Measurement Report: Optical properties and sources of water-soluble brown carbon in Tianjin, North China: insights from organic molecular compositions

Brown carbon (BrC) aerosols exert vital impacts on climate change and atmospheric photochemistry due to their light absorption in the wavelength range from near-ultraviolet (UV) to visible light. However, the optical properties and formation mechanisms of ambient BrC remain poorly understood, limiting the estimation of their radiative forcing. In the present study, fine aerosols (PM2.5) were collected during 2016–2017 on a day/night basis over urban Tianjin, a megacity in North China, to obtain seasonal and diurnal patterns of atmospheric water-soluble BrC. There were obvious seasonal but no evident diurnal variations in light absorption properties of BrC. In winter, BrC showed much stronger light absorbing ability since mass absorption efficiency at 365 nm (MAE365) (1.54 ± 0.33 m2 g−1), which was 1.8 times larger than that (0.84 ± 0.22 m2 g−1) in summer. Direct radiative effects by BrC absorption relative to black carbon in the UV range were 54.3 ± 16.9 % and 44.6 ± 13.9 %, respectively. In addition, five fluorescent components in BrC, including three humic-like fluorophores and two protein-like fluorophores were identified with excitation-emission matrix fluorescence spectrometry and parallel factor (PARAFAC) analysis. The lowly-oxygenated components contributed more to winter and nighttime samples, while more-oxygenated components increased in summer and daytime samples. The higher humification index (HIX) together with lower biological index (BIX) and fluorescence index (FI) suggest that the chemical compositions of BrC were associated with a high aromaticity degree in summer and daytime due to photobleaching. Fluorescent properties indicate that wintertime BrC were predominantly affected by primary emissions and fresh secondary organic aerosol (SOA), while summer ones were more influenced by aging processes. Results of source apportionments using organic molecular compositions of the same set of aerosols reveal that fossil fuel combustion and aging processes, primary bioaerosol emission, biomass burning, and biogenic and anthropogenic SOA formation were the main sources of BrC. Biomass burning contributed much larger to BrC in winter and at nighttime, while biogenic SOA contributed more in summer and at daytime. Especially, our study highlights that primary bioaerosol emission is an important source of BrC in urban Tianjin in summer.

LED-to-LED wireless communication between divers

<p class="Abstract">For military divers, having a robust, secure, and undetectable wireless communication system available is a fundamental element. Wireless intercoms using acoustic waves are currently used. These systems, even if reliable, have the defect of being easily identifiable and detectable. Visible light can pass through sea water. Therefore, light can be used to develop short-range wireless communication systems. To realize secure close-range underwater wireless communication, the Underwater Optical Wireless Communication (UOWC) can be a valid alternative to acoustic wireless communication. UOWC is not a new idea, but the problem of the presence of sunlight and the possibility of using near-ultraviolet radiation (near-UV) has not been adequately addressed in the literature yet. In military applications, the possibility of using invisible optical radiation can be of great interest. In this paper, a feasibility study is carried out to demonstrate that UOWC can be performed using near-ultraviolet radiation. The proposed system can be useful for wireless voice communications between military divers as well as amateur divers.</p>

OPTICAL PROPERTIES OF AMORPHOUS THIN FILMS OF SODIUM-TUNGSTEN OXIDE BRONZES

В работе измерены спектральные зависимости оптической плотности аморфных тонких пленок оксидной натрий-вольфрамовой бронзы тетрагональной структуры состава NaWO, конденсированной на стеклянные подложки, термостатированные при температурах 373,473 и 573 K, а так же отожженные на воздухе и в вакууме, и электрохромно окрашенных. В качестве исследуемой оптической характеристики была выбрана оптическая плотность D, пропорциональная, как известно, коэффициенту поглощения. Спектральные измерения пленок, осажденных на подложки в диапазоне температур 373,473 и 573 K показали однотипность спектральных характеристик, с пиком экситонного поглощения в ближнем ультрафиолете. Полоса минимального поглощения лежит в диапазоне длин волн 400÷460 нм, а примесного поглощения - широкой полосой в области 650 ÷1000 нм с максимумом в диапазоне 900÷1000 нм. Подобная спектральная характеристика и определяет сине-голубой цвет тонкой пленки на просвет. Изучение оптических свойств тонких пленок натрий-вольфрамовых бронз представляет собой актуальную задачу. The spectral dependences were measured of the optical density of amorphous thin films of sodium-tungsten oxide bronze of the tetragonal structure and the composition NaWO, condensed on glass substrates, thermostated at temperatures of 373, 473 and 573 K, as well as annealed in air vacuum, and electrochromically colored. The optical density D, which is proportional, as is known, to the absorption coefficient, was chosen as the studied optical characteristic. Spectral measurements of films deposited on substrates in the temperature range of 373, 473 and 573 K showed the same type of spectral characteristics, with a peak of the exciton absorption in the near ultraviolet. The band of minimum absorption lies in the wavelength range of 400÷460 nm, while that of the impurity absorption is a wide band in the region of 650÷1000 nm with a maximum in the range of 900÷1000 nm. This spectral characteristic determines the blue-blue color of a thin film in transmission. The study of the optical properties of thin films of sodium-tungsten bronzes is an urgent problem.

First Report of Diaporthe ambigua associated with dead arm disease on grapevine in Chile

Grapevine (Vitis vinifera L.) is one of the most important fruit crops in Chile based on economic value. Phaeomoniella chlamydospora and Botryosphaeriaceae species have been reported as the major causal agents associated with dieback symptoms in Chile commercial vineyards (Díaz and Latorre 2014; Besoain, 2018; Larach et al. 2020). Recently Eutypa lata has been reported attacking Chilean vineyards with dieback symptoms (Lolas et al. 2020). In this study, two commercial cv. Cabernet Sauvignon vineyards, located in O'Higgins Region of Chile, showing dead cordons, dead spur with a grayish color, canker, and vascular necrosis were sampled in fall 2018, with a high incidence of symptoms was observed. Four symptomatic wood samples were analyzed from these vineyards. Pieces of wood (<1 cm2) were taken from the advance zone of the canker lesions, disinfected with 70% ethanol, rinsed in sterile distilled water, dried, and transferred to two media in Petri plates, potato dextrose agar acidified with 0.5 ml of 96% lactic acid (APDA) and malt extract agar, and incubated for at least seven days at 24°C in darkness. From mycelium obtained from monosporic culture, two isolates were selected and morphologically identified as Diaporthe sp. To induce sporulation, these two isolates were grown in APDA under near-ultraviolet light (λ = 320 nm) at room temperature. After 30 days, the development of pycnidia was observed. Both Diaporthe sp. isolate presented alpha-conidia ellipsoidal with an obtuse apex, biguttulate (n=30) of 6.7 µm ± 0.33 µm x 3.3 µm ± 0.32 µm. No Beta-conidia or perhitecia were observed. DNA was extracted from the monosporic mycelium. The ribosomal internal transcribed spacer (ITS), β-tubulin (BT) gene, and elongation factor (EF) gene were amplified using ITS4/ITS5, Bt2a/Bt2b, and EF1-728F/EF1-986R primer pairs, respectively. PCR products were sequenced and identified as Diaporthe ambigua Nitschke (PUCV2140 and PUCV2141), showing 100% sequence identity with ITS MH864620.1, 99.8% with BT MG281142.1, and 100% with EF KC343738.1 sequences from D. ambigua. Sequences were deposited in GenBank (ITS: accession numbers MW301136, MW301137; BT: MW323445, MW323446 and EF: MW308305, MW308306). Two pathogenicity tests were performed with strains PUCV2140 and PUCV2141 using 2-year-old V.vinifera cv. Cabernet Sauvignon. In each test, three plants were used per isolate, considering one plant as an experimental unit. In the first test, a 5 mm mycelial plug from a 6-day-old APDA culture was inoculated using an oblique cut made in the bark with a sterile scalpel and done at the middle of the trunk. In the second test, the trial was done under the same described conditions previously, but in this case, one-year-old semi-lignified shoots were inoculated between two internodes, using mycelial plugs, one shoot for each plant. Injured plants but treated with sterile APDA plugs were used as controls. Plants were placed in natural conditions, and after three months from inoculations, plants showed a cortical canker and brown vascular lesions. Non-inoculated plants remained asymptomatic. The lengths of the cankers were 22.0 ± 1.8 mm and 10.5 ± 0.6 mm, after inoculations of the trunk and cane, respectively. The vascular lesions were 37.0 ± 3.3 and 18.0 ± 2.0 mm, in trunk and cane inoculations, respectively. D. ambigua was re-isolated and reidentified morphologically from the inoculated symptomatic plants, confirming Koch’s postulate. Also, the plants inoculated on the trunk showed premature leaf drop. To our knowledge, this is the first report of D. ambigua associated with dieback affecting grapevines in Chile. Previous D. ambigua was reported causing fruit rots (Auger et al. 2013; Díaz et al. 2017) and cordon dieback in kiwifruit (Díaz and Latorre, 2018), and stem canker and dieback in blueberry (Elfar et al. 2013) in Chile. This study reports a new species of fungi for Chile associated with the dead arm in vineyards. D. ambigua is a pathogen in essential crops in our country. Therefore, it is important to study its prevalence in the future.