After the Fukushima Dai-ichi nuclear accident, many efforts were put into the determination of the presence of Cs,Cs, I, and other gamma-emitting radionuclides in the ocean, but minor work was done regarding the monitoring of less volatile radionuclides, pure beta-ray emitters or simply radionuclides with very long half-lives. In this study we document the temporal evolution ofI, U, and Pu isotopes (Pu and Pu) in seawater sampled during four different cruises performed 2, 3, and 4 years after the accident, and we compare the results to Cs collected at the same stations and depths. Our results show that concentrations ofI are systematically above the nuclear weapon test levels at stations located close to the FDNPP, with a maximum value of 790 × 10 at·kg, that exceeds all previously reported I concentrations in the Pacific Ocean. Yet, the total amount ofI released after the accident in the time 2011-2015 was calculated from the I/Cs ratio of the ongoing Cs releases and estimated to be about 100 g (which adds to the 1 kg released during the accident in 2011). No clear evidence of Fukushima-derivedU and Pu isotopes has been found in this study, although further monitoring is encouraged to elucidate the origin of the highest Pu/Pu atom ratio of 0.293 ± 0.028 we found close to FDNPP.

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In the current study, the photooxidation reaction of toluene (C7H8) was investigated in a Potential Aerosol Mass Oxidation Flow Reactor (PAM OFR). The hydroxyl radical (OH) exposure of toluene in the PAM OFR ranged from 0.4 to 1.4 × 1012 molec cm−3 s, which is equivalent to 3 to 12 days of atmospheric oxidation. A proton transfer reaction-mass spectrometer (PTR-MS) and a scanning mobility particle sizer (SMPS) were used to study the gas-phase products formed and particle number changes of the oxidation reaction in PAM OFR. The secondary organic aerosol (SOA) formed in the PAM OFR was also collected for off-line chemical analysis. Key gas-phase reaction products of toluene, including glyoxal, methyl glyoxal, unsaturated carbonyl compounds, and benzaldehyde, were identified by the PTR-MS. Second generation products, including acetic acid, formaldehyde, formic acid, and acetaldehyde, were also detected. By comparing the mass spectrums obtained under different OH exposures and relative humidity (RH), changes in the two parameters have minimal effects on the composition of gas-phase products formed, expect for the spectrum obtained at OH exposure of 0.4 × 1012 cm−3 s and RH = 17%, which is slightly different from other spectrums. SMPS results showed that particle mass concentration increases with increasing OH exposure, while particle number concentration first increases and then decreases with increasing OH exposure. This result probably suggests the formation of oligomers at high OH exposure conditions. Off-line chemical analysis of the SOA sample was dominated by C4 diacids, including malic acid, citramalic acid, and tartaric acid. The well-known toluene SOA marker 2,3-Dihydroxy-4-oxopentanoic acid, as well as 2,3-dihydroxyglutaric acid, which has not been identified in previous toluene photooxidation experiments, were also detected in the SOA sample. Our results showed good agreements with the results of previous smog chamber studies of toluene photooxidation reaction, and they suggested that using PAM OFR for studies of oxidation reaction of different VOCs can be atmospherically relevant.

The current study presents a detailed investigation of diesel vehicle emissions utilizing chassis dynamometer testing. Nitrogen oxides (NOx), total hydrocarbon (THC), carbon monoxide (CO), and particulate matter (PM) were chosen to be the targets of this study. The recruited vehicle fleet consists of 15 in-use diesel vehicles, spanning a wide range of emission standards, engine sizes, weight, model year, etc. The real-time measurement data collected in different tests, as well as the mass of PM collected on filters, are used to calculate the emission factors (EF) of vehicles under various driving conditions. Results show that in general, EFs of NOx, CO, THC, and PM of the recruited fleet span a wide range of value (NOx: 0.80 ± 0.34 g kg -1 to 60.28 ± 2.94 g kg -1 ; THC: 0.10 ± 0.04 g kg -1 to 5.28 ± 1.28 g kg -1 ; CO: below detection limits to 24.01 ± 8.48 g kg -1 ; PM: below detection limits to 2.47 ± 1.22 g kg -1 ). Further data analysis shows that the implementation of a higher emission standard has a significant effect on reducing the emission of pollutants, except for NOx. Driving conditions are also the important factors affecting the EFs of target pollutants. Besides, statistical analysis shows a significant correlation between EFs of NOx with the testing weight and the maximum engine power of the vehicle. Further investigation is recommended to explore the effect of maintenance of the vehicles to the vehicular emission.