预测低温冷害的门限回归模型

提出用门限回归模型（TR）来描述低温灾害指标变量在灾害状况与非灾害状况的突变性。研制了TR建模的一套简便通用的方案，用笔者改进的遗传算法可同时优化门限值和回归系数，从而解决了TR建模过程所涉及的大量复杂寻优工作这一问题，为TR模型的广泛应用提供了有效工具。实例的计算结果说明了其可行性和有效性。该方案具有通用性，在各种自然灾害时序预测中具有广泛的实用价值。     

INTEGRATING PHOSPHORUS AND NITROGEN DECISION MANAGEMENT AT WATERSHED SCALES1

ABSTRACT: The persistence of water quality problems has directed attention towards the reduction of agricultural nonpoint sources of phosphorus (P) and nitrogen (N). We assessed the practical impact of three management scenarios to reduce P and N losses from a mixed land use watershed in central Pennsylvania, USA. Using Scenario 1 (an agronomic soil P threshold of 100 mg Mehlich‐3 P kg^‐1, above which no crop response is expected), 81 percent of our watershed would receive no P as fertilizer or manure. Under Scenario 2 (an environmental soil P threshold of 195 mg Mehlich‐3 P kg^‐1, above which the loss of P in surface runoff and subsurface drainage increases greatly), restricts future P inputs in only 51 percent of the watershed. Finally, using scenario 3 (P and N indices that account for likely source and transport risks), 25 percent of the watershed was at high risk or greater of P loss, while 60 percent of the watershed was classified as of high risk of nitrate (NO₃) leaching. Areas at risk of P loss were near the stream channel, while areas at risk of NO₃ leaching were near the boundaries of the watershed, where freely draining soils and high manure and fertilizer N applications coincide. Remedial measures to minimize P export should focus on critical source areas, while remedial measures to reduce N losses should be source based, concentrating on more efficient use of N by crops.     

RELATIONSHIPS BETWEEN WIND VELOCITY AND UNDERWATER IRRADIANCE IN A SHALLOW LAKE (LAKE OKEECHOBEE,FLORIDA, USA)1

ABSTRACT: Relationships between wind velocity and the vertical light attenuation coefficient (K₀) were determined at two locations in a large, shallow lake (Lake Okeechobee, Florida, USA). K₀ was significantly correlated with antecedent wind conditions, which explained as much as 90 percent of the daily variation in K₀. Sub-surface irradiance began to change within 60 to 90 minutes of the time when wind velocity exceeded or dropped below a threshold value. Maximum one hour changes in K₀ were > 50 percent, however, 20 to 30 percent changes were more common. The magnitude of change in K₀ varied spatially based on differences in sediment type. K₀ never exceeded 2.8 at a location where bottom sediments were dominated by a mixture of coarse sand and shells. In comparison, K₀ exceeded 9 during episodic wind events where the bottom sediment was comprised of fine grain mud. Underwater irradiance data can be used to determine threshold wind velocity and account for the influence sediment type has on K₀. Once a threshold velocity has been established, the frequency, rate, and duration of expected change in underwater irradiance can be evaluated. This is critical information for scientists who are studying algal productivity or other light-related phenomena.     

Nestmate recognition in the ant Cataglyphis niger : do queens matter?

This study compares two basic models for the origin and maintenance of colony gestalt odor in the polygynous ant species Cataglyphis niger. In the first model, queens are centers of de novo biosynthesis and distribution of recognition odors (“queen-centered” model); in the second, colony odors are primarily synthesized and distributed by workers (“worker-centered” model). We tested the behavioral patterns that are predicted from each model, and verified by biochemical means the distributional directionality of these signals. Encounters between nestmates originating from split colonies were as amicable as between nestmates from non-split colonies; queenless ants were as aggressive as their queenright nestmates, and both were equally aggressed by alien ants. These results indicate that queens have little impact on the recognition system of this species, and lend credence to the worker-centered model. The queen-centered model predicts that unique queen substances should be produced in appreciable quantities and that, in this respect, queens should be more metabolically active than workers. Analysis of the chemical composition of postpharyngeal glands (PPGs) or cuticular extracts of queens and workers revealed high similarity. Quantitatively, queens possessed significantly greater amounts of hydrocarbons in the PPG than workers, but the amount on the thoracic epicuticle was the same. Queens, however, possess a lower hydrocarbon biosynthesis capability than workers. The biochemical evidence thus refutes the queen-centered model and supports a worker-centered model. To elucidate the directionality of cue distribution, we investigated exchange of hydrocarbons between the castes in dyadic or group encounters in which selective participants were prelabeled. Queens tended to receive more and give less PPG content, whereas transfer to the epicuticle was low and similar in all encounters, as predicted from the worker-centered hypothesis. In the group encounters, workers transferred, in most cases, more hydrocarbons to the queen than to a worker. This slight preference for the queen is presumably amplified in a whole colony and can explain their copious PPG content. We hypothesize that preferential transfer to the queen may reflect selection to maintain her individual odor as close to the average colony odor as possible. Received: 4 November 1997 / Accepted after revision: 5 February 1998     

冬季水库水源中MIB和土嗅素的产生与降解机理

2-甲基异冰片(MIB) 和土嗅素(geosmin)由放线菌,真菌和蓝绿藻代谢产生,这两种物质是目前造成饮用水具有霉味和土味的主要原因.以包头市画匠水库为研究对象,运用推流式反应器基本模型和OriginPro 9.0线性拟合法,分析冬季水源水库水中MIB和土嗅素净产率与损失率;运用双膜理论计算嗅味物质挥发速率常数.结果表明,冬季画匠水库0.55m冰层下,透射光照强度(Surface PAR)为70 ~ 636W/m2,平均光照强度为114.8W/m2,存在合适藻类代谢产生异味物质的光照条件.封冻前后,水库水中MIB和土嗅素浓度逐渐增高,并以60~102ng/L的较高浓度水平维持到来年解冻,此后二者浓度逐渐降低到较低水平,呈规律性变化.曲线拟合结果显示,冬季画匠水库水中MIB/土嗅素的产生与减少均符合准一级反应动力学模型(R2为0.941~0.989).由于低温与冰层阻碍等原因,影响水库中MIB/土嗅素的损失主要因素是出流携带;冰层融化后,挥发和出流携带是MIB/土嗅素减少的主要原因.MIB和土嗅素冬季产生速率常数为4.119, 2.146ng/(L×d),水流携带损失速率常数为0.032d-1.冰层融化后,MIB产生速率为1.012ng/(L×d),损失速率为0.072d-1,藻细胞产率4.57×10-8ng/(L×d×cell);土嗅素产生速率常数为1.638ng/(L×d),损失速率为0.083d-1,藻细胞产率5.46×10-8ng/(L×d×cell).     

垃圾转运站空气中挥发性有机化合物分析

通过对垃圾转运站空气样品进行分析,共检出主要挥发性有机化合物43种。其中国家《恶臭污染物排放标准》控制污染物有4种,它们的含量相对较低,但波动范围较大;USEPA优先控制污染物有5种,虽然种类不多,但检出率较高,因此不应忽视其对环境的影响。     

基于图像处理的湍流轴对称火焰体积与表面积计算方法

基于"圆柱体法"思想设计出轴对称火焰的火焰体积和表面积计算公式,以25cm×25cm正庚烷油池火为例,采用灰度阈值法提取其火焰区域,进而计算轴对称火焰的体积和表面积,并讨论灰度阈值对火焰区域提取、火焰体积与表面积计算的影响。结果表明:本文所述方法可以简便地计算湍流轴对称火焰的火焰体积和表面积;火焰体积与表面积随灰度阈值增大而减小且灰度阈值变化对火焰体积的影响幅度约为对火焰表面积影响幅度的两倍。     

恶臭污染物的排放与监测

概括介绍恶臭污染源的形成、排放特征及恶臭污染物的监测技术,重点介绍了我国测定恶臭的国家标准方法“三点比较式臭袋法”及其实际操作中若干问题解析。     

Field studies on the ammonia odor threshold based on ambient air-sampling following accidental releases

Ammonia is one of the most widely produced and utilized chemicals in the U.S., and while numerous lab studies have been undertaken, there is no consensus on the odor threshold. In contrast to controlled lab conditions used to determine odor thresholds, the field conditions following unintentional chemical releases are uncontrolled and highly variable due to many factors. A critical component in managing the response to these chemical spills involves understanding how lab data could be applied to uncontrolled field conditions in and around the affected community. It was postulated that analysis of field data collected following accidental releases of ammonia might augment and verify data collected in lab experiments. The widespread transport and use of ammonia has resulted in a number of unintentional releases of ammonia into the environment as a result of train derailments, tanker spills, and plant accidents. In the field studies reported here, air monitoring data were collected following a variety of accidental ammonia releases. Of 6539 readings between 0 and 1 ppm, odor was detected only in 208 samples (3.2%). Of 65 readings between 1.1 and 1.5 ppm, odor was detected in 51 samples (78.5%). These data are consistent with an ammonia odor threshold within a concentration range of 1.1–1.5 ppm. This level is consistent with the recently published odor threshold data for ammonia, but is significantly lower than frequently cited historical data. Furthermore, a review of the ammonia literature demonstrates that the ammonia odor threshold is significantly lower than levels that produce eye, nose, or throat irritation.     

等离子在卷烟厂除异味系统中的应用研究

卷烟厂中存在很多醛,酮有害气体,会大大降低工作环境的质量。针对此问题,提出了在高压直流上叠加高频电压交流脉冲的基础上调节可变电容改变电路阻抗的方法改进等离子体除异味装置。在高频高压脉冲电源下,利用可变电容与交直流叠加技术,产生高频高压快速上升沿的交流脉冲,改变负载回路上的阻抗,比较品质因数不同情况下产生的等离子,满足产生更佳低温等离子体的需求。经仿真实验结果和烟厂异味气体的成分分析表明,利用该方法可以达到除异味的理想效果,使工作环境得到更大更好的改善。