Search

The development of mangrove forest environmental services plays a crucial role in human health, economic development, and the security of countries worldwide. This study aims to establish and validate a model for assessing the factors influencing the willingness-to-pay for mangrove forest environmental services. The proposed model comprises four key factors: attitude, subjective norm, perceived behavior control, and environmental knowledge. Data were collected by surveying 235 individuals from various households in Phu Long commune, Vietnam. The Partial Least Squares—Structural Equation Modeling (PLS-SEM) methodology was employed for data analysis. The research findings reveal that perceived behavior control significantly impacted residents’ willingness-to-pay, followed by attitude, environmental knowledge, and subjective norms. Furthermore, certain demographic characteristics such as gender and family size mediate the relationship between independent and dependent variables. Based on the obtained results, several policy recommendations are put forward.

The conservation and sustainable development of mangrove forests play a critical role in stabilizing livelihoods, creating employment opportunities for neighboring communities, and preserving valuable ecosystems. This study assesses the willingness-to-pay residents for the environmental services of mangrove forests. The Theory of Planned Behavior, along with demographic factors, is utilized to investigate the willingness-to-pay for mangrove forest services among residents in Phu Long commune, Hai Phong City, a coastal area in northern Vietnam. Data were collected through in-depth interviews with 235 households from four villages in Phu Long commune, employing a contingent valuation scenario and the payment card technique. The interval regression model is applied to analyze the influencing factors and the level of willingness-to-pay for five priority mangrove forest environmental services, which include: (i) greenhouse gas absorption and storage (climate change mitigation), (ii) support for biodiversity conservation, (iii) prevention of extreme weather events, (iv) scenic beauty services, and (v) habitat services for species. The Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) indices are used to select the most appropriate model. The estimated results from the interval regression model indicate that each household, on average, is willing to pay 327,792 Vietnamese dong (VND) per year for the five priority services. The analysis of factors reveals that attitudes, perceived behavioral control, and knowledge about mangrove forests have the most positive and significant impact on residents' willingness-to-pay. Based on these findings, several policy implications are proposed to enhance residents' willingness-to-pay for mangrove forest environmental services and promote the conservation and sustainable development of mangrove forests.

In this study, we evaluated the effect of probiotic bacteria Pediococcus pentosaceus supplemented at different inclusion levels in a control diet [basal diet containing 0.5% fructooligosaccharide (FOS)] on the growth performance, feed conversion ratio, immune response, and the disease resistance of whiteleg shrimp Litopenaeus vannamei juveniles against Vibrio parahaemolyticus. A control diet with 0.5% FOS but without P. pentosaceus supplementation (Control) was prepared. In addition, three other test diets were also formulated: control diet supplemented with P. pentosaceus at (i) 1 × 106 cfu g–1 diet (P1), (ii) 1 × 107 cfu g–1 diet (P2), or (iii) 1 × 108 cfu g–1 diet (P3). After a 60-day feeding trial, the experimental shrimps were challenged with V. parahaemolyticus. The results showed that dietary supplementation of P. pentosaceus significantly improved the growth performance and immune responses of L. vannamei juveniles. The juveniles that were fed with a P2 or P3 diet recorded the maximum increase in the final body weight, final length, weight gain, and survival rate. The total hemocyte counts, phenoloxidase, and lysozyme activity of shrimp fed with either of these two diets were significantly enhanced. The results also showed that juveniles fed with a P2 or P3 diet exhibited significantly lower mortality when challenged with V. parahaemolyticus. Overall results suggested that a combination of P. pentosaceus at the inclusion level of 1 × 107 cfu g–1 diet (P2) and 0.5% FOS could be considered as a potential synbiotic formulation for improving the growth, health, and robustness of L. vannamei.

From the ethyl acetate extract of the leaves of Amensiodendron chinense (Merr.) Hu (Sapindaceae), we isolated three known phenolic compounds: 4-hydroxy-3-methoxybenzaldehyde (1), methyl 3,4-dihydroxybenzoate (2), and 3,4-dihydroxybenzoic acid (3). We elucidated their chemical structures from the spectral data and compared them with those reported in the literature.

In this study, Bi0.5(Na1–xKx)0.5SnO3 (BNKS) ceramics (x = 0, 0.1, 0.2, 0.3, and 0.4) were fabricated via ultrasound wave before milling. The time of ball milling decreased from 20 to 1 h. The X-ray diffraction patterns show that the BNKS has a single-phase structure. When the potassium content increases, the phase structure of the ceramics changes from rhombohedral to tetragonal. When sintered at 1100 °C and x = 0.2, the ceramics’ physical properties are the best with the mass density of 5.59 g/cm3, the electromechanical coupling constants kp of 0,31 and kt of 0.27, the remanent polarization of 11.9 µC/cm; the dielectric constant εr of 1131, and the highest dielectric constant emax of 4800.

Soil salinity has a major impact on agricultural production. In a changing climate with rising sea-levels, low-lying coastal areas are increasingly inundated whereby saltwater gradually contaminates the soil. Drought prone areas may suffer from salinity due to high evapotranspiration rates in combination with the use of saline irrigation water. Salinity is difficult to monitor because soil moisture affects the soil’s spectral signature. We conducted Fourier-transform infrared spectroscopy on alluvial and sandy soil samples in the coastal estuary of the Red River Delta. The soils are contaminated with NaCl, Na2CO3 and Na2SO4 salts. In an experiment of salt contamination, we established that three ranges of the spectrum were strongly influenced by both salt and moisture content in the soil, at wavenumbers 3200–3400 cm−1 (2.9–3.1 µm); 1600–1700 cm−1 (5.9–6.3 µm); 900–1100 cm−1 (9.1–11.1 µm). The Na2CO3 contaminated soil and the spectral value had a linear relationship between wavelengths 6.9 and 7.4 µm. At wavelength 6.99 µm, there was no relationship between absorbance and soil moisture, but the absorbance was proportional to the salt content (R2 = 0.85; RMSE = 0.68 g) and electrical conductivity (R2 = 0.50; RMSE = 3.8 dS/m). The relationship between soil moisture and spectral absorbance value was high at wavelengths below 6.7 µm, resulting in a quadratic relation between soil moisture and absorbance at wavelength 6.13 µm (R2 = 0.80; RMSE = 5.2%). The spectral signatures and equations might be useful for mapping salt-affected soils, particularly in difficult to access locations. Technological advances in thermal satellite sensors may offer possibilities for monitoring soil salinity.

The concentrations and profiles of paraquat, a kind of herbicide, were studied in water samples taken from a stream flowing through five villages of Mai Chau province, the Northern Vietnam, during dry and rainy seasons. In this study, paraquat was found at almost the sampling sites and showed an average concentration for paraquat to be 30.69 μg/L and with a maximum of 134.08 μg/L. The herbicide concentration tended to be the highest on the dry season because of the least rainfall and also the highest evaporation rate of water in the stream. For risk assessment of human health, a hazard index (HI) value was calculated for estimating the risk towards the residents. HQ in the dry and rainy season is from 0.0001 to 0.2448 and from 0.0001 to 0.0279, respectively. The results showed a minimum risk; however, there are concerns toward the danger of long-term exposure to the residents from the stream that could affect their life quality.

Lanthanum has been doped onto the surface of the natural Pyrolusite for simultaneous removal of phosphate and fluoride in aqueous solution. The adsorbent characterization of the materials was observed by the SEM, BET, and XRD techniques. The dynamics and isotherms models of fluoride and phosphate adsorption, with respect to pH, pHPZC, adsorbent dose, and effect of coexisting ions, were studied. The results showed that lanthanum doped Pyrolusite ore (LDPO) relatively highly adsorbed amount of phosphate and fluoride from aqueous solution. Phosphate and fluoride removal efficiencies of LDPO are approximately 97% and 95%, respectively. Pseudo-first order for kinetic studies of phosphate and fluoride removal of the LDPO was observed with high correlations for fluoride but weak correlations for phosphate. However, pseudo-second order for kinetic studies was high correlation for both phosphate and fluoride. The phosphate and fluoride adsorption capacities of the LDPO significantly decreased with the existence of coions (sulfate, chloride, and nitrate) in the aqueous solution.

Academic library managers need to understand the work motivation of their staff and what inspires librarians to maximum productivity and enthusiasm as well as what prevents them from striving to achieve excellence. In a literature search, the authors found only one previous study of the work motivation of librarians in Vietnam, indicating a need for further research in this area. Using a self-designed questionnaire based on Abraham Maslow's hierarchy of needs, the authors surveyed and interviewed 220 librarians who work in 78 libraries to find out what factors affect their job motivation. The study also points out differences in motivations between academic librarians and other librarians and makes recommendations to help library managers improve staff performance.

The ambient air quality during COVID-19 lockdowns has been improved in many cities in the world. This study is to assess the changes in persistent organic pollutants in PM2.5 during the COVID-19 lockdown in Hanoi. Individual organic species in PM2.5 ((e.g., polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs), and organochlorine pesticides (OCPs)) were measured in an urban residential area in Hanoi from before the March 10th to April 22nd, 2020, including before the partial lockdown (BL) and the partial lockdown (PL) phases. During the PL phase, the concentration of Σ14PAHs and Σ28PCBs was reduced by 38 and 52% compared with the BL period, respectively. The diagnostic ratio method implied that the sources of PAHs within the PL phase had a less effect on traffic and industrial activities than in the BL phase. The characteristic ratio method indicated that PCBs were mixed by commercial product and combustion process in both the BL and the PL periods, however, the source of PCBs in the BL phase was influenced by municipal waste incineration more than those in the PL phase. The decreasing concentration of Σ20OCPs during the partial lockdown was attributed to the restriction of human activities during the quarantine period. The results suggested that the source of OCPs was probably derived from the usage of pesticides in current and, historical degradation or the transportation of pesticides from the soil to the atmosphere. [ABSTRACT FROM AUTHOR]

Community-Based Tourism (CBT) stands as a pivotal approach for sustainable tourism and poverty alleviation in marginalized Northern Vietnamese rural communities. In Hoa Binh province, a region rich in ethnic diversity engaged in CBT, a research gap exists concerning CBT governance. This study addresses this gap by exploring how CBT governance is organized in five villages of Mai Chau and Da Bac district, Hoa Binh province, by identifying relevant actors, institutions, and resources, and how it addresses the challenge of sustainable (tourism) development. To this end, a combination of semistructured interviews, focus groups, and observation were used. The results showed the complexity of CBT governance in Hoa Binh, and the many different manifestations of CBT in the different villages. The paper also analyzed factors that explain these differences, such as the historical or ethnic composition of the local community, biophysical conditions, community rules, and attributes of external factors. It also presents the complexity of the relationship between the development of CBT and sustainable development challenges. [ABSTRACT FROM AUTHOR]

Machining Carbon Fibre Reinforced Plastics (CFRPs) composites are typically accompanied by the appearance of machining damage which strongly impacts the structural integrity of composite parts during their service lives. Studying the correlation between machining damage and its affected factors has still been an open issue. Hence, it is necessary to do more research. This study focuses on investigating the influences of main process parameters and tool wear phenomenon in terms of machining length on the machining quality which was characterized by the surface roughness criterion, the ten-point max, Rz. A full factorial design of experiments was conducted including three levels of feed speed and two degrees of spindle speed. The results revealed that machining damage was mainly influenced by process parameters at a small machining distance, whereas at a longer machining distance, tool wear had a dominant effect on the machining quality than machining parameters. These findings could provide guidelines for selecting suitable machining parameters to enhance the machining quality of CFRP. [ABSTRACT FROM AUTHOR]

The SPOT-MAS assay "Screening for the Presence Of Tumor by Methylation And Size" detects the five most common cancers in Vietnam by evaluating circulating tumor DNA in the blood. Here, we validated its performance in a prospective multi-center clinical trial, K-DETEK. Our analysis of 2795 participants from 14 sites across Vietnam demonstrates its ability to detect cancers in asymptomatic individuals with a positive predictive value of 60%, with 83.3% accuracy in detecting tumor location. We present a case report to support further using SPOT-MAS as a complementary method to achieve early cancer detection and provide the opportunity for early treatment. [ABSTRACT FROM AUTHOR]

People all across the world, especially in Vietnam, have been motivated to make online purchases since the COVID-19 pandemic, which started in early 2020. Despite the problematic developments of the COVID-19 pandemic throughout the 2020–2021 period, Vietnam has experienced a considerable increase in e-commerce, both in terms of users and revenue, contributing considerably to national economic growth. The purpose of this study is to examine how COVID-19 affects Vietnamese customers' online purchasing decisions. We conducted a survey of 638 Vietnamese internet shoppers for this, and the results were analyzed using SPSS. The results show that attitudes, perceived ease of use, perceived usefulness, and subjective norms all positively and significantly impact customer purchase intention. The desire to make an online purchase, however, is negatively and negligibly impacted by perceived risk. Online purchasing behavior is positively influenced by the intention to buy online. The perceived risk of the COVID-19, in particular, significantly modifies the relationship between perceived usefulness and perceived usability and online shopping intention, but only marginally modifies the relationship between attitude, subjective norms, and perceived risk and online purchase intention. Using a combined Theory of Acceptance Model (TAM) and Theory of Planned Behaviors (TPB) model with COVID-19 as an external model variable, the study adds to the body of knowledge by providing empirical findings. [ABSTRACT FROM AUTHOR]

To reach the sustainable development goals on health management in Litopenaeus vannamei shrimp culture, Pediococcus pentosaceus AB01 was supplemented in shrimp diet. In this study, the control diet and three experimental diets containing P. pentosaceus AB01 (108, 109, 1010 CFU/g) were separately introduced to L. vannamei for a 28 days feeding trial. After the feeding trial, percent weight gain, feeding efficiency, and feed conversion ratio (FCR) were significantly elevated in L. vannamei administered with P. pentosaceus AB01 at 109 and 1010 colony‐forming unit (CFU)/g. Protease, amylase, and trypsin were found at higher levels in the probiotic‐supplied groups. The feeding of shrimps with P. pentosaceus AB01 significantly increased innate immune response and levels of related biochemical parameters in the haemolymph. After the white spot syndrome virus (WSSV) challenge, supplementation of P. pentosaceus AB01 had significant positive effects (p <.05) on survival rate, compared to that of the control diet. The higher resistance of L. vannamei to WSSV might have been due to alterations in the gut microbiome composition and upregulation of the Toll‐Like Receptor (TLR) signalling pathway. Hence, P. pentosaceus AB01 may be a promising alternative feed to promote growth rate, modulate microbiota composition, and enhance immunity in L. vannamei shrimp. [ABSTRACT FROM AUTHOR]

Covid-19 lockdowns have improved the ambient air quality across the world via reduced air pollutant levels. This article aims to investigate the effect of the partial lockdown on the main ambient air pollutants and their elemental concentrations bound to PM2.5 in Hanoi. In addition to the PM2.5 samples collected at three urban sites in Hanoi, the daily PM2.5, NO2, O3, and SO2 levels were collected from the automatic ambient air quality monitoring station at Nguyen Van Cu street to analyze the pollution level before (March 10th–March 31st) and during the partial lockdown (April 1st–April 22nd) with "current" data obtained in 2020 and "historical" data obtained in 2014, 2016, and 2017. The results showed that NO2, PM2.5, O3, and SO2 concentrations obtained from the automatic ambient air quality monitoring station were reduced by 75.8, 55.9, 21.4, and 60.7%, respectively, compared with historical data. Besides, the concentration of PM2.5 at sampling sites declined by 41.8% during the partial lockdown. Furthermore, there was a drastic negative relationship between the boundary layer height (BLH) and the daily mean PM2.5 in Hanoi. The concentrations of Cd, Se, As, Sr, Ba, Cu, Mn, Pb, K, Zn, Ca, Al, and Mg during the partial lockdown were lower than those before the partial lockdown. The results of enrichment factor (EF) values and principal component analysis (PCA) concluded that trace elements in PM2.5 before the partial lockdown were more affected by industrial activities than those during the partial lockdown. [ABSTRACT FROM AUTHOR]

We propose and develop a simple and cost‐effective method to fabricate surface enhanced Raman scattering (SERS) substrates for the trace detection of antibiotics. A nanostructured silicon (Si) surface is prepared by the pulsed laser ablation (PLA) of a Si wafer in distilled water. Silver nanoparticles (AgNPs) synthesized via PLA in distilled water are deposited on the ablated Si surface to form a SERS substrate (AgNP/aSi). Malachite green (MG) is used as a probe analyte to examine the SERS activity of the AgNP/aSi substrate. The AgNP/aSi substrate can yield an SERS spectrum of MG with high resolution at a minimum concentration of 0.01 ppm. Using the AgNP/aSi substrate, we investigate its capacity for detecting tetracycline (TC) residue in shrimp. The Raman peak intensities at 1320 cm−1 for TC concentrations from 10 to 0.1 ppm show a linear relationship with the corresponding logarithmic concentrations. Our simple and efficient method can be used for the trace detection of MG, TC, and other antibiotics in various applications via SERS. [ABSTRACT FROM AUTHOR]

Fine particles (PM2.5) in the atmosphere, especially PM2.5 bounded with trace metals, pose potentially adverse human health risks. This study aimed to characterize the trace elements in PM2.5 in a suburban area of Hanoi from November 2019 to December 2020. The study area represented a mixture of industrial, agricultural, and residential areas. The results revealed that PM2.5 mass was highest in winter due to the stable meteorological conditions, which disfavor the particulate matter dispersion in the atmosphere. Fe, Mg, Zn, K, and Al were the most abundant elements in PM2.5, accounting for 29.6, 19.0, 16.3, 15.8, and 11.3% of the total concentration of metals, respectively. PM2.5-bound trace metals were highest in winter, followed by autumn and spring. Principal component analysis with multiple linear regression (PCA/MLR) illustrated that crustal dust, pesticide, and industrial emissions contributed to 73.6% of the total contribution sources, while vehicle exhaust mixed with coal combustion accounted for 64.1% of the total contribution sources. The health risk assessments suggested that As (HQ = 4.7) and Cd (HQ = 3.1) had non-carcinogenic risks for adults. The cumulative carcinogenic risk of elements was within the acceptable range for both children and adults. Notably, the source of As should be paid attention to as the As high concentration exceeding the safe level for non-carcinogenic risks in the study area. [ABSTRACT FROM AUTHOR]

In this study, an analytical method for the simultaneous determination of 7 major pharmaceutical residues in Vietnam, namely, carbamazepine, ciprofloxacin, ofloxacin, ketoprofen, paracetamol, sulfamethoxazole, and trimethoprim, in surface water and hospital wastewater has been developed. The method includes enrichment and clean-up steps by solid phase extraction using mix-mode cation exchange, followed by identification and quantification using an ultrahigh-performance liquid chromatography and tandem mass spectrometry and employing electrospray ionization (UPLC-ESI-MS/MS). Seven target compounds were separated on the reversed phase column and detected in multiple reaction monitoring (MRM) mode within 6 minutes. The present study also optimized the operating parameters of the mass spectrometer to achieve the highest analytical signals for all target compounds. All characteristic parameters of the analytical method were investigated, including linearity range, limit of detection, limit of quantification, precision, and accuracy. The important parameter in UPLC-ESI-MS/MS, matrix effect, was assessed and implemented via preextraction and postextraction spiking experiments. The overall recoveries of all target compounds were in the ranges from 55% to 109% and 56 % to 115% for surface water and hospital wastewater, respectively. Detection limits for surface water and hospital wastewater were 0.005–0.015 µg L−1 and 0.014–0.123 µg L−1, respectively. The sensitivity of the developed method was allowed for determination of target compounds at trace level in environmental water samples. The in-house validation of the developed method was performed by spiking experiment in both the surface water and hospital wastewater matrix. The method was then applied to analyze several surface water and hospital wastewater samples taken from West Lake and some hospitals in Vietnam, where the level of these pharmaceutical product residues was still missed. Sulfamethoxazole was present at a high detection frequency in both surface water (33% of analyzed samples) and hospital wastewater (81% of analyzed samples) samples. [ABSTRACT FROM AUTHOR]

Surficial sediment samples along the coastal area of the province Thai Binh in Vietnam have been collected and analysed by modified Tessier method for the mercury content. The mercury levels in these samples were found in the range between 0.12–3.79 mg/kg. Elevated concentrations were observed in some locations close to tidal marshes, large aquaculture productions or low-lying areas. The highest level of mercury was detected in a low-lying terrain near large aquaculture productions. The majority of the mercury species in all samples were witnessed in the fraction bound to organic matters. The predominance of this fraction is possibly associated with some misuses of mercurial fungicides by aqua farmers. These mercury species remain quite resistant in the sediments, thus posing a quite low risk for the surrounding ecological environment. Nevertheless, it is necessary to undertake further studies to evaluate the effect of this contamination on the food chain. [ABSTRACT FROM AUTHOR]

This study investigated the airborne concentration of PM10 and 20 trace elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Na, Pb, Ti, V, Zn) in residential, industry, traffic road, coal mining, thermal power plant area of Bac Giang province. The average PM10 concentration was highest at coal site, followed by traffic 1 sites, industrial sites and traffic 2 sites, the residential sites, and lowest at the power plant site located in mountain area. While Al, Ca, Fe, K, Mg, Na were the most abundant elements in all sampling sites, accounting for 73–96% of total obtained elements, the concentration of As, Cd, Cr, Cu, Mn, Ni, Pb, V, and Zn occupied from 2.9 to 23.2%. Noticeably, the concentrations of Cd were from 7 to 65 times higher than the concentration limit for Cd (0.1 ng/m3) according the World Health Organization (WHO). Although, the Hazard Index (HI values) of all metals were found to be within the safe level for both children and adults, the Carcinogenic Risk (CR) of Cr and As in all sites were closed to the acceptable levels for children, implying a potential carcinogenic risks of these metals. [ABSTRACT FROM AUTHOR]

A survey conducted on newly cultivated lowland rice fields by direct seeding method in Hai Duong Province, Viet Nam, in March 2017 revealed high devastation of the field. In these fields, farmers used an annual crop rotation cycle of rice-scallion-rice. Investigations on the devastated fields revealed that the chemical and physical soil properties were appropriate for rice cultivation. On the other hand, observations done on the root systems showed that the dead plants have symptomatic root galls suggesting the presence of plant parasitic nematodes. Sequencing of the internal transcribed spacer (ITS) region of the rDNA genes of the nematodes showed that the root nematodes extracted from the infested fields belonged to Meloidogyne graminicola. The reproductive factor of the isolated M. graminicola population on the IR64 rice variety (Oryza sativa indica) was normal, suggesting that the impact of this plant pest was not due to the emergence of an unusual virulent population. The combination of the three factors (wrong cropping choice for rotation, using rice variety susceptible to M. graminicola and direct seeding) were obviously promoting the nematode infection and its high proliferation in the surveyed fields. Meloidogyne graminicola could parasitize and propagate in scallions of Vietnam. Since this plant is annually cultivated on a paddy field for crop rotation, preventive measures or alternative plant for crop rottion is necessary. [ABSTRACT FROM AUTHOR]

Meloidogyne graminicola , also known as the rice root-knot nematode, is one of the most damaging plant-parasitic nematode, especially on rice. This obligate soilborne parasite induces the formation of galls that disturb the root morphology and physiology. Its impact on the root microbiome is still not well described. Here, we conducted a survey in Northern Vietnam where we collected infected (with galls) and non-infected root tips from the same plants in three naturally infested fields. Using a metabarcoding approach, we discovered that M. graminicola infection caused modifications of the root bacterial community composition and network structure. Interestingly, we observed in infected roots a higher diversity and species richness (+24% observed ESVs) as well as a denser and more complex co-occurrence network (+44% nodes and +136% links). We identified enriched taxa that include several hubs, which could serve as potential indicators or biocontrol agents of the nematode infection. Moreover, the community of infected roots is more specific suggesting changes in the functional capabilities to survive in the gall environment. We thus describe the signature of the gall microbiome (the 'gallobiome') with shifting abundances and enrichments that lead to a strong restructuration of the root microbiome. [ABSTRACT FROM AUTHOR]