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51.
Dao TH 《Journal of environmental quality》2003,32(2):694-701
Information is needed on organic polyphosphates such as myo-inositol 1,2,3,5/4,6-hexakis dihydrogenphosphate or phytate (IP6) contribution to the sources and sinks of dissolved phosphorus (PO4-P) in the soil-manure-water system. Effects of Na+, Ca2+, Al3+, and Fe3+ and cation to IP6-P mole ratios on the enzymatic dephosphorylation of IP6 were studied to determine controlling mechanisms of dephosphorylation and persistence in manure. Phytate- and PO4-P were analyzed by high-performance liquid chromatography. Phytate dephosphorylation by Aspergillus ficuum (Reichardt) Henn. phytase EC 3.1.3.8 decreases by 50 +/- 3.6 and 40 +/- 4% at pH 4.5 and 6, respectively, as Ca2+ concentrations increase and cation to IP6-P mole ratios reach 6:6. Polyanionic IP6 has a high affinity for Al3+ and Fe3+ and reductions in dephosphorylation average 27 and 32% at a cation to IP6-P mole ratio of 1:6 for Al3+ and Fe3+, respectively, while reaching more than 99% at a mole ratio of 6:6. A phytase-hydrolyzable phosphorus (PHP) fraction is native to ruminant animal manure and is proportional to total solids (TS) concentration in 1 to 100 g L(-1) suspensions. Added phytase, in effect, increases water-extractable P content of manure and the risk of environmental P dispersion. As the bioavailability and ecological effect of IP6-P appear to be regulated not only by pH-controlled enzyme activity but also by the associated counterions, the differential protective effects of cations influence the accuracy of manure PHP fraction estimates and increase phytate resistance to enzymatic dephosphorylation that may lead to its persistence in manure. 相似文献
52.
Nguyen Le-Phuc Thuy Ngoc Luong Tri Van Tran Yen Thi Hai Pham Phuong Thuy Ngo Sura Nguyen 《Journal of Material Cycles and Waste Management》2017,19(3):1085-1092
In this study, a very promising way of treating and recycling spent nickel catalysts of fertilizer plants in Vietnam was proposed. Firstly, nickel was recovered from spent catalyst using HNO3—leaching process. Results show that nickel recovery of over 90% with a purity of over 90% can be achieved with HNO3 2.1–2.5 M at 100?°C in 75 min. The residue after leaching is not considered as a hazardous waste according to the Vietnamese regulations. Then, the leachate solution was used as a precursor to prepare a model catalyst for exhaust gas (CO, HC, NOx) treatment. In comparison with the catalyst prepared from the commercial nickel nitrate solution, the catalyst synthesized from recovered nickel exhibits similar properties and activities. The influence of Ni loading of Ni/alumina catalyst as well as the modification of active phase by some metals addition (Mn, Ba, Ce) was also investigated. It is feasible to modify active phase by transition metals such as Mn, Ba, and Ce for complete oxidation of CO and HC at 270?°C and a reduction of NOx below 350?°C at high volumetric flow condition (GHSV?=?110.000 h?1). 相似文献
53.
Extracellular phosphohydrolases mediate the dephosphorylation of phosphoesters and influence bioavailability and loss of agricultural P to the environment to pose risks of impairment of sensitive aquatic ecosystems. Induction and culture of five strains of Aspergillus were conducted to develop a source of high-affinity and robust phosphohydrolases for detecting environmental P and quantifying bioactive P pools in heterogeneous environmental specimens. Enzyme stability and activity against organic P in poultry litter were evaluated in 71 samples collected across poultry producing regions of Arkansas, Maryland, and Oklahoma of the US Differences existed in strains' adaptability to fermentation medium as they showed a wide range of phytate-degrading activity. Phosphohydrolases from Aspergillus ficuum had highest activity when the strain was cultured on a primarily chemical medium, compared to Aspergillus oryzae which preferred a wheat bran-based organic medium. Kinetics parameters of A. ficuum enzymes (K(m)=210 microM; V(max) of 407 nmol s(-1)) indicated phytic acid-degrading potential equivalent to that of commercial preparations. Purified A. ficuum phosphohydrolases effectively quantified litter bioactive P pools, showing that organic P occurred at an average of 54 (+/-14)% of total P, compared to inorganic phosphates, which averaged 41 (+/-12)%. Litter management and land application options must consider the high water-extractable and organic P concentrations and the biological availability of the organic enzyme-labile P pool. Robustness of A. ficuum enzymes and simplicity of the in situ ligand-based enzyme assay may thus increase routine assessment of litter bioactive P composition to sense for on-farm accumulation of such environmentally-sensitive P forms. 相似文献
54.
55.
舟山群岛港口发展有广阔前景 总被引:2,自引:1,他引:1
舟山海域位于长江水道和我国南北洋通道交汇的前沿,是我国南北海运的要冲与江海联运的枢纽,地理位置非常优越。舟山的三大优势资源“鱼、港、景”中,港的优势得天独厚拥有极为丰富的深水岩线,建设第四、五代大型集装箱泊位及其他大型深水泊位,发展潜能很大。舟山港域的发展提出了三点建议:1、充分利用区域优势,北依上海,南托宁波,定位于华东沿海重要的区域性洪口,成为长江三角洲口群体中的一个重要组成部分。2、利用岛屿 相似文献
56.
Maternal serum markers for trisomy 21 screening (MSS) can be assayed in women ≥35 years in an attempt to reduce the need for invasive procedures and thereby avoid their side effects. Our objective was to compare, in women ≥35, eight different software packages dedicated to second trimester MSS, thus providing reliable data for patient counselling. A simulation study was carried out on 189 sera from women with Down syndrome fetuses and 11 962 sera from mothers of unaffected babies. The first step was to estimate the joint distribution of alpha-fetoprotein (AFP) and free beta-human chorionic gonadotrophin (β-hCG). The second step was to calculate trisomy 21 detection and false-positive rates for each software according to maternal age (35–45 years), using the usual 1:250 risk threshold. Agreement between software packages was measured using 2×2 kappa coefficients. Detection rates and false-positive rates increased with maternal age. Depending on the software, 57–71% detection rates were achieved at 35 years with 12–18% false-positive rates. At 45 years, 61–100% detection rates were achieved with 66–95% false-positive rates. Up to 39 years, all softwares were concordant (kappa coefficients >0.75). In the range 35–45 years, false-positive and detection rates increased substantially with maternal age and differences between software packages are observed. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
57.
Ngo Thanh Huy Van Dieu-Anh Tran Hoai Le Nakada Norihide Tanaka Hiroaki Huynh Trung Hai 《Environmental science and pollution research international》2021,28(10):12082-12091
Environmental Science and Pollution Research - This study evaluated the occurrence of PPCPs in Cau River (Vietnam). Surface water and sediment samples were collected to determine PPCP... 相似文献
58.
The effects of powdered activated carbon(PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor(DMBR) were investigated to explore the enhancement mechanism of pollutants removal and filtration performance. Sludge properties were analyzed through various analytical measurements. The results showed that the improved sludge aggregation ability and the evolution of microbial communities affected sludge morphology in PAC-DMBR, as evidenced by the formation of large, regularly shaped and strengthened sludge flocs. The modifications of sludge characteristics promoted the formation process and filtration flux of the dynamic membrane(DM) layer. Additionally, PAC addition did not exert very significant influence on the propagation of eukaryotes(protists and metazoans)and microbial metabolic activity. High-throughput pyrosequencing results indicated that adding PAC improved the bacterial diversity in activated sludge, as PAC addition brought about additional microenvironment in the form of biological PAC(BPAC), which promoted the enrichment of Acinetobacter(13.9%), Comamonas(2.9%), Flavobacterium(0.31%) and Pseudomonas(0.62%), all contributing to sludge flocs formation and several(such as Acinetobacter) capable of biodegrading relatively complex organics. Therefore, PAC addition could favorably modify sludge properties from various aspects and thus enhance the DMBR performance. 相似文献
59.
Long Ngo Louise M. Ryan Maura Mezzetti Frédéric Y. Bois Thomas J. Smith 《Environmental and Ecological Statistics》2011,18(1):131-146
In a study of 133 volunteer subjects, demographic, physiologic and pharmacokinetic data through exposure to 1,3-Butadiene
(BD) were collected in order to estimate the percentage of BD concentration metabolized at steady state, and to determine
whether this percentage varies across gender, racial, and age groups. During the 20 min of continuous exposure to 2 parts
per million (ppm) of BD, five measurements of exhaled concentration were made on each subject. In the following 40 min washout
period, another five measurements were collected. A Bayesian hierarchical compartmental physiologically-based pharmacokinetic
model (PKPB) was used. Using prior information on the model parameters, Markov Chain Monte Carlo (MCMC) simulation was conducted
to obtain posterior distributions. The overall estimate of the mean percent of BD metabolized at steady state was 12.7% (95%
credible interval: 7.7–17.8%). There was no significant difference in gender with males having a mean of 13.5%, and females
12.3%. Among the racial groups, Hispanic (13.9%), White (13.0%), Asian (12.1%), and Black (10.9%), the significant difference
came from the difference between Black and Hispanic with a 95% credible interval from −5.63 to −0.30%. Those older than 30 years
had a mean of 12.2% versus 12.9% for the younger group; although this was not a statistically significant difference. Given
a constant inhalation input of 2 ppm, at steady state, the overall mean exhaled concentration was estimated to be 1.75ppm
(95% credible interval: 1.64–1.84). An equivalent parameter, first-order metabolic rate constant, was also estimated and found
to be consistent with the percent of BD metabolized at steady state across gender, race, and age strata. 相似文献
60.
Ngo An The Nguyen Giang Thi Huong Nong Duong Huu See Linda 《Environmental science and pollution research international》2022,29(28):42037-42054
Environmental Science and Pollution Research - This research developed an agent-based model (ABM) for simulating pollutant loads from pig farming. The behavior of farmer agents was captured using... 相似文献