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41.
旅游者们越来越意识到交通的负面影响(包括噪音和其他类型的污染).繁重的交通会影响旅游目的地的娱乐或其他价值.对于旅游胜地以赢利为目的的管理者来说,交通方式和参观者的满意程度及再访愿望之间的关系正越来越重要.  相似文献   
42.
Growth performance and heavy metal uptake by willow (Salix viminalis) from strongly and moderately polluted calcareous soils were investigated in field and growth chamber trials to assess the suitability of willow for phytoremediation. Field uptakes were 2-10 times higher than growth chamber uptakes. Despite high concentrations of cadmium (≥80 mg/kg) and zinc (≥3000 mg/kg) in leaves of willow grown on strongly polluted soil with up to 18 mg Cd/kg, 1400 mg Cu/kg, 500 mg Pb/kg and 3300 mg Zn/kg, it is unsuited on strongly polluted soils because of poor growth. However, willow proved promising on moderately polluted soils (2.5 mg Cd/kg and 400 mg Zn/kg), where it extracted 0.13% of total Cd and 0.29% of the total Zn per year probably representing the most mobile fraction. Cu and Pb are strongly fixed in calcareous soils.  相似文献   
43.
ABSTRACT

On November 18, 1997, above-road particulate matter (PM) lidar (light detection and ranging) signals and heavy-duty (HD) and light-duty (LD) vehicle counts were simultaneously collected for 894 10-sec sampling periods at the Caldecott Tunnel in Orinda, CA, for the purpose of measuring the relative contributions of LD and HD vehicles to the PM lidar signal under real-world driving conditions. The relationship between the PM lidar signal and traffic activity (i.e., LD and HD traffic volumes) was examined using a time-series analysis technique, multilagged regression. The time-series model results indicate that the PM lidar signal in the current sampling period (PMt) depended on the level recorded in the previous three sampling periods (i.e., PMt-1, PMt-2, and PMt-3), the number of LD vehicles in the seventh past sampling period (LDt-7), and the number of HD vehicles measured 80 sec previous to the current sampling period (HDt-8). On a 10-sec period basis, the model results indicate that HD vehicles contributed, on average, 3 times more to above-road PM li-dar signals than did LD vehicles. The observed lag in the relationship between vehicle types and the lidar signal 20 m above the road suggests that resuspended road dust, rather than tailpipe exhaust emissions, was the main source of the detected PM. Detection of road dust at such heights above the road suggests the need for investigating the processes governing the vertical transport and recycling of PM over the road as a function of vehicle dynamics under a range of meteorological conditions.  相似文献   
44.
The radionuclides 210Po and 210Pb widely present in the terrestrial environment are the final long-lived radionuclides in the decay of 238U in the earth’s crust. Their presence in the atmosphere is due to the decay of 222Rn diffusing from the ground. The range of activity concentrations in ground level air for 210Po is 0.03-0.3 Bq m−3 and for 210Pb 0.2-1.5 Bq m−3.In drinking water from private wells the activity concentration of 210Po is in the order of 7-48 mBq l−1 and for 210Pb around 11-40 mBq l−1. From water works, however, the activity concentration for both 210Po and 210Pb is only in the order of 3 mBq l−1.Mosses, lichens and peat have a high efficiency in capturing 210Po and 210Pb from atmospheric fallout and exhibit an inventory of both 210Po and 210Pb in the order of 0.5-5 kBq m−2 in mosses and in lichens around 0.6 kBq m−2. The activity concentrations in lichens lies around 250 Bq kg−1, dry mass.Reindeer and caribou graze lichen which results in an activity concentration of 210Po and 210Pb of about 1-15 Bq kg−1 in meat from these animals. The food chain lichen-reindeer or caribou, and Man constitutes a unique model for studying the uptake and retention of 210Po and 210Pb in humans. The effective annual dose due to 210Po and 210Pb in people with high consumption of reindeer/caribou meat is estimated to be around 260 and 132 μSv a−1 respectively.In soils, 210Po is adsorbed to clay and organic colloids and the activity concentration varies with soil type and also correlates with the amount of atmospheric precipitation. The average activity concentration levels of 210Po in various soils are in the range of 20-240 Bq kg−1.Plants become contaminated with radioactive nuclides both by absorption from the soil (supported Po) and by deposition of radioactive fallout on the plants directly (unsupported Po). In fresh leafy plants the level of 210Po is particularly high as the result of the direct deposition of 222Rn daughters from atmospheric deposition. Tobacco is a terrestrial product with high activity concentrations of 210Po and 210Pb. The overall average activity concentration of 210Po is 13 ± 2 Bq kg−1. It is rather constant over time and by geographical origin.The average median daily dietary intakes of 210Po and 210Pb for the adult world population was estimated to 160 mBq day−1 and 110 mBq day−1, corresponding to annual effective doses of 70 μSv a−1 and 28 μSv a−1, respectively. The dietary intakes of 210Po and 210Pb from vegetarian food was estimated to only 70 mBq day−1 and 40 mBq day−1 corresponding to annual effective doses of 30.6 μSv a−1 and 10 μSv a−1, respectively. Since the activity concentration of 210Po and 210Pb in seafood is significantly higher than in vegetarian food the effective dose to populations consuming a lot of seafood might be 5-15 fold higher.  相似文献   
45.
Environmental monitoring of landscapes is of increasing interest. To quantify landscape patterns, a number of metrics are used, of which Shannon’s diversity, edge length, and density are studied here. As an alternative to complete mapping, point sampling was applied to estimate the metrics for already mapped landscapes selected from the National Inventory of Landscapes in Sweden (NILS). Monte-Carlo simulation was applied to study the performance of different designs. Random and systematic samplings were applied for four sample sizes and five buffer widths. The latter feature was relevant for edge length, since length was estimated through the number of points falling in buffer areas around edges. In addition, two landscape complexities were tested by applying two classification schemes with seven or 20 land cover classes to the NILS data. As expected, the root mean square error (RMSE) of the estimators decreased with increasing sample size. The estimators of both metrics were slightly biased, but the bias of Shannon’s diversity estimator was shown to decrease when sample size increased. In the edge length case, an increasing buffer width resulted in larger bias due to the increased impact of boundary conditions; this effect was shown to be independent of sample size. However, we also developed adjusted estimators that eliminate the bias of the edge length estimator. The rates of decrease of RMSE with increasing sample size and buffer width were quantified by a regression model. Finally, indicative cost–accuracy relationships were derived showing that point sampling could be a competitive alternative to complete wall-to-wall mapping.  相似文献   
46.
Widespread use of tributyltin (TBT) poses a serious environmental problem. Adsorption by black carbon (BC) may strongly affect its behavior. The adsorption of TBT to well characterized soot and two charcoals with specific surface area in the range of 62-111 m2 g−1 have been investigated with main focus on pH effects. The charcoals but not soot possess acidic functional groups. TBT adsorption reaches maximum at pH 6-7 for charcoals, and at pH > 6 for soot. Soot has between 1.5 and 15 times higher adsorption density (0.09-1.77 μmol m−2) than charcoals, but charcoals show up to 17 times higher sorption affinities than soot. TBT adsorption is successfully described by a new pH-dependent dual Langmuir model considering electrostatic and hydrophobic adsorption, and pH effects on TBT speciation and BC surface charge. It is inferred that strong sorption of the TBTOH species to BC may affect TBT toxicity.  相似文献   
47.
Abstract

Standard No. EN 15831:2004 provides 2 methods of calculating insulation: parallel and serial. The parallel method is similar to the global one defined in Standard No. ISO 9920:2007. Standards No. EN 342:2004, EN 14058:2004 and EN 13537:2002 refer to the methods defined in Standard No. EN ISO 15831:2004 for testing cold protective clothing or equipment. However, it is necessary to consider several issues, e.g., referring to measuring human subjects, when using the serial method. With one zone, there is no serial-parallel issue as the results are the same, while more zones increase the difference in insulation value between the methods. If insulation is evenly distributed, differences between the serial and parallel method are relatively small and proportional. However, with more insulation layers overlapping in heavy cold protective ensembles, the serial method produces higher insulation values than the parallel one and human studies. Therefore, the parallel method is recommended for standard testing.  相似文献   
48.
49.
The frequency and intensities of dust exposures in and near farm fields, which potentially contribute to high intensity human exposure events, are undocumented due to the transient nature of local dust plumes and the difficulties of making accurate concentration measurements. The objective of this study is to measure near-field spatial concentrations of the dust plumes emitted during tilling and harvesting of an irrigated cotton field outside of Las Cruces, NM (soil class: fine-loamy, mixed, superactive, thermic Typic Calciargid). A comparison of remote lidar measurements of plumes emitted from cotton field operations with in situ samplers shows a strong agreement between the two techniques: r2 = 0.79 for total suspended particulates (TSP) and r2 = 0.61 for particulate matter with diameter less than or equal to 10 microm (PM10). Plume movement was dependent on the short-term wind field and atmospheric stability. Horizontal spread rate of the plumes, determined from lidar measured Gaussian dispersion parameters, was less than expected by a factor of 7. Thus, in-plume downwind concentrations were higher than expected. Vertical dispersion was dependent on the rise of "cells" of warm air convecting off the soil surface. On a windy day, discing the field showed TSP and PM10 concentrations at the source itself of up to 176 microg m(-3) and 120 microg m(-3), respectively. These resulted in in-plume peak TSP concentrations of about 1.22 microg m(-3) at 10 m downwind and 0.33 microg m(-3) at 100 m downwind. The measured concentrations highlight a potential exposure risk to people in and around farming operations.  相似文献   
50.
In public debate GMPs are oftenreferred to as being unnatural or a violationof nature. Some people have serious moralconcerns about departures from what is natural.Others are concerned about potential risks tothe environment arising from the combination ofhereditary material moving across naturalboundaries and the limits of scientificforesight of long-term consequences. To addresssome of these concerns we propose that anadditional element in risk assessment based onthe concept of familiarity should beintroduced. The objective is to facilitatetransparency about uncertainties inherent inthe risk assessment of the GMP. Familiarityconventionally involves data and experiencerelating to the plant species and the ecosystemin question. We would like to extend thisconcept to the molecular level of plantbreeding and suggest that GMP characteristicsshould be compared to a reference baselinedetermined by conventional breeding techniques.Three GMPs are ranked according to familiarityat the plant and ecosystem level and themolecular level. The approach may help tointegrate discussion of the scientificarguments and moral questions raised in thedebate about GMOs by providing an operationalscheme within which moral concerns are broughtwithin the framework of science-based riskassessment.  相似文献   
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