Dong Nai River Research Articles

Concentrations of Organochlorine, Organophosphorus, and Pyrethroid Pesticides in Rivers Worldwide (2014–2024): A Review

The extensive use of pesticides has led to the contamination of natural resources, sometimes causing significant and irreversible damage to the environment and human health. Even though the use of many pesticides is banned, these compounds are still being found in rivers worldwide. In this review, 205 documents have been selected to provide an overview of pesticide contamination in rivers over the last 10 years (2014–2024). After these documents were examined, information of 47 river systems was organized according to the types of pesticides most frequently detected, including organochloride, organophosphorus, and pyrethroid compounds. A total of 156 compounds were classified, showing that 46% of these rivers contain organochlorine compounds, while 40% exhibit organophosphorus pesticides. Aldrin, hexachlorocyclohexane, and endosulfan were the predominant organochlorine pesticides with concentration values between 0.4 and 37 × 105 ng L−1. Chlorpyrifos, malathion, and diazinon were the main organophosphorus pesticides with concentrations between 1 and 11 × 105 ng L−1. Comparing the pesticide concentrations with standard guidelines, we found that the Ganga River in India (90 ng L−1), the Owan and Okura Rivers in Nigeria (210 and 9 × 103 ng L−1), and the Dong Nai River in Vietnam (68 ng L−1) exceed the permissible levels of aldrin (30 ng L−1).

Developing a circular economy from plastic waste and identifying microplastics in domestic water supplies in Ho Chi Minh City and the Southeastern provinces

Abstract While humans are struggling to deal with plastic waste, the plastic decomposition products, namely microplastics, have silently infiltrated almost all environmental states. This study examines the feasibility of a circular economy approach for addressing plastic waste and reducing microplastics in source water in Southeastern provinces. Of the 400 households surveyed, there were 200 households in Ho Chi Minh, 50 households in Dong-naiand 150 households in Binh Duong, only 10% of household plastic waste is recycled, 33% of them are sold as scrap and 57% of them are completely processed. Out of the remaining 57% of waste, it can be the starting material to produce later stage products and create income opportunities of hundreds of billions of VND per month for Ho Chi Minh and Binh Duong province. The process of breaking down plastic waste into microplastics in the Sai Gon River and Dong Nai River has resulted in the emergence of microplastic polymers such as Polypropylene (27.1%), Polyethylene (51.2%), Polyvinyl Chloride (13.4%), and 8.3% of other plastics. These microplastics pose a significant threat to human health. The SWOT analysis identifies opportunities and challenges for implementing a circular economy approach to minimize plastic waste and microplastics in the study area.

Response of streamflow and sediment variability to cascade dam development and climate change in the Sai Gon Dong Nai River basin

Response of streamflow and sediment variability to cascade dam development and climate change in the Sai Gon Dong Nai River basin

Acute Toxicity of DDT on Embryo and Larval Growth of the Pacific Oyster, Crassostrea gigas (Thunberg, 1793): A Case Study in the Saigon–Dongnai River, Vietnam

Acute Toxicity of DDT on Embryo and Larval Growth of the Pacific Oyster, Crassostrea gigas (Thunberg, 1793): A Case Study in the Saigon–Dongnai River, Vietnam

The seasonal variations in the interactions between rare earth elements and organic matter in tropical rivers

The escalation of global demands for critical minerals to facilitate the green energy transition creates emerging needs to better understand their environmental behaviours. Several nations recognize rare earth elements (REEs) as priority critical minerals and emphasize the necessity to evaluate their environmental mobility and potential effects on natural ecosystems and human health. Here, we investigated the seasonal variations in dissolved concentrations of REEs and their leachable fractions from suspended particles in samples collected bi-weekly from the Sai Gon and Dong Nai Rivers in Southern Vietnam. The investigation period extended over sixteen months, including a transition from wet to dry seasons. We reported significant mobility of REEs in the river waters during the wet season due to watershed runoff, especially in Sai Gon River with the occurrence of acid-sulphate soils. Dissolved REE concentrations in the dry season were significantly lower because of the interactions with organic-rich particles (up to 13% of particulate organic carbon, POC) mainly derived from phytoplankton materials. The conditional distribution coefficients (logKD from 5 to 7 for Pr) were proportional to POC content. The scavenging capacity of particulate organic matter also led to affect the fractionation between light REEs and heavy REEs in solution, and the characteristic Middle REE-enrichment patterns for the leachable REEs fraction. We also reported significant Eu anomalies (Eu/Eu* up to 7) in the Dong Nai River during the dry season and associated this observation with the decomposition of organic matter that previously accumulated Eu. However, further studies are required to confirm this hypothesis because of small reservoir effects; elevated Eu anomalies were observed in water samples with low dissolved Eu concentrations.

Water quality assessment using water quality index: a case of the Dong Nai river- sections flow through Bien Hoa city

Over the past few years, there are many activities had negative impacts on the surface water of the Dong Nai river such as industry, agriculture, and service development activities; Therefore, river water quality is significantly relieved. This study was conducted to evaluate the effect of elements on the water quality in Bien Hoa City, Dong Nai Province. Analyze the parameters of pH, temperature, DO, BOD5, COD, N-NH4+, P-PO43-, TSS, turbidity, and total Coliform on 54 samples from Jan to Dec in 2022. The water quality index (WQI) and statistical analysis were applied to explore and determine the water quality in Bien Hoa City. The results of the study indicated that the water quality of Dong Nai river is not quite good, most parameters reach the limit value B1 according to QCVN 08:2015/BTNMT; however, the values of parameters DO, total coliforms, TSS exceed the limit value B1 significantly. WQI values fluctuate at a fairly high level from 17 to 68, and the average WQI of the river reaches is quite low, so the authority should have promulgated the law to protect the water surface of this river; Therefore, water quality assessment is significant for better control and management of the surface water environment in Vietnam.

Assessing water quality in the Dong Nai River (Vietnam): implications for sustainable management and pollution control.

Dong Nai River provides essential water resources for millions of people across 11 provinces and cities in Vietnam. However, the different pollution sources such as household, farming, and industrial operations have caused the river water quality to deteriorate over the past decade. To gain a comprehensive understanding of the river's surface water quality, this study employed the water quality index (WQI) across 12 different sampling sites. In total,144 water samples with 11 parameters were analyzed in accordance with the Vietnamese standard 08:2015/MONRE. Results revealed a range of surface water quality, from poor to good according to the VN-WQI (Vietnamese standard), and a medium even bad level in some months according to the NS-WQI (American standard). The study also identified temperature, coliform, and dissolved oxygen (DO) as strong contributors to WQI values (VN_WQI standard). Principal component analysis/factor analysis was used to determine pollution sources, with the results highlighting agricultural and domestic activities as the main contributors to river pollution. In conclusion, this study underscores the importance of effective planning and management of infrastructure zoning and local activities to improve the river's surface water quality and surrounding areas, as well as safeguard the well-being of the millions who depend on it.

Identifying the impact of land use land cover change on streamflow and nitrate load following modeling approach: a case study in the upstream Dong Nai River basin, Vietnam.

Tri An Reservoir is a vital source of water for agriculture, industry, hydropower, and public usage in Southern Vietnam. Due to human activities, water eutrophication has become a serious problem in recent decades. This study investigated for the first time the impact of land use and land cover (LULC) change on streamflow and nitrate load from the upstream Dong Nai River basin, which is the largest watershed of the reservoir. The study utilized several LULC scenarios, including LULC 2000, 2010, and 2020. The SWAT model was applied to model the watershed during the period 1997-2009. Results showed that the hydrological model performed satisfactorily based on the Nash-Sutcliffe efficiency (NSE) coefficient, the root mean square error observations standard deviation ratio (RSR), and the percent bias (PBIAS). The average simulated values of monthly streamflow and nitrate load were 453.7, 450.0, 446.7 m3/s and 17,699.43, 17,869.13, 17,590.81 tonnes for the LULC 2000, 2010, and 2020 scenarios, respectively. There were no significant differences in streamflow and nitrate load at the basin level under the different LULC scenarios. However, when looking at the subbasin level, there were differences in nitrate load among the scenarios. This suggests that the impacts of LULC on nitrate load may be more pronounced at smaller scales. Overall, our finding underscores the importance of modeling techniques in predicting the impacts of LULC change on streamflow and water quality, which can ultimately aid in the sustainable management of water resources.

Amino accelerators and antioxidants in sediments from the Dong Nai River System, Vietnam: Distribution and influential factors

Amino accelerators and antioxidants (AAL/Os) have become a suite of contaminants of emerging concern recently due to the accumulating evidence for their environmental occurrence and associated toxic potential. Nevertheless, data on sedimentary deposition of AAL/Os has remained scarce, particularly for regions beyond the North America. In the present study, we elucidated spatial distribution of fifteen AAL/Os and five AAO transformation products (AAOTPs) in seventy-seven sediments from the Dong Nai River System (DNRS), Vietnam. Total concentrations of AAL/Os (∑AAL/Os) ranged from 0.377 to 51.4 ng/g (median: 5.01 ng/g). 1,3-Diphenylguanidine and 4,4′-bis(1,1-dimethylbenzyl) diphenylamine were the two most prevalent congeners, both with detection frequencies >80%. Additionally, AAOTPs were quantifiable in 79% of the DNRS sediments with a median ∑AAOTPs at 2.19 ng/g, dominated by N, N′-diphenylbenzidine and 2-nitrodiphenylamine. Higher sediment-associated levels of AAL/Os and AAOTPs were spotted in downstream and the primary tributary of the DNRS compared to the upstream, implying their cumulative sedimentation towards the estuarine region. The distribution patterns of AAL/Os and AAOTPs across individual transects also demonstrated the influence of human activities (e.g., urbanization and agriculture), hydrodynamics, and decontamination by mangrove reserves. Meanwhile, characteristics of sediments, i.e., total organic carbon (TOC) content and grain sizes, exhibited significant correlations with the burdens of these compounds, indicating their preferential partitioning into the fine and TOC-rich matter. This research sheds light on environmental behavior of AAL/Os and AAOTPs beneath Asian aquatic system, and highlights the need for further evaluation of their impacts on the wildlife and public health.

Typical pathogens on plastic debris in downstream of Sai Gon and Dong Nai rivers: an initial observation

Plastic pollution is recently receiving significant attention. In aquatic ecosystem, plastic debris can provide a habitat for microbial communities, including pathogens which might cause ad-verse impacts on aquatic animals and human health. This study, for the first time, investigated densities of typical pathogens of Coliforms and Vibrio spp. associated on plastic samples col-lected in surface water (SW), water column (WC, 5 m below surface water), and sediment (SED) at downstreams of Sai Gon river (Phu My bridge site) and Dong Nai river (Binh Khanh habour site) in the dry season of 2022. The results showed that densities of pathogens associat-ed on SW plastics were significantly higher than densities of pathogens associated on WC and SED plastics. For instance, (i) densities of Coliform on SW plastics (9.7 ± 0.1 × 106 and 180.0 ± 10.0 × 106 CFU/g plastic) were significantly higher than the ones on WC plastics (3.1 ± 0.5 × 106 and 5.5 ± 1.2 × 106 CFU/g plastic), and the ones on SED plastics (1.7 ± 0.3 × 106 and 5.7 ± 0.7 × 106 CFU/g plastic); and similarly (ii) densities of Vibrio spp. on SW plastics (4.2 ± 0.1 × 104 and 1.3 ± 0.2 × 105 CFU/g plastic) were significantly higher than the ones on WC plastics of 0.0 ± 0.0 and 7.7 ± 0.4 × 103 CFU/g plastic, and the ones on SED plastics of 2.0 ± 0.2 × 104 and 4.4 ± 0.0 × 104 CFU/g plastic, in Phu My and Binh Khanh, respectively. Other hand, densi-ties of pathogens on plastic samples colleceted in Phu My were significally lower than in the ones collected in Binh Khanh. These findings proposed that pathogen contamination on the plastic debris in downstream area is likely heavier than in upstream area of Sai Gon and Dong Nai rivers.

Differences between surfactant-free Au@Ag and CTAB-stabilized Au@Ag star-like nanoparticles in the preparation of nanoarrays to improve their surface-enhanced Raman scattering (SERS) performance.

In this study, we assessed the controlled synthesis and efficacy of surface-enhanced Raman scattering (SERS) on two distinct types of star-like Au@Ag core-shell nanoarrays. These nanoarrays were designed based on gold nanostars (AuNSs), which were synthesized with and without CTAB surfactant (AuNSs-CTAB and AuNSs-FS, respectively). The AuNS-FS nanoparticles were synthesized via a novel modification process, which helped overcome the previous limitations in the free-surfactant preparation of AuNSs by significantly increasing the number of branches, increasing the sharpness of the branches and minimizing the adsorption of the surfactant on the surface of AuNSs. Furthermore, the differences in the size and morphology of these AuNSs in the created nanoarrays were studied. To create the nanoarrays, a three-step method was employed, which involved the controlled synthesis of gold nanostars, covering them with a silver layer (AuNSs-FS@Ag and AuNSs-CTAB@Ag), and finally self-assembling the AuNS@Ag core-shelled nanoparticles via the liquid/liquid self-assembly method. AuNSs-FS@Ag showed higher ability in forming self-assembled nanoarrays than the nanoparticles prepared using CTAB, which can be attributed to the decrease in the repulsion between the nanoparticles at the interface. The nano-substrates developed with AuNSs-FS@Ag possessed numerous "hot spots" on their surface, resulting in a highly effective SERS performance. AuNSs-FS featured a significantly higher number of sharp branches than AuNSs-CTAB, making it the better choice for creating nanoarrays. It is worth mentioning that AuNSs-CTAB did not exhibit the same benefits as AuNSs-FS. The morphology of AuNSs with numerous branches was formed by controlling the seed boiling temperature and adding a specific amount of silver ions. To compare the SERS activity between the as-prepared nano-substrates, i.e., AuNS-CTAB@Ag and AuNS-FS@Ag self-assembled nanoarrays, low concentrations of crystal violet aqueous solution were characterized. The results showed that the developed AuNSs-FS@Ag could detect CV at trace concentrations ranging from 1.0 ng mL-1 to 10 ng mL-1 with a limit of detection (LOD) of 0.45 ng mL-1 and limit of quantification (LOQ) of 1.38 ng mL-1. The nano-substrates remained stable for 42 days with a decrease in the intensity of the characteristic Raman peaks of CV by less than 7.0% after storage. Furthermore, the spiking method could detect trace amounts of CV in natural water from the Dong Nai River with concentrations as low as 1 to 100 ng mL-1, with an LOD of 6.07 ng mL-1 and LOQ of 18.4 ng mL-1. This method also displayed good reproducibility with an RSD value of 5.71%. To better understand the impact of CTAB stabilization of the Au@Ag star-like nanoparticles on their surface-enhanced Raman scattering (SERS) performance, we conducted density functional theory (DFT) calculations. Our research showed that the preparation of AuNSs-FS@Ag via self-assembly is an efficient, simple, and fast process, which can be easily performed in any laboratory. Furthermore, the research and development results presented herein on nanoarrays have potential application in analyzing and determining trace amounts of organic compounds in textile dyeing wastewater.

Determination of the Pore Water Velocity Using a Salt Tracer Combined with Self-Potential Measurements

The tracer technique is recommended as an effective tool in surveying abnormal seepage through lakes and dams. By injecting a tracer into a known upstream location and monitoring the appearance of the tracer in the downstream leak point, it is possible to determine the direction and the average water velocity of the preferential flow through the dam. The detailed result achieved depends on the number of samples and the sampling locations to analyze tracer concentration over time in the field. This study proposes to use noninvasive self-potential measurements to determine the location and time the salt tracer moves through the seepage zone. The connection between the potential signal according to the propagation of the NaCl salt tracer and the water velocity was demonstrated through an experiment on a sandbox model. Experimental results express a good agreement between the time to reach the maximum value of the potential variation and the salt concentration variation with the time that water comes to monitoring locations. The result indicates an ability to determine the pore water velocity of the seepage zone based on the recording of potential signals produced by a salt tracer movement. The salt tracer test using NaCl combined with self-potential measurements was then applied to survey a leaking earth dam in the Dong Nai river basin (Vietnam).

Microplastics and solutions to remove microplastics in wastewater from wastewater treatment plants in the Saigon–Dong Nai river basin, Vietnam

Microplastics and solutions to remove microplastics in wastewater from wastewater treatment plants in the Saigon–Dong Nai river basin, Vietnam

<i>PHYSELLA ACUTA </i>(DRAPARNAUD, 1805) (MOLLUSCA: GASTROPODA: PHYSIDAE) IN THE ĐANHIM RIVER BASIN (LÂM ĐỒNG PROVINCE, VIETNAM): GENETIC AND MORPHOLOGICAL IDENTIFICATION

Invasive freshwater molluscs of the genus Physella (Gastropoda: Physidae) were discovered in the basin of the Dong Nai River, Vietnam for the first time. Based on the analysis of morphological features and the nucleotide sequence of the fragment of the COI mitochondrial gene, these molluscs were identified as belonging to the species Physella acuta (Draparnaud, 1805). The paper summarizes the available information on the distribution of this species in the waterbodies of Vietnam, provides the morphological characteristics of the studied individuals, and compares them with other populations of the species found in tropic and subtropic regions. It is shown that, despite the more than twenty-year history of registration of Physella acuta in Vietnam, the species remains relatively rare in the country's waterbodies. The presence in the studied sample of individuals of different size groups suggests that, in the basin of the Dong Nai River, self-reproducing population of Physella acuta has been established.

Impact of Forest Conversion to Agriculture on Hydrologic Regime in the Large Basin in Vietnam

Deforestation due to agricultural land expansion occurred greatly during 1994 to 2005 with a high proportion of forests being converted into agriculture in the upstream Dong Nai river basin in Vietnam. Most of these conversions included expansions of coffee plantations in Dak Lak and Lam Dong provinces, which are in the world’s Robusta coffee production area. The aim of this study is to quantify the impact on the water cycle due to the conversion of forest to coffee plantations in a tropical humid climate region by the application of a hydrological model: soil and water assessment tool (SWAT). The model was calibrated with climate data from 1980–1994, validated with climate data from 1995–2010, and verified with statistical indicators such as Nash–Sutcliffe efficiency (NSE), percent bias (PBIAS), and ratio of the root mean square error (RSR). The simulations indicated that forest conversions into agriculture (expansion of coffee plantations) had significantly increased surface runoff (SUR) while actual evapotranspiration (ET), soil water content (SW), and groundwater discharge (GW) decreased. These changes are mainly related to the decrease in infiltration and leaf area index (LAI) post land cover changes. However, the soil was not thoroughly destroyed after deforestation due to the replacement of the lost forest with crops and vegetation. Therefore, changes in infiltration were marginal and not sufficient to bring large changes in the annual flow. Higher reductions in ET and SW were proposed, resulting in reduced streamflow in the dry season at the basin where the proportion of agricultural land was higher than the forest cover. Besides the plantation expansion, which resulted in streamflow reductions in the dry season, an existing problem was over-irrigation of coffee plantations that could likely deplete groundwater resources. Hence, balancing economic benefits by coffee production and mitigating groundwater depletion issues should be prioritized for land use management in the study area.

Drastic variations in estuarine morphodynamics in Southern Vietnam: Investigating riverbed sand mining impact through hydrodynamic modelling and field controls

Recent riverbed sand mining activities have modified estuarine morphology and sedimentation patterns in many Southeast Asian deltas. The Soai Rap Estuary along the Dong Nai River (one of the largest rivers in Southern Vietnam) is one of the most intensively mined areas in the region, where large-scale sand mining activities have started since the 1990′s. In this paper, we used hydrodynamic modelling (TELEMAC-2D) to investigate the estuarine morphological changes and sediment dynamics related to the intensive riverbed mining in the Soai Rap Estuary. After the hydraulic calibration and validation of the model, we simulate four scenarios: two with dredging, one with sand excavation, and a baseline condition. Our results show that dredging substantially changed the hydraulic regimes, morphological and sediment dynamics of the estuary. Compared to the baseline, dredging substantially influences flow velocity and tidal amplitude. These activities reduce the amount of sediment accumulating upstream by 18% to 36%, while increasing sediment deposition in the Soai Rap Estuary by 6% to 13%. Furthermore, sediment accumulation in the Ganh Rai Bay area decrease by 5% to 10% due to increased sediment transport from the sea to the estuary. Our modelled results also show that the mining pits (pockmarks) created by sand extractions efficiently trap sediment, causing discontinuities in the longitudinal transport of sediment and resulting morphological patterns. We conclude that the morphology and sediment transport regime of the Soai Rap estuary has been significantly altered by the river sand dredging. As such, we recommend that the local government put in place measures to ensure that sand extraction is carried out sustainably in the future, to minimise further alterations to the natural sedimentation patterns and geomorphology of this estuary.

Organochlorine Compounds in Commercial Bivalves from the Mekong and Saigon–Dong Nai River Deltas (South Vietnam)

Organochlorine Compounds in Commercial Bivalves from the Mekong and Saigon–Dong Nai River Deltas (South Vietnam)

Statistical and Hydrological Evaluations of Water Dynamics in the Lower Sai Gon-Dong Nai River, Vietnam

The water levels downstream of the Sai Gon and Dong Nai river in Southern Vietnam have been significantly changed over the last three decades, leading to severe impacts on urban flooding and salinity intrusion and threating the socio-economic development of the region and lives of many local people. In this study, the Mann-Kendall (MK) and trend-free prewhitening (TFPW) tests were applied to detect the water level trends and changepoints based on a water level time series at six gauging stations that were located along the main rivers to the sea over 1980–2019. The results indicated that the water level has rapidly increased by about 0.17 to 1.8 cm/year at most gauge stations surrounding Ho Chi Minh City, strongly relating to urbanization and the dike polder system’s impacts that eliminates the water storage space. In addition, the operation of upstream reservoirs has contributed to water level changes with significant consequences since the high-water level at Tri An station on the Dong Nai river occurs 1000–1500 times compared to 300–500 times before the operation. Although the effects of the flows from the sea are less than the two other factors, the local government should seriously consider water level changes, especially in the coastal regions. Our study contributes empirical evidence to evaluate the water level trends in the planning and development of infrastructure, which is necessary to adapt to future changes in Southern Vietnam’s hydrologic system.

Assessment of water quality changes in Saigon and Dong Nai rivers under the influence of domestic wastewater discharges

The study was conducted to evaluate the impact of domestic wastewater discharges on surface water quality (BOD5 and DO) at pumping stations on Sai Gon – Dong Nai river during the dry season and the wet season using the MIKE 21FM model. The results indicated that the water quality in Dong Nai river is rated better than the Sai Gon River. Specifically, the BOD5 concentration was high, and the DO concentration was low at Hoa Phu station in Sai Gon River. However, the surface water quality at pumping stations on Dong Nai river, namely Hoa An and Binh An was up to standard compared to column A2 for domestic water supply purposes according to QCVN 08- MT:2015/BTNMT. Specifically, the wastewater source from Thu Dau Mot city on the Sai Gon river was about 4 km from Hoa Phu pumping station with a discharge volume of 0,66 m3/s, and another source from Bien Hoa city on the Dong Nai river reached a discharge volume of 2,15 m3/s, which was about 4.7 km and 5.5 km from Hoa An and Binh An intakes, respectively. The outcomes proved that Hoa Phu and Hoa An pumping stations were not affected by the wastewater from these cities. Otherwise, there was markedly degraded water quality at Binh An intake in the dry season, which was unsatisfied with QCVN 08- MT:2015/BTNMT (A2 type).

Study of flow in Rua island on Dong Nai river using 3D numerical method

Erosion and bank erosion are processes occurring to the riverbed and are issues closely related to the people and society. Rua Island is located in Thanh Hoi commune, Tan Uyen town, Binh Duong province which is one of serious bank erosion areas in the downstream of the Dong Nai river. Riverbank erosion in Rua islet in general has been going on for a long time and the rate of bank erosion has increased after the Tri An hydropower project came into operation and river-bed sand mining activities accelerated. At present, the Rua Islet is in danger of being cut in two at the position of Rua neck. Therefore, researching to determine the mechanism and cause of landslide of Rua Islet in order to point out effective measures to prevent landslide is urgent. A three-dimensional numerical modeling has been developed for the river section in this island to study the flow structure. This model was calibrated with observation data in 2017. Using this model flow in the entire river section was simulated. The calculation results clearly showed the three-dimensional structure of the flow at this river section, especially at the curved sections where bank erosion often occurs. Calculation results also show the distribution of bottom stresse in the river section, it is a parameter that is crucial to the process of changing of the river bed.