Northeast Vietnam Research Articles

Distribution characteristics of tropical cyclones affecting the Vietnam region during 1992–2022

This research investigates the distribution characteristics of tropical cyclones affecting the Vietnam region, including the mainland and the East Vietnam Sea, from 1992 to 2022. The tropical cyclone activity showed an increasing trend, mainly in the numbers of tropical depressions and typhoons with the sustained maximum wind speed ranging from level 12 to 15 on the Beaufort Wind Scale; however, this trend did not meet the statistical 99% confidence level. The number of tropical cyclones directly affecting the mainland of Vietnam accounted for approximately 32%. Over the East Vietnam Sea, tropical cyclones presented a peak in September and a slump in February. Occurrence frequencies and probabilities were significantly high over the in-shore and off-shore regions from Quang Ninh to Phu Yen, over the North and Center of East Vietnam Sea, where the maximum frequencies could be 0.9 tropical cyclone/year over the Gulf of Tonkin higher than 1.1 tropical cyclone/year passing a grid of 1o longitude-latitude over the north East Vietnam Sea. Meanwhile, the southern offshore areas from Phu Yen - Ca Mau, Ca Mau - Kien Giang, and Thailand Gulf were less influenced by tropical cyclones. The frequency and probability of typhoons were below 0.1 tropical cyclone/year and 0.2%, respectively.

New subsurface structural insights of Northeast Vietnam: Advanced implications from high-resolution magnetic data

Northeast Vietnam is covered by sedimentary rocks, and its subsurface structures can be determined by geophysical studies. However, the structural patterns in Northeast Vietnam have so far been poorly studied and there is a lack of addressing the complex geological features of this area. Outlining such geological features is commonly achieved by applying various edge detection methods to magnetic fields. In this research, we applied nine enhancement techniques to magnetic data of Northeast Vietnam to identify geological features in this area. The methods are tested on synthetic data before applying to RTP (reduction to pole) magnetic data that are obtained from the multiple stage RTP technique. Four semiautomated depth estimation methods are also used to obtain the depth of magnetic structures in Northeast Vietnam. The results indicate that the normalized total gradient and power transform of the tilt angle of the total horizontal gradient can produce geological features more clearly than others. The findings show that the study area is dominated by NE-SW and ENE-WSW trending lineaments, and most of magnetic sources are around 1–2.5 km deep in the area. The NE-SW and ENE-WSW trending structures are possibly related to the left-lateral motion along the Ailaoshan–Red River shear zone. Our findings also show that Northeast Vietnam may be considered as a southwestern continuation of the South China Block. Our results provide a better picture of the structural features of Northeast Vietnam and overcome the gap in understanding the tectonic and geological framework of this important area.

Harvest and trade of wild edible russula griseocarnosa in North Vietnam

This study examines the harvest and trade of wild edible Russula griseocarnosa in north Vietnam. Russula griseocarnosa is an edible forest mushroom, but there is no reliable information on harvesting practices and trade in this species in Vietnam. This study aims to provide ethnomycological and marketing knowledge for this mushroom. Semi-structured interviews were conducted with mushroom collectors and traders over 2 years; harvest yields were obtained from local officials; and policy settings were sought from forest managers. About 85% of mushroom collectors were women of the Dao, Lo Ursula, Muong, Nung, Mong, San Chi, San Diu, and Tay ethnicities. The collecting season was bimodal, with the wet season beginning (May) and ending (September). The traders were Hoa, Kinh, Nung and Tay, and 57% were women. Fresh mushrooms sold for 9.1-10.5 US$/kg on dry days and 7.0-7.9 US$/kg on wet days. The best grade of dried product fetched 70.4-83.3 US$/kg. A number of interim policies have been established to encourage local people to protect forests and to help create a sustainable edible wild mushroom market. Our study provides the first detailed account of the role of edible wild mushrooms in northeast Vietnam, and this will inform the co-development of rural livelihood and sustainable forest management plans.

Geological setting, lead-zinc mineralization characteristics and its potential prospects in the Na Bop - Pu Sap area, Cho Don, Northeastern Vietnam

The Lo Gam structural zone is recognized as a crucial area for the occurrence of lead-zinc deposits in Northeast Vietnam, encompassing the distinguished territories of Cho Dien and Cho Don. Specifically, within the Cho Don area, the Na Bop-Pu Sap area emerges as particularly noteworthy owing to the considerable scale and quality of its lead-zinc ore deposits. In order to comprehensively investigate the geological attributes and lead-zinc mineralization phenomena prevalent in Na Bop-Pu Sap, a suite of analytical techniques including petrographic analyses, mineralogical examinations, scanning electron microscopy (SEM), and ICP-MS were employed. Furthermore, stable isotope investigations and single mineral sphalerite analyses were conducted to assess the origin of metal constituents and the physicochemical conditions conducive to ore genesis. The Na Bop-Pu Sap area is under the influence of the NW-SE fault system, with the ore structure predominantly manifesting as bands and veins aligned parallel to the foliations of hosted rock. This configuration suggests a close association between the formation of lead-zinc ore and the foliation processes occurring within the shear zones. The assemblage of ore minerals within the region primarily comprises galena, sphalerite, pyrite, pyrrhotite, and arsenopyrite. Integration of S and Pb isotopic analyses alongside single mineral sphalerite assessments reveals that the ore-forming solutions emanate from both magmatic activity and sedimentary sources, with lead-zinc ore deposition occurring at temperatures ranging from low to medium. Projections suggest that the Na Bop-Pu Sap mining area may exhibit relative degrees of erosion extending to depths of approximately 600 meters below the existing terrain surface. This comprehensive examination of the ore characteristics in the Na Bop-Pu Sap mine area yields invaluable insights, thereby advancing our understanding of the potential for deep-seated lead-zinc mineral resources within the Northeastern Vietnam.

Characteristics of heavy metals in surface sediments of the Van Don-Tra Co coast, northeast Vietnam

Eighteen surface sediment samples were collected from the Van Don-Tra Co coast, northwestern Gulf of Tonkin, for analyzing the concentration of heavy metals (Zn, Cr, As, Cu, Ni, Pb, Co, and Cd) and grain size. The statistical and contamination indices of heavy metals were calculated to evaluate the extent of pollution caused due to heavy metals and their potential harm to the environment. According to the analysis results, the contamination of heavy metals in the study area were higher than the background concentrations, except for Pb. The heavy metal concentrations in the study area followed the descending order of Zn > Cr > As > Cu > Ni > Pb > Co > Cd. The concentrations of heavy metals do not correlate with clay content, and almost heavy metals were non-correlated with silt and sand contents, except for Cr, implying that the grain size does not control heavy metals concentration in surface sediments in the region. The results of pollution indices imply that the contamination in the environment was due to excess accumulation of Cd, in contrast to that of Zn. The ecological pollution risk shows an increased risk of heavy metal pollution. According to the statistical index, the contamination of heavy metals in surface sediments in the study area could come from the same sources under the same environmental conditions and is related to the source of sedimentary material from the mainland near the study area.

Antimicrobial residues in meat from chickens in Northeast Vietnam: analytical validation and pilot study for sampling optimisation

Antimicrobials used in chicken farming for therapeutic and/or prophylactic purposes may result in unacceptable levels of edible residues, if withdrawal periods are not respected. To evaluate the risk in Vietnam, we validated an analytical method to detect antimicrobial residues from chicken meat samples and carried out a pilot cross-sectional study to identify optimal sampling strategies. A total of 45 raw meat samples were collected from 4 markets, 1 slaughterhouse and 4 farms (5 per site) in Northern Vietnam, between March and April 2021. Farmers were asked about antimicrobials used during sampled production cycles (5 chickens sampled per batch). Samples were analysed using liquid chromatography-tandem mass spectrometry for the presence of 68 antimicrobials at a pre-defined validation concentration. 7 compounds were identified from 4 classes (tetracyclines, sulphonamides, macrolides, and fluoroquinolones). In markets, where the source of sampled chickens was unknown, a diverse pool of residual antimicrobials was detected in 20% (4/20) of the meat samples. No residues were detected in samples from the slaughterhouse. No residues were detected in chickens from the one farm that reported using antimicrobials, whereas sulfadimethoxine, doxycycline and tilmicosin residues were identified from the other 3 farms reporting no antimicrobial use. The probability of detecting antimicrobial residues present in a flock based on sampling a single chicken was estimated at 0.93 (highest density interval 0.735–0.997). The preliminary results suggest a disparity between farmers’ reports on antimicrobial drug use and actual usage, and that the analysis of a single sample per farm has a high probability of detecting antimicrobial residues, if present.

Households’ willingness-to-pay for mangrove environmental services: Evidence from Phu Long, Northeast Vietnam

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.

Identifying the wetlands of international importance in Beibu Gulf along the East Asian – Australasian Flyway, based on multiple citizen science datasets

The Beibu Gulf (Gulf of Tonkin, Vinh Bac Bo in Vietnamese), located midway along the East Asian-Australasian Flyway (EAAF), is a critical stopover and wintering region for migratory waterbirds. This transboundary coastal region, spanning between China and Vietnam, harbors diverse wetland habitats that provide refuge to waterbird species, including highly threatened species such as the spoon-billed sandpiper (CR) and the black-faced spoonbill (EN). However, the scarcity of comprehensive assessments regarding waterbird abundances, distribution, key wetland habitats, and regional threats hinders our understanding of its conservation significance at the flyway level. Further research is needed to address these knowledge gaps and facilitate effective conservation efforts in the Beibu Gulf. By synthesizing accessible citizen science datasets and published records from wetland sites in south China and northeast Vietnam, we concluded that at least 97 waterbird species used the Gulf’s wetlands during their annual cycle. Among surveys conducted from 2014 to 2022, 5 and 11 waterbird species were considered as first and second class protected species under the National Key Protected Wild Animal List in China; 2 species were listed as Critically Endangered on the IUCN Red List, 4 as Endangered and 2 as Vulnerable, underlying the critical importance of the Beibu Gulf for the survival of these species. Our study identified 25 sites in the Beibu Gulf that met the criteria for designation as internationally important wetlands. Alarmingly, less than a quarter (n = 5, or 20%) of these sites benefit from national or international protection. Localized threats, including aquatic resource harvesting, hunting, and aquaculture/fisheries, were widespread in the region. This study provides a crucial scientific baseline for continued waterbird monitoring, site prioritization, and the development of effective habitat management plans to conserve vital coastal wetland habitats in the Beibu Gulf in China and Vietnam.

Association of ADH1B rs1229984, ADH1C rs698, and ALDH2 rs671 with Alcohol abuse and Alcoholic Cirrhosis in People Living in Northeast Vietnam.

Alcohol abuse can cause developing cirrhosis, even liver cancer. Several single nucleotide polymorphisms (SNPs) of ADH1B, ADH1C, and ALDH2 genes have been reported to be associated with alcohol abuse and alcoholic cirrhosis (ALC). This study investigated the association between three SNPs of ADH1B rs1229984, ADH1C rs698, and ALDH2 rs671 with alcohol abuse and ALC in people living in the Northeast region of Vietnam. 306 male participants were recruited including 206 alcoholics (106 ALC, 100 without ALC) and 100 healthy non-alcoholics. Clinical characteristics were collected by clinicians. Genotypes were identified by Sanger sequencing. Chi-Square (χ2) and Fisher-exact tests were used to assess the differences in age and clinical characteristics, Child-Pugh score, frequencies of alleles and genotypes. Our data showed that the frequency of ALDH2*1 was significantly higher in alcoholics (88.59%) and ALC groups (93.40%) than that of healthy non-alcoholics (78.50%) with p=0.0009 and non-ALC group (83.50%) with p=0.002, respectively. We detected opposite results when examined ALDH2*2. Frequency of combined genotypes with high acetaldehyde accumulation were significantly lower in alcoholics and ALC group than those of control groups with p=0.005 and p=0.008, respectively. Meanwhile, the proportion of combined genotypes with non-acetaldehyde accumulation were significantly two times higher in the ALC group (19.98%) than those of the non-ALC group (8%) with p=0.035. These combined genotypes showed a decreasing trend in the Child-Pugh score from likely phenotype causing risk for non-acetaldehyde accumulation to high acetaldehyde accumulation. The ALDH2*1 allele was found as a risk factor for alcohol abuse and ALC, and combined genotypes of ADH1B rs1229984, ADH1C rs698, and ALDH2 rs671 with non-acetaldehyde accumulation increase ALC risk. In contrast, ALDH2*2 and the genotype combinations related to high acetaldehyde accumulation were protective factors against alcohol abuse and ALC.

Population structure of Vietnamese pigs using mitochondrial DNA.

The D-loop region on mitochondrial DNA (mtDNA) is frequently used for analyses of maternal lineages within domestic animal species. There are many native pig breeds in Vietnam, but their origins remain unclear. This study investigated maternal lineages using the D-loop region on mtDNA of 260 samples collected from native pigs in 20 provinces across Vietnam. The D-loop region of all samples was amplified and sequenced. We obtained 713 bp sequences of the D-loop region for each sample excluding the repeat region, and variants on this region were used to construct a phylogenetic tree. We detected 50 haplotypes from Vietnamese native pigs, with 27 novel haplotypes. Phylogenetic tree analysis showed two haplotype groups: one for the MTSEA group, frequently found in domestic pigs in the mountainous areas of Cambodia and Laos; and the D2 group, found in pigs originating from Chinese pigs. No European haplotype was found. Haplotypes in northeast Vietnam comprised only haplotypes of the D2 group, whereas in areas from the northwest mountains to the south, we found haplotypes belonging to both the D2 and MTSEA groups. This study suggested that both origins contributed to maternal lineages of current populations of Vietnamese native pigs.

Forecasting zonation of oil-gas prospects in the sedimentary basins of the Northeast Vietnam continental shelf based on gravity and borhole data

This study used the 2D and 3D normalized total gradient (NTG) method of gravity anomalies to detect the gravity anomalies caused by oil-gas reservoirs. The NTG of gravity anomalies can be associated with known oil-gas reservoirs, and most of them seem to be a good coincidence with the reservoirs. The closed minima of the NTG of gravity anomalies indicate the existence and locations of the density deficient anomalies closely related to the possible oil-gas reservoirs. The reliability of the NTG method depends mainly on the Fourier-developed coefficient N. Here, N is optimally selected by the borehole data. The 2D, 3D normalized total gradient method is applied in the sedimentary basins of the Northeast Vietnam continental shelf. Borehole data confirm the results of the method.

Livelihood vulnerability to climate change: a case of farm households in Northeast Vietnam

Livelihood vulnerability to climate change: a case of farm households in Northeast Vietnam

Development of Logistics Hubs Served by Strategic Freight Corridor: The Case of Northeast Vietnam

Development of Logistics Hubs Served by Strategic Freight Corridor: The Case of Northeast Vietnam

Assessing Impacts of Mining Activities on Land Use/Land Cover Change Using Remote Sensing and GIS Techniques: A Case Study in Campha City, Vietnam

Coal is one of the most mining commodities to date, especially to supply both national andinternational energy needs. Coal mining activities that are not well managed will have an impact on theoccurrence of environmental damage. The present study was undertaken to analyze the process of humaninducedlandscape transformation in the coal mines affected areas of Cam Pha, northeast Vietnam byinterpreting temporal remote sensing data and using Geographic Information System. This experimentrevealed that most of the study area was dominated by forest in all the time sequence period. The forestcover has decreased about 21.3%, meanwhile having nine fold increase in mining area from 1990 to 2020.The forest area lost during the study period was 7983.45 ha due to land cover conversion into mining area.The mining activities were also detrimental to the bare land and water body cover. The results of this studyare expected to be used to support government efforts and mining managers in post-mining coal activities.

Effects of Climate-Smart Agriculture Adoption on Performance of Rice Farmers in Northeast Vietnam

Agricultural production is increasingly vulnerable to risks and uncertainties associated with climate changes. Climate-smart agriculture (CSA) has been proposed to address challenges in agricultural production such as food security, water shortage, drought, and soil erosion, etc. The benefits of CSA adoption for farmers have been debated. Many previous studies have indicated that impacts seem to be affected by selection bias. However, controlling such selection bias has not been considered in studies on the CSA adoption. Thus, in this study, we analyzed the impacts of CSA adoption on major economic indicators for rice farmers. The Propensity Score Matching (PSM) method was employed to address such selection bias for a case study on rice farmers in Thai Nguyen province, Vietnam. Comparing main economic indicators, we found significant differences in rice yields and used seed inputs between CSA and non-CSA adopters. Ignoring selection bias control resulted in overestimation of economic returns. The results also indicate limited contribution of CSA adoption to a reduction in pesticide and herbicide usage, and an increase in use of organic fertilizers. Some implications for further research are also discussed.

Description of one new species of freshwater shrimp of the genus Caridina (Crustacea: Decapoda: Atyidae) from two karst caves of Northern Vietnam.

A new species of atyid freshwater shrimp is described from two caves of Bac Kan Province, Northeast Vietnam, namely Caridina namdat sp. nov. This species can be distinguished from its congeners by a suite of morphological characters such as reduced eyes with short eyestalk, very short and unarmed rostrum, slender second pereiopod, elongated endopod of male first pleopod, and long appendix interna of the male second pleopod. Molecular phylogenetic data from the mitochondrial cytochrome oxidase subunit I (COI) and 16S ribosomal RNA genes also support the distinctiveness of the new species from all other examined species.

In-vitro Antioxidant, Antidiabetic, Antibacterial and Cytotoxic Activities of Essential Oil extracted from Flowers of Illicium verum L.

Illicium verum is a small native evergreen tree of northeast Vietnam, India and southwest China. It is the flower of a medium-sized tree and is also known as star anise belongs to the family of Schisandraceae that grows in North America, Atlantic region, and tropical and subtropical zones of Asia. This study investigated the in vitro cytotoxic effects of essential oil obtained from the flowers of Illicium verum is also known as star anise. Steam distillation method was used to extract oil from the flowers of Illicium verum. Antioxidant activities such as DPPH (2,2-diphenyl-1-picrylhydrazyl), and ferric reducing power assays were assessed followed by total phenolic contents was estimated by folin-ciocalteau reagent method. Gas chromatography–mass spectrometry (GC-MS) analysis was used to find out volatile and semi-volatile compounds of essential oil extracted from Illicium verum. Anti-proliferative effect was studied by MTT assay method using MCF 7 and HepG 2 cancer cell lines. The maximum HepG 2 cell death was 25.73 ±0.24 % at 100µg/mL concentration and the IC50 was 194.32±0.24% at 100µg/mL concentration. The maximum MCF 7 cell death was 32.64±0.32% at 100µg/mL concentration and the IC50 was 153.18 ± 0.32% at 100µg/mL concentration.

Evaluation of Different Machine Learning Models for Predicting Soil Erosion in Tropical Sloping Lands of Northeast Vietnam

Soil erosion induced by rainfall under prevailing conditions is a prominent problem to farmers in tropical sloping lands of Northeast Vietnam. This study evaluates possibility of predicting erosion status by machine learning models, including fuzzy k-nearest neighbor (FKNN), artificial neural network (ANN), support vector machine (SVM), least squares support vector machine (LSSVM), and relevance vector machine (RVM). Model evaluation employed a historical dataset consisting of ten explanatory variables and soil erosion featured four different land use managements on hillslopes in Northwest Vietnam. All 236 data samples representing soil erosion/nonerosion events were randomly prepared (80% for training and 20% for testing) to assess the robustness of the five models. This subsampling process was repeatedly carried out by 30 rounds to eliminate the issue of randomness in data selection. Classification accuracy rate (CAR) and area under receiver operating characteristic (AUC) were used to evaluate performance of the five models. Significant difference between different algorithms was verified by the Wilcoxon test. Results of the study showed that RVM model achieves the best outcomes in both training (CAR = 92.22% and AUC = 0.98) and testing phases (CAR = 91.94% and AUC = 0.97). Four other learning algorithms also demonstrated good performance as indicated by their CAR values surpassing 80% and AUC values greater than 0.9. Hence, these results strongly confirm the efficacy of applying machine learning models for soil erosion prediction.

Late Ordovician (Katian) Graptolites and Shelly Fauna from the Phu Ngu Formation, North-East Vietnam

Two new graptolite assemblages are identified from discrete intervals within the Phu Ngu Formation, Na Ri District, Bac Kan Province, north-east Vietnam. The graptolites occur in laminated mud/siltstones thought to be distal turbidite deposits. A low-diversity diplograptid sensu lato assemblage occurs in mud-rich layers that are interlaminated with silty and sandy horizons containing the dendroid graptolite Dictyonema sp. This level also contains orthoconic nautiloids and conulariids. A few metres stratigraphically above, a second more diverse graptolite assemblage comprises a single Dicellograptus, tentatively identified as D. flexuosus, together with Climacograptus dorotheus and Orthograptus truncatus pauperatus in mud and silt laminae that also yield brachiopods, orthoconic nautiloids, conulariids, fragmentary trilobites, and ostracods. The ostracods include the first East Asian occurrence of the typically Baltic genus Kinnekullea, and we describe the new species Kinnekullea gaia. The graptolites suggest a Late Ordovician Katian age, most probably in the Dicranograptus clingani Biozone, this being older than previous biostratigraphical constraints on the Phu Ngu Formation.

Optimizing lime pretreatment of rice straw for biolipid production using oleaginous microorganisms

This work focuses on the lime pretreatment of rice straw, agricultural waste in northeast Vietnam, for microbial lipid (bio-lipid) production. A response surface methodology approach was performed to optimize parameters for the pretreatment process. These parameters are the concentration of Ca(OH)2, hydrolysis temperature, and maintained time; the effect is considered bio-lipid production yield. The lipid yield was estimated through consolidated bioprocessing of the pretreated rice straw as a substrate and using the fungus strain (Aspergillus oryzae 32) and the yeast strain (Lipomyces starkeyi 22). As a result, the optimal pretreatment conditions for maximum lipid yield were obtained at Ca(OH)2 concentration of 12 g/L and hydrolysis temperature of 110 °C within 60 min. The accumulated lipid in fermentation using these oleaginous microorganisms was 8.5g/100g oven-dry weight of rice straw (10.9g/100g for pretreated rice straw). The biolipid consisted of 42.6% saturated, 21.1% monounsaturated (MUFA), and 35.1% polyunsaturated (PUFA) fatty acids.