/kg. Some crops in this region showed Mo deficiency. In soils of the... 

Soils in the North China Plain and Loess Plateau regions contained 0.04-3.01 mg/kg DTPA-extractable Zn with an average of 0.44 mg/kg. The concentrations of DTPA-extractable Zn in northern China are presented in Table 7.7. In the loessial soils of the Loess Plateau, 64% of the soil samples had less than 0.5 mg/kg of bioavailable Zn. The bioavailable Zn in the arid soils of North China varied from 0.08-11.84 mg/kg with an average of 1 mg/kg, with 41% of the soil samples having < 0.5 mg/kg of bioavailable Zn. The average amount of bioavailable Zn in calcareous soils was 0.35 mg/kg (trace - 1.12 mg/kg). The North China Plain and Loess Plateau are major Zn-deficient regions in China. Calcareous paddy soils frequently displayed Zn deficiency in rice. Zinc fertilizers have been applied to rice, maize, sorghum, wheat, cotton and fruit trees where bioavailable Zn was less than 0.5 mg/kg. 

In 156 arid soils sampled from the wheat fields of Pakistan, hot water-extractable B and ammonium oxalate/oxalic acid-extractable Mo were in the range of 0.104-5.746 and 0.029-1.364 mg/kg, respectively. DTPA-extractable Zn and Mn varied from 0.13-15.73 and from 4.68-18.59 mg/kg, respectively. EDTA-extractable Cu was from 1.69-29.51 mg/kg. The average and standard deviation of bioavailable B, Mo, Zn, Mn and Cu were 0.897 0.884, 0.257 0.213, 1.066 1.911, 11.05 2.99, and 6.24 2.99 mg/kg, respectively. These arid soils contained 0.7-18.1% CaC03 with soil pH from 7.89-9.25. In addition, in another 86 arid and semi-arid soils sampled from maize fields, higher bioavailable Mn (15.86 9.49 mg/kg) was found, but bioavailable Zn, Mo and Cu were also lower than those in the soils from arid wheat fields. Bioavailable Zn, Mo and Cu were 0.78 0.74, 0.190 0.103, and 5.72 1.95 mg/kg, respectively. However, the soils sampled from the maize fields had similar bioavailable B concentrations compared to those samples taken from the arid wheat fields. 

In silt clay soils (0-30 cm) of Isfahan, Central Iran, the amount of EDTA-extractable Zn, Cu, Pb, Ni, Cd, Co and Cr were 3.2, 1.8, 2.6, 0.6, 0.16, 0.6 and 0.8 mg/kg, respectively (Khoshgoftarmanesh and Kalbasi, 2002). Concentrations of these trace elements increased in subsoils (30-60 cm) and increased with applications of municipal waste leachate. In the surface soils of agricultural, industrial and urban regions of Isfahan, central Iran, the average DTPA-Cd was 0.09 mg/kg, and about 80% of the soil samples had less than 0.1 mg/kg DTPA-extractable Cd (Amini et al., 2005). DTPA-Cd was strongly correlated with EC in the soils. 

Table 4. Sporopollen abundance in the soil samples of SL profile at the Dinghushan Biosphere Reserve, South China ...

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