耕作土壤非交换性钾有效性的研究

采用２种化学连续提取法及连续耗钾实验。研究了几种耕作土壤非交换性钾释放特性及有效性。结果表明,供试土壤非交换性钾释放特性和有效性与粘土矿物密切相关。富含伊利石的土壤非交换性钾的释放量大,速率快,有效性高;黑麦草吸收该土壤的非交换性钾量及总吸钾量高,生物量大。而富含高岭石或蒙脱石的土壤非交换性钾有效性明显较低;非交换性钾的释放量和速率、黑麦草吸收该土壤的非交换性钾量、总吸钾量及生物量的均值分别仅为富含伊利石上壤的４６．９６％、４５．５０％、４１．６５％、４３．９０％和６７．５２％。供试土壤耗竭前期非交换性钾有效性高,供钾量大;黑麦草生长良好,生物量大。     

Why do nocturnal orb-web spiders (Araneidae) search for light?

The nocturnal orb-web spider Larinioides sclopetarius lives near water and frequently builds webs on bridges. In Vienna, Austria, this species is particularly abundant along the artificially lit handrails of a footbridge. Fewer individuals placed their webs on structurally identical but unlit handrails of the same footbridge. A census of the potential prey available to the spiders and the actual prey captured in the webs revealed that insect activity was significantly greater and consequently webs captured significantly more prey in the lit habitat compared to the unlit habitat. A laboratory experiment showed that adult female spiders actively choose artificially lit sites for web construction. Furthermore, this behaviour appears to be genetically predetermined rather than learned, as laboratory-reared individuals which had previously never foraged in artificial light exhibited the same preference. This orb-web spider seems to have evolved a foraging behaviour that exploits the attraction of insects to artificial lights. Received: 8 June 1998 / Received in revised form: 18 January 1999 / Accepted: 19 January 1999     

Meio- and macrofauna communities in three sandy beaches of the northern Adriatic Sea protected by artificial reefs

Interactions between meio- and macrofaunal assemblages and food availability were investigated in relation to tourism pressures on three beaches of the northern Adriatic Sea. All beaches were characterised by the presence of artificial reefs, freshwater inputs and tourism pressures. Beach sediments displayed high organic loads and low protein and chlorophyll a contributions to the bulk of the organic matter. Consequently, the organic matter was of mostly refractory composition and, thus, of scarce nutritional quality. Macrofaunal community structure and biomass were related to the quantity and nutritional quality of sedimentary organic matter, whereas meiofauna was apparently not. No relationships were found between physical variables and the metazoan communities. Most likely, the presence of artificial reefs reduced the physical impact of waves on the beach assemblages, whereas the presence of synergistic human impacts, including freshwater inputs and the tourism pressure, negatively influenced both the meio- and the macrofaunal assemblages.     

Decline in metallophytes in tertiary polluted floodplain grasslands in the Netherlands: experimental evidence for metal and nutritional changes in soil as driver factors

Metallophyte vegetation along the River Geul has been almost completely replaced by grasses during the last decades. Field investigations indicated that this was accompanied by higher alkalinity and phosphate availability in the soil, related to the closure of the metal industry and intensification of agricultural practices. An experiment with a full factorial design for phosphate and zinc availability indicated that the metallophytes Silene vulgaris and Thlaspi caerulescens did not grow on zinc-poor soils, irrespective of phosphate availability. The grass Holcus lanatus performed well on phosphate-rich soil, irrespective of zinc availability. An experiment with zinc-poor and zinc-rich floodplain soils confirmed the high zinc demand of the metallophytes T. caerulescens and Armeria maritima and the zinc independence of H. lanatus. A third experiment indicated that a reduced zinc availability due to liming affected only the metallophyte T. caerulescens; it had no effect on the growth of the grass Festuca rubra. This means that increasing alkalinity leads to a decrease in zinc availability, limiting the growth of at least some metallophyte species. An increase in phosphate availability stimulates growth in more competitive fast-growing grasses under zinc-rich as well as zinc-poor conditions.     

Remote sensing technology and land use analysis in food security assessment

ABSTRACT

Climate change and a rapidly growing human population have put ever greater strains on the global food system. Although the number of food insecure people in the world has reached a record low, changing land use and climate variability will threaten our ability to maintain this progress. Profound changes in the structure of economies around the world have affected agricultural production and how food is delivered to the consumer. This paper explores connections between land use, environmental change and food availability, access, and utilization. Each of these elements of food security has vulnerabilities to changing environmental conditions and land use that can be explored using satellite remote sensing observations. Technology is a key way environmental changes can be quantified and used in food security assessment.     

Recent Changes in Body Size of the Eurasian Otter <Emphasis Type="Italic">Lutra lutra</Emphasis> in Sweden

We studied geographical and temporal body size trends among 169 adult museum specimens of the Eurasian otter (Lutra lutra) collected in Sweden between 1962 and 2008, whose sex, year of collection, and locality were known. Skull size and body mass increased significantly in relation to the year of collection, and skull size (but not body mass) was significantly and negatively related to latitude, contrasting Bergmann’s rule and the trend found for Norwegian otters. Latitudinal differences in body size between the two countries may be due to differences in food availability. The temporal increase in body size among Swedish otters resembled that observed for Norway otters, though Swedish otters are smaller with respect to their Norwegian counterparts. Latitude and year represent a combination of environmental factors, including ambient temperature in the year of collection as well as the number of days of ice coverage. We replaced the above factors with mean annual temperature or the number of days of ice coverage, and found that each of these factors explains a similar proportion of the variation in body size as did latitude and year. We hypothesize that this temporal increase in body size is related to a combination of factors, including reduced energy expenditure resulting from increasing ambient temperature, and increased food availability from longer ice-free periods.     

Outdoor and indoor cadmium distributions near an abandoned smelting works and their relations to human exposure

The relationship of measured or modelled Cd concentrations in soil, house dust and available to plants with human urinary Cd concentrations were assessed in a population living around a Cd/Pb/Zn smelter in the UK. Modelled air concentrations explained 35% of soil Cd variation indicating the smelter contributed to soil Cd loads. Multi-variate analysis confirmed a significant role of biological and life-style factors in determining urinary Cd levels. Significant correlations of urinary Cd with soil, house dust and modelled plant available Cd concentrations were not, however, found. Potential reasons for the absence of clear relationships include limited environmental contact in urban populations; the role of undefined factors in determining exposure; and the limited spatial scope of the survey which did not sample from the full pollution gradient. Further, the absence of any significant relationship indicates that environmental measures provide limited advantage over atmospheric model outputs for first stage human exposure assessment.     

A Comparison of Three Federal Datasets for Thermoelectric Water Withdrawals in the United States for 2010

Historically, thermoelectric water withdrawal has been estimated by the Energy Information Administration (EIA) and the U.S. Geological Survey's (USGS) water‐use compilations. Recently, the USGS developed models for estimating withdrawal at thermoelectric plants to provide estimates independent from plant operator‐reported withdrawal data. This article compares three federal datasets of thermoelectric withdrawals for the United States in 2010: one based on the USGS water‐use compilation, another based on EIA data, and the third based on USGS model‐estimated data. The withdrawal data varied widely. Many plants had three different withdrawal values, and for approximately 54% of the plants the largest withdrawal value was twice the smallest, or larger. The causes of discrepancies among withdrawal estimates included definitional differences, definitional noise, and various nondefinitional causes. The uncertainty in national totals can be characterized by the range among the three datasets, from 5,640 m³/s (129 billion gallons per day [bgd]) to 6,954 m³/s (158 bgd), or by the aggregate difference between the smallest and largest values at each plant, from 4,014 m³/s (92 bgd) to 8,590 m³/s (196 bgd). When used to assess the accuracy of reported values, the USGS model estimates identify plants that need to be reviewed.     

重金属及养分元素在城市污泥主要组分中的分配及其化学形态

通过沉降／离心法将城市污泥区分为生物絮凝体、颗粒态、胶体及水溶态四种组分，并研究了重金属与养分元素在其中的分配及其各组分中重金属的化学形态，生物絮凝体组分占污泥干物质６８％，其次为颗粒态组分（占２３％），胶体及水溶态组分所占比例最少，有机Ｃ，总Ｎ，Ｐ，Ｋ及Ｃｕ，Ｐｂ，Ｚｎ，Ｃｄ，Ｈｇ，Ａｓ也主要分配在生物絮凝体组分中，从重金属在各组分中的形态分布看，重金属的化学活性依次为，污泥水溶性＋胶体组分〉生     

基于备件库存的舰炮使用可用度建模与仿真

使用可用度是舰炮战备完好性的重要度量标准,从三级备件库存结构和使用可用度着手,建立了舰炮使用可用度和备件保障度的关系模型,并利用蒙特卡罗法对给出的示例进行了仿真。仿真结果表明,该方法能够定量地描述使用可用度与备件库存之间的关系,找出了影响使用可用度的关键环节,为优化配置保障资源提供辅助决策。