Reaction of chlorine nitrate with hydrogen chloride and water at antarctic stratospheric temperatures

Laboratory studies of heterogeneous reactions important for ozone depletion over Antarctica are reported. The reaction of chlorine nitrate (ClONO(2)) with H(2)0 and hydrogen chloride (HCl) on surfaces that simulate polar stratospheric clouds [ice and nitric acid (HNO(3))-ice and sulfuric acid] are studied at temperatures relevant to the Antarctic stratosphere. The reaction of ClONO(2) on ice and certain mixtures of HNO(3) and ice proceeded readily. The sticking coefficient of ClONO(2) on ice of 0.009 +/- 0.002 was observed. A reaction produced gas-phase hypochlorous acid (HOCl) and condensed-phase HNO(3); HOC1 underwent a secondary reaction on ice producing dichlorine monoxide (Cl(2)O). In addition to the reaction with H(2)0, ClONO(2) reacted with HCl on ice to form gas-phase chlorine (Cl(2)) and condensed-phase HNO(3.) Essentially all of the HCl in the bulk of the ice can react with ClONO(2) on the ice surface. The gaseous products of the above reactions, HOCl, Cl(2)0, and Cl(2), could readily photolyze in the Antarctic spring to produce active chlorine for ozone depletion. Furthermore, the formation of condensed-phase HNO(3) could serve as a sink for odd nitrogen species that would otherwise scavenge the active chlorine.     

The potential for ozone depletion in the arctic polar stratosphere

The nature of the Arctic polar stratosphere is observed to be similar in many respects to that of the Antarctic polar stratosphere, where an ozone hole has been identified. Most of the available chlorine (HCl and ClONO(2)) was converted by reactions on polar stratospheric clouds to reactive ClO and Cl(2)O(2) throughout the Arctic polar vortex before midwinter. Reactive nitrogen was converted to HNO(3), and some, with spatial inhomogeneity, fell out of the stratosphere. These chemical changes ensured characteristic ozone losses of 10 to 15% at altitudes inside the polar vortex where polar stratospheric clouds had occurred. These local losses can translate into 5 to 8% losses in the vertical column abundance of ozone. As the amount of stratospheric chlorine inevitably increases by 50% over the next two decades, ozone losses recognizable as an ozone hole may well appear.     

Antarctic stratospheric chemistry of chlorine nitrate, hydrogen chloride, and ice: release of active chlorine

The reaction rate between atmospheric hydrogen chloride (HCl) and chlorine nitrate (ClONO(2)) is greatly enhanced in the presence of ice particles; HCl dissolves readily into ice, and the collisional reaction probability for ClONO(2) on the surface of ice with HCl in the mole fraction range from approximately 0.003 to 0.010 is in the range from approximately 0.05 to 0.1 for temperatures near 200 K. Chlorine (Cl(2)) is released into the gas phase on a time scale of at most a few milliseconds, whereas nitric acid (HNO(3)), the other product, remains in the condensed phase. This reaction could play an important role in explaining the observed depletion of ozone over Antarctica; it releases photolytically active chlorine from its most abundant reservoir species, and it promotes the formation of HNO(3) and thus removes nitrogen dioxide (NO(2)) from the gas phase. Hence it establishes the necessary conditions for the efficient catalytic destruction of ozone by halogenated free radicals. In the absence of HCl, ClONO(2) also reacts irreversibly with ice with a collision efficiency of approximately 0.02 at 200 K; the product hypochlorous acid (HOCI) is released to the gas phase on a time scale of minutes.     

The seasonal evolution of reactive chlorine in the northern hemisphere stratosphere

In situ measurements of chlorine monoxide (ClO) at mid- and high northern latitudes are reported for the period October 1991 to February 1992. As early as mid-December and throughout the winter, significant enhancements of this ozone-destroying radical were observed within the polar vortex shortly after temperatures dropped below 195 k. Decreases in ClO observed in February were consistent with the rapid formation of chlorine nitrate (ClONO(2)) by recombination of ClO with nitrogen dioxide (NO(2)) released photochemically from nitric acid (HNO(3)). Outside the vortex, ClO abundances were higher than in previous years as a result of NOx suppression by heterogeneous reactions on sulfate aerosols enhanced by the eruption of Mount Pinatubo.     

Atomic Chlorine and the Chlorine Monoxide Radical in the Stratosphere: Three in situ Observations

Three simultaneous observations of atomic chlorine (Cl) and the chlorine monoxide radical (ClO) are reported which encompass the altitude interval between 25 and 45 kilometers. Together, Cl and ClO form a gas-phase catalytic cycle potentially capable of depleting stratospheric ozone. Observed Cl and C1O densities, although variable, imply that chlorine compounds constitute an important part of the stratospheric ozone budget. The results are compared with recent models of stratospheric photochemistry which have been used as a basis for predicting ozone depletion resulting from fluorocarbon release.     

二氧化氯对青椒采后生理和贮藏品质的影响

【目的】研究二氧化氯(ClO2)对青椒的保鲜作用，为青椒的贮藏提供新方法。【方法】用二氧化氯气体(0、5、10、20、50 mg·L-1)处理青椒，研究二氧化氯对青椒采后生理和贮藏品质的影响。【结果】5、10、20、50 mg·L-1的ClO2处理对青椒的腐烂有明显的抑制作用，40 d时其腐烂率均小于对照的50%；其中50 mg L-1的处理对腐烂的抑制效果最明显，贮藏到30 d时才有腐烂发生，40 d只有对照的1/4。20、50 mg L-1ClO2可显著抑制青椒的呼吸(P<0.05)，5、10 mg·L-1对呼吸的抑制作用不显著(P>0.05)。除50 mg·L-1外，5、10、20 mg L-1ClO2处理使MDA含量低于对照，但无显著差异(P>0.05)。5 mg·L-1的处理可以减缓青椒叶绿素的降解，10、20、50 mg·L-1的处理使青椒叶绿素含量低于对照，但无显著影响(P>0.05)。ClO2可保持青椒的营养成分，对青椒VC、可滴定酸和可溶性固形物含量有一定的保留作用；对青椒的风味无影响。【结论】二氧化氯可以有效延缓青椒的采后生理变化，保持青椒的品质。     

Dynamics of the reaction of methane with chlorine atom on an accurate potential energy surface

The reaction of the chlorine atom with methane has been the focus of numerous studies that aim to test, extend, and/or modify our understanding of mode-selective reactivity in polyatomic systems. To this point, theory has largely been unable to provide accurate results in comparison with experiments. Here, we report an accurate global potential energy surface for this reaction. Quasi-classical trajectory calculations using this surface achieve excellent agreement with experiment on the rotational distributions of the hydrogen chloride (HCl) product. For the Cl + CHD(3) → HCl + CD(3) reaction at low collision energies, we confirm the unexpected experimental finding that CH-stretch excitation is no more effective in activating this late-barrier reaction than is the translational energy, which is in contradiction to expectations based on results for many atom-diatom reactions.     

二氧化氯在饮用水中消毒副产物的形成

[目的]研究二氧化氯消毒副产物的形成和各种操作参数的影响。[方法]采用腐殖酸作为模拟废水进行试验,考察高纯二氧化氯在饮用水消毒过程中三氯甲烷和二氧化氯无机副产物的生成情况,研究温度、反应时间、pH、腐殖酸浓度和二氧化氯浓度等因素对饮用水中三氯甲烷和无机副产物形成的影响。[结果]有机物浓度、二氧化氯浓度是三卤甲烷形成的主要因素,三卤甲烷的含量随着腐殖酸浓度的增加而增加,但反应4 h后低于7μg/L,当二氧化氯浓度大于1.2 mg/L时,可产生大量的三卤甲烷,而pH的影响不大,温度有一定影响。无机副产物的形成与ClO2/TOC的值有较强的关联,pH为6和7时的ClO3-和ClO2+ClO2-+ClO3-的含量要高于在其他pH时的含量。[结论]该研究可为有效控制三卤甲烷的形成提供参考。     

紫外分光光度法与碘量法测定二氧化氯稳定性的研究

[目的]利用紫外分光光度法和碘量法测定二氧化氯的稳定性.[方法]以粉剂二氧化氯为试验材料,确定紫外分光光度法和碘量法的试验条件,然后分别用2种方法研究温度、活化时间、降解时间对二氧化氯的影响.[结果]二氧化氯的最大吸收波长为357 ～ 360nm.利用碘量法测定二氧化氯溶液中ClO2和ClO2-的离子浓度,适宜pH 6.85 ～ 7.15.当二氧化氯溶液浓度增加或溶液温度升高时,紫外吸收时吸光值随之升高,同时碘量法显示溶液中ClO2和ClO2-的离子浓度也逐渐升高.二氧化氯使用时需活化210 ～ 220 min,此时溶液的吸光值最大,ClO2的离子浓度最高,ClO2-的离子浓度最低.二氧化氯使用时快速降解,溶液吸光值降低,溶液中ClO2和ClO2-的离子浓度下降.[结论]该研究可为粉剂二氧化氯的推广应用提供科学依据.     

稳定性ClO2溶液杀菌特性分析及其在葡萄干加工中的应用

测定了稳定性ClO2活化液中各种不同氧化性氯组分的含量,研究活化液经过改变pH、吹高纯氮气和吹高纯氮气后再稀释等处理后杀菌特性的变化情况;应用正交实验对稳定性ClO2活化液在葡萄干加工中的杀菌工艺进行优化并对其可行性作分析。结果表明:稳定性ClO2活化液中可氧化性氯主要以ClO2和ClO2-(亚氯酸根)形式存在,约占5%的ClO2对稳定性ClO2活化液的杀菌能力起到不可替代的作用;稳定性ClO2活化液对葡萄干原料的杀菌效果明显,经活化液浸泡处理后的葡萄干产品中可氧化性氯的残留非常低,不会对人体健康产生影响。     

ClO2/UV氧化法降解苯酚的研究

[目的]研究UV光催化联合ClO2降解水溶液中苯酚的方法。[方法]以模拟苯酚废水为处理对象,ClO2为氧化剂,UV作为辅助手段,考察ClO2/UV氧化处理苯酚废水工艺中ClO2投加量、UV辐照时间、废水pH等因素对苯酚处理效果的影响。[结果]处理质量浓度为100 mg/L的苯酚废水,pH在8左右,ClO2投加量为140 mg/L,UV辐照时间为30 min的条件下,处理效果最好,苯酚去除率高达99.6%。并且在相同的处理条件下,ClO2/UV氧化苯酚的效率明显高于单一ClO2或UV法,同时大大缩短了反应时间。[结论]ClO2/UV氧化法是一种行之有效的含酚废水的处理方法。     

In Situ Northern Mid-Latitude Observations of ClO, O3, and BrO in the Wintertime Lower Stratosphere

In order to test photochemical theories linking chlorofluorocarbon derivatives to ozone(O(3)) depletion at high latitudes in the springtime, several related atmospheric species, including O(3), chlorine monoxide(ClO), and bromine monoxide (BrO) were measured in the lower stratosphere with instruments mounted on the NASA ER-2 aircraft on 13 February 1988. The flight path from Moffett Field, California (37 degrees N, 121 degrees W), to Great Slave Lake, Canada (61 degrees N, 115 degrees W), extended to the center of the polar jet associated with but outside of the Arctic vortex, in which the abundance of O(3) was twice its mid-latitude value, whereas BrO levels were 5 parts per trillion by volume (pptv) between 18 and 21 kilometers, and 2.4 pptv below that altitude. The ClO mixing ratio was as much as 65 pptv at 60 degrees N latitude at an altitude of 20 kilometers, and was enhanced over mid-latitude values by a factor of 3 to 5 at altitudes above 18 kilometers and by as much as a factor of 40 at altitudes below 17 kilometers. Levels of ClO and O(3) were highly correlated on all measured distance scales, and both showed an abrupt change in character at 54 degrees N latitude. The enhancement of ClO abundance north of 54 degrees N was most likely caused by low nitrogen dioxide levels in the flight path.     

Correction

A typographical error in Table 1 of my paper "The Validity of the Use of Tracers to Follow Chemical Reactions" (Science, 1949, 110, 14), under the entries for chlorine makes the estimated maximum ratios for the tracers Cl(36) and Cl(38) somewhat ambiguous. The stable isotopes should be written as Cl (natural abundance). The ratios were calculated for reactions with the tracers Cl(36) and Cl(38) in systems containing chlorine of natural isotopic abundance. Due attention has been given to the fact that the Cl(35) and Cl(37) will react at different rates.     

Sulfur and chlorine in late Cretaceous Deccan magmas and eruptive gas release

Large-volume pāhoehoe lava flows erupted 67 to 65 million years ago, forming the Deccan Traps, India. The impact of these flood basalt eruptions on the global atmosphere and the coeval end-Cretaceous mass extinction has been uncertain. To assess the potential gas release from this volcanism, we measured sulfur and chlorine concentrations in rare glass inclusions inside crystals and on glassy selvages preserved within lavas. Concentrations range from approximately 1400 parts per million of S and 900 parts per million of Cl in inclusions down to a few hundred parts per million in the lava. These data indicate that eruptions of Deccan lavas could have released at most 0.103 weight % of S, yielding up to 5.4 teragrams of SO2 per cubic kilometer of lava. A more conservative estimate is 0.07 weight % of S and 0.04 weight % of Cl, yielding 3.5 teragrams of SO2 and 1 teragram of HCl for every cubic kilometer of lava erupted. The flows were very large in volume, and these results imply that huge amounts of S and Cl gases were released. The environmental impact from even individual eruptions during past flood basalt activity was probably severe.     

壳聚糖和二氧化氯对樱桃番茄联合保鲜效果研究

以樱桃番茄(Lycopeisicon esculentum Mill)为原料研究壳聚糖和二氧化氯联合保鲜的效果。首先测定单种药物对樱桃番茄失重率和腐烂率的影响,然后通过正交试验评价两种药物混合作用对总酸、总糖和维生素C等与贮存品质相关指标的影响,比较了在顺次处理的组合作用中二氧化氯和壳聚糖不同作用顺序的联合保鲜效果。结果表明,二氧化氯和壳聚糖单独作用时均能显著降低樱桃番茄的腐烂率,并在一定程度上降低失重率;正交试验显示,二氧化氯对维生素C的含量影响最大,而壳聚糖对失重率和总糖含量的影响最大,优化后混合保鲜剂的最佳配方为:壳聚糖浓度1%、二氧化氯浓度10.0 mg/L、乙酸浓度0.5%、浸泡时间3 min;联合作用时,在二氧化氯浸泡之后再进行壳聚糖涂抹能更有效降低腐烂率。试验证明了二氧化氯和壳聚糖联合作用具有可行性。     

二氧化氯处理对“徐香”猕猴桃贮藏品质的影响

以浙江省主产的‘徐香’猕猴桃为试验材料,研究了不同浓度二氧化氯（ClO₂）（0、20、50 mg·L^-1和80 mg·L^-1）处理的猕猴桃在（3±1）℃条件下贮藏期间品质的变化。结果表明,与对照相比,二氧化氯处理可以较好地保持猕猴桃果实贮藏期、尤其在贮藏后期的果实硬度,能显著抑制猕猴桃中的可滴定酸含量、可溶性糖含量和Vc含量的下降速率,但对可溶性固形物含量的影响效果不显著（p>0.05）。比较表明,猕猴桃采后ClO₂处理的适宜浓度为50 mg·L^_-1。     

Antarctic Ozone Depletion Chemistry: Reactions of N2O5 with H2O and HCl on Ice Surfaces

The reactions of dinitrogen pentoxide (N(2)O(5)) with H(2)O and hydrochloric acid (HCl) were studied on ice surfaces in a Knudsen cell flow reactor. The N(2)O(5) reacted on ice at 185 K to form condensed-phase nitric acid (HNO(3)). This reaction may provide a sink for odd nitrogen (NO(x)) during the polar winter, a requirement in nearly all models of Antarctic ozone depletion. A lower limit to the sticking coefficient, gamma, for N(2)O(5) on ice is 1 x 10(-3). Moreover, N(2)O(5) reacted on HCl-ice surfaces at 185 K, with gamma greater than 3 x 10(-3). This reaction, which produced gaseous nitryl chloride (ClNO(2)) and condensed-phase HNO(3), proceeded until all of the HCl within the ice was depleted. The ClNO(2), which did not react or condense on ice at 185 K, can be readily photolyzed in the Antarctic spring to form atomic chlorine for catalytic ozone destruction cycles. The other photolysis product, gaseous nitrogen dioxide (NO(2)), may be important in the partitioning of NO(x) between gaseous and condensed phases in the Antarctic winter.     

Toxaphene insecticide: a complex biodegradable mixture

Adsorption and gas-liquid chromatography separate toxaphene into at least 175 polychlorinated 10-carbon compounds including Cl(6), Cl(7), Cl(8), Cl(9), and Cl(10) derivatives. One toxic component is 2,2,5-endo,6-exo,8,9,10-heptachlorobornane. Rats metabolically dechlorinate toxaphene, removing about half of the chlorine from the technical insecticide and from each of seven subfractions of varying composition and toxicity.     

重庆市烤烟氯素营养研究

采用调查研究、田间试验和室内分析相结合的方法,于2001—2002年对重庆市烟区土壤、烟叶含氯量现状进行了调查研究,根据调查结果于2003—2004年进行了不同施氯量的田间试验,研究了氯对烟叶产量和质量的影响以及氯在土壤中的残留．结果表明：重庆植烟土壤含氯量低,平均为13．4mg／kg,严重缺氯的土壤（Cl≤2mg／kg）样本占19．2％;可能缺氯的土壤（Cl≤10mg／kg）占50％．重庆市烟叶含氯量很低,平均为0．70g／kg,有99％的烟叶样本含氯量低于优质烟叶要求的含氯下限（3g／kg）,烟叶含氯量低已成为影响烟叶质量的限制因素．烟叶含氯量随施氯量的增加而升高,二者呈直线或指数相关．施氯量在0～45kg／hm^2范围内,随着施氯量的增加烟叶产量、上等烟比例、产值、总糖和还原糖含量提高;施用适量氯（30～45kg／hm^2）能降低烟叶烟碱及总氮含量;施木克值、K2O／Cl、总糖／烟碱以及烟碱／总氮比趋于合理,协调了烟叶各化学成分的比例,改善了烟叶品质．氯在土壤中的残留量及其动态变化主要受降雨量和降雨强度的影响．重庆烟区的最佳推荐施氯量为30～45kgCl／hm^2．     

1-MCP和ClO2对甜樱桃布鲁克斯的防腐保鲜效果

[目的]探讨甜樱桃防腐保鲜技术,为减少甜樱桃采后腐烂、延长保鲜期和货架期提供理论依据.[方法]以布鲁克斯甜樱桃为试材,经40 mg/L二氧化氯(ClO2)溶液(蒸馏水配制)瞬时浸泡后,分别采用1-甲基环丙烯(1-MCP)单独处理和1-MCP+ClO2协同处理对甜樱桃进行低温贮藏保鲜试验,探讨1-MCP和ClO2对甜樱桃布鲁克斯的防腐保鲜效果.[结果]与1-MCP单独处理相比,1-MCP+ClO2协同处理的甜樱桃可溶性固形物、可滴定酸含量下降速度减慢,果实腐烂率和失重率明显降低,且以40 mg/L ClO2+0.5 μL/L 1-MCP的效果最佳.[结论]1-MCP+ClO2协同作用能够有效降低甜樱桃布鲁克斯在贮藏保鲜过程中的腐烂率,延缓果实衰老,延长贮藏保鲜期.