Microplastics (MP) are omnipresent in ecosystems. Some studies focus on MP fates and their toxicology on biota for the last ten years in the world. In the present study, MP was identified in bivalve (Perna Viridis) collected in Vietnam for the first time using micro-Fourier transform infrared Microspectroscopy (µFTIR) technique. Organisms were digested by KOH 10% solution then separated using KI 50% solution. The average concentration evaluated at 2.60 MP/individual and 0.29 MP/gram of wet tissue. Six types of MP were found with a high proportion of polypropylene (PP) (31%) and polyester (23%). MP characterizations were also observed which bring to much important information such as the source of MP contamination in bivalve from Vietnam. Nevertheless, more work needs to be invested in the future such as on different species or environment compartments which permit to the global view of MP contamination in Vietnam.
The Red river system is a typical example of Southeast Asian rivers that is strongly impacted by human and climatic conditions, especially in the recent period. In this paper, we aim to investigate the longitudinal variation of the water quality of the Red river, in the section from Hanoi city to the Ba Lat estuary. The sampling campaigns were conducted in the dry seasons in 2017 and 2018. The monitoring results showed that the average concentrations of nutrients (NO2-, NO3-, NH4+, PO43-) were still lower than the allowed values of the Vietnamese standard limits for surface water quality (QCVN 08:2015/BTNMT, column A1) whereas the average concentrations of Cl- and TSS exceeded the allowed values of the QCVN 08:2015/BTNMT, column A1 4.6 and 2.3 times, respectively. NO3- and dissolved silica (DSi) concentrations showed a significant variation from the Hanoi site to the Ba Lat site (6.62 mg/l to 1.19 mg/l for NO3- and 5.21 mg/l to 2.14 mg/l for DSi) whereas SO42-, NO2- and Cl- increased markedly in this longitudinal section, especially from the point SH6 where the salinity started to increase. Based on the three different methods for classification of trophic levels and on the different variables observed during the dry seasons in 2017–2018, the nutrient concentrations of the Red river water tended to slightly increase from the site Hanoi (SH1) to the site SH5 at Nam Dinh, indicating the increase of nutrient external input along the river whereas it tended to decrease from the site SH6 (at mesotrophic/eutrophic level) to the last observed site SH9 (at oligotrophic/mesotrophic level) at the sea due to the dilution of seawater. Seawater in dry season could affect directly the river downstream about 35 km far from the sea. The results may be a guide for planning of water use including agricultural irrigation in the Red river estuary.
This study was conducted from May to November 2017 to evaluate the accumulation of organochlorine pesticide chemicals (OCPs) in fish, Bostrychus sinensis, growing at the Soai Rap estuary, Ho Chi Minh City, Vietnam. The pesticide chemicals in the tissues of fish and the sediments of the estuary were analyzed using a gas chromatography method and Varian GC-450 (ECD) instrument. The results showed that in all tissue samples of fish, the content of DDTs was the highest (9.524 ng/g), followed by aldrin (1.209 ng/g); HCHs (1.972 ng/g); dieldrin (1.743 ng/g) and endosunfans (1.053 ng/g), and the lowest values were Heptachlor (0.807 ng/g) and Eldrin (0.715 ng/g). The content of OCPs in all sediment samples from the study area was found to be lower than Vietnamese standard 43: 2012 /MONRE and some other standards in the world. The bioaccumulation factor of OCPs in the tissue of fish was very low level (BAF < 100), for DDTs at low levels (100 < BAF < 500). The Biota-Sediment Accumulation Factor (BSAF) of the seven substances in the sediment was Dieldrin > DDTs > Aldrin > HCHs > Endosunfans > Heptachlor > Endrin.
Cyanobacteria are photosynthetic microorganisms that have their biosynthesis capacities for secondary compounds with the high application value. They can produce a variety of bioactive compounds such as lipopeptides, fatty acids, toxins, carotenoids, vitamins and plant growth regulators which could be released into the culture medium. The present study aimed to isolate and screen cyanobacteria strains that could synthesize phytohormone, indole-3-acetic acid (IAA) from paddy soild and fresh water ecosystems (canals, river). Soil and water samples were collected from diferent provinces (Bac Giang, Thanh Hoa and Hue). Indole-3-acetic acid was extracted from the culture of isolated cyanobacteria strains and identified using the Salkowski method. As a result, total 10 strains belonging to 4 genera including Nostoc, Anabena, Geitlerinema and Planktothricoides were susscessful isolated from river, canal and rice field. The morphology of isolated taxa was characterized and monoalgal cultures were grown in BG 11 medium. In L-tryptophan-enriched growth media, all cyanobacteria strains in this research were able to biosynthesize growth regulators with IAA concentrations ranging from 9.1 to 95 µg/mL. Among the isolated cyanobacteria strains, the Planktothricoides raciborskii showed potential for the production of IAA even in the absence of tryptophan in the culture medium. Research results of the L-tryptophan concentration effect on the ability of IAA biosynthesis of this cyanobacteria strain showed that IAA concentration increased gradually and reached the highest value (118,28 ± 2,00 µg/mL) when supplementing L- tryptophan in culture medium at 900 µg/mL. The capacity of producing IAA makes these isolated cyanobacteria an appopriate cadidate for agricultural biotechnology.
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