Modeling toxic compounds from nitric oxide emission measurements

Determining the amount and rate of degradation of toxic pollutants in soil and groundwater is difficult and often requires invasive techniques, such as deploying extensive monitoring well networks. Even with these networks, degradation rates across entire systems cannot readily be extrapolated from the samples. When organic compounds are degraded by microbes, especially nitrifying bacteria, oxides or nitrogen (NO_x) are released to the atmosphere. Thus, the flux of nitric oxide (NO) from the soil to the lower troposphere can be used to predict the rate at which organic compounds are degraded. By characterizing and applying biogenic and anthropogenic processes in soils the rates of degradation of organic compounds. Toluene was selected as a representative of toxic aromatic compounds, since it is inherently toxic, it is a substituted benzene compound and is listed as a hazardous air pollutant under Section 12 of the Clean Air Act Amendments of 1990. Measured toluene concentrations in soil, microbial population growth and NO fluxes in chamber studies were used to develop and parameterize a numerical model based on carbon and nitrogen cycling. These measurements, in turn, were used as indicators of bioremediation of air toxic (i.e. toluene) concentrations. The model found that chemical concentration, soil microbial abundance, and NO production can be directly related to the experimental results (significant at P < 0.01) for all toluene concentrations tested. This indicates that the model may prove useful in monitoring and predicting the fate of toxic aromatic contaminants in a complex soil system. It may also be useful in predicting the release of ozone precursors, such as changes in reservoirs of hydrocarbons and oxides of nitrogen. As such, the model may be a tool for decision makers in ozone non-attainment areas.     

Sorption of heterocyclic compounds from a complex mixture of coal-tar compounds on natural clayey till

The sorption and desorption of heterocyclic organic compounds in a complex multisolute system to a natural clayey till was investigated. The composition of the solutes reflect a simplified composition of an aqueous phase in contact with coal tar. Sorption was studied for two ratios (s:l) of clayey till (solid) to aqueous phase (liquid). The effect of the complex mixture of solutes on sorption of the four heterocyclic compounds: benzofuran, dibenzofuran, benzothiophene, and dibenzothiophene is evaluated by comparison with their sorption measured in single-solute systems. Sorption of the four compounds is affected by the complex mixture, with sorption decreases for all four compounds at high s:l ratio indicating competitive sorption. The effect on sorption of the individual compounds is not related to solubility or hydrophobicity of the compounds. Freundlich-type isotherms are observed for all compounds in the high s:l-ratio experiments, but for the most hydrophobic compounds isotherms are close to linear. The sorption of N-compounds and benzofuran is apparently influenced by cation exchange and dipole–dipole attraction to clay minerals. At high concentrations a dramatic increase in the sorption of the most strongly sorbing compounds is observed in the low s:l-ratio experiment. The dramatic increase in sorption appears to be a result of multimolecular layer sorption or condensation on surfaces in the clayey till at high surface density of organic compounds, and the data are fitted by BET (Brunauer, Emmet, and Teller) type 2 isotherms. The increase may or may not be induced by the presence of N-heterocyclic compounds sorbed by cation exchange and dipole–dipole attraction. The desorption of the compounds was studied for the low s:l ratio where multimolecular layer formation apparently had occurred. Partially irreversible sorption, hysteric Langmuir type desorption with isotherms of very high K_l coefficient, or behaviour reflecting dissolution of a condensed phase is observed.     

胶合竹材GluBam甲醛释放影响因素的气候箱实验与分析

胶合竹材GluBam的甲醛释放情况是现代竹结构住宅环保性的一个重要方面,也是竹结构住宅推广中最受关注的指标之一。采用1 m3气候箱对温度、相对湿度和封边情况与GluBam的甲醛释放量和释放速率的相关关系进行了测试,并以一阶单衰减模型为基础提出了GluBam的甲醛释放分析模型。测试和分析结果表明:GluBam板材在各模拟条件下甲醛浓度峰值均小于规范要求;初始甲醛释放量E0和衰减率常数k可以用来评价GluBam的甲醛释放特征;GluBam的醛释放量和释放速率随环境温度和湿度增加而显著增大,且温度因素的影响更大;封边处理可以有效降低GluBam板材的甲醛释放量。     

Effect of dye compounds on the adsorption of atrazine by natural sediment

The overall objective of this research is to investigate competitive adsorption between atrazine (AT) and dye compounds in the natural aquatic sediment. The sorbent was sediment obtained from Guanting Reservoir (Beijing, China), which contained 25% sand, 67% silt, 8% clay, and 2.06% organic carbon. Batch adsorption experiments were conducted at various Ca2+ concentration, pH levels, temperatures, and introducing conditions of dye compounds. Compared with the dye-free system, both of dyes including Congo red (CR) and methylene blue (MB) reduce the adsorption of atrazine over the range of dye concentrations examined, with the adsorption percentage of atrazine decreasing about 14-30%. And the competition between AT and MB is much stronger than that between AT and CR. The adsorption experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (Kf) of the samples; Kf values range from 1.669 micromol/kg for the MB-AT sample up to 3.738 micromol/kg for the AT-alone sample. By contrast with the single-solute adsorption isotherm, both simultaneous adsorption and dye preloading inhibit the adsorption of atrazine. As for AT preloading, the impacts of CR and MB are different on the desorption of atrazine. As compared to the atrazine desorption without dye compounds, a certain amounts of atrazine molecules are replaced by MB in AT preloading system, while in CR solution AT is adsorbed strongly on the sediment and could not be replaced by CR. The result suggests that micropore constriction by CR reduces the desorption rate of atrazine.     

Influence of temperature on formaldehyde emission parameters of dry building materials

The diffusion coefficient, D, partition coefficient, K, and the initial volatile organic compounds (VOCs) in dry building materials, are the three key parameters used to predict the VOC emissions. D and K may be strongly affected by temperature. We have developed a new and simple method, the C-history method, to measure the diffusion coefficient, D and the partition coefficient, K of formaldehyde in dry building materials at temperatures of 18, 30, 40 and 50 °C. The measured variations of the diffusion coefficients and the partition coefficients with temperature for particle board, vinyl floor, medium- and high-density board are presented. A formula relating the partition coefficient and related factors is obtained through analysis. This formula can predict the partition coefficient in principle and provide an insight for fitting experimental data, and it agrees well with the experimental results.     

Investigation of carbonyl compounds in air from various industrial emission sources

The emission concentrations of carbonyl compounds in air were quantified from a total of 195 man-made source units within 77 individual companies at a large industrial complex in Korea. The measurement data were evaluated both by absolute magnitude of concentration and by their relative contribution to malodor formation such as malodor degree (MD) derived from empirical formula. It was found that formaldehyde exhibited the highest mean concentration of 323ppb with a median value of 28.2ppb, while butyraldehyde recorded the highest contribution to odor formation with an MD value of 3.5 (186 (mean) and 9.8ppb (median)). The relative intensity of carbonyl emission, when compared by the sum of MD, showed the highest source strength from the food and beverage (industry sector) and scrubber (source unit). A comprehensive evaluation of the carbonyl data from diverse industrial facilities thus allowed us to describe the fundamental patterns of their emission.     

造纸黑液木质素用于制备人造板胶粘剂的研究

分别采用硫酸、硝酸和盐酸从造纸黑液中提取木质素,以此替代部分苯酚.制备改性人造板用酚醛树脂胶粘剂,并测定其固体含量、动力黏度(40℃)、游离甲醛含量和胶合强度等性能;考察了3种酸析木质素掺入量、催化剂(氧氧化钠)加入量和苯酚与甲醛摩尔比(简称酚醛比)对木质素酚醛树脂胶粘剂性能的影响.结果表明,当硫酸、硝酸木质素掺入量为苯酚用量的20%(质量分数,下同)时,获得的胶粘剂性能较好;以硝酸木质素掺入量为苯酚用量的20%为例,当氢氧化钠加入量为苯酚用量的0.6%(质量分数)、酚醛比为1.0:1.5时.制备的硝酸木质素酚醛树脂胶粘剂胶合性能较好.用木质素替代部分苯酚,不仅可以降低产品成本,而且减少了苯酚的用量,更环保.     

餐厨垃圾处理厂挥发性有机物释放特征

选择目前国内成功运营的餐厨垃圾处理厂为采样点,该厂以利用餐厨垃圾生产生物蛋白饲料和厌氧发酵为主要工艺,采用气相色谱/质谱联用(GC/MS)技术对挥发性有机物(VOCs)浓度较高的工段,如破碎室、湿热反应器、好氧发酵仓进行了定性和定量分析.结果表明,3个采样点共检测出65种物质,包括醇、醛、酮、酯、芳香烃、硫化物、卤代物、烯烃和烷烃9类.湿热反应器排放VOCs浓度最高且包含物质种类最多,其中酮、酯、芳香烃、硫化物、卤代物、烯烃及烷烃类物质浓度均高于其他检测点,需对该工段进行重点监测和控制.     

纳米氧化铈对汽油发动机尾气污染物排放的影响

通过非水微乳液法制备了纳米氧化铈,并将之添加到90^#汽油中,研究了纳米氧化铈对汽油动力性能、尾气污染物CO、HC、PM、NOx排放的影响。结果表明：非水微乳液法制备的纳米氧化铈粒径在30～50nm之间,粒径分布较窄;添加浓度为100mg／L时,不会对汽油的动力性能产生明显影响,但可以明显降低90。汽油尾气中的CO、HC、PM、NOx排放。其中,800r／min的正常怠速下可以降低CO排放19．39％、HE排放19．92％、NOx排放51．19％、PM排放25％;在2000r／min的高怠速下可降低CO排放16．17％、NOx排放46．92％、PM排放16．67％。     

The natural production of organobromine compounds

Organobromine chemicals are produced naturally by an array of biological and other chemical processes in our environment. Some of these compounds are identical to man-made organobromine compounds, such as methyl bromide, bromoform, and bromophenols, but many others are entirely new moleclar entities, often possessing extraordinary and important biological properties. Although only a few natural organobromine compounds had been discovered up to 1968, this number as of early 1999 is more than 1,600, and new examples are being discovered continually. Organobromine compounds are produced naturally by marine creatures (sponges, corals, sea slugs, tunicates, sea fans) and seaweed, plants, fungi, lichen, algae, bacteria, microbes, and some mammals. Many of these organobromine compounds are used in chemical defense, to facilitate food gathering, or as hormones.     

脱硫设施对2种燃煤锅炉排放VOCs的影响

利用GC-MS,对我国7家典型燃煤电厂和2家焦化厂燃煤锅炉在脱硫工艺设施前后排放烟气中的VOCs进行了分析,并计算了燃煤电厂锅炉的排放因子和VOCs的排放量。2种锅炉在脱硫后VOCs的浓度分别为85~1 374 μg·m⁻³和27~45 μg·m⁻³。脱硫设施对VOCs的排放影响受多种因素影响,包括脱硫设施的种类、VOCs的性质、脱硫浆液等。通过计算得到各企业的臭氧生成潜势值(OFP),为17~2 640 μg·m⁻³,其中苯系物对臭氧生成的贡献最大。计算得到燃煤电厂的排放因子为2.37 g·GJ⁻¹,每年因火力发电排放的VOCs为4.2×10⁴ t。以上结果可为燃煤电厂的VOCs控制设备和工艺选择提供参考。     

Effect of formaldehyde on Cu(II) removal from synthetic complexed solutions by ion exchange

The effect of formaldehyde (HCHO) on the ion exchange of Cu(II) from an equimolar EDTA (ethylenediaminetetraacetic acid, H(4)L) solution with a strong-base Amberlite IRA-400 resin was studied. Experiments were conducted as a function of the initial concentration of Cu(II) (0.5-10 mM), solution pH (1.0-6.0), HCHO concentration (0-6 vol%), and temperature (15-35 degrees C). It was shown that the amount of exchange of Cu(II), which exists in the form of complexed anions CuL(2-), increased with increasing solution pH and reached a plateau at an equilibrium pH (pH(e)) of 3.5. However, the amount of exchange decreased with increasing HCHO concentration up to 3 vol% but then slightly decreased with a further increase in HCHO concentration. Such effect of added HCHO was determined by the following two factors: the competitive exchange of HCOO(-) anions and the enhanced exchange of Cu(I) in the form of complexed anions CuL(3-). The exchange isotherm obtained at a fixed pH(e) could be well described by the Langmuir equation. The isosteric enthalpy change for the present ion exchange process was also evaluated and discussed.     

城市污水厂主要处理单元恶臭及挥发性有机物的逸散

在污水处理厂的主要处理工艺段设置采样点,采用在线监测仪,检测空气中恶臭及挥发性有机物(VOCs)的浓度,明确主要恶臭物质和排放源,研究恶臭及VOC在不同季节的逸散特征。结果表明,恶臭和VOC的排放主要集中在进水区,浓度与进水水质相关。粗格栅间是主要的恶臭源,其恶臭、TVOC、硫化物和胺类的浓度分别为3 458.54~5 028.03 OU、120~221 mg/m3、253~464 mg/m3和15~36 mg/m3,占各个监测点浓度总量的80.6%、93%、90%和89%。主要的恶臭物质为硫化氢和氨,其浓度对应的臭气强度超过4级。恶臭与VOC的排放呈现季节变化,夏季的浓度明显高于冬季。相关性分析显示,恶臭浓度与TVOC、硫化物、胺类浓度具有明显的相关性。     

Effect of reducing conditions on sludge melting process

The objective of this study was to compare the effects of CO/CO(2) reducing conditions with those of air oxidizing conditions on the pouring temperature of the sludge melting process and the heavy metal leachability of the resultant sludge slag. Synthetic sludge ash composed of SiO(2), CaO and Al(2)O(3), as well as sewage sludge ash generated from a laboratory incinerator was employed. The experimental results indicated that the pouring temperatures are significantly reduced under the reducing conditions of CO/CO(2), or 24 and 77 degrees C lower than under air conditions for synthetic and sludge ash, respectively. The heavy metal leaching tests further indicate lower heavy metal concentrations present in the leachate under the reducing conditions, notably an order of magnitude lower in Zn. However, X-ray diffractogram indicates similar peaks for these two slags produced under different conditions.     

Effect of SME biodiesel blends on PM2.5 emission from a heavy-duty engine

To explore the effect of biodiesel and sulfur content on PM_2.5 emissions, engine dynamometer tests were performed on a Euro II engine to compare the PM_2.5 emissions from four fuels: two petroleum diesel fuels with sulfur contents of 50 and 100 ppm respectively, and two B20 fuels in which soy methyl ester (SME) biodiesel was added to each of the above mentioned petroleum diesel fuels (v/v: 80%/20% for petroleum diesel and SME respectively). Gaseous pollutants and PM_2.5 emissions were sampled with an AVL AMA4000 and Model 130 High-Flow Impactor (MSP Corp). Measurements were made of the PM_2.5 mass, organic carbon (OC), elemental carbon (EC) and the water-soluble ion distribution. The results showed that PM_2.5 emissions decreased with lower sulfur content or blending with SME biodiesel, and the decrease would be more by applying both two methods together. Particles of approximately 0.13 μm contributed 48–83% of PM_2.5 emissions. The impact of sulfur content on this percentage was different for low and high engine speed. The majority of PM_2.5 was comprised of OC and EC, and the carbon emission rate had the same trend as PM_2.5. Since the EC abatement of B20 was larger than OC, the OC/EC ratio of B20 was always larger than that of petroleum diesel. For petroleum diesel, the OC/EC increased with sulfur content, which was not the case for B20. The SO₄^2? had highest emission rate in the water-soluble ions of PM.     

Effect of fuel aromatic content on PAH emission from a heavy-duty diesel engine

Polycyclic aromatic hydrocarbons (PAHs) emission tests for a heavy-duty diesel engine fueled with blend base diesel fuel by adding batch fractions of poly-aromatic and mono-aromatic hydrocarbons, Fluorene and Toluene, respectively, were simulated to five steady-state modes by a DC-current dynamometer with fully automatic control system. The main objective of this study is to investigate the effect of total aromatic content and poly-aromatic content in diesel fuels on PAH emission from the HDD engine exhaust under these steady-state modes. The results of this study revealed that adding 3% and 5% (fuel vol%) Fluorene in the diesel fuel increases the amount of total-PAH emission by 2.6 and 5.7 times, respectively and increases the amount of Fluorene emission by 52.9 and 152 times, respectively, than no additives. However, there was no significant variation of PAH emission by adding 10% (vol%) of Toluene. To regulate the content of poly-aromatic content in diesel fuel, in contrast to the total aromatic content, will be more suitable for the management of PAH emission.     

Effect of drying on the desorption of diuron and terbuthylazine from natural soils

This work was initiated to study the effects of climate induced soil water status variations which can reach extreme values under natural conditions on the sorption process of hydrophobic organic compounds. Based on the classical slurry batch methodology an approach is developed that allows the fast and careful complete drying of soil suspensions (microwave technique). Classical adsorption experiments were followed by three desorption steps with and without drying cycles. Drying and re-wetting enhanced the sorption-desorption hysteresis and Freundlich adsorption coefficients increased from 5.9 to 16 and 5.2 to 21 over three drying cycles for diuron and terbuthylazine respectively. Assuming the validity of a dual stage adsorption process, model evaluation suggests that drying is as a shrinking-like process leading to conformational changes of the dominant sorbent (soil organic matter) which restrict the intra-micro-particle diffusion. Rewetting only leads to a partial recovery of the diffusional pore space.     

Effect of hexachlorocyclohexane on metel4ne production and emission from flooded rice soil

Application of commercial formulation (an isomeric mixture) of hmachlorocyelohexane (HCH) to flooded rise fields planted to cv. Ran at 1 kg active ingredient.ha⁻¹ significantly inhibited mute emission. Negative P oxafed between methane emission from HCH-treated fields and root oxidise activity (in tents of -naphthylamine oxidised). Under laboratory condaition, the addition of technical grade -, β-, γ- and δ-isomers (99.1% purity) of HM individually at 20 μg.g⁻¹ soil at flooding, effected a distinct inhibition of methane production. Evidence suggests that the inhibitory effect of all the four isomers on methane production only until 20–25 days after their application was related to their persistence in flooded soil.     

Effect of temperature and humidity on formaldehyde emissions in temporary housing units

The effect of temperature and humidity on formaldehyde emissions from samples collected from temporary housing units (THUs) was studied. The THUs were supplied by the U.S. Federal Emergency Management Administration (FEMA) to families that lost their homes in Louisiana and Mississippi during the Hurricane Katrina and Rita disasters. On the basis of a previous study, four of the composite wood surface materials that dominated contributions to indoor formaldehyde were selected to analyze the effects of temperature and humidity on the emission factors. Humidity equilibration experiments were carried out on two of the samples to determine how long the samples take to equilibrate with the surrounding environmental conditions. Small chamber experiments were then conducted to measure emission factors for the four surface materials at various temperature and humidity conditions. The samples were analyzed for formaldehyde via high-performance liquid chromatography. The experiments showed that increases in temperature or humidity contributed to an increase in emission factors. A linear regression model was built using the natural log of the percent relative humidity (RH) and inverse of temperature (in K) as independent variables and the natural log of emission factors as the dependent variable. The coefficients for the inverse of temperature and log RH with log emission factor were found to be statistically significant for all of the samples at the 95% confidence level. This study should assist in retrospectively estimating indoor formaldehyde exposure of occupants of THUs.     

沈阳市固定燃烧源挥发性有机化合物2007年排放清单研究

挥发性有机化合物(VOCs)与.OH的反应是对流层臭氧形成的重要化学过程,是导致城市光化学烟雾的根本原因。为建立沈阳市固定燃烧源VOCs排放清单,选取了电力热力行业、钢铁行业和秸秆燃烧3个主要排放源进行研究。结果表明:(1)2007年,沈阳市固定燃烧源VOCs排放总量为8 544.539 t,其中排放量最大的是秸秆燃烧,为6 317.115 t;其次是电力热力行业,为2 225.780 t;最小的是钢铁行业,为1.644 t。(2)沈阳市各区县固定燃烧源VOCs排放量由大到小排序依次为新民市、法库县、东陵区、康平县、辽中县、于洪区、苏家屯区、大东区、沈北新区、铁西区、沈河区、皇姑区、和平区;VOCs排放强度由大到小排序依次为大东区、沈河区、铁西区、东陵区、皇姑区、和平区、于洪区、苏家屯区、法库县、康平县、辽中县、沈北新区、新民市。