Tạp chí Khoa học Tự nhiên Đại học Quốc gia Thành phố Hồ Chí Minh

Since 2013, the Ministry of Natural Resources and Environment published the revision of the “National Technical Regulation on Ambient Air Quality” (QCVN 05:2013/BTNMT), in which the fine particulate matter (PM2.5) was added to the QCVN. However, the status and the temporal variation of PM2.5 in Ho Chi Minh City (HCMC) have not been reported so far, especially based on the continuous and high time resolution measurements. The aim of this study was to analyze the status and the temporal variation of PM2.5 collected at the center of HCMC. Based on the composited PM2.5 data from the air monitoring station located at the University of Science, the average PM2.5 concentration was 28.0 ± 18.1 µg/m³ during 2013– 2017. The annual PM2.5 concentration in HCMC exceeded the acceptable limits of QCVN and WHO, highlighting a high human health risk. The PM2.5 concentrations showed the pronounced diurnal variation with the highest observed after the morning rush hour and the lowest during the midnight. In addition, a remarkable seasonal variation was observed with the highest and lowest PM2.5 occurring in dry and rainy seasons, respectively. This result highlighted the vital role of the rainfall events in reducing the PM2.5 level. Finally, from the analysis of the backward trajectories ending at the air monitoring station, we found that the air mass from the North and Northeast originating from China then passing through the areas (i.e. Binh Duong and Dong Nai provinces) with heavy industrial activities possessed a high PM2.5 level.

This article was retracted on 15 December 2021 by authors.   Euphorbia tirucalli has not been chemically studied much in Vietnam. This research described the isolation and elucidation of compounds isolated from the plant collected in Binh Thuan. Multiple chromatographic methods were applied, including normal phase silica gel column chromatography and thin-layer chromatography. Seven compounds were isolated and their chemical structures were elucidated by spectroscopic analysis as well as comparing their data with the ones in the literature. They are arjunolic acid (1), eriodictyol (2), quercitrin (3), afzelin (4), scopoletin (5), 3,3′,4- trimethylellagic acid (6), and gallic acid (7). Among them, compound 1 a major component was isolated for the first time in Euphorbia genus, while three compounds 2, 4, and 5 were isolated from this species for the first time.

The MIKE 21 FM model, developed by the Danish Hydraulic Institute, is a distributed system model that is used in hydrological calculations, water quality simulation, sediment transport calculations, resources and water environment in rivers, estuaries, coastal areas, and seas... This paper is an initial step in setting and establishing a set of model's parameters for simulating contaminant transport at the Dinh Vu coastal area, Hai Phong city under different scenarios. The model was calibrated and validated with the real data at 8 surface water quality monitoring sites at Hai Phong coastal area in 2014 and 2015. The result obtained by MIKE 21 HD for adjusters and good quality with specified Nash are 0.96 and 0.93, respectively. The relatively wrong number of Ecolab parameters are below 20 %.

The early Palaeozoic granitogneiss association in the Chu Lai - Kham Duc area (Quang Nam) is a large area of hundreds of km2, along southern of the East – West ductile deformation zones (Tam Ky – Phuoc Son fault zone), which is studied in detail in different geologic maps scales by the geologists, which is named Chu Lai complex. The five samples studied in detail are composed mainly of granitogneiss and biotite gneiss from the Chu Lai - Kham Duc area. The samples were crushed and large zircons were extracted. The in-situ zircon U–Pb geochronology was conducted on five samples (60 zircons in total) of age between 444 Ma and 426 Ma. These ages indicated the prolonged magmatic – tectonic period between the late Ordovician and middle Silurian in Kon Tum massif.

Solanum procumbens L. is a medicinal plant belonging to the Solanaceae family. In Vietnam, it is known as "Ca gai leo", and it cultivated in some tropical countries in China, Laos, Cambodia, and Vietnam. From the stem of the ethyl acetate extract of Solanum procumbens, we had isolated one anthraquinone (1), four polyphenols (2-5), and one indole (6). By spectroscopic methods as well as comparing with data in the literature, their chemical structures were elucidated as ziganein (1), benzoic acid (2), salicylic acid (3), 4-hydroxybenzaldehyde (4), vanillic acid (5), and indole-3-carbaldehyde (6). These compounds were isolated for the first time from the genus Solanum.

Green brackish algae Chaetomorpha sp. are easily found in shrimp ponds in Mekong Delta, Vietnam. They can also be co-cultured with shrimps in brackish water shrimp ponds to increase shrimp health and yield. Chaetomorpha sp. algae contain high amount of protein from 10 to 20% w/w db, including water soluble protein and alkaline-soluble protein with over 88% total protein. Dried material were used for protein extraction by using cellulase enzyme (Crestone Conc., Genecor) and NaOH solution. In this research, we optimize the extraction condition of protein from green algae Chaetomorpha sp. by using response surface methodology (RSM). At optimal extraction conditions, dried material was used for protein extraction by using cellulase enzyme (Crestone Conc., Genecor) with the enzyme dosage of 121 UI/g db at 400C during 90 mins. After extraction, the slurry was centrifuged to separate the algae biomass residue to extract the alkaline-soluble protein. The protein extraction yield by using cellulase enzyme was 38.921 mg/g db. After that the, algae biomass residue was extracted by a 1.2% NaOH solution for 78 mins at 500C. The protein extraction yield was 68.651 mg/g db. The total protein extraction yield was 105.755 mg/g db. The extraction yield was increased 10.33% when using the response surface methodology. Concentrated algae protein can be used as a good protein source for food and feed products.  

The aminolysis of poly(ethylene terephthalate) (PET) waste bottle with excess amount of aliphatic diamines, such as tetramethylenediamine (TMDA) and hexamethylenediamine (HMDA) without catalyst has been carried out. Each trimers and pentamers in the obtained products were isolated and characterized by FTIR, NMR, HPLC methods. Although an excess of diamine was employed, longer blocks of oligomers were still formed as minor products.

Rice husk is a common agricultural waste and an abundant source in Viet Nam. In terms of composition, rice husk is a silica-rich material (SiO2) so it can be used to prepare negative electrode materials for rechargeable Li-ion batteries. Recent processes of synthesizing the silica materials for the rechargeable batteries are often complex, expensive, and energy-intensive. In this study, KOH was used to treat rice husk ash to obtain SiO2/C porous composite materials. X-ray diffraction results (XRD) showed that the diffraction peak between 22o and 23o (2q ) was characterized of SiO2 material, and the other peaks around 43-44o was featured of carbon material. Scanning electron microscope image (SEM) showed the porous structure with the pore size 3-5 mm.Besides, the amorphous structure with coverage layers was also confirmed through the Transmission Electron Microscope (TEM) images. Preliminary electrochemical results demonstratedthat Li-ion coin cell using the SiO2/C anode material exhibited a high capacity of 1200 mAh/g at a discharge current of 1.0 A/g and maintained 1000 mAh/g after 100 cycles. SiO2/C materials prepared from rice husks were highly promising for battery application thanks to their low cost, stable performance, environmental friendliness, and easy expansion for production scale.

The problem of microplastic pollution (<5 mm) is becoming one of the biggest challenges facing countries. One of the problems is the export value of seafood products. Therefore, to assess the microplastic accumulation in clam (Meretrix lyrata), this study investigated the concentration of microplastics (MPs) in clam and their habitat in four clam culture beds (Tan Thanh, Ba Tri, Ganh Hao, and Ba Dong) in three consecutive months (from January to March 2020). The samples were analyzed by the method of oxidation of organic compounds and MPs flotation solution. The result showed that the concentrations of MPs in all three types of samples (seawater, surface sediment, and clam tissues respectively 36,66 ± 11.94 items 1 L- of seawater; 169.34 ± 42.01 items 1 kg- of soil; 13.79 ± 1.06 items individual- 10 g-, w.w) were markedly different between the four clam culture beds in three months (p-value <α = 0.05). Among which, the natural clam culture at Ganh Hao beach had the lowest concentration of MPs compared to Tan Thanh, Ba Dong, and Ba Tri cultured beds by households. Furthermore, the concentration of MPs in March was also the lowest compared to January and February. Hard plastic fibers were found the most (> 50%) compared to other types of plastic. The conclusion that microplastics have appeared everywhere in the environment and were found in the organism of clam, affecting the life of aquatic organisms.

Ho Chi Minh City plays a role as a leading economic and social center in the South of Vietnam, together with the urbanization, transportation system is being rapidly developing, resulting in an increase in emissions from these activities, and worsen the quality of the city. Therefore in this study, emission inventory for transportation has been conducted using the EMISENS model and then using GIS solfware to distribute the emissions in space in order to have the overall picture of air emissions of this city. The results showed that on-road activites especially from using motorcycles are the major contributer to air emissions in the city. On-road source in general accounting for 88% of NOx, 99% of CO, 79% of SO2, 99% of NMVOC, 88% of PM in total emissions from transportation activities. Key finding in this study is that hahour activities contribute up to 20% of total SOx and 10% of total PM. Other sources of transportation (airport, habour, bus station, rail way) only accounting for negligible amount of emissions Emission maps of transportation showed that central areas (District 1, District 10, District 3 and District 5) reached higer level of emissions than others. In additions, harbours areas as District 2, District 4 and District 7 where Saigon Port and Cat Lat Port are located in suffer the highest emissions of SO2, NOx and Dust.