共查询到20条相似文献，搜索用时 31 毫秒
1.
Rog B. Parsons 《Geoderma》1978,21(1):25-39
The development and distribution of soils in the Coast Range and Klamath Mountains are related to geomorphic surfaces and slope gradients. Soils over basalt, studied in the Coast Range, were formed in transported materials and include examples of more than a half dozen great groups of the Alfisol, Inceptisol, Mollisol, and Ultisol orders. Distribution patterns of the soils can be related to active slopes, metastable slopes, pediments, ridge tops, flood plains, and alluvial fans. Variables among the factors of soil formation in the Coast Range are chiefly geomorphic surfaces and parent materials.Soils of a lithosequence of pyroclastics, granite and schist in the Klamath Mountains include examples of great groups in the Entisol, Inceptisol, and Mollisol orders. All soils from pyroclastics have argillic horizons, those from granite lack argillic horizons, and those from schist lack argillic horizons except on relatively stable surfaces. Average thicknesses of soils over saprolite range from 76 cm over granite and schist to 150 cm over pyroclastics.Lithologic discontinuities are common in both mountain areas. Field techniques for identification, described briefly, include stone lines, irregular distribution of rock fragments with depth, thicknesses of weathering rinds on rock fragments, and the lateral extensions of soil horizons. 相似文献
2.
The seller's risk-the probability of a set of samples exceeding an agreed upon aflatoxin level when the lot mean does not-and the buyer's risk-the probability of a lot exceeding this level when a set of samples do not-have been computed using a parametrized experimental aflatoxin distribution and Monte Carlo simulation. The calculations are exemplified using the proposed EC standards (three 10 kg samples, 4 ng/g of total aflatoxin, basis kernels only) as well as for samples up to 250 kg and for varied lot aflatoxin levels. It is found that within this sample size range the seller's risk is as high as 42% at 10 kg and increases with increasing sample size to 80% at 250 kg. Only by reducing lot levels to 0.2 ng/g of total aflatoxin, basis kernels, can the risk be brought down to 2.5%, independent of sample size. The buyer's risk is as high as 58% at 10 kg but falls to 11% at 250 kg samples. The implications for both seller and buyer strategies are discussed. 相似文献
3.
Schatzki TF 《Journal of agricultural and food chemistry》2000,48(9):4365-4368
Sequential sampling for aflatoxin testing in pistachios is evaluated using the aflatoxin distribution and Monte Carlo results previously obtained (J. Agric. Food Chem. 1999, 47, 3771-3775). The sequential protocol is modeled on the current EU test protocol by applying a three-step sampling, using 10, 20, and 30 kg sample averages. An acceptance level of 15 ng/g of total aflatoxin, under consideration for U.S. standards, is applied. Optimization leads to indifference regions of 2-30 ng/g for the first two steps. The resulting OC curve approximates that for a single 50 kg sample. The sequential protocol is applied to the results for a set of 1293 lots of the 1998 crop year, each tested with a single 10 kg sample. Ninety-five percent of the lots would have been accepted on the basis of the single test and 1.5% would have been rejected, whereas 3.5% of the lots would have required retesting. 相似文献
4.
5.
E J de Vries F J Mulder B Borsje 《Journal of the Association of Official Analytical Chemists》1978,61(3):731-734
The official first action method for determining vitamin D in multivitamin preparations was modified. The method was collaboratively studied by 7 laboratories, using 6 preparations in oil. The preparations consisted of vitamin D at various levels and at various ratios (in w/w) in vitamin A. Three samples contained cholecalciferol and 3 samples contained vitamin D3 from vitamin D3 resin. After outliers were eliminated by the Dixon test, data were analyzed and averages were compared with amounts of vitamin D known to be in each sample. For samples with vitamin D: vitamin A ratios of 1:0.5, 1:5, and 1:10, the mean vitamin D recoveries were 98.8, 94.6, and 90.7%, respectively. The method has been adopted as official final action. 相似文献
6.
A simple procedure is described for the routine determination of pentachlorophenol (PCP) in various types of toy paints. PCP can be determined in water colors, body colors, showcard paints, gouache paints, and colored inks. PCP is extracted from the sample with acetone, followed by quantitative gas chromatographic analysis of the concentrated acetone extract on stainless steel columns containing 15% Carbo-wax 20M on 60-80 mesh Chromosorb P (AW). As little as 1 ppm PCP can be determined with recoveries ranging from 50 to 100%, depending on the type of paint. The presence of PCP in samples is confirmed by thin layer chromatography, using dansyl chloride as a fluorescent labeling compound. By this method as little as 4 ppm can be determined. The results of PCP determinations in 65 commerical samples are presented. 相似文献
7.
An account is given of a study of the size and diversity of populations of Clostridium pasteurianum and C. acetobutylicum in representative soils sampled at various latitudes and altitudes within the U.S.S.R. Evidence is presented to show that the two species are well adapted to soil and climatic factors in terms of the relative dominance of the two species and in terms of differences in their growth-temperature characteristics, carbohydrate utilization and fermentation products, nitrogen fixation and the comparative chemistry of their cells. In all of these characteristics, C. pasteurianum was more variable than C. acetobutylicum. 相似文献
8.
Water, Air, & Soil Pollution - The effects of acid rain on surface horizons of five soils from Galicia and the buffer capacity of these soils with respect to the addition of H` were studied.... 相似文献
9.
Alexander M. Green 《Water, air, and soil pollution》1974,3(2):237-248
Water resources are essential for economic and cultural development of a territory. Both economic development and the health of the people depend on the provision of pure water. Scientifically founded plans of water resources use and conservation should be based on a balance approach to the assessment of available water supply sources and, on the forecast of their interconnected change in the future in a close association with the forecast of the whole economy and culture of the studied region. In the future the main threat to the normal development of the economy and life will not be water deficiency but the conversion of rivers, lakes and other water supply sources into sewers. Therefore it is proposed that there be a complete cessation of sewage discharge (even of the so-called purified) into water supply sources while drawing up long-term water management balances. 相似文献
10.
T Suzuki K Ishikawa N Sato K I Sakai 《Journal of the Association of Official Analytical Chemists》1979,62(3):681-684
A rapid analytical method for determining chlorinated pesticide residues in milk was developed. Thirteen pesticides were almost completely extracted. Ten mL samples of fortified milk were extracted 3 times with 20 mL portions of n-hexane as follows: (A) in the absence of water-soluble solvent; in the presence of (B) 1 mL acetonitrile; (C) 3 mL acetonitrile; (D) 5 mL acetonitrile; (E) 5 mL ethanol; (F) 5 mL acetonitrile and 1 mL ethanol. System F produced the highest pesticide recoveries but the lowest fat extraction, thus eliminating the necessity for liquid-liquid partitioning and minimizing Florisil column cleanup. Pesticide recoveries throughout the procedure were 94--103%. It was noticed, however, that the fat in high fat-containing raw milk is more readily extracted than that in commercial milk. 相似文献
11.
Heavy metal residues (i.e., As, Cd, Cu, Pb, Mn, Hg, and Zn) were determined in striated muscle of 268 fish specimens harvested during a 5-yr period (1980–1984) from several aquatic systems in east Tennessee (U.S.A.). Elevated concentrations of Hg, Mn, and Cd were found in the muscle of fish from several of the aquatic systems studied; concentrations of Hg exceeded the U.S. Food and Drug Administration action level of 1.0 ppm for food intended for human consumption. In general, the concentrations of the other metals in fish muscle were low. Moreover, muscle metal content did not vary among the three fish groups (i.e., game fish, catfish, and rough fish) investigated at any one of the nine sampling stations established. The results of this study are in agreement with the 1978–1979 pilot survey of Young and Blevins (1981) conducted at the same sampling stations. It appears that, in this region of Tennessee, heavy metal contamination of fish tissues has neither improved nor deteriorated during the last 5 yr. 相似文献
12.
serA基因编码3-磷酸甘油酸脱氢酶（PGDH）,此酶在合成L-丝氨酸的第一步起催化作用。利用质粒pCM80分别与野生型基因serA、缺失了C末端ACT功能域的突变基因serA△77构建了重组体表达菌MB200/pCM80serA和MB200/pCM80serA△77。通过分析发现野生型基因重组表达菌的PGDH酶活受L-丝氨酸浓度影响较大,当反应体系中的L-丝氨酸浓度为40μmol/L时,酶活减少了约1/3;缺失了ACT功能域的基因表达菌的PGDH酶活基本不变,不受L-丝氨酸浓度的影响。进一步在静息细胞反应条件下,对重组菌和野生菌株MB200进行发酵产L-丝氨酸的研究,实验发现MB200/pCM80serA产L-丝氨酸的量为13.6mg/mL,MB200/pCM80serA△77产L-丝氨酸的量为16.8 mg/mL,而野生型菌株M.sp MB200的产量为6.4 mg/mL,重组菌的L-丝氨酸产量都有所提高,且MB200/pCM80serA△77的产量提高更多。结果证实了甲基营养菌MB200中serA基因与产L-丝氨酸具有反馈抑制关系,为进一步解除反馈抑制并发酵产L-丝氨酸奠定了基础。 相似文献
13.
In Illinois, atmospheric deposition is one major source of heavy metal inputs to agricultural land. The atmospheric Pb deposition and transport record in agricultural soils in Champaign, Illinois, was established by studying surface and subsurface soil samples collectedduring the past 100 years from the Morrow Plots on the campus of the University of Illinois at Urbana-Champaign. The Pb content in the soilsamples was measured and the Pb deposition fluxes were calculated. ThePb content in surface soils increased sharply in the first half of the20th century, and stayed invariant since. The maximum Pb flux from theatmosphere was estimated to be 27 (±14) μg cm-2 yr-1around 1940. The major pollution source for this increase probably was residential coal burning. It was estimated that in 50 yr, morethan 50% of the Pb input had been lost from the surface soils. 相似文献
14.
The nature of the alkaline hydrolysis of some barbiturates in combinations with parabens (p-hydroxybenzoates) was studied with controlled variables, including temperature, viscosity, and concentrations of sodium hydroxide, barbiturate, and parabens. The kinetic studies showed that parabens could be completely hydrolyzed in strong base at 40 degrees C in 1 hr, while the barbiturate remained intact and was readily isolated by partition chromatography, Based on the theoretical results, a partition chromatographic procedure for butabarbital with parabens was devised. Standard recoveries averaged 100.7% with a standard deviation of 0.89. Kinetic data indicate that the hydrolysis of parabens could also be applied to analyze combinations with amo-, seco-, and pentobarbitals. Phenobarbital and parabens are readily separated by partition chromatographic methods without prior hydrolysis of the parabens. The low extraction constant for phenobarbital allowed its retention on a column against relatively strong solvents while the intact parabens are eluted. A slightly modified method was applied to the separation of phenobarbital from parabens. Standard recoveries average 99.9% with a standard deviation of 0.69. 相似文献
15.
The official final action acid hydrolysis method, 14.019, for the determination of fat in foods was successfully applied, with slight modifications, to the analysis of homogenates of food, feces, and animal tissues as well as dry samples of mixed foods. In samples containing sucrose or fructose, it was necessary to carry out a fermentation procedure before acid hydrolysis to avoid problems encountered when these sugars were present. 相似文献
16.
V. K. Savost’yanov 《Eurasian Soil Science》2006,39(10):1154-1155
17.
R J Bushway C W Cramer A R Hanks B M Colvin 《Journal of the Association of Official Analytical Chemists》1975,58(5):957-960
A simple and rapid high-performance liquid chromatographic procedure is described for the determination of strychnine. Grain baits containing strychnine alkaloid are ground, mixed, and extracted by shaking with chloroform. Without further cleanup, extract filtrates are injected directly into a liquid chromatograph. Chromatography is complete within 7 min and peak heights are used for quantitation. Separations were made on a 30 cm times 4 mm id stainless steel column packed with mu Porasil (8-12 mum silica). The eluting solvent was methanol-chloroform (10+90) at a flow rate of 2.0 ml/min. Recovery of spiked samples ranged from 91.5 to 95.2%. Confirmation of strychnine from a commercial sample was made by high resolution mass spectrometry with mass agreement to 1.2 ppm. 相似文献
18.
S.T. Willatt 《Geoderma》1979,22(4):323-331
Water contents were measured in a soil profile during the winter from the time of harvest until soil temperatures were greater than 0°C through this profile in the spring. Water movement between successive layers was predicted using the Darcy flow law and changes in water flux. These values were then compared with the changes in soil water content observed in field measurements. Results showed that water content changes (accumulation or loss) below the frozen layer were greater than predicted but that the differences between predicted and measured contents were small, much smaller than the amounts reported in previous experiments. 相似文献
19.
Onondaga Lake, N.Y., failed to turnover in the spring of 1986 because of the strong chemical stratification under the ice that developed as a result of ionic discharges from an alkali plant. This stratification had a negative impact on the O2 resources of the lake, as the lower depleted layers of the lake were not replenished with O2. Anoxia and anaerobiesis in the bottom water expanded following ‘ice-out’. Comparison of characteristics observed for the winter through spring interval of 1986 with historic data indicates Onandaga Lake has failed to experience spring turnover in a number of years (approximately 7 of the last 18 yr) because of the ionic discharges from the alkali plant. 相似文献
20.
S Fuchs T Beck M Sandvoss A Mosandl 《Journal of agricultural and food chemistry》1999,47(8):3058-3062
Mentha x piperita shoot tips and first leaf pairs were fed with aqueous solutions of different deuterium-labeled pulegone and various enantiomeric distributions. The essential oil was extracted by solid-phase microextraction and analyzed using enantioselective multidimensional gas chromatography/mass spectrometry. The genuine p-menthan-3-ones (-)-menthone and (+)-isomenthone as well as their labeled analogues were analyzed simultaneously. Both enantiomers of labeled pulegone were converted into the corresponding labeled p-menthan-3-ones by Mentha x piperita, indicating an unspecific reduction process. The generation of 4S- and 4R-configured p-menthan-3-ones differed in their stereoselectivities. Labeled (S)-pulegone was reduced by Mentha x piperita more rapidly rather than (R)-pulegone. From a comparison of labeled pulegone enantiomers the bioconversion preferrably led to 4S-configured diastereomers. 相似文献