两种淹水模式下施用钝化材料对镉污染农田水稻安全生产的影响

为实现镉(Cd)污染农田稻米安全生产,以中度Cd污染农田为研究对象,通过连续2 a的大田试验,对比分析了间歇性淹水和全生育期淹水2种淹水模式下,玉石粉、生物炭和粉煤灰这3种钝化材料施用后对土壤pH,有效Cd和稻米Cd含量的影响.结果 表明:①单一淹水处理下,全生育期淹水和间歇性淹水处理均可提高土壤pH,土壤有效Cd降低...     

淹水对污染土壤镉形态转化的影响

研究了受铜冶炼厂“三废”污染的土壤在栽种小麦－水稻－小麦的过程中土壤镉形态的转化。结果表明，淹水后交换态镉形态所占比例明显下降，下降幅旗与土壤氧化铁活化度呈极显负相关。所下降的部分向着活性较低的紧结合有机态，晶形氧化铁结合态及石灰性土壤的碳酸盐结合态转化。     

Deflagration suppression using expanded metal mesh and polymer foams

Expanded metal mesh and polymer foams of appropriate pore or cell size and sufficient surface area per unit volume can suppress deflagrations of gas/vapor–air mixtures. This paper reviews the requirements that have been established for use of these materials in military aircraft fuel tanks. Extensions and generalizations of these requirements for other applications have been developed and incorporated into the 2008 edition of the NFPA 69 Standard for Explosion Prevention. The new NFPA 69 requirements for testing, evaluating, and installing these materials are summarized here along with an explanation of the basis and rationale for these requirements.     

固相萃取剂在富集检测极性有机污染物领域的应用研究进展

介绍了常用固相萃取剂的类型与适用范围,综述了近年来在极性有机污染物富集检测中获得应用的新型固相萃取剂,包括具有高比表面积和亲水表面的聚合物萃取剂,以及利用分子印迹和免疫亲和技术制备的新型萃取剂。     

Street floods in Metro Manila and possible solutions

Urban floods from thunderstorms cause severe problems in Metro Manila due to road traffic. Using Light Detection and Ranging (LiDAR)-derived topography, flood simulations and anecdotal reports, the root of surface flood problems in Metro Manila is identified. Majority of flood-prone areas are along the intersection of creeks and streets located in topographic lows. When creeks overflow or when rapidly accumulated street flood does not drain fast enough to the nearest stream channel, the intersecting road also gets flooded. Possible solutions include the elevation of roads or construction of well-designed drainage structures leading to the creeks. Proposed solutions to the flood problem of Metro Manila may avoid paralyzing traffic problems due to short-lived rain events, which according to Japan International Cooperation Agency (JICA) cost the Philippine economy 2.4 billion pesos/day.     

某聚合物驱油先导实验职业卫生调查

对某采油厂聚合物驱油先导试验项目进行了职业卫生调查,以明确有害因素存在的岗位部位、种类、危害程度,并对职业病危害控制措施及效果进行调查分析。     

Influence of flooding and vegetation on carbon, nitrogen, and phosphorus dynamics in the pore water of a Spartina alterniflora salt marsh

Four sites were selected in a salt marsh in the Bah′?a Blanca Estuary (Argentina): (1) low marsh (flooded by the tide twice daily) vegetated by S. alterniflora; (2) non-vegetated low marsh; (3) high marsh (flooded only in spring tides) vegetated by S. alterniflora; (4) non-vegetated high marsh. The pH and Eh were measured in sediments, while dissolved nutrients (ammonium, nitrate, nitrite and phosphate) and particulate organic matter (POM) were determined in pore water. pH (6.2–8.7) was only a ected by vegetation in low areas. Eh (from –300 to 250 mV) was lower at low sites than at high ones; in the latter, the values were higher in the non-vegetated sediments. The POM concentration was greater in the high marsh than in the low marsh, with no e ect of vegetation. Ammonium was the most abundant nitrogen nutrient species in pore water, except in the non-vegetated high marsh where nitrate concentration was higher. All nitrogen nutrients were a ected by both flooding and vegetation. Phosphate was always present in pore water at all sites throughout the year and its concentration varied within narrow limits, with no e ect of flooding and greater values always at non-vegetated sites. Our results showed that the variability of the pore water composition within the marsh is greater than the temporal variation, meaning that both tidal flooding and vegetation are important in the dynamics of nutrients and organic matter in the sediment pore water.     

双亲型清水剂处理油田含聚污水

考察了双亲型清水剂QS-03对油田含聚污水处理效果的影响因素,并对其作用机理进行了分析。实验结果表明:当清水剂QS-03的亲水性与亲油性功能基团的摩尔比为2∶1、清水剂加入量大于等于200 mg/L时,处理后污水澄清透明,污水含油量由4 540 mg/L大幅降至26~45 mg/L;在处理温度为50~80℃和污水含油量为3 200~5 800 mg/L的范围内,清水剂QS-03均表现出良好的清水效果,生成的絮体呈松散状,具有良好的流动性。机理分析结果表明,双亲型清水剂QS-03可有效破坏油-水界面双电层、降低界面膜强度,并且与污水中阴离子聚合物的相互作用大幅减弱,因而在高效清水除油的同时可有效避免含聚污水处理中的黏性"含聚油泥"问题。     

Two-stage thermal gasification of polyolefins

Plastic pellets of polyethylene (PE), polypropylene (PP), and polystyrene (PS) were gasified in a two-stage thermal degradation process. The first stage is the conversion of polyolefins to distilled oils using a melting vessel. In the second stage, the oils from the first stage are gasified using a tubular reactor. The distilled oil yields of PE, PP, and PS in the first stage were 84, 89, 92 wt%, respectively, each at 470°C. The total gas yields of PE, PP, and PS in the second stage were 80, 74, and 6.2 wt%, respectively, each at 800°C. The main components of the product gas for PE and PP were methane and olefins such as ethene and propene. Some aromatic oils, including benzene, toluene, and xylene, were also produced as by-products. The amount of carbonaceous residue, or coke, was very low (less than 1 wt%). By dividing the process into two stages, the coking rate was considerably reduced compared with direct gasification of the polyolefins. Received: July 19, 2000 / Accepted: September 17, 2000     

Fluid Mechanics of Serpentine Flow Fields on a Porous Media

Laminar flows are investigated in single and double parallel serpentine channels mounted on a porous media and it is found that significant convective transport occurs in porous media for practical fuel cell conditions. This transport increases with increasing flow Reynolds number, with decreasing land width, and most significantly with increasing channel length.

Increasing the number of parallel channels significantly decreases the pressure drop across the fuel cell, but also significantly decreases the magnitude of convective transport in the porous media. Increased parasitic loads must be put in the context of the change in electrochemical performance.

This paper presents both data and a methodology for beginning to think about flow field design from a hydrodynamic perspective.