Changes in soil chemistry accompanying acidification over more than 100 years under woodland and grass at Rothamsted Experimental Station, UK   总被引：2，自引：0，他引：2  

L. Blake  K. W. T. Goulding  C. J. B. Mott  & A. E. Johnston 《European Journal of Soil Science》1999,50(3):401-412

We have examined the effect that acid deposition and other sources of acidity have had over the last 110–140 years on soil under woodland (Broadbalk and Geescroft Wildernesses) and grassland (Park Grass) comprising some of the Classical Experiments at Rothamsted Experimental Station. Changes in soil chemistry have been followed by analysing some of the unique archive of stored samples for pH, water-soluble and exchangeable base cations, aluminium, iron and manganese, exchangeable acidity, cation exchange capacity (CEC) and soluble anions. Proton balances and historical data show the importance of acid deposition to acidification and concomitant changes in the chemistry of the soil. The pH of the surface soil of Geescroft Wilderness has fallen from 6.2 to 3.8 since 1883. The decrease in the pH of the unlimed, unfertilized plot on Park Grass was less over a similar period (from pH 5.2 to 4.2), illustrating the significant effect of the woodland canopy on the interception of acidifying pollutants. The effect of increasing acidity on the soil chemistry of Geescroft Wilderness is seen in its decreasing base saturation and CEC, with base cations moving down the soil profile. Clay minerals are being irreversibly weathered, and Mn and Al progressively mobilized, so that today Al occupies 70% of the exchange complex in the surface soil. Even with present reductions in sulphur deposition critical loads for sulphur, nitrogen and acidity are still exceeded. Such semi-natural ecosystems are unsustainable under the current climate of pollution.  相似文献   

Efficacy of reduced rates of chlorantraniliprole seed treatment on insect pests of irrigated drill‐seeded rice     

James M Villegas  Blake E Wilson  Michael J Stout 《Pest management science》2019,75(12):3193-3199

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Penny ice cap cores, baffin island, canada, and the wisconsinan foxe dome connection: two states of hudson bay ice cover     

DA Fisher  RM Koerner  JC Bourgeois  G Zielinski  C Wake  CU Hammer  HB Clausen  N Gundestrup  S Johnsen  K Goto-Azuma  T Hondoh  E Blake  M Gerasimoff 《Science (New York, N.Y.)》1998,279(5351):692-695

Ice cores from Penny Ice Cap, Baffin Island, Canada, provide continuous Holocene records of oxygen isotopic composition (delta18O, proxy for temperature) and atmospheric impurities. A time scale was established with the use of altered seasonal variations, some volcanic horizons, and the age for the end of the Wisconsin ice age determined from the GRIP and GISP2 ice cores. There is pre-Holocene ice near the bed. The change in delta18O since the last glacial maximum (LGM) is at least 12.5 per mil, compared with an expected value of 7 per mil, suggesting that LGM ice originated at the much higher elevations of the then existing Foxe Dome and Foxe Ridge of the Laurentide Ice Sheet. The LGM delta18O values suggest thick ice frozen to the bed of Hudson Bay.  相似文献   

Atmospheric residence time of CH3Br estimated from the junge spatial variability relation     

JJ Colman  DR Blake  FS Rowland 《Science (New York, N.Y.)》1998,281(5375):392-396

The atmospheric residence time for methyl bromide (CH3Br) has been estimated as 0.8 +/- 0.1 years from its empirical spatial variability relative to C2H6, C2Cl4, CHCl3, and CH3Cl. This evaluation of the atmospheric residence time, based on Junge's 1963 general proposal, provides an estimate for CH3Br that is independent of source and sink estimates. Methyl bromide from combined natural and anthropogenic sources furnishes about half of the bromine that enters the stratosphere, where it plays an important role in ozone destruction. This residence time is consistent with the 0.7-year value recently calculated for CH3Br from the combined strength estimates for its known significant sinks.  相似文献   

The efficiency of sequential extraction of phosphorus in soil and sediment: insights from the oxygen isotope ratio of phosphate     

Lei  Xue-Tie  Zhang  Han  Chen  Min  Guo  Laodong  Zhang  Xi-Guang  Jiang  Zhao-Hua  Blake  Ruth E.  Chen  Zhi-Gang 《Journal of Soils and Sediments》2020,20(3):1332-1343

Journal of Soils and Sediments - Phosphorus (P) occurs in different chemical forms in soil and sediment, and they play different ecological and environmental roles. Thus, separation and...  相似文献   

The role of commercial crocodile farming in crocodile conservation     

D.K. Blake  J.P. Loveridge 《Biological conservation》1975,8(4):261-272

Commercial crocodile rearing stations in Rhodesia are described, including regulations which govern their operation. When crocodile eggs are collected from the wild a quota of juveniles equivalent to 5% of the number collected must be released at the age of 3 years. Figures for hatching success and juvenile growth on rearing stations compared with wild populations indicate that both these parameters are better on the rearing stations. The growth rate on a rearing station is twice as fast as in the wild. Data on juvenile survival on the rearing stations suggest that it is of the order of 50% to the age of 3 years. No comparative information is available for wild populations. Survival of station-reared crocodiles after release into the wild is good, although growth slows substantially. Juveniles for release are a valuable tool in management, for restocking suitable areas or supplementation of natural recruitment. Crocodile farms may provide an answer to future management of this species, and a ready source of breeding stock is available in ‘problem’ animals which are relocated rather than shot. Crocodile rearing and farming in developing countries could provide the incentive to maintain a renewable resource rather than to exploit and destroy existing populations.  相似文献   

The therapeutic efficacy and prophylactic activity of doramectin against Dictyocaulus viviparus in cattle     

NJ BARTON  PJ MITCHELL  FG HOOKE†‡  J. REYNOLDS§ 《Australian veterinary journal》1995,72(9):349-351

SUMMARY Three groups of 8, 4-month-old male Jersey or Jersey-cross calves were infected with 2400 Dictyocaulus viviparus L₃ larvae and either left untreated or injected subcutaneously with 200 μg/kg doramectin 5 or 25 days after infection (DAI). Lungworms were found in all untreated cattle (geometric mean = 49) at necropsy 39 or 40 DAI. None was found in any of the treated cattle. In a second experiment, groups of 6, 8-month-old calves were untreated or injected with 200 μg/kg doramectin 28, 21 or 14 days before each calf was challenged with 2700 D viviparus larvae. Lungworms were recovered at necropsy 32 to 34 DAI. The geometric mean worm burden in the untreated cattle was 550. This was reduced by 100%, 99.5% and 94.1% in calves treated with doramectin 14, 21 or 28 days, respectively, before infection. It was concluded that doramectin is a highly effective anthelmintic against D viviparus adult or L₄ infections of cattle, and that reinfection of treated cattle will be significantly reduced for at least 28 days after treatment.  相似文献   

Sagittal fractures of the third carpal bone in thoroughbred horses     

NJ KANNEGIETER  HILARY M BURBIDGE 《Australian veterinary journal》1988,65(12):402-403

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Radioimmunoassay for etorphine in horses with a 125I analog of etorphine     

C L Tai  C Wang  T J Weckman  M A Popot  W E Woods  J M Yang  J Blake  H H Tai  T Tobin 《American journal of veterinary research》1988,49(5):622-628

To improve the sensitivity and specificity of screening for etorphine in horses, an 125I-labeled etorphine analog was synthesized and an antibody to etorphine was raised in rabbits. A radioimmunoassay (RIA) for etorphine was developed, using these reagents. Bound and free 125I-labeled etorphine was separated by a double-antibody method that reduced interference from materials associated with equine urine. The 125I-labeled etorphine binding was rarely greater than 250 pg of background etorphine equivalents/ml in raw urine and was 100 pg/ml in hydrolyzed urine. The 125I-RIA was capable of detecting etorphine equivalents in urine above these background values. Etorphine equivalents were detected in equine urine samples for about 7 days after 4 mares were dosed with 0.22 microgram of etorphine/kg of body weight, IV. The stability of etorphine in urine from these mares was evaluated. Urine from these dosed mares was held in constant -20 C storage, and aliquots were repeatedly frozen and thawed. When analyzed for etorphine equivalents using an 125I-RIA, etorphine and its metabolites in urine samples were stable for less than or equal to 38 days if continuously frozen and also were resistant to repeated freezing and thawing.  相似文献   

Reconstruction of the parotid duct in a horse using an interposition polytetrafluoroethylene tube graft     

NJ KANNEGIETER  P ECKE 《Australian veterinary journal》1992,69(3):62-63

A Thoroughbred gelding was referred for treatment of a parotid duct fistula. This had developed after the referring veterinarian had excised a portion of the duct, and ligated the proximal end, as a means of treating a recurring sialocoele. This report describes the successful surgical reconstruction of the excised 15 cm portion of the parotid duct using an interposition polytetrafluoroethylene tube graft.  相似文献