Publications by authors named "Julien Némery"

7 Publications

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Sedimentological and geochemical data in bed sediments from a tropical river-estuary system impacted by a developing megacity, Ho Chi Minh City - Vietnam.

Data Brief 2020 Aug 27;31:105938. Epub 2020 Jun 27.

CARE, Ho Chi Minh City University of Technology, VNU-HCM, Viet Nam.

Sedimentological and geochemical data were obtained for bed sediments from a tropical estuary environment in Vietnam in October 2014, January 2016, and November 2016. The data include grain-size distribution, percentage of clay, silt and sand, percentage of organic matter, concentration of total particulate phosphorus (TPP), concentration of particulate inorganic phosphorus (PIP), concentration of particulate organic phosphorus (POP), percentage of total nitrogen (TN), percentage of total carbon (TC), trace metals concentrations (V, Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Pb) and major elements (Al, Fe, Mn). Geochemical indexes (Enrichment factor EF and Geo-accumulation Index I-geo) and sediment quality guideline (mean Effect Range Median quotients) were calculated.
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http://dx.doi.org/10.1016/j.dib.2020.105938DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7339034PMC
August 2020

Nutrient dynamics and eutrophication assessment in the tropical river system of Saigon - Dongnai (southern Vietnam).

Sci Total Environ 2019 Feb 26;653:370-383. Epub 2018 Oct 26.

CARE, Ho Chi Minh City University of Technology, VNU-HCM, Viet Nam.

Saigon-Dongnai Rivers in Southern Vietnam is a complex lowland hydrological network of tributaries that is strongly influenced by the tidal cycles. The increasing economic, industrial and domestic developments in and around Ho Chi Minh City (HCMC) have led to serious impacts on water quality due to lack of appropriate wastewaters treatment. Drinking water production is impacted and the large aquaculture production areas may also be affected. We analyzed spatial and seasonal variability of nutrient concentrations (Phosphorus, Nitrogen and Silica) and eutrophication indicators (Organic Carbon, Chlorophyll-a and Dissolved Oxygen) based on bi-monthly monitoring during two hydrological cycles (July 2015-December 2017). Four monitoring sites were selected to assess the impact of HCMC: two upstream stations on the Saigon River and Dongnai River branches to provide the reference water quality status before reaching the urbanized area of HCMC; one monitoring station in the city center to highlight Saigon River water quality within the heart of the megacity; the fourth station downstream of the confluence to evaluate the impact of HCMC on the estuarine waters. This study points to excess nutrients in HCMC's water body with concentrations of NH and PO averaging to 0.7 ± 0.6 mgN L and 0.07 ± 0.06 mgP L, respectively in mean over the monitored period and rising up to 3 mgN L and 0.2 mgP L, in extreme conditions. During the dry season, we evidenced that untreated domestic discharges leads to degradation of the Saigon River's water quality with extreme values of algal biomass (up 150 μChl-a L) and hypoxic conditions occurring episodically (DO < 2 mg L) in the heart of the megacity. Until now, eutrophication in the urban center has had no clear effect downstream because eutrophic water mass from the Saigon River is efficiently mixed with the Dongnai River and sea water masses during the successive semi-diurnal tidal cycles.
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http://dx.doi.org/10.1016/j.scitotenv.2018.10.319DOI Listing
February 2019

Atmospheric nitrate export in streams along a montane to urban gradient.

Sci Total Environ 2018 Aug 23;633:329-340. Epub 2018 Mar 23.

Université Grenoble Alpes, CNRS, LECA, F-38000 Grenoble, France; Université Savoie Mont Blanc, INRA, CARRTEL, F-74200 Thonon-Les Bains, France.

Nitrogen (N) emissions associated with urbanization exacerbate the atmospheric N influx to remote ecosystems - like mountains -, leading to well-documented detrimental effects on ecosystems (e.g., soil acidification, pollution of freshwaters). Here, the importance and fate of N deposition in a watershed was evaluated along a montane to urban gradient, using a multi-isotopic tracers approach (ΔO, δN, δO of nitrate, δH and δO of water). In this setting, the montane streams had higher proportions of atmospheric nitrate compared to urban streams, and exported more atmospheric nitrate on a yearly basis (0.35 vs 0.10 kg-Nhayr). In urban areas, nitrate exports were driven by groundwater, whereas in the catchment head nitrate exports were dominated by surface runoff. The main sources of nitrate to the montane streams were microbial nitrification and atmospheric deposition, whereas microbial nitrification and sewage leakage contributed most to urban streams. Based on the measurement of δN and δO-NO, biological processes such as denitrification or N assimilation were not predominant in any streams in this study. The observed low δN and δO range of terrestrial nitrate (i.e., nitrate not coming from atmospheric deposition) in surface water compared to literature suggests that atmospheric deposition may be underestimated as a direct source of N.
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http://dx.doi.org/10.1016/j.scitotenv.2018.03.141DOI Listing
August 2018

How can water quality be improved when the urban waste water directive has been fulfilled? A case study of the Lot river (France).

Environ Sci Pollut Res Int 2018 Apr 15;25(12):11924-11939. Epub 2018 Feb 15.

Université de Bordeaux, UMR 5805 EPOC-OASU-allée Geoffroy Saint-Hilaire, 33615, Pessac, France.

The Lot river, a major tributary of the downstream Garonne river, the largest river on the Northern side of the Pyrenees Mountains, was intensively studied in the 1970s. A pioneering program called "Lot Rivière Claire" provided a diagnosis of water quality at the scale of the whole watershed and proposed an ambitious program to manage nutrient pollution and eutrophication largely caused by urban wastewater releases. Later on, the implementation of European directives from 1991 to 2000 resulted in the nearly complete treatment of point sources of pollution in spite of a doubling of the basin's population. At the outlet of the Lot river, ammonium and phosphate contamination which respectively peaked to 1 mg N-NH L and 0.3 mg P-PO L in the 1980s returned to much lower levels in recent years (0.06 mg N-NH L and 0.02 mg P-PO L), a reduction by a factor 15. However, during this time, nitrate contamination has regularly increased since the 1980s, from 0.5 to 1.2 mg N-NO L in average, owing to the intensification of agriculture and livestock farming. Application of the Riverstrahler model allowed us to simulate the water quality of the Lot drainage network for the 2002-2014 period. We showed that, with respect to algal requirements, phosphorus and silica are well balanced, but nitrogen remains largely in excess over phosphorus and silica. This imbalance can be problematic for the ecological status of the water bodies. Using the model, for simulating various scenarios of watershed management, we showed that improvement of urban wastewater treatment would not result in any significant change in the river's water quality. Even though arable land occupies a rather limited fraction of the watershed area, only the adoption of better farming practices or more radical changes in the agro-food system could reverse the trend of increasing nitrate contamination.
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http://dx.doi.org/10.1007/s11356-018-1428-1DOI Listing
April 2018

Impact of anthropogenic activities on water quality and plankton communities in the Day River (Red River Delta, Vietnam).

Environ Monit Assess 2018 Jan 8;190(2):67. Epub 2018 Jan 8.

MARBEC, IRD, Ifremer, Univ Montpellier, CNRS, Montpellier, France.

Planktons are a major component of food web structure in aquatic ecosystems. Their distribution and community structure are driven by the combination and interactions between physical, chemical, and biological factors within the environment. In the present study, water quality and the community structure of phytoplankton and zooplankton were monthly investigated from January to December 2015 at 11 sampling sites along the gradient course of the Day River (Red River Delta, northern Vietnam). The study demonstrated that the Day River was eutrophic with the average values of total phosphorus concentration 0.17 mg/L, total nitrogen concentration 1.98 mg/L, and Chl a 54 μg/L. Microscopic plankton analysis showed that phytoplankton comprised 87 species belonging to seven groups in which Chlorophyceae, Bacillariophyceae, and Cyanobacteria accounted for the most important constituents of the river's phytoplankton assemblage. A total 53 zooplankton species belonging to three main groups including Copepoda, Cladocera, and Rotatoria were identified. Plankton biomass values were greatest in rainy season (3002.10-3 cell/L for phytoplankton and 12.573 individuals/m for zooplankton). Using principal correspondence and Pearson correlation analyses, it was found that the Day River was divided into three main site groups based on water quality and characteristics of plankton community. Temperature and nutrients (total phosphorus and total nitrogen) are key factors regulating plankton abundance and distribution in the Day River.
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http://dx.doi.org/10.1007/s10661-017-6435-zDOI Listing
January 2018

Spatial variation and risk assessment of trace metals in water and sediment of the Mekong Delta.

Chemosphere 2017 Jul 27;179:367-378. Epub 2017 Mar 27.

Faculty of Environment, HCMUT, Ho Chi Minh City, Viet Nam.

The Mekong Delta, is home to 17 million inhabitants and faces numerous challenges relating to climate change, environmental degradation and water issues. In this study, we assess trace metals concentrations (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Cd, Hg, Pb) in the water, suspended particulate matter and surface sediments of the Tien River, the Northern branch of the Mekong Delta, during both dry and rainy seasons. Metal concentrations in the dissolved and suspended particle phases remain in the low concentration range of the main Asian Tropical River. During transportation in the riverine part, we evidenced that V, Cr, Co, As and Pb are dominant in the particulate phase while Mo, Ni and Cu dominate in the dissolved fraction. In the salinity gradient, dissolved U, V, Mo exhibit conservative behaviour while Ni, Cu, As, Co and Cd showed additive behaviour suggesting desorption processes. In the surface sediment, metal concentrations are controlled by the particle-size, POC contents and Fe, Al and Mn - oxy(hydr)oxides. Calculated Enrichment Factor and Geoaccumulation Index evidenced As enrichment while the calculated mean effect range median quotients evidenced a low to medium ecotoxicological potential effects range in the surface sediments.
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http://dx.doi.org/10.1016/j.chemosphere.2017.03.105DOI Listing
July 2017

Baseline seasonal investigation of nutrients and trace metals in surface waters and sediments along the Saigon River basin impacted by the megacity of Ho Chi Minh (Vietnam).

Environ Sci Pollut Res Int 2017 Feb 10;24(4):3226-3243. Epub 2016 Oct 10.

Faculty of Environment, HCMUT, Ho Chi Minh City, Vietnam.

The Saigon River, Southern Vietnam, crosses one of the most dynamic developing Megacity in Southeast Asia: Ho Chi Minh City (HCMC). The increased economic, industrial, and domestic developments may affect the environmental quality of water and halieutic resources. In this study, we evaluated the seasonal (dry and wet seasons) biogeochemical state of the Saigon River during two snapshot campaigns conducted along the river basin upstream from HCMC; the Saigon River was characterized by slightly acidic (pH 5.7-7.7) and oxygen-depleted water (dissolved oxygen (DO), 0.36-5.18 mg l). Nutrients (N-NH = 0.01-2.41, N-NO = 0.14-2.72, and P-PO = ~0-0.42 mg l), DOC (2.2-8.0 mg l), POC, and trace metal(oid) (As, Cd, Cr, Cu, Zn, and Hg) concentrations were low showing a good quality of the upstream river. In the urban center area, DO dropped to 0.03 mg l accompanied with a rise of nutrient concentrations (e.g., N-NH, up to 17.7 mg l) likely originating from wastewater discharges. Trace metal concentrations also rose sharply (e.g., Cr and Hg rose up to 10-fold higher) in both water and sediments but remained under the World Health Organization (WHO) and Vietnamese concentration guidelines. In the downstream estuarine area, the intrusion of marine waters diluted water flowing from HCMC, leading water quality to return close to the state observed upstream from HCMC. In general, levels of nutrient and metal contaminations along the Saigon River during both seasons appear moderate regarding to Vietnamese and WHO guidelines although the urban area is highlighted as the major contributor for metal(oid) emissions. Finally, we showed that apart from wastewater and industrial discharges that affect the river quality, metal(oid) partitioning between solid and solution is controlled by the change in water geochemistry along the continuum during both seasons, such as DO (e.g., for As and Cr) and pH (e.g., for Pb) which drives their sorption/dissolution dynamics.
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http://dx.doi.org/10.1007/s11356-016-7660-7DOI Listing
February 2017