评价农场尺度上养分和微量元素动态变化的一个系统方法:以(O)jebyn奶牛场的研究为例

通过把全面的农田试验和矿质风化释放养分以及微量元素循环具体研究结合起来,用一个系统分析方法来评价农场尺度上的养分和微量元素可持续性.为了比较有机和常规农业管理方式,在瑞典北部的Ojebyn奶牛场进行了一个包括磷、钾和锌在内的农场尺度上的实例研究.通过结合不同的元素平衡法(农场总体尺度、畜舍尺度和农田尺度)以及进一步把这些方法应用到FARMFLOw模型,我们能够把子系统内质量流和库结合起来并建立子系统之间联系,来进行农场尺度上的预测.研究发现农场内部的元素流动大,而且农场有内部源(锌)和损失项(钾).在Ojebyn奶牛场形成并得到验证的方法是很有前途的,认为可以应用到任何农场.     

Prompt detection of alpha particles from 210Po: another clue to the origin of rock varnish?

Alpha particles have been measured coming from the surfaces of rocks covered with dark red-brown rock varnish, as well as rocks that appear to have little, if any, varnish. A pronounced peak at 5.3 MeV indicates the presence of 210Po, a short-lived natural-radioactive element. Surface activities for 33 samples range from 0.008 Bq/cm2 to 0.065 Bq/cm2. It is estimated that this nuclide is concentrated 10(11) times in these paper-thin coatings above its concentration in ground-level air. Gamma rays from the decay of 137Cs, a product of testing nuclear weapons some 50 years ago, were also detected. Analysis of samples of varnish stripped from the rock revealed traces of 239,240Pu and 238Pu. The presence of all of these isotopes strongly supports the theory that varnish films derive their building blocks from the atmosphere and, with time, all rocks in arid environments will become coated.     

A systems approach to assess farm-scale nutrient and trace element dynamics: a case study at the Ojebyn dairy farm

A systems analysis approach was used to assess farmscale nutrient and trace element sustainability by combining full-scale field experiments with specific studies of nutrient release from mineral weathering and trace-element cycling. At the Ojebyn dairy farm in northern Sweden, a farm-scale case study including phosphorus (P), potassium (K), and zinc (Zn) was run to compare organic and conventional agricultural management practices. By combining different element-balance approaches (at farmgate, barn, and field scales) and further adapting these to the FARMFLOW model, we were able to combine mass flows and pools within the subsystems and establish links between subsystems in order to make farm-scale predictions. It was found that internal element flows on the farm are large and that there are farm internal sources (Zn) and loss terms (K). The approaches developed and tested at the Ojebyn farm are promising and considered generally adaptable to any farm.     

Arzneimittel in der aquatischen Umwelt

The German Environmental Advisory Council evaluated German water protection policies in its last environmental report (2004) concluded that despite some great successes in this area there is still considerable need for action. Specifically, diffuse nutrient and chemical substances inputs remain an unsolved problem. The contamination of surface and groundwater with pharmaceuticals has been identified as an environmental risk increasing in pertinence. Pharmaceuticals and their metabolites are being detected in the whole aquatic environment, which they enter through sewage, soil contamination by agriculture, and waste storage facilities. Different pharmaceuticals have been tested for acute toxicity on various aquatic organisms, but almost nothing is known about chronic toxicity of these contaminants. This knowledge, however, is essential for estimating the ecotoxicological potential of pharmaceutical residues. In the opinion of the Environmental Council different strategies are necessary, to reduce the contamination of the environment with pharmaceuticals. Farmers should refrain from using pharmaceuticals for prophylactic purposes or from using hormonally or antibiotically active substances in livestock feed additives, so as to reduce inputs of veterinary drugs. As regards human medications, packaging should better correspond to appropriate dosage amounts, and environmentally responsible disposal measures should be followed. Still under discussion are a programme for the risk evaluation of existing pharmaceuticals and a ban on the use of sewage sludge in agriculture. In the future, improvement of sewage treatment facilities, for instances through membrane technologies, will offer further potential to reduce inputs of hazardous substances.     

Allelopathic potential of Cistus ladanifer chemicals in response to variations of light and temperature

Summary. Earlier studies have demonstrated the allelopathic potential of the exudate of Cistus ladanifer leaves, and have identified the compounds responsible for the effect. It is here shown that the effect of each of these compounds and their interactions on germination and seedling development varies depending on the light and temperature parameters to which they are subjected. The allelochemicals show a fairly heterogeneous response when studied separately, there being no general pattern to the behaviour. When they act conjointly, however, their activity is enhanced by high temperatures, and the greatest phytotoxicity in inhibiting both germination and seedling development is attained with high temperatures and long photoperiods. These results suggest that the environmental factors temperature and photoperiod may alter the allelopathic effect of Cistus ladanifer. Received 5 December 2001; accepted 11 March 2002.     

Hypoxia-induced structural changes in the diet of bottom-feeding fish and Crustacea

Interactive effects of three alternating normoxia-hypoxia cycles on benthic prey exploitation by mobile fish (spot, Leiostomus xanthurus; and hogchoker, Trinectes maculatus) and a burrowing crustacean (Squilla empusa) were investigated in the York River, Chesapeake Bay, Virginia, USA, in 1989. Predators collected in four depth strata (A: 5 to 10 m; B: 10 to 14 m; C: 14 to 20 m; D:>20 m) variously affected by hypoxia were separated into size classes (three for spot and two each for hogchoker and mantis shrimp) to examine potential ontogenetic influences in prey selection. The most severe effects of hypoxia on the benthos occurred in the two deepest strata (C and D) and decreased in shallower strata (B>A), with Stratum A never affected by low oxygen. Predators investigated exhibited dietary evidence of optimal prey exploitation during or immediately after hypoxic events. In most instances gut contents contained significantly larger, deeper-burrowing prey during periods of low oxygen than during alternating peroids of normal oxygen levels. Spot consumed a greater biomass (45 to 73%) of polychaetes than other prey, with crustaceans initially also constituting a main dietary component but decreasing in importance later in the study period. The deep-burrowing anemone, Edwardsia elegans, was an important prey species for spot, particularly in the lower depth strata affected by hypoxia. Prey consumed by 10-to 15-cm-long spot increased significantly in size during some hypoxic events, suggesting a sublethal effect of hypoxia on large benthic species. Polychaetes (primarily Glycera americana, Notomastis latericeus and Loimia medusa) were dominant dietary components in hogchoker, making up between 85 and 98% of the diet. Bivalve siphons became important prey for hogchoker in the three deepest strata and were only consumed after the August hypoxia. Stomach contents of mantis shrimp were difficult to identify in most instances due to the near complete mastication of consumed prey. Crustaceans were important prey initially but became less conspicuous in the diet subsequent to the July hypoxia event, when hydroids became more dominant. Overall, predator species exhibited optimal exploitation of moribund or slowly recovering benthos affected by hypoxia. The sublethal effects of hypoxia through increased availability of benthos to resident predators can have important consequences for energy flow in areas such as the York River which experience periodic low-oxygen cycles.