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21.
The emissions of NO2 and HONO from the KNO3 photolysis in the presence of TiO2 were measured using a round-shape reactor coupled to a NOx analyzer. TiO2 played important roles in the emission flux density of NO2 (RNO2) and HONO (RHONO), depending on crystal structures and mass ratios of TiO2. RNO2 and RHONO significantly decreased with increasing the rutile and anatase mass ratios from 0 to 8 and 0.5 wt.%, respectively. Nevertheless, with further increasing the anatase mass ratio to 8 wt.%, there was an increase in RNO2 and RHONO. RNO2 on KNO3/TiO2/SiO2 had positive correlation with the KNO3 mass (1–20 wt.%), irradiation intensity (80–400 W/m2) and temperature (278–308 K), while it had the maximum value at the relative humidity (RH) of 55%. RHONO on KNO3/TiO2/SiO2 slightly varied with the KNO3 mass and temperature, whereas it increased with the irradiation intensity and RH. In addition, the mechanism for NO2 and HONO emissions from the nitrates photolysis and atmospheric implications were discussed. 相似文献
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Nanometer-size zero-valent iron (NZVI) is an efficient reducing agent, but its surface is easily passivated with an oxide layer, leading to reaction inefficiency. In our study, oxalate (OA) was introduced into this heterogeneous system of NZVI, which could form ferrioxalate complexes with the NZVI surface-bound Fe3+ and dissolved Fe3+ in the solution. Photolysis of ferrioxalate complexes can facilitate the generation of Fe2+ from Fe3+ and CO2?- radical, both species have strong reduction capacity. Hence, a “photo-oxalate-Fe(0)” system through sunlight induction was established, which not only prohibited the formation of a surface passivation layer, but also displayed a synergetic mechanism of ferrioxalate photolysis to enhance reduction, exhibiting remarkably higher degradation activity (several times faster) toward the model pollutant Cr(VI) than the mechanism with NZVI alone. Factor tests suggested that both NZVI dosage and OA content markedly affected the reduction rate. Low pH was beneficial to the reduction efficiency. Moreover, recyclability experiment showed that the reduction rate decreased from 0.21706 to 0.03977 min?1 after three cycles of reuse due to the NZVI losing reaction activity generally, but the system still maintained considerable reduction capacity. Finally, a mechanism was revealed whereby NZVI would transform to Fe oxides after the exhaustion of its reductive power, and the photolysis of ferrioxalate to promote the cycling of iron species played the predominant role in providing extra reduction ability. These features confirm that introduction of OA into Cr(VI) reduction by NZVI through sunlight induction is advantageous and promising. 相似文献
24.
Zeeshan Jave Cheng Liu Muhammad Fahim Khokhar Chengzhi Xing Wei Tan Muhammad Ahmed Subhani Abdul Rehman Aimon Tanvir 《环境科学学报(英文版)》2019,31(6):296-305
This study presents the Multi Axis Differential Optical Absorption Spectroscopy(MAXDOAS) measurements for Glyoxal(CHOCHO) in Beijing, China(39.95°N, 116.32°E). CHOCHO is the smallest compound of di-carbonyl group. As a primary sink of CHOCHO, its photolysis with NOx(oxides of nitrogen) results in the production of tropospheric ozone. Therefore,the focus of CHOCHO DOAS measurements is increasing in trend. We did the measurements from 09 May 2017 to 09 September 2017. The study was conducted to compare different retrieval settings in order to reveal best DOAS fit settings for CHOCHO;furthermore, effect of haze and non-haze days on CHOCHO concentration was examined.The root mean square of residual and Differential Slant Column density(dSCD) error was reduced when measurements were done with lower wavelength limit around 432–438 nm and upper intervals around 455–460 nm. Thus, lower wavelength intervals around432–438 nm and upper intervals around 457–460 nm were best for the retrieval of dSCDs for CHOCHO. Meteorological conditions like haze or non-haze days did not have significant effect on DOAS fit parameters. The CHOCHO vertical column densities range from 1.33 E +14 to 9.77 E + 14 molecules/cm2 during the study period with average of 6.16 E +14 molecules/cm2. The results indicated that during haze days CHOCHO concentration was higher because of lower rate of photolysis and atmospheric oxidation potential. Our results did not show any significant weekend effect on CHOCHO atmospheric concentration. 相似文献
25.
Yiqun Cao Qingxin Ma Biwu Chu Hong He 《Frontiers of Environmental Science & Engineering》2023,17(4):48
26.
有机痕量分析的样品处理包括从样品采集直到最终分离测定的全过程,在有机痕量分析中,必须严格防止所用器皿、化学试剂、溶剂等污染,减少系统误差。 相似文献
27.
Cui N Zhang X Xie Q Wang S Chen J Huang L Qiao X Li X Cai X 《Environmental pollution (Barking, Essex : 1987)》2011,159(2):609-615
Transformation products usually differ in environmental behaviors and toxicological properties from the parent contaminants, and probably cause potential risks to the environment. Toxicity evolution of a labile preservative, bronopol, upon primary aquatic degradation processes was investigated. Bronopol rapidly hydrolyzed in natural waters, and primarily produced more stable 2-bromo-2-nitroethanol (BNE) and bromonitromethane (BNM). Light enhanced degradation of the targeted compounds with water site specific photoactivity. The bond order analysis theoretically revealed that the reversible retroaldol reactions were primary degradation routes for bronopol and BNE. Judging from toxicity assays and the relative pesticide toxicity index, these degradation products (i.e., BNE and BNM), more persistent and higher toxic than the parent, probably accumulated in natural waters and resulted in higher or prolonging adverse impacts. Therefore, these transformation products should be included into the assessment of ecological risks of non-persistent and low toxic chemicals such as the preservative bronopol. 相似文献
28.
In vitro residual anti-bacterial activity of difloxacin, sarafloxacin and their photoproducts after photolysis in water 总被引:1,自引:0,他引:1
Souvik Kusari 《Environmental pollution (Barking, Essex : 1987)》2009,157(10):2722-2730
Fluoroquinolones like difloxacin (DIF) and sarafloxacin (SARA) are adsorbed in soil and enter the aquatic environment wherein they are subjected to photolytic degradation. To evaluate the fate of DIF and SARA, their photolysis was performed in water under stimulated natural sunlight conditions. DIF primarily degrades to SARA. On prolonged photodegradation, seven photoproducts were elucidated by HR-LC-MS/MS, three of which were entirely novel. The residual anti-bacterial activities of DIF, SARA and their photoproducts were studied against a group of pathogenic strains. DIF and SARA revealed potency against both Gram-positive and -negative bacteria. The photoproducts also exhibited varying degrees of efficacies against the tested bacteria. Even without isolating the individual photoproducts, their impact on the aquatic environment could be assessed. Therefore, the present results call for prudence in estimating the fate of these compounds in water and in avoiding emergence of resistance in bacteria caused by the photoproducts of DIF and SARA. 相似文献
29.
Anna Christiansson Johan Eriksson Daniel Teclechiel Åke Bergman 《Environmental science and pollution research international》2009,16(3):312-321
Background, aim, and scope Decabromodiphenyl ether (DecaBDE) is used as an additive flame retardant in polymers. It has become a ubiquitous environmental
contaminant, particularly abundant in abiotic media, such as sediments, air, and dust, and also present in wildlife and in
humans. The main DecaBDE constituent, perbrominated diphenyl ether (BDE-209), is susceptible to transformations as observed
in experimental work. This work is aimed at identifying and assessing the relative amounts of products formed after UV irradiation
of BDE-209.
Materials and methods BDE-209, dissolved in tetrahydrofuran (THF), methanol, or combinations of methanol/water, was exposed to UV light for 100
or 200 min. Samples were analyzed by gas chromatography/mass spectrometry (electron ionization) for polybrominated diphenyl
ethers (PBDEs), dibenzofurans (PBDFs), methoxylated PBDEs, and phenolic PBDE products.
Results The products formed were hexaBDEs to nonaBDEs, monoBDFs to pentaBDFs, and methoxylated tetraBDFs to pentaBDFs. The products
found in the fraction containing halogenated phenols were assigned to be pentabromophenol, dihydroxytetrabromobenzene, dihydroxydibromodibenzofuran,
dihydroxytribromodibenzofuran, and dihydroxytetrabromodibenzofuran. The PBDEs accounted for approximately 90% of the total
amount of substances in each sample and the PBDFs for about 10%.
Discussion BDE-209 is a source of PBDEs primarily present in OctaBDEs but also to some extent in PentaBDEs, both being commercial products
now banned within the EU and in several states within the USA. It is notable that OH-PBDFs have not been identified or indicated
in any of the photolysis studies performed to date. Formation of OH-PBDFs, however, may occur as pure radical reactions in
the atmosphere.
Conclusions Photolysis of decaBDE yields a wide span of products, from nonaBDEs to hydroxylated bromobenzenes. It is evident that irradiation
of decaBDE in water and methanol yields OH-PBDFs and MeO-PBDFs, respectively. BDE-202 (2,2′,3,3′,5,5′,6,6′-octabromodiphenyl
ether) is identified as a marker of BDE-209 photolysis.
Recommendations and perspectives BDE-209, the main constituent of DecaBDE, is primarily forming debrominated diphenyl ethers with higher persistence which
are more bioaccumulative than the starting material when subjected to UV light. Hence, DecaBDE should be considered as a source
of these PBDE congeners in the environment.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
30.
Chlorinated pesticides can contain impurities of dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and their precursors, as a result of various manufacturing processes and conditions. As precursor formation of PCDD/Fs can also be mediated by ultraviolet light (UV), this study investigated whether PCDD/Fs are formed when currently used pesticides are exposed to natural sunlight. Formulations containing pentachloronitrobenzene (PCNB; n = 2) and 2,4-dichlorophenoxyacetic acid (2,4-D; n = 1) were exposed to sunlight in quartz tubes, and the concentration of 93 PCDD/F congeners were monitored over time. Considerable formation of PCDD/Fs was observed in both PCNB formulations (by up to 5600%, to a maximum concentration of 57 000 μg ∑PCDD/F kg−1) as well as the 2,4-D formulation (by 3000%, to 140 μg ∑PCDD/F kg−1). TEQ also increased by up to 980%, to a maximum concentration of 28 μg kg−1 in PCNB, but did not change in the 2,4-D formulation. Assuming similar yields as observed in the present study as a worst case scenario the use of PCNB in Australia may result in the formation of 155 g TEQ annum−1, contributed primarily by OCDD formation. This warrants detailed evaluations on the contemporary release of PCDD/Fs to the environment after the use of pesticides. Changes in congener profiles (including the ratio of PCDDs to PCDFs (DF ratio)) suggest that pesticide sources of PCDD/Fs after sunlight exposure may not be recognized based on matching source fingerprints established from manufacturing impurities. These changes also provide preliminary insights into the possible formation routes and types of precursors involved. 相似文献