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251.
This research evaluated the UNC passive aerosol sampler as a tool to measure particle mass concentrations and size distributions. The exposure scenario represented high concentrations and exposure periods of a few hours. Mass concentrations measured with the passive sampler were compared to concentrations measured using both a dichotomous sampler and an aerodynamic particle sizer (APS). In addition, the size distributions measured with the passive sampler were compared to those measured using the APS. Mass concentrations measured using the dichotomous sampler and the APS agreed well. The passive sampler tracked, but tended to overestimate, mass concentrations measured by the other two instruments. Size distributions measured with the passive sampler followed the general pattern of those measured using the APS. Overall, the passive sampler demonstrated both its utility and its limitations in these tests. The concentration measurements and size distributions found using passive samplers were more variable than those of the other instruments, but generally followed the data taken using the other methods. The advantages of low cost and ease of use offset the limitations in data quality with the passive sampler; these advantages are particularly welcome for sampling situations where aerosol properties vary over space or time. 相似文献
252.
253.
Hillslope runoff and leaching studies, catchment-scale water quality measurements and P retention and release characteristics of stream bank and catchment soils were used to better understand reasons behind the reported ineffectiveness of riparian buffers for phosphorus (P) management in catchments with sandy soils from south-west Western Australia (WA). Catchment-scale water quality measurements of 60 % particulate P (PP) suggest that riparian buffers should improve water quality; however, runoff and leaching studies show 20 times more water and 2 to 3 orders of magnitude more P are transported through leaching than runoff processes. The ratio of filterable reactive P (FRP) to total P (TP) in surface runoff from the plots was 60 %, and when combined with leachate, 96 to 99 % of P lost from hillslopes was FRP, in contrast with 40 % measured as FRP at the large catchment scale. Measurements of the P retention and release characteristics of catchment soils (<2 mm) compared with stream bank soil (<2 mm) and the <75-μm fraction of stream bank soils suggest that catchment soils contain more P, are more P saturated and are significantly more likely to deliver FRP and TP in excess of water quality targets than stream bank soils. Stream bank soils are much more likely to retain P than contribute P to streams, and the in-stream mixing of FRP from the landscape with particulates from stream banks or stream beds is a potential mechanism to explain the change in P form from hillslopes (96 to 99 % FRP) to large catchments (40 % FRP). When considered in the context of previous work reporting that riparian buffers were ineffective for P management in this environment, these studies reinforce the notion that (1) riparian buffers are unlikely to provide fit-for-purpose P management in catchments with sandy soils, (2) most P delivered to streams in sandy soil catchments is FRP and travels via subsurface and leaching pathways and (3) large catchment-scale water quality measurements are not good indicators of hillslope P mobilisation and transport processes. 相似文献
254.
Vanessa E. Melin David W. Johnstone Felicia A. Etzkorn Terry C. Hrubec 《Environmental monitoring and assessment》2014,186(6):3717-3724
Disinfection by-products (DBPs) arise when natural organic matter in source water reacts with disinfectants used in the water treatment process. Studies have suggested an association between DBPs and birth defects. Neural tube defects (NTDs) in embryos of untreated control mice were first observed in-house in May 2006 and have continued to date. The source of the NTD-inducing agent was previously determined to be a component of drinking water. Tap water samples from a variety of sources were analyzed for trihalomethanes (THMs) to determine if they were causing the malformations. NTDs were observed in CD-1 mice provided with treated and untreated surface water. Occurrence of NTDs varied by water source and treatment regimens. THMs were detected in tap water derived from surface water but not detected in tap water derived from a groundwater source. THMs were absent in untreated river water and laboratory purified waters, yet the percentage of NTDs in untreated river water were similar to the treated water counterpart. These findings indicate that THMs were not the primary cause of NTDs in the mice since the occurrence of NTDs was unrelated to drinking water disinfection. 相似文献
255.
256.
Amy Hinsley Tamsin E. Lee Joseph R. Harrison David L. Roberts 《Conservation biology》2016,30(5):1038-1047
The wildlife trade is a lucrative industry involving thousands of animal and plant species. The increasing use of the internet for both legal and illegal wildlife trade is well documented, but there is evidence that trade may be emerging on new online technologies such as social media. Using the orchid trade as a case study, we conducted the first systematic survey of wildlife trade on an international social‐media website. We focused on themed forums (groups), where people with similar interests can interact by uploading images or text (posts) that are visible to other group members. We used social‐network analysis to examine the ties between 150 of these orchid‐themed groups to determine the structure of the network. We found 4 communities of closely linked groups based around shared language. Most trade occurred in a community that consisted of English‐speaking and Southeast Asian groups. In addition to the network analysis, we randomly sampled 30 groups from the whole network to assess the prevalence of trade in cultivated and wild plants. Of 55,805 posts recorded over 12 weeks, 8.9% contained plants for sale, and 22–46% of these posts pertained to wild‐collected orchids. Although total numbers of posts about trade were relatively small, the large proportion of posts advertising wild orchids for sale supports calls for better monitoring of social media for trade in wild‐collected plants. 相似文献
257.
David P. Novello 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1288-1295
Title V of the Clean Air Act requires tens of thousands of air pollution sources to obtain an operating permit incorporating all applicable requirements under the Act. EPA recently promulgated its controversial Title V regulations, which establish the minimum elements for state permit programs. The new permit system is among the most important changes made by the 1990 Clean Air Act Amendments, and will significantly alter the way companies comply with air pollution requirements. Previously, the Act only required certain sources to obtain a new source review permit before constructing or modifying the facility (although many states established operating permit systems on their own). Now, all states must adopt operating permit programs consistent with the minimum federal requirements, and submit them to EPA by November 1993. Even though EPA has established minimum requirements, these programs are likely to vary widely from state to state. 相似文献
258.
259.
David Sinclair Richard J. Countess Benjamin Y. H. Liu David Y. H. Pui 《Journal of the Air & Waste Management Association (1995)》2013,63(7):661-663
The diffusion battery, an assembly of circular tubes or rectangular channels, is one of the best devices available for measuring the size and size distribution of submicron aerosols in the diameter range 0.002 to 0.2 µ m. The performance of these batteries is known from molecular diffusion theory, but until now has not been checked experimentally in this size range because of the lack of the necessary monodisperse aerosols. Experimental measurements on singly charged monodisperse aerosols from 0.01 µm to 0.1 µ m are described using a General Electric and a Pollak condensation nucleus counter to measure the aerosol penetration through the stages of a set of portable diffusion batteries in series. Particle sizes in the range tested could be selected at will by adjusting the voltage of an electric mobility classifier. The fraction of aerosol of a given size passing through each battery stage was found to agree closely with the penetration calculated from molecular diffusion theory for that size. This shows that the theory is correct and confirms that the aerosol produced by the electric mobility classifier was monodisperse. In addition, it was found that the difference in penetration between a charged versus a neutralized aerosol was insignificant except for the smallest aerosols used. 相似文献