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排序方式: 共有123条查询结果,搜索用时 15 毫秒
1.
A Permeable Reactive Barrier for Treatment of Heavy Metals 总被引:8,自引:0,他引:8
2.
A greenhouse experiment was conducted to examine the effects of salinity, nitrogen, and aeration on the growth of Spartina alterniflora Loisel. The experiment was conducted in a factorial arrangement of treatments with salt marsh substrate at three salinity levels (15, 30, 45‰), at two nitrogen levels (0 and 168 kg/ha) and at two aeration levels (zero and oxygen saturation). The maximum biomass was found in the low salinity, nitrogen enhanced, aerated treatment which had 11 times more biomass than the highest (45‰) salinity, nitrogen poor, unaerated treatment. the average effect of nitrogen over the three salinity levels was a 2.01, 1.47, 1.25, and 1.52 times increase in aerial biomass, density, height, and belowground biomass of the plants, respectively. The main effect of aeration was a 2.49, 2.01, 1.57, and 1.85 times increase in the same variables. The combination effect of aeration and nitrogen additions enhanced biomass by 453%. An increase in salinity from 15‰ to 45‰ decreased biomass, density, height and belowground biomass of S. alterniflora by 66, 53, 38, and 61%, respectively. The effect of salinity was more pronounced between 30 and 45‰ than it was between 15 and 30‰. N, P, K, Ca, Mg, Na, Fe, Mn, Zn, Cu, and S concentrations in the aerial living biomass were also examined. There was no evidence to suggest that elemental concentrations (on a per gram basis) were consistently correlated with increased or decreased growth. In relation to salinity, correlations between growth and elemental concentrations were negative while for nitrogen enhanced and/or aerated systems, the correlations were positive. 相似文献
3.
Regression models are developed and presented to predict dry mass (mg) from two linear dimensions (mm) for 17 benthic macroinvertebrate taxa common to littoral zones of New Zealand lakes. We also provide regression models to predict body length from head capsule width for the major insect taxa. Dry mass was best explained as a power function of all linear dimensions: M = aL b .Parameters are presented in the log10‐transformed linear form of this power function. Body length was a simple linear function of head capsule width for all insect taxa, hence parameters for these models are presented as untransformed values. We also provide family level models for the Chironomidae, and compare our chironomid body length‐mass model with other published Chrionomidae length‐mass models. There was a very high degree of variability in parameter values among published length‐mass models for the family Chironomidae (mean coefficient of variation for mass at length = 148%). We discuss the potential causes and implications of this variability. 相似文献
4.
The Myth of Location Privacy in the United States: Surveyed Attitude Versus Current Practices 总被引:1,自引:0,他引:1
In the United States, legal steps have been taken to protect personal privacy, which is viewed as an individual's fundamental right. Location privacy (i.e., protection of personal and location information), however, has not received equal attention in the legal system. Given the recent popularity of location-based services (e.g., cell phones), it is possible to obtain an individual's location information easily and precisely. An investigation of public perception of privacy in the United States indicated that survey responders (1) were unaware of legal implications of location privacy violation and (2) believed that there should be location privacy protection similar to that provided by the Health Insurance Portability and Accountability Act and the Family Educational Rights and Privacy Act. 相似文献
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Daniel G. Brown Rick Riolo Derek T. Robinson Michael North William Rand 《Journal of Geographical Systems》2005,7(1):25-47
The use of object-orientation for both spatial data and spatial process models facilitates their integration, which can allow exploration and explanation of spatial-temporal phenomena. In order to better understand how tight coupling might proceed and to evaluate the possible functional and efficiency gains from such a tight coupling, we identify four key relationships affecting how geographic data (fields and objects) and agent-based process models can interact: identity, causal, temporal and topological. We discuss approaches to implementing tight integration, focusing on a middleware approach that links existing GIS and ABM development platforms, and illustrate the need and approaches with example agent-based models. 相似文献
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Tracking eutrophication in Taihu Lake using the diatom record: potential and problems 总被引:7,自引:0,他引:7
Xuhui Dong Helen Bennion Rick Battarbee Xiangdong Yang Handong Yang Enfeng Liu 《Journal of Paleolimnology》2008,40(1):413-429
Taihu Lake is the third largest freshwater lake in China and has been experiencing eutrophication problems for several decades.
Diatoms in short sediment cores from three bays in northern Taihu Lake were studied in addition to 1-year of seasonal phytoplankton
samples in order to evaluate the rate and magnitude of nutrient enrichment. The dominant species found in the phytoplankton
samples appeared in high percentages in the surface sediment samples, suggesting that the latter faithfully record the modern
diatom flora. The diatom preservation status varied among the three cores, while in all cores the preservation deteriorated
with sediment depth. Due to the superior diatom preservation in the core from Mashan Bay, the fossil diatom record of this
core and an established diatom total phosphorus (TP) transfer function were used to reconstruct the nutrient history of Taihu
Lake. Diatom assemblages changed from Aulacoseira-dominated to other eutrophic planktonic species, such as Stephanodiscus minutulus, Cyclostephanos tholiformis, Cyclotella atomus, C. meneghiniana and S. hantzschii in ca. 1980. Diatom-inferred TP concentrations exhibited little change prior to 1980, with values around 50 μg/l. However,
after 1980 TP concentrations increased significantly and remained in excess of 100 μg/l, reflecting eutrophication of Taihu
Lake. Comparison with TP measurements in the water column from 1988 to 2004, as well as the analogue analysis among fossil
and modern samples, demonstrates that the diatom-TP inference model can reliably hindcast past TP concentrations. Therefore,
the baseline TP value of about 50 μg/l, can be used as a restoration target for Taihu Lake. However, due to the complexity
of this very large, shallow aquatic ecosystem, caution should be exercised when employing the diatom record to track eutrophication.
Further studies on the mechanism of diatom distribution, evolution and preservation are recommended for Taihu Lake. 相似文献
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