In order to test the hypothesis of aluminium toxicity induced by acid deposition, an experimental acid irrigation was carried out in a mature Norway spruce stand in Southern Germany (Höglwald). The experiment comprised three plots: no irrigation, irrigation (170 mm a?1), and acid irrigation with diluted sulphuric acid (pH of 2.6–2.8). During the seven years of acid irrigation (1984–1990) water containing 0.43 molc m?2 a?1 of protons and sulphate was added with a mean pH of 3.2 (throughfall?+?acid irrigation water) compared to 4.9 (throughfall) on both control plots. Most of the additional proton input was consumed in the organic layer and the upper mineral soil. Acid irrigation resulted in a long lasting elevation of sulphate concentrations in the seepage water. Together with sulphate both aluminium and appreciable amounts of base cations were leached from the main rooting zone. The ratio between base cations (Ca?+?Mg?+?K) and aluminium was 0.79 during acid irrigation and 0.92 on the control. Neither tree growth and nutrition nor the pool of exchangeable cations were affected significantly. We conclude that at this site protection mechanisms against aluminium toxicity exist and that additional base cation runoff can still be compensated without further reduction of the supply of exchangeable base cations in the upper mineral soil. 相似文献
Pollution of the atmosphere with cadmium (Cd), mercury (Hg), and lead (Pb) is a consequence of human activities. Natural archives
are necessary to reconstruct the long-term history of metal deposition because accurate measurement of atmospheric deposition
is a recent accomplishment. Reconstructions require: (1) accurate determination of concentrations of elements and isotopes,
(2) accurate chronology of archives, and (3) archives that faithfully record atmosphere deposition. The most useful long-term
archives are accumulations of ice and snow, peat, and lake sediment. Quantification of Cd deposition is uncommon because of
its low concentration and substantial chemical mobility. Nonetheless, trends in peat and lake sediment are similar to those
of Hg and Pb since ca. 1800 a.d. Both Hg and Pb are relatively chemically immobile and thus the peat and lake archives are believed to record historic trends
of atmospheric deposition. Isotopic and concentration studies of Pb indicate a history of northern hemisphere atmospheric
pollution extending back prior to 0 a.d. Although measurements of Hg concentration are now routine, isotopic measurements are in their infancy. Some Hg pollution
sources have unique isotopic ratios, thereby contributing unique signals to the total Hg. Maximum accumulation rates of Hg
and Pb occur up to 10 years later than for Cd (1970s versus 1960s in eastern North America, perhaps slightly later in Europe).
By 2004, deposition of Cd, Hg, and Pb had declined from peak values in eastern North America more than 75, 75, and 90%, respectively. 相似文献
Phospholipid fatty acid (PLFA) analysis has gained great importance in the study of soil microbial community structure. This structure can give indication of the soil status. Purpose of the present paper is to analyse PLFA patterns in altered agricultural soils in order to develop a soil status alteration index. Soils subjected either to intensive agricultural exploitation, or to overflow by municipal and industrial wastes, or to irrigation with saline waters were analysed for PLFA content and compared to adjacent untreated soils by means of different statistical techniques.
Principal component analysis separated PLFAs in three groups: unsaturated PLFAs (first axis, 48% of total variance), monounsaturated and cyclopropane PLFAs (second axis, 28% of total variance) and polyunsaturated PLFAs (third axis, 24% of total variance).
By means of canonical discriminant analysis, a soil alteration index (SAI) was produced from 15 PLFAs using two data sets. A third data set was used to test the SAI general validity together with other data sets reported in literature. The index validity was confirmed in most cases: SAI gave higher scores for control soils and was generally able to classify soils according to their reported degree of alteration. 相似文献
The optimum middle-phase microemulsion used for remediation of oily contaminated soils is often obtained by mixing a certain
amount of a surfactant/alcohol mixture with oil and adjusting the salinity concentrations at a constant water–oil ratio. Upon
introduction to the subsurface, however, the system may not be in the optimum state throughout the remediation process owing
to the change in the water–oil ratio. This research has attempted to investigate the effect of the water–oil ratio on the
phase behavior of systems containing brine, anionic surfactant, alcohols, and different oils. By systematically changing the
water–oil ratio, while keeping the others variables constant, the systems exhibited different phase behavior. The results
revealed that the effect of the water–oil ratio on system behavior was significant, and analogous to that of salinity. Increasing
the water–oil ratio led the system change from winsor I → winsor III → winsor II. The greater the water–oil ratio the lower
the salinity required to produce the middle-phase microemulsion, but the narrower the salinity range of the three-phase region.
An empirical correlation has been developed in order to predict the changes in phase behavior with the changes in water–oil
ratio. This provides a useful tool for designing optimum formulations suitable for soil remediation.
Received: October 5, 1999 / Accepted: March 27, 2000 相似文献
Geochemical mapping is a technique rooted in mineral exploration but has now found worldwide application in studies of the
urban environment. Such studies, involving multidisciplinary teams including geochemists, have to present their results in
a way that nongeochemists can comprehend. A legislatively driven demand for urban geochemical data in connection with the
need to identify contaminated land and subsequent health risk assessments has given rise to a greater worldwide interest in
the urban geochemical environment. Herein, the aims and objectives of some urban studies are reviewed and commonly used terms
such as baseline and background are defined. Geochemists need to better consider what is meant by the term urban. Whilst the
unique make up of every city precludes a single recommended approach to a geochemical mapping strategy, more should be done
to standardise the sampling and analytical methods. How (from a strategic and presentational point of view) and why we do
geochemical mapping studies is discussed.
In 2002, The (UK) Department for Environment, Food and Rural Affairs (DEFRA) together with the Environment Agency published
document SGV10 “Contaminants in soil: collation of toxicological data and intake values for humans. Lead”. This publication
sets out the derivation of Soil Guideline Values for lead contamination. Values for soil lead that are protective of the health
of children and also for adults are derived using the model recommended by an international task force working under the auspices
of the Society for Environmental Geochemistry and Health (SEGH) (Wixson and Davies 1993, 1994). Detailed examination of the DEFRA publication shows it uses unrealistic values for two variables in the SEGH model. The
consequence is both actual and has potential adverse societal impacts. These impacts could be avoided if the appropriate scientific
community were regarded as stakeholders in the legislative outcome and not simply the providers of the research data. 相似文献