A field experiment with variable-suction multi-compartment samplers to measure the spatio-temporal distribution of solute leaching in an agricultural soil

Solutes spread out in time and space as they move downwards from the soil surface with infiltrating water. Solute monitoring in the field is often limited to observations of resident concentrations, while flux concentrations govern the movement of solutes in soils. A recently developed multi-compartment sampler is capable of measuring fluxes at a high spatial resolution with minimal disturbance of the local pressure head field. The objective of this paper is to use this sampler to quantify the spatial and temporal variation of solute leaching below the root zone in an agricultural field under natural rainfall in winter and spring. We placed two samplers at 31 and 25 cm depth in an agricultural field, leaving the soil above undisturbed. Each sampler contained 100 separate cells of 31 × 31 mm. Water fluxes were measured every 5 min for each cell. We monitored leaching of a chloride pulse under natural rainfall by frequently extracting the collected leachate while leaving the samplers buried in situ. This experiment was followed by a dye tracer experiment. This setting yielded information that widely surpassed the information that can be provided by separate anionic and dye tracer trials, and solute transport monitoring by coring or suction cups. The detailed information provided by the samplers showed that percolation at the sampling depth started much faster (approximately 3 h after the start of rainfall) in initially wet soil (pressure head above − 65 cm) than in drier soil (more than 14 h at pressure heads below − 80 cm). At any time, 25% of the drainage passed through 5–6% of the sampled area, reflecting the effect of heterogeneity on the flow paths. The amount of solute carried by individual cells varied over four orders of magnitude. The lateral concentration differences were limited though. This suggests a convective–dispersive regime despite the short vertical travel distance. On the other hand, the dilution index indicates a slight tendency towards stochastic–convective transport at this depth. There was no evidence in the observed drainage patterns and dye stained profiles of significant disturbance of the flow field by the samplers.     

一株耐镉细菌的分离及其富集Cd的机理

从重金属镉污染土壤中筛选到一株对镉具有较强抗性和富集能力的细菌RC。经形态学观察和生理生化鉴定以及16SrDNA序列分析,RC为蜡状芽孢杆菌（Bacillus cereus）。在不同镉浓度液体培养条件下研究了菌体的生长曲线,并探讨了RC菌株对Zn、Cu的抗性,结果显示RC对不同重金属的抗性机制存在一定的差异。利用扫描电镜、透射电镜观察了镉在RC胞内外的沉积作用及分布情况,结果表明,在镉浓度为150 mg/L时菌体细胞壁及其内部可见大量的高电子密度颗粒,同时在菌体表面也有沉淀物附着。因此,胞内外沉积作用可能是该菌对高浓度镉的抗性和富集作用的重要途径。通过红外光谱探讨了RC积累镉前后细胞壁表面化学基团的变化情况,结果发现RC的细胞壁上参与积累作用的化学官能团主要有—OH、—NH、—CO和—CO—NH—等。     

Specificity of communication channels in four limacodid moths: Darna bradleyi, Darna trima, Setothosea asigna, and Setora nitens (Lepidoptera: Limacodidae)

Summary. Darna bradleyi Holloway, D. trima Moore, Setothosea asigna van Eecke and Setora nitens Walker are sympatric and coseasonal limacodid moths in plantations of oil palm, Elaeis guineensis Jacq. (Arecales: Palmae), in Borneo, southeast Asia. We tested the hypothesis that these four species maintain reproductive isolation through specificity in diel periods of communication, microlocation for communication and/or communication signal (pheromone). Studying diel periodicity of calling behavior by female moths and response by male moths to traps baited with virgin females or synthetic pheromone, we determined that sexual communication of D. bradleyi and D. trima took place from ˜17:30 to 18:45 hr and that of S. asigna and S. nitens from ˜18:45 to 20:00 hr and from ˜18:30 to 19:30 hr, respectively. Over 80% of male S. asigna and S. nitens were captured in pheromone-baited traps suspended >5 m high, whereas male D. bradleyi and D. trima were captured mostly in traps <5 m high. Synthetic pheromone baits attracted male moths in a species-specific manner. Moreover, baits containing both S. asigna and S. nitens pheromones failed to attract any male moths, indicating that female S. asigna and S. nitens, with overlapping communication periods, use bifunctional pheromone components that attract conspecific males while repelling heterospecifics. Similarly, addition of D. bradleyi pheromone to S. asigna or S. nitens pheromone reduced attraction of male S. asigna and S. nitens. The failure of D. bradleyi and D. trima, which overlap in time and microlocation for communication, to evolve bifunctional pheromones may be attributed to the recent occurrence of sympatry between D. bradleyi and D. trima in Borneo, apparently too recent for bifunctional pheromones to have evolved. We conclude that D. bradleyi, D. trima, S. asigna and S. nitens utilize any or all of diel periodicity, intra and interspecific effects of communication signal and/or microlocation for signaling, allowing these limacodids to co-inhabit the same habitat and remain reproductively isolated. Received 5 May 2000; accepted 18 August 2000     

Thiolsulfonate functionalized polystyrene resin： Preparation and application in the isolation and identification of electrophilic mutagens

A new approach for isolation and identification of elecrtophilic mutagens from complex matrix was developed.Thiosulfonic anion was immobilized onto polystyrene beads and used as separation media.Potassium polystyryl-thiosulfonate,prepared from polystyryl- sulfonyl chloride and KHS,was observed to selectively react with model electrophilic mutagens such as alkyl halides,α-chloroketones andα-chloroesters to produce polystyryl-thiosulfonic esters.After separation from other nonreactive organic compounds,the beads then reacted with ethanethiol to produce unsymmetrical ethyl disulfides which are easily detected by GC/MS.For one mutagenic compound,only one unsymmetrical disulfide was found to contain its structure part.Thus,the structure of the parent mutagens could be deduced from that of the unsymmetrical disulfides.The degree of functionaiization of the potassium polystyryl-thiosulfonate resin was 1.11 mmol/g.Its reactivity was discussed and its recycling method was reported here.     

Suppression of flame propagation in a long duct by inertia isolation with inert gases

Experimental studies were done with a small pipe with a diameter of 0.043 m and a large pipe with a diameter of 0.49 m to demonstrate the flame propagation suppression with inertia isolation in a long duct. Tests were carried in an ignition section containing propylene/air mixture near stoichiometric concentration and generating a peak flame propagation speed of approximately 100 m/s. The ignition section is connected to a section filled with an inert gas, another section with flammable mixtures, and finally a sufficiently long, ambient section to accommodate flame propagation. The critical length of the inert gas section required for successful suppression of flame from the igniting the flammable section is found to be 0.6 m for CO₂ and 0.9 m for N₂ in the large pipe and 0.2 m for CO₂ and 0.3 m for N₂ in the small pipe. Additional tests with a 3 m of ignition section and peak flame propagation speed of 225 m/s showed that the critical length for successful suppression by CO₂ is only increased slightly to 0.9 m, confirming that the suppression is a result of inertia isolation rather than inert gas dilution. Finally, application of the results in responding to large-scale leak into a long, underground duct is discussed.     

绿色住宅内声环境控制

室内噪声主要来源于室外噪声辐射和室内声源。室内噪声会对人的听力、语言交流、睡眠休息、心脏功能、心理、工作效率、儿童发育等多方面产生不良影响。主要分析绿色住宅内部噪声对室内声环境的影响,综述目前绿色住宅建设中存在着的隔声设计隐患,结合“绿色住宅建设技术要求（2001）”,提出改善室内声环境的优化设计方法,从而就如何加强绿色住宅室内噪声污染危害的防治措施提出一些看法。     

在噪声治理中二次隔振的应用实例

在噪声治理工程中应用二次隔振降低固体传声,可以起到较理想的隔振效果。二次隔振系统固有频率低,可以隔绝低频振动。对制冷系统的压缩机组进行二次隔振,取得了满意的隔振效果。     

一株解淀粉芽胞杆菌的分离鉴定及水质净化效果的研究

采用富集培养及摇瓶实验,从污染河沟底质活性污泥中分离筛选到1株对亚硝态有较强转化能力的菌株HN.经形态特征、生理生化特性、16S rDNA基因序列分析、细胞脂肪酸组成及Biolog全自动微生物鉴定系统分析,鉴定菌株HN为解淀粉芽胞杆菌(Bacillus amyloliquefaciens),并在3种模拟水体环境中对菌株HN的水质净化效果进行了初步研究.结果表明,该菌株在试验第4d能将高浓度模拟污水(水样Ⅰ)、鲫鱼养殖废水(水样Ⅱ)、鲤鱼和对虾养殖废水(水样Ⅲ)中初始浓度分别为6.47、1.20和4.50mg·L-1的亚硝态氮去除100%、46%和100%,而对照的转化率分别为-10.4%、-800%和16.0%,同时对硝态氮也表现较强的去除能力且基本不累积氨氮.环境耐受性试验表明,该菌株在20～45℃、pH5.0～10.0、海盐浓度0.5%～3.0%的范围内都能正常生长.研究认为,解淀粉芽胞杆菌HN能显著降低水体中亚硝态氮和硝态氮的含量,且环境耐受力强,有望将其开发成高效的水产养殖水体净化微生态制剂.     

污泥中一株产耐高温蛋白酶菌株的分离、鉴定及酶学特性

蛋白酶是水解蛋白质肽键的一类酶的总称,它可将蛋白质分解、转化为氨基酸,从而被动植物体直接吸收利用.基于此,以江苏省无锡市太湖新城污水处理厂的污泥为材料,通过观察水解圈大小和蛋白酶活性测定等方法,从中筛选出一株高产蛋白酶菌株TC16.同时,参照《伯杰氏细菌鉴定手册》和《常见细菌鉴定手册》,根据其形态学特征、生理生化特性,并结合16SrDNA序列的比对分析结果发现,该菌属于芽孢杆菌属菌株.对其酶学性质的研究发现,从该污泥中分离得到的菌株TC16分泌的胞外蛋白水解酶的活性最高可达621U·mL-1.研究表明,与其他芽孢杆菌属菌株相比,TC16菌株分泌的蛋白酶具有较高的酶活性,且具有较宽范围的pH和温度耐受性.     

污水处理技术的新发展

概述了污水处理的各种技术，总结了国外污水处理技术的最新发展动态。