River Surface Water Research Articles

Impact of Snowmelt Conditions on the Isotopic Composition of the Surface Waters of the Upper Ob River during the Flood Period

For many of the Siberian rivers, and the Upper Ob in particular, 70–80% of the volume of the annual water runoff is formed during the spring flood. Thus, factors influencing the formation of water runoff during the spring flood are paramount. We explain changes in the isotopic composition of the Upper Ob surface waters by changing different components’ contribution to the runoff water discharge over the spring flood period. We suggest estimating the time of meltwater flow from the Upper Ob watershed to the outlet section using the difference between the date of the complete melting of the snow cover in the catchment area and the date of the maximum light isotope composition of water in the outlet section. We show that a sharp short-term weighting of the isotopic composition of water in the river at the end of the first phase of the flood may be associated with the influx of autumn soil moisture, displaced from the soils by snowmelt waters.

Mega dam‐induced riverbed erosion exacerbates drought effects on river water surface elevation

AbstractBy regulating the seasonal flow discharge, dams are frequently used to augment downstream flow discharges and water surface elevations in dry season periods. However, dams also typically generate severe bed incision in their downstream reaches, which whilst not reducing the volume of flow passing through the channel, can nevertheless reduce water surface elevations. Such reductions in water surface elevations can make it more difficult to access available water in the river in instances where they drop substantially below the levels of water intake structures. Here, we evaluate the extent to which dam‐induced incision downstream of the Three Gorges Dam (TGD) contributes to falling water surface elevations during the 2019 dry season (December to February), which was a period characterized by extremely low water surface elevations along the mid‐lower reaches of the Changjiang River. Our results indicate that the 2019 dry season exhibited the second lowest water surface elevation ever recorded in the middle Changjiang even though the flow discharge was actually larger than in previous dry seasons. The 2019 event was found to be characterized by a sharp fall of water surface elevation, caused by TGD‐induced downstream channel narrowing and bed incision. Thus, whilst TGD releases did augment flows during the 2019 dry season, channel degradation resulted in a substantial net lowering of water surface elevations. Consequently, the overall impact of the TGD on dry season water surface elevations was to aggravate (not mitigate) low water surface elevations experienced along the Changjiang River. Our study has relevance for other major dam‐altered rivers that experience extreme low water surface elevations in dry periods.

Nanographite: A highly active and durable metal-free ozonation catalyst with application in natural waters

The development of metal-free heterogeneous catalysts for advanced oxidation processes has emerged as a key focus for both academia and industry. We report on research that seeks to establish a correlation between the crystallographic, physicochemical, textural, and morphological properties of a series of graphite-based solids and their activities as metal-free ozonation catalysts in aqueous media. Our findings show that nanographite (NG) outperforms traditional graphite-based solids, activated carbon and Co3O4. The enhanced activity of NG is due to defective nanosized graphitic structures with high surface areas. NG exhibits an exceptional activity, durability, and recyclability that surpasses other known catalysts. Our study employs electron spin resonance and selective quenching experiments that reveal the generation of 1O2 during catalytic ozonation. Significantly, NG shows excellent catalytic efficiency even when using natural surface river water or seawater. This study illustrates the importance of the natural properties of graphite-based materials as active and durable ozonation catalysts in water.

First hydrological study on the seasonal occurrence of glyphosate, glufosinate, and their metabolites in the Red River system, North Vietnam

We report the spatial and seasonal distribution of organophosphorus herbicides, namely glyphosate (GLYP), glufosinate (GLUF), and their respective metabolites aminomethyl phosphonic acid (AMPA) and 3-(methylphosphinico)-propionic acid (MPPA), in the Red River system (North Vietnam), a major water body in Southeast Asia. The four compounds were measured at 34 sampling stations located from upstream to the estuary during the dry (March) and wet (July) seasons in 2019. Large seasonal variations in herbicide concentrations were measured for the four analytes from upstream to the estuary, with the highest range of variations observed during the wet season. In the surface waters of the Red River, the maximum concentrations of GLUF (234 ng L–1), GLYP (565 ng L–1) and its metabolite AMPA (1329 ng L–1), occurred in the wet season. These values however, are lower than reported in other rivers worldwide. In contrast, the estimated fluxes of these compounds in the Red River water basin were very high during the wet season, i.e., up to 121, 50.2, 284, and 186 kg d–1 for GLYP, GLUF, AMPA, and MPPA, respectively. During both seasons, we observed correlations between the four compounds and ammonium (NH4+), suggesting that both nitrogen containing fertilizers and herbicides were applied in areas close to the river shore. The concentrations and fluxes of the herbicides GLYP, GLUF, and their metabolites determined in the Red River were compared to those recorded in other world river systems, such as the Garonne River (France), thus highlighting the importance of monitoring these compounds in surface waters.

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.

Residues, potential source and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in surface water of the East Liao River, Jilin Province, China

The environmental risks posed by polycyclic aromatic hydrocarbons (PAHs) and the diversity of their anthropogenic origins make them a global issue. Therefore, it is of utmost significance for protecting the aquatic environment and the growth of neighboring populations to identify their possible origins and ecological risk. Here, we detail the contamination profiles of 15 PAHs found in the East Liao River's surface waters in Jilin Province and use the receptor model Absolute Principal Component Analysis - Multiple Linear Regression (APCS-MLR) and diagnostic ratios method to identify the primary potential sources of pollution. Based on the natural hazard risk formation theory (NHRFT), an ecological risk assessment (ERA) model for PAHs in the East Liao River was developed. The method assesses the ecological risk status of PAHs by integrating the risk quotient (RQ) approach and the DPSIRM (driving force, pressure, state, impact, response, management) conceptual framework. Total concentrations in the surface water body were between 396.42 and 624.06 ng/L, with an average of 436.99 ng/L. The source research revealed that coal, biomass, and traffic emission sources are the most likely PAH contributors to the East Liao River. The ERA found that the majority of the sites' locations of the study were at low risk for PAHs in surface water bodies (30.7 % and 32.2 %, respectively), while only a tiny percentage of sites were at high or very high risk (1.8 % and 13.6 %). The study results provide theoretical support for the East Liao River's ecological, environmental protection, and policy formulation.

Estimation of nitrogen and phosphorus fluxes into a Barrier Island lagoon via meteoric groundwater discharge

Meteoric groundwater discharge (MGD) to coastal regions transports terrestrial freshwater and nutrients that may alter coastal ecosystems by supporting harmful algal blooms. Estimation of MGD-driven nutrients is crucial to assess potential effects on coastal zones. These estimates require a reliable assessment of MGD rates and pore water nutrient concentrations below subterranean estuaries. To estimate nutrient delivery into a subterranean estuary in the Indian River Lagoon, FL., pore water and surface water samples were collected from nested piezometers along a selected transect on five sampling episodes. Groundwater hydraulic head and salinity were measured in thirteen onshore and offshore piezometers. Numerical models were developed, calibrated, and validated using SEAWAT to simulate MGD flow rates. Lagoon surface water salinity exhibits no spatial but mild temporal variation between 21 and 31. Pore water salinity shows tremendous variation in time and space throughout the transect except in the middle region of the lagoon which exhibits uniform but elevated salinities up to 40. Pore water salinity as low as that of freshwater happens to occur in the shoreline regions during most of the sampling episodes. Both pore water and surface water show remarkably higher total nitrogen TN than total phosphorus TP concentrations and most TN is exported as NH4, reflecting the effect of mangroves on the geochemical reactions that reduce NO3 into NH4. Nutrient contributions of pore water and lagoon water exceed the Redfield TN/TP molar ratio in all sampling trips by up to a factor of 48 and 4, respectively. Estimated TP and TN fluxes receives by the lagoon via MGD are 41–106 and 113–1478 mg/d/m of shoreline. The molar TN/TP ratio of nutrient fluxes exceeds the Redfield ratio by a factor of up to 3.5 which indicates the potential of MGD-driven nutrients to alter the lagoon water quality and support harmful algal blooms.

The habitat of Varuna litterata in the bengawan solo river

Varuna litterata is a crab that belongs to the Varunidae and has been caught to fulfill the need for the availability of an animal protein source. The purpose of this study was to determine the existing habitat of V. litterata in the Bengawan Solo River Estuary. Sampling of V. litterata was carried out every month for five months in three stations by using fixed nets. Water and substrate quality parameters were measured and examined. The samples of V. litterata that had been obtained were then counted and differentiated based on sex and size. The morphological characteristics were then recorded. The sample was then weighed, the width and length of the carapace were measured. The results showed that the abundance of V. litterata was even at each station. The carapace width distribution was dominated by 3.5-3.99 cm in size. The ratio of male and female individuals is still in balance. The results of this study indicated that V. litterata can be found in waters that are directly opposite the sea and spread as far as 32 km from the estuary. V. litterata can be found in waters that are still affected by tidal currents with salinity ranging from 20-25 ppt, temperature ranging from 31-33.2, river surface water current ranging from 0, 39-0,52 m/s with a textured bottom consisting of silty, clayey, sandy, and muddy.

Occurrence and characteristics of microplastics in surface water and sediment of Zayandeh-rud river, Iran

Background: Zayandeh-rud river is the most important river in the central regions of Iran and the present study aimed to provide new insights into microplastics (MPs) pollution in surface water and sediments of this river. Methods: Water and sediment samples were collected in July 2021 from 19 sampling sites along the river. Organics matters were removed from the samples by wet peroxide oxidation (WPO), and MPs were extracted by floatation in ZnCl2 -saturated salt and filtration on a polytetrafluoroethylene (PTFE) membrane filter. Trapped MPs on the filter were counted and qualified by a stereomicroscope. Results: MPs were found in 13 sites from 19 sampling sites along the river. The minimum and maximum levels of MPs in water samples were 0 and 51±16.5 particles/m3 , respectively. MPs also were detected in the sediments of all sampling sites except the first two sampling sites (the maximum level was 58±25.9 particles/kg as dry sediment). Fragments were the most common shape of MPs in both water and sediment samples. 72.3% of MPs detected in water samples were 1-5 mm in size, while this percentage for sediment was 49.2%. The five main polymer types found in water and sediment samples were polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Conclusion: These levels of MPs in the water and sediments of Zayandeh-rud river and longtime persistence of plastics in the environment is a significant threat to environmental and human health and need serious attention to restrict MPs release into the river.

A Framework for Estimating Global River Discharge From the Surface Water and Ocean Topography Satellite Mission

AbstractThe Surface Water and Ocean Topography (SWOT) mission will vastly expand measurements of global rivers, providing critical new data sets for both gaged and ungaged basins. SWOT discharge products (available approximately 1 year after launch) will provide discharge for all river that reaches wider than 100 m. In this paper, we describe how SWOT discharge produced and archived by the US and French space agencies will be computed from measurements of river water surface elevation, width, and slope and ancillary data, along with expected discharge accuracy. We present for the first time a complete estimate of the SWOT discharge uncertainty budget, with separate terms for random (standard error) and systematic (bias) uncertainty components in river discharge time series. We expect that discharge uncertainty will be less than 30% for two‐thirds of global reaches and will be dominated by bias. Separate river discharge estimates will combine both SWOT and in situ data; these “gage‐constrained” discharge estimates can be expected to have lower systematic uncertainty. Temporal variations in river discharge time series will be dominated by random error and are expected to be estimated within 15% for nearly all reaches, allowing accurate inference of event flow dynamics globally, including in ungaged basins. We believe this level of accuracy lays the groundwork for SWOT to enable breakthroughs in global hydrologic science.

Seasonal Assessment of Ecological and Human Health Risks of Trace Metals in the Saigon River Surface Water, Vietnam

AbstractRiver water pollution with potentially toxic elements can be quantified via hydrological studies, while its potential impacts on the ecosystem and human health can be assessed via the indices of ecological risk (RI) and human health hazard (HI). This study aims to assess potential ecological and human health risks of trace‐element pollution of the Saigon River surface water, based on seasonal, position, and tidal changes. Surface water samples are taken during dry and rainy seasons and analyzed for Cu, Cr, Mn, Pb, Ni, and Zn. The trace‐element concentrations are used to compute RI and HI. Of the six elements, Cu accounted for 87.7 and 12.5% of the total variance of RI and HI, respectively. The RI and HI values are strongly correlated and are higher in dry season than in rainy season. The HI value of >1 for children suggests that children's health may be sensitive to the adverse impacts of the current status of the trace‐element pollution. Overall, the trace‐element pollution of the river surface water is at a moderate ecological risk in dry season but at a low ecological risk in rainy season. The potentially hazardous elements can have detrimental impacts on children's health in both seasons.

Characterisation of Neonicotinoid Insecticides in the Cocoa-producing Owena River Basin of Nigeria by a QuEChERS Method Coupled to Liquid Chromatography-Tandem Mass Spectrometry

Background: Neonicotinoids (hereafter called “neonics”) are systemic insecticides used for the protection of agricultural crops. However, their dispersion in nature has been the subject of global concern due to reports of adverse effects on some living organisms. One of the applications of neonics in Nigeria is to protect the cocoa cash crop. Objective: Previous studies on pesticide-related pollution in Nigeria focused mainly on organochlorines, but research on neonics is sparse, and the knowledge gap needs to be filled. This work aimed at confirming the presence of four neonics, namely, imidacloprid, thiacloprid, acetamiprid, and thiamethoxam, within the Owena River Basin. Methods: Neonics were extracted from cocoa-growing soil, river water, and sediments by a modified QuEChERS method, followed by clean-up of the extractant by dispersive solid phase extraction and analysis by an optimized liquid chromatography/tandem mass spectrometry analytical procedure. The overall performance of these developed methods was then evaluated by set criteria. Results: The Limit of Detection (LOD) and Limit of Quantitation (LOQ) ranged from 0.0005 to 0.002 μg/g and 0.002 to 0.005 μg/g, respectively. The recovery for the four target analytes exceeded 75% across all matrices from laboratory-prepared samples. It was discovered that the average concentrations of three of the four neonics of interest in the individual media were: 10.34 nmol/g in cocoa-producing soil, 1.03 nmol/g in river sediment, and 1.08 nM (1.08 x 10-3 nmol/g) in surface river water. No imidacloprid was identified in any of these three environmental compartments. Conclusion: The concentration of neonics in the river water, i.e., 0.23 µg/L (230 ng/L), is identical to that of the maximum value recommended in the Canadian Water Quality Guidelines for the Protection of Freshwater Aquatic Life.

Estimating the Relative Impact of Measurement, Parameter, and Flow Law Errors on Discharge from the Surface Water and Ocean Topography Mission

Abstract The Surface Water and Ocean Topography (SWOT) mission will allow the estimation of discharge in rivers wider than 100 m, filling important gaps in the network of in situ measurements. This novel source of discharge observations has the potential to enable significant progress toward closing Earth’s water budget and creating new understanding of the water cycle. Quantifying the uncertainty in the SWOT estimates of discharge, mapping the error sources, and understanding their relative importance is essential to the fulfillment of this potential. Here, we break the SWOT discharge production process into its essential parts: 1) retrieval of river width and water surface heights and slopes, 2) estimation of unobservable parameters, and 3) computation of discharge with the selected flow law, and through a Monte Carlo simulation study, we assess the sensitivity of the overall discharge error to each of these parts. We analyze the discharge error characteristics in terms of bias, error standard deviation, and the correlation between true and retrieved discharges and map the contribution of the essential discharge production elements to each of the error metrics. Our study revealed that biases in parameters are the most important source of discharge biases, yet we found that a larger than expected fraction of the discharge biases can be attributed to observation errors. Surprisingly, we found that parameter biases are also the most important contributor to discharge error standard deviation and to the deterioration of the correlation between truth and retrieved discharges, which were previously thought of as being controlled by observation errors.

Determination of partition coefficients of phthalic acid esters between polydimethylsiloxane and water and its field application to surface waters

Phthalic acid esters (PAEs) or phthalates are endocrine-disrupting chemicals and among the most frequently detected hydrophobic organic pollutants, which can be gradually released from consumer products into the environment (e.g., water). This study measured the equilibrium partition coefficients for 10 selected PAEs, with a wide range of logarithms of the octanol-water partition coefficient (log Kow) from 1.60 to 9.37, between poly(dimethylsiloxane) (PDMS) and water (KPDMSw) using the kinetic permeation method. The desorption rate constant (kd) and KPDMSw for each PAEs were calculated from kinetic data. The experimental log KPDMSw for the PAEs ranges from 0.8 to 5.9, which is linearly correlated with log Kow values up to 8 from the literature (R2 > 0.94); however, it slightly deviated for the PAEs with log Kow values greater than 8. In addition, KPDMSw decreased with the temperature and enthalpy for PAEs partitioning in PDMS-water in an exothermic manner. Furthermore, the effects of dissolved organic matter and ionic strength on the partitioning of PAEs in PDMS were investigated. PDMS was used as a passive sampler to determine the aqueous concentration of plasticizers in river surface water. The results of this study can be used to evaluate the bioavailability and risk of phthalates in real environmental samples.

Hydrochemical Characteristics and Quality Assessment of Surface Water in Sidakan-Balakyan River, Kurdistan Region, NE, Iraq

The hydrochemical characteristics of surface water are studied to understand their source, type of water, and evolution. This study aims to determine the hydrochemical characteristics and controlling factors, by evaluating the water quality of the Sidakan-Balakyan River. The samples were collected along the Sidakan-Balakyan River to the junction point of the Sidakan-Rwanduz Rivers, for each sample, physical (pH, EC, Temperature, Turbidity, TDS and T.H) and chemical parameters (Mg2+, Ca2+, K+, Na+, HCO3-, Cl-, SO42- and NO3-) were analyzed. The results showed that all water samples were within the acceptable range. The results obtained from the Piper and Chadha diagram indicate that the studied water samples during High Flow Period is Mg- Bicarbonate type as well as Ca+2 and SO4-2, whereas during Low Flow Period in Sidakan river is Mg2+- Bicarbonate, But in Balakyan and Rwanduz rivers are Ca2+- Bicarbonate. Moreover, based on Gibbs Diagram, water samples were distributed in the rock weathering dominance section. Based on TDS and T.H of water samples were found to be moderately hard fresh water. Additionally, the river water can not be used for drinking directly. Most samples have a good to excellent water quality index except for some samples which are unsuitable during High Flow Period.

Improving the accuracy of the Water Detect algorithm using Sentinel-2, Planetscope and sharpened imagery: a case study in an intermittent river

ABSTRACT Mapping surface water using remotely sensed optical imagery is a particular challenge in intermittent rivers because water contracts down to narrow linear features and isolated pools, which require accurate water detection methods and reliable image datasets. Of the many methods that use optical sensors to identify water, the Water Detect algorithm stands out as one of the best options due to its classification accuracy, open-source code, and because it does not require ancillary data. However, in the original study, the Water Detect algorithm was only tested with Sentinel-2 imagery. High-resolution and high-frequency imagery, such as Planetscope, combined with sharpening and band synthesizing techniques have the potential to improve the accuracy of surface water mapping, but their benefit to the Water Detect algorithm remains unknown. Uncertainty also exists about the extent to which different input parameters (i.e. maximum clustering and regularization) influence the accuracy of Water Detect. Practitioners seeking to map surface water in intermittent rivers need guidance on a best-practice approach to improve the accuracy of Water Detect. To meet this need, we automated an existing method for sharpening and synthesizing bands and applied it to a series of multispectral Sentinel-2 and Planetscope images. We then developed a sensitivity analysis algorithm that compared the accuracy for all possible combinations of input parameters in a given range for the water detection process – enabling optimal parameters to be identified. We applied this workflow to an 81 km stretch of the lower Fitzroy River (Western Australia) to periods when spatial water extent varied markedly, i.e. mid-wet (February), early-dry (June), and late-dry season (October), across three years with variable wet season flow. We found that the ability to accurately detect surface water using multispectral imagery was increased by using input parameters identified by the sensitivity analysis and using Visible + Near-infrared (VNIR) bands, with relatively little gained by image sharpening unless the area of interest was burnt or experienced considerable shading. Also, the regularization parameter exerted less influence on results than maximum clustering. Importantly, the accuracy of the Water Detect algorithm can vary drastically if input parameters are not calibrated to local conditions. Results also revealed that our approach was adept at detecting linear features in intermittent rivers. We recommend that practitioners using Water Detect to identify surface water undertake a workflow similar to that described here to improve the accuracy of the Water Detect algorithm. The automated routines provided by this study will significantly assist practitioners in doing so. Increasing the accuracy with which we detect and map water in intermittent rivers will improve our understanding and management of these important systems which are under increasing threat.

Effects of irrigation on the fate of microplastics in typical agricultural soil and freshwater environments in the upper irrigation area of the Yellow River

Agricultural activities are among the most significant sources of microplastics (MPs) in water. However, few studies have explored the effect of irrigation on the fate of MPs in agricultural systems. This study investigated the distribution of MPs in agricultural soil, surface water, and sediment of adjacent rivers, as well as the “MP communities” in various environments before and after irrigation in a typical agricultural irrigation area of the Yellow River. MPs were detected in all of the examined sites. The number of MPs in surface water and sediment increased after irrigation, whereas those in the surface soil of croplands decreased. In the vertical direction, irrigation accelerated the migration of MPs (< 100 µm) deep into the soil. The vertical mobility of fibers in soil was faster than that of other types of MPs. Moreover, irrigation decreased the correlation between soil properties and MPs in soils. MP community analysis indicated that irrigation enhanced the differences between MP communities among adjacent environments. Collectively, our findings confirmed that river water irrigation caused secondary MP pollution in the soil environment and accelerated MP pollution in deep soil. Therefore, this study provides a theoretical basis for the development of strategies for MP pollution control in agricultural soil.

Ecohydrological metrics derived from multispectral images to characterize surface water in an intermittent river

Accurately describing the hydrology of intermittent rivers is a critical step in improving our understanding and management of freshwater ecosystems. Traditional approaches such as using gauged discharge data provide little information once flow ceases and no insight into the location, morphology, or persistence of river pools. However, multispectral images can be used to describe surface water, characterize hydrology, and provide insight into ecological functioning. A multispectral approach is highly cost-effective and well suited to remote intermittent rivers with little or no gauging infrastructure. Here, we develop an algorithm to extract hydrological attributes (i.e., pool area, length, perimeter, and mean width) from multispectral imagery (Sentinel-2) and use these attributes to create a suite of ecologically relevant hydrological metrics. We describechanges in attributes and metrics in a large lowland intermittent river as it transitions from wet to dry over a four-year period. We also describe temporal changes in attributes and metrics among five river sections with contrasting hydrological persistence and fragmentation.Our algorithm successfully identified surface water in the main channel and the adjacent floodplain, the centerline of pools, and their upstream and downstream ends. Metrics proved effective at describing seasonal patterns in hydrology; revealing how the size, complexity, and elongation of surface water features (e.g., pools) decreased as the study river transitioned from wet to dry and how fragmentation increased. Metrics also successfully differentiated the river sections with varied hydrological persistence. Ecohydrological metrics derived from multispectral imagery have the potential to provide meaningful insights into riverine morphology, resilience, and ecological functioning. Our spatial approach represents a significant advancement in the ability to characterize and manage intermittent rivers, which are increasingly threatened by water resource development and a drying climate.

Occurrence of Microplastics in River Water in Southern Thailand

Microplastic (MP) contamination in the marine environment has received growing attention. In 2022, the surface water of the U-Taphao River was sampled four times, in February, April, June, and August. The surface water samples were taken at seven different locations, ranging from upstream to downstream parts of the river. The results reveal that the number of MPs detected at the U-Taphao River in February, April, June, and August were 0.41 ± 0.08, 0.25 ±0.06, 0.24 ± 0.11, and 0.26 ± 0.06 particles/L, respectively. The MPs in the U-Taphao River each month were not statistically different (p = 0.190). The trend of the number of MPs found declined from upstream to downstream. Fibers were the most commonly found MPs in the U-Taphao River in this study and were found at more than 80% of all stations during all sample collection periods. Our results indicate that MP contamination is present in the river water, but it is noted that slightly different polymer types were found during each collection month. MPs can be transferred through the food chain and potentially to humans. Regular monitoring of MPs in the riverine system is, therefore, important, for which the findings of the present study can be used as a baseline for the number of MPs in the river water in the region.

Characteristics of integrated mangrove-shrimp farming systems in Ben Tre Province, Vietnam: preliminary findings for organic shrimp production certification

Mangrove forests play a critical role in natural disaster resistance and provide meaningful livelihoods for local communities, especially integrated mangrove shrimp farming (IMSF) systems. Organic shrimp certification actually increases the value chains of shrimp farming in addition to ameliorating mangrove–forest management. Identifying technical issues and assessing environmental risks are the leading concerns when considering organic shrimp production certification. In this study, the technical practices of 30 households were investigated, and surface water and sediment samples were collected in the IMSF models and adjacent rivers in the Thua Duc Forest Management Board area, Ben Tre Province. Data collected from shrimp farming ponds and the environmental background were referred to both the Naturland and National Standards. The results showed that the average mangrove forest and shrimp pond ratio was 56.90:42.70 (%). Two technical issues were highlighted: (i) the use of rotenone, known as a toxin to kill undesirable fish before stocking shrimp, and (ii) annual shrimp pond regeneration causing increased pollution. The data showed that higher concentrations of TSS and P-PO4 3- were detected in surrounding rivers, while surface water in either IMSF ponds or adjacent rivers slightly surpassed the permissible levels of total Fe concentration. All parameters—including heavy metals; toxic and persistent parameters; oil and grease and coliforms analysed in surface water, and sediment samples—were lower than the detection and permissible levels. The results provided evidence that the IMSF’s practices and environmental characteristics were suitable for recommending the Naturland Standards. Recommendations and technical interventions for farmers are necessary to help reduce Fe levels and the safe use of rotenone in IMSF systems. An environmental quality monitoring programme at the target area should be applied when launching organic shrimp production.