加速溶剂萃取技术及其在环境分析中的应用

加速溶剂萃取技术是一项新颖的样品前处理技术，通过升高温度与压力结合使用有机溶剂，可快速，有效地由基体中萃取各种欲测物。本文系统地阐述了该技术的基本原理，各种影响因子及其在环境分析中的应用。该法适用于固体和半固体样品的前处理。     

上海市防灾救灾系统管理存在的问题及对策

对上海当前防灾救灾系统管理中存在的问题进行了分析，并且提出了相应的对策，对上海及其它城市的防灾救灾系统管理体系的改进与完善有一定的借鉴作用。     

The acetochlor registration partnership: prospective ground water monitoring program

The Acetochlor Registration Partnership conducted a prospective ground water (PGW) monitoring program to investigate acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)-acetamide] transport to ground water at eight sites. The distribution of soil textures among these sites was weighted toward coarser soil types, while also including finer-textured soils that dominate most corn (Zea mays L.)-growing areas of the United States. Each site consisted of a 1.2-ha test plot adjacent to a 0.2-ha control plot. Suction lysimeters and monitoring wells were installed at multiple depths within each test and control plot to sample soil-pore water and near-surface ground water. Irrigation was applied to each site during the growing season to ensure water input of 110 to 200% of average historical rainfall. Acetochlor dissipated rapidly from surface soils at all sites with a DT(50) (time for 50% of the initial residues to dissipate) of only 3 to 9 d, but leaching was not an important loss mechanism, with only 0.25% of the 15,312 soil-pore water and ground water samples analyzed containing parent acetochlor at or above 0.05 microg L(-1). However, quantifiable residues of a soil degradation product, acetochlor ethanesulfonic acid, were more common, with approximately 16% of water samples containing concentrations at or above 1.0 microg L(-1). A second soil degradation product, acetochlor oxanilic acid, was present at concentrations at or above 1.0 microg L(-1) in only 0.15% of water samples analyzed. The acetochlor PGW program demonstrated that acetochlor lacks the potential to leach to ground water at detectable concentrations, and when applied in accordance with label restrictions, is unlikely to move to ground water at concentrations hazardous to human health.     

Phosphorus losses to water from lowland rice fields under rice-wheat double cropping system in the Tai Lake region

To assess P losses to surface water by runoff during the rice season and by drainage flow during the winter wheat season, serial field trials were conducted in different types of paddy soils in the Tai Lake Region (TLR) during 2000 and 2001. Four P application rates were set as 0 (CK), 30, 150, and 300 kg P/hm2 for flooded rice trials and 0 (CK), 20, 80, 160 kg P/hm2 for winter wheat trials respectively. Field experiments were done in two locations with a plot size of 30 m2 and four replications in a randomized complete block design. A simplified lysimeter was installed for each plot to collect all the runoff or drainage flow from each event. Total P (TP) losses to surface water during rice season by runoff flow from four treatments were 150 (CK), 220 (T30), 395 (T150), 670 (T300) g P/ hm2 in year 2000, and 298, 440, 1828, 3744 g P/hm2 in year 2001 respectively in Wuxi station, here the soil is permeable paddy soil derived from loam clay deposit. While the losses were 102, 140, 210, 270 in year 2000, and 128, 165, 359, 589 g P/hm2 in year 2001 respectively in Changshu station, here the soil is waterlogged paddy soil derived from silt loam deposit. During the winter wheat season, total P lost from the fields by drainage flow in the four treatments were 253 (CK), 382 (T20), 580 (T89), 818 (T160) g P/hm2 in year 2000--2001, and 573.3, 709.4, 1123.2, 1552.4 g P/hm2 in year 2001--2002 at the Wuxi station. While these were 395.6, 539.1, 1356.8, 1972.1 g P/hm2 in year 2000--2001, and 811.5, 1184.6, 3001.2, 5333.1 g P/hm2 in year 2001--2002 at the Changshu station. Results revealed that P fertilizer application rates significantly affected the TP concentrations and TP loads in runoff during the rice season, and by drainage flow during the winter wheat season. Both TP loads were significantly increased as the P application rate increases. The data indicate that TP losses to surface water were much higher during the winter wheat season than during the rice season in two tested sites. The data also reveal that the annual precipitation and evaporation rate affected the soil P losses to surface water significantly. Year 2000 was relatively dried with higher evaporation thus P losses to water by both runoff and drainage flow were less than in year 2001 which was a relatively wet year with lower evaporation. Results indicate that texture, structure of the soil profile, and field construction (with or without ridge and deep drains) affected soil P losses to surface water dramatically. Annual possible TP lost to water at the application rate of 50 kg P/hm2 year tested in TLR were estimated from 97 to 185 tones P from permeable paddy soils and 109-218 tones P from waterlogged paddy soils. There was no significant difference of TP lost between the CK and the T50 treatments in both stations, which indicate that there is no more TP lost in field of normal P fertilizer application rate than in control field of no P fertilized. Much higher TP lost in runoff or drainage flow from those other P application rates treatments than from the T50 treatment, which suggest that P losses to surface water would be greatly increasing in the time when higher available P accumulation in plough layer soil in this region.     

Urban Wastewater Treatment and Reclamation for Agricultural Irrigation: The situation in Morocco and Palestine

As freshwater becomes increasingly scarce due to population growth, urbanisation and, probably, climate change, the use of wastewater in agriculture, aquaculture, groundwater recharge and in other areas will increase. In some cases, wastewater is the only water resource available to poor, subsistence-level farming communities. Although there are benefits to using wastewater in agriculture—such as better nutrition and food security for many households—uncontrolled use of wastewater is frequently associated with significant negative human health impacts. These health impacts can be minimized when good management practices are implemented. In this paper the existing situation, in relation to water resources availability, wastewater treatment and reuse in Morocco and Palestine, is presented.     

Soybean-Oil-Based Polyisocyanurate Rigid Foams

Polyisocyanurate foams were prepared from polymeric 4,4-diphenylmethane diisocyanate (MDI), soy polyol and polypropylene oxide polyol by varying isocyanate index from 110 to 350. The higher isocyanate index produced polyisocyanurate foams with higher thermal stability, improved flame resistance, tensile strength, higher modulus, and higher glass transition. Soy-based foams displayed better thermal stability, lower flammability, higher rigidity (modulus) and higher compression strength than those based on the propylene oxide polyols of the same molecular weight and functionality.     

Uncertainty Analysis In Dissolved Oxygen Modeling in Streams

Uncertainty analysis in surface water quality modeling is an important issue. This paper presents a method based on the first-order reliability method (FORM) to assess the exceedance probability of a target dissolved oxygen concentration in a stream, using a Streeter–Phelps prototype model. Basic uncertainty in the input parameters is considered by representing them as random variables with prescribed probability distributions. Results obtained from FORM analysis compared well with those of the Monte Carlo simulation method. The analysis also presents the stochastic sensitivity of the probabilistic outcome in the form of uncertainty importance factors, and shows how they change with changing simulation time. Furthermore, a parametric sensitivity analysis was conducted to show the effect of selection of different probability distribution functions for the three most important parameters on the design point, exceedance probability, and importance factors. Note: This version was published online in June 2005 with the cover date of August 2004.     

Determination of depleted uranium in environmental samples by gamma-spectroscopic techniques

The military use of depleted uranium initiated the need for an efficient and reliable method to detect and quantify DU contamination in environmental samples. This paper presents such a method, based on the gamma spectroscopic determination of 238U and 235U. The main advantage of this method is that it allows for a direct determination of the U isotope ratio, while requiring little sample preparation and being significantly less labor intensive than methods requiring radiochemical treatment. Furthermore, the fact that the sample preparation is not destructive greatly simplifies control of the quality of measurements. Low energy photons are utilized, using Ge detectors efficient in the low energy region and applying appropriate corrections for self-absorption. Uranium-235 in particular is determined directly from its 185.72 keV photons, after analyzing the 235U-226Ra multiplet. The method presented is applied to soil samples originating from two different target sites, in Southern Yugoslavia and Montenegro. The analysis results are discussed in relation to the natural radioactivity content of the soil at the sampling sites. A mapping algorithm is applied to examine the spatial variability of the DU contamination.     

Comparison of different methods for uranium determination in water

Photometry, laser photometry, liquid scintillation (LSC), gamma spectrometry and alpha spectrometry were used for estimating waterborne uranium concentration. The chemical procedures applied were pre-concentration, liquid extraction, chromatographic resin extraction and precipitation. Our results show that laser photometry is an easy and accurate method capable of estimating low uranium concentrations, parts of micrograms per litre. It is not applicable for higher concentrations, difficult water matrixes and isotope determination. The classical photometry is complementary, resolving the problem related to high concentrations, practically up to 10 mg/l. Alpha and gamma spectrometry resolve the problem of precise isotope determination, but with the disadvantage of hard chemical preparation and long measurement times. An intermediate method is LSC, with the problem of isotope estimation, due to poor energy resolution.     

基于PLC的企业铁路道口安全控制系统研究

企业铁路是企业生产的重要组成部分,然而企业铁路道口的安全问题一直较为突出,主要是因为目前所用的道口安全控制系统在灵活性和可靠性方面难以协调一致.针对这种状况,提出了基于PCL的铁路道口安全控制系统,研究了PCL安全控制系统的实现方案,并用实例证明了它的科学性和可行性.