Sensitivity analysis using a diffuse pollution hydrologic model to assess factors affecting pesticide concentrations in river water

2010 ◽  
Vol 62 (11) ◽  
pp. 2579-2589 ◽  
Author(s):  
Koji Tani ◽  
Yoshihiko Matsui ◽  
Kentaro Narita ◽  
Koichi Ohno ◽  
Taku Matsushita
Keyword(s):  
Sensitivity Analysis ◽  
River Water ◽  
Rate Constant ◽  
Degradation Rate ◽  
Hydrologic Model ◽  
Adsorption Coefficient ◽  
Pesticide Concentration ◽  
Artificial Drainage ◽  
Degradation Rate Constant ◽  
Intermittent Irrigation

We quantitatively evaluated the factors that affect the concentrations of rice-farming pesticides (an herbicide and a fungicide) in river water by a sensitivity analysis using a diffuse pollution hydrologic model. Pesticide degradation and adsorption in paddy soil affected concentrations of the herbicide pretilachlor but did not affect concentrations of the fungicide isoprothiolane. We attributed this difference to the timing of pesticide application in relation to irrigation and drainage of the rice paddy fields. The herbicide was applied more than a month before water drainage of the fields and runoff was gradual over a long period of time, whereas the fungicide was applied shortly before drainage and runoff was rapid. However, the effects of degradability-in-water on the herbicide and fungicide concentrations were similar, with concentrations decreasing only when the rate constant of degradation in water was large. We also evaluated the effects of intermittent irrigation methods (irrigation/artificial drainage or irrigation/percolation) on pesticide concentrations in river water. The runoff of the fungicide, which is applied near or in the period of intermittent irrigation, notably decreased when the method of irrigation/artificial drainage was changed to irrigation/percolation. In a sensitivity analysis evaluating the synergy effect of degradation and adsorbability in soil, the degradation rate constant in soil greatly affected pesticide concentration when the adsorption coefficient was small but did not affect pesticide concentration when the adsorption coefficient was large. The pesticide concentration in the river water substantially decreased when either or both the degradation rate constant in soil and adsorption coefficient was large.

scholarly journals pH effect on stability and kinetics degradation of nitazoxanide in solution

2020 ◽  
Vol 4 (1) ◽  
pp. 12-17
Author(s):  
Fábio Barbosa ◽  
Leonardo Pezzi ◽  
Julia Sorrentino ◽  
Martin Steppe ◽  
Nadia Volpato ◽  
...  
Keyword(s):  
Rate Constant ◽  
Degradation Product ◽  
Degradation Rate ◽  
Degradation Kinetics ◽  
Ph Effect ◽  
Degradation Rate Constant ◽  
Main Degradation Product ◽  
Wide Ph Range ◽  
The Stability ◽  
Ph Range

Stability studies correspond to a set of tests designed to assess changes in the quality of a given drug over time and under the influence of a number of factors. Among these factors, pH plays an important role, due to the catalytic effect that hydronium and hydroxide ions can play in several reactions. In the present study, the degradation kinetics of nitazoxanide was evaluated over a wide pH range, and the main degradation product generated was identified by LC-MS/MS. Nitazoxanide showed first-order degradation kinetics in the pH range of 0.01 to 10.0 showing greater stability between pH 1.0 and 4.0. The degradation rate constant calculated for these pH was 0.0885 x 10-2 min-1 and 0.0689 x 10-2 min-1, respectively. The highest degradation rate constant value was observed at pH 10.0 (0.7418 x 10-2 min-1) followed by pH 0.01 (0.5882 x 10-2 min-1). A major degradation product (DP-1) was observed in all conditions tested. Through LC-MS/MS analysis, DP-1 was identified as a product of nitazoxanide deacetylation. The effect of pH on the stability of nitazoxanide and the kinetic data obtained contribute to a better understanding of the intrinsic stability characteristics of nitazoxanide.

Modified graphene quantum dots-zinc oxide nanocomposites for photocatalytic degradation of organic dyes and commercial herbicide

2019 ◽  
Vol 39 (3-4) ◽  
pp. 81-94 ◽  
Author(s):  
Suchada Phophayu ◽  
Pichitchai Pimpang ◽  
Sawitree Wongrerkdee ◽  
Supphadate Sujinnapram ◽  
Sutthipoj Wongrerkdee
Keyword(s):  
Quantum Dots ◽  
Photocatalytic Degradation ◽  
Rate Constant ◽  
Degradation Rate ◽  
Carrier Lifetime ◽  
Organic Dyes ◽  
Graphene Quantum Dots ◽  
High Crystallinity ◽  
Degradation Rate Constant ◽  
Photocatalytic Material

The high crystallinity of graphene quantum dots-ZnO nanocomposites is considered to have a significant effect in improving the carrier lifetime for enhanced photocatalytic degradation. The graphene quantum dots-ZnO nanocomposites were synthesized by adding graphene quantum dots solution into starting precursors during the precipitation. Characterization was performed using various techniques. High crystallinity of graphene quantum dots-ZnO nanocomposites is obtained in terms of increased crystal size and decreased dislocation density. The improved crystallinity increases the carrier lifetime on the material surface for the functional improvement of photocatalytic material. Photocatalytic test of methylene blue and methyl orange was performed under UV irradiation. Degradation rate constant reaches the maximum value for both organic dyes for the appropriate preparing condition of graphene quantum dots-ZnO nanocomposites. The graphene quantum dots-ZnO nanocomposites were then applied to degrade commercial glyphosate herbicide contaminants for an agricultural wastewater treatment investigation. The investigation aims to demonstrate a facile useful way of herbicide contaminant reduction for the better health of farmers. The graphene quantum dots-ZnO nanocomposites show an enhancement of the photocatalytic process with improved degradation rate constant (23% increased) in comparison to pure ZnO. Therefore, this work demonstrates that graphene quantum dots-ZnO nanocomposites can be used as a photocatalytic material for degrading organic dyes and commercial herbicide contaminants owing to its low-cost and environmental-friendly properties.

Intensification of a Pond System by Fibrous Carriers

1993 ◽  
Vol 28 (7) ◽  
pp. 117-123 ◽  
Author(s):  
Qi Peishi ◽  
Wang Boazhen ◽  
Ma Fang ◽  
Zhang Jinsong ◽  
Li Tingjun
Keyword(s):  
Mathematical Model ◽  
Microbial Communities ◽  
Flow Pattern ◽  
Rate Constant ◽  
Degradation Rate ◽  
Heilongjiang Province ◽  
Conventional System ◽  
Mixed Flow ◽  
Pond System ◽  
Degradation Rate Constant

A study was carried out on the intensification of a pond system, consisting of an anaerobic pond, a facultative pond and a polishing pond, in Anda City, Heilongjiang Province, by fibrous carriers packed in the anaerobic pond, by means of which the performance of the pond system was remarkably improved with higher removal capacities and efficiencies for SS, BOD5, COD, TN, TP and bacteria, compared with the conventional system. The mechanism for the intensified effect was found to be ascribed to the increase of biomass in the form of biofilm attached to the surface of the fibrous carriers and more even distribution of the biomass in the pond. A mathematical model based on the complete mixed flow pattern was developed both for the intensified and conventional anaerobic pond, and the organic degradation rate constant value K in the former was found to be much greater than that in the latter. The microbial communities in both the ponds were also observed.

Impact of transverse and longitudinal dispersion on first-order degradation rate constant estimation

2004 ◽  
Vol 73 (1-4) ◽  
pp. 3-14 ◽  
Author(s):  
Greg A. Stenback ◽  
Say Kee Ong ◽  
Shane W. Rogers ◽  
Bruce H. Kjartanson
Keyword(s):  
Rate Constant ◽  
Degradation Rate ◽  
Longitudinal Dispersion ◽  
First Order ◽  
Degradation Rate Constant

scholarly journals PENGARUH INTENSITAS CAHAYA TERHADAP DEGRADASI WARNA AGARAGAR YANG DIWARNAI SARI UMBI BIT MERAH (Beta vulgaris L. var. rubra L.)

Agric ◽  
2016 ◽  
Vol 25 (1) ◽  
pp. 42
Author(s):  
Lydia Ninan Lestario ◽  
Noviana Gunawan ◽  
Yohanes Martono
Keyword(s):  
Light Intensity ◽  
Beta Vulgaris ◽  
Rate Constant ◽  
Degradation Rate ◽  
Color Stability ◽  
Fluorescent Light ◽  
Beetroot Juice ◽  
Constant Rate ◽  
Degradation Rate Constant ◽  
Color Degradation

<p>The aims of this research were to determine the concentration of beetroot juice in jelly which panelists like best; to determine the color degradation rate constant in jelly colored with beetroot juice caused by sunlight and fluorescent light; and color degradation rate constant of jelly colored with synthetic colorant.</p><p>The organoleptic test used 2,5 percent; 5 percent; 7,5 percent; 10 percent; and 12,5 percent beetroot juice and permitted synthetic colorant for food. The light intensity to test the beetroot color stability in jelly were 879,06 lux, 1.688,54 lux, 2.342,2 lux and 6.752,2 lux.</p><p>The results showed that the concentration of beetroot juice which panelists like best was 5 percent.; The color degradation rate constant of jelly colored by 5 percent beetroot juice on intensity 879,06 lux was 0,0468 hour-1; 1.688,54 lux was 0,0565 hour-1; 2.342,2 lux was 0,0653 hour-1;<br />6.752,2 lux was 0,0887 hour-1. The higher the light intensity, the higher the degradation constant rate.</p>

Cosolvent-free nanocasting synthesis of ordered mesoporous g-C3N4 and its remarkable photocatalytic activity for methyl orange degradation

RSC Advances ◽  
2015 ◽  
Vol 5 (94) ◽  
pp. 76963-76972 ◽  
Author(s):  
Xiaochun Gao ◽  
Xuejiao Jiao ◽  
Lanchun Zhang ◽  
Wencai Zhu ◽  
Xiaohong Xu ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Methyl Orange ◽  
Rate Constant ◽  
Degradation Rate ◽  
Methyl Orange Degradation ◽  
Ordered Mesoporous ◽  
Degradation Rate Constant ◽  
Nanocasting Route

Ordered mesoporous g-C3N4, synthesized via a green cosolvent-free nanocasting route, exhibited remarkable photodegradation performance towards methyl orange with a degradation rate constant 30 times higher than that of bulk g-C3N4.

scholarly journals Controlling the Photo-Degradation Rate Constant of PS Containing Nickel(II) Complex

2019 ◽  
Vol 22 (3) ◽  
pp. 8-17
Author(s):  
Zainab Hussain ◽  
◽  
Raghda Alsayed ◽  
Atheel Alwash ◽  
Ahmed Ahmed ◽  
...  
Keyword(s):  
Rate Constant ◽  
Degradation Rate ◽  
Photo Degradation ◽  
Degradation Rate Constant

scholarly journals Photostability Study of Some Modified Poly(vinyl chloride) Containing Pendant Schiff’s Bases

2016 ◽  
Vol 13 (2) ◽  
pp. 188-195
Author(s):  
Baghdad Science Journal
Keyword(s):  
Vinyl Chloride ◽  
Rate Constant ◽  
Degradation Rate ◽  
Schiff’S Bases ◽  
Photo Degradation ◽  
Photo Oxidation ◽  
Modified Polymers ◽  
Poly Vinyl Chloride ◽  
Schiff's Bases ◽  
Degradation Rate Constant

The polymers modified Poly(vinyl chloride) differ in their tendency to photo oxidation comparing with that unmodified. It has been studied Photostability for modified Poly(vinyl chloride) chains using Schiff’s bases derivative of (5-amino-1, 3, 4-thiadiazole-2-thiol) in a manner casting of plastic chips with thickness (40) in a solvent Tetrahydrofuran. It has been determined the effectiveness Photostability of these modified polymers through the photo degradation rate constant for photostabilizer (kd) for the modified Poly (vinyl chloride). Attributed efficiency of these Poly(vinyl chloride) chips in Photostability by replace the atom Cl Poly(vinyl chloride) chains ends more stable than light stabilizer.

scholarly journals Enhanced photocatalytic degradation of N-doped TiO2-SiO2 composite for degradation of phenol under simulated natural light assisted by S2O8 2- anions

2021 ◽  
Vol 947 (1) ◽  
pp. 012020
Author(s):  
Huu-Tai Huynh ◽  
Minh-Vien Le ◽  
Luan Van Hoang
Keyword(s):  
Photocatalytic Degradation ◽  
Band Gap ◽  
Rate Constant ◽  
Degradation Rate ◽  
Band Gap Energy ◽  
Natural Light ◽  
Doped Tio2 ◽  
Gap Energy ◽  
Molar Ratios ◽  
Degradation Rate Constant

Abstract In recent years, TiO2 photocatalyst has been studied to increase the overall efficiency in the degradation of organic pollutants in water. Several solutions have been proposed such as non-metal doping to reduce a high band gap energy (3.2 eV) of TiO2 to increase absorption in the visible region and synthesis of composite photocatalyst to improve the efficiency of electron-hole separation and the specific surface area. Herein, the N-doped TiO2-SiO2 photocatalysts were investigated. Powder samples with three molar ratios of TiO2/SiO2 (95/5-TS5, 85/15-TS15, 75/25-TS25) were successfully synthesized, characterized, and estimated their photocatalytic activity toward the phenol degradation (initial concentration to be 10 ppm) under simulated natural light. N-doped TiO2-SiO2 samples were prepared with molar ratios of N to designed TiO2 to be 3%, 5%, 7%. The 3N-TS5 photocatalyst (3 mol % N doped TS5) shows the highest phenol efficiency degradation, to be 95% in 4 h, photocatalytic degradation rate constant of 1.02}10−2 min−1 due to its narrower band gap energy (3.05 eV). Furthermore, the addition of S2O8 2- anions at a concentration of 1 mM is enhanced degradation efficiency and degradation rate. And phenol is almost completely degraded within 60 min and achieved a degradation rate constant of 7.65*10−2 min−1, 7.5 times higher than that without the presence of S2O8 2- anions. This attractive result is attributed to the generation of sulfate radical (SO4 *“) during photolysis. Finally, N-doped TiO2-SiO2 photocatalyst assisted by S2O8 2- anions shows potential to design and improve manufacturing processes to obtain photoreactors for organic degradation from waste-water under natural light degradation.

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