Transitions in diatom assemblages and pigments through dry and wet season conditions in the Red River, Hanoi (Vietnam)

Background and aims – Biomonitoring is an important tool for assessing river water quality, but is not routinely applied in tropical rivers. Marked hydrological changes can occur between wet and dry season conditions in the tropics. Thus, a prerequisite for ecological assessment is that the influence of ‘natural’ hydrological change on biota can be distinguished from variability driven by water quality parameters of interest. Here we aimed to (a) assess seasonal changes in water quality, diatoms and algal assemblages from river phytoplankton and artificial substrates through the dry-wet season transition (February–July 2018) in the Red River close to Hanoi and (b) evaluate the potential for microscopic counts and high-performance liquid chromatography (HPLC) analysis of chlorophyll and carotenoid pigments for biomonitoring in large tropical rivers.Methods – River water (phytoplankton) and biofilms grown on artificial glass substrates were sampled monthly through the dry (February–April) to wet (May–August) season transition and analysed via microscopic and HPLC techniques.Key results – All phototrophic communities shifted markedly between the dry and wet seasons. Phytoplankton concentrations were low (ca. thousands of cells/mL) and declined as the wet season progressed. The dominant phytoplankton taxa were centric diatoms (Aulacoseira granulata and Aulacoseira distans) and chlorophytes (Scenedesmus and Pediastrum spp.), with chlorophytes becoming more dominant in the wet season. Biofilm diatoms were dominated by Melosira varians, and areal densities declined in the wet season when fast-growing pioneer diatom taxa (e.g. Achnanthidium minutissimum, Planothidium lanceolatum) and non-degraded Chlorophyll a concentrations increased, suggesting active phytobenthos growth in response to scour damage. Otherwise, a-phorbins were very abundant in river seston and biofilms indicating in situ Chlorophyll a degradation which may be typical of tropical river environments. The very large range of total suspended solids (reaching > 120 mg L-1) and turbidity appears to be a key driver of photoautotrophs through control of light availability.Conclusions – Hydrological change and associated turbidity conditions exceed nutrient influences on photoautotrophs at inter-seasonal scales in this part of the Red River. Inter-seasonal differences might be a useful measure for biomonitoring to help track how changes in suspended solids, a major water quality issue in tropical rivers, interact with other variables of interest

Genome evolution of dengue virus serotype 1 under selection by <i>Wolbachia pipientis</i> in <i>Aedes aegypti</i> mosquitoes.

The introgression of antiviral strains of Wolbachia into Aedes aegypti mosquito populations is a public health intervention for the control of dengue. Plausibly, dengue virus (DENV) could evolve to bypass the antiviral effects of Wolbachia and undermine this approach. Here, we established a serial-passage system to investigate the evolution of DENV in Ae. aegypti mosquitoes infected with the wMel strain of Wolbachia. Using this system, we report on virus genetic outcomes after twenty passages of serotype 1 of DENV (DENV-1). An amino acid substitution, E203K, in the DENV-1 envelope protein was more frequently detected in the consensus sequence of virus populations passaged in wMel-infected Ae. aegypti than wild-type counterparts. Positive selection at residue 203 was reproducible; it occurred in passaged virus populations from independent DENV-1-infected patients and also in a second, independent experimental system. In wild-type mosquitoes and human cells, the 203K variant was rapidly replaced by the progenitor sequence. These findings provide proof of concept that wMel-associated selection of virus populations can occur in experimental conditions. Field-based studies are needed to explore whether wMel imparts selective pressure on DENV evolution in locations where wMel is established

Refined cut-off for TP53 immunohistochemistry improves prediction of TP53 mutation status in ovarian mucinous tumors: implications for outcome analyses.

TP53 mutations are implicated in the progression of mucinous borderline tumors (MBOT) to mucinous ovarian carcinomas (MOC). Optimized immunohistochemistry (IHC) for TP53 has been established as a proxy for the TP53 mutation status in other ovarian tumor types. We aimed to confirm the ability of TP53 IHC to predict TP53 mutation status in ovarian mucinous tumors and to evaluate the association of TP53 mutation status with survival among patients with MBOT and MOC. Tumor tissue from an initial cohort of 113 women with MBOT/MOC was stained with optimized IHC for TP53 using tissue microarrays (75.2%) or full sections (24.8%) and interpreted using established criteria as normal or abnormal (overexpression, complete absence, or cytoplasmic). Cases were considered concordant if abnormal IHC staining predicted deleterious TP53 mutations. Discordant tissue microarray cases were re-evaluated on full sections and interpretational criteria were refined. The initial cohort was expanded to a total of 165 MBOT and 424 MOC for the examination of the association of survival with TP53 mutation status, assessed either by TP53 IHC and/or sequencing. Initially, 82/113 (72.6%) cases were concordant using the established criteria. Refined criteria for overexpression to account for intratumoral heterogeneity and terminal differentiation improved concordance to 93.8% (106/113). In the expanded cohort, 19.4% (32/165) of MBOT showed evidence for TP53 mutation and this was associated with a higher risk of recurrence, disease-specific death, and all-cause mortality (overall survival: HR = 4.6, 95% CI 1.5-14.3, p = 0.0087). Within MOC, 61.1% (259/424) harbored a TP53 mutation, but this was not associated with survival (overall survival, p = 0.77). TP53 IHC is an accurate proxy for TP53 mutation status with refined interpretation criteria accounting for intratumoral heterogeneity and terminal differentiation in ovarian mucinous tumors. TP53 mutation status is an important biomarker to identify MBOT with a higher risk of mortality.KLG is supported by the Victorian Cancer Agency (MCRF15013) and the Australian National Health and Medical Research Council (APP1045783 and #628434). This study was supported by the Peter MacCallum Cancer Foundation. CS is supported by a University of Melbourne Postgraduate Scholarship. DDB is supported by National Health and Medical Research Council of Australia (NHMRC) grants APP1092856 and APP1117044 and by the US National Cancer Institute U54 programme (U54CA209978-04). ELG and SHK are supported through P50 CA136393-10. The following cohorts that contributed to the GAMuT study were supported as follows: CASCADE: Supported by the Peter MacCallum Cancer Foundation AOCS: The Australian Ovarian Cancer Study Group was supported by the U.S. Army Medical Research and Materiel Command under DAMD17-01-1-0729, The Cancer Council Victoria, Queensland Cancer Fund, The Cancer Council New South Wales, The Cancer Council South Australia, The Cancer Council Tasmania and The Cancer Foundation of Western Australia (Multi-State Applications 191, 211 and 182) and the National Health and Medical Research Council of Australia (NHMRC; ID400413 and ID400281). The Australian Ovarian Cancer Study gratefully acknowledges additional support from Ovarian Cancer Australia and the Peter MacCallum Foundation. The AOCS also acknowledges the cooperation of the participating institutions in Australia and acknowledges the contribution of the study nurses, research assistants and all clinical and scientific collaborators to the study. The complete AOCS Study Group can be found at www.aocstudy.org. We would like to thank all of the women who participated in these research programs. OVCARE receives core funding from The BC Cancer Foundation and the VGH and UBC Hospital Foundation. The Gynaecological Oncology Biobank at Westmead is a member of the Australasian Biospecimen Network-Oncology group, which was funded by the National Health and Medical Research Council Enabling Grants ID 310670 & ID 628903 and the Cancer Institute NSW Grants ID 12/RIG/1-17 & 15/RIG/1-16. COEUR: This study uses resources provided by the Canadian Ovarian Cancer Research Consortium’s - COEUR biobank funded by the Terry Fox Research Institute and managed and supervised by the Centre hospitalier de l’Université de Montréal (CRCHUM). The Consortium acknowledges contributions to its COEUR biobank from Institutions across Canada (for a full list see http://www.tfri.ca/en/research/translational-research/coeur/coeur_biobanks.aspx). The following cohorts that contributed to OTTA were supported as follows: AOV: Canadian Institutes of Health Research (MOP-86727), Cancer Research Society (19319). BAV: ELAN Funds of the University of Erlangen-Nuremberg; DOV: NCI/NIH R01CA168758. Huntsman Cancer Foundation and the National Cancer Institute of the National Institutes of Health under Award Number P30CA042014. HAW: U.S. National 19 Institutes of Health (R01-CA58598, N01-CN-55424 and N01-PC-67001); MAY: National Institutes of Health (R01-CA122443, P30-CA15083, P50-CA136393); Mayo Foundation; Minnesota Ovarian Cancer Alliance; Fred C. and Katherine B. Andersen Foundation; SEA: SEARCH team: Mitul Shah, Jennifer Alsopp, Mercedes Jiminez-Linan SEARCH funding: Cancer Research UK (C490/A16561), the Cancer Research UK Cambridge Cancer Centre and the National Institute for Health Research Cambridge Biomedical Research Centres. The University of Cambridge has received salary support for PDPP from the NHS in the East of England through the Clinical Academic Reserve. JBD: Cancer Research UK Institute Group Award UK A22905 and A15601; STA: NIH grants U01 CA71966 and U01 CA69417; SWE: Swedish Cancer foundation, WeCanCureCancer and årKampMotCancer foundation; TVA: Canadian Institutes of Health Research grant (MOP-86727) and NIH/NCI 1 R01CA160669- 01A1; VAN: M.S. Anglesio is funded through a Michael Smith Foundation for Health Research Scholar Award and the Janet D. Cottrelle Foundation Scholars program managed by the BC Cancer Foundation. The Vancouver study cohort (TVAN) is supported by BC’s Ovarian Cancer Research team (OVCARE), the BC Cancer Foundation and The VGH+UBC Hospital Foundation. WMH: National Health and Medical Research Council of Australia, Enabling Grants ID 310670 & ID 628903. Cancer Institute NSW Grants 12/RIG/1-17 & 15/RIG/1-16

Preliminary investigation of nutrient contents in wastewater at some coastal communes of Giao Thuy district, Nam Dinh province

Wastewater, especially non-treated wastewater from different sources is one of causes for surface and ground water pollution. However, the monitoring of wastewater quality has not been regularly implemented. This paper presents the preliminary observation results of the wastewater quality of different sources such as domestic, fishery processing, husbandry, agricultural runoff and irrigation canals in some coastal communes of Giao Thuy district, Nam Dinh province in 2017 - 2018. The results showed variation values of some variables as following: pH: 3.4 to 8.7; DO: 1.1 – 7.6 mg/l; conductivity: 0.01 – > 99.9 S/m; Suspended solids: 7 – 599 mg.L-1; nitrate (NO3-): 0.01-1.74 mgL-1; ammonium (NH4+): 0.01 - 3.99 mgNL-1, phosphate (PO43-): < 0.01– 3.05 mgPL-1, total phosphorus: 0.01 – 5.03 mgPL-1. The values of some variables such as DO, pH, nitrite, ammonium, suspended solids and phosphate at some observation time exceeded the allowed values of the Vietnamese standards for domestic wastewater quality, for industrial wastewater quality and for surface water quality. Among these different wastewaters observed, the higher contents of nutrients were found for domestic wastewater. The results provide a dataset for environmental managers in order to control of wastewater quality, especially for the coastal communes where coastal aquacultural areas are large like Giao Thuy district, Nam Dinh province.Nước thải, đặc biệt là nước thải chưa qua xử lý từ nhiều nguồn thải khác nhau là một trong những nguyên nhân gây ô nhiễm nguồn nước mặt và nước ngầm. Tuy nhiên việc giám sát chất lượng nước, lại chưa được thường xuyên thực hiện. Bài báo trình bày kết quả khảo sát bước đầu về chất lượng nước thải sinh hoạt, chế biến thủy sản, chăn nuôi, nông nghiệp, kênh dẫn tưới tiêu tại một số xã ven biển thuộc huyện Giao Thủy, tỉnh Nam Định trong năm 2017 - 2018. Kết quả khảo sát cho thấy khoảng giá trị của một số thông số như sau: pH 3,4 – 8,7; DO: 1,1 – 7,6 mgL-1; độ dẫn điện: 0,01 – 99,9 S/m; chất rắn lơ lửng: 7 – 599 mg.L-1; nitrat (NO3-): 0.01-1.74 mgL-1; amoni (NH4+): 0.01 - 3.99 mgNL-1; phốtphat (PO43-): <0,01 - 3,05 mgPL-1 và phốtpho tổng số: 0,01 – 5,03 mgL-1. Hàm lượng một số chỉ tiêu như NO2, NH4 +, PO43-, SS tại một số thời điểm đã vượt quá giá trị cho phép theo các quy chuẩn nước thải sinh hoạt, nước thải công nghiệp và nước tưới tiêu. Trong các loại nước thải đã quan trắc, nước thải sinh hoạt có hàm lượng các chỉ tiêu dinh dưỡng cao hơn. Các kết quả nghiên cứu nhằm cung cấp cơ sở dữ liệu cho các nhà quản lý về việc kiểm soát chất lượng nước thải, đặc biệt là các xã ven biển có diện tích nuôi trồng thủy sản khá lớn như huyện Giao Thủy, tỉnh Nam Định

Observation of organic matters concentrations in agricultural runoff in the Red River Delta (Vietnam)

Due to utilization increase of chemical fertilizers and manures and of a large water volume for irrigation, agricultural runoff has significantly accelerated water pollution. The Red River locates in Vietnam where agriculture plays an important role in the country’s economy. This paper presented the observation results of organic matters concentrations in agricultural runoff from different plant fields (vegetable, flower and rice) in the Red River Delta in 2013 -2014. The results showed that DOC concentrations varied in a high range from 1.0 mg.L-1 to 37.1 mg.L-1, averaging 10.2 ± 6.2 mg.L-1 whereas POC concentrations varied from 0.5 to 4.5 mg.L-1, averaging 1.7 ± 0.7 mg.L-1 for a total 104 samples observed. TOC concentrations in water from the vegetable and flower fields (11.7 ± 7.3 mg.L-1 and 12.6 ± 6.0 mg.L-1 respectively) were higher than the one from the rice field (8.5 ± 6.6 mg.L-1). Lower organic matters concentrations were found in the rainy season than in the dry season due to dilution process. The results suggest the needs for regularly monitoring and efforts to control organic matter pollution from agricultural runoff in the Red River basin or other river basins in developing countries.Do sử dụng phân bón và thể tích nước tưới lớn, canh tác nông nghiệp đã và đang góp phần đáng kể gây ô nhiễm nguồn nước. Sông Hồng nằm ở Việt Nam, nơi ngành nông nghiệp đóng vai trò quan trọng trong nền kinh tế. Bài báo trình bày kết quả quan trắc hàm lượng cacbon hữu cơ (TOC) bao gồm dạng hòa tan (DOC) và không tan (POC), trong nước chảy tràn từ đất canh tác (rau, hoa, lúa) ở đồng bằng sông Hồng năm 2013 -2014. Kết quả cho thấy DOC thay đổi rất rộng từ 1,0 mg.L-1 đến 37,1 mg.L-1, trung bình đạt 10,2 ± 6,2 mg.L-1 trong khi POC thay đổi từ 0,5 mg. L-1 đến 4,5 mg.L-1, trung bình đạt 1,7 ± 0,7 mg.L-1 đối với 104 mẫu nước. TOC từ trồng rau và hoa (11,7 ± 7,3 mg. L-1 và 12,6 ± 6,0 mg.L-1) cao hơn so với trồng lúa (8,5 ± 6,6 mg. L-1). TOC trong mùa mưa thấp hơn so với mùa khô. Cần thường xuyên giám sát và nỗ lực kiểm soát ô nhiễm chất hữu cơ do nước chảy tràn từ đất canh tác ở lưu vực sông Hồng

Preliminary investigation of nutrient contents in wastewater at some coastal communes of Giao Thuy district, Nam Dinh province

Wastewater, especially non-treated wastewater from different sources is one of causes for surface and ground water pollution. However, the monitoring of wastewater quality has not been regularly implemented. This paper presents the preliminary observation results of the wastewater quality of different sources such as domestic, fishery processing, husbandry, agricultural runoff and irrigation canals in some coastal communes of Giao Thuy district, Nam Dinh province in 2017 - 2018. The results showed variation values of some variables as following: pH: 3.4 to 8.7; DO: 1.1 – 7.6 mg/l; conductivity: 0.01 – > 99.9 S/m; Suspended solids: 7 – 599 mg.L-1; nitrate (NO3-): 0.01-1.74 mgL-1; ammonium (NH4+): 0.01 - 3.99 mgNL-1, phosphate (PO43-): < 0.01– 3.05 mgPL-1, total phosphorus: 0.01 – 5.03 mgPL-1. The values of some variables such as DO, pH, nitrite, ammonium, suspended solids and phosphate at some observation time exceeded the allowed values of the Vietnamese standards for domestic wastewater quality, for industrial wastewater quality and for surface water quality. Among these different wastewaters observed, the higher contents of nutrients were found for domestic wastewater. The results provide a dataset for environmental managers in order to control of wastewater quality, especially for the coastal communes where coastal aquacultural areas are large like Giao Thuy district, Nam Dinh province.Nước thải, đặc biệt là nước thải chưa qua xử lý từ nhiều nguồn thải khác nhau là một trong những nguyên nhân gây ô nhiễm nguồn nước mặt và nước ngầm. Tuy nhiên việc giám sát chất lượng nước, lại chưa được thường xuyên thực hiện. Bài báo trình bày kết quả khảo sát bước đầu về chất lượng nước thải sinh hoạt, chế biến thủy sản, chăn nuôi, nông nghiệp, kênh dẫn tưới tiêu tại một số xã ven biển thuộc huyện Giao Thủy, tỉnh Nam Định trong năm 2017 - 2018. Kết quả khảo sát cho thấy khoảng giá trị của một số thông số như sau: pH 3,4 – 8,7; DO: 1,1 – 7,6 mgL-1; độ dẫn điện: 0,01 – 99,9 S/m; chất rắn lơ lửng: 7 – 599 mg.L-1; nitrat (NO3-): 0.01-1.74 mgL-1; amoni (NH4+): 0.01 - 3.99 mgNL-1; phốtphat (PO43-): <0,01 - 3,05 mgPL-1 và phốtpho tổng số: 0,01 – 5,03 mgL-1. Hàm lượng một số chỉ tiêu như NO2, NH4 +, PO43-, SS tại một số thời điểm đã vượt quá giá trị cho phép theo các quy chuẩn nước thải sinh hoạt, nước thải công nghiệp và nước tưới tiêu. Trong các loại nước thải đã quan trắc, nước thải sinh hoạt có hàm lượng các chỉ tiêu dinh dưỡng cao hơn. Các kết quả nghiên cứu nhằm cung cấp cơ sở dữ liệu cho các nhà quản lý về việc kiểm soát chất lượng nước thải, đặc biệt là các xã ven biển có diện tích nuôi trồng thủy sản khá lớn như huyện Giao Thủy, tỉnh Nam Định

Observation of organic matters concentrations in agricultural runoff in the Red River Delta (Vietnam)

Due to utilization increase of chemical fertilizers and manures and of a large water volume for irrigation, agricultural runoff has significantly accelerated water pollution. The Red River locates in Vietnam where agriculture plays an important role in the country’s economy. This paper presented the observation results of organic matters concentrations in agricultural runoff from different plant fields (vegetable, flower and rice) in the Red River Delta in 2013 -2014. The results showed that DOC concentrations varied in a high range from 1.0 mg.L-1 to 37.1 mg.L-1, averaging 10.2 ± 6.2 mg.L-1 whereas POC concentrations varied from 0.5 to 4.5 mg.L-1, averaging 1.7 ± 0.7 mg.L-1 for a total 104 samples observed. TOC concentrations in water from the vegetable and flower fields (11.7 ± 7.3 mg.L-1 and 12.6 ± 6.0 mg.L-1 respectively) were higher than the one from the rice field (8.5 ± 6.6 mg.L-1). Lower organic matters concentrations were found in the rainy season than in the dry season due to dilution process. The results suggest the needs for regularly monitoring and efforts to control organic matter pollution from agricultural runoff in the Red River basin or other river basins in developing countries.Do sử dụng phân bón và thể tích nước tưới lớn, canh tác nông nghiệp đã và đang góp phần đáng kể gây ô nhiễm nguồn nước. Sông Hồng nằm ở Việt Nam, nơi ngành nông nghiệp đóng vai trò quan trọng trong nền kinh tế. Bài báo trình bày kết quả quan trắc hàm lượng cacbon hữu cơ (TOC) bao gồm dạng hòa tan (DOC) và không tan (POC), trong nước chảy tràn từ đất canh tác (rau, hoa, lúa) ở đồng bằng sông Hồng năm 2013 -2014. Kết quả cho thấy DOC thay đổi rất rộng từ 1,0 mg.L-1 đến 37,1 mg.L-1, trung bình đạt 10,2 ± 6,2 mg.L-1 trong khi POC thay đổi từ 0,5 mg. L-1 đến 4,5 mg.L-1, trung bình đạt 1,7 ± 0,7 mg.L-1 đối với 104 mẫu nước. TOC từ trồng rau và hoa (11,7 ± 7,3 mg. L-1 và 12,6 ± 6,0 mg.L-1) cao hơn so với trồng lúa (8,5 ± 6,6 mg. L-1). TOC trong mùa mưa thấp hơn so với mùa khô. Cần thường xuyên giám sát và nỗ lực kiểm soát ô nhiễm chất hữu cơ do nước chảy tràn từ đất canh tác ở lưu vực sông Hồng

Microbial contamination in the surface water in the Ba Vi National Park, Ha Noi

Ba Vi National Park, one of 28 Vietnam National parks, is currently preserved and exploited for a variety of purposes, including the preservation of intact natural forest ecosystems and genetic resources of rare plants and animals. This paper presents the monitoring results of microbial contamination in surface water environment of the Ba Vi National Park (Ha Noi) in the period 2013-2014 and 2018. The results showed that total coliform (TC) density varied from 23 to 11,000 MPN/100ml in bimonthly observation in 2013-2014 which was lower than that one of sampling campaign in 2018, from 900 MPN/100ml to 8,100 MPN/ml. Fecal coliform (FC) densities vaired from 0 to 110 MPN/100ml in 2013 -2014 were lower than that in 2018, from 0 MPN/100ml to 600 MPN/100ml. At several observation time, both TC and FC were higher than the allowable values of the Vietnam national technical regulation QCVN 08-MT: 2015/BTNMT column A1 for surface water quality. The exceeded values of TC and FC than the allowable values and the increase trend from the 2013 to 2018 periods indicated the potential risks to the public health in this region when people use water for domestic and agricultural purposes. Our results provide dataset for environmental management in the Ba Vi National Park in order to protect the eco-environment in parallel with economical-social development.Vườn Quốc gia Ba Vì, một trong 28 vườn quốc gia của Việt Nam hiện đang được bảo tồn và khai thác cho nhiều mục đích, trong đó có bảo tồn nguyên vẹn các hệ sinh thái rừng tự nhiên, các nguồn gen động, thực vật quý hiếm, các đặc sản rừng và các di tích lịch sử, cảnh quan tự nhiên trong vùng. Bài báo trình bày kết quả quan trắc, đánh giá mức độ ô nhiễm vi sinh vật trong môi trường nước mặt tại Vườn Quốc Gia Ba Vì, Hà Nội giai đoạn 2013-2014 và 2018. Kết quả cho thấy mật độ coliform tổng số (TC) biến đổi trong khoảng từ 23 – 11.000 MPN/100ml trong các đợt quan trắc định kỳ 2 tháng/lần trong hai năm 2013 - 2014 và trong khoảng từ 900 – 8.100 MPN/100ml trong một đợt quan trắc năm 2018. Mật độ fecal coliform (FC) biến đổi trong khoảng từ 0 - 110 MPN/100ml năm 2013 -2014 và từ 0 - 600 MPN/100ml vào năm 2018. Vào một số thời điểm quan trắc, mật độ FC và TC vượt giá trị cho phép của quy chuẩn kỹ thuật Quốc Gia QCVN 08-MT:2015/BTNMT cột A1 về chất lượng nước mặt. Các giá trị TC và FC vượt quá giá trị cho phép và xu hướng gia tăng TC và FC từ 2013 -2018 cho thấy nguy cơ tiềm tàng khi người dân sử dụng nguồn nước này cho các mục đích sinh hoạt và nông nghiệp. Như vậy, kết quả của nghiên cứu này nhấn mạnh nhu cầu giám sát thường xuyên chất lượng nước và cần thực hiện các giải pháp hiệu quả để xử lý và quản lý nguồn gây ô nhiễm trong khu vực nhằm bảo vệ môi trường sinh thái song song với phát triển kinh tế - xã hội của khu vực

Seasonal and spatial variation in biodegradability of organic carbon along the Red River, Vietnam

The biodegradability of organic carbon in aquatic ecosystems has been broadly attributed to a variety of interacting physical, chemical and biological factors and processes. The Red River is the second largest river in Vietnam. It also constitutes the main source of water for a large percentage of the population of North Vietnam, however, little has been published on the variation in biodegradability of organic matter in this ecosystem, despite its importance in terms of carbon export to the adjacent coastal ocean. Here, we present the results of an investigation into seasonal and spatial variations of the biodegradability of organic carbon in the Red River basin, North Viet Nam. Biodegradability of DOC (BDOC) and POC (BPOC) seasonally differed at the four stations investigated. BDOC concentrations ranged from 0.2 − 2.84 mgCl−1 and BPOC concentrations fluctuated from 0.02 − 2.6 mgCl−1. In the biphasic degradation, the degradation constant for the labile fraction of DOC (k1) varied between 0.0036 and 0.6357, with values being significantly higher (p < 0.014) during the rainy season than during the dry season. In contrast, no significant difference (p = 0.352) in the biodegradability of the POC labile fraction was observed. In general, the average observed in our study values of the biodegradable fraction of particulate was lower than BDOC, BPOC ranged from 16% to 39%, with biodegradability of total organic carbon (BTOC) ranging from 33% to 44%. The higher rainy %BDOC (49%) than dry season (29%) in watersheds dominated by wetlands

Establishing an empirical equation for the relationship between total suspended solids and total phosphorus concentrations in the downstream Red river water

Recently, the Asian rivers have faced the strong reduction of riverine total suspended solids (TSS) flux due to numerous dam/reservoir impoundment. The Red river system is a typical example of the Southeast Asian rivers that has been strongly impacted by reservoir impoundment in both China and Vietnam, especially in the recent period. It is known that the reduction in total suspended solids may lead to the decrease of some associated elements, including nutrients (N, P, Si) which may affect coastal ecosystems. In this paper, we establish the empirical relationship between total suspended solids and total phosphorus concentrations in water environment of the Red river in its downstream section from Hanoi city to the Ba Lat estuary based on the sampling campaigns conducted in the dry and wet seasons in 2017, 2018 and 2019. The results show a clear relationship with significant coefficient between total suspended solids and total phosphorus in the downstream Red river. It is expressed by a simple equation y = 0.0226x0.3867 where x and y stand for total suspended solids and total phosphorus concentrations (mg/l) respectively with the r2 value of 0.757. This equation enables a reasonable prediction of total phosphorus concentrations of the downstream Red river when the observed data of total suspended solids concentrations are available. Thus, this work opens up the way for further studies on the calculation of the total phosphorus over longer timescales using daily available total suspended solids values