Ozone decomposition under the irradiation of 253.7 nm in the presence of methyl bromide

In this paper the mechanism and kinetic of ozone decomposition under the irradiation of 253.7 nm UV\|light were studied. The quantum yield of the ozone depletion in the presence of methyl bromide is further determined and a reaction model is provided to explain the experimental fact.

Grafting,metham sodium,soil solarization and virtually impermeable films as alternative technologies to methyl bromide for Chinese protected tomatoes

In the frame of the Sino-ltalian Cooperation Program for Environmental Protection, jointly launched in the year 2000 by the Italian Ministry for Environment and Territory and Sea （IMETS） and the China State Environmental Protection Administration （SEPA）, experimental trials were carried out in Qingzhou city （Shandong Province, China） during 2001-2003 to test several methyl bromide alternative methods to control soilborne diseases in greenhouse tomatoes. Grafting tomatoes on resistant rootstock （Lyeopersicon lycopersicum × L. hirsutum）, metham sodium applied under traditional polyethylene plastic films; metham sodium applied at low rate under virtually impermeable films and soil sotarization combined with biocontrol agents were the alternatives tested and compared to methyl bromide applied under virtually impermeable plastic films too. Collected data show that resistant rootstock （Lycopersicon tycopersicum × L. hirsutum） introduced from Italy is a promising alternative to methyl bromide for local tomato cultivars. Metham sodium applied under traditional polyethylene plastic films is an effective alternative. Moreovez virtually impermeable films demonstrate the help to reduce methyl bromide and metham sodium rates. Finally soil solarization combined with biocontrol agents does not provide satisfactory results in terms of disease control.

THEORETICAL INVESTIGATION OF COLLISION ENERGY EFFECT ON REACTION O(?) BARIUM WITH METHYL BROMIDE

The reac dynamics on Ba+BrCH_3→BaBr+CH_3 has been investigated in the first proposed potential energy surface of the generalized LEPS type,using the quasiclassical trajectory method.In simulation of the conditions in molecular beam experiments,the results of the present study show significant effect of the reagent collision energy on the dynamics of the reaction,and are in good agreement with the experimental ones.

Study on the effect of methyl bromide and metham sodium fumigation on the soil protozoan community in a greenhouse environment

We examined soil fumigation effects on soil protozoan abundance and community structure in greenhouses and explored the capacity of protozoa to recover after disturbances. A randomized complete block design with five treatments and 4 replicates was set up in Qingzhou, Shandong Province, China. In addition to methyl bromide （MB） and untreated control （CK）, three alternative fumigation treatments were studied, including MB＋VIF （virtually impermeable films）, metham sodium （MS） and MS＋VIF. Tomato cultivars （Lyeopersicum eseulentum Mill）, cv. Maofen-802 were selected as test crops. Results of four fumigations were demonstrated through three-level ten-fold dilution methodology. Abundance of three groups of soil protozoa-flagellates, amoebae, and ciliates was measured from July 2002 to July 2003. Results indicated that two chemical fumigants and their combinations with physical material all significantly repressed soil protozoan abundance. MB was a stronger fumigant than MS, and use of VIF increased their repressive power. The most serious population reduction occurred in amoebae, thus, they also required the longest time to recover. MB and MS also changed the protozoan community structure. MB use decreased the percentage of amoebae but increased percentage of ciliates, while MS incrcased the percentagc of amoebae and decreased the percentage of flagellates in the protozoan community.

Synthesis of dimethyl ether from methane mediated by HBr

Dimethyl ether （DME） was synthesized from methane through a two-step process, in which CH3Br was prepared from the oxidative bromination reaction of methane in the presence of HBr and oxygen over a Rh-SiO2 catalyst and then, in the second step, CH3Br was hydrolyzed to DME over a silica supported metal chloride catalyst. 12 mol%ZnCl2/SiO2 catalyst was found to be the most active, but it deactivated because of Cl- losing.

Impact of Soil Texture and Organic Matter Content on Methyl Isothiocyanate Volatilization from Soil Columns

Metam sodium （MS; sodium N-methyl dithiocarbamate） has emerged as a promising soil fumigant in the US to replace methyl bromide （MeBr）. Metam potassium （MK; potassium N-methyl dithiocarbamate） and MS break down into the volatile gas methyl isothiocyanate （MITC） to control soil borne pests. Many studies have focused on MS, but MK has not been studied as thoroughly. The objective of this research was to determine the effect of increasing organic matter （OM） treatments and soil texture to minimize the off-gassing of MS and MK. Bench-scale soil column studies were performed to simulate organic matter treatments that may decrease the volatilization loss of MITC. Incorporation depth of OM simulated surface tillage （0-15 cm） practices. Soil was packed in steel columns and MS or MK was applied at a depth of 15 cm and MITC volatilization was measured using gas chromatography/mass spectroscopy. Volatilization of MITC behaved similarly for MS and MK with MITC movement impacted by soil texture. MITC volatilization was lower from a sandy clay loam than a sandy soil. Surface incorporation of OM did not significantly decrease MITC volatilization. These results suggest that soil texture is the dominant factor reducing MITC off-gassing and prolonging the time needed to control soil borne pests.

Impact of Soil Fumigation Practices on Soil Nematodes and Microbial Biomass

This study was designed to understand the impact of methyl bromide (MB) (CH3Br) and its alternatives on both free-living and root-knot nematodes in the soil. A randomized complete block experiment with six treatments and 4 replicates (each replicate in a separate greenhouse) was established in Qingzhou, Shandong Province, China. In addition to MB and untreated control (CK) treatments there were four alternative soil fumigation practices including MB+virtually impermeable films (VIF), metam sodium (MS), MS +VIF and soil solarization combined with selected biological control agents (SS+BCA). Two tomato (Lycopersicum esculentum Mill.) cultivars, cv. Maofen-802 from the Xian Institute of Vegetable Science, China, and cv. AF179 Brillante from the Israeli Hazera Quality Seeds, were selected as test crops. The results indicated that Rhabditidae was the most dominant population with percentage abundance as high as 85% of the total number of identified free-living nematodes, followed by that of Cephalobidae. Methyl bromide and its alternatives except for the non-chemical SS+BCA treatment controlled the target pest, root-knot nematodes. Also, the impact of the three chemical alternatives on free-living nematode number and functional group abundance was similar to the impact associated with a typical methyl bromide application. Chemical fumigation practices, especially that with MB, significantly reduced the number of nematodes in the soil and simultaneously significantly reduced the number of nematode genera thereby reducing nematode diversity. All the four soil chemical fumigation activities decreased soil microbial biomass and had an obvious initial impact on microorganism biomass. Furthermore, both plant-parasitic and fungivore nematodes were positively correlated with soil microbial biomass.

Product oriented oxidative bromination of methane over Rh/SiO_2 catalysts

Rh/SiO2 was prepared for the oxidative bromination of methane. The catalyst was prepared by calcination at different temperatures and for different times to obtain catalysts with different specific surface areas for the purposes of producing either CH3Br or CH3Br and CO. It was found that the catalyst having a low specific surface area （calcined at relatively high temperature） favors the selective oxidation of methane to prepare CH3Br, while the catalyst having a high specific surface area favors the deeper partial oxidation of methane, which is good for CH3Br and CO preparation, The 650 h on stream life-time test revealed that the catalytic performance of the 0.4Rh/SiO2-900-10 catalyst was excellent. Both methane conversion and CH3Br selectivity kept increasing trends during the life-time test. No matter how serious was the Rh leaching during the reaction, the 0.4Rh/SiO2-900-10 catalyst did not deactivate at all.

Biofumigation: An alternative strategy for the control of plant parasitic nematodes

Plant-parasitic nematodes wreak havoc on the yield and quality of crops worldwide.Damage from these pests is estimated to exceed US$100 bllion annually but is likely higher due to misdiagnosis.Nematode damage may be catastrophic,but historically the solution has been damaging as well.Use of the synthetic nematicide methyl bromide(MBr)poses risks to the environment and to human health.Biofumigation,the use of plant material and naturally produced compounds to control pests,is an increasingly feasible method of pest management.The process acts through the growth or incorporation of plant material into the soil,that,over the course of its degradation,releases glucosinolates that break down into nematotoxic isothiocyanates.These secondary plant metabolites exist naturally in commonly grown plants,most of which belong to the Brassicaceae family.Research endeavors have increasingly explored the potential of biofumigation.The reaction of target pests,the selection of biofumigant,and ideal environments for efficacy continue to be evaluated.This review seeks to provide a cost and benefit assessment of the status of biofumigation for the control of plant-parasitic nematodes as an alternative to conventional methyl bromide usage.

Methane oxybromination over Rh-based catalysts:Effect of supports

Bromine mediation has been regarded as one of the most efficient ways to activate and convert methane to useful organics.This article reports the effects of active components(Rh,Ru,Pd and Pt)and supports(SiO2,Mg O and Al2O3)on the catalysis of methane oxybromination.Among the prepared catalysts,Rh/SiO2 is the best in performance(CH4 conversion of ca.20%and CH3Br selectivity exceeding 70%).The results reveal that support type has a notable influence on the catalytic performance of Rh,especially on product distribution.The high selectivity to CH3 Br over Rh/SiO2 is attributed to its low propensity for CH3Br oxidation.It was found that Rh small in particle size shows high catalytic activity and CH3Br selectivity.Although silicalite-1 zeolite suffers from a certain degree of structural damage due to the presence of high temperature steam,the use of silicalite-1 as support results in a performance comparable to that of Rh/SiO2.