混合层深度对藻类生长的影响研究

三峡水库蓄水后,支流库湾频繁暴发水华.为研究水华暴发关键因子,以临界层理论为指导,于2012年初冬季,在香溪河野外观测站建立围隔实验系统,研究水体混合对藻类生长的影响机制.围隔水下深度按梯度布设,表底掺混均匀,并注入由浮游动物网过滤的低Chl-a浓度的香溪河河水.结果表明,Zeu/Zmix(真光层深度与混合层深度之比)>1的围隔藻类生长迅速并暴发水华,Chl-a浓度最高达到90 mg·m-3,反之生长缓慢.临界层理论适用于本实验,Zeu/Zmix也存在一个临界值,低于临界值浮游植物生长会受光限制而不易暴发水华;在临界层理论的基础上,分析得藻类净初级生产力与Zmix存在负相关关系,即Zmix越小藻类净初级生产力越大.     

车载激光雷达对北京地区边界层污染监测研究

介绍了自行研制的车载差分激光雷达AML-2探测原理及技术参数,于2006-08、2006-09在不同天气因素条件下对北京西南郊榆垡地区大气边界层污染物O3、NO2、SO2进行了实时监测,对比分析了3种污染物浓度垂直分布及日变化特征.结果表明,无外来污染输送时,3种污染物在阴雨天气总体浓度较小,O3和NO2浓度随高度升高而减小,SO2浓度垂直分布少见此特征,但在近地面0.6 km左右有较强SO2污染层.南部气流输送对北京地区大气环境影响明显,2006-08-23～2006-08-25这次强污染气流输送高度约1～1.5 km,3种污染物浓度垂直分布及日变化特征受到干扰,北京榆垡地区边界层O3、NO2、SO2总体浓度明显上升.     

静电除尘器的粉尘非稳态收集过程

为了全面揭示电除尘器粉尘非稳态收集过程,建立完整的非稳态静电收尘理论,根据静电学基本原理,研究了极板粉尘层电荷导人、积累、释放的过程,推导出随粉尘层厚度增长而改变的动态收尘电场强度计算公式,进而得到荷电粒子动态驱进速度公式,最终形成静电除尘非稳态收集理论.研究结果表明,在静电收尘过程中,粒子驱进速度与粉尘比电阻、工作电压、粉尘层厚度等多种因素有关;随粉尘比电阻的升高,收尘效率下降,当供电电压为最佳工作电压时收尘效率最高.针对不同比电阻粉尘进行了多项实验研究,实验结果与理论研究结果吻合.非稳态静电收尘理论成功地解释了实际静电收尘过程中与传统静电收尘理论相矛盾的地方,为静电除尘器的设计及其运行参数的选取提供了更为科学的理论基础.     

Sudden high concentration of TSP affected by atmospheric boundary layer in Seoul metropolitan area during duststorm period

Hourly concentrations of TSP, PM(10), PM(2.5) near the surface at Seoul city were examined from March 20 to March 25, 2001 (duststorm event) in order to investigate the effect of a duststorm generated in China on the local aerosol concentration in Korea, The ratios of fine to coarse particles such as TSP to PM(10), TSP to PM(2.5) and PM(10)-PM(2.5) to PM(2.5) showed that a great amount of dust transported from the origin of the duststorm was remarkable with a maximum ratio of 9.77 between TSP and PM(2.5). Back trajectories every 6 h showed the movement of dust particles in the lower atmosphere near 500 m to 1500 m (atmospheric boundary layer), which implied transport from Baotou in inner Mongolia of northern China to the direction of Seoul city in Korea and then the back trajectories passed near the southern border of Mongolia and Baotou through Zengzhou in the midlevels (3000 m) and low levels (500 m) of China, finally reaching Seoul city. So, the TSP concentration at Seoul city was partially influenced by the duststorm, under the prevailing westerly wind and the transported aerosols could influence high concentrations of pollutants of TSP, PM(10) and PM(2.5) in Seoul. The sudden high concentrations of TSP and PM(10) were found for a few hours, especially at 1500 to 1800 LST, March 22. At 1200 LST, before the passage of a cold front through the Korean peninsula, the convective boundary layer (CBL) near Seoul was not shallow, but at 1500 LST, under the frontal passage, the CBL was remarkably thinner (less than 300 m), due to the compression of the boundary layer by the intrusion of cold air. This resulted in the increase of the TSP concentration, even though the mixed layer above maintained almost the same depth. At 1800 LST shortly after the frontal passage, that is, near sunset, the nocturnal cooling of the ground caused air parcels to cool, thereby enhancing the shallower nocturnal surface inversion layer and producing the maximum concentration of TSP of 1388 microg/m(3) near Seoul city.     

Integrating soil carbon cycling with that of nitrogen and phosphorus in the watershed model SWAT: Theory and model testing

In this paper we describe and test a sub-model that integrates the cycling of carbon (C), nitrogen (N) and phosphorus (P) in the Soil Water Assessment Tool (SWAT) watershed model. The core of the sub-model is a multi-layer, one-pool soil organic carbon (S_C) algorithm, in which the decomposition rate of S_C and input rate to S_C (through decomposition and humification of residues) depend on the current size of S_C. The organic N and P fluxes are coupled to that of C and depend on the available mineral N and P, and the C:N and N:P ratios of the decomposing pools. Tillage explicitly affects the soil organic matter turnover rate through tool-specific coefficients. Unlike most models, the turnover of soil organic matter does not follow first order kinetics. Each soil layer has a specific maximum capacity to accumulate C or C saturation (S_x) that depends on texture and controls the turnover rate. It is shown in an analytical solution that S_x is a parameter with major influence in the model C dynamics. Testing with a 65-yr data set from the dryland wheat growing region in Oregon shows that the model adequately simulates the S_C dynamics in the topsoil (top 0.3 m) for three different treatments. Three key model parameters, the optimal decomposition and humification rates and a factor controlling the effect of soil moisture and temperature on the decomposition rate, showed low uncertainty as determined by generalized likelihood uncertainty estimation. Nonetheless, the parameter set that provided accurate simulations in the topsoil tended to overestimate S_C in the subsoil, suggesting that a mechanism that expresses at depth might not be represented in the current sub-model structure. The explicit integration of C, N, and P fluxes allows for a more cohesive simulation of nutrient cycling in the SWAT model. The sub-model has to be tested in forestland and rangeland in addition to agricultural land, and in diverse soils with extreme properties such high or low pH, an organic horizon, or volcanic soils.     

厚煤层分层综采工作面的瓦斯治理

结合矿井瓦斯管理的实际,介绍了高瓦斯厚煤层分层综采工作面瓦斯治理的技术经验,具有很强的针对性和可操作性,实现了矿井在特殊阶段的安全生产.     

保护层分析中独立保护层的识别研究

为阐述保护层分析(LOPA)中独立保护层(IPL)的识别规则,以及这些规则在实际应用中要注意的问题,以生产聚氯乙烯(PVC)的间歇聚合反应为例,对8个不同的LOPA场景进行分析,给出不同场景的IPL和要求时的失效概率(PFD),以及建议增加的IPL。分析结果表明,在进行IPL的识别时,应重点确认IPL的有效性和独立性。在评估IPL有效性时,应关注具有共同元件的IPL,IPL的行动能力、人员行动有效性及IPL的PFD等。在评估独立性时,应确保IPL独立于初始事件和同一场景中的其他IPL的任何构成元件。通过分析,发现PVC工艺中安全阀(PSV)设计、安全仪表功能(SIF)设计和人员行动等IPL中存在的问题,并提出相应的建议。     

保护层开采效果测评指标及应用研究

为深入分析保护层开采的实施效果,依据煤岩卸压变形理论和瓦斯运移特性,建立保护层开采测评指标体系,并选择淮南矿区对指标现场应用方法进行分析。研究结果表明:测评体系包括保护范围和保护效果两部分,其中,瓦斯压力、瓦斯含量、煤层透气性系数、煤层顶底板相对变形、瓦斯抽放量、突出指标的变化等因素可作为效果考察的现场测评指标。保护层开采后,应首先明确其保护范围,然后再对保护效果分别从煤体力学特性、煤层瓦斯特性和煤层开采动力特性3方面进行综合分析,按照现场实测值与指标临界值的对比,即可系统地定量评价保护层开采的效果。     

气溶胶辐射效应对气象和环境影响的观测与模拟研究

选取2015年和2019年不同代表年份,结合外场观测和数值模拟,分析了天津地区不同季节不同天气(晴天、多云、霾)下,气溶胶辐射效应对整层大气透过率和地表入射太阳辐射的影响,以及这种影响在不同年份的差异.借助WRF-Chem模式模拟分析了重污染期间气溶胶辐射效应对垂直方向上气象要素廓线、边界层结构以及PM_2.5浓度的反馈机制.结果表明:霾污染可导致大气透过率明显下降,春、秋、冬不同季节,霾污染导致中午大气透过率分别下降0.09,0.11和0.09.全年平均霾污染可导致大气透过率降低约15.5%.云量的增多也可导致大气透过率明显下降,多云天气下大气透过率相比晴天减小约22.4%.霾和云对大气透过率的影响还与太阳高度角有关,当太阳高度角>60°时,霾污染导致大气透过率下降8.6%.随污染等级提高,气溶胶对太阳辐射的衰减作用也越强,天津地区空气质量分别为Ⅰ～Ⅰ级时,中午地表入射短波辐射呈稳定下降趋势,依次为484,446,439,342,328和253W/m².重污染期间,气溶胶辐射效应导致大气低层(250m以下)降温(0.8℃)增湿(3.8%...     

基于双电极传感器的腐蚀电流检测系统抗扰技术

目的 针对金属电化学腐蚀中腐蚀电流检测,设计一种高精度I-V转换的微电流检测电路,突破宽范围微弱电流高精度检测技术。方法 通过分析电路的稳定性,针对100 pA~10 mA的微弱腐蚀电流采集,采用法安级偏置运放实现I-V转换,设计基于ADG708电子开关的8档自动调节电路,并通过24位ADC实现高精度模数转换。针对微弱电流采集中信号易受噪声的影响,设计自适应滤波器用于信号滤波处理。结果 通过MATLAB仿真自适应滤波器的有效性,结果表明,在采集i(k)=2sin(2πk)电流时,误差从0.29 mA(1σ)降低到0.003 9 mA(1σ)。通过电流源校准测试系统精度,在100 pA时误差最大,为4.7%;在10 mA时误差最小,为0.049%。当电流值低于100 nA时,测量误差可以控制在5%以内;100 nA以上时,测量误差可以控制在1%以内。结论 在微弱电流采样中引入自适应滤波器后,系统的采样精度显著提高,突破了宽范围的腐蚀电流采集技术,实现了微弱电流检测。可以将腐蚀电流应用在金属腐蚀速率的评价中。