BACKGROUND: Export to the deep sea has been found to be a relevant pathway for highly hydrophobic chemicals. The objective of this study is to investigate the influence of this process on the potential for long-range transport (LRT) of such chemicals. METHODS: The spatial range as a measure of potential for LRT is calculated for seven PCB congeners with the multimedia fate and transport model ChemRange. Spatial ranges for cases with and without deep sea export are compared. RESULTS AND DISCUSSION: Export to the deep sea leads to increased transfer from the air to the surface ocean and, thereby, to lower spatial ranges for PCB congeners whose net deposition rate constant is similar to or greater than the atmospheric degradation rate constant. This is fulfilled for the PCB congeners 101, 153, 180, and 194. The spatial ranges of the congeners 8, 28, and 52, in contrast, are not affected by deep sea export. With export to the deep sea included in the model, the spatial ranges of the heavier congener are similar to those of the lighter ones, while the intermediate congeners 101 and 153 have the highest potential for long-range transport. CONCLUSIONS: Transfer to the deep ocean affects the mass balance and the potential for LRT of highly hydrophobic chemicals and should be included in multimedia fate models containing a compartment for ocean water. 相似文献
With the popularity of refrigerants in the process industries, the potential safety problems caused by the use of refrigerants have attracted worldwide attention as people have realized their inherent explosion characteristics of refrigerants. This paper studied the explosion characteristics of refrigerant 2, 3, 3, 3–tetrafluoropropene (R1234yf) at different concentrations and initial pressures based on a 20 L experimental apparatus. The experimental results illustrated the peak overpressure of R1234yf increased with the rise of initial pressure. At a constant ambient temperature of 25 °C, the maximum rate of pressure rise and deflagration index showed an N-shaped trend with the increase of the refrigerant concentration from 6.8% to 10%. The maximum rate of pressure rise and deflagration index increased first and then decreased with the increase of the refrigerant concentration at atmospheric pressure, while they presented an M-shaped trend at pressurization condition. The peak overpressure, the maximum rate of pressure rise, and deflagration index reached 0.742 MPa, 4.04 MPa s−1, and 1.1 MPa.m.s−1 with a refrigerant concentration of 7.6%, respectively, which were less than those of refrigerant propane and difluoromethane (R32) at the optimal concentration. Furthermore, R1234yf exhibited better safety performance compared with refrigerant R32 in the same flammability classification. 相似文献
A sintering technology for preparing porous materials from sea bottom sediments was developed for use in water purification. The purpose of the present study was to develop methods for converting the sea bottom sediments dredged from Ago Bay into value-added recycled products. The sintered products fabricated at 400℃ were found to be very effective adsorbents for the removal of heavy metals. 相似文献
Objective: The primary purpose of this study was to examine the association between variations in visual behavior measures and subjective sleepiness levels across age groups over time to determine a quantitative method of measuring drivers' sleepiness levels.
Method: A total of 128 volunteer drivers in 4 age groups were asked to finish 2-, 3-, and 4-h continuous driving tasks on expressways, during which the driver's fixation, saccade, and blink measures were recorded by an eye-tracking system and the subjective sleepiness level was measured through the Stanford Sleepiness Scale. Two-way repeated measures analysis of variance was then used to examine the change in visual behavior measures across age groups over time and compare the interactive effects of these 2 factors on the dependent visual measures.
Results: Drivers' visual behavior measures and subjective sleepiness levels vary significantly over time but not across age groups. A statistically significant interaction between age group and driving duration was found in drivers' pupil diameter, deviation of search angle, saccade amplitude, blink frequency, blink duration, and closure duration. Additionally, change in a driver's subjective sleepiness level is positively or negatively associated with variation in visual behavior measures, and such relationships can be expressed in regression models for different period of driving duration.
Conclusions: Driving duration affects drivers' sleepiness significantly, so the amount of continuous driving time should be strictly controlled. Moreover, driving sleepiness can be quantified through the change rate of drivers' visual behavior measures to alert drivers of sleepiness risk and to encourage rest periods. These results provide insight into potential strategies for reducing and preventing traffic accidents and injuries. 相似文献