Efficient retrieval of vegetation leaf area index and canopy clumping factor from satellite data to support pollutant deposition assessments

Canopy leaf area index (LAI) is an important structural parameter of the vegetation controlling pollutant uptake by terrestrial ecosystems. This paper presents a computationally efficient algorithm for retrieval of vegetation LAI and canopy clumping factor from satellite data using observed Simple Ratios (SR) of near-infrared to red reflectance. The method employs numerical inversion of a physics-based analytical canopy radiative transfer model that simulates the bi-directional reflectance distribution function (BRDF). The algorithm is independent of ecosystem type. The method is applied to 1-km resolution AVHRR satellite images to retrieve a geo-referenced data set of monthly LAI values for the conterminous USA. Satellite-based LAI estimates are compared against independent ground LAI measurements over a range of ecosystem types. Verification results suggest that the new algorithm represents a viable approach to LAI retrieval at continental scale, and can facilitate spatially explicit studies of regional pollutant deposition and trace gas exchange.     

PAFC对水体中持久性有机污染物PFOA的混凝效果

针对含全氟辛酸(PFOA)的工业废水及应对PFOA的污染突发事件,采用PAFC及其复配粘土矿物凹凸棒和沸石进行混凝实验,并对几个影响因素进行了考察。结果表明,在PAFC的最佳投加量10 mg/L时,PFOA和浊度的去除率分别达到70.25%和99.42%,PAFC混凝处理PFOA的效果优于PAC;pH值对PAFC去除PFOA有一定的影响,当pH大于6时有利于PFOA的去除;PFOA和浊度的去除率随原始浊度的增加而增加;活性炭、盐酸改性凹凸棒、盐酸改性沸石、CT-MAB改性的沸石复配PAFC均可提高PFOA的去除率;改性处理后的沸石应用于PFOA的处理中,有望降低处理成本。     

Two methods to determine plant responses to pollutant mixtures

Two methods are described which enable better interpretation of the effects of pollutant mixtures on plants. The first method is a statistical procedure in which treatment components are partitioned into single degrees of freedom comparisons. With this technique, joint action of pollutants can be calculated. Trends in response, such as linear or quadratic, can be observed for quantitative data. Also, the nature of interactions in experiments of a factorial design can be determined. The second procedure described is growth analysis. Growth analysis provides a method for determination of the effects of pollutants on physiological processes, such as relative rates of growth, carbon allocation and leaf expansion. Advantages, disadvantages and applications of both methods are discussed.     

Simplified Pearson distributions applied to air pollutant concentration

Determination of Pearson system of distribution is proposed by using first three moments of the data. The actual distribution of air pollutant concentration observed at two typical areas is well approximated by Type VI distribution (Beta distribution of the second kind). About half of the data observed around an isolated source show convex curve when the cumulative frequencies are drawn on the probability paper of log-normal distribution which belongs to Type VI of Pearson system. Errors of the distributions are evaluated between log-normal and Type VI of Pearson system.     

Development of a fuzzy-stochastic nonlinear model to incorporate aleatoric and epistemic uncertainty

Site uncertainties significantly influence groundwater flow and contaminant transport predictions. Aleatoric and epistemic uncertainty are both identified in site characterization and represented using proper uncertainty theories. When one theory best represents one parameter whereas a different theory may be more suitable for another parameter, the hybrid propagation of aleatoric (random) and epistemic (nonrandom) uncertainties will occur. The computational challenges of joint propagation of aleatoric and epistemic uncertainty through groundwater flow and contaminant transport models are significant. A fuzzy-stochastic nonlinear model was developed in this paper to incorporate these two types of uncertain site information and reduce the computational cost. The results show that (1) the computational cost using the nonlinear model is reduced compared with that of using the sparse grid algorithm and Monte Carlo methods; (2) the uncertainty of hydraulic conductivity (K) significantly influences the water head and solute distribution at the observation wells compared to other uncertain parameters, such as the storage coefficient and the distribution coefficient (K_d); and (3) the combination of multiple uncertain parameters substantially affects the simulation results. Neglecting site uncertainties may lead to unrealistic predictions.     

Ecological risk assessment of pollutant chemicals: extinction risk based on population-level effects

The extinction probability is one of the most useful endpoints that are utilized in conservation biology. A parallel approach is advocated for the ecological risk assessment of chemical pollutants. The presented framework estimates extinction probability induced by pollutant chemicals in order to evaluate ecological hazards of pollution, and is applicable to any biological community (aquatic or terrestrial). The analytical framework, which is based on stochastic population dynamics theory, is briefly explained. The extinction risk estimation is feasible if ecotoxicological data concerning pollutant effects on population growth rate of organisms (the intrinsic rate of natural increase), and if environmental exposure concentration is provided. Tentative risk estimation was made for some agrochemicals and surfactants on zooplankton populations (Daphnia) as target organisms.     

蚯蚓生态滤池中蚯蚓与植物对污水净化的作用评估

构建具有不同蚯蚓和植物配置的4个单级蚯蚓生态滤池,依次编号为A(无蚯蚓无植物)、B(有蚯蚓无植物)、C(有蚯蚓栽种芦苇)和D(有蚯蚓栽种水生鸢尾)。通过比较4个滤池在6个月实验期间对化学需氧量(COD)和总氮(TN)的去除效率,系统分析蚯蚓和植物对滤池去除污染物的影响。实验分2个阶段进行:5月上旬至9月上旬,滤池进水碳氮比恒定为6;9月中旬至11月中旬,滤池每周进水碳氮比交替为3、6、9。研究结果表明,蚯蚓对滤池去除COD有一定的促进作用,且作用强度显著受到进水碳氮比的影响。植物的存在与种类对滤池去除COD效率没有显著影响。蚯蚓和植物对滤池的TN去除效率都没有显著影响。滤池进水的碳氮比是显著影响滤池去除TN效率的主要因素。     

Tracer studies to characterize the effects of roadside noise barriers on near-road pollutant dispersion under varying atmospheric stability conditions

A roadway toxics dispersion study was conducted at the Idaho National Laboratory (INL) to document the effects on concentrations of roadway emissions behind a roadside sound barrier in various conditions of atmospheric stability. The homogeneous fetch of the INL, controlled emission source, lack of other manmade or natural flow obstructions, and absence of vehicle-generated turbulence reduced the ambiguities in interpretation of the data. Roadway emissions were simulated by the release of an atmospheric tracer (SF₆) from two 54 m long line sources, one for an experiment with a 90 m long noise barrier and one for a control experiment without a barrier. Simultaneous near-surface tracer concentration measurements were made with bag samplers on identical sampling grids downwind from the line sources. An array of six 3-d sonic anemometers was employed to measure the barrier-induced turbulence. Key findings of the study are: (1) the areal extent of higher concentrations and the absolute magnitudes of the concentrations both increased as atmospheric stability increased; (2) a concentration deficit developed in the wake zone of the barrier with respect to concentrations at the same relative locations on the control experiment at all atmospheric stabilities; (3) lateral dispersion was significantly greater on the barrier grid than the non-barrier grid; and (4) the barrier tended to trap high concentrations near the “roadway” (i.e. upwind of the barrier) in low wind speed conditions, especially in stable conditions.     

Relative importance of school bus-related microenvironments to children's pollutant exposure

Real-time concentrations of black carbon, particle-bound polycyclic aromatic hydrocarbons, nitrogen dioxide, and fine particulate counts, as well as integrated and real-time fine particulate matter (PM2.5) mass concentrations were measured inside school buses during long commutes on Los Angeles Unified School District bus routes, at bus stops along the routes, at the bus loading/unloading zone in front of the selected school, and at nearby urban "background" sites. Across all of the pollutants, mean concentrations during bus commutes were higher than in any other microenvironment. Mean exposures (mean concentration times time spent in a particular microenvironment) in bus commutes were between 50 and 200 times greater than those for the loading/unloading microenvironment, and 20-40 times higher than those for the bus stops, depending on the pollutant. Although the analyzed school bus commutes represented only 10% of a child's day, on average they contributed one-third of a child's 24-hr overall black carbon exposure during a school day. For species closely related to vehicle exhaust, the within- cabin exposures were generally dominated by the effect of surrounding traffic when windows were open and by the bus's own exhaust when windows were closed. Low-emitting buses generally exhibited high concentrations only when traveling behind a diesel vehicle, whereas high-emitting buses exhibited high concentrations both when following other diesel vehicles and when idling without another diesel vehicle in front of the bus. To reduce school bus commute exposures, we recommend minimizing commute times, avoiding caravanning with other school buses, using the cleanest buses for the longest bus routes, maintaining conventional diesel buses to eliminate visible emissions, and transitioning to cleaner fuels and advanced particulate control technologies as soon as possible.     

V-doped TiO2 photocatalysts and their application to pollutant degradation

Environmental Science and Pollution Research - V-doped TiO2 materials (0.01, 0.05, 0.10, and 1.00 nominal atomic %) were synthesized by the sol-gel method and characterized by X-ray diffraction,...     

The effects of deterioration and technological levels on pollutant emission factors for gasoline light-duty trucks

Vehicle deterioration and technological change influence emission factors (EFs). In this study, the impacts of vehicle deterioration and emission standards on EFs of regulated pollutants (carbon monoxide [CO], hydrocarbon [HC], and nitrogen oxides [NO_x]) for gasoline light-duty trucks (LDTs) were investigated according to the inspection and maintenance (I/M) data using a chassis dynamometer method. Pollutant EFs for LDTs markedly varied with accumulated mileages and emission standards, and the trends of EFs are associated with accumulated mileages. In addition, the study also found that in most cases, the median EFs of CO, HC, and NO_x are higher than those of basic EFs in the International Vehicle Emissions (IVE) model; therefore, the present study provides correction factors for the IVE model relative to the corresponding emission standards and mileages.

Implications: Currently, vehicle emissions are great contributors to air pollution in cities, especially in developing countries. Emission factors play a key role in creating emission inventory and estimating emissions. Deterioration represented by vehicle age and accumulated mileage and changes of emission standards markedly influence emission factors. In addition, the results provide collection factors for implication in the IVE model in the region levels.     

Methodologies for incorporation of synergistic effects in the calculation of the Pollutant Standards Index

The United States Environmental Protection Agency (EPA) developed the Pollutant Standards Index (PSI) in order to provide the public with an overall assessment of daily air quality. PSI values are determined from measured concentrations of five criteria air pollutants carbon monoxide, nitrogen dioxide, ozone, sulfur dioxide, and particulate matter (PM-10). In general, the PSI can be considered a useful tool in the assessment of air quality as it relates to health effects. However, the current method of PSI calculation is subject to certain inherent limitations. These limitations include the fact that the PSI neglects the role of synergism between the individual pollutants in affecting air quality and health. It is very likely that the combination of certain pollutants is more harmful than each acting individually. Since the general population is exposed to more than one of the criteria pollutants at a given time, revising the current PSI methodology to account for such synergism would be useful and helpful to the public. In the current work, two methodologies for synergistic PSI calculation have been evaluated. The first option (Option 1) is dominated by the principle of threshold levels. When further research determines more accurate levels, the methodology may be of value for future synergistic PSI evaluations. The second option (Option 2) is an attempt to incorporate the correlation of pollutant concentrations with health effects (as determined by increased hospital admissions) into the synergism evaluation. The underlying philosophy of this methodology holds the most promise for accurate synergistic PSI calculation. Comprehensive research and experimentation would be beneficial in creating a more accurate PSI function equation. The main advantage of these hypothetical methodologies is that the current PSI method would still be valid for initial PSI calculation. The dissimilarity is in the calculation of the critical (i.e. reportable) PSI value. It is no longer a matter of the highest PSI value among the pollutants being an accurate representative of air quality. Instead, each of the PSI values obtained is applied to a separate equation to determine a synergistic PSI. When above-average pollutant concentrations are recorded, the possibility of synergistic behavior increases and would be demonstrated with the application of both options. The advantage of Option 1 (versus Option 2) is that the equation was derived from a recognized approach to synergism in combination with the ideas of threshold levels. The advantage of Option 2 is that it is an attempt to correlate concentration levels with health effects observed in the health industry. It is possible that a combination of both philosophies will eventually lead to the development of a synergistic PSI methodology worthy of approval by the EPA.     

Daily surface UV exposure and its relationship to surface pollutant measurements

For the past 30 years, the stratospheric ozone layer has decreased in the Northern Hemisphere. The main effect of this ozone decrease was an expected increase in the UV radiation at the Earth's surface, but there has been no clear evidence of an increasing urban trend in surface UV. This study shows that specific air pollutants can reduce the increased surface levels of UV radiation and offers an explanation for why the expected surface UV increases have not been observed, especially in urban regions. A U.S. Environmental Protection Agency (EPA) UV monitoring site at the University of California at Riverside combined with air pollution data from a site operated by the California Air Resources Board in Rubidoux, CA, provided the basis of this study. The 1997 South Coast Ozone Study (SCOS-97) provided three key ingredients: black carbon, PM10 concentrations, and collocated radiometric measurements. The Total Ozone Mapping Spectrometer (TOMS) satellite data were used to provide the stratospheric ozone levels that were included in the statistical model. All of these input parameters would be used to test this study's hypothesis: the expected increase of surface UV radiation, caused by decreases in stratospheric ozone, can be masked by increases in anthropogenic emissions. The values for the pollutants were 7:00 a.m.-5:00 p.m. averages of the instrument's values taken during summer 1997. A statistical linear regression model was employed using the stratospheric ozone, black carbon, PM10, and surface ozone concentrations, and the sin (theta) and cos (theta). The angle theta is defined by theta = 2pi (Julian date/365). This model obtained a coefficient of determination of 0.94 with an uncertainty level (p value) of less than 0.3% for all of the variables in the model except ground-level ozone. The final model, regressed against a data set from a remote, western North Carolina site, resulted in a coefficient of determination of 0.92. The model shows that black carbon can reduce the Diffey-weighted UV levels that reach the surface by as much as 35%, depending on the season.     

The critical loads/levels approach to gaseous pollutant emission control

There is increasing pressure to control gaseous acidifying emissions to prevent harmful environmental effects; many governments are looking for a more effective and scientific means of assessing effects and planning emission controls compared with arbitrarily uniform percentage reductions. The critical loads/levels concept may offer the basis for a solution which is acceptable internationally. There is already agreement to map the critical loads and levels for countries in Europe and North America as a first step towards assessment. Recent developments in defining and quantifying critical loads and levels show the approach could be sufficiently adaptable to apply to the effects of different pollutants on a range of environmental receptors. Whilst it is difficult to arrive at an agreed single definition, various international groups have arrived at definitions which suit their own particular purposes. Despite a variety of different approaches to arriving at estimates of critical loads, there is broad agreement at the figures calculated by the different methods. An extension of the concept, the target load/level, provides a practical solution for implementing control strategies to prevent or minimize environmental effects.     

Antioxidant responses in clam Venerupis philippinarum exposed to environmental pollutant hexabromocyclododecane

The objective of this study was to assess the potential toxic effects of hexabromocyclododecane (HBCD) on tissues of clam Venerupis philippinarum using parameters of antioxidant defenses and oxidative stress. Antioxidant biomarkers including ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), superoxide dismutase (SOD), and glutathione (GSH), as well as DNA damage and lipid peroxidation (LPO) in gills and digestive glands of V. philippinarum, were analyzed after a 1-, 3-, 6-, 10-, and 15-day exposure to seawater containing HBCD at environmentally related concentrations, respectively. The results showed that the activity of most antioxidant enzymes increased, and different trends were detected with exposure time extending. The oxidative stress could be obviously caused in the gills and digestive glands under the experimental conditions. This could provide useful information for toxic risk assessment of environmental pollutant HBCD.     

Large-scale effects on resistivity index of porous media

The estimation of humidity in the unsaturated zone of soils and NAPL saturation in contaminated aquifers may be based on the interpretation of electrical resistivity index logs. In the present work, concepts of the theory of the two-phase flow in pore networks are employed to interpret the form of the equilibrium and dynamic resistivity index curves of large porous samples. A resistivity cell is constructed to measure the capillary and electrical properties of large samples of unconsolidated porous media. The drainage capillary pressure and resistivity index curves of a sand column are measured by using the micropore membrane (porous plate) method, where a 0.5% wt/vol NaCl aqueous solution is displaced by n-dodecane. The dynamic resistivity index curves are measured by using the continuous injection technique for various orientations of the sand column. Based on concepts of the two-phase flow theory, concerning the dominant displacement growth pattern in a pore network and arising from the cooperative effects of capillary, buoyancy, and viscous forces, approximate relationships are developed for the resistivity index and saturation exponent as functions of the water saturation. The saturation exponent decreases as the displacement advances and the fluid distribution across the sand column tends to be homogenized after oil breakthrough. Both the resistivity index and saturation exponent increase as the displacement pattern tends to become compact and stable. In the destabilized flow pattern, as the Bond number decreases, the resistivity index may increase respectably within a narrow range of values of the Bond number. This happens when the thickness of the unstable capillary finger exceeds the lateral dimension of the porous sample and becomes a fractal percolation cluster. The saturation exponent becomes almost constant and independent of water saturation only over the destabilized displacement pattern at high values of the Bond number.     

Three-dimensional modeling of air flow and pollutant dispersion in an urban street canyon with thermal effects

Effects of excess ground and building temperatures on airflow and dispersion of pollutants in an urban street canyon with an aspect ratio of 0.8 and a length-to-width ratio of 3 were investigated numerically. Three-dimensional governing equations of mass, momentum, energy, and species were modeled using the RNG k-epsilon turbulence model and Boussinesq approximation, which were solved using the finite volume method. Vehicle emissions were estimated from the measured traffic flow rates and modeled as banded line sources, with a street length and bandwidths equal to typical vehicle widths. Both measurements and simulations reveal that pollutant concentrations typically follow the traffic flow rate; they decline as the height increases and are higher on the leeward side than on the windward side. Three-dimensional simulations reveal that the vortex line, joining the centers of cross-sectional vortexes of the street canyon, meanders between street buildings and shifts toward the windward side when heating strength is increased. Thermal boundary layers are very thin. Entrainment of outside air increases, and pollutant concentration decreases with increasing heating condition. Also, traffic-produced turbulence enhances the turbulent kinetic energy and the mixing of temperature and admixtures in the canyon. Factors affecting the inaccuracy of the simulations are addressed.