scholarly journals Carbaryl Photochemical Degradation on Soil Model Surfaces

Soil Systems ◽  
2019 ◽  
Vol 3 (1) ◽  
pp. 17 ◽  
Author(s):  
Marie Siampiringue ◽  
Rajae Chahboune ◽  
Pascal Wong-Wah-Chung ◽  
Mohamed Sarakha
Keyword(s):  
Liquid Chromatography ◽  
Light Exposure ◽  
Degradation Mechanism ◽  
Parent Compound ◽  
Toxicity Tests ◽  
Photochemical Degradation ◽  
First Order Kinetics ◽  
A Value ◽  
Order Of Magnitude ◽  
Set Up

The phototransformation of carbaryl was investigated upon solar light exposure on three surfaces, silica, kaolin and sand, as soil models. By excitation with a Suntest set up at the surface of the three solid supports, the degradation of carbaryl followed first-order kinetics with a rate constant of 0.10 h−1. By using the Kubelka Munk model, the quantum yield disappearance at the surface of kaolin was evaluated to 2.4 × 10−3. Such a value is roughly one order of magnitude higher than that obtained in aqueous solutions. The results indicated that the particle size and the specific surface area of the various models have significant effects. The photo-oxidative properties as well as the byproduct elucidation by liquid chromatography combined with diode arrays (LC-DAD) and liquid chromatography coupled mass spectrometry (LC-MS) analyses allowed us to propose the degradation mechanism pathways. The main products were 1-naphtol and 2-hydroxy-1,4-naphthoquinone, which arise from a photo-oxidation process together with products from photo-Fries, photo-ejection and methyl carbamate hydrolysis. The toxicity tests clearly showed a significant decrease of the toxicity in the early stages of the irradiation. This clearly shows that the generated products are less toxic than the parent compound.

Decomposition of 4,4'-(Diazoamino)-bis(5-methoxy-2-methylbenezenesulfonic Acid) in Solutions ofFD&C Red No. 40

1984 ◽  
Vol 67 (4) ◽  
pp. 844-845
Author(s):  
Naomi Richfield-Fratz
Keyword(s):  
Liquid Chromatography ◽  
Aqueous Solutions ◽  
Borate Buffer ◽  
Sodium Borate ◽  
First Order ◽  
First Order Kinetics ◽  
Color Additive ◽  
Sodium Borate Buffer

Abstract 4,4'-(Diazoamino)-bis(5-methoxy-2-methylbenzenesuIfonic acid), when present as a reaction by-product in FD&C Red No. 40, is shown to decompose rapidly in aqueous solutions of the color additive. The decomposition is halted by the addition of sodium borate buffer. Quantitationly liquid chromatography shows that decomposition is nonlinear with time and follows approximate first order kinetics.

scholarly journals The Response to Stratospheric Forcing and Its Dependence on the State of the Troposphere

2009 ◽  
Vol 66 (7) ◽  
pp. 2107-2115 ◽  
Author(s):  
Cegeon J. Chan ◽  
R. Alan Plumb
Keyword(s):  
Time Scale ◽  
Equilibrium Temperature ◽  
Intrinsic Variability ◽  
Winter Solstice ◽  
Fluctuation Dissipation ◽  
Fluctuation Dissipation Theorem ◽  
Order Of Magnitude ◽  
Leading Mode ◽  
Set Up ◽  
Hemisphere Winter

Abstract In simple GCMs, the time scale associated with the persistence of one particular phase of the model’s leading mode of variability can often be unrealistically large. In a particularly extreme example, the time scale in the Polvani–Kushner model is about an order of magnitude larger than the observed atmosphere. From the fluctuation–dissipation theorem, one implication of these simple models is that responses are exaggerated, since such setups are overly sensitive to any external forcing. Although the model’s equilibrium temperature is set up to represent perpetual Southern Hemisphere winter solstice, it is found that the tropospheric eddy-driven jet has a preference for two distinct regions: the subtropics and midlatitudes. Because of this bimodality, the jet persists in one region for thousands of days before “switching” to another. As a result, the time scale associated with the intrinsic variability is unrealistic. In this paper, the authors systematically vary the model’s tropospheric equilibrium temperature profile, one configuration being identical to that of Polvani and Kushner. Modest changes to the tropospheric state to either side of the parameter space removed the bimodality in the zonal-mean zonal jet’s spatial distribution and significantly reduced the time scale associated with the model’s internal mode. Consequently, the tropospheric response to the same stratospheric forcing is significantly weaker than in the Polvani and Kushner case.

Berechnung kinetischer Isotopeneffekte für die Reaktion von Methyljodid mit Cyanid-Ion

1966 ◽  
Vol 21 (9) ◽  
pp. 1377-1384
Author(s):  
A. V. Willi
Keyword(s):  
Transition State ◽  
Secular Equation ◽  
Isotope Effects ◽  
Force Constants ◽  
Bond Breaking ◽  
Bending Force ◽  
A Value ◽  
Order Of Magnitude ◽  
Deuterium Isotope Effects ◽  
The Difference

Kinetic carbon-13 and deuterium isotope effects are calculated for the SN2 reaction of CH3I with CN-. The normal vibrational frequencies of CH3I, the transition state I · · · CH3 · · · CN, and the corresponding isotope substituted reactants and transition states are evaluated from the force constants by solving the secular equation on an IBM 7094 computer.Values for 7 force constants of the planar CH3 moiety in the transition state (with an sp2 C atom) are obtained by comparison with suitable stable molecules. The stretching force constants related to the bonds being broken or newly formed (fCC, fCC and the interaction between these two stretches, /12) are chosen in such a way that either a zero or imaginary value for νʟ≠ will result. Agreement between calculated and experimental methyl-C13 isotope effects (k12/ k13) can be obtained only in sample calculations with sufficiently large values of f12 which lead to imaginary νʟ≠ values. Furthermore, the difference between fCI and fCC must be small (in the order of 1 mdyn/Å). The bending force constants, fHCI and fHCC, exert relatively little influence on k12/k13. They are important for the D isotope effect, however. As soon as experimental data on kH/kD are available it will be possible to derive a value for fHCC in the transition state if fHCI is kept constant at 0.205 mdynA, and if fCI, fCC and f12 are held in a reasonable order of magnitude. There is no agreement between experimental and calculated cyanide-C13 isotope effects. Possible explanations are discussed. — Since fCI and fCC cannot differ much it must be concluded that the transition state is relatively “symmetric”, with approximately equal amounts of bond making and bond breaking.

Increased Wall-to-Wall Curing Contraction in Thin Bonded Resin Layers

1989 ◽  
Vol 68 (1) ◽  
pp. 48-50 ◽  
Author(s):  
A.J. Feilzer ◽  
A.J. De Gee ◽  
C.L. Davidson
Keyword(s):  
Polymerization Shrinkage ◽  
A Value ◽  
Set Up

Wall-to-wall (WTW) polymerization contraction of filled and unfilled chemically and photo-initiated resins was studied in relation to the WTW distance. In an experimental set-up, the resins were bonded to two opposing disks, and the axial (WTW) displacement resulting from the polymerization shrinkage was measured continuously. It was found that the WTW contraction increased with decreasing WTW distance and ultimately reached a value of almost three times the linear polymerization shrinkage.

scholarly journals Investigation of the β-pinene photooxidation by OH in the atmosphere simulation chamber SAPHIR

2016 ◽  
Author(s):  
Martin Kaminski ◽  
Hendrik Fuchs ◽  
Ismail-Hakki Acir ◽  
Birger Bohn ◽  
Theo Brauers ◽  
...  
Keyword(s):  
Degradation Mechanism ◽  
Degradation Process ◽  
Product Distribution ◽  
High Reactivity ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Emission Rates ◽  
Photochemical Degradation ◽  
Atmosphere Simulation Chamber ◽  
Simulation Chamber

Abstract. Beside isoprene, monoterpenes are the non-methane volatile organic compounds (VOC) with the highest global emission rates. Due to their high reactivity towards OH, monoterpenes can dominate the radical chemistry of the atmosphere in forested areas. In the present study the photochemical degradation mechanism of β-pinene was investigated in the Jülich atmosphere simulation chamber SAPHIR. The focus of this study is on the OH budget in the degradation process. Therefore the SAPHIR chamber was equipped with instrumentation to measure radicals (OH, HO2, RO2), the total OH reactivity, important OH precursors (O3, HONO, HCHO), the parent VOC beta-pinene, its main oxidation products, acetone and nopinone, and photolysis frequencies. All experiments were carried out under low NOx conditions (≤ 2 ppb) and at atmospheric beta-pinene concentrations (≤ 5 ppb) with and without addition of ozone. For the investigation of the OH budget, the OH production and destruction rates were calculated from measured quantities. Within the limits of accuracy of the instruments, the OH budget was balanced in all β-pinene oxidation experiments. However, even though the OH budget was closed, simulation results from the Master Chemical Mechanism 3.2 showed that the OH production and destruction rates were underestimated by the model. The measured OH and HO2 concentrations were underestimated by up to a factor of two whereas the total OH reactivity was slightly overestimated because of the poor reproduction of the measured nopinone by the model by up to a factor of three. A new, theory-derived first-generation product distribution by Vereecken and Peeters was able to reproduce the measured nopinone time series and the total OH reactivity. Nevertheless the measured OH and HO2 concentrations remained underestimated by the numerical simulations. These observations together with the fact that the measured OH budget was closed suggest the existence of unaccounted sources of HO2.

scholarly journals Toxicity of neem's oil, a potential biocide against the invasive mussel Limnoperna fortunei (Dunker 1857)

2012 ◽  
Vol 84 (4) ◽  
pp. 1065-1071 ◽  
Author(s):  
Patricio J. Pereyra ◽  
Gustavo B. Rossini ◽  
Gustavo Darrigran
Keyword(s):  
Invasive Species ◽  
Toxicity Tests ◽  
Limnoperna Fortunei ◽  
Target Species ◽  
Potential Toxicity ◽  
A Value ◽  
Closed Systems ◽  
The One ◽  
Invasive Mussel ◽  
Golden Mussel

The golden mussel Limnoperna fortunei (Dunker 1857) is one of the most distributed Nuisance Invasive Species (NIS) in South America, and a threat of great concern for the industry of the area. In this study, we carried out toxicity tests made with a Neem's oil solution with L. fortunei larvae and benthonic adults (7, 13 and 19 ± 1 mm). Tests with non-target species (Daphnia magna, Lactuca sativa and Cnesterodon decemmculatus) were also made with the aim to evaluate the potential toxicity of the Neem's solution in the environment. The LC100 of Neem's solution obtained for larvae was 500 µl/L, a value much higher than the one obtained for D. magna and C. decemmaculatus. Thus, we recommend that it should not be used in open waters. However, since the adults were killed in 72 h and the larvae in 24 h, this product can be used in closed systems, in man-made facilities.

scholarly journals Weekly water-loss from Spherical Water-loss Integrators on a Clearing and below Secondary Growth in Central Amazonia ()

1972 ◽  
Vol 2 (1) ◽  
pp. 33-36 ◽  
Author(s):  
W. L. F. Brinkmann
Keyword(s):  
Solar Radiation ◽  
Water Loss ◽  
Standing Crop ◽  
Secondary Growth ◽  
Tropical Agriculture ◽  
Air Humidity ◽  
Central Amazonia ◽  
Order Of Magnitude ◽  
Set Up ◽  
The Impact

Abstract: Spherical ceramic bulbs were set up as weekly water-loss integrators on a clearing and below a 2 year-old Cecropia-commumty at Km 18 of the Manaus-Itacoatiara Road. The instruments worked well in distinguishing the particular responses of individual sites to the impact of atmospheric agents as solar radiation, air temperature, air humidity and wind. Water-loss was primarily dependent on the order of magnitude of the weekly total of solar radiation and the presence or lack of a standing crop. Already a scarce secondary growth will reduce the weekly amount of water lost to the atmosphere considerably. Shelter-wood, however, considering the crop specific demands if introduced to tropical agriculture would provide favourable conditions as far as the impact of atmospheric controls on the tropical environment are concerned.

Determination of cannabinoids in oral fluid and urine of “light cannabis” consumers: a pilot study

2018 ◽  
Vol 57 (2) ◽  
pp. 238-243 ◽  
Author(s):  
Roberta Pacifici ◽  
Simona Pichini ◽  
Manuela Pellegrini ◽  
Roberta Tittarelli ◽  
Flaminia Pantano ◽  
...  
Keyword(s):  
Pilot Study ◽  
Oral Fluid ◽  
Urine Samples ◽  
Screening Tests ◽  
Gas Chromatography Mass Spectrometry ◽  
Negative Results ◽  
A Value ◽  
Order Of Magnitude ◽  
Confirmation Analysis

Abstract Background In those countries where cannabis use is still illegal, some manufacturers started producing and selling “light cannabis”: dried flowering tops containing the psychoactive principle Δ-9-tetrahydrocannabinol (THC) at concentrations lower than 0.2% together with variable concentration of cannabidiol (CBD). We here report a pilot study on the determination of cannabinoids in the oral fluid and urine of six individuals after smoking 1 g of “light cannabis”. Methods On site screening for oral fluid samples was performed, as a laboratory immunoassay test for urine samples. A validated gas chromatography-mass spectrometry (GC-MS) method was then applied to quantify THC and CBD, independently from results of screening tests. Results On site screening for oral fluid samples, with a THC cut-off of 25 ng/mL gave negative results for all the individuals at different times after smoking. Similarly, negative results for urine samples screening from all the individuals were obtained. Confirmation analyses showed that oral fluid THC was in the concentration range from 2.5 to 21.5 ng/mL in the first 30 min after smoking and then values slowly decreased. CBD values were usually one order of magnitude higher than those of THC. THC-COOH, the principal urinary THC metabolite, presented the maximum urinary value of 1.8 ng/mL, while urinary CBD had a value of 15.1 ng/mL. Conclusions Consumers of a single 1 g dose of “light cannabis” did not result as positive in urine screening, assessing recent consumption, so that confirmation would not be required. Conversely, they might result as positive to oral fluid testing with some on-site kits, with THC cut-off lower than 25 ng/mL, at least in the first hour after smoking and hence confirmation analysis can be then required. No conclusions can be drawn of eventual chronic users.

scholarly journals Mapping gaseous amines, ammonia, and their particulate counterparts in marine atmospheres of China’s marginal seas: Part 1 – Differentiating marine emission from continental transport

2021 ◽  
Author(s):  
Dihui Chen ◽  
Yanjie Shen ◽  
Juntao Wang ◽  
Yang Gao ◽  
Huiwang Gao ◽  
...  
Keyword(s):  
Significant Negative Correlation ◽  
The Yellow Sea ◽  
Sea Spray ◽  
Marine Atmosphere ◽  
Coastal Site ◽  
Marginal Seas ◽  
Range Transport ◽  
Order Of Magnitude ◽  
Using Data ◽  
Set Up

Abstract. To study sea-derived gaseous amines, ammonia, and primary particulate aminium ions in the marine atmospheres of China's marginal seas, an onboard URG-9000D Ambient Ion Monitor-Ion chromatography (AIM-IC, Thermo Fisher) was set up on the front deck of the R/V Dongfanghong 3 to semi-continuously measure the spatiotemporal variations in the concentrations of atmospheric trimethylamine (TMAgas), dimethylamine (DMAgas), and ammonia (NH3gas) along with their particulate matter (PM2.5) counterparts. In this study, we differentiated marine emissions of the gas species originating from continental transport using data obtained from December 9 to 22, 2019 during the cruise over the Yellow and Bohai Seas, facilitated by additional measurements collected at a coastal site near the Yellow Sea during summer 2019. The data obtained during the cruise and the coastal site demonstrated that the observed TMAgas and protonated trimethylamine (TMAH+) in PM2.5 over the Yellow and Bohai Seas overwhelmingly originated from marine sources. During the cruise, there was no significant correlation (P > 0.05) between the simultaneously measured TMAH+ and TMAgas concentrations. Additionally, the concentrations of TMAH+ in the marine atmosphere varied around 0.28 ± 0.18 μg m−3 (average  ±  standard deviation), with several episodic hourly average values exceeding 1 μg m−3, which were approximately one order of magnitude larger than those of TMAgas (approximately 0.031 ± 0.009 μg m−3). Moreover, there was a significant negative correlation (P < 0.01) between the concentrations of TMAH+ and NH4+ in PM2.5 during the cruise. Therefore, the observed TMAH+ in PM2.5 was overwhelmingly derived from primary sea-spray aerosols. Using the TMAgas and TMAH+ in PM2.5 as tracers for sea-derived basic gases and sea-spray particulate aminium ions, the values of non-sea-derived DMAgas and NH3gas, as well as non-sea-spray particulate DMAH+ in PM2.5, were estimated, and the estimated average values of each species contributed to 16 %, 34 %, and 65 % of the observed average concentrations, respectively. Uncertainties remained in the estimations as TMAH+ may decompose into smaller molecules in seawater to varying extents. The non-sea-derived gases and non-sea-spray particulate DMAH+ likely originated from long-range transport from the upwind continents, according to the recorded offshore winds and increased concentrations of SO42− and NH4+ in PM2.5. The lack of a detectable increase in the particulate DMAH+, NH4+, and SO42− concentrations in several SO2 plumes did not support the secondary formation of particulate DMAH+ in the marine atmosphere.

scholarly journals Kinetics, Mechanism, and Toxicity of Amlodipine Degradation by the UV/Chlorine Process

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3150
Author(s):  
Jianye Xu ◽  
Siqi Zhou ◽  
Erdeng Du ◽  
Yongjun Sha ◽  
Lu Zheng ◽  
...  
Keyword(s):  
Acute Toxicity ◽  
Advanced Oxidation Process ◽  
High Resolution Mass Spectrometry ◽  
Ph Value ◽  
Degradation Products ◽  
Degradation Mechanism ◽  
Complete Removal ◽  
Ammonia Concentration ◽  
Ammonia Nitrogen ◽  
Toxicity Tests

The UV/chlorine process, as a new type of AOP (Advanced Oxidation Process), was utilized to treat amlodipine (AML)-containing water. The influencing factors, including chlorine dose, UV intensity, solution initial pH value, and ammonia concentration, were investigated. The degradation of AML in real water and the relative contributions of OH• and Cl• were also studied. Finally, high-resolution mass spectrometry (HRMS) and GC-MS were used to identify the possible degradation products. The results demonstrated that the AML degradation process was fitted with apparent first-order kinetics. AML degradation had a positive correlation with UV intensity and chlorine dose, and a negative correlation with ammonia concentration. In the presence of ammonia nitrogen and DOM, the removal of AML from real water was reduced. OH• made a dominant percentage contribution of 55.7% to the degradation of AML. Sixteen intermediates were detected and identified. A possible degradation mechanism was also proposed. Acute toxicity tests and risk prediction both illustrated that the complete removal of AML does not guarantee the reduction of acute toxicity, but a prolonged degradation promoted the detoxification of toxic intermediates. The UV/chlorine process can be regarded to be an effective method to remove AML and reduce ecological risk.

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