直接电流法测定酚

本文提出了一种测定酚的新方法——直接电流法。用金电极为工作电极,银-氯化银电极为对电极(也是参考电极)。在0.075M Na_2B_4O_7和0.14M KCl溶液中,外加恒定电压650mV时,酚在金电极上发生氧化反应所产生的电流与溶液中酚的含量成正比。 此法简易、快速、可以测定ppm—ppb数量级的酚。用此法测定了焦化废水中的总酚,结果较为满意。     

五氯酚对牛血清白蛋白的荧光猝灭作用

用荧光光谱和紫外吸收光谱法研究了五氯酚对牛血清白蛋白(BSA)的荧光猝灭作用.结果表明,五氯酚可以有规律地使BSA内源荧光猝灭,其猝灭机理可认为是五氯酚与BSA形成复合物的静态猝灭;并获得了不同温度下,五氯酚与BSA作用的结合常数和热力学参数.根据所得结果可推断五氯酚与BSA的作用力为疏水作用力和静电作用力.同时由Forster非辐射能量转移理论计算得出了五氯酚与BSA结合位置的距离.     

河流与海洋溶解有机物荧光激发-发射矩阵光谱的测定

通过对河流与海洋现场样品、微藻培养液和牛血清蛋白溶液的实验,确定了HITACHI F-4500型荧光分光光度计的测定河流和海洋溶解有机物荧光激发-发射矩阵光谱的激发和发射通带分别为5 nm和10 nm,波长扫描速度为12 000 nm/min,标准偏差在0.6%~8%。     

液相色谱测定湖泊水中硝酸根的高灵敏度快速分析法

作为湖泊水中微量硝酸根的分析法,本文研究了用离子交换树脂浓缩和紫外吸光法构成的液相色谱法的最佳条件。其结果是:该法精度在用5m150ppb硝志氮溶液行20次重复测定时的标准偏差为0.86％,另外在S/N= 3时的检测极限是0.014ppb。其含量在0～1 ppM和0～100ppb时所得到的检量线浓度和色谱峰高的相关系数为0.999;含量在0～loppbg时,其相关系数为0 .993,因此,不受干扰物质的影响。该法硝志氮的定量下限为1 ppb,测定所花的时间不到10分钟。现以测定日本琵琶湖水中的硝酸根为例,发现该法所测得的数据与铜、镉     

水的分析方法发展述评(续三)

有机物 Chang(11P)发明一种测定水中酚的方法。酚类物质相继被大网孔阴离子交换树脂选择性吸着、丙酮—水洗脱、二氯甲烷萃取和蒸发浓缩后,用气相色谱法测定。对于ppb和ppm水平的苯酚、烷基和氯化酚,该法均能给出准确的结果。这篇文章还谈到一种浓缩和测定饮用水中卤代甲烷的技术,也     

荧光光谱标准加入法快速检测雪碧中的苯甲酸钠

为建立一种快速测定雪碧中苯甲酸钠的方法,探讨了雪碧体系中苯甲酸钠的荧光特性,建立了标准加入法检测雪碧中的苯甲酸钠的方法,并对该方法进行了评价。结果表明:荧光检测最佳的激发波长为265 nm、发射波长为313 nm;100 mL检测体系中,雪碧添加量为10 mL,盐酸浓度0.01 mol/L、表面活性剂浓度0.05 g/L,当加入0～20 mL 0.1 g/L苯甲酸钠溶液时,荧光强度与苯甲酸钠的加入体积有良好的线性关系,工作曲线为y=39.8x+638.3,相关系数为0.9991,检出限为9.07×10~(-5)g/L,变异系数为1.1%。     

邻苯二酚荧光法测定垃圾渗滤液中的金属锰（Ⅱ）

在PH约为2.3条件下,锰（VII）与邻苯二酚发生氧化还原作用,致使邻苯二酚的荧光（λex/λem=278nm/318nm）发生猝灭,且体系的荧光猝灭程度与锰（II）的浓度在一定范围呈现良好的线性关系,基于此可建立测定锰（II）的荧光分析方法。本文详细研究了其反应的特性和影响因素,在优化的试验条件下,测定锰浓度的线性范围是2×10-8mol/L-3×10-4mol/L,检出限为2×10-9mol/L。RSD=1.0%,常见离子不干扰测定。该方法稳定性好,简便易行,快速准确,有很好的选择性和很高的灵敏度,成功应用于垃圾渗滤液样品中锰（Ⅱ）的测定,实验结果令人满意。     

水系沉积物中痕量铈、铅快速同时测定的荧光分析法研究

在研究氯化钾介质中铈(Ⅲ)、铅(Ⅱ)的荧光性质基础上,提出了快速测定铈、铅的荧光分析法。在实验条件下,用262．5nm紫外光激发,以120nm／min扫描300～520nm的发射光谱。其在352．4nm处峰高与2．0×10－8～2．0×10－6mol／LCe3－,在485．0nm处峰高与4．0×10－7～1．0×10－5mol／LPb2－,存在线性关系。该法用于标准水系沉积物分析,结果与标准值无显著性差异。Ce￣(3＋)和Pb￣(2＋)的检出限分别为1．5×10－8和2．0×10－7mol／L。      

荧光猝灭法研究洛克沙胂与腐殖酸的相互作用

运用荧光光谱和荧光猝灭滴定方法,研究腐殖酸(HA)与洛克沙胂(ROX)之间的相互作用,考察了HA浓度、pH和温度对ROX与HA之间相互作用强度的影响.结果表明,HA中的4个峰(Ex/Em=300 nm/480 nm、370 nm/480 nm、420 nm/500nm、460 nm/520 nm,分别标记为A、B、C、D)与ROX发生了不同程度的猝灭作用,猝灭程度依次为C>B>A>D.随着HA浓度增加,ROX与峰A所代表官能团结合常数的常用对数值lg K有略微上升,且远大于O2双分子动态猝灭常数的lg K值,表明ROX能与HA中羧基和羰基等官能团发生静态猝灭作用;在pH值5.00~9.00范围内,ROX-HA体系中峰A的lg K在3.55~3.98 L·mol-1之间波动,且在pH=6.00时达到最大值,这可能是由于pH改变了ROX形态以及HA分子中酚羟基和羧基的构象所致;在25.0~55.0℃范围内,随着温度上升,lg K值降低,lg K值介于2.65~3.89 L·mol-1之间,这进一步表明ROX与HA中的类FA荧光峰所代表的官能团发生静态猝灭.瞬态荧光光谱和线性模型拟合分析表明:ROX与HA中峰A、峰B、峰D所代表的官能团均发生单一静态猝灭作用,而与峰C所代表的官能团同时发生静态猝灭和碰撞猝灭作用.     

环境水中酚的荧光法测定

酚的分析方法主要有比色法、气相色谱法、紫外分光光度法及荧光法。尽管4-氨基安替比林比色法(4-AAP法)被日本 JIS 和美国水标准分析法所采用,但该方法不能测定对位是烷基、芳基、硝基、苯酰基、亚硝基或醛基的酚类,对甲酚是典型的例子。荧光法的灵敏度高,适用于浓度为微克每升级的水中酚的直接测定。然而,荧光法的应用,关键是避免水的Raman 光谱对低含量酚测定的严重干扰。对此,可采用醋酸丁酯提取浓缩水中的酚。本方法则利用了校正荧光光谱技术。水样通过蒸馏去除干扰,经酸化后用校正荧光光谱直接测定。实验部分一、仪器与试剂日立650—60荧光分光光度计;     

水和废水中酞酸酯的测定

建立了Zorbax-CN柱和含0.1％异丙醇的正己烷为洗脱液,在224nm处紫外检测的液相色谱系统,并应用该系统测试了北京市工业废水、地面水、地下水和饮用水中的酞酸酯。水样经正己烷萃取后,不需净化（如柱层析）即可直接进入液相色谱系统进行分析。方法检出限：酞酸二甲酯1.0ng;酞酸二乙酯0.4ng;酞酸二正丁酯、酞酸二正辛酯和酞酸－双-（2-乙基己基）酯为0.2ng。定量分析的线性范围为0.1～450ppb,回收率为70～110％,5～7次平行测试的变异系数在10％以内。     

高效液相色谱法测定水中微量酚

本文报道了水中11种微量酚的高效液相色谱测定方法。用氯化四丁基按作为阳离子对萃取剂。二氯甲烷章取水中微量酚，除本酚外，水中10种微量酚的回收率大于90％。用MicropakMCH－5色谱柱，醋酸—水—乙睛流动相，uv254um和280um双波长检测，流速1ml／min下，对水中11种微量酚进行了分离和定量、11种酚的检测极限是0.1mg／L～1.26mg／L；检测范围为0.1mg／L～7mg／L。对2—甲基—4，6—二硝基酚的峰高与浓度进行了线性回归，γ＝0.9993；该法适用于水中11种微量酚的同时测定。     

4-AAP光度法测定污水中挥发酚的干扰规律研究及其应用

矿物油(原油、机油、柴油等)、苯胺、部分金属离子及ClO^-等物质对4-AAP法测定污水中的挥发酚有干扰。本文采用标加干扰物的方法研究了各种干扰物质对挥发酚测定过程中的回收率的影响规律,得到总回收率Y方程。由Y值和4-AAP法测定值C_D可求得水样中挥发酚的实际含量C_T(C_D/Y)。混和干扰物加标拟合实验结果的相对误差<±5%。该方法测定实际水样的结果与4阶导数光谱法的结果基本吻合。本文是针对油矿区污水特点,提出的消除各种干扰挥发酚测定物质影响的研究方法。     

Apparent deposition velocity and compensation point of ammonia inferred from gradient measurements above and through alfalfa

Understanding the cycling of ammonia between croplands and the atmosphere is of importance to agriculturalists and atmospheric scientists. Flux densities of gaseous ammonia (NH₃), particulate ammonium (NH₄⁺), and total ammoniacal nitrogen (AN) were measured using an aerodynamic method above an alfalfa (Medicago sativa, L.) canopy between April and July 1981 at a rural location in central New York State. In air not influenced by local sources, NH₃ and NH₄⁺ averaged 1.5 and 3.0 ppb, respectively, at 1 m above the crop. Ambient NH₄⁺ varied consistently with synoptic air masses, being lowest (2.3 ppb) for NW and highest (6.4 ppb) for SW flows. Concentrations and gradients of both species were higher during periods of hay harvest. Gradients of NH₃ were much steeper than those of NH₄⁺ within the alfalfa canopy, but NH₄⁺ contributed appreciably (36% on average) to above-canopy AN gradients. Alfalfa's NH₃ compensation point was estimated by combining concentration and gradient data with transport resistances. Gaseous gradients indicated a compensation point of 2 ppb, lower than previously published estimates. Conversion of NH₃ to NH₄⁺ within the canopy air could have reduced NH₃ gradients and caused a low estimate of the compensation point. Acidic aerosols, by keeping NH₃ levels low, may compete with plants for NH₃. Future studies of ammonia exchange should distinguish between NH₃ and NH₄⁺ if flux densities are to be related to ambient conditions. Total AN level is a poor predictor of soil-plant-atmosphere ammonia exchange since high AN was frequently associated with low NH₃, and NH₃ is more surface reactive than NH₄⁺.     

Characteristics and recent trends of sulfur dioxide at urban, rural, and background sites in North China: Effectiveness of control measures

SO₂ measurements made in recent years at sites in Beijing and its surrounding areas are performed to study the variations and trends of surface SO₂ at different types of sites in Northern China. The overall average concentrations of SO₂ are (16.8 ± 13.1) ppb, (14.8 ± 9.4) ppb, and (7.5 ± 4.0) ppb at China Meteorological Administration (CMA, Beijing urban area), Gucheng (GCH, relatively polluted rural area, 110 km to the southwest of Beijing urban area), and Shangdianzi (SDZ, clean background area, 100 km to the northeast of Beijing urban area), respectively. The SO₂ levels in winter (heating season) are 4-6 folds higher than those in summer. There are highly significant correlations among the daily means of SO₂ at different sites, indicating regional characteristics of SO₂ pollution. Diurnal patterns of surface SO₂ at all sites have a common feature with a daytime peak, which is probably caused by the downward mixing and/or the advection transport of SO₂-richer air over the North China Plain. The concentrations of SO₂ at CMA and GCH show highly significant downward trends (-4.4 ppb/yr for CMA and -2.4 ppb/yr for GCH), while a less significant trend (-0.3 ppb/yr) is identified in the data from SDZ, reflecting the character of SDZ as a regional atmospheric background site in North China. The SO₂ concentrations of all three sites show a significant decrease from period before to after the control measures for the 2008 Olympic Games, suggesting that the SO₂ pollution control has long-term effectiveness and benefits. In the post-Olympics period, the mean concentrations of SO₂ at CMA, GCH, and SDZ are (14.3 ± 11.0) ppb, (12.1 ± 7.7) ppb, and (7.5 ± 4.0) ppb, respectively, with reductions of 26%, 36%, and 13%, respectively, compared to the levels before. Detailed analysis shows that the differences of temperature, relative humidity, wind speed, and wind direction were not the dominant factors for the significant differences of SO₂ between the pre-Olympics and post-Olympics periods. By extracting the data being more representative of local or regional characteristics, a reduction of up to 40% for SO₂ in polluted areas and a reduction of 20% for regional SO₂ are obtained for the effect of control measures implemented for the Olympic Games.     

A passive sampler for airborne formaldehyde

A simple, inexpensive passive sampler is described that is capable of reliable measurements of formaldehyde at the parts per billion (ppb) levels relevant to indoor and outdoor air quality. The passive sampler consists of a modified dual filter holder in which the upper stage serves as the diffusion barrier, the lower stage includes a 2,4-dinitrophenylhydrazine (DNPH)-coated filter which collects formaldehyde, and the space between the two stages serve as the diffusion gap. The measured sampling rate, 18.8 ± 1.8 ml min⁻¹, was determined in experiments involving sampling of ppb levels of formaldehyde with the passive sampler and with DNPH-coated C₁₈ cartridges and agrees well with the value of 19.4 ± 2.0 ml min⁻¹ calculated from theory. The measured sampling rate was independent of formaldehyde concentration (16–156 ppb) and sampling duration (1.5–72 h). The precision of the measurements for colocated passive samplers averaged 8.6% in purified and indoor air (office and museums) and 10.2% in photochemically polluted outdoor air. With a 1.2-μm pore size Teflon filter as the diffusion barrier, the detection limit is 32 ppb h, e.g. 4 ppb in an 8-h sample, 1.3 ppb in a 24-h sample, and so on. Perceived advantages and limitations of the sampler are discussed including flexibility, cost effectiveness and possible negative bias at high ambient levels of ozone.     

Hydrochloric acid: A regional perspective on concentrations and formation in the atmosphere of Southern California

Atmospheric gaseous hydrochloric acid (HCl) concentrations and water-soluble species in the aerosol phase were measured at nine sites in Southern California throughout the year 1986. Annual average HCl concentrations measured by the denuder difference method ranged from 0.39 ppb at an offshore island to 1.25 ppb onshore at Hawthorne, California. An ion balance on the aerosol shows that coarse particle chloride begins as sea salt over the ocean and is depleted relative to aerosol sodium with transport inland. Total chloride and sodium balances show that chloride depletion from the aerosol is matched by a comparable increase in gaseous HCl concentrations, consistent with the proposition that acid gas reactions with sea salt are the principal source of gaseous HCl in the Southern California atmosphere. Fine aerosol chloride exceeds fine particle sodium on a number of occasions, particularly at one inland site known for extraordinarily high NH₃ levels. There is evidence that coarse aerosol chloride from sea salt is being processed by atmospheric reactions through HCl to form fine aerosol, possibly NH₄Cl.     

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.     

Ozone concentrations at a remote mountain site and at two regional locations in southwestern Alberta

Ozone concentrations at a remote site in the Rocky Mountains of southwestern Alberta averaged 43.4 ppb over a 2 year period and the Canadian air quality objective of an 80 ppb hourly average was exceeded 1.5% of the time. The diurnal variation in O₃ concentrations was small, 2.9 ppb, indicative of a remote location, above the nocturnal inversion and not greatly influenced by local emissions. During the period when O₃ concentrations were highest, winds were generally from the southwest, suggestive of the long range transport of anthropogenic pollutants from distant sources rather than the generation of O₃ from local emissions. In contrast, hourly O₃ concentrations at two regional air quality monitoring sites showed an average diurnal variation of 14 ppb. Only two hourly averages exceeded 80 ppb during the 2 years, and the mean O₃ concentration was 26 ppb. When these regional sites were within the urban plume from Calgary, the O₃ concentrations were depressed to a mean of 18 ppb. Ozone concentrations in downtown Calgary averaged 13 ppb. Under Alberta climatological and meteorological conditions, hourly O₃ objectives are most likely to be exceeded in remote areas, rather than in cities or in areas under the direct influence of urban emissions.     

Carbonyl compounds in dining areas, kitchens and exhaust streams in restaurants with varying cooking methods in Kaohsiung, Taiwan

Eighteen carbonyl species in C₁–C₁₀ were measured in the dining areas, kitchens and exhaust streams of six different restaurant types in Kaohsiung, southern Taiwan. Measured results in the dining areas show that Japanese barbecue (45.06 ppb) had the highest total carbonyl concentrations (sum of 18 compounds), followed by Chinese hotpot (38.21 ppb), Chinese stir-frying (8.99 ppb), Western fast-food (8.22 ppb), Chinese–Western mixed style (7.38 ppb), and Chinese buffet (3.08 ppb), due to their different arrangements for dining and cooking spaces and different cooking methods. On average, low carbon-containing species (C₁–C₄), e.g., formaldehyde, acetaldehyde, acetone and butyraldehyde were dominant and contributed 55.01%–94.52% of total carbonyls in the dining areas of all restaurants. Meanwhile, Chinese–Western mixed restaurants (45.48 ppb) had high total carbonyl concentrations in kitchens mainly because of its small kitchen and poor ventilation. However, high carbon-containing species (C₅–C₁₀) such as hexaldehyde, heptaldehyde and nonanaldehyde (16.62%–77.00% of total carbonyls) contributed comparatively with low carbon-containing compounds (23.01%–83.39% of total carbonyls) in kitchens. Furthermore, Chinese stir-frying (132.10 ppb), Japanese barbecue (125.62 ppb), Western fast-food (122.67 ppb), and Chinese buffet (119.96 ppb) were the four restaurant types with the highest total carbonyl concentrations in exhaust streams, indicating that stir-frying and grilling are inclined to produce polluted gases. Health risk assessments indicate that Chinese hotpot and Japanese barbecue exceeded the limits of cancer risk (10^− 6) and hazard index (= 1), mainly due to high concentrations of formaldehyde. The other four restaurants were below both limits.