Scaling DNAPL migration from the laboratory to the field

A particular problem with the release of dense nonaqueous phase liquids (DNAPLs) into the environment is identifying where the DNAPL is and if it is still moving. This question is particularly important at sites where thousands of cubic meters of DNAPLs were disposed of. To date, results from laboratory models have not been scaled to predict analogous migration at the larger length and time scales appropriate for sites where large volumes of DNAPLs were released. Modified inspectional analysis is a technique for developing scaling relationships through nondimensionalizing the governing equations. It was applied in this study to scale observations of DNAPL migration in a laboratory model to four hypothetical scenarios in the field where large volumes of DNAPL were released. One scenario was compared to a large DNAPL spill site. The length and time scales of DNAPL movement predicted from our analysis are consistent with those predicted from a numerical model of this site. To our knowledge, this is the first application of modified inspectional analysis for release of DNAPLs in a laboratory model. This methodology may prove useful for scaling results from other laboratory investigations of DNAPL migration to field-scale systems.     

Particulate organic matter in the sea: the composition conundrum

As organic matter produced in the euphotic zone of the ocean sinks through the mesopelagic zone, its composition changes from one that is easily characterized by standard chromatographic techniques to one that is not. The material not identified at the molecular level is called "uncharacterized". Several processes account for this transformation of organic matter: aggregation/disaggregation of particles resulting in incorporation of older and more degraded material; recombination of organic compounds into geomacromolecules; and selective preservation of specific biomacromolecules. Furthermore, microbial activities may introduce new cell wall or other biomass material that is not easily characterized, or they may produce such material as a metabolic product. In addition, black carbon produced by combustion processes may compose a fraction of the uncharacterized organic matter, as it is not analyzed in standard biochemical techniques. Despite these poorly-defined compositional changes that hinder chemical identification, the vast majority of organic matter in sinking particles remains accessible to and is ultimately remineralized by marine microbes.     

Determining the role of human substances in the fate of pesticides in the environment

The data presented in this paper emphasize that the behavior and fate of pesticides in the environment is influenced by humic substances. Various methods most frequently used for the characterization of humic substances are discussed. Both humic acid and fulvic acid can solubilize in water certain organic compounds and are important carriers of some pesticides in soil. Humic substances have the potential for promoting the nonbiological degradation of many pesticides. Several methods of bleaching humus color from drinking water, including chlorination, ozonation, and UV-radiation, are described. Finally, the photochemical stability to UV-radiation of certain pesticides in aqueous fulvic acid solution is discussed.     

上海河流氮负荷的年际变化及其水体富营养化的原因探讨

利用1990-2002年水质监测数据,分析了上海河流水体中氮负荷(总氮和氨氮)的年际变化特征：从整体上来看,上海河流水体氮负荷较大,氮污染严重:苏州河、黄浦江下游河段氮负荷明显高于上游河段,市区河流氮负荷明显高于郊区河流;从年际变化上看,苏州河、黄浦江、市区河流(除龙华港)水体历年氮含量有降低趋势,郊区河流水体历年氮含量有增长趋势。在此基础上,从六个方面讨论了造成上海河流水体富营养化的原因,以期为上海市河流综合整治的规划决策提供重要的科学依据。     

Numerical investigation of the flow profiles in the electrically enhanced cyclone

A numerical model for simulation of the electrohydrodynamic flow in an electrically enhanced cyclone is presented. A finite element approach was applied to solve the coupled equations for the positive corona-induced electric field. Three-dimensional simulations of gas flow were carried using Reynolds-Averaged Navier-Stokes equations including the Reynolds stress model and the electrohydrodynamic effect. Numerical results show that the change in the flow profile because of the influence of the corona-induced electric field is apparent when the inlet flow rate is low but is negligible at higher flow rates.     

Determining the role of humic substances in the fate of pesticides in the environment

Abstract

The data presented in this paper emphasize that the behavior and fate of pesticides in the environment is influenced by humic substances. Various methods most frequently used for the characterization of humic substances are discussed. Both humic acid and fulvic acid can solubilize in water certain organic compounds and are important carriers of some pesticides in soil. Humic substances have the potential for promoting the nonbiological degradation of many pesticides. Several methods of bleaching humus color from drinking water, including chlorination, ozonation, and UV‐radiation, are described. Finally, the photochemical stability to UV‐radiation of certain pesticides in aqueous fulvic acid solution is discussed.     

Issues Regarding the Ozone Air Quality Standard and the Design Value

Abstract

Two problems exist in the form and the compliance test of the present National Ambient Air Quality Standard (NAAQS) for ozone. One is the use of the number of exceedances in the form of the standard, which generates confusion and unnecessary complexity when the form is translated to the design value. The other is the requirement of a zero percent chance of violation in the compliance test, which makes the NAAQS considerably more stringent than generally assumed. There are also two sample-size problems in the estimation procedure for the design value. One is the upward creeping of the (n+l)th highest value in n years as n increases from one in the table look-up approach. The other is the infinite-sample-size assumption instead of the number of high-ozone season days per year for the daily maximum ozone concentrations in the distribution fitting approach. Both problems lead to an exaggeration of the design value.

The above problems can be removed in a revised NAAQS by (1) using a statistic that is identical to the design value itself in the form of the standard, (2) defining the design value as an n-year mean of, say, the annual mth highest values rather than the xth highest value in n years, and (3) using a simple compliance test like the t test that compares the design value with the level of the standard, taking into account the year-to-year fluctuation of the annual mth highest values. When the design value of an area is close to the level of the standard, the test provides a natural “too close to call” interval, which adjusts itself with the fluctuation of the annual mth highest values, so that as the fluctuation increases, the ability to assign the compliance status of the area decreases. The inclusion of a “too close to call” interval or category in the standard is critical to reduce the tendency toward ozone attainment flip-flops in areas approaching attainment and to assure that the ozone NAAQS is not more or less stringent than it appears.     

Attempts to probe the ozone layer and the ultraviolet-B levels of the past

To get a proper perspective on the current status of atmospheric ozone, which protects the biosphere from ultraviolet-B (UV-B; 280-315 nm) radiation, it would be of value to know how ozone and UV-B radiation have varied in the past. The record of worldwide ozone monitoring goes back only a few decades, and the record of reliable UV-B measurements is even shorter. Here we review indirect methods to assess their status further back in time. These include variations in the Sun's emission and how these affect the atmosphere, changes in the Earth's orbit, geologic imprints of atmospheric ozone, effects of catastrophic events such as volcanic eruptions, biological proxies of UV-B radiation, the spectral signature of terrestrial ozone in old recordings of star spectra, and the modeling of UV-B irradiance from ozone data and meteorological recordings. Although reliable reconstructions do not yet extend far into the past, there is some hope for future progress.     

On the seasonal variation of the surface ozone in Athens,Greece

An attempt has been made to examine the seasonal variation of the surface ozone mixing ratio in Athens, Greece during the periods 1901–1940 and 1987–1998. The first finding is that in July and August while the daytime surface ozone mixing ratio from the beginning until the end of the 20th century has increased by approximately 1.8 times, the nighttime surface ozone mixing ratio remained approximately at the same level. The second finding is that the increase in the mean daytime mixing ratio during the transition period from winter to summer is equal to the increase in the maximum daytime mixing ratios, whilst the enhancement of the nighttime surface ozone maxima is stronger than that of the nighttime mean surface ozone mixing ratio. Plausible explanation for this finding is given through mechanisms like long-range transport and photochemical processes occurring in the boundary layer, free troposphere and lower stratosphere.     

水处理中含铁废料综合利用的研究进展

回顾了２０余年来我国在水处理中综合利用含铁废料的研究进展，分别评述了副产品硫酸亚铁制备絮凝剂ＰＦＳ的各种方法，废铁屑运用于内电解法水处理和其他含铁泥渣，废酸在水处理中的研究和应用现状，指出含铁废料综合利用中有待于进一步研究的若干问题。     

Effects of oxygen on the release and distribution of phosphorus in the sediments under the light condition

Effects of oxygen on the release and distribution of phosphorus (P) in the sediments in the presence of light were investigated, using sediment cores and overlying water from Lake Taihu, in China. The results show that P can be released from sediments to the overlying water in both anoxic and aerobic conditions. But more P was released in the anoxic condition. The transformation of P between various fractions in the sediments was observed during the release experiments. Concentrations of Ca-bound P and organic P in the sediments decreased in both conditions, but Fe/Al-bound P increased in the aerobic condition. The decrease of total P and P fractions in the sediments is consistent with the accumulative increase in quantity (AIQ) of total P (TP) in the overlying water, but is contrary with the AIQ of dissolved inorganic P. This is due to the uptake of algae by the dissolved inorganic P. Total nitrogen in the sediments in the anoxic condition was lower than that in the aerobic condition, and pH in the overlying water increased in the anoxic condition.     

Backyard of the rich north: the climate change-related vicious circle of the Arctic zone

The Arctic zone is full of controversies, unknowns, contrasts, and challenges. The following example is enlightening. Saudi Arabia is a country that has been considered to have almost unlimited possibilities because of its enormous oil earnings. The country has US$60 thousand million purchasing power parity oil income each year for its mere 22 million inhabitants. Astonishingly, the Arctic zone's income from oil, gas, and minerals is at least as large as that of Saudi Arabia, modestly estimated, but the Arctic has less than 4 million people. Most money, however, flows away from the tundra, yet social and environmental problems remain there. A part of the side effect of consuming these resources-largely fossil fuels-returns to the Arctic in the form of greenhouse warming and all its consequences. The Arctic zone now warms at approximately double the rate of the world average.     

The Costs of Meeting the Environmental Objectives for the Baltic Sea: A Review of the Literature

The environmental targets of the recently agreed Baltic Sea Action Plan (BSAP) targets are likely associated with a considerable cost, which motivates a search for low-cost policies. The following review shows there is a substantial literature on cost-efficient nutrient reduction strategies, including suggestions regarding low-cost abatement, but actual policies at international and national scale tend to be considerably more expensive due to lack of instruments that ensure a cost-efficient allocation of abatement across countries and sectors. Economic research on the costs of reducing hazardous substances and oil spill damages in the Baltic Sea is not available, but lessons from the international literature suggest that resources could be used more efficiently if appropriate analysis is undertaken. Common to these pollution problems is the need to ensure that all countries in the region are provided with positive incentives to implement international agreements.     

Estimating the hydraulic properties of the fracture network in a sandstone aquifer

The potential hydraulic behaviour of the fracture network in a major Triassic sandstone aquifer in the UK has been evaluated. The properties of the fracture network were determined using results from detailed scan line surveys at 10 sites, television and geophysical borehole logging, and packer testing. Six sets of discontinuities common to all sites were identified and statistically characterised (dip, strike, orientation, density, size, and estimated transmissivity). A discrete fracture network model was then used stochastically to investigate the properties of the network. In general, the network is poorly connected: it is estimated that 9% of the discontinuities intersecting boreholes are transmissive. The hydraulic behaviour of the network is generally dominated by one sub-horizontal bedding plane fracture set, although when present, a relatively infrequent north-south striking, sub-vertical set modifies the bulk flow properties significantly. Ignoring this latter set, the network's minimum representative volume is about 35 x 35 x 35 m. The upscaled permeability is anisotropic, being typically 23 times greater in the horizontal than in the vertical. Tortuosity in the north-south direction is around 1.6.     

Study of the SRF-derived ashes melting behavior and the effects generated by the optimization of their composition on the furnaces energy efficiency in the incineration plants

As regards the incineration process of the urban solid waste, the composition correct management allows not only the valorization of precise civil and industrial groups of waste as alternative fuels but also a considerable increase of the furnace work temperature leading to a remarkable improvement of the related energy efficiency. In this sense, the study of the melting behavior of ashes deriving from several kinds of fuels that have to be processed to heat treatment is really important. This approach, indeed, ensures to know in depth the features defining the melting behavior of these analyzed samples, and as a consequence, gives us the necessary data in order to identify the best mixture of components to be incinerated as a function of the specific working temperatures of the power plant. Firstly, this study aims to find a way to establish the softening and melting temperatures of the ashes because they are those parameters that strongly influence the use of fuels. For this reason, in this work, the fusibility of waste-derived ashes with different composition has been investigated by means of the heating microscope. This instrument is fundamental to prove the strict dependence of the ashes fusion temperature on the heating rate that the samples experienced during the thermal cycle. In addition, in this work, another technological feature of the instrument has been used allowing to set an instantaneous heating directly on the sample in order to accurately reproduce the industrial conditions which characterize the incineration plants. The comparison between the final results shows that, in effect, the achievement of the best performances of the furnace is due to the a priori study of the melting behavior of the single available components.     

Recent trends of the emission characteristics from the road construction industry

Bitumen is a black, thermoplastic, hydrocarbon material derived from the processing of crude oil. At ambient temperature, bitumen is solid and does not present any health/environmental risks. This is one of the main reasons that bitumen is widely used for road construction all over the world. But during manufacturing/modification according to its application, storage, transportation, and use of bitumen is heated giving off various hydrocarbons emissions. In recent years, there has been increasing interest in investigating the potential of bitumen emissions to cause health effects. This is mainly because of the reason that bitumen has small amount of poly-aromatic hydrocarbons, along with some other volatiles like benzene, toluene, etc., which are known to be carcinogenic in nature. Thus, assessment of the emission characteristics and health hazards of bitumen fumes may have far reaching industrial economic and public health implications. In this review, we will discuss about the emission characteristics from bitumen, asphalts, or road construction, which is mainly contributed by bitumen fumes. Sampling strategies and analytical methods employed are also described briefly.     

Estimation of the net air-sea flux of ammonia over the southern bight of the North Sea

Measurements of airborne gaseous ammonia and total dissolved ammonium in sea water determined on cruises on the North Sea have been used to calculate net fluxes of ammonia between air and sea. The system is finely balanced with the majority of net fluxes from air to sea, but some periods occur when the sea becomes a net source of ammonia in air. Examination of the field data suggests that the main factor determining the direction of flux is the airborne ammonia concentration, which when elevated causes ammonia deposition to the sea. It is calculated that ammonia deposition to the southern bight of the North Sea (below 56°N) amounts to 7.6 x 103 tonnes N per year, about one-half of an earlier upper limit estimate. Comparison with studies from the Pacific Ocean, in which the sea acts as a source of atmospheric ammonia, reveals that the major differences arise from much higher concentrations of airborne ammonia in the North Sea atmosphere caused by advection from adjacent land.     

On the forming mechanism of the cleaning airflow of pulse-jet fabric filters

To reveal the formation mechanism of a pulse-jet airflow’s cleaning effect in a filter bag, a theoretical model is built by using the theory of the gas jet and unitary adiabatic flow according to given specifications and dimensions of the bags and resistance characteristics of the cloth and dust layer. It is about the relationship between cleaning system structure and operating parameters. The model follows the principle that the flow and kinetic energy of jet flow injected into a filter bag should be consistent with the flow of cleaning airflow in the bag and the pressure drop flowing through the filter cloth and dust layer. The purpose of the model is to achieve the peak pressure of cleaning airflow, which dominates the effect of the pulse-jet cleaning process. The cleaning system structure includes air pressure in the nozzle, structure and size of nozzle, exit velocity of nozzle, jet distance, and diameter of jet cross section. Based on the condition of the cleaning system structure and operating parameters established by using the theoretical model, Fluent software is applied to carry out a numerical simulation of the jet airflow field at the nozzle’s outlet, jet airflow field between nozzle and bag top, and cleaning airflow field in the filter bag. Experimental results are used to verify the reliability of the theoretical model. They are obtained in a pilot-scale test filter with a single bag, with length 2 m and in general full-scale dimensions of the cleaning system. The results show that when any rectification measure is not installed at the bag opening, the cross-sectional area covered by the jet gas is hardly sufficient to cover the entire area of the bag opening. A large portion of the gases injected into the filter bag will overflow reversely upward from the edge due to pressure differences between the upper area and lower area inside the bag opening. This led to a serious shortage of the cleaning airflow and ar limited increase in static pressure. When a venturi-type rectifier tube is installed at the bag opening, the jet flow is converted to funnel flow for which the cross-section velocity distribution is more uniform at the throat of the rectifier tube due to the guided effects of the upper tapered pipe. Then it is transited to stressful flow below the bag opening via rectified effects of the lower dilated pipe. The results show that the gap between the static pressure of gas in the bag and the expected value is significantly reduced. The theoretical value of the nozzle diameter is enlarged to compensate for two aspects of adverse effects of cleaning airflow and energy. This is because the flow is not a purely free-form jet from the nozzle to the entrance of the rectifier tube and because the gas suffers from local resistance while flowing through the rectifier tube. The numerical simulation and experiment show that the peak pressure of cleaning airflow in the filter bag is able to reach the expected value. The results confirm that the mechanism of the pulse-jet cleaning airflow and the calculation method of the pulse-jet cleaning system structure and operating parameters offered in this study are correct. The study results provide a scientific basis for designing the system of pulse-jet fabric filters.

Implications: Pulse-jet cleaned fabric filters are commonly used for air pollution control in many industries. Pulse-jet cleaning is widely used for this purpose as it enables frequent cleaning while the filter is operating. However, the theoretical system of the forming mechanism of the pulse-jet cleaning has not formed so far. This indicates the theoretical model plays an important role in designing effective pulse-jet cleaned fabric filters.