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The proper selection of the background electrolyte is of special importance studying element availability and mobility in the laboratory. The determination of the background solution composition can be done with the equilibrium soil solution method ESS (Matschonat and Vogt, 1997). The ESS method is a procedure to find out a salt solution of major cations and anions that does not undergo changes in its composition when brought into contact with a specific soil sample. This composition is experimentally approximated in an iterative procedure until certain quality criteria are fulfilled. We tested if the ESS method, which was developed for forest soils, can successfully be applied also to agricultural soils. The solution composition was confirmed by an independent method. We used samples of a glasshouse and an arable loess soil. Because the ESS method is relatively time and work consuming, we tested modifications which should simplify the procedure: the use of dried and frozen samples instead of field fresh soil, an approximation according to the solution's electric conductivity only, and the modeling of cation exchange to omit iteration steps. The ESS method caused slight overestimation (10–25 %) in cation concentrations, but in general, these were well met. Individual anion concentrations, however, were not buffered in this soil and could not unequivocally be determined. We recommend to adjust the anion concentrations in the ESS procedure according to their proportions in an initial water extract. As ion concentrations are functions of the soil : solution ratio, any method based on addition of water to the soil, like the so‐called soil saturation extract (Germany: Bodensättigungsextrakt), runs a risk to seriously underestimate ion concentrations at field conditions. The ESS method may therefore be especially well suited for soils with a low water content. The use of frozen soil gave good results and the omission of iteration steps by cation exchange modeling was promising and will be explored with the aim to operationalize it in forthcoming work. 相似文献
3.
Pfau T Garland de Rivaz A Brighton S Weller R 《Veterinary journal (London, England : 1997)》2011,190(2):278-283
A recent survey reported an increased risk of injury in dogs participating in agility, a competitive canine sport involving different jumping activities. The aim of this study was to quantify the kinetic parameters during jump landing for commonly used obstacle types. It was hypothesised that with increasing obstacle height, the vertical force and vertical and accelerative horizontal impulse will increase as a result of a lengthened aerial phase, a more acute landing angle and the need to convert potential into forwards kinetic energy. Simultaneous kinetic and kinematic data were recorded from 11 competition agility dogs jumping over obstacle combinations of different height and inter-obstacle distance. Speed and landing angle of the second of the two consecutive jumps were successfully controlled by obstacle height and distance between obstacles. Statistical analysis showed differences between obstacles for peak vertical force, vertical impulse and accelerative horizontal impulse (increasing values with more acute landing angles). Extremely high peak vertical force was observed in the forelimbs (4.5 times bodyweight) when landing from a hurdle jump at high speed. Further detailed studies into the consequences for internal limb structures are warranted in order to clarify how this might be related to injury. 相似文献
4.
Dissolved organic matter (DOM) is involved in many important biogeochemical processes in soil. As its collection is laborious, very often water‐soluble organic matter (WSOM) obtained by extracting organic or mineral soil horizons with a dilute salt solution has been used as a substitute of DOM. We extracted WSOM (measured as water‐soluble organic C, WSOC) from seven mineral horizons of three forest soils from North‐Rhine Westphalia, Germany, with demineralized H2O, 0.01 M CaCl2, and 0.5 M K2SO4. We investigated the quantitative and qualitative effects of the extractants on WSOM and compared it with DOM collected with ceramic suction cups from the same horizons. The amounts of WSOC extracted differed significantly between both the extractants and the horizons. With two exceptions, K2SO4 extracted the largest amounts of WSOC (up to 126 mg C kg–1) followed by H2O followed by CaCl2. The H2O extracts revealed by far the highest molar UV absorptivities at 254 nm (up to 5834 L mol–1 cm–1) compared to the salt solutions which is attributed to solubilization of highly aromatic compounds. The amounts of WSOC extracted did not depend on the amounts of Fe and Al oxides as well as on soil organic C and pH. Water‐soluble organic matter extracted by K2SO4 bore the largest similarity to DOM due to relatively analogue molar absorptivities. Therefore, we recommend to use this extractant when trying to obtain a substitute for DOM, but as WSOM extraction is a rate‐limited process, the suitability of extraction procedures to obtain a surrogate of DOM remains ambiguous. 相似文献
5.
REASONS FOR PERFORMING STUDY: Previous studies have implicated tension in the deep digital flexor tendon (DDFT) in the rotation of the distal phalanx (DP) after the breakdown of the dorsal laminae caused by laminitis. Howeveer, once the DP has rotated, the DDFT should become shorter, reducing the force it exerts on the DP. OBJECTIVE: To compare DDFT force and ground reaction forces (GRFs) in normal ponies and ponies with rotation of the DP as a sequel to laminitis. METHODS: Six normal ponies (Group 1) and 6 sound ponies with 6-13 degrees of rotation of the DP in relation to the dorsal hoof wall (Group 2) were assessed at trot using forceplate and motion analysis. The force in the DDFT was calculated by assuming that the extending moment at the distal interphalangeal (DIP) joint resulting from the GRF was equal to the flexing moment created by the force in the DDFT during the stance phase (inverse dynamics). RESULTS: In early stance, the peak DDFT force (mean+/-s.d.) in the normal ponies was 1.92+/-1.63 N/kg. However, in Group 2, the point of zero moment was palmar to the centre of rotation of the DIP joint for the first 40% of stance and hence DDFT force was zero. Force in the DDFT reached a peak of 10.00+/-3.56 N/kg at 60.7+/-5.6% of stance in Group 1 and 6.41+/-1.37 N/kg at 79.2+/-9.6% of stance in Group 2. CONCLUSIONS: DDFT force in Group 2 laminitic ponies was much reduced until late stance, when it neared normal values. POTENTIAL RELEVANCE: Further studies of ponies with rotation of the DP as a sequel to laminitis should assist farriery aimed at reducing the force in the DDFT through the breakover phase of stance to protect damaged dorsal laminae. 相似文献
6.
Christian Gosch Richard Alexander Gottsberger Karl Stich Thilo Christopher Fischer 《European journal of plant pathology / European Foundation for Plant Pathology》2012,134(4):835-845
Fire blight caused by the gram-negative bacterium Erwinia amylovora is a major disease of pome fruit like apple (Malus domestica) or pear (Pyrus communis). Detection of the pathogen is hampered by low titres usually being present during initial flower infection and the brief time frame for analysis to decide upon subsequent countermeasures. Here we describe a loop-mediated isothermal amplification of DNA (LAMP) assay for genomic DNA of Erwinia amylovora, which relies on a highly specific primer design that excludes amplification from typical DNA sources of the orchard biological system and from sample handling. The assay enables the fast detection of down to approximately 20?cfu of pure Erwinia amylovora or 100?fg genomic DNA (corresponding to approximately 25 E. amyolovora equivalents) per reaction within 45?min. Fast and reliable detection of E. amylovora in orchard samples by naked eye is achieved through a visual colour change indication with hydroxynaphthol blue. The assay avoids use of complex technical devices and is thus suitable for field testing. 相似文献
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Background, aim, and scope Contaminated mine drainage water has become a major hydrogeological and geochemical problem. Release of soluble metal contaminants
and acidity from mining sites can pose serious chemical risks to surface and groundwater in the surrounding environment, and
it is an important socio-economic factor addressed by working groups like SUITMA Morel and Heinrich (J Soils Sediments 8:206–207,
2008). The release of Zn and Pb from sulfide-bearing flotation residues of a small scale mine in Western Germany is investigated
with focus on metal transfer to soil solution. Total contents of the soil material as well as soil water sampled with suction
cups were analyzed. The influence of pH on leaching behavior was investigated with pHstat tests. Isotopic analyses helped assessing seepage water velocity. The aim of this study was the assessment of the environmental
behavior of zinc and lead caused by the weathering of sulfide-bearing mine tailings. Especially, we address in this paper
the dissolution of sphalerite (ZnS) in contrast to the well-known dissolution processes of pyrite (FeS2).
Materials and methods Total metal contents of the soil samples were analyzed by energy-dispersive X-ray fluorescence spectroscopy, total C concentration
was measured using a CHNS elemental analyzer. X-ray diffraction (XRD) spectra were recorded from powdered soil samples. Soil
water was sampled in nylon suction cups. Electrical conductivity (EC), pH, and temperature of the soil water samples were
measured in the field immediately after sampling. Major anions (F, Cl, NO2, NO3, SO4) were analyzed by ion chromatography, major cations (Ca, Na, K, Li) were analyzed by flame photometry, heavy metals (Zn,
Pb, Fe, Mn, and Mg) by flame atomic absorption spectrometry. Tritium was analyzed by liquid scintillation counting (LSC),
18O and 2H were analyzed by isotope ratio mass spectrometry (IRMS). pHstat tests were performed at four different pH values between 2 and 5.
Results Total Zn contents of the soil samples averaged 10 g kg−1, Pb contents averaged 2.5 g kg−1, Fe 22 g kg−1, S 8.0 g kg−1, and total carbon 4.0 g kg−1. Below 2-m depth, soil samples had neutral pH values. Toward the surface, pH decreased down to pH 5.4 in P1 and P3, and to
pH 5.9 in core P2, respectively. Dissolved contents of major ions (Mg, Ca, K, SO4, and HCO3) in the soil solution increased with depth. Metal concentrations (Fe, Mn, Zn) decreased with depth. The solution pH was neutral
to slightly alkaline in samples below 2 m and slightly acidic (pH 6) at 1 m depth. Tritium values are around 7 TU and correspond
to modern rain, i.e., after 1975. Stable isotope values plot on the global meteoric water line. The pHstat tests provide two kinds of information, the acid neutralization capacity after 24 h (ANC24) and the release of metals depending
on pH. The ANC24 increases linearly with decreasing pH from about 60 mmol(eq) kg−1 at pH 5 to about 460 mmol(eq) kg−1 at pH 2. Zn and Fe release show a strong increase with decreasing pH to 126 and 142 mmol(eq) kg−1, respectively. Pb release increases at pH <4 and Mn release at pH <5, both to about 10 mmol(eq) kg−1.
Discussion With an average of 10 g kg−1, this field site is highly enriched in Zn. In the oxidized topsoil, Zn concentrations are significantly lower than in the
anoxic subsoil. The distribution pattern of total Zn contents and soil pH values indicate that the topsoil, which is prone
to oxidation and acidification, is already depleted in Zn. Only in soil core P2, Zn (and Fe) contents in the topsoil were
higher than in the subsoil. Oxidation of the sulfidic material leads to redistribution into mobilizable species. High soil
water concentrations (10 to 15 mg L−1) can be found at acidic pH. The dominant Zn species in the soil solution is Zn2+. At neutral pH, Zn concentrations are below 0.001 mg L−1. During the soil passage, the contaminated seepage water enters the anoxic subsoil with pH buffering carbonates. Results
indicate that Zn is immobilized there. However, when the acid neutralization capacity is exhausted, a breakthrough of dissolved
Zn to the groundwater has to be expected. Lead averages 2.5 g kg−1 inside the flotation dump. In contrast to Zn, the first centimeters of the oxidized topsoil with high TOC contents show higher
Pb contents than the anoxic subsoil. About 80% of the cation exchange capacity in the topsoil is occupied by Pb. In contrast
to Zn, Pb is not abundant as aqueous species at slightly acidic pH. Values lower than pH 4 are necessary to mobilize Pb in
higher amounts, as pHstat experiments confirm. Hence, Pb is not expected to be leached out until the buffer capacity of the soil is exhausted.
Conclusions The environmental fate and behavior of Zn and Pb in the flotation dump is strongly depending on pH and redox conditions. Oxidation
of sphalerite leads to a transfer of Zn from immobile to easily mobilizable species. Sulfide oxidation leads to an acidification
of the topsoil where the buffer capacity is already exhausted due to the leaching of carbonates. At acidic pH, Zn is transferred
to the aqueous phase and leached to the subsoil where soil pH is neutral. Electron supply and the buffer capacity of the material
are found to be the main factors controlling the mobility of Zn. In contrast, the transfer of comparable amounts of Pb to
the aqueous phase requires pH values <4. Since Pb is enriched in the topsoil, not leaching to the groundwater, but direct
uptake (e.g., children, animals) and uptake by plants is the highest environmental risk. If the acidification of the soil
proceeds with the same rate as in the last 40 years, it will reach the bottom of the tailing in about 200 years and a breakthrough
of metals to the groundwater has to be expected.
Recommendations and perspectives The behavior of the different metals and their environmental impact depends on the different metal properties as well as on
external conditions, e.g. pH, redox conditions, buffer capacity, and groundwater recharge. To assess the future release of
metals from a flotation dump it is crucial to determine the main processes leading to acidification, the buffer capacity,
and heavy metal binding forms. The release of heavy metals to the groundwater could be prevented by liming or other buffering
techniques de Andrade et al. (J Soils Sediments 8:123–129, 2008).
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
Fuchs T Nathues H Koehrmann A Andrews S Brock F Klein G Beilage Eg 《Berliner und Münchener tier?rztliche Wochenschrift》2011,124(1-2):22-27
The objective of this study was to determine the effect of using a gonadotrophin releasing factor (GnRF) vaccine on growth performance of male pigs. Vaccinated pigs were compared with surgically castrated pigs and entire males under conventionally managed farm conditions. Male pigs were randomly assigned to three treatment groups: pigs surgically castrated during the first week of life (group "C", n=274), pigs immunised twice during the fattening period with a GnRF vaccine, the first when 13-14 weeks of age and the second when 20-21 weeks of age (group "V" n=280) and entire males (group "E", n=56). Average daily weight gain (ADG) was measured during the study. Additionally, feed conversion ratio (FCR) as defined by feed intake/weight gain and feed consumption was assessed during the fattening period. No difference in the ADG during the fattening period could be determined between "C" and "V". From the start of the study until slaughter at study day 160/173 the ADG in group "E" was lower (625 g/day; P) than in group "C" (681 g/day; P < 0.001) and group "V" (675 g/day; P < 0.01). The FCR during the fattening period until study day 160, three days before the first batch of pigs were slaughtered at 24-25 weeks of age, was higher in group"C" (2.72 kg feed intake/kg weight gain) compared with group "V" (2.44 kg feed intake/kg weight gain; P < 0.001) and group "E" (2.44 kg feed intake/kg weight gain; P <0.01). Pigs in group "V" performed similarly to those in group "E" until the second vaccination (day 135) after which time they showed a substantial increase in feed intake and ADG, while retaining an FCR advantage over group C. 相似文献