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Increasing mercury contents are reported from freshwater systems and fish in northern Europe and North America. Mercury input from soils is a major source with the leaching being affected by increased atmospheric mercury deposition compared to pre-industrial times and by other environmental conditions such as acid rain. The results of a mathematical model-calculation of vertical inorganic Hg(II) leaching in a Scandinavian iron-humus podzol under different atmospheric input rates of mercury are presented. Leaching under background rain conditions was calculated to be considerably stronger than under acid rain conditions. Increasing fractions of deposited soluble or solute atmospheric mercury were leached from the O f(h)-horizon with decreasing soil content of soluble mercury under acid rain conditions; this effect was less pronounced under background rain conditions. The steady state concentrations of soluble mercury of the upper soil horizons were calculated and compared with the actual concentrations of total (= soluble + insoluble mercury) and extractable (= estimate of soluble) mercury measured in these horizons. The results indicate that even if the deposition of airborne mercury to soil is strongly reduced, the total mercury content of the soil decreases only slowly. It may take decades or even centuries before a new steady state concentration of total mercury is established in the soil. The decrease of the mercury concentration in the O f(h)-horizon is probably largely dependent on the turnover of organic matter, binding most of the deposited airborne mercury in an insoluble form. Hence, present day mercury leaching is likely to be dominated by mercury deposited during former times and temporarily retained in an insoluble form in the organic matter. 相似文献
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J. VEENSTRA P. J. G. M. RIETRA J. M. COSTER C. P. STOUTENBEEK E. A. TER LAAK† O. L. M. HAENEN‡ H. H. W. DE GIER S. DIRKS-GO 《Aquaculture Research》1993,24(1):119-122
Abstract A 63-year-old man was admitted to hospital for septicaemia and severe metastatic skin infection, 24h after he had eviscerated fresh eels. V. vulnificus was isolated from his blood and wounds. The strain was indole negative, was ornithine decarboxylase positive and grew at 42°C. A strain of V. vulnificus with these characteristics was isolated in 1987 from diseased eels. The characteristics differed from those of V. vulnificus strains (biogroup 1) that have been reported from patients world-wide. V. vulnificus biogroup 1 was isolated from 3 of 11 seawater samples collected along the coast of the Netherlands, but indole negative strains of V. vulnificus were not isolated. We conclude that an indole-negative variant of V. vulnificus is pathogenic for eels and for human beings and that eels may transmit V. vulnificus to humans. 相似文献
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CERI E. SHERLOCK TIMOTHY S. MAIR FRERIK TER BRAAKE 《Veterinary radiology & ultrasound》2009,50(1):13-20
We report the use of low-field standing magnetic resonance imaging in the standing horse for the diagnosis of osseous lesions in the metacarpophalangeal (MCP) or metatarsophalangeal (MTP) joint that were not apparent using standard radiography. Thirteen horses were studied and all had thickening of the subchondral bone plate and abnormal signal intensity in the adjacent spongiosa in either the condyles of metacarpal/metatarsal III or the proximal phalanx or both. Abnormalities were characterized by diffuse decreased signal intensity on T1-weighting adjacent to the subchondral bone and within the spongiosa in at least two imaging planes; in the absence of increases in signal intensity in fat-suppressed images, this change was interpreted as bone sclerosis. Nine horses also had a diffuse decreased signal intensity on T2* -weighting in the same areas and five had a diffuse increase in signal intensity in fat-suppressed images in conjunction with a decrease in signal intensity on T1- and T2* -weighted images; the increase in signal intensity in fat-suppressed images was interpreted as fluid accumulation. Five horses had a focal area of change in signal intensity within the subchondral bone with apparent loss of definition between the subchondral bone and the articular cartilage. Eleven horses were available for follow up, of which eight were sound and three remained lame. We conclude that lameness originating from the MCP or MTP joint may be associated with osseous damage in horses of any signalment in the absence of radiographic changes. 相似文献
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L O BRANDSÆTER H FOGELFORS H FYKSE E GRAGLIA R K JENSEN B MELANDER J SALONEN P VANHALA 《Weed Research》2010,50(2):102-109
Brandsæter LO, Fogelfors H, Fykse H, Graglia E, Jensen RK, Melander B, Salonen J & Vanhala P (2010). Seasonal restrictions of bud growth on roots of Cirsium arvense and Sonchus arvensis and rhizomes of Elymus repens. Weed Research 50 , 102–109.
Summary
The success of weed management aimed at depleting the regenerative structures of perennial weeds depends largely on the sprouting activity of rhizome and root buds. Seasonal variation in sprouting of these buds on Cirsium arvense, Sonchus arvensis and Elymus repens was studied for plants collected from Denmark, Finland, Norway and Sweden. At 2‐week intervals from July to October, 5‐cm fragments of roots or rhizomes were cut from plants grown in buckets and planted into soil in pots, half of which were placed immediately into growth chambers at 18°C for 4 weeks. The other half of the pots were initially placed in a dark room at 2°C for 4 weeks before being transferred to the same growth chamber, also for 4 weeks. During the growth chamber period, the numbers of emerged shoots in each pot were counted weekly. The sprouting activity of C. arvense and E. repens was relatively uniform during this period and bud dormancy was not apparent. In all ecotypes of S. arvensis, innate bud dormancy developed during the latter part of the growing season. For all three species, differences in sprouting readiness were found among ecotypes. The results imply that C. arvense and E. repens are more likely to be controlled by mechanical measures in autumn than S. arvensis. 相似文献6.
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