Natural and anthropogenic components of soil acidification

The following 8 theses are theoretically founded and experimentally quantified. 1. Rocks contain only bases and no acid precursors. Therefore, with the exception of sulfide containing rocks, soils cannot acidify as a result of atmospheric rock weathering. 2. A consumption of protons in rocks and soils results in a decrease of their acid neutralizing capacity (ANC) and can result in the buildup of a base neutralizing capacity (BNC). Strong soil acidification leads to the formation of stronger acids from weaker acids in the solid phase; this may be connected with a decrease in the BNC. 3. Weak acids (carbonic acid) lead in geological times to the depletion of bases without a larger accumulation of labile cation acids. Strong acids (HNO₃, organic acids, H₂SO₄) can lead within a few decades to soil acidification, i.e. to leaching of nutrient cations and the accumulation of labile cation acids. 4. The acid input caused by the natural emission of SO₂ and NO_x can be buffered by silicate weathering even in soils low in silicates. 5. The cause of soil impoverishment and soil acidification is a decoupling of the ion cycle in the ecosystem. 6. Acid deposition in forest ecosystems which persists over decades leads to soil acidification. 7. Formation and deposition of strong acids with conservative anions (SO₄, NO₃) shifts soil chemistry into the Al or Al/Fe buffer range up to great soil depth. In such soils eluvial conditions prevail throughout the solum and even in upper part of the C horizon: in connection with the decomposition of clay minerals, Al and eventually Fe are being eluviated. The present soil classification does not include this soil forming process. 8. In the long run, soil acidification by acid deposition results in the retraction of the root system of acid tolerant tree species from the mineral soil, and in water acidification.     

Chemische Eigenschaften von Waldböden im Nordwestdeutschen Pleistocän und deren Gruppierungen nach Pufferbereichen

Chemical properties of forest soils in the pleistocene of Northwest Germany and their classification based on soil buffering systems In order to characterize the chemical characteristics of forest soils of Hamburg, 800 soil samples and 400 root samples from 172 sites were used to obtain suitable soil chemical and ecochemical parameters. A strong and deep reaching soil acidification was observed on all sites with exception of those on till. The sulfate concentration in the equilibrium soil solution allows the conclusion that deposition of acid plays a significant role in this acidification. Classification of sites based on edaphic factors did not provide useful information on the chemical status of soils. However, grouping of soil horizons using pH measured in 0.01 M CaCl₂ lead to a stratification according to the soil buffering systems. Distinction between the exchanger and the aluminium buffer ranges was, however, not quite satisfactory.     

Sexual differentiation in litter-bearing mammals: influence of sex of adjacent fetuses in utero

In rodents and swine, individual differences in a broad range of characteristics correlate with intrauterine position during fetal life. By identifying the intrauterine position of mice at cesarean delivery, we can predict reliably postnatal reproductive traits such as genital morphology, timing of puberty, length of estrous cycles, timing of reproductive senescence, sexual attractiveness, sexual behavior, aggressiveness, daily activity level, body weight and tissue enzyme activity in females; in males we can predict genital and brain morphology, sexual behavior, aggressiveness, daily activity level, body weight, and tissue enzyme activity. In mice, as in all mammals, male fetuses have greater concentrations of testosterone than do females. In addition, female mouse fetuses have greater circulating concentrations of estradiol than do male fetuses, a condition not found in all mammals. A mouse fetus positioned between males has greater concentrations of testosterone than does a fetus of the same sex positioned between females, and a fetus positioned between females has greater concentrations of estradiol than does a fetus of the same sex positioned between males. Gonadal steroids regulate differentiation of secondary sexual characteristics. Studies in which the effects of intrauterine position have been eliminated by exposing fetuses to steroid receptor blockers reveal the critical role of steroids in mediating this phenomenon. The intrauterine position phenomenon provides the only mammalian model for relating postnatal traits to concentrations of endogenous hormones to which individuals are exposed during fetal life. Results from studies using this naturally occurring experimental system in litter-bearing species have given insights concerning the consequences of individual differences in steroid concentrations during sexual differentiation that likely apply to all mammals. One specific hypothesis is that circulating estradiol may interact with testosterone in mediating some aspects of sexual differentiation in rodents and, thus, possibly in other mammals.     

Validation of a method for the detection of virulent Yersinia enterocolitica and their distribution in slaughter pigs from conventional and alternative housing systems

Various methods have been described in the literature for the detection of virulent Yersinia enterocolitica in pigs. The risk factors for pig herd contamination have yet to be determined. The objective of this study was to validate a sensitive method for the detection of Y. enterocolitica and to describe the distribution of the bacteria in pigs at slaughter from conventional and alternative ("organic") housing systems. First, samples were collected from tonsils, caecum with caecal contents, and the caecal lymph nodes of 60 slaughter pigs. These samples were used to compare the sensitivity of six different laboratory culture methods either in common use or described in the literature with that of a polymerase chain reaction with two primer pairs (multiplex PCR). Then, only PCR was used to examine tonsils, caecum and caecal lymph nodes from two groups of slaughter pigs: 210 from six conventional fattening farms and 200 from three with alternative housing. The results of the multiplex PCR were positive in 28 cases. All culture methods proved inferior to PCR in sensitivity. In the second part of the study, PCR detected 36 (18%) positive pigs from alternative housing and 60 (29%) from conventional housing (p<0.05). The highest rate of Y. enterocolitica contamination was found in tonsils (11% alternative, 22% conventional; p<0.05), followed by caecum (5%, 11%) and lymph nodes (2%, 7%). The housing system appears to be one important factor in the prevalence of this common pathogen in pig herds, as we found important differences between the two systems studied here. In the conventional system, the main risk factors appeared to be sourcing pigs from different pig suppliers, use of commercial feed and transportation to slaughter.     

The challenge of micropollutants in aquatic systems

The increasing worldwide contamination of freshwater systems with thousands of industrial and natural chemical compounds is one of the key environmental problems facing humanity. Although most of these compounds are present at low concentrations, many of them raise considerable toxicological concerns, particularly when present as components of complex mixtures. Here we review three scientific challenges in addressing water-quality problems caused by such micropollutants. First, tools to assess the impact of these pollutants on aquatic life and human health must be further developed and refined. Second, cost-effective and appropriate remediation and water-treatment technologies must be explored and implemented. Third, usage and disposal strategies, coupled with the search for environmentally more benign products and processes, should aim to minimize introduction of critical pollutants into the aquatic environment.     

Charcoal and smoke extract stimulate the soil microbial community in a highly weathered xanthic Ferralsol

The influence of charcoal and smoke condensates (pyroligneous acid, PA) on microbial activity in a highly weathered Amazonian upland soil was assessed via measurements of basal respiration (BR), substrate-induced respiration (SIR), and exponential population increase after substrate addition. PA extracts are commonly used for fertilizer or as pest control in Brazil, where phosphorus (P) availability and nitrogen (N) leaching are among the most severe limitations for agriculture. Microbes play an important role in nutrient cycling and solubilizing of phosphate. BR, microbial biomass, population growth and the microbe's efficiency (expressed by the metabolic quotient) increased linearly and significantly with increasing charcoal concentrations (50, 100 and 150 g kg⁻¹ soil). Application of PA caused a sharp increase in all parameters. We suppose that the condensates from smoke contain easily degradable substances and only small amounts of inhibitory agents, which could be utilized by the microbes for their metabolism.