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71.
Aspects of phytoremediation of organic pollutants 总被引:1,自引:0,他引:1
Phytoremediation is a quite novel technique to clean polluted soils using plants. In theory, phytoremediation methods are
cheap, are accepted by the public and, compared to physical or chemical approaches, are ecologically advantageous. Until today,
however, there are only a few examples of successful applications. One reason is that the processes involved are complex,
and a full clean up may require many years. Plants affect the water balance of a site, they change redox potential and pH,
and stimulate microbial activity of the soil. These indirect influences may accelerate degradation in the root zone or reduce
leaching of compounds to groundwater. Compounds taken up into plants may be metabolised, accumulated, or volatilised into
air. Based on these processes, several phytoremediation methods have been developed: Phytoextraction, rhizofiltra-tion, phytostabilisation,
rhizo and phytodegradation, pump and tree, land farming, phytovolatilisation, hydraulic control and more. Already in use are
plants (and here willow, poplar and grass) for the degradation of petroleum products, aromatic hydrocarbons (BTEX), chlorinated
solvents, explosives and cyanides. However, phytotoxicity and pollutant mass balances were rarely documented. Often, the success
of the projects was not controlled, and only estimates can be made about the applicability and the potential of phytoremediation.
This lack of experience about possibilities and limitations seems to be a hindrance for a broader use of these techniques. 相似文献
72.
73.
Quantitative estimation of the mineralogical composition of silt fractions of soils based on both, chemical analysis and application of Karl-Fischer-titration. I. Method This paper describes a method for calculating the mineralogical composition of the silt fractions of soils. The chemical analysis and the temperature dependence of water release are used for determining micas and feldspars, each in three components in a relatively short procedure. The release of water was measured by Karl-Fischer-titration at controlled temperatures. At temperatures above 550°C the water release of the particle size fractions correlates with their content of micas. The quantity of micas can be obtained from the amount of released water and the results of the chemical analysis. The influence of kaolinite, amphibole and the fluoride content on the calculation is described. By considering the potassium content of the mica fraction results of the chemical analysis are used to quantify feldspars. 相似文献
74.
Sebastian Krahe Rolf-Alexander Düring Johan A. Huisman Andreas L. Horn Stefan Gäth 《Water, air, and soil pollution》2006,172(1-4):221-237
Partition coefficients K P of nonylphenol (NP) in soil were determined for 193 soil samples which differed widely in content of soil organic carbon (SOC), hydrogen activity, clay content, and in the content of dissolved organic carbon (DOC). By means of multiple linear regression analysis (MLR), pedotransfer functions were derived to predict partition coefficients from soil data. SOC and pH affected the sorption, though the latter was in a range significantly below the pKa of NP. Quality of soil organic matter presumably plays an important but yet not quantified role in sorption of NP. For soil samples with SOC values less than 3 g kg?1, model prediction became uncertain with this linear approach. We suggest that using only SOC and pH data results in good prediction of NP sorption in soils with SOC higher than 3 g kg?1. Considering the varying validity of the linear model for different ranges of the most sensitive parameter SOC, a more flexible, nonlinear approach was tested. The application of an artificial neuronal network (ANN) to predict sorption of NP in soils showed a sigmoidal relation between K P and SOC. The nonlinear ANN approach provided good results compared to the MLR approach and represents an alternative tool for prediction of NP partitioning coefficients. 相似文献
75.
Bergeron C Gafner S Clausen E Carrier DJ 《Journal of agricultural and food chemistry》2005,53(8):3076-3080
The aqueous extract of American skullcap (Scutellaria lateriflora L. (S. lateriflora), Lamiaceae) has been traditionally used by North American Indians as a nerve tonic and for its sedative and diuretic properties. Recent reports stated that flavonoids and possibly amino acids are responsible for the anxiolytic activity. As a part of our search for environmentally friendly solvents to extract the active components from medicinal plants, we used S. lateriflora in a comparison of accelerated solvent extraction (ASE) using water, and supercritical fluid extraction (SFE) using CO2 and 10% EtOH as modifier, at different temperatures. Flavonoids and amino acids were quantified by HPLC-UV and HPLC-MS, respectively. The flavonoid content was compared with conventional extraction methods (hot water extraction and 70% ethanol). The use of ASE at 85 degrees C with water as solvent gave the best results for flavonoid glycosides and amino acids, whereas SFE gave higher yields of flavonoid aglycones. However, the results obtained for total flavonoids were not significatively superior to hot water extraction or 70% aqueous EtOH extract. 相似文献
76.
Surface charge of clay-humus fractions from Chernozems as a function of pH and Ca-concentration The charge characteristics of clay-humus fractions from A-horizons of several Chernozems as a function of Ca concentration and pH of the soil solution was investigated. The surface charge was measured by titration with charge compensating polyelectrolytes; the endpoint was at zero potential. A logarithmic dependence of the surface charge [molc/kg] on the Ca concentration of the soil solution in the range ? 2 mmol/L was observed. The influence of pH on the surface charge was almost linear over a wide range of pH-values, the change in pH-dependent charges being most pronounced for the horizons with low Ca saturation on the exchange sites. It was also found that the competition between protons and Ca ions for the exchange sites leads to a distinct decrease of the influence of Ca concentration on the surface charge in acid environment. The reason for slaking of the soil surface and of the displacement of clay-humus particles in Chernozems could be attributed to an increase in surface charge with decreasing Ca concentrations after leaching of lime. According to the present findings the drop in mobility of the clay-humus fractions during acidification could be explained by a charge compensating effect of protons and aluminium ions. 相似文献
77.
Rates of carbon dioxide production of cocoons, juveniles and matures of Lumbricus rubellus were measured at five constant (2°C, 5°C, 10°C, 15°C, 20°C) and three diurnally fluctuating temperature regimes (0–10°C, 5–15°C, 10–20°C) covering the whole range of temperature conditions experienced by this species in forests in Central Germany. Respiration rates of developmental stages significantly increased with temperature both under constant and fluctuating regimes. Overall, at constant temperature regimes Q10 values for cocoons, juvenile and mature earthworms were 1.6, 2.7 and 2.0, respectively. At fluctuating temperature regimes Q10 values were generally higher with 2.4, 3.6 and 3.5 for cocoons, juvenile and mature earthworms, respectively. At the same mean temperature respiration rates at fluctuating regimes exceeded those at constant regimes in all developmental stages. 相似文献
78.
Ectomycorrhizae (ECM) or the root‐fungal association in forest ecosystems provide a unique soil microenvironment where soil properties and processes differ from the bulk soil. In this study, we would like to better understand the role of ECM systems in mineral weathering and its implications to soil formation and nutrient cycling in forest ecosystems. Specifically, we would like to document the spatial variations in the composition of soil solution and mineralogy of the rhizosphere as influenced by the ECM of Norway spruce + Piloderma croceum. Two‐month‐old seedlings of Norway spruce (control and colonized by P. croceum) were cultivated in special rhizotrons designed to allow spatial collection of soil solution. We used A and C horizons of a Dystric Cambisol collected from Höglwald forest near Munich. Micro suction cups (5 mm x 1mm) were installed in colonized and control rhizotrons, and soil solution was collected from September to November 2000. Our results show that the concentrations of NH , Ca2+, and Mg2+ in the soil solution were lower in <1.0 cm than in >3.0 cm distance from the roots of Norway spruce, due to the possible range of influence of Piloderma mycelium reaching about 2–3 cm from the surface of the mycorrhizal root. In the rhizotron with soil from the A horizon, a higher phosphorus content in Piloderma‐colonized seedlings was observed. X‐ray diffraction data indicate that chlorite and possibly mica are being transformed to 2:1‐expanding clay minerals (probably smectite) within <1.0 cm distance from roots. The spatial variations in soil solution composition and mineral transformation are likely to be due to Piloderma colonization and concentrated mycelial growth within <1.0 cm distance from the roots. This is also evident in more intricate growth of mycelia on surfaces of micaceous minerals as compared to quartz. We assume that Piloderma modifies soil solution and mineralogy through acquisition of essential elements for its own survival and/or for the uptake by plant roots. However, the presence of spontaneous infection with wildtype ECM in the control plots may have altered the influence of Piloderma and must be taken into consideration when interpreting our results. 相似文献
79.
The combined influence of a strongly interacting cosolvent (NaCl) and a weakly interacting cosolvent (sucrose) on the heat-induced gelation of bovine serum albumin (BSA) was studied. The dynamic shear rheology of 4 wt % BSA solutions containing 0 or 20 wt % sucrose and 0-200 mM NaCl was monitored as they were heated from 30 to 90 degrees C at 1.5 degrees C min(-)(1), held at 90 degrees C for 120 min, and then cooled back to 30 degrees C at -1.5 degrees C min(-)(1). The turbidity of the same solutions was monitored as they were heated from 30 to 95 degrees C at 1.5 degrees C min(-)(1) or held isothermally at 90 degrees C for 10 min. NaCl had a similar effect on BSA solutions that contained 0 or 20 wt % sucrose, with the gelation temperature decreasing and the final gel strength increasing with increasing salt concentration and the greatest changes occurring between 25 and 100 mM NaCl. Nevertheless, the presence of sucrose did lead to an increase in the gelation temperature and final gel strength and a decrease in the final gel turbidity. The impact of NaCl on gel characteristics was attributed primarily to its ability to screen electrostatic interactions between charged protein surfaces, whereas the impact of sucrose was attributed mainly to its ability to increase protein thermal stability and strengthen the attractive forces between proteins through a preferential interaction mechanism. 相似文献
80.