Comparison of H2O2 and O3 content in atmospheric samples in the San Bernardino mountains,Southern California

Concentrations of atmospheric H₂O₂ were measured in air, rain, cloud and dew samples in forested areas of the San Bernardino Mountains, southern California, from spring through fall of 1987–1990 O₃ measurements in air were also conducted for comparison. Typical ranges of H₂O₂ concentrations measured were 1–3 ppb in air, 10–90 μM in rain and cloud water, and < μM in dew. The results show that gas-phase H₂O₂ concentrations were slightly higher at nighttime than at daytime or nearly constant throughout a 24-hr period, whereas O₃ concentrations were highest during the afternoon, when polluted air masses from Los Angeles carried by daily sea breezes reached the mountain region. Afternoon concentrations of gaseous H₂O₂ and O₃ in the mountain region were compared with those measured in Los Angeles urban sites to elucidate the regional variation of these oxidants. The results show that ambient concentrations of H₂O₂ and O₃ were about 50–100% higher at the mountains sites than at the Los Angeles sites.     

Field investigations on the snow chemistry in central and southern california—II. Carbonyls and carboxylic acids

Snow samples from central and southern California were collected during the winter of 1987–1988 from there storms and analyzed for carbonyl compounds and carboxylic acids. Approximately 90% of the samples contained total aldehyde concentrations up to 40 μM. Formaldehyde and acetaldehyde were the dominant aldehydes observed; secondary aldehydes included glyoxal, methylglyoxal, and benzaldehyde. The highest aldehyde concentrations were observed in snow collected in areas where deciduous and coniferous forests are widespread. However, these aldehydes can be attributed also in part to primary and secondary products of anthropogenic activities. Formic and acetic were analyzed in all measured samples with concentrations ranging from 0.5 to 4.9 μM for HCOOH and from <0.3 to 13.4 μM for CH₃COOH. Maximum contribution of organic acids to precipitation-free acidity, calculated by assuming that the only sources of the measured formate and acetate were their respective acid forms, averaged 43.1% for samples with a pH⩽5. A consistent correlation between NH₄⁺ and acetate was found. [CH₃COOH] exceeded [HCOOH] in about 50% of the samples with the highest levels for CH₃COOH measured in cores collected from lower elevated locations adjacent to the Los Angeles basin. Results presented in this paper suggest that dry deposition and/or scavenging of carbonyl compounds and organic acids to snow may be important sinks for these compounds.     

镧对酸雨胁迫下水稻叶片质膜H+-ATPase活性的影响

为了明晰稀土提高植物抗酸性的内在机制,采用水培法研究了镧(La,15 mg·L~(-1))对酸雨(AR,pH=3.5、2.5)胁迫下水稻叶片质膜H+-ATPase活性的影响.结果显示:与CK相比,pH=3.5 AR组水稻相对生长速率减小,质膜H+-ATPase活性升高,胞内H+增多,CAT活性升高,H_2O_2和MDA含量升高,质膜脂肪酸不饱和度指数(IUFA)降低.La+pH 3.5 AR组水稻各项指标优于pH=3.5 AR组,表明La促使AR下质膜H+-ATPase活性升高,将胞内过多的H+泵出,减缓AR伤害,维持水稻正常生长.另外,La能增强CAT活性,清除过多的H_2O_2,减轻膜脂过氧化程度,使质膜IUFA升高,膜的流动性增强,提高质膜H+-ATPase活性.pH=2.5 AR组水稻相对生长速率、质膜H+-ATPase活性、CAT活性与质膜IUFA均降低,而胞内H+、H_2O_2和MDA含量升高.La+pH 2.5 AR组与pH=2.5 AR组水稻各指标均无明显差异,La对pH=3.5 AR组的缓解效果优于pH=2.5 AR组.综上可知,La对AR下质膜H+-ATPase活性的调节增强了植物耐酸性,这与La能维持AR下较好的质膜环境有关.同时,La的调控效果受AR强度限制.     

Characterization of precipitation in the background of atmospheric pollutants reduction in Guilin: Temporal variation and source apportionment

Rainfall samples were collected from three observation sites in Guilin from 2013 to 2017, and the chemical composition characteristics of precipitation and the contribution made by different ion sources were analyzed when atmospheric pollutants levels were reduced. The results showed that acid gas emissions and atmospheric pollutant concentrations continued to decline during the study period. However, the change in the volume-weighted mean pH at the three sites suggested that acid rain pollution was not alleviated and began to deteriorate after 2015. The continuing downward trend for alkaline neutralizing ions (Ca²⁺, NH₄⁺) in precipitation indicated that the reduction in alkaline neutralizing substances in the atmosphere was an important factor that led to the deterioration in acid rain across Guilin. The principal component analysis and spearman correlation analysis indicated five sources of ions in precipitation. Quantitative assessment of these five sources indicated that fossil fuel combustion contributed the most ions concentration in precipitation at the three sites, followed by agriculture, terrestrial (crustal) sources, marine sources, and biomass burning. Long-distance airflow might affect the acidity, the electrical conductivity (EC), and ion concentrations in precipitation across Guilin. The airflow trajectory from the west and southeast directions corresponded to higher acidity and ion concentrations. According to the current air pollution control strategy planned by Guilin, reducing atmospheric coarse particles and NH₃ at the same time may potentially lead to further deteriorations in acid rain contents. Therefore, Guilin needs to develop more reasonable pollution prevention measures that synergistically control atmospheric pollutants and acid rain pollution.     

Numerical simulation of wet scavenging of air pollutants—II. Modeling of rain composition at the ground

The modeling of rain composition for a convective shower (Tucson, AZ, 10 September 1977) and a frontal precipitation event (Den Helder, Holland, 12 December 1978) is performed in this paper by including the pollutant species and wet scavenging mechanisms into the mass transport equation of the sequential sampling model described in Part I of this series. The results indicate that: (1) the major scavenging mechanisms of most pollutants in convective showers appear to be similar to those in frontal precipitations; (2) the major scavenging mechanisms of NH₄ and NO₃ are gas absorption, whereas the absorption of SO₂ by aqueous drops and oxidation of S(IV) by H₂O₂ and O₃ in the aqueous phase are the major formation and scavenging mechanisms for SO₄; (3) the scavenging by raindrops in the below-cloud region is the dominant removal mechanism for coarse particles, whereas nucleation is the major scavenging mechanism for submicrometer particles; (4) H₂O₂ is the most important oxidant responsible for the oxidation of S(IV) and the formation of sulfate in precipitation; (5) the contributions of both (SO₂ + H₂O₂) and (SO₂ + O₃) reactions to sulfate concentration in precipitation are larger for convective precipitation than for frontal precipitation.     

深圳大气降水的化学组成特征

为了了解近年来深圳降水的化学特征与大气污染状况,连续2 a采集了深圳降水样品,分析其化学组分.结果表明,与北京等中国北方内陆城市相比,深圳降水中离子浓度比较低,但降水的酸化程度和酸化频率非常高,雨量加权pH值在2004年和2005年分别为4.48和4.68,酸化频率分别为88%和91%,降水酸化严重;相对中国内陆酸雨城市,深圳降水中SO24-对雨水酸性贡献相对较低,而NO-3和Cl-对雨水阴离子总量及降水酸性的贡献相对较大;Cl-和Na 对雨水阴阳离子的贡献较高,深圳降水受海洋的影响显著;SO24-、NO-3、NH 4等二次组分在雨水中占有很高比例,三者之和超过离子总量的40%,表明深圳大气环境中二次污染突出;降水中不同组分的来源差别较大,Cl-、K 、Na 主要来自海洋源,而SO24-、NO-3、Ca2 、Mg2 主要来自非海洋源;甲酸、乙酸和乙二酸是深圳降水中主要的有机酸,三者之和在2004年和2005年分别占检测到的有机酸总量的94%和99%.     

Insight into removal of dissolved organic matter in post pharmaceutical wastewater by coagulation-UV/H2O2

The removal of four dissolved organic matter (DOM) fractions, non-acid hydrophobics, hydrophobic acids, hydrophilics and transphilics, was achieved by coagulation-UV/H₂O₂ oxidation in post-pharmaceutical wastewater (PhWW). Coagulation with Polyferric chloride (PFC), Polymeric ferric sulfate (PFS) and Polymeric aluminum ferric chloride (PAFC) was studied separately to evaluate the effects of the initial pH and coagulant dosage. The coagulation-UV/H₂O₂ oxidation method resulted in much higher reduction rates for dissolved organic carbon (DOC) (by 75%) and UV₂₅₄ (by 92%) than coagulation or UV/H₂O₂ oxidation alone. The proportion of non-acid hydrophobics, hydrophobic acids, transphilics and hydrophilics removed by coagulation was 54%, 49%, 27% and 12 %, while the combined treatment removed 92%, 87%, 70% and 39%, respectively. Parallel factor analysis (PARAFAC) of fluorescence measurements revealed that the humic-like fluorescent component C4 showed the highest removal (by 44%) during the coagulation stage. After coagulation-UV/H₂O₂ treatment, the humic-like fluorescent component C3 had the highest removal (by 72%), whereas xenobiotic organic fluorescent components C1 and C4 remained recalcitrant to decomposition. Significant correlations (R² > 0.8) between C1 and the hydrophobic acids and non-acid hydrophobics suggested the possibility of using fluorescence spectroscopy as an effective tool to assess variations in DOM fraction treatment efficacy in coagulation-UV/H₂O₂ systems. After the combined treatment, toxic inhibition of cellular activity by post PhWW decreased from 88% to 47% and biodegradability increased from 0.1 to 0.52.     

Atmospheric H2O2 field measurements in a tropical environment: Bahia,Brazil

Concentrations of H₂O₂ in atmospheric gas and liquid phases were determined for the first time in the tropical Southern Hemisphere. Measurements were carried out in the Salvador area, Bahia, 13°S, 38°W) both at the seaside and 500 m away from it as well as at 270 km inland, in a rural area, during March–April 1988. Gaseous H₂O₂ was collected by cryogenic and rain by wet only sampling. Analyses were performed with the peroxyoxalate chemiluminescence method, employing a compact field apparatus. The measured gas phase concentrations ranged from 0.2 to 3.9 ppbv compared to 0.01-0.6 ppbv obtained from measurements with similar methodology in Dortmund (51°30'N, 7°30'E), F.R.G, during summer. The corresponding concentration ranges in rainwater are 0.9-6.8 ppmw (Bahia) and 0.1–2.2 ppmw (Dortmund, summertime). Gas/liquid H₂O₂ equilibrium during rain events is only attained at precipitation rates below 1 mm h⁻¹.     

A captive-air irradiation study of the response of nitric acid and peroxyacetyl nitrate to ozone control strategies in Los Angeles

Outdoor smog chamber experiments were used to study the sensitivity of the yields of two important nitrogen-containing pollutants, nitric acid (HNO₃) and peroxyacetyl nitrate (PAN) to changes in nonmethane hydrocarbon (HC) and nitrogen oxide (NO_x) concentrations in Los Angeles. The experiments were conducted at two sites in the Los Angeles Basin using eight chambers filled with morning Los Angeles air on 33 days. At least one chamber was unchanged and served as a control, while the initial HC and/or NO_x concentrations were changed by 25–50% in up to seven chambers to simulate O₃ control strategies and to broaden the range of HC - NO_x conditions studied. Empirical models that predict the maximum yields of HNO₃ and PAN were used to determine the response of these pollutants to three possible ozone control strategies. All three strategies (reductions in HC, NO_x or both HC and NO_x) reduced PAN while only NO_x reductions decreased HNO₃. However, reducing NO_x increased the HC reductions required to attain lower O₃ levels. Thus, there is a conflict between the O₃ and HNO₃ control strategies.     

广州白云山春季降水及广西苗儿山云雾水中有机弱酸的研究

利用离子色谱法测量了广州白云山春季降水及广西苗儿山云雾水中的甲酸和乙酸,并同时测定了降水中阴离子(F^-,Cl^-,SO₄^2-,NO₃^-)和阳离子(Na⁺,NH₄⁺,K⁺,Ca²⁺,Mg²⁺。用多元逐步回归、多对多双重筛选回归及R聚类分析的多元统计的数学方法分析了降水中有机弱酸间及与阴阳离子间的关系。讨论了有机酸的来源及其对酸雨中酸度的贡献。     

Decontamination of alachlor herbicide wastewater by a continuous dosing mode ultrasound/Fe2+/H2O2 process

We used a ultrasound/Fe2+/H2O2 process in continuous dosing mode to degrade the alachlor.Experimental results indicated that lower pH levels enhanced the degradation and mineralization of alachlor. The maximum alachlor degradation(initial alachlor concentration of 50 mg/L) was as high as 100% at pH 3 with ultrasound of 100 Watts, 20 mg/L of Fe2+, 2 mg/min of H2O2 and 20℃ within60 min reaction combined with 46.8% total organic carbon removal. Higher reaction temperatures inhibited the degradation of alachlor. Adequate dosages of Fe2+and H2O2 in ultrasound/Fe2+/H2O2process not only enhance the degradation efficiency of alachlor but also save the operational cost than the sole ultrasound or Fenton process. A continuous dosing mode ultrasound/Fe2+/H2O2 process was proven as an effective method to degrade the alachlor.     

Photodegradation of amoxicillin by catalyzed Fe3+/H2O2 process

Three oxidation processes of UV-Fe³⁺(EDTA)/H₂O₂ (UV: ultraviolet light; EDTA: ethylenediaminetetraacetic acid), UV-Fe³⁺/H₂O₂ and Fe³⁺/H₂O₂ were simultaneously investigated for the degradation of amoxicillin at pH 7.0. The results indicated that, 100% amoxicillin degradation and 81.9% chemical oxygen demand (COD_Cr) removal could be achieved in the UV-Fe³⁺ (EDTA)/H₂O₂ process. The treatment efficiency of amoxicillin and COD_Cr removal were found to decrease to 59.0% and 43.0% in the UV-Fe³⁺/H₂O₂ process; 39.6% and 31.3% in the Fe³⁺/H₂O₂ process. Moreover, the results of biodegradability (biological oxygen demand (BOD₅)/COD_Cr ratio) revealed that the UV-Fe³⁺ (EDTA)/H₂O₂ process was a promising strategy to degrade amoxicillin as the biodegradability of the effluent was improved to 0.45, compared with the cases of UV-Fe³⁺/H₂O₂ (0.25) and Fe³⁺/H₂O₂ (0.10) processes. Therefore, it could be deduced that EDTA and UV light performed synergetic catalytic effect on the Fe³⁺/H₂O₂ process, enhancing the treatment efficiency. The degradation mechanisms were also investigated via UV-Vis spectra, and high performance liquid chromatography-mass spectra. The degradation pathway of amoxicillin was further proposed.     

Receptor modeling of the fine aerosol at a residential Los Angeles site

Receptor modeling on ambient aerosol and air quality data collected at Duarte, CA (a residential site near Los Angeles), in 1983 and 1987–1988 was carried out. A significant change in the ambient concentrations of SO₄²⁻, Al, Si, Mn, Fe, Pb, Br, volatile and organic carbon and fine particle (FP) mass took place from 1983 to 1987–1988. A drastic reduction (∼80%) of the ambient Pb and Br concentrations took place as the lead content and the usage of leaded gasoline decreased in the Los Angeles Basin during that period. A day-of-the-week analysis indicated that both crustal (Si, Ca, Fe) and transportation (Pb, CO, organic carbon and black carbon) related pollutants exhibit significantly different concentrations between weekdays and weekends of 1987–1988. this indicates that loadings of suspended soil dust are more affected by anthropogenic activities than meteorological patterns. In contrast, sulfate and volatile carbon concentrations seem to be insensitive to that cycle indicating that other sources/processes can be responsible for the ambient levels of these pollutants. Principal component analysis of aerosol and air quality data showed that the major contributions to the variance of the ambient aerosol loadings come from soil, motor vehicles and sulfates.     

Atmospheric gaseous organic acids in winter in a rural site of the North China Plain

Organic acids are important contributors to the acidity of atmospheric precipitation,but their existence in the Chinese atmosphere is largely unclear.In this study,twelve atmospheric gaseous organic acids,including C₁-C₉ alkanoic acids,methacrylic acid,pyruvic acid,and benzoic acid,were observed in the suburb of Wangdu,Hebei Province,a typical rural site in the northern China plain from 16^th December,2018 to 22^nd January,2019,using a Vocus@Proton-Trans...     

邻苯二甲酸二甲酯的紫外光-H2O2降解机制研究

为研究邻苯二甲酸二甲酯(DMP)在紫外光(UV)-H2O2体系下的光降解机制,利用质谱仪鉴定了目标化合物的降解产物,并借此推测其可能的降解途径.结果表明,在UV-H2O2的体系中,10 mg.L-1的DMP在90 min内的降解率达到92.3%,溶液pH值由初始的6.50降至4.98.通过GC/MS、LC/MS分析,DMP在UV-H2O2降解过程中的产物有六类,并且推断出DMP的两条侧链同时发生水解作用,生成的邻苯二甲酸可以异构为更加稳定的对苯二甲酸.此外,DMP还可以发生苯环取代、侧链缩合成环等反应,最后,在.OH的作用下,DMP及其芳香族中间产物发生开环反应,苯环被破坏,生成多种小分子有机酸,并进一步矿化为CO2和水.     

Response of ozone to changes in hydrocarbon and nitrogen oxide concentrations in outdoor smog chambers filled with Los Angeles air

During the summer portion of the 1987 Southern California Air Quality Study (SCAQS), outdoor smog chamber experiments were performed on Los Angeles air to determine the response of maximum ozone levels, O₃(max), to changes in the initial concentrations of hydrocarbons, HC, and nitrogen oxides, NO_x. These captive-air experiments were conducted in downtown Los Angeles and in the downwind suburb of Claremont. Typically, eight chambers were filled with LA air in the morning. In some chambers the initial HC and/or NO_x concentrations were changed by 25% to 50% by adding various combinations of a mixture of HC, clean air, or NO_x. The O₃ concentration in each chamber was monitored throughout the day to determine O₃(max).An empirical mathematical model for O₃(max) was developed from regression fits to the initial HC and NO_x concentrations and to the average daily temperature at both sites. This is the first time that a mathematical expression for the O₃-precursor relationship and the positive effect of temperature on O₃(max) have been quantified using captive-air experiments. An ozone isopleth diagram prepared from the empirical model was qualitatively similar to those prepared from photochemical mechanisms. This constitutes the first solely empirical corroboration of the O₃ contour shape for Los Angeles.To comply with the Federal Ozone Standard in LA, O₃(max) must be reduced by approximately 50%. Several strategies for reducing O₃(max) by 50% were evaluated using the empirical model. For the average initial conditions that we measured in LA, the most efficient strategy is one that reduces HC by 55–75%, depending on the ambient HC/NO_x ratio. Any accompanying reduction in NO_x would be counter-productive to the benefits of HC reductions. In fact, reducing HC and NO_x simultaneously requires larger percentage reductions for both than the reduction required when HC alone is reduced. The HC-reduction strategy is the most efficient on average, but no single strategy is the optimum every day.     

基于δ15N和δ18O的农业区地下河硝酸盐污染来源

为研究岩溶区农业活动为主导的地下河流域硝酸盐污染来源,于2017年5~10月每24 d左右对重庆青木关流域6个采样点进行监测,利用~(15)N和~(18)O同位素技术对示踪硝酸盐来源进行解译,应用IsoSource模型计算出不同端元硝酸盐的贡献率.结果表明:(1)青木关农业区地下河系统存在较大的硝酸盐污染风险,大部分采样点出现不同程度NO_3~--N浓度超标现象.(2)空间上,青木关地下河中NO_3~--N浓度整体呈现由上游向下游升高的趋势.时间上,上游鱼塘和岩口落水洞以及下游姜家泉样点NO_3~--N浓度在5~6月因受农业施肥的影响,均呈上升趋势,6~9月受降水影响而出现不同程度升高或降低,9月之后随着农业活动减少而逐渐降低;中游土壤点NO_3~--N浓度保持较高值;中下游大鹿池NO_3~--N浓度较低且变幅不大.(3)通过硝酸盐~(15)N和~(18)O同位素分析,表明上游鱼塘和岩口落水洞的硝酸盐源于土壤有机氮、动物粪便及污废水混合;中游土壤点硝酸盐源于土壤有机氮、降水和肥料中NH_4~+;中下游大鹿池中硝酸盐来源于动物粪便及污废水、土壤有机氮、降水和肥料中NH_4~+的混合作用.地下河出口处姜家泉硝酸盐污染严重,其源于土壤有机氮、降水和肥料中NH_4~+、动物粪便及污废水、大气沉降的综合作用.(4)基于IsoSource模型对地下河出口处硝酸盐来源进行定量分析,发现动物粪便及污废水贡献率占46.4%,土壤有机氮占32.6%,降水与肥料中NH_4~+占18.6%,大气沉降仅占2.4%.     

中国西南酸雨区降水化学特征研究进展

西南酸雨区为我国主要酸雨沉降区,且是全球三大喀斯特集中分布区之一.本文将该区9个地点的降雨资料进行了总结、整理和分析,数据包括pH值和主离子成分(Cl~-、SO_4~(2-)、NO_3~-、Ca~(2+)、NH_4~+、Mg~(2+)、K~+、Na~+).该地区降雨中的主要阴离子为SO_4~(2-)和NO_3~-,主要阳离子为Ca~(2+)和NH_4~+.与我国其它地区相比,其酸性离子、碱性离子和总离子浓度均普遍高于东南地区、而低于我国北方地区.西南酸雨区主要以pH值为4.5~5.6的弱酸性降雨为主,占总降雨频次的58%左右.根据酸、碱性离子的相关性、中和因子等分析结果,该区雨水中的酸性物质可能受到了碱性离子的中和作用,其中起主要中和作用的离子为Ca~(2+)和NH_4~+.将该区雨水pH值和酸、碱性离子浓度与我国其它地区进行对比研究发现,西南酸雨区降雨受到的中和作用要强于东南地区,但弱于北方地区的降雨.通过对西南酸雨区降雨中主要离子来源的分析和估算,降雨中的酸性离子SO_4~(2-)和NO_3~-主要来自于人为污染;99.7%的Ca~(2+)和84.0%的Mg~(2+)为陆源贡献,这可能与西南地区碳酸盐岩广泛分布有关.     

Fe2+-H2O2法处理DSD酸生产氧化母液的研究

为改善DSD酸氧化母液的可生化降解性,将废液先用有机絮凝剂TS-1(一种季胺盐)处理,TS-1的投加量为3g/L,其后用Fe²⁺-H₂O₂法氧化,Fe²⁺和H₂O₂的量分别为150mg/L,7g/L,废液COD和色度的去除率分别可达64%和62%。经处理后的废水,其BOD₅/COD≈0.3,可以认为已达到生化处理的要求。当H₂O₂的投量为2g/L,经Fe²⁺-H₂O₂氧化处理后的废液,再用FeCl₃进行两级混凝处理(FeCl₃的投加量分别为5g/L和2g/L),则COD和色度的去除率可达90%和95%。     

A numerical experiment on the relative importance of H2O2 O3 in aqueous conversion of SO2 to SO42-

The importance of the three major aqueous reactions thought to be responsible for the in-cloud conversion of SO₂ to SO₄^2- was studied using the acidic deposition and oxidants model by supressing each reaction individually and all reactions simultaneously. The reactions are the oxidation of SO₂ by H₂O₂, or O₃ and catalytic oxidation by O₂ in the presence of Fe and Mn. The model simulations were 19–24 April 1981. It was found that SO₄^2- precipitation concentrations were generally more sensitive to H₂O₂ oxidation than to O₃ oxidation. The contribution of catalytic oxidation of SO₂ in the presence of Fe and Mn is insignificant everywhere and at all times. The contributions of H₂O₂ oxidation to SO₄^2- in precipitation is strongest in light precipitation areas while O₃ oxidation can be greater than H₂O₂ oxidation in heavy precipitation areas. The effect of supressing one reaction is mitigated by compensation through another mechanism. This is seem from the significant difference observed in the effects when individual suppressions were added together and when all reactions were suppressed simultaneously. From this, it is estimated that the contribution of aqueous oxidation of SO₂ to SO₄^2- in precipitation is approximately 50–80 per cent. Further simulations show that the relationship between SO₂ emissions and SO₄^2- production in the aqueous-phase through the oxidation reaction with O₃ is always non-linear in view of the pH dependence of the reaction rates.