环境测试舱自吸附甲醛重释放规律与影响因素研究

广泛用于板材污染物释放量测试、空气净化产品净化效果测试等实验中的环境测试舱,往往由于其内壁黏附性杂质而对目标测试物产生不可忽视的自吸附作用,自吸附污染物将作为二次释放源出现重释放,研究目标测试物的自吸附消耗量及重释放规律,探索有效控制措施,有利于对环境测试舱实验应用及室内污染控制提出指导性实际意义。分别选取0.2%甲醛溶液、大芯板作为同一自制玻璃环境测试舱2期实验(I期、Ⅱ期)的不同甲醛释放源,通过近90 d追踪测试,经不同释放源、不同控制条件下舱内壁自吸附甲醛的多次重释放实验,结合非线性拟合分析方法,总结出舱内壁自吸附甲醛重释放甲醛浓度变化符合一阶递增指数函数:y=A1×exp(-x/t1)+y0,(A1<0、t1>0)。曲线参数y0值可用于评价实验条件下测试舱内自吸附甲醛残余量;y0值与环境舱舱体材质、环境温湿度、舱外甲醛浓度及空气交换手段有关,而与释放源及其释放平衡浓度高低无明显关系。大开舱门短时间抽气式空气交换对舱内自吸附甲醛残余有适度清除效果,使y0值降低,同时有利于再次平衡状态的快速建立;而长时间的无动力空气交换,或者自来水洗及去离子水洗等处理手段对舱内壁自吸附甲醛残余无明显清除作用。     

室内甲醛污染治理技术研究

鉴于室内空气甲醛污染的危害,使用市售的"家丁"牌甲醛消除剂,对其去除甲醛性能进行了测试研究.研究结果表明,甲醛消除剂可以快速、有效地消除室内空气中的甲醛,又可以减少室内装修材料中游离甲醛的释放,是治理室内空气甲醛污染的有效手段之一.     

室内甲醛污染治理技术研究

鉴于室内空气甲醛污染的危害，使用市售的“家丁”牌甲醛消除剂，对其去除甲醛性能进行了测试研究。研究结果表明，甲醛消除剂可以快速、有效地消除室内空气中的甲醛，又可以减少室内装修材料中游离甲醛的释放，是治理室内空气甲醛污染的有效手段之一。     

利用cannizzaro反应消除生产中脲醛胶的残余甲醛

在适当条件下,使脲醛胶中剩余甲醛发生歧化反应,即一分子甲醛还原成为甲醇,一分子甲醛氧化成为甲酸,剩余甲醛在加入乙醛的作用下生成季戊四醇,经权威部门检测,所制成的脲醛胶符合GTB18583-2001标准,用该胶制成的人造板强度达标,甲醛释放量符合GB18580-2001中E2标准,并达到环保标志产品HJB2-37-1999人造木质板材标准.     

甲醛清除剂净化效果的实验舱测试和分析

为了对市售被动式室内空气净化产品的净化效果有深刻具体的认识,选择销售份额较大的4种甲醛清除剂进行实验舱测试。结果表明:(1)甲醛清除剂对甲醛的净化过程均随时间呈对数衰减,可见甲醛浓度越高,甲醛清除剂对甲醛的净化速率越快。(2)不同的甲醛清除剂的净化速率都有一定差异,即使24h净化率均在90%以上的甲醛清除剂,净化速率也不同,净化率达到90%以上所需要的实际时间可相差数倍。(3)《室内空气净化功能涂覆材料净化性能》(JCT 1074—2008)中对甲醛清除剂根据其对污染物24h的净化率进行了分级,消费者可据此对净化产品的优劣有初步判断。而净化速率和饱和净化量则可在消费者购买甲醛清除剂时起到更具体和明确的指导作用,并可在消费者具体使用时,根据饱和净化量,对甲醛清除剂用量和甲醛清除剂持续作用时间有初步的判断。     

室内甲醛污染治理实验研究

针对装修所带来的室内甲醛污染危害,采用活性炭、甲醛清除剂来去除室内甲醛,并对其去除效果、影响因素进行了研究。结果表明,在活性炭、甲醛清除剂最佳使用量下,甲醛清除剂的去除率显著高于活性炭去除率,且持久性较好;最佳量的甲醛清除剂在治理不同板材所含的甲醛时,中密度板的甲醛去除率均高于木板、细木工板和装饰单面贴面胶合板的去除率;环境温度升高时,甲醛清除剂其去除效率有所降低。甲醛清除剂对室内甲醛有明显的去除。     

室内有害气体的通风净化效应

室内装修材料和家具释放的有害气体严重恶化了室内空气品质,其中甲醛对人体危害尤为突出,而室内通风是清除甲醛行之有效的办法。测试了室内甲醛释放源的释放强度规律,并建立了新装修室内甲醛通风净化的空气动力学模型,数值计算分析了通风情况下室内甲醛的浓度分布特征。结果表明:(1)室内地板和家具的甲醛释放强度均随测试时间呈指数减小;(2)同一通风风速下,装修后第30天时的甲醛浓度较大区域明显减少;(3)在室内人坐姿和站姿呼吸高度(约1.2、1.7m)处,无论风速大小,装修后通风一段时间后室内甲醛浓度均减小,且较低位置(1.2m)甲醛浓度减小更明显;(4)在同种气流组织形式下,较小和较大的通风风速对室内甲醛通风净化效果均不理想,对本研究模型而言,以通风风速2m/s左右时对室内甲醛净化效果较好。     

四平市二龙湖底泥磷释放研究

采用室内实验模拟法对四平市二龙湖富营养化限制因子磷的底泥释放速率及释放量进行了研究,并研究在种环境因子(温度、pH、DO和扰动因素)影响下底泥磷的释放规律。结果表明,(1)二龙湖年平均底泥释磷量为208·78g,最大释磷率为0·889μg/g(T=20℃,pH=8,DO为4·68mg/L);(2)自然和人为的扰动因素会促进底泥的磷释放;(3)H在弱酸至中性范围内底泥释磷量最小,酸性和碱性条件都有利于磷的释放;(4)随着温度的升高底泥释磷量增大;(5)厌条件比好氧条件更有利于磷的释放。     

新装修居室中大芯板释放甲醛的研究

采用环境舱模拟室内微环境,以大芯板作为研究对象,探讨空气交换率、相对湿度、温度等因素对室内甲醛释放的影响,得出室内甲醛释放规律.研究成果对预测室内甲醛浓度,建立室内甲醛释放模型,以及减少甲醛危害等有重要意义.     

活性污泥对甲醛废水的净化性能

采用微生物法处理低浓度甲醛废水达标排放是比较经济的方法之一.在研究中采用序批式活性污泥法(SBR)工艺,考察了曝气时间、进水甲醛浓度、进水 pH 和水温对微生物净化低浓度甲醛废水的影响.结果表明,随着曝气时间的延长,活性污泥对甲醛的去除率增大.进水甲醛浓度在 40～120 mg/L 范围内,随着浓度升高甲醛污泥负荷增加,微生物对甲醛的降解速率增加,但对甲醛的去除率降低.活性污泥在 pH 为 5～7 的中性和弱酸性环境中对甲醛的降解速率较高.在15～35℃范围内,污泥对废水中甲醛的去除率随温度升高而上升,微生物对甲醛的降解速率随温度升高呈指数递增趋势.     

Disinfection performance of chlorine dioxide gas at ultra-low concentrations and the decay rules under different environmental factors

ABSTRACT

Gaseous chlorine dioxide (ClO₂) is one of the most promising air disinfectants. In this study, an ultra-low concentration of ClO₂ gas (< 1.2 mg/m³) was generated in an office at various levels of humidity and illuminance to investigate the decay law. The disinfection efficiency and metal corrosiveness of ultra-low concentrations of ClO₂ gas were also studied using an experimental chamber. At 48% and 75% humidity, the decay rate constants of ClO₂ gas were 0.0034 min^?1 and 0.0036 min^?1, respectively. The rate of decline of the ClO₂ concentration increased as the humidity of the environment increased. The decay rate constant of ClO₂ gas at an illuminance of 76 lux and 3429 lux was 0.0034 min^?1 and 0.00427 min^?1, respectively; hence, the decay rate increased with increased illumination. At a humidity of 72% and illuminance of 2112 lux, the decay rate constant reached 0.00880 min^?1. The effects of humidity and illuminance on the attenuation of the ClO₂ concentration were strongly synergistic. When the gas concentration was maintained below 0.9 mg/m³, the disinfection rate of ClO₂ on bacteria (P. aeruginosa, V. mimicus and S. aureus) exceeded 99.9%; thus, ClO₂ gas exhibited a high disinfection efficiency. In addition, there was no corrosion to various metals by ClO₂ under the same conditions. Consequently, gaseous ClO₂ at ultra-low concentrations has a high sterilization efficiency and is non-corrosive to metals.     

Effects of Operational Factors on Pollutant Emission Rates from Residential Gas Appliances

The NO, NO₂, and CO emissions from residential gas combustion appliances contribute to indoor air pollution. The work described investigated the impact of various unvented gas appliances designs and/or operational factors on pollutant emission rates. All experiments were performed in a 1150 ft³ (32.56 m³) all aluminum chamber under controlled conditions. Results are presented for the effect of the following factors on emission rates: 1) appliance type and/or design, 2) primary aeration level, 3) firing rate (fuel input rate), 4) chamber humidity, and 5) time dependence of emission rates. It is concluded that primary aeration level has the largest impact on pollutant emission rates of range-top burners, followed in turn by firing rate, appliance type, chamber humidity, and time dependence of emission rate.     

The Survival of Airborne Serratia marcescens in Urban Concentrations of Sulfur Dioxide

Aerosols of Serratia marcescens ATCC 274 were suspended in a 709L rotating drum at 20 ± 1 °C and high to mid-range relative humidities. At specified times after bacterial aerosolization, sulfur dioxide was added to concentrations of 2.5, or 5 mg/m³. Viable cell decay rate constants, in control aerosols without added sulfur dioxide, increased rapidly from near 100% to 60% RH in the first hour (termed: young aerosol) of suspension, and from a minimum rate constant at 80% in the succeeding four hours (termed: old aerosol).Upon addition of sulfur dioxide to a cloud of S. marcescens, generally, viable cell decay rate constants increased further. One exception was at 80% relative humidity where maximum resistance to SO₂ accelerated death was observed for old aerosols. Cells in young aerosols were particularly sensitive to SO₂ addition at mid-range humidities, while in older aerosols the cells were insensitive to up to 5 mg SO₂/m³ introduced at high RH; but were up to 10 times more sensitive than cells in young aerosols to a given increase (from 2.5 to 5 mg/m³) in SO₂ concentration at mid-range humidities.     

Effect of natural compounds on reducing formaldehyde emission from plywood

The effects of natural compounds on reducing formaldehyde emission from plywood were investigated. Urea, catechin and vanillin were examined as the natural formaldehyde reducers. The microemission cell, with an internal volume of 35 ml, the maximum exposed test surface area of 177 cm² and an air purge flow rate of 50 ml min⁻¹, was used to measure specific emission rate (SER). In the case of no reducer treatment, formaldehyde emission from plywood was fast and SERs were 4.4 mg m⁻² h⁻¹ at 30 °C and 15 mg m⁻² h⁻¹ at 60 °C. When this plywood was treated with the natural compounds, the SERs of formaldehyde were decreased at all temperatures. In the case of urea treatment, the SERs of formaldehyde decreased to 0.30 mg m⁻² h⁻¹ at 30 °C and 0.65 mg m⁻² h⁻¹ at 60 °C. When the urea treatment was applied to the inside of kitchen cabinet (made from plywood; 270 cm wide, 60 cm deep, 250 cm high), the concentration of formaldehyde was reduced substantially from 1600 to 130 μg m⁻³. The reducing effect of formaldehyde continued during the observation period (6 months), with a mean concentration of 100 μg m⁻³. Reducers in the plywood would react with released formaldehyde. Application of natural compounds such as urea, catechin and vanillin could provide a simple and effective approach for suppressing formaldehyde emission from plywood.     

Interlaborafory Comparison of Formaldehyde Emissions from Particleboard Underlayment in Small-Scale Environmental Chambers

Formaldehyde (CH₂O) emissions from particleboard underlayment have been measured in 0.17 and 0.2 m³ chambers at separate laboratories to test the comparability of small scale environmental chamber measurements under different ventilation and product loading conditions. Absolute CH₂O calibration was established through intermethod comparison of different monitoring techniques against a CH₂O generation apparatus. Interlaboratory precision was enhanced via co-calibration of each laboratory’s CH₂O colorimetric analyzer against the same blank and bi-level generation source at the beginning and end of the study. The results show excellent intermethod and interlaboratory agreement in both the CH₂O calibration and particleboard emissions testing. The CH₂O emission rates of the test specimens demonstrate a Fick’s Law dependence on CH₂O vapor concentration. Measured CH₂O concentrations are described by a single-compartment, single emitter model, and are inversely proportional to the ratio [N/L (m/h)] of the air exchange rate [N(h^-1)] and product loading [L(m^-1)]. Comparison tests at varying N and L, but uniform N/L were performed; similar CH2O concentrations were measured for N and L levels selected from an indoor compartment model, and for fivefold larger N and L values, which are more convenient for small-scale chamber testing.     

A new environmental chamber for evaluation of gas-phase chemical mechanisms and secondary aerosol formation

A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m³ FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled enclosure flushed with purified air. Solar radiation is simulated with either a 200 kW Argon arc lamp or multiple blacklamps. Results of initial characterization experiments, all carried out at 300–305 K under dry conditions, concerning NO_x and formaldehyde offgasing, radical sources, particle loss rates, and background PM formation are described. Results of initial single organic–NO_x and simplified ambient surrogate–NO_x experiments to demonstrate the utility of the facility for mechanism evaluation under low NO_x conditions are summarized and compared with the predictions of the SAPRC-99 chemical mechanism. Overall, the results of the initial characterization and evaluation indicate that this new environmental chamber can provide high quality mechanism evaluation data for experiments with NO_x levels as low as 2 ppb, though the results indicate some problems with the gas-phase mechanism that need further study. Initial evaluation experiments for SOA formation, also carried out under dry conditions, indicate that the chamber can provide high quality secondary aerosol formation data at relatively low hydrocarbon concentrations.     

Formaldehyde measurements in Dutch houses,schools and offices in the years 1977–1980

Many formaldehyde concentration measurements were performed in houses, schools and offices where chipboard material was used during the period 1977–1980 following complaints made by inhabitants. In one building the reason for the complaints was formaldehyde emission from urea-formaldehyde insulation foam instead of chipboard.The threshold limit value, established in the Netherlands at 120 μg formaldehyde m⁻³ (0.1 ppm) for living accommodation was exceeded in most cases. The limit was exceeded in 80% of the investigated houses, in 90% of the investigated schools and in 60% of the investigated offices.The efficiency of measures taken to decrease the formaldehyde concentration were investigated in several rooms by repeated measurements afterwards. In some cases the formaldehyde concentration could be reduced to a level lower than the limit value. This was shown to be difficult when the formaldehyde concentration is higher than 300–500 μg m⁻³, due to emission from chipboard. In one building where formaldehyde was emitted from insulation foam in the cavity wall, the formaldehyde concentration could be decreased from 2300 μ μ⁻³ to 80 μg m⁻³.The influence of the temperature and the ventilation rate could be verified in some cases in practice.     

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.     

Monoterpene emissions and carbonyl compound air concentrations during the blooming period of rape (Brassica napus)

An increasing percentage of agricultural land in Germany is used for oil seed plants. Hence, rape has become an important agricultural plant (in Saxony 1998: 12% of the farmland) in the recent years. During flowering of rape along with intensive radiation and high temperatures, a higher production and emission of biogenic VOC was observed. The emissions of terpenes were determined and more importantly, high concentrations of organic carbonyl compounds were observed during this field experiment. All measurements of interest have been carried out during two selected days with optimal weather conditions. It is found that the origin or the mechanism of formation of different group of compounds had strong influence on the day to day variation of their concentrations. The emission flux of terpenes from flowering rape plants was determined to be 16–32 μg h⁻¹ m⁻² (30–60 ng h⁻¹ per g dry plant––540–1080 ng h⁻¹ per plant), in total. Limonene, α-thujene and sabinene were the most important compounds (about 60% of total terpenes). For limonene and sabinene reference emission rates (M_S) and temperature coefficients were determined: β_limonene=0.108 K⁻¹ and M_S=14.57 μg h⁻¹ m⁻²; β_sabinene=0.095 K⁻¹ and M_S=5.39 μg h⁻¹ m⁻².The detected carbonyl compound concentrations were unexpectedly high (maximum formaldehyde concentration was 18.1 ppbv and 3.4 ppbv for butyraldehyde) for an open field. Possible reasons for these concentrations are the combination of primary emission from the plants induced by high temperature and high ozone stress, the secondary formation from biogenically and advected anthropogenically emitted VOC at high radiation intensities and furthered by the low wind speeds at this time.     

Characterization of Several Integrative Sampling Methods for Nitric Acid,Sulphur Dioxide and Atmospheric Particles

Laboratory and field experiments were performed to evaluate integrative measurement methods for atmospheric nitrates, sulphate and sulphur dioxide. Denuder tubes and several filter media were tested under laboratory and field conditions. Effects of sampling variables such as temperature and relative humidity, flow rates, concentration, loading capacity and artifacts due to NO, NO₂ and SO₂ were also evaluated. The integrative filter sampling method and the ion chromatographic analytical procedure gave a measurement precision (relative standard deviation) of ±11.5 percent for particulate NO₃ ^? on Teflon and ±15.6 percent for gaseous HNO₃ on nylon; for both these constituents, the detection limit was about 0.1 μ m^?3.