Synopsis of myxosporean species (Cnidaria: Myxozoa) parasitizing fishes from Vietnam.

This paper provides an updated checklist of species-level identified myxosporeans from marine and freshwater fishes in Vietnam. The list includes 51 nominal species (38 marine and 13 freshwater) belonging to 9 genera: Myxobolus Bütschli, 1882 (26 species); Kudoa Meglitsch, 1947 (6 species); Henneguya Thélohan, 1892 (6 species); Thelohanellus Kudo, 1933 (5 species); Unicapsula Davis, 1924 (2 species); Ceratomyxa Thélohan, 1892 (2 species), Zschokkella Auerbach, 1909 (2 species); Auerbachia Meglitsch, 1960 (1 species), and Meglitschia Kovaleva, 1988 (1 species). For each parasite species, information on myxospore morphology, line drawings, fish hosts, infection sites, and collection locality in Vietnam are reported. Where available, we also provide GenBank accession numbers for nucleotide sequence data. In addition, taxonomic status of several species was discussed and Myxobolus eszterbaueri nom. nov. is proposed as a junior homonym for Myxobolus hakyi Baska, Voronin, Eszterbauer, Müller, Marton & Molnár 2009, which is preoccupied.

Single-step removal of arsenite ions from water through oxidation-coupled adsorption using Mn/Mg/Fe layered double hydroxide as catalyst and adsorbent.

This study developed a layered double hydroxides (Mn/Mg/Fe-LDH) material through a simple co-precipitation method. The Mn/Mg/Fe-LDH oxidized arsenite [As(III)] ions into arsenate [As(V)] anions. The As(III) and oxidized As(V) were then adsorbed onto Mn/Mg/Fe-LDH. The adsorption process of arseniate [As(V)] oxyanions by Mn/Mg/Fe-LDH was simultaneously conducted for comparison. Characterization results indicated that (i) the best Mg/Mn/Fe molar ratio was 1/1/1, (ii) Mn/Mg/Fe-LDH structure was similar to that of hydrotalcite, (iii) Mn/Mg/Fe-LDH possessed a positively charged surface (pHIEP of 10.15) and low Brunauer-Emmett-Teller surface area (SBET = 75.2 m2/g), and (iv) Fe2+/Fe3+ and Mn2+/Mn3+/Mn4+ coexisted in Mn/Mg/Fe-LDH. The As(III) adsorption process by Mn/Mg/Fe-LDH was similar to that of As(V) under different experimental conditions (initial solutions pH, coexisting foreign anions, contact times, initial As concentrations, temperatures, and desorbing agents). The Langmuir maximum adsorption capacity of Mn/Mg/Fe-LDH to As(III) (56.1 mg/g) was higher than that of As(V) (32.2 mg/g) at pH 7.0 and 25 °C. X-ray photoelectron spectroscopy was applied to identify the oxidation states of As in laden Mn/Mg/Fe-LDH. The key removal mechanism of As(III) by Mn/Mg/Fe-LDH was oxidation-coupled adsorption, and that of As(V) was reduction-coupled adsorption. The As(V) mechanism adsorption mainly involved: (1) the inner-sphere and outer-sphere complexation with OH groups of Mn/Mg/Fe-LDH and (2) anion exchange with host anions (NO3-) in its interlayer. The primary mechanism adsorption of As(III) was the inner-sphere complexation. The redox reactions made Mn/Mg/Fe-LDH lose its original layer structure after adsorbing As(V) or As(III). The adsorption process was highly irreversible. Mn/Mg/Fe-LDH can decontaminate As from real groundwater samples from 45-92 ppb to 0.35-7.9 ppb (using 1.0 g/L). Therefore, Mn/Mg/Fe-LDH has great potential as a material for removing As.

Field demonstration of solar-powered electrocoagulation water treatment system for purifying groundwater contaminated by both total coliforms and arsenic.

People who drink groundwater in rural areas of Southeast Asia are exposed to pathogens and arsenic (As)-related health problems. A water treatment system consisting of electrocoagulation reactors, using iron (Fe) electrodes and a filtration tank, was designed to treat complex contaminated groundwater for drinking. Its applicability was demonstrated near the Red River in Vietnam. The water treatment system reduced 10.3 CFU/mL of total coliform and 376 µg/L of As(III) in the groundwater to 0 CFU/mL and 6.68 µg/L, respectively. Total coliforms were attenuated by Fe(II) infiltration or enmeshed during Fe precipitate formation. Of the total As, 43% formed As(III) complexation with the Fe precipitates and the other 57% was oxidized to As(V) then adsorbed to Fe precipitates. The Fe precipitates, containing total coliforms and As, were separated from the discharge water in the filtration tank. The system required 49 W of power to operate, which equates to 423 kWh/year, to continuously purify 0.5 t water/day. This requirement was powered by a 380-750 W solar panel, without external energy supply, making the water treatment system an appropriate option for addressing drinking water problems in rural areas.

Field Survey and Comparative Study of Pteris Vittata and Pityrogramma Calomelanos Grown on Arsenic Contaminated Lands with Different Soil pH.

In field survey, Pteris vittata and Pityrogramma calomelanos were only found in arsenic (As) contaminated areas with soil pH 7.2-8.8 and 2.3-4.2, respectively. In the first pot experiment, two fern species were grown on the soil amended with 300 mg kg-1 As at soil pH of 5.1, 7.2 and 9. P. calomelanos survived all pH treatments, and had the highest frond As concentration and soil As removal efficiency at soil pH 5.1. All P. vittata plants were dead at soil pH 5.1. P. vittata had higher frond As concentration, biomass and the amount of As removed from the soil than those of P. calomelanos at soil pH of 7.2 and 9. In the second pot experiment, P. vittata was demonstrated to have greater life time, biomass, As tolerance and accumulation than those of P. calomelanos as planted on alkaline soil (pH 7.8) spiked with various concentrations of As.

Accumulation of Indium and other heavy metals by Eleocharis acicularis: an option for phytoremediation and phytomining.

Eleocharis acicularis was exposed to different concentrations of In, Ag, Pb, Cu, Cd, and Zn in the laboratory to assess its capability in accumulating these metals. After 15 days, 477 mg/kg dry wt. of In was accumulated by the roots; concentrations of Ag, Pb, Cu, Cd, and Zn in the shoots were 326, 1120, 575, 195, and 213 mg/kg dry wt., respectively. The results indicate that E. acicularis has the ability to accumulate these metals from water, making it a good candidate species for phytoremediation and phytomining.