Persistence of radon-222 flux during monsoon at a geothermal zone in Nepal

The Syabru-Bensi hydrothermal zone, Langtang region (Nepal), is characterized by high radon-222 and CO₂ discharge. Seasonal variations of gas fluxes were studied on a reference transect in a newly discovered gas discharge zone. Radon-222 and CO₂ fluxes were measured with the accumulation chamber technique, coupled with the scintillation flask method for radon. In the reference transect, fluxes reach exceptional mean values, as high as 8700 ± 1500 g m⁻² d⁻¹ for CO₂ and 3400 ± 100 × 10⁻³ Bq m⁻² s⁻¹ for radon. Gases fluxes were measured in September 2007 during the monsoon and during the dry winter season, in December 2007 to January 2008 and in December 2008 to January 2009. Contrary to expectations, radon and its carrier gas fluxes were similar during both seasons. The integrated flux along this transect was approximately the same for radon, with a small increase of 11 ± 4% during the wet season, whereas it was reduced by 38 ± 5% during the monsoon for CO₂. In order to account for the persistence of the high gas emissions during monsoon, watering experiments have been performed at selected radon measurement points. After watering, radon flux decreased within 5 min by a factor of 2–7 depending on the point. Subsequently, it returned to its original value, firstly, by an initial partial recovery within 3–4 h, followed by a slow relaxation, lasting around 10 h and possibly superimposed by diurnal variations. Monsoon, in this part of the Himalayas, proceeds generally by brutal rainfall events separated by two- or three-day lapses. Thus, the recovery ability shown in the watering experiments accounts for the observed long-term persistence of gas discharge. This persistence is an important asset for long-term monitoring, for example to study possible temporal variations associated with stress accumulation and release.     

Temperature dependence of the absolute rate constant for the reaction of ozone with dimethyl sulfide

Absolute rate constants for the reaction of ozone with dimethyl sulfide (DMS) were measured in a 200-L Teflon chamber over the temperature range of 283-353 K. Measurements were carried out using DMS in large excess over ozone of 10 to 1 or greater. Over the indicated temperature range,the data could be fit to the simple Arrhenius expression as KDMS = (9.96±3.61)×10-11exp(-(7309.7±1098.2)/T)cm3/(molecule·s). A compared investigation of the reaction between ozone and ethene had a kc2H4 value of(1.35±0.11)×10-18 cm3/(molecule·s) at room temperature.     

地下洞室及其围岩爆破地震安全监测与动力分析

基于地下洞室及其围岩的爆破震动安全监测,通过质点振动速度峰值及其卓越频率分析,论述爆破地震波的传播规律以及地下洞室与围岩爆破地震作用下的动力特性,并对爆破地震安全监测与分析结果进行解释与原因探讨。通过大量监测数据的回归分析,得出质点振动速度峰值与爆破药量和距离及环境条件的关系式,并在分析三者关系的基础上指出,近爆破点区域的爆破地震波衰减速度明显大于较远区域,爆破引起的质点振动速度峰值的卓越频率集中在以45Hz为中心的15~75Hz范围值。质点振动速度峰值及其卓越频率与爆破规模与环境的几何因素密切相关,介质本身的物理几何特性是爆破地震波衰减的主要影响因素之一。     

Suppression of gas explosion using vacuum chamber at different break-up times of diaphragm

Vacuum chamber is a new method to suppress the gas explosion. The explosion propagation characteristics have been studied in an L-shaped channel (tubes joined a right angle) with a vacuum chamber in the region of joining of the tubes. The vacuum chamber separated from the inner tubular space with the help of a diaphragm pierced by firing pin. The results demonstrate that the effect of explosion suppression of vacuum chamber is related to the break-up time of diaphragm and the position of the explosive flame front. When the diaphragm breaks up, the shorter the distance of flame front propagation is, the closer the flame front gets to the vacuum chamber, and the better effect of explosion suppression is, conversely, the worse the effect of explosion suppression is.     

松花江上游夹皮沟金矿土壤与大气汞污染特征

在松花江上游夹皮沟金矿开采区内,混汞法提金工艺已使用180余年,导致严重的环境介质汞污染问题.为研究土壤和大气汞污染特征,使用塞曼效应汞分析仪(Zeeman RA915+)测定了大气汞含量,使用冷原子吸收分光光度法(GB/T17136-1997)测定了土壤汞含量,使用动态通量箱法测定了老金厂、二道沟、二道岔和夹皮沟镇小区四处土/气间汞交换通量;对土壤汞含量和大气汞含量进行了线性回归分析;并对土/气间汞交换通量与气象因子进行了相关性分析.结果表明:①区域大气汞含量均值为(71.08±38.22)ng.m-3.②区域土壤汞含量均值为(0.913 1±0.040 8)mg.kg-1;土壤汞含量与大气汞含量显著正相关.③各采样点土/气间汞交换通量为:老金厂(129.13±496.07)ng.(m2.h)-1,二道沟(98.64±43.96)ng.(m2.h)-1,二道岔(23.17±171.23)ng.(m2.h)-1,夹皮沟镇小区(7.12±46.33)ng.(m2.h)-1.④太阳辐射是老金厂、二道岔和夹皮沟镇小区土/气间汞交换通量主要影响因子,太阳辐射、大气温度和土壤温度共同控制二道沟土/气汞交换通量过程;地形条件的干扰,形成三类迥异的土/气间汞交换通量日变化特征形态.     

Review of the influencing factors of secondary organic aerosol formation and aging mechanism based on photochemical smog chamber simulation methods

The formation and aging mechanism of secondary organic aerosol (SOA) and its influencing factors have attracted increasing attention in recent years because of their effects on climate change, atmospheric quality and human health. However, there are still large errors between air quality model simulation results and field observations. The currently undetected components during the formation and aging of SOA due to the limitation of current monitoring techniques and the interactions among multiple SOA formation influencing factors might be the main reasons for the differences. In this paper, we present a detailed review of the complex dynamic physical and chemical processes and the corresponding influencing factors involved in SOA formation and aging. And all these results were mainly based the studies of photochemical smog chamber simulation. Although the properties of precursor volatile organic compounds (VOCs), oxidants (such as OH radicals), and atmospheric environmental factors (such as NO_x, SO₂, NH₃, light intensity, temperature, humidity and seed aerosols) jointly influence the products and yield of SOA, the nucleation and vapor pressure of these products were found to be the most fundamental aspects when interpreting the dynamics of the SOA formation and aging process. The development of techniques for measuring intermediate species in SOA generation processes and the study of SOA generation and aging mechanism in complex systems should be important topics of future SOA research.     

养殖塘CH4通量时空变化特征及其影响因素

本研究基于多通道密闭式动态箱法对亚热带典型养殖塘CH₄通量的时空变化特征及其影响因素进行了分析.结果表明：亚热带养殖塘CH₄主要排放方式是冒泡,CH₄扩散及冒泡通量均呈现明显的季节变化特征.春、夏、秋、冬4个季节CH₄扩散通量分别为：0.113,0.830,0.002,0.005μmol/（m²·s）,冒泡通量分别为0.923,1.789,0.006,0.007μmol/（m²·s）,冒泡通量占总通量的比例分别为89.04%、68.29%、78.95%和60.52%.在冬、春季养殖塘没有人工管理措施的情况下,CH₄通量随着离岸距离的增加而增大,冬、春季养殖塘中间区域CH₄总通量分别是岸边浅水区的34.70和2.98倍.夏季养殖活跃期CH₄通量在空间上呈现出：人工投食区（7.371μmol/（m²·s））>自然生长区（2.151μmol/（m²·s））>人工增氧区（0.888μmol/（m²·s））>岸边浅水区（0.206μmol/（m²·s））的特征.在0.5h尺度上,春季CH₄扩散通量与水温呈显著正相关关系,与风速呈负相关关系,秋季CH₄扩散通量与水温、风速呈正相关关系,冒泡通量和水温呈正相关关系.在日尺度上,水温是CH₄扩散通量和冒泡通量的主控因子,两者均随着水温升高呈指数增加,并且冒泡通量的水温敏感性Q₁₀（12.72）大于扩散通量（7.78）.     

改进式开顶气室模拟CO2浓度控制系统性能分析

为提高开顶气室（open-top chamber,OTC）模拟气候变化研究植物生理响应的控制效果,基于前期OTC控制系统基础,对气室结构、控制系统及监测系统改进升级。对改进后的OTC控制系统采集了试验期间5月—10月OTC气室内CO₂浓度、温度及空气相对湿度实时数据分析模拟效果,结果表明：改进后的OTC控制系统能够控制CO₂浓度达到试验预设浓度梯度,在试验期OTC气室内监测的CO₂浓度平均值对照组（CK）为369.33 μmol?mol^?1,处理1组（TR1）为558.35 μmol?mol^?1,处理2组（TR2）为772.71 μmol?mol^?1;CO₂浓度波动范围TR1组为551.82—572.40 μmol?mol^?1,变幅为20.58 μmol?mol^?1;TR2组为756.71—779.79 μmol?mol^?1,变幅为23.08 μmol?mol^?1,满足试验预设模拟要求;气室内不同处理间温度、空气相对湿度差异均不显著（p＞0.05）。改进后的OTC控制系统模拟效果好,可用于研究植物响应气候变化的模拟试验。     

氨与甲苯SOA形成含氮有机物的影响因素研究

利用自制的烟雾腔系统使臭氧光解产生OH自由基,启动甲苯光氧化产生二次有机气溶胶（SOA）粒子,在不同的实验条件下研究甲苯SOA与氨反应形成的含氮有机物,并采用紫外-可见分光光度计测量反应产物溶液在205和270nm处的吸光度,探究光照时间、甲苯、氨、臭氧浓度和相对湿度等环境因素对含氮有机物形成的影响规律.结果表明,有机酸铵和咪唑类产物的生成浓度随着紫外光照时间的延长,甲苯、氨和臭氧的浓度的增加而逐渐增大.但是当臭氧浓度超过一定值后,光解生成的高浓度OH自由基能够使甲苯光氧化产物变成更多的挥发性化合物,从而不利于含氮有机物的生成.水分子的增加会使臭氧光解产生的OH自由基浓度减少,从而导致有机酸铵和咪唑类产物的生成浓度随着相对湿度的增大而降低.这为研究人为源SOA颗粒中含氮有机物棕色碳的形成提供了实验依据.     

IEC 60068-2-5中辐照度和温度的解读

为了更好解读IEC 60068-2-5:2010中的辐照度和温度设定,及如何执行该标准,结合标准中对辐照度和温度设定的要求,提供具体的解决方案。建议在执行标准时,应使用日光过滤片来过滤氙灯光源,实现该标准对光源的要求。同时建议使用340 nm点控制,辐照度设定为0.60 W/m2@340 nm。对于温度的设定,建议按照标准中图2的温度上升、下降与时间的关系,对其进行设定。另外,标准中程序A的循环接近最严酷的自然条件,而程序B和程序C的循环比程序A的严酷很多。因此,一般情况下推荐程序A,对于耐候性好的材料,需要加速测试的,推荐程序B。