Evaluation of fly ash,apatite and rice straw derived-biochar in varying combinations for in situ remediation of soils contaminated with multiple heavy metals

ABSTRACT

In

-situ sorbent amendment is a relatively low-cost, low-impact approach for remediation of soil contaminated with heavy metals (HMs), and thus is considered a way to be favored in developing countries. In this study, materials of non-hazardous, alkaline agronomic and industrial by-products were used as sorbents to explore their capacity of in situ immobilization of multiple HMs in mining-impacted arable soil. These sorbents included fly ash (FA), biochar (BC) and apatite (AP) and they were implemented with varying ratios of combinations. Results of soil microcosm tests showed that after incubation for 90 days, concentrations of Pb, Zn, and Cd in their exchangeable forms determined by a sequential extraction method significantly decreased in amended soils, as opposed to the unamended control. Of the five sets of amendments, the composite of FA, BC, and AP resulted in the maximum reduction (up to 80%) in the mobility of Pb, Zn, and Cd in soils. The mechanisms underlying the immobilization of HMs in amended soils might involve processes of surface precipitation, ion exchange and complexation, in which the physicochemical properties of sorbent materials played an important role. The immobilization efficacy of sorbent amendments on HMs in soil was further supported by pot experiments in which significant inhibition of HM accumulation in the belowground and aboveground tissues of maize was observed after 50-day cultivation in amended soils as compared with control soil. Together, these results suggest that the application of cost-saving and environmentally friendly materials derived from wastes as sorbents to remediate soils contaminated with multiple HMs is promising for developing countries like Vietnam.     

Variable-timing,fixed-rate application of cattle biogas effluent to rice using a leaf color chart: microcosm experiments in Vietnam

ABSTRACT

Livestock production plays a leading role in agricultural land-use change. Producing biogas from livestock waste and subsequently using the biogas effluent as fertilizer for crops is a promising option to solve environmental problems resulting from expanding livestock production. However, it is difficult to promptly and accurately measure the nitrogen (N) concentration of effluent for farmers in developing countries, making precise N management difficult. The objectives of the current study were (1) to evaluate the feasibility of variable-timing, fixed-rate application of cattle biogas effluent using a leaf color chart (LCC) for rice (Oryza sativa L.) and (2) to determine the optimum LCC threshold for grain yield. We conducted two microcosm experiments in the Mekong Delta of Vietnam in 2018 using eight treatments of N-fertilizer application. In the Zero treatment, we applied no N. In the Estd treatment, we split-applied N as effluent (E) at fixed rate and timing as the standard method. In E2.75, E3.00, E3.25, E3.50, and E3.75, we applied effluent whenever the LCC value went below 2.75, 3.00, 3.25, 3.50, and 3.75, respectively. In U3.25, we applied N as urea (U) whenever the LCC value fell below 3.25. The total effluent-N application rate ranged from 90 to 210 kg N ha^?1 season^?1. Rice growth was normal but there was a substantial yield gap between the two microcosm experiments due to the seasonal difference in solar radiation. Rice yield tended to increase with increasing LCC threshold. There was a positive linear relationship between LCC and chlorophyll content (SPAD) values (R ² = 0.73–0.79). Grain yield was well explained (R ² = 0.70–0.89) by the seasonal mean LCC or SPAD value. Plant total N uptake increased with increasing LCC threshold, but the three calculated indices of N use efficiency (NUE) – apparent N recovery, agronomic NUE, and internal NUE – were not always improved with a higher LCC threshold. Our results showed that the tested variable-timing, fixed-rate strategy for the application of cattle biogas effluent was feasible and the optimum LCC threshold for grain production was 3.75 under the current microcosm conditions.     

Anthropogenic Input of Selected Heavy Metals (Cu, Cr, Pb, Zn and Cd) in the Aquatic Sediments of Hochiminh City, Vietnam

The aquatic system of Hochiminh City comprises two main rivers: the Sai Gon and Nha Be rivers. Five canals discharge into these two rivers: NhieuLoc-ThiNghe, TauHu-BenNghe, TanHoa-LoGom, ThamLuong-BenCat and Doi-Te. The rivers and these canals collect effluent water from domestic and industrial sources. Most of these flows are not treated or at most are only primarily treated. A total of 33 sediment cores were taken from these rivers and canals. Chemical composition of these aquatic sediments has very high concentrations of several “urban” metals such as Cd, Cr, Cu and Zn. Most of the samples have exceeded the US EPA’s toxicity reference values for Cu, Zn and Cr (82, 82 and 70%, respectively). The highest concentrations of these metals appear to be associated with the uncontrolled and untreated industrial runoff to the discharge canals. These concentrations in fluvial sediment are relatively low, which indicates the dilution process of the contaminants. This finding indicates that the anthropogenic inputs play an important role in the elevation of heavy metals in the aquatic system and organic matter seems to exert a strong geochemical control on the amount of heavy metals. The Pearson correlation coefficients calculated for Cd, Cr, Cu and Zn, are 0.89; 0.72; 0.93 and 0.87, respectively.     

Assessing in vivo Fertilizing Capacity of Liquid-Preserved Boar Semen According to the 'Hanover Gilt Model'

The goal of this study was to determine the ability of the Hanover gilt model to assess in vivo fertilizing capacity of preserved sperm and to consider whether any modifications to this model were needed. This model evaluates the fertilizing capacity of semen based on the fertilization rate, the rate of normal embryos and the accessory sperm count of 3–5‐day embryos. Its distinguishing characteristics are the use of one‐time insemination of sperm in reduced numbers, of spontaneously ovulating gilts and of ovulation detection through ultrasound examination of ovaries. Reduced sperm numbers allow for an accurate evaluation of the fertilizing potential of different semen treatments, thereby avoiding the compensatory effect of doses calibrated to maximize fertility. The model's usefulness was assessed in a trial run designed to compare the fertilizing capacity of liquid boar semen diluted into two different extenders. The diluent, the boar and the backflow, had no significant effect on any of the parameters studied. Gilts inseminated less than 24 h before ovulation had a significantly higher (p < 0.01) fertilization rate and accessory sperm cell count (p < 0.05) than those inseminated more than 24 h before ovulation. Very good/good embryos from homogeneous litters (only very good/good embryos were present) had a significantly higher (p < 0.01) accessory sperm count than those from heterogeneous litters (at least one embryo was of a different quality and/or oocytes were present). Both very good/good and degenerated/retarded embryos from heterogeneous litters had low accessory sperm numbers. This suggests that accessory sperm count is significantly related to the quality of the litter, but not to the quality of the embryo within gilts. It can be concluded that the Hanover gilt model is sensitive enough to show fertility differences (in this study, those associated with in vivo ageing of semen), while using relatively few gilts and little time.     

Seroprevalence of T. gondii in sheep from Marrakech, Morocco

Toxoplasma gondii is a ubiquitous intracellular protozoan parasite transmitted by food. Concerning this parasite, there are few studies done in Morocco. In this study, 261 sera from sheep intended for consumption in Marrakech were subjected to the Toxoplasma ELISA based serology test for the detection of anti-T. gondii specific IgG confirming a past infection. Of the total tested 72 (27.6%) sera were positive for IgG. This result shows that the seroprevalence approaches the world average and is similar to what is found in other cities of Morocco. This has prompted us to investigate other animal species in the region in order to evaluate the degree of contamination by this parasite as well as the potential risk incurred on consumption of their meat.     

Les vitamines du groupe B dans les aliments végétaux au Sud Vietnam

Résumé Les recherches sur la teneur en vitamines du groupe B (thiamine, riboflavine, nicotinamide) faites sur 135 végétaux alimentaires du Sud Vietnam, montrent que les plantes riches en thiamine sont rares; ce sont surtout les graines et quelques rares feuilles(Sesbania grandiflora Pers. 0,365 mg% de partie comestible) et fruit (pulpe deTamarindus indica L. 0,374 mg %:Durio Zibethinus Murr. 0,300 mg %).Les bonnes sources de riboflavine sont aussi rares mais ce sont essentiellement les légumes à feuilles vertes dont spécialementIpomoea aquatica Forsk. 0,500 mg % et un champignonVolvaria esculenta Massee 0,350 mg %.Enfin la nicotinamide se trouve en quantité importante dans les plantes alimentaires étudiées et sa répartition est assez variée. Les teneurs les plus élevées se trouvent dans les graines comme:Arachis hypogea L. 12 mg %,Citrullus vulgaris Schrad. 8,450 mg %Sesamum indicum L. 5,970 mg %.

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Summary The vitamins of the B group (thiamine, riboflavine, nicotin amide) were analysed in 135 edible plants from South-Vietnam. The plants rich in thiamine are rare; some seeds, rarer leaves(Sesbania grandiflora Pers. 0.365 mg % of the edible part) and fruits (pulp ofTamarus Indica L. 0.374 mg %,Durio Zibethinus Murr 0.3 mg %) were found.The rich sources of riboflavine are equally rare; into the group belong especially green leaves, in particularIpomoea aquatica Forsk, 0.5 mg % and a fungus,Volvaria esculenta Massee 0.35 mg %.Nicotinamide is found in greater quantities in the analysed plants, the allotment being rather great. The greatest amounts have been found in the seeds:Arachis hypogea L. 12 mg %,Citrullus vulgaris Schrad 8.45 mg %Sesamum Indicum L. 5.97 mg %.

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Zusammenfassung Die Vitamine der B-Gruppe (Thiamin, Riboflavin, Nicotinsäureamid) wurden in 135 essbaren Pflanzen aus Süd-Vietnam bestimmt. Thiamin-reiche Pflanzen sind selten: manche Samen, seltener manche Blätter,(Sesbania grandiflora Pers. 0,365 mg % des essbaren Teiles) und Früchte (Fleisch vonTamarindus indica L. 0,374 mg %,Durio Zibethinus Murr 0,3 mg %).Gute Quellen an Riboflavin sind ebenso selten. Solche sind besonders grüne Blätter, namentlich vonIpomoea aquatica Forsk, 0,5 mg %, und ein Pilz,Volvaria esculenta Massee 0,35 mg %.Nicotinsäureamid findet sich in wechselnden Mengen in den untersuchten Pflanzen. Die höchsten Gehalte sind in Samen zu finden:Arachis hypogea L. 12 mg %,Citrullus vulgaris Schrad. 8,45 mg %,Sesamum indicum L. 5,97 mg %.

     

Prevalence of Salmonella spp. in pigs, chickens and ducks in the Mekong Delta, Vietnam

In order to determine the prevalence of Salmonella spp. in domestic animals in 6 provinces of the Mekong Delta, Vietnam, 1,098 fecal or intestinal content samples from pigs, chickens, and ducks were examined in the period from July to October, 2000. Salmonella spp. were isolated from 78 (7.1%) of the total samples, which included 23 (5.2%) of 439 pigs, 24 (7.9%) of 302 chickens, and 31 (8.7%) of 357 ducks. From those samples, 80 Salmonella strains were isolated and 25 serovars were identified. The predominant serovars were S. Javiana, S. Derby, and S. Weltevreden. S. Javiana and S. Weltevreden were detected together in pigs, chickens, and ducks. These results indicate that the serovars of Salmonella are widely distributed in domestic animals in the Mekong Delta, Vietnam.