排序方式: 共有24条查询结果,搜索用时 15 毫秒
1.
Jacob Carstensen Daniel J. Conley Erik Bonsdorff Bo G. Gustafsson Susanna Hietanen Urzsula Janas Tom Jilbert Alexey Maximov Alf Norkko Joanna Norkko Daniel C. Reed Caroline P. Slomp Karen Timmermann Maren Voss 《Ambio》2014,43(1):26-36
Hypoxia has occurred intermittently over the Holocene in the Baltic Sea, but the recent expansion from less than 10 000 km2 before 1950 to >60 000 km2 since 2000 is mainly caused by enhanced nutrient inputs from land and atmosphere. With worsening hypoxia, the role of sediments changes from nitrogen removal to nitrogen release as ammonium. At present, denitrification in the water column and sediments is equally important. Phosphorus is currently buried in sediments mainly in organic form, with an additional contribution of reduced Fe-phosphate minerals in the deep anoxic basins. Upon the transition to oxic conditions, a significant proportion of the organic phosphorus will be remineralized, with the phosphorus then being bound to iron oxides. This iron-oxide bound phosphorus is readily released to the water column upon the onset of hypoxia again. Important ecosystems services carried out by the benthic fauna, including biogeochemical feedback-loops and biomass production, are also lost with hypoxia. The results provide quantitative knowledge of nutrient release and recycling processes under various environmental conditions in support of decision support tools underlying the Baltic Sea Action Plan. 相似文献
2.
Voss KA Pohlman A Viswanathan S Gibson D Purohit J 《Environmental monitoring and assessment》2012,184(3):1603-1616
Environmental agencies across the United States have searched for adequate methods to assess anthropogenic impacts on the
environment. Biological assessments, which compare the taxonomic composition of an aquatic assemblage to relevant biocriteria,
have surfaced as an effective method to assess the ecological integrity of US waterbodies. In this study, bioassessment data
were collected and analyzed in conjunction with physical habitat and chemical stressor data for streams and rivers within
the San Diego basin from 1998 through 2005. Physical stressors such as sediment loading, riparian destruction, and in-stream
habitat homogenization affect many locations in the region. However, physical habitat measures alone were found to frequently
overestimate the biological integrity of streams in the region. Many sites within the San Diego Basin, although unaffected
by physical stressors, continue to exhibit low biological integrity scores. Sites with low biological integrity tend to possess
higher specific conductance and salinity compared to sites with high biological integrity. We suggest that one possible reason
for these differences is the source water used for municipal purposes. 相似文献
3.
As the primary interface with the human body during rear impact, the automotive seat holds great promise for mitigation of Whiplash Associated Disorders (WAD). Recent research has chronicled the potential influence of both seat geometrical and constitutive properties on occupant dynamics and injury potential. Geometrical elements such as reduced head to head restraint, rearward offset, and increased head restraint height have shown strong correlation with reductions in occupant kinematics. The stiffness and energy absorption of both the seating foam and the seat infrastructure are also influential on occupant motion; however, the trends in injury mitigation are not as clear as for the geometrical properties. It is of interest to determine whether, for a given seat frame and infrastructure, the properties of the seating foam alone can be tailored to mitigate WAD potential. Rear impact testing was conducted using three model year 2000 automotive seats (Chevrolet Camaro, Chevrolet S-10 pickup, and Pontiac Grand Prix), using the BioRID P3 anthropometric rear impact dummy. Each seat was distinct in construction and geometry. Each seat back was tested with various foams (i.e., standard, viscoelastic, low or high density). Seat geometries and infrastructures were constant so that the influence of the seating foams on occupant dynamics could be isolated. Three tests were conducted on each foam combination for a given seat (total of 102 tests), with a nominal impact severity of Delta V = 11 km/h (nominal duration of 100 msec). The seats were compared across a host of occupant kinematic variables most likely to be associated with WAD causation. No significant differences (p < 0.05) were found between seat back foams for tests within any given seat. However, seat comparisons yielded several significant differences (p < 0.05). The Camaro seat was found to result in several significantly different occupant kinematic variables when compared to the other seats. No significant differences were found between the Grand Prix and S-10 seats. Seat geometrical characteristics obtained from the Head Restraint Measuring Device (HRMD) showed good correlation with several occupant variables. It appears that for these seats and foams the head-to-head restraint horizontal and vertical distances are overwhelmingly more influential on occupant kinematics and WAD potential than the local foam properties within a given seat. 相似文献
4.
Martel PH Kovacs TG O'Connor BI Voss RH 《Environmental pollution (Barking, Essex : 1987)》1995,89(3):229-240
To better understand the relationships between pulp manufacturing processes and mixed function oxidase (MFO) enzyme induction in fish, a practical and standardized exposure procedure is required. This study was undertaken to develop a laboratory-based exposure procedure to quantify the relative MFO induction potencies of different types of pulp and paper mill effluents. One major consideration in developing the procedure was to ensure that the protocol was practical so that tests could be performed in a short time, with small volumes of effluents and using simple experimental conditions. A series of concentration-response and time-course experiments were conducted to find the minimum time and effluent concentration which could distinguish the ability of different effluents to cause significant MFO induction in rainbow trout in the laboratory. Experiments were also conducted to determine the effects of biotic and abiotic factors such as loading density, fish size and feeding regime. This study showed that the exposure of rainbow trout in the laboratory to 10% concentration of secondary-treated effluent for 96 h caused significant increases in hepatic MFO activity. The magnitude of MFO induction was comparable to other field and laboratory observations. While fish size, loading density and feeding regime were found to affect the test results, consistent responses within a laboratory using this protocol are possible, provided that these factors are standardized. Therefore, the short-term exposure approach described in this paper could be a relevant tool for assessing the ability of different types of pulp and paper mill effluents to cause MFO induction in fish. 相似文献
5.
Tracy K Kuczenski Donald R. Field Paul R. Voss Volker C. Radeloff Alice E. Hagen 《Journal of the American Water Resources Association》2000,36(1):215-228
ABSTRACT: Recurrent calls for integrated resource management urge that an understanding of human activities and populations be incorporated into natural resource research, management, and protection efforts. In this paper, we hypothesize that watersheds can be a valuable geography for organizing an inquiry into the relationship between humans and the environment, and we present a framework for conducting such efforts. The framework is grounded in the emerging field of landscape ecology and incorporates demographic theory and data. Demography has been advanced by technological capabilities associated with the 1990 Census. Employing Geographic Information System (GIS) tools, we couple Landsat Thematic Mapper (TM) land cover data with census‐derived housing density data to demonstrate the operation of our framework and its utility for better understanding human‐landscape interactions. In our investigation of the Kickapoo Watershed and two sub‐ watersheds, located in southwestern Wisconsin, we identify relationships between landscape composition and the distribution and social structure of human populations. Our findings offer insight into the interplay between people and biophysical systems. 相似文献
6.
Ulrich Struck Maren Voss Bodo von Bodungen Nicolai Mumm 《Die Naturwissenschaften》1998,85(12):597-603
15 N of bulk sediment, organic carbon concentrations, and abundances of exoskeletons of Bosmina
longispina
maritima in the sediment, the data are used to evaluate significant sources of nitrogen in the food web over the past century. Nitrogen
isotopic composition of bulk sediments ranges from 2.5 to 4.5?, that of exokeletons varies between 0.4 and 6.2?. The two are
positively correlated. A marked increase in the abundance of Bosmina since 1965 (from less than 500 specimen to more than 5000 specimen cm3 of sediment) is correlated with a significant increase in sedimentary organic carbon concentrations (from 4% to more than
10%). The isotopic data do not identify increased land-derived nitrate as the dominant nitrogen source fuelling the increase.
Instead, we postulate that nitrogen fixation by diazotrophic bacteria has been one of the larger sources of nitrogen in the
Baltic Sea, as it is today.
Received: 29 April 1998 / Accepted in revised form: 13 August 1998 相似文献
7.
Martel P Kovacs T Voss R Megraw S 《Environmental pollution (Barking, Essex : 1987)》2003,124(3):471-483
On three occasions between 1998 and 2000, freshwater mussels were collected by divers in Lake Memphremagog during the spring and transplanted to various locations in the St-Fran?ois River (Quebec, Canada). Mussel growth was monitored by comparing total weight and length at the beginning and end of the exposure period. In 1998, mussels were caged for 60 days at 10 stations, including locations receiving treated effluents from three pulp and paper mills. Overall, there was an apparent trend of increased mussel growth from upstream to downstream along the river. However, mussels caged downstream from the effluent discharge of a bleached kraft pulp and paper mill grew more slowly than those caged immediately upstream in the river. In 1999 and 2000, we further investigated the situation in the vicinity of this bleached kraft mill. The measurements again indicated that growth of mussels in the effluent plume from this mill was reduced in comparison to sites upstream. Overall, in terms of growth, the caged mussels responded both positively and negatively to different environmental conditions. Compared with other monitoring approaches used at these sites during the same period, the caged mussel experiment results were consistent with the trends observed with the benthic invertebrate survey but not with the trends observed for fish. 相似文献
8.
The Capital Region of Denmark tested the Multi Increment Sampling® (MIS) technology at 14 children's playgrounds in the region to assess whether the method provides representative test results and an improved foundation for risk assessment. The purpose of the investigation was to determine whether the previous uses of the playground areas have led to soil contamination that poses a health risk to its current users (children). The unpaved areas of the playgrounds were divided into decision units based on historical data along with the expected patterns of movement from its users. The samples from each unit consisted of 45 to 100 increments were collected from three depths within the upper one‐half meter. Furthermore, triplicate samples were taken from the upper sampling depth in at least one unit for quality control purposes. The investigation results showed excellent consistency between the pollution parameters and contamination levels in different decision units for each playground. The decision units where high levels of soil contamination exist coincide well with the previous site history. The MIS method has proven to be expensive and time consuming. However, in the future it will be easier to implement as we gain more experience with use of this method. ©2016 Wiley Periodicals, Inc. 相似文献
9.
Charles H. Peterson Stephen R. Fegley Christine M. Voss Sara R. Marschhauser Beth M. VanDusen 《Marine Biology》2013,160(3):629-640
Protecting eggs from predators is common practice in sea turtle conservation, but routine protection of hatchlings is not. Of 42 loggerhead hatchlings observed emerging from 10 nests on undeveloped Onslow Beach, North Carolina, 24 % were preyed on by ghost crabs. In experimental trials, ghost crabs similarly threatened and captured neonate freshwater sliders, supporting their substitution as proxy for threatened and endangered sea turtle hatchlings in field experiments testing density dependence. Exploiting natural long-shore variation in ghost crab density, we show that a 2.6-fold higher ghost crab density resulted in 5 times more nocturnal threat encounters with sliders and 3.4 times more slider captures. Sliders released in simulated group emergences experienced lower per capita capture risk by ghost crabs than solitary sliders, implying predator dilution. Non-independence of egg and hatchling depredation motivates consideration of merging sea turtle egg and hatchling stages when modeling and managing food web interactions. 相似文献
10.
西安作为汾渭平原地区最大的城市,大气颗粒物污染形势严峻.2017年夏季期间,在西安市浐灞生态园区运用气溶胶化学组分监测仪,对大气亚微米颗粒物中的非难挥发性组分(NR-PM1)进行了在线监测.观测期间NR-PM1的平均质量浓度为(30.1?±?15.4)μg???m?3.其中有机物含量最高,占NR-PM1总质量浓度的63%,其次为硫酸盐(18%)、铵盐(10%)和硝酸盐(9%).运用正交矩阵因子分析法共解析出两个主要因子,包括烃类有机组分(HOA)和含氧有机组分(OOA),分别占有机物总质量浓度的43%和55%.HOA主要由机动车排放贡献,而OOA主要由气态污染物的二次反应生成.气象因素对NR-PM1的浓度与化学组分的影响较为显著.高硝酸盐阶段发生在高湿、低温条件,可能是由氮氧化物的液相反应产生的.高硫酸盐阶段发生在低湿、高温条件,主要来自于大气光化学反应的贡献.该研究结果为西安及周边地区的空气污染治理决策提供重要的理论依据. 相似文献