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91.
Photolysis of 14C-sulfadiazine in aqueous solution under simulated sunlight followed first-order kinetics. The impact of H2O2, humic acid, fulvic acid and acetone to enhance the photodegradation of sulfadiazine (SDZ) was studied. Six photoproducts, 4-OH-SDZ, 5-OH-SDZ, N-formyl-SDZ, 4-[2-iminopyrimidine-1(2H)-yl] aniline, 2-aminopyrimidine, and aniline were identified. Extrusion of SO2 was found to be the main degradation process during irradiation. These photoproducts can occur in water and soil upon sunlight exposure, when soil is treated with SDZ contained in manure. Due to photodegradation the experimental half-life of the SDZ in water was 32h and in the presence of photosensitizers the half-life values were 19.3-31.4h, 17.2-31.4h, 12.6-29.8h, and 3.8-30.7h for H2O2, humic acid, fulvic acid, and acetone, respectively depending on the concentration of the photosensitizers. The presence of photosensitizers markedly reduced SDZ persistence, indicating that indirect photolytic processes are important factors governing the photodegradation of SDZ in aqueous environments. Investigation revealed further persistence behavior of SDZ in manure. The half-life value of SDZ in manure was 158h. 相似文献
92.
93.
Characterizing effects of uncertainties in MSW composting process through a coupled fuzzy vertex and factorial-analysis approach 总被引:1,自引:0,他引:1
A coupled fuzzy vertex and factorial-analysis approach was developed in this study for systematically characterizing effects of uncertainties in a municipal solid waste composting process. A comprehensive composting process model was also embedded into the system framework and used to address substrate decomposition and biomass growth, as well as the interactions between moisture contents, temperatures, and oxygen concentrations. The applicability of the proposed method was verified through a custom-made pilot-scale composting system. Results from fuzzy simulation indicated that the fuzzy vertex method could effectively communicate implicit knowledge into dynamic simulations and thus provide valuable information for enhancing composting process control under uncertainty. The factorial analysis was effective in quantifying the proportion to which the uncertainty of each single or interactive effect of model parameters contributes to the overall uncertainty of the system outcomes. Thus, sensitive parameters that may lead to errors or unreasonable predictions can be determined. The proposed study system could not only be used in characterizing combined effects of uncertainties for composting processes, but was also applicable to many other environmental modelling systems. 相似文献
94.
L. Bdard-Tremblay L. Fang L. Bauwens Z. Cheng A.V. Tchouvelev 《Journal of Loss Prevention in the Process Industries》2008,21(2):154-161
An accidental hydrogen release within an equipment enclosure may result in the presence of detonable mixture in a confined environment. From a safety standpoint, it is then useful to assess the potential for damage. In that context, numerical simulation of the sequence of events subsequent to detonative ignition provides a useful tool, although with obvious limitations. This article describes the procedure, summarizes two case studies, and reviews the limitations. First, a hydrogen dispersion pattern is obtained from numerical simulation of dispersion, using a commercial package designed primarily for incompressible flow. This dispersion cloud is then used as the initial condition in an inviscid, compressible, reactive flow simulation. To force detonative ignition, a sufficiently large amount of energy is deposited in a small region that corresponds to the ignition location. Chemistry is modeled using a single step Arrhenius model. Because the wave thickness is small compared with the computational domain, a fine mesh is needed, limiting the practicality of the process to two-dimensional geometries. This is the most significant limitation; it is conservative. The two cases described in the paper include an electrolyzer, in which a small release occurs, leading potentially to some damage to the enclosure, and a reformer, in which the consequences are potentially more serious. 相似文献
95.
Water produced by advanced treatment of a groundwater was evaluated to determine the amount of DBPs (Disinfection By-Products) including trihalomethanes (THMs). Both Gas Chromatography (GC) and Gas Chromatography/Mass Spectrometry (GS/MS) were adopted for detection and identification of DBPs such as trihalomethanes (THMs), halo-acetic acids (HAAs) and aldehydes. Two disinfection modes (ozonation followed by chlorination and chlorination alone) were compared to determine the DBPs generation. The mutagenitic acivity of ozonated water, chlorinated water after ozonation and potable water was assessed using the Ames test. Chloroform, dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) were the main constituents of THMs and HAAs, respectively. THMs accounted for more than 85% of all DBPs measured, whereas haloacetic acids accounted for around 14%. Ozonation followed by chlorination proved to be better in terms of THMs and HAAs control. The combined system produced 28.3% less DBPs compared to chlorination alone. Ozonation was found capable of reducing mutagenic matter in the groundwater by 54.7%. The combined system also resulted in water with no mutagenicity. 相似文献
96.
The impact of motorcycle traffic on soil and vegetation of stabilized coastal dunes, Israel 总被引:1,自引:0,他引:1
This study aimed to assess the response of soil and annual plant vegetation of stabilized coastal dunes in Israel, to varying
intensities of off-road motorcycle (ORM) traffic, and to assess their resistance and resilience to such a disturbance. A standard
experimental procedure that included 0, 20, 50, 100 and 200 ORM straight passes and 150 ORM turn passes was used. Plant ground
cover, mean plant height, species richness, species diversity, soil penetrable depth, organic matter and moisture contents
were measured on several dates within a period of 372 days after the experiment. Results have shown that: (1) ORM passes had
a significant immediate impact on annual plants that increased with traffic intensity. The impact on the soil was detected
only as an increase of penetrable depth. (2) The maximum impact on annual plants was observed in the wheel ruts and turn areas.
The impact on the area between the wheel ruts and on the margins outside the wheel ruts was indirect and smaller. (3) Annual
plant ground cover and mean plant height were less sensitive parameters than species richness and species diversity for determining
the impact of ORM traffic on the area. (4) One year after the experiment, soil and annual plant vegetation in all passes were
very similar to their pre-experimental condition. This indicates high resilience and recovery potential of the Mediterranean
stabilized coastal dune ecosystem to ORM disturbance. 相似文献
97.
Starch-gel electrophoresis of allozymes was used to differentiate the two red mullet species (Mullus barbatus L. and M. surmuletus L.) in the Mediterranean Sea and, further, to investigate the genetic stock structure of M. barbatus in the eastern Mediterranean area. Twenty putative enzyme-coding loci were examined in eight M. barbatus samples caught in the Aegean and Ionian Seas (Greece) and in the Gulf of Lion (France), and two M. surmuletus samples caught in the Aegean and Gulf of Lion. A high degree of genetic polymorphism was found in both species. Species-specific
electrophoretic patterns were found in PGI* and PGM*. Estimates of variance of allele frequencies among samples (F
ST) and 2 analyses both revealed significant differences (P < 0.05) among the M. barbatus samples. Most of the genetic variation was among samples regardless of region. The mean value of Nei's genetic distance between
the two species was 0.329. Genetic distance among M. barbatus samples was low (maximum Nei's D = 0.012), with the sample from Platania differing most from other M. barbatus samples. This is probably be due to founder effects existing at this area. These results suggest that allozyme analysis may
provide important information on the genetic structure of the red mullet to ensure sustainable management of this species.
Received: 7 May 1997 / Accepted: 13 October 1997 相似文献
98.
In this study, an interval-fuzzy two-stage chance-constrained integer programming (IFTCIP) method is developed for supporting
environmental management under uncertainty. The IFTCIP improves upon the existing interval, fuzzy, and two-stage programming
approaches by allowing uncertainties expressed as probability distributions, fuzzy sets, and discrete intervals to be directly
incorporated within a general mixed integer linear programming framework. It has advantages in uncertainty reflection, policy
investigation, risk assessment, and capacity-expansion analysis in comparison to the other optimization methods. Moreover,
it can help examine the risk of violating system constraints and the associated consequences. The developed method is applied
to the planning for facility expansion and waste-flow allocation within a municipal solid waste management system. Violations
of capacity constraints are allowed under a range of significance levels, which reflects tradeoffs between the system cost
and the constraint-violation risk. The results indicate that reasonable solutions for both binary and continuous variables
have been generated under different risk levels. They are useful for generating desired decision alternatives with minimized
system cost and constraint-violation risk under various environmental, economic, and system-reliability conditions. Generally,
willingness to take a higher risk of constraint violation will guarantee a lower system cost; a strong desire to acquire a
lower risk will run into a higher system cost. 相似文献
99.
Fourteen (14) characters from six (6) water samples collected from springs, ponds, and streams located in Lower Cretaceous sedimentary area of Afikpo Basin have been analyzed. These include pH, turbidity, conductivity, total dissolved solid, hardness, Fe2+, Ca2+, Mg2+, K+, NO3 ?, Cl?, SO4 2?, and Na+. These sediments, which are Turonian and Coniacian in age, are subdivided into two by a basic rock dyke. Results of the analyses show clearly that the Turonian sediments, intruded by dolerite, have net Fe2+, HCO3 ?, Ca2+, Mg2+, Mn2+, Cl?, and SO4 2? concentration while those from the younger Coniacian sediment have net higher amounts of K+, Na+, and Mn2+. The overriding mafic minerals in the basic intrusive rock possibly led to higher leaching into ground water system near it. On the other hand, the presence of feldsparthic to kaolinitic sands of the younger Coniacian units led to higher K+ and Na+ matter in the water from these zones. The formations dip away from the older sediments. Concentrations of these characters are within acceptable drinking water standards by World Health Organization but noticeable anomalous zones for Fe2+, Mg2+, and Ca2+ are zones of basic rock suites. Areas with greater Na+ and K+ are traceable to sandy units. It is thus concluded that more analysis of surface, subsurface, and pond water samples can be utilized for minerals search and geological mapping. At this stage, it forms a veritable reconnaissance tool. 相似文献
100.
Z. Zlatev I. Dimov Tz. Ostromsky G. Geernaert I. Tzvetanov A. Bastrup-Birk 《Environmental Modeling and Assessment》2001,6(1):35-55
In order to help guide air pollution legislation at the European level, harmful air pollution effects on agriculture crops and the consequent economic implications for policy have been studied for more than a decade. Ozone has been labeled as the most serious of the damaging air pollutants to agriculture, where growth rates and consequently yields are dramatically reduced. Quantifying the effects has formed a key factor in policymaking. Based on the widely held view that AOT40 (Accumulated exposure Over Threshold of 40 ppb) is a good indicator of ozone-induced damage, the Danish Eulerian Model (DEM) was used to compute reduced agriculture yields on a 50 km×50 km grid over Europe. In one set of scenarios, a ten year meteorological time series was combined with realistic emission inventories. In another, various idealized emission reduction scenarios are applied to the same meteorological time series. The results show substantial inter-annual variability in economic losses, due in most part to meteorological conditions which varied much more substantially than the emissions during the same period. It is further shown that, taking all uncertainties into account, estimates of ozone-induced economic losses require that a long meteorological record is included in the analysis, for statistical significance to be improved to acceptable levels for use in policy analysis. In this study, calculations were made for Europe as a whole, though this paper presents results relevant for Denmark. 相似文献