Colorimetric determination of caffeic acid in plant materials   总被引：1，自引：0，他引：1  

K L Bajaj  Y K Arora 《Journal of the Association of Official Analytical Chemists》1979,62(5):1160-1161

A new colorimetric method is described for determining caffeic acid content in plant materials. Caffeic acid is separated by thin layer chromatography from the alcoholic extract, and color is developed using 0.5% aqueous thiosemicarbazide solution under alkaline conditions. The absorbance is read at 475 nm. Lambert-Beer's law is obeyed in the concentration range 0.37-17.5 micrograms caffeic acid/mL. The method is reproducible and has been applied to the estimation of caffeic acid in carrot roots.  相似文献   

Output of methylmercury from a Catchment in northern Sweden     

Y. H. Lee  K. Bishop  H. Hultberg  C. Pettersson  Å. Iverfeldt  B. Allard 《Water, air, and soil pollution》1995,80(1-4):477-481

The runoff output of methylmercury (MeHg) from the 50 ha Svartberget Catchment in northern Sweden was studied during 1993. These outputs are compared to those from the Gårdsjön Catchment in the southwestern part of Sweden. Although the wet deposition of MeHg is several times higher in southern Sweden the output of MeHg per unit area from the two catchments was comparable (0.12 g /km_* ²yr). Furthermore, the concentration of MeHg (0.4 ng/L) in the Svartberget Catchment was more than twice that from the Gårdsjön Catchment. These results suggest that the contemporary wet deposition of MeHg in itself is not a good indicator of runoff concentration or output per unit area. DOC transport and catchment characteristics such as wetland area, or possibly other forms of contemporary atmospheric deposition may all be more important for explaining MeHg output from the terrestrial ecosystem.  相似文献   

Regional Characteristics of Cooper Corrosion Components in East Asia     

M. Kitase  S. Hatakeyama  T. Mizoguchi  Y. Maeda 《Water, air, and soil pollution》2001,130(1-4):1463-1468

Copper plates were exposed under shelters at 13 sampling sites in East Asia and their corrosion was analyzed. The corrosion products were first dissolved in water and then oxalic acid. Sulfate, nitrate and chloride in the solutions were measured by ion chromatography. The amounts of the three anions significantly differed depending on the atmospheric environment at the sites. Sulfate was a major part of the anions at Chongqing and Shanghai in China. Especially, at the urban sites in Japan, nitrate remarkably changed with the seasons, and often became the large anionic component in the summer. The amounts of chloride at most sites were at higher concentration levels compared with those at the rural sites in Japan. The anions in the copper corrosion must mainly reflect the impact of acid deposition.  相似文献   

Internal Distribution of Acid Materials within Snow Crystals     

H. Fushimi  T. Kawamura  H. Iida  M. Ochiai  T. Nakajima  Y. Azuma 《Water, air, and soil pollution》2001,130(1-4):1709-1714

We found that river water is acidified not only in the first stage but also in the later stage of the snowmelt season in Japan, which differs from the so called acid shock occurring in the first stage of the snowmelt in the northern Europe. The acid shocks depend on the regional characteristics of the melt-refreeze processes forming the internal distribution of acid materials within snow crystals under the warm metamorphism. In a warm climatic region like the central Japan, there are possibilities to have the complicated distribution structure of acid materials within granular-snow crystals due to the repeated melt-refreeze processes even in midwinter. Consequently, the pH value of meltwater does not always increase as the snowmelt proceeds. Then, we showed the possibility by using the X-ray computed tomography that the domains with the acid materials exist in the inner parts of snow crystals. So, the acidification of the river water may occur even in the later stage of the snowmelt.  相似文献   

Mutagenicity determination of the wastewater emitted from petrochemical industry in Taiwan     

I. F. Mao  M. L. Chen  C. F. Lan  Y. P. Chang  S. C. Chang 《Water, air, and soil pollution》1994,76(3-4):459-466

Thirty-eight wastewater samples were collected from 19 petrochemical plants located in Taiwan during 1991. These plants represented most of petrochemical industry in Taiwan. Water samples were passed through an XAD-2 resin column and then eluted by acetone. The mutagenicity of wastewater was determined by the Ames Salmonella/microsome test. 52.6 and 26.3% of wastewater collected respectively in summer and winter were found to exhibit mutagenic activity in Salmonella typhimuriumTA 98 and TA 100. Four samples collected from 2 plants had higher levels of mutagenicity. The measurement and identification of mutagenic pollutants in this kind of wastewater need further investigation.  相似文献   

Glass transition and water effects on sucrose inversion by invertase in a lactose-sucrose system     

Kouassi K  Roos YH 《Journal of agricultural and food chemistry》2000,48(6):2461-2466

Enzymatic changes are often detrimental to quality of low-moisture foods. In the present study, effects of glass transition and water on sucrose inversion in a lactose-sucrose food model were investigated. Amorphous samples were produced by freeze-drying lactose-sucrose (2:1)-invertase (20 mg invertase/49.4 g of carbohydrate) dissolved in distilled water. Sorption isotherms were determined gravimetrically at 24 degrees C. Sucrose hydrolysis was determined by monitoring glucose content using a test kit and the amounts of fructose, glucose, and sucrose using HPLC. The glass transition temperatures, T(g), at various water contents were measured using differential scanning calorimetry (DSC). The BET and the GAB sorption models were fitted to experimental data up to a(w) 0.444 and 0.538, respectively. Water sorption and DSC results suggested time-dependent crystallization of sugars at a(w) 0.444 and above. Significant sucrose hydrolysis occurred only above T(g), concomitantly with crystallization. Sucrose hydrolysis and crystallization were not likely in glassy materials.  相似文献   

Estimation of rainfall erosivity using 5- to 60-minute fixed-interval rainfall data from China   总被引：2，自引：0，他引：2  

S. Yin  Y. Xie  M.A. Nearing  C. Wang 《CATENA》2007,70(3):306-312

The 30-min rainfall erosivity index (EI₃₀) is commonly used in the Universal Soil Loss Equation for predicting soil loss from agricultural hillslopes. EI₃₀ is calculated from the total kinetic energy and the maximum 30-min rainfall intensity of a storm. Normally, EI₃₀ values are calculated from breakpoint rainfall information taken from continuous recording rain gauge charts, however, in many places in China and other parts of the world the detailed chart-recorded rain gauge data relative to storm intensities are not readily available, while hourly rainfall is readily available. The objective of this study was to assess the accuracy of EI₃₀ estimations based on 5-, 10-, 15-, 30-, and 60-min time-resolution rainfall data as compared to EI₃₀ estimations from breakpoint rainfall information. 456 storm events from five soil conservation stations in eastern China were used. The values of EI₃₀ based on the fixed-time-interval data were less than those calculated from breakpoint data. The average conversion factors (ratio of values calculated from the breakpoint data to those from the fixed-interval data) for the five stations decreased from 1.105 to 1.009 for the estimation of E values, from 1.668 to 1.007 for I₃₀ values, and from 1.730 to 1.014 for EI₃₀ values as the time resolution increased from 60 to 5 min. The maximum 30-min rainfall intensity was the major source of error in estimating EI₃₀ for 60-min fixed-interval data, while storm kinetic energy played a proportionately more significant role as the fixed-interval data decreased from 60 to 5 min.  相似文献   

Arbuscular mycorrhizal fungus (Glomus aggregatum) influences biotransformation of arsenic in the rhizosphere of sunflower (Helianthus annuus L.)   总被引：2，自引：0，他引：2  

Venecio U. Y. ULTRA Jr    Sota TANAKA  Katsutoshi SAKURAI  K&#;z&#; IWASAKI 《Soil Science and Plant Nutrition》2007,53(4):499-508

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Arylsulphatase activity of different latosol soils of Ghana cropped to cocoa (Theobroma cacao) and coffee (Coffea canephora var. robusta)     

M. R. Appiah  Y. Ahenkorah 《Biology and Fertility of Soils》1989,7(2):186-190

Summary A study was undertaken to investigate arylsulphatase activity in 15 soils cropped to cocoa (Theobroma cacao) and coffee (Coffea canephora var. robusta) in Ghana. The arylsulphatase activity was correlated positively and significantly with organic C, total N, and cation exchange capacity, and correlated negatively with acetate soluble sulphate. The enzyme was deactivated at an incubation temperature of over 60°C. Preheating and oven-drying of soils decreased arylsulphatase activity. Addition of 1.0 ml toluene during the assay resulted in a sharp decline in arylsuphatase activity. The addition of trace elements at a concentration of 1 ppm caused a reduction in soil arylsulphatase activity compared with that of the untreated samples.  相似文献   

Flavor and texture of banana chips dried by combinations of hot air, vacuum, and microwave processing   总被引：1，自引：0，他引：1  

Mui WW  Durance TD  Scaman CH 《Journal of agricultural and food chemistry》2002,50(7):1883-1889

The behavior of 16 volatile compounds of banana during a combination of air-drying (AD) and vacuum microwave-drying (VMD) of banana chips was characterized. Samples were AD to remove 60, 70, 80, or 90% of moisture (wet basis) and then subjected to VMD to achieve a final moisture content of 3% (dry basis). Banana slices were also dehydrated using only AD, VMD, and freeze-drying (FD) for comparison. Samples that underwent more VMD had significantly lower levels of volatile compounds, which is attributed to the decreased formation of an impermeable solute layer on the surface of the chips. High values for water solubility and relative volatility of compounds correlated with losses during VMD; however, additional factors appear to influence the behavior of compounds during VMD processing. The optimal process of 90%AD/10%VMD yielded crisper banana chips with significantly higher volatile levels and sensory ratings than AD chips.  相似文献