Humic-like substances global levels and extraction methods in aerosols

Environmental Chemistry Letters - The abundance of humic-like substances in the atmosphere has received considerable attention since these substances play an important role in various atmospheric...     

Characterization of the genes involved in nitrogen cycling in wastewater treatment plants using DNA microarray and most probable number-PCR

To improve nitrogen removal performance of wastewater treatment plants (WWTPs), it is essential to understand the behavior of nitrogen cycling communities, which comprise various microorganisms. This study characterized the quantity and diversity of nitrogen cycling genes in various processes of municipal WWTPs by employing two molecular-based methods:most probable number-polymerase chain reaction (MPN-PCR) and DNA microarray. MPN-PCR analysis revealed that gene quantities were not statistically different among processes, suggesting that conventional activated sludge processes (CAS) are similar to nitrogen removal processes in their ability to retain an adequate population of nitrogen cycling microorganisms. Furthermore, most processes in the WWTPs that were researched shared a pattern:the nirS and the bacterial amoA genes were more abundant than the nirK and archaeal amoA genes, respectively. DNA microarray analysis revealed that several kinds of nitrification and denitrification genes were detected in both CAS and anaerobic-oxic processes (AO), whereas limited genes were detected in nitrogen removal processes. Results of this study suggest that CAS maintains a diverse community of nitrogen cycling microorganisms; moreover, the microbial communities in nitrogen removal processes may be specific.

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Mobile monitoring along a street canyon and stationary forest air monitoring of formaldehyde by means of a micro-gas analysis system

A micro-gas analysis system (μGAS) was developed for mobile monitoring and continuous measurements of atmospheric HCHO. HCHO gas was trapped into an absorbing/reaction solution continuously using a microchannel scrubber in which the microchannels were patterned in a honeycomb structure to form a wide absorbing area with a thin absorbing solution layer. Fluorescence was monitored after reaction of the collected HCHO with 2,4-pentanedione (PD) in the presence of acetic acid/ammonium acetate. The system was portable, battery-driven, highly sensitive (limit of detection = 0.01 ppbv) and had good time resolution (response time 50 s). The results revealed that the PD chemistry was subject to interference from O(3). The mechanism of this interference was investigated and the problem was addressed by incorporating a wet denuder. Mobile monitoring was performed along traffic roads, and elevated HCHO levels in a street canyon were evident upon mapping of the obtained data. The system was also applied to stationary monitoring in a forest in which HCHO formed naturally via reaction of biogenic compounds with oxidants. Concentrations of a few ppbv-HCHO and several-tens of ppbv of O(3) were then simultaneously monitored with the μGAS in forest air monitoring campaigns. The obtained 1 h average data were compared with those obtained by 1 h impinger collection and offsite GC-MS analysis after derivatization with o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBOA). From the obtained data in the forest, daily variations of chemical HCHO production and loss are discussed.     

An analytical method to determine Henry's law constant for selected volatile organic compounds at concentrations and temperatures corresponding to tap water use

Henry's law constants (H) are needed to model human exposure to Volatile Organic Compounds (VOCs) in indoor air resulting from the use of tap water. This paper presents an experimental method to determine Hs for several common tap water pollutants at concentrations and temperatures used in household water. For 5 VOCs Henry's law constants were obtained simultaneously over the 25 degrees C to 45 degrees C temperature range, providing data on H beyond the currently available data (up to 35 degrees C). Henry's law constants were obtained as the ratio of equilibrium concentrations of VOCs in air and water, using simultaneous sampling from sealed bottles kept at constant temperatures. Air and water samples were concentrated by a purge-and-trap method, thermally desorbed from a Tenax trap, and analyzed with a gas chromatograph with an electron capture detector (GC-ECD). Experimental results agreed well with available literature data.     

Air Quality Standards National And International

The advantages and disadvantages of establishingworldwide air quality standards are reviewed. Inter-national standards would represent the best and mostadvanced procedures and might lead to improvementin standards in some countries where air quality isfar from adequate. International standards alsowould permit accurate comparisons of air pollutionamong countries and would provide a sound basis forcombatting pollution.     

Field validation of an active sampling cartridge as a passive sampler for long-term carbonyl monitoring

A carbonyl sampler originally designed for the active sampling method (Sep-Pak XPoSure) was used for long-term passive sampling, and its applicability as a passive sampler was examined through field experiments. The uptake rates of passive sampling were determined experimentally from collocated passive and active samplings for various sampling periods. The obtained uptake rates of formaldehyde, acetaldehyde, and acetone were 1.48, 1.23, and 1.08 mL/min, respectively. These uptake rates were consistent for a wide range of the sampling term (12 hr-2 weeks). Uptake rates of each carbonyl were proportional to the diffusion coefficients of each. Therefore, the ratios of diffusion coefficients were used to calculate the uptake rates of carbonyls for which the rates were not determined experimentally. Lower limits of determination were 2.16-17.5 microg/m3 for 2-week sampling. It was confirmed that 2-week monitoring of carbonyl concentrations up to 118-229 microg/m3 was possible. Relative standard deviations of the passive method generated from the repeatability test were 2-12.3% error for five samplings, and the recovery efficiencies were larger than 90%. Thus, the passive sampler was found to be highly suitable for long-term monitoring of carbonyl compounds.     

Trans-Pacific dispersal of loggerhead turtle hatchlings inferred from numerical simulation modeling

We used Lagrangian numerical simulations to examine the trans-Pacific dispersal processes of loggerhead turtle hatchlings. Ten thousand simulated particles were released from each of the three nesting regions in Japan and tracked for 5 years. Results showed many particles moving eastward, drifting in the Kuroshio Current followed by the Kuroshio Extension Current. However, no particles reached Baja California, a known feeding area, through passive processes, indicating that trans-Pacific transportation requires active swimming by turtles. The duration of the trans-Pacific dispersal was estimated to be at least 1.6–3.4 years, with some turtles drifting in the Kuroshio Countercurrent and remaining in the western Pacific even after 5 years. This indicates that as revealed by previous genetic studies, not all loggerheads always disperse along a trans-Pacific route. The findings showed that survival and expected growth rates varied widely according to ambient temperatures during drifting, which in turn depended on nesting location.     

Fertilization success and sexual behavior in male medaka, Oryzias latipes, exposed to tributyltin

We evaluated the effects of tributyltin (TBT), polychlorinated biphenyls (PCBs), and a mixture of TBT and PCBs on reproduction, gonadal histology, and sexual behavior in Japanese medaka (Oryzias latipes). We administered TBT (1 microg g(-1) body weight [b.w.] daily), PCBs (1 microg g(-1) b.w. daily), or both to medaka for 3 weeks. We assessed reproductive success during week 3 and the sexual behavior of male medaka after the exposure period. Fertilization success was significantly decreased in groups that received TBT. The profiles of fertility developed a bimodal distribution in the TBT and TBT+PCBs groups, and the numbers of males that performed "following" and "dancing" were significantly decreased in the TBT+PCBs group. The frequency of "dancing" also decreased after treatment with TBT, whereas fish that received PCBs only showed no difference in sexual behavior. Testes that had oocytes showed normal spermatogenesis, even though two of the five males treated with TBT+PCBs had some indication of testis-ova, which did not occur in any other group. Our results indicate that TBT, but not PCBs, affects sexual behavior and reproduction in medaka.