Mercury (Hg) Transport in a High Arctic River in Northeast Greenland     

Frank Rig��t  Mikkel P. Tamstorf  Martin M. Larsen  Jens S?ndergaard  Gert Asmund  Julie Maria Falk  Charlotte Sigsgaard 《Water, air, and soil pollution》2011,222(1-4):233-242

In a warming climate, mercury (Hg) pathways in the Arctic can be expected to be affected. The Hg transport from the high arctic Zackenberg River Basin was assessed in 2009 in order to describe and estimate the mercury transported from land to the marine environment. A total of 95 water samples were acquired and filtered (0.4 ??m pore size), and Hg concentrations were determined in both the filtered water and in the sediment. A range of other elements were also measured in the water samples. Hg concentrations in the filtered water were in general highest in the beginning of the season when the water came mainly from melted snow. THg concentrations in the sediment were in general relatively constant or slightly decreasing until mid-August, where after the concentrations increased. A principal component analysis separated the samples into spring, summer and autumn samples indicating seasonal characteristics of the patterns of element concentrations. The total amount of Hg in the sediment transported was estimated to 2.6 kg. Approximately 60% of the sediment-transported Hg occurred during a 24-h flood in the beginning of August caused by a glacial lake outburst flood. The total amount of transported dissolved Hg was estimated to 46 g, and 13% of this transport occurred during the 24-h flood. If it is assumed that the Hg transport by Zackenberg River is representative for the general glacial rivers in East Greenland, the total Hg transport into the North Atlantic from Greenland alone is approximately 4.6 tons year^?1 with an estimated annual freshwater discharge of ??440 km³.  相似文献   

Left ventricular M-mode prediction intervals in 7651 dogs: Population-wide and selected breed-specific values     

Lilith Carla Esser  Martin Borkovec  Alexander Bauer  Jens Häggström  Gerhard Wess 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2020,34(6):2242-2252

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Temporal changes in clinical and radiographic variables in dogs with preclinical myxomatous mitral valve disease: The EPIC study     

Adrian Boswood  Sonya G. Gordon  Jens Häggström  Martin Vanselow  Gerhard Wess  Rebecca L. Stepien  Mark A. Oyama  Bruce W. Keene  John Bonagura  Kristin A. MacDonald  Mark Patteson  Sarah Smith  Philip R. Fox  Karen Sanderson  Richard Woolley  Viktor Szatmári  Pierre Menaut  Whitney M. Church  M. Lynne O'Sullivan  Jean-Philippe Jaudon  Jan-Gerd Kresken  John Rush  Kirstie A. Barrett  Steven L. Rosenthal  Ashley B. Saunders  Ingrid Ljungvall  Michael Deinert  Eric Bomassi  Amara H. Estrada  Maria J. Fernandez Del Palacio  N. Sydney Moise  Jonathan A. Abbott  Yoko Fujii  Alan Spier  Michael W. Luethy  Roberto A. Santilli  Masami Uechi  Anna Tidholm  Christoph Schummer  Philip Watson 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2020,34(3):1108-1118

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Enhanced non-extractable residue formation of 14C-metalaxyl catalyzed by an immobilized laccase     

Jens Botterweck  Burkhard Schmidt  Jan Schwarzbauer  Roschni Kalathoor  Andreas Schäffer 《Biology and Fertility of Soils》2014,50(7):1015-1024

We studied the influence of an immobilized laccase from Trametes versicolor on non-extractable residue (NER) formation of the systemic fungicide ¹⁴C-metalaxyl in soil. We added the enzyme (130 mU/g DW) to soil sterilized by gamma irradiation and observed that the amount of NER (6.3 % of applied radioactivity) after 10 days of incubation was enhanced about twofold compared to the sterile soil without laccase addition. Residues formed within samples without enhanced enzyme activity were mainly bound via ester linkages to all fractions of humic matter, i.e., fulvic acids, humic acids, non-humines, and humines, respectively. In contrast, residues formed in presence of immobilized laccase were more strongly bound by covalent linkages such as ether and C-C bonds, especially to humic acids. After chemical degradation of the humic matter, it could be observed that all NER contained the first major transformation product, i.e., metalaxyl acid. The findings underline that the residue formation of metalaxyl in soil may be partly catalyzed by immobilized extracellular oxidative enzymes through oxidative coupling reactions within the humic matter.  相似文献   

Plant available soil water at sowing in Mediterranean environments—Is it a useful criterion to aid nitrogen fertiliser and sowing decisions?   总被引：1，自引：0，他引：1  

Carina Moeller  Senthold Asseng  Jens Berger  Stephen P. Milroy 《Field Crops Research》2009

In regions where rainfall is low and variable, water stored in the soil profile prior to sowing can alter yield expectation and hence management decisions. Thus, wheat farmers in Mediterranean regions may be able to benefit from knowing the amount of soil water at sowing by optimising their nitrogen (N) fertiliser management and by deciding on whether or not to sow a crop. We used the ASPIM-Nwheat model to explore how levels of plant available soil water (PAW) at sowing, N fertiliser rate, soil, site and season-type (below or above median rainfall) affected wheat yields at sites in the Mediterranean area of southwest Australia. Overall, the greatest influence on yield potential and the consequent N fertilisation requirement was season-type. The additional yield per mm PAW at sowing was generally higher in seasons with below median rainfall, except when yields were severely water-limited by below median rainfall of <222 mm combined with <40 mm PAW at sowing on light clay soil with 109 mm plant available water capacity (PAWC). Sowing was generally warranted; only on light clay soil with <10 mm PAW at sowing and below median rainfall of <222 mm was there an opportunity for a conditional sowing strategy. Scope for varying N fertiliser rates with PAW at sowing was limited to soils with higher PAWC (109 and 130 mm, respectively) in below median rainfall seasons at the wetter site (295 mm mean seasonal rainfall), and in both season-types at the drier site (225 mm mean seasonal rainfall). Only in these combinations, soil water at sowing modified the optimal N fertiliser rate for maximum average yield resulting in significant interactions between PAW at sowing and N fertiliser rates. Similar interactions were found for a site in the Mediterranean Basin and a site in the eastern Australian subtropics on soil with high PAWC (183 and 276 mm, respectively). In contrast, there was no benefit from modifying crop management based on PAW at sowing on soil with low PAWC (i.e. sandy soil) and/or under conditions of high in-season rainfall. The conditional N management approach becomes more viable as the proportion of water stored in the soil prior to sowing increases relative to total crop water use and as the PAWC of the soil increases. Knowledge of PAW at sowing × N fertiliser rate interactions in a particular soil × site × season-type context can help to identify sites where a more targeted N management dependent on amounts of PAW at sowing is potentially profitable.  相似文献   

甘蔗糖料压榨系统的现况及新技术方案     

Yangsheng Lu  Jens Thomsen 《广西蔗糖》2009,(4):25-29

本文论述了辊式压榨机的现状及其技术改进趋势,并分析了其固有缺陷,认为这是造成甘蔗汁液排放困难、重吸现象严重的根本原因,进而提出了改变压榨形式,延长压榨时间,采用外力排放糖汁等新的压榨技术方案,通过改善甘蔗糖料的压榨过程,强化固液萃取(渗出)分离过程,消除重吸现象,提高压榨效率,取代传统辊式压榨机,降低能耗,以满足清洁生产之需要.  相似文献   

Agricultural intensification in the Sahel – The ladder approach     

Jens B. Aune  André Bationo 《Agricultural Systems》2008

Agricultural intensification in the Sahel can be described as climbing a ladder. The capital, labour, management and institutional requirements increase when farmers climb the ladder, but the potential gains are also higher. The first step on this ladder are agricultural practices without any financial outlay but with increasing labour demand, such as organic fertilizer use, seed priming, water harvesting and harvesting grains at physiological maturity to improve fodder quality. The next step on the ladder is the use of micro-fertilising, popularly known as microdose, at the rate of 0.3 g NPK fertilizer per pocket in sorghum and millet. The following step is the development of improved crop/livestock systems characterized by use of higher rates of mineral fertilisers and manure, increasing cowpea density and improved animal fattening. The last step presented on the ladder is the development of more commercially orientated agriculture characterized by development of cash crops, milk production and/or agroforestry systems. Evidences from the field support the observation that farmers intensify their production in a sequential manner similar to the way described in this paper. The technologies presented can facilitate agricultural intensification by reducing the risks and minimising the cost in agricultural production.  相似文献   

Plagiotropism and auxin in Abies nordmanniana     

Veierskov B  Rasmussen HN  Eriksen B  Hansen-Møller J 《Tree physiology》2007,27(1):149-153

Main branches of Abies nordmanniana Spach. were examined through their first growth season from subapical buds around the leader bud to fully expanded shoots. Plagiotropism was evident in branch orientation, which was almost horizontal, as well as in the orientation of buds developing on the branches. Auxin transport capacity was predominantly basipetal (> 90%) and consistently higher in the middle part of the branch than in the distal and proximal ends. Auxin transport capacity was higher on the dorsal side of the branch during the short initial hyponastic growth phase, but the difference disappeared when the branch became horizontal. No dorsal-ventral differences could be detected in young horizontal branches in concentrations of indole acetic acid, cytokinins, gibberellins or abscisic acid. Branch orientation was unaffected by decapitation of the leader apex or by decapitation and replacement with exogenous auxin. However, decapitation resulted in a less plagiotropic bud arrangement on the branches, and auxin application to the leader bud scar counteracted this effect. Thus, a signal originating in the stem seems to be involved in regulating branch bud positioning, whereas the horizontal branch orientation must rely on a different mechanism, presumably autonomic within the branch.  相似文献   

土壤中山毛榉根系呼吸的碳素损失   总被引：7，自引：0，他引：7  

上官周平  邵明安 《土壤学报》2000,37(4):549-552

根系对植物生长发育过程有着重要的调控作用,其生理生化代谢过程是农学、生态学等学科研究的薄弱领域。植物生长发育过程受不同器官呼吸碳素损失的影响,根系是一个重要的碳素库［1］,其呼吸作用是生态系统碳素循环中重要的反馈途径之一［2,3］。由于很多研究侧重地上部分的研究,就环境因素对地下碳素库调控的了解还很有限,根系碳素量几乎占到植物总碳素量的50%［4,5］,但是,目前就植物根系呼吸碳素损失的研究方法,以及影响同化产物累积和分配的机制还有待研究［1］。以往多用溶液培养、气培和分离根系［6］来测定根系的呼吸速率或根系活力,这些测定结果与自然状态下根系的实际生理状况差异较大,难以确切掌握植物碳素平衡与分配。为此,我们设计了一种可动态测定土壤中植物根系呼吸碳素损失的方法,并在高CO2条件下植物13C吸收与分配模式研究中取得了较好的结果。  相似文献   

Self‐service traps inspected by avian and terrestrial predators as a management option for rodents     

Annika Schltelburg  Alexandra Plekat  Sonoko Bellingrath‐Kimura  Jens Jacob 《Pest management science》2020,76(1):103-110

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