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1.
2.
Using the soil gas radon as an indicator for ground contamination by non-aqueous phase-liquids 总被引:1,自引:0,他引:1
Michael Schubert Klaus Freyer Hans-Christian Treutler Holger Weiß 《Journal of Soils and Sediments》2001,1(4):217-222
1 The Problem One of the major problems facing risk assessment at polluted industrial sites and military bases is subsurface contamination
by non-aqueous phase-liquids (NAPLs), since tracing the extent of a NAPL plume using conventional methods (drive point profiling)
is usually associated with difficulties. In an effort to trace subsurface contamination as precisely as possible, monitoring
points are placed in the area that might be affected by contaminants, and groundwater and soil samples are taken to the laboratory
for analysis. However, the final number of monitoring points is hardly ever sufficient for distinctive contamination mapping,
and this may ultimately result in an unsuitable remediation action being taken.
2 Objectives To obtain a more detailed image of a subsurface NAPL plume and, hence, to facilitate remediation measures that are best suited
for the site in question, a denser network of monitoring points is desirable. The aim of the investigation described in this
paper was therefore to develop a new detection method for subsurface NAPL contamination, which is based on an easily accessibleindicator for NAPLs rather than on the analysis of soil and groundwater samples taken at the site. Based on the good solubility of
radon in NAPLs, the idea was put forward that subsurface NAPL contamination should have an influence on the natural radon
concentration of the soil gas. Provided this effect is significant, it would be possible to carry out a straightforward radon
survey on an appropriate sampling grid covering the suspected site and thus enabling the NAPL contamination to be detected
by the localization of anomalous low radon concentrations in the soil. The overall aim of the investigation was to assess
the general suitability of the soil-gas radon concentration as an indirect tracer for NAPL contamination in the ground.
3 Methods The partitioning coefficient KNAPL/air is one of the most influential parameters governing the decrease of the radon concentration in the soil gas in the presence
of a subsurface NAPL contamination. Since NAPL mixtures such as gasoline, diesel fuel and paraffin are among the most important
NAPLs regarding remediation activities, laboratory experiments were performed to determine the radon-partitioning coefficient
for these three NAPL mixtures.
Field experiments were carried out as well. The aim of the field experiments was to test the use of the soil-gas radon concentration
as a tracer for NAPL contamination on-site. For the field experiments, each site was covered with a suitable grid of soil
gas sampling points. Finally, the lateral radon distribution pattern achieved on each of the sites was compared to the respective
findings of the earlier research performed by conventional means.
4 Results and Discussion The results of the laboratory experiments clearly show a very strong affinity of radon to the NAPL mixtures examined. The
partitioning coefficients achieved correspond to those published for pure NAPLs (Clever 1979) and are thus in the expected
range. The results of the field experiments showed that the minimum radon concentrations detected match the respective NAPL
plumes traced previously.
5 Conclusions Both the results of the lab experiments and the on-site findings demonstrate that the soil-gas radon concentration can be
used as an indicator for subsurface NAPL contamination. The investigation showed that NAPL-contaminated soil volumes give
rise to anomalous low soil-gas radon concentrations in the close vicinity of the contamination. The reason for this decrease
in the soil-gas radon concentration is the good solubility of radon in NAPLs, which enables the NAPLs to accumulate and ‘trap’
part of the radon available in the soil pores.
6 Recommendations and Outlook Further research is required into contamination with rather volatile NAPLs such as BTEX. Further research is also needed to
examine whether it is possible to not only localize a NAPL plume, but also to obtain some quantitative information about the
subsurface NAPL contamination. The authors also believe that additional investigations should be carried out to study the
ability of the method to not just localize a NAPL contamination, but also to monitor on-site, clean-up measures. 相似文献
3.
Effects of grazing and rainfall variability on root and shoot decomposition in a semi-arid grassland
Marcus Giese Ying Zhi Gao Ying Zhao Qingmin Pan Shan Lin Stephan Peth Holger Brueck 《Applied soil ecology》2009,41(1):8-18
Overgrazing increasingly affects large areas of Inner Mongolian semi-arid grasslands. Consequences for ecosystem functions and, in particular, for the decomposition as a key process of ecosystem carbon (C) and nitrogen (N) cycling are still unclear.We studied the effects of grazing on shoot and root decomposition with the litter bag method in a long-term grazing exclosure (UG79), a moderate winter grazed (WG) and a long-term heavily grazed site (HG). We separated the effects of local environmental factors and litter quality as altered by grazing. Growing seasons of average and very low precipitation allowed us to study the effect of inter annual rainfall variability on decomposition.Grazing-induced differences in environmental factors of the three studied grassland sites had no effect on decay rates of shoot and root dry mass. Also differences in litter quality among the grazing sites were not reflected by root decomposition dynamics. The accelerated shoot decay at site HG could not clearly be linked to litter quality parameters. Shoot decay rates were more or less constant, even under very dry conditions. This indicates the possibility of photodegradation (solar UV-B radiation) to control aboveground decomposition in this semi-arid ecosystem. By selecting the best predictors of root decomposition from regression analysis, we found that soil water content was the best parameter explaining the dynamics.Net N immobilization was generally not detected during the decay process of shoot and root. It is likely, when root decomposition is strongly reduced in dry periods, shoot decomposition becomes relatively more important for nutrient cycling. A separate analysis of shoot and root decay dynamics is required in order to describe C and N cycling in this semi-arid grassland. The grazing impact on C and N fluxes through decomposition of plant material likely exhibits a strong interaction with seasonal rainfall pattern. 相似文献
4.
在已掌握甘蓝型油菜―萝卜附加系染色体构成,并构建萝卜分子连锁图谱的基础上,以甘蓝型油菜―萝卜附加系为材料,利用(dp)RAPD分子标记技术,筛选附加系中外源萝卜9条染色体(A~I)的分子标记,为进一步研究萝卜染色体与连锁群对应关系奠定基础.试验筛选了576个随机引物(组合),有413个能从附加系中扩增出萝卜染色体的(dp)RAPD标记,平均有效引物(组合)占71.7%,其中RAPD反应有效引物率67.7%,dpRAPD反应有效引物率73.2%.试验共得到899个萝卜染色体(dp)RAPD标记,包括354个RAPD标记和545个dpRAPD标记,覆盖萝卜整个基因组的全部9条染色体,不同染色体的标记数目变化范围在41~160,其中最多的是染色体C,最少的是染色体I. 相似文献
5.
Morten Eikenes Gry Alfredsen Bjørn Erik Christensen Holger Militz Halvor Solheim 《Journal of Wood Science》2005,51(4):387-394
Fungi cause serious problems in wood utilization, and environmentally benign wood protection is required as an alternative to traditional chemicals. Chitosan has shown promising antimicrobial properties against several microorganisms. In this study, we present the characterization of and antifungal properties of a commercial chitosan formulation developed for impregnation of wood. A broad range of chemical and mycological methods were used to evaluate the uptake, fixation, and antifungal properties of chitosan for wood preservation. The results show that the higher the uptake of chitosan the lower the relative recovery of chitosan in wood after leaching, and the higher the molecular weight of chitosan the higher the recovery. Chitosan with high molecular weight proved to be more efficient against decay fungi than chitosan with low molecular weight. The fungi tested on chitosan-amended nutrient agar medium were totally inhibited at 1% (w/v) concentration. In decay studies using small wood blocks, 4.8% (w/v) chitosan concentration gave the best protection against brown rot fungi. 相似文献
6.
Evgenii Sharapov Christian Brischke Holger Militz Elena Smirnova 《Wood material science & engineering》2020,15(4):198-204
ABSTRACT An IML-RESI PD 400 drilling tool and a standard spade drill bit (IML System GmbH, Wiesloch, Germany) were used to study the combined effect of wood moisture content (MC), drill bit rotational speed and feed rate on drilling resistance (DR) and feeding force (FF). Tests were made with Norway spruce (Picea abies (L.) Karst.) conditioned in a normal climate (20°C/65% RH), at 20°C/95% RH, vacuum-pressure impregnated in water, and oven-dried. Rotational speeds and feed rates had an impact on feed rate per cutting edge for the major cutting edge of the drill bit which was used for correlation with DR and FF for various MC. Impact of MC on DR and FF depended on rotational speeds and feed rates of the drill bit. For feed rates per cutting edge less than 0.09?mm, DR was higher for water saturated (WS) specimens. Negligible differences between DR for various MC were found for feed rates per cutting edge between 0.09 and 0.15?mm. DR was higher at low MC for feed rates per cutting edge which were higher than 0.15?mm. FF extremely increased in conditioned (20°C/95% RH) and WS specimens at feed rates per cutting edge less than 0.1?mm. 相似文献
7.
Philipp Schlotzhauer Alexander Ehrmann Susanne Bollmus Holger Militz 《Wood material science & engineering》2020,15(5):278-288
ABSTRACT Knowledge about perpendicular to grain tension behavior of wood is essential, since in construction tension stresses perpendicular to grain cannot be avoided completely. Especially for hardwoods, the data basis is scarce. EN 338 design values are with 0.6 N/mm² characteristic strength set very low. The US-American National Design Specifications even set this value to zero and make local reinforcements mandatory. This paper compares strength and stiffness values attained with newly-designed, little, prismatic specimens and EN 408 structural timber specimens to evaluate the current European design values. Little specimen’s characteristic strength values range from 7.2 to 10.6?N/mm² and are assumed to be real material properties. EN 408 specimen values are with approximately 4.0?N/mm² lower. These lower values are mainly due to stress peaks introduced by the force introduction. Strength values attained for the medium-dense European hardwoods beech, ash and maple exceed EN 338 design values by a factor of six to seven. Adaptation of the EN 338 design value is not recommended, though. The abundance of influencing factors makes clear that the design value and the ensuing design code have to be synchronized carefully by tedious testing in order to make use of the perpendicular to grain tension strength potential of the selected hardwoods. 相似文献
8.
Wood modification with alkoxysilanes 总被引:4,自引:0,他引:4
Steffen?Donath Holger?Militz Carsten?MaiEmail author 《Wood Science and Technology》2004,38(7):555-566
Wood was treated with three different alkoxysilanes which are able to undergo a sol–gel process: tetraethoxysilane (TEOS), methyl triethoxysilane (MTES) and propyl triethoxysilane (PTEO). Two types of treatments were compared: impregnation of fibre saturated wood with monomeric silane solutions, and impregnation with pre-hydrolysed partly oligomeric silanes. Wood properties such as cell wall bulking, anti-swelling efficiency (ASE), moisture uptake and durability were more significantly improved in samples treated with monomeric silanes than in samples treated with oligomeric silanes. SEM-EDX mapping showed that this treatment resulted in a higher degree of silicon incorporation into the cell wall, although the weight percent gain (WPG) was lower compared to the treatment with pre-hydrolysed partly oligomeric silanes. The resistance against soil micro-organisms was enhanced in the initial phase of incubation especially in those samples treated with organo-functional-alkoxysilanes. In miniaturised block tests with the white-rot basidiomycete Trametes versicolor, an improved durability was observed within the test period. During an air conditioning step, a weight loss of the treated samples occurred which was accompanied by a reduction in bulking and ASE. The initial reduction of moisture uptake observed after treatment diminished almost completely. This effect was explained by an ageing of the gels in the wood cell wall which is a consequence of uncompleted hydrolysis and condensation of the silanes during the treatment. 相似文献
9.
ABSTRACT The endophyte Piriformospora indica colonizes roots of a range of host plants and increases biomass production and resistance to fungal pathogens and, thus has been considered a biocontrol fungus. However, the field performance of this fungus has not yet been tested in temperate climates. Therefore, we evaluated the performance of this fungus in different substrata under greenhouse and practical field conditions. Roots of winter wheat were colonized efficiently, and biomass was particularly increased on poor substrata. In greenhouse experiments, symptom severity of a typical leaf (Blumeria graminis f. sp. tritici), stem base (Pseudocercosporella herpotrichoides), and root (Fusarium culmorum) pathogen was reduced significantly. However, in field experiments, symptoms caused by the leaf pathogen did not differ in Piriformospora indica-colonized compared with control plants. In the field, Pseudocercosporella herpotrichoides disease severity was significantly reduced in plants colonized by the endophyte. Increased numbers of sheath layers and hydrogen peroxide concentrations after B. graminis attack were detected in Piriformospora indica-colonized plants, suggesting that root colonization causes induction of systemic resistance or priming of the host plant. Although the endophyte is not well suited for growth at Central European temperature conditions, it remains to be shown whether P. indica is more suitable for tropical or subtropical farming. 相似文献
10.
The objective of this study was to determine the impact of earthworm bioturbation on the distribution and availability of zinc in the soil profile.Experiments were carried out with Allolobophora chlorotica and Aporrectodea caliginosa in 24 perspex columns (∅ 10 cm), filled with 20-23 cm non-polluted soil (OM 2%, clay 2.9%, pH 0.01 M CaCl2 6.4), that was covered by a 3-5 cm layer of aged zinc spiked soil (500 mg Zn/kg dry soil) and another 2 cm non-polluted soil on top. After 80 and 175 days, columns were sacrificed and each cm from the top down to a depth of 15 cm was sampled. Earthworm casts, placed on top of the soil, were collected. Each sample was analyzed for total and CaCl2-exchangeable zinc concentrations.Effects of earthworm bioturbation were most pronounced after 175 days. For A. chlorotica, total and CaCl2-exchangeable zinc concentrations in the polluted layers were lower with than without earthworms. Total zinc concentrations in the non-polluted layers were higher in columns with earthworms. Casts of A. chlorotica collected on the soil surface showed slightly higher total zinc concentrations than non-polluted soil. Casts were found throughout the whole column. For A. caliginosa there were no differences in total zinc concentration between columns with and without earthworms. CaCl2-exchangeable zinc concentrations in the polluted layers were lower for columns with earthworms. Casts were mainly placed on top of the soil and contained total zinc concentrations intermediate between those in non-polluted and polluted soil layers.This study shows that different endogeic earthworm species have different effects on zinc distribution and availability in soils. A. chlorotica transfers soil throughout the whole column, effectively mixing it, while A. caliginosa decreases metal availability and transfers polluted soil to the soil surface. 相似文献