Comparison of annular denuder and filter pack collection of HNO3 (g), HNO2((g), SO2 (g), and particulate-phase nitrate,nitrite and sulfate in the south-west desert

During the 15 January–4 February 1986 SCENES Special Study, a comparison study was conducted to determine atmospheric HNO₃ (g), HNO₂ (g), SO₂ (g), and particle-phase nitrate, nitrite and sulfate sampled with annular diffusion denuder and filter pack sampling systems for 12-h periods. The results of the ion chromatographic analyses of the denuder and filter extracts from the annular denuder system showed that an average of 88% of the total nitrate measured was HNO₃ (g), 97% of the total nitrite was HNO₂ (g), and 91% of the total sulfur was present as SO₂ (g). Analyses of the various gas-phase species collected by replicate annular denuder systems indicated that a precision of ± 3% to ± 18% was achieved using these denuders. The good agreement in HNO₃ (g) concentrations observed between the filter pack and the denuder (r²=0.873, slope=1.06±0.03, intercept=0±3.5 nmol m⁻³) results from the fact that the majority of the atmospheric nitrate consisted of HNO₃ (g), which minimized any positive artifact in HNO₃(g) due to loss of HNO₃(g) from particles collected in the filter pack. The particulate-phase nitrate correlation between the two sampling systems was not as good (r²=0.709, slope=0.519±0.045, intercept =0±1.2 nmol m⁻³) because the lower percentage of nitrate present as the particulate species was more affected by the loss of particulate nitrate during sampling with the filter pack.     

Southern California air quality study: A search for methyl nitrate

Methyl nitrate, CH₃ONO₂, was measured by electron capture gas chromatography (EC-GC) under conditions which allowed resolution of methyl nitrate, PAN, and several chlorinated hydrocarbons. Calibrations involved both EC-GC andNO_x chemiluminescence and were in agreement with independent calibrations involving i.r. spectroscopy. The rate constant for photolysis of methyl nitrate in sunlight was< 2.3 × 10⁻⁶s⁻¹. Detection limits of field instruments were 0.1–0.4 ppb. Some 3000 EC-GC chromatograms grams of ambient air recorded between June and December 1987, during the Southern California Air Quality Study (SCAQS) at up to nine Southern California locations yielded only seven possible, but unlikely observations of methyl nitrate. Thus, methyl nitrate was only a minor component among nitrogenous air pollutants during SCAQS. The measured CH₃ONO₂/PAN ratios of<0.003–0.2 during SCAQS are discussed in terms of available kinetic data for PAN unimolecular decomposition (a major source of methyl nitrate), PAN thermal decomposition and CH₃ONO₂ photolysis.     

Electrochemical measurement of carbon monoxide in breath: Interference by hydrogen

The purpose of this study was to determine the concentration of carbon monoxide (CO) in blood (COHb) and breath to demonstrate that breath hydrogen (H₂) can be a significant interferant. For this purpose, we measured blood COHb with CO-oximetry and breath CO with an electrochemical analyzer. In addition, the samples were analyzed by gas chromatography (GC). The concentration of CO in breath, collected with a Priestley tube after a 20 s breath hold, from healthy, nonsmoking adult males (n = 20) and females (n = 10) had a mean ± SD (range) of 2.6 ± 0.4 ppm (2.0–3.9), respectively, when measured by GC. However, these same samples when measured with an electrochemical (EC) analyzer showed elevated CO values of 4.7 ± 2.9 ppm (2.6–17.6). The concentration of H₂, a prominent trace gas in breath known to interfere with EC analyzers, correlated strongly with the observed EC analyzer response [EC (ppm CO) = 0.336 H₂ (ppm) + 1.93, r² = 0.98]. The EC analyzer was linear for H₂ concentrations up to 40 ppm, with a sensitivity of 0.035 V ppm⁻¹. The analyzer sensitivity to CO was 0.10 V ppm ⁻¹. Blood from this population showed COHb concentrations of 0.56 ± 0.11% (0.40–0.97), as measured by GC, but elevated values were found when measured by CO-oximeter (Ciba Corning Diagnostics Corp., Models 2500 and 270), 1.3 ± 0.2% (1.1–1.6) and 1.0 ± 0.3% (0.1–1.6), respectively. When breath CO was compared to blood COHb, only measurements by GC significantly correlated [COHb% = 0.241 CO(ppm) — 0.076, r² = 0.78]. We conclude that, relative to quantitative analysis by GC, (1) EC analyzers are susceptible to H₂ interference that cause falsely elevated CO measurements, and (2) CO-oximeters overestimate COHb concentrations in the range typical for healthy nonsmokers.     

Field tests of a passive sampler for atmospheric ozone at California mountain forest locations

Field tests of a colorant-based ozone passive sampler have been carried out during the 1990 smog season at five mountain forest locations in California. Co-located measurements of ambient ozone were made at all field sites using the passive sampler and a reference method, ultraviolet (u.v.) photometry. The sampling duration ranged from 3 to 30 days. Nitrogen dioxide, aldehydes and the phytotoxic oxidants peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN) were measured at one location to assess possible interferences. The average precision of the measurements, calculated from data for 42 sets of colocated passive samplers, was 12%. Data for all field locations could be reduced to a single equation relating color change (ΔE units) to ozone dose (units: ppb-days). This polynomial equation could be reduced to a linear equation for color changes not exceeding 8 ΔE units (equivalent to sampling durations of up to 15 days), with good agreement between field data and earlier calibration results obtained in the laboratory. Both polynomial and linear equations can be used to obtain quantitative, time-integrated measurements of ambient ozone. The performance of the passive sampler showed no dependence on changes in ambient temperature and humidity. Interferences from air pollutants other than ozone contributed a total positive bias of less than 5% to the measured ozone concentrations: 3% for NO₂, 1.3% for PAN, 0.2% for PPN, and 0.% or less for formaldehyde and acetaldehyde.     

Laboratory tests of KI and alkaline annular denuders

Annular denuders coated with KI and with alkaline solutions have been tested for their ability to remove atmospheric pollutants including ozone, NO₂, SO₂, formaldehyde, methyl nitrate and peroxyacetyl nitrate. Tests were carried out at flow rates of 0.4–2.0 ℓ min⁻¹, using particle-free ambient air as well as purified air to study the effect of atmospheric CO₂ on alkaline denuder performance. Denuders coated with KI were efficient in removing O₃, NO₂, SO₂ (> 95%) and PAN (84±3%) but not methyl nitrate (44%) and formaldehyde (<5%). Selective removal of PAN from NO₂, and vice versa, could be obtained with annular denuders coated with NaOH, which removed 100% PAN and ⩽15% NO₂, and with alkaline guaiacol, which removed ⩾99% NO₂ and ⩽6% PAN.     

Heterogeneous transformation of peroxyacetylnitrate

The heterogeneous decomposition of peroxyacetylnitrate (PAN) has been investigated using a flow reactor and infrared spectroscopic analysis. The decomposition rate in air due to glass surfaces follows the relation d[PAN]/dt = −S/V([PAN] × 7 × 10⁷ + [CH₃C(O)OO] × 5 × 90¹²)exp(−9382/T) molecules cm⁻³ s⁻¹ (S/V=surface to volume ratio). The rate observed for NH₄HSO₄-covered surfaces is lower than in the glass case. The rate is high enough to affect many laboratory experiments but too slow to have any influence on PAN decomposition under ambient conditions.     

中国西部本底大气中CO的连续测量

在中国西北部的瓦里关全球基准站(36°17'N,100°54'E,3810m asl)建立了气相色谱-汞置换法大气CO连续测量系统.组装调试和运行标定表明,色谱方法的基线稳定,分离度高,检测方法可靠,系统具有高自动化的操作性能和严格的质量控制,其设计完全符合世界气象组织(WMO)全球大气本底测量的要求.根据采样现场大气CO浓度的变化,采用经国际比对的CO标准气系列,用峰高外标法设定可调整的标准工作曲线计算环境CO浓度,系统对CO的检测限低至1×10^-9(V/V),检测精度小于0.1%,准确度在±0.05%以内,可提供我国本底地区近地层大气CO连续而精确的现场测量结果.     

夏季北京市大气中PAN与PPN的监测分析

采用在线监测仪器,在2005-08对北京市中关村地区大气中的PAN和PPN浓度进行了监测.结果表明,大气中存在着高浓度的PAN和PPN,其最高体积分数分别为2 493.2×10^-12和509.2×10^-12;PPN与PAN的浓度相关性很强,相关系数R²=0.949 5;［PPN］/［PAN］为20.2%. PAN和PPN的浓度在夜间有1个峰值出现,白天高浓度的PAN和PPN出现在NO₂浓度较高而NO浓度较低的时段,PAN与O₃的浓度变化趋势基本一致并显示出一定的相关性.     

大气中几种痕量烃类化合物连续自动检测

本文报道在环境大气中有机污染物的全自动新分析方法。本方法采用由计算机控制的GC、大气样品浓缩管、电磁六通阀、真空泵及微处理机组成的全自动连续分析装置、完成定性定量分析。连续三周在呼和浩特市以每小时为一分析周期,用此装置检测了环境大气中正己烷、苯、甲苯、O-甲苯、M-甲苯、P-甲苯等16种有机污染物,获得较满意的结果。     

国庆期间南岭背景大气中PAN的浓度特征与来源

为了评估华南地区国庆期间频发的大范围区域光化学污染事件对华南背景大气的影响,2018年国庆节前后（9月19日~10月19日）,在广东南岭国家大气背景站对光化学污染的代表产物过氧乙酰硝酸酯（PAN）开展了连续在线观测,并对PAN的浓度特征和来源进行了分析.结果表明,研究期间南岭PAN的平均体积浓度为（0.66±0.54）×10^-9,最大值为2.33×10^-9,显著高于国内外其他背景站点（（0.21~0.44）×10^-9）,且PAN的夜间浓度一直维持在较高的水平;PAN和O₃（r=0.90）、NO₂（r=0.87）的相关性较强,通过PAN和O₃的线性拟合估算出O₃的大气背景体积浓度为（46.22±0.65）×10^-9,表明南岭光化学反应十分活跃;受区域光化学污染事件的影响,国庆期间南岭PAN的浓度显著升高,达到（1.18±0.45）×10^-9,而同期NO/NO₂比值降低,导致PAN大气寿命延长,有利于PAN的本地累积;结合气团后向轨迹,潜在源贡献分布以及前体物NO₂的全国分布特征分析,发现国庆期间高浓度PAN主要来自湖南,湖北、河南、江西等华中地区.     

乌江流域表层水体中汞的形态与时空分布特征

为了弄清乌江流域表层水体中汞的形态与时空分布规律,于2009年1~12月,每月采集乌江流域河流表层水样,采用两次金汞齐-冷原子荧光光谱法和蒸馏-乙基化结合GC-CVAFS法测定了水中不同形态汞的浓度。结果表明:(1)监测期间各采样点总汞、甲基汞、溶解态汞、颗粒态汞、活性汞、颗粒态甲基汞、溶解态甲基汞的年均算数平均值分别为5.20±10.89、0.09±0.20、3.31±10.66、1.89±1.08、0.30±0.36、0.06±0.19、0.04±0.03 ng/L。不同形态汞的沿程分布显示,水库的修建改变了原有的汞的地球化学过程。(2)通过不同季节各形态汞浓度的变化发现,河流表层水中不同形态汞有明显的季节变化趋势。(3)相关分析发现,总汞受总悬浮颗粒物含量的影响相对较大;活性汞浓度的季节变化可能与降雨对乌江水体的影响有关。     

Precision of the radiochemical OH measurement method

Twenty-eight radiochemical ¹⁴C tracer measurement of tropospheric hydroxyl radical (OH) concentrations were obtained at a rural site near Washington State University, Pullman, WA (117°W, 47°N). Diurnal OH concentration variations were observed for the five days between 9 August and 14 August 1990. These data made it possible to estimate the midday precision and detection limit of the radiochemical OH measurement method. Experiments performed at a peak O₃ photolysis rate J (O(¹D)) of (3.0±0.2) × 10⁻⁵ s⁻¹ yielded a mean midday OH concentration of (5.6±0.1 (1σ)) × 10⁶ cm⁻³. Other data put an upper bound of 16% on fluctuations of instrument sensitivity. Low-light or nighttime background OH concentrations were less than (2.6±2) × 10⁵ cm⁻³. A lower detection limit of 10⁵ cm⁻³ was obtained when extra care was taken with the low-level ¹⁴C counting procedure.     

持续性降水气象条件下土壤/大气间汞通量特征

为研究自然条件下地表大气间汞交换通量特征及其影响因素,2012年4月22~25日在位于松花江上游的夹皮沟金矿,使用动态通量箱法(dynamic flux chamber, DFC)与汞分析仪(LUMEX Zeeman RA915+)联用技术测定了在持续性降雨气象条件控制下矿区土壤大气间汞交换通量,同步测定了近地面垂向0~150cm范围内大气汞浓度以及太阳辐射强度和大气温湿度,并分析了汞交换通量与降水条件下气象因子间相关关系.结果表明:在持续性降雨条件控制下,地表大气间的汞交换通量表现为沉降与释放过程连续交替出现特征,这与晴朗天气条件下日型汞通量单峰结构明显不同.降水间歇期土壤大气间汞交换通量在坡耕农田采样点依次为(-2.08±6.11)、(-6.16±33.57)、(-3.20±8.64)和(5.06±18.80)ng/(m2·h);在谷底漫滩采样点依次为(-5.21±6.42)、(3.87±28.12)、(-11.87±14.10)和(-9.44±12.23)ng/(m2·h).在局地范围内,地形条件差异影响不同地表和近地面大气系统能量收支,并使近地面大气汞浓度和气象因子发生变化,进而影响地表大气间汞交换通量过程和水平.持续性降水条件下,地表和大气间汞交换通量与太阳辐射强度和大气湿度间具有较为明显的正线性相关关系,与大气汞浓度和大气温度间无明显线性相关关系.     

毛细管GC-ECD测定环境样品中的PCBs

建立了毛细管柱ＧＣ－ＥＣＤ测定海洋环境样品中的ＰＣＢｓ的分析方法,给出了ＰＣＢｓ和ＯＣＰｓ的Ｆｌｏｒｉｓｉｌ柱层析的分离方式以及回收率,测定了国际互校样品和我国海洋环境样品中的ＰＣＢｓ。结果表明,本方法可用于海洋环境样品中ＰＣＢｓ的分析。     

Sulfur dioxide,hydrogen sulfide,total reduced sulfur,chlorinated hydrocarbons and photochemical oxidants in southern California museums

Indoor and outdoor concentrations of the air pollutants ozone, NO₂, SO₂, H₂S, total reduced sulfur (TRS), peroxyacetyl nitrate (PAN), methyl chloroform and tetrachloroethylene, have been measured at three southern California museums. Indoor maxima were 175 ppb for NO₂, 77 ppb for O₃, 0.7 ppb for PAN, 1.2 ppb for C₂Cl₄, >6.3 ppb for CH₃CCl₃, 2.5 ppb for SO₂, 1.4 ppb for TRS, and 46 ppt for H₂S. Indoor levels and indoor/outdoor (I/O) ratios for the chlorinated hydrocarbons pointed out to indoor sources. Outdoor and indoor levels of SO₂ and TRS were low at all three museums, but I/O ratios for SO₂ were high and averaged 0.89. H₂S concentrations were low, 16–46 ppt at one museum and less than 6 ppt at the other two museums. I/O ratios for the air pollutants with outdoor sources (ozone, PAN and NO₂) showed substantial variations, from low values of 0.02–0.33 at locations without influx of outdoor air to high values of 0.85–0.88 at locations experiencing high influx of outdoor air. Of the 10 institutions we have surveyed in southern California to date, eight exhibit high I/O ratios, e.g. 0.60–1.00 for PAN. Of the four museums surveyed that were equipped with HVAC and chemical filtration, only two yielded the expected low I/O ratios.     

NitroMAC: An instrument for the measurement of HONO and intercomparison with a long-path absorption photometer

NitroMAC (French acronym for continuous atmospheric measurements of nitrogenous compounds) is an instrument which has been developed for the semi-continuous measurement of atmospheric nitrous acid (HONO). This instrument relies on wet chemical sampling and detection using high performance liquid chromatography (HPLC)-visible absorption at 540 nm. Sampling proceeds by dissolution of gaseous HONO in a phosphate buffer solution followed by derivatization with sulfanilamide/N-(1-naphthyl)-ethylenediamine. The performance of this instrument was found to be as follows: a detection limit of around 3 ppt with measurement uncertainty of 10% over an analysis time of 10 min. Intercomparison was made between the instrument and a long-path absorption photometer (LOPAP) during two experiments in different environments. First, air was sampled in a smog chamber with concentrations up to 18 ppb of nitrous acid. NitroMAC and LOPAP measurements showed very good agreement. Then, in a second experiment, ambient air with HONO concentrations below 250 ppt was sampled. While NitroMAC showed its capability of measuring HONO in moderate and highly polluted environments, the intercomparison results in ambient air highlighted that corrections must be made for minor interferences when low concentrations are measured.     

徐州市环境空气TSP中多环芳烃的分布

报告了徐州市区秋季环境空气中TSP上多环芳烃的分布状况.索氏提取样品,GC/MS测定出TSP上吸附着14种多环芳烃.其中4苯环数的NFDA1、苯并(b)荧蒽含量有明显优先;3个监测点中有2个测点的苯并(a)芘超标,超标倍数在01～22倍之间;监测点苯并(a)芘质量浓度与多环芳烃质量浓度、多环芳烃质量浓度与总悬浮微粒质量浓度之间成线性关系.      

天津夏季边界层低层大气中PAN和O3的输送特征分析

采用在线仪器监测分析2017年夏季天津气象铁塔220 m观测平台大气中过氧乙酰硝酸酯(PAN)和O_3的体积分数,并结合气象观测资料和后向轨迹分析PAN和O_3的输送特征.观测期间PAN和O_3体积分数平均值分别为(0.73±0.56)×10~(-9)和(53±25)×10~(-9),最大小时体积分数分别为3.49×10~(-9)和137×10~(-9),PAN和O_3体积分数具有相似的日变化特征,白昼PAN和O_3浓度高于夜间,且PAN和O_3浓度相关系数(R2=0.52)显著高于夜间(R2=0.21).观测期间偏南风下PAN和O_3浓度最高,偏东风下最低,风玫瑰图和后向轨迹聚类分析都表明,来源于西南方向的气流轨迹对应的污染物浓度最高,途经渤海和河北、辽宁沿海地区的偏东气流对应的PAN和O_3体积分数最低,边界层内输送对PAN和O_3的体积分数分布起到了重要作用.     

Determinations of methyl iodide in the Antarctic atmosphere and the south polar sea

Methyl iodide (CH₃I) concentrations were determined in the atmosphere and in surface sea water near the Antarctic Peninsula with a GC/ECD system during October–December 1987. The mean air concentration of methyl iodide was 2.4 pptv with a corresponding seawater concentration of 2.6 ng l⁻¹. In addition chloroiodomethane (CH₂ClI) was detected in some of the seawater samples as a second volatile organoiodine species. No relationship between methyl iodide and biogenic brominated methanes was found. From this it follows that methyl iodide has a different pathway of biogenic production in marine organisms than the brominated methanes. Based on a two-phase model a global sea-to-air flux for methyl iodide of 8 × 10¹¹ g yr⁻¹ was calculated. This is important for the balance of the global biogeochemical iodine cycle assuming that methyl iodide is by far the dominant volatile organoiodine species in the environment.     

Southern California air quality study: Peroxyacetyl nitrate

Information on the spatial and seasonal variations of ambient peroxyacetyl nitrate (PAN) has been obtained from simulataneous measurements made at five, seven or nine Southern California locations in June-September and November-December, 1987. Summertime (smog season) levels of PAN were consistent with photochemical formation during transport, and increased substantially from coastal to inland locations. Daily maxima (up to 30 ppb) coincided with those of ozone at all locations and shifted from midday at coastal sites to late afternoon inland.Elevated levels of PAN, e.g. up to 19 ppb on 3 December 1987, were observed during the fall at all coastal and central locations, where they consistently exceeded summertime levels.