Source apportion of atmospheric particulate matter: a joint Eulerian/Lagrangian approach

PM_2.5 samples were collected during an annual monitoring campaign (January 2012–January 2013) in the urban area of Naples, one of the major cities in Southern Italy. Samples were collected by means of a standard gravimetric sampler (Tecora Echo model) and characterized from a chemical point of view by ion chromatography. As a result, 143 samples together with their ionic composition have been collected. We extend traditional source apportionment techniques, usually based on multivariate factor analysis, interpreting the chemical analysis results within a Lagrangian framework. The Hybrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT) model was used, providing linkages to the source regions in the upwind areas. Results were analyzed in order to quantify the relative weight of different source types/areas. Model results suggested that PM concentrations are strongly affected not only by local emissions but also by transboundary emissions, especially from the Eastern and Northern European countries and African Saharan dust episodes.     

Comparison of a new Eulerian model with a modified Lagrangian approach for particle distribution and deposition indoors

Understanding of aerosol dispersion characteristics has many scientific and engineering applications. It is recognized that Eulerian or Lagrangian approach has its own merits and limitations. A new Eulerian model has been developed and it adopts a simplified drift–flux methodology in which external forces can be incorporated straightforwardly. A new near-wall treatment is applied to take into account the anisotropic turbulence for the modified Lagrangian model. In the present work, we present and compare both Eulerian and Lagrangian models to simulate particle dispersion in a small chamber. Results reveal that the standard k–ε Lagrangian model over-predicts particle deposition compared to the present turbulence-corrected Lagrangian approach. Prediction by the Eulerian model agrees well with the modified Lagrangian model.     

On the relationship between acid rain and cloud type

Spanish European Monitoring and Evaluation Programme (EMEP) stations were selected to relate acid rain episodes with the meteorological structure that caused the rainfall during a 5-year period. A principal component analysis (PCA) was used to determine the origin of major ions (SO4(2-), NO3-, Cl-, Ca2+, K+, Mg2+, and Na+) in the rainwater. In addition, the meteorological origin of the rain was identified. Previous works suggested a relationship between acid rain and storm convective clouds. However, statistical analyses of pH values show that only the short-lived convective phenomena may cause acid rain in Spain. In fact, rain generated by fronts and that related to long-lived convective systems is neutral or even slightly basic. Results suggest that the acid rain might be related to the meteorological time scale instead of to the cloud type.     

The relationship between mixed-liquor particle size and solids retention time in the activated sludge process

Particle size distribution (PSD) analysis was used to evaluate the quality of mixed liquors collected from different activated sludge process modifications (i.e., conventional activated sludge, modified Ludzack-Ettinger, high-purity oxygen, step-anoxic, and oxidation ditch). An experiment protocol was developed to define the allowable sample holding time and provide representative and repeatable results. Samples of 26 treatment plants, with a total of 37 samples, were tested. A new indicator, called mean particle size (MPS), was introduced to describe the integrated mean particle size. The results of MPSs of three cut-off sizes (0.5 to 50, 100, and 200 microm) showed that the average size of mixed-liquor biosolids increased with increasing solids retention time (SRT), and the number of particles in the sedimentation supernatant decreased with increasing SRT. Particle deflocculation occurred after excessive sample holding time, and analysis within 12 hours generally eliminated sample holding problems. The results provide a methodology using PSD for characterizing mixed-liquor biosolids.     

A scheme for black carbon and sulphate aerosols tested in a hemispheric scale,Eulerian dispersion model

Production, transport and deposition of sulphate and black carbon (BC) are simulated separating aerosol modes by production mechanisms, thus facilitating calculation of aerosol physical properties. The scheme uses explicit sulphur chemistry with prescribed oxidants and aerosol transformation based on Brownian coagulation rates, and is implemented in a 3-D, hemispheric-scale transport model with off-line meteorology from ECMWF. The components are DMS, SO₂, sulphate and BC. Simulations are made for the year 1988. Predicted results for sulphate agree well with the measurements, except for considerable underestimations in the Arctic. In Europe SO₂ is slightly overestimated and sulphate is slightly underestimated in cold seasons, whilst trends are less clear in North America. Compared to many other models, we estimate a smaller effective oxidation rate for SO₂ due to reduced rates in cold clouds; a shorter turnover time for sulphate (3.7 d) due to a probably too large below-cloud scavenging ratio; and slightly smaller sulphate column burdens. Our BC results are similar to Liousse et al.’s (1996, J. Geophys. Res. 101, 19.411–19.432) except in USA, whilst the concentrations in remote areas and the turnover time (3.7 d) are considerably smaller than Cooke and Wilson’s (1996, J. Geophys. Res. 101, 190.395–19.409). Agreements with available measurements are quite close to large anthropogenic emissions (including USA), but they are considerably underestimated in Arctic winter. Transition from hydrophobic to hydrophilic BC due to coagulation is swift (6% h^-1). Sensitivity tests emphasize that sub-cloud scavenging coefficients rely on careful assumptions about size distributions, and that more research is needed on sulphate production in ice-clouds. Emphasis should also be put on production of sulphate and hydrophilic BC boundary-layer clouds; inclusion of hydrophobic accumulation mode BC and sub-grid transition to hydrophilic BC in emitting grid squares.     

Eulerian derivation of the fractional advection-dispersion equation

A fractional advection-dispersion equation (ADE) is a generalization of the classical ADE in which the second-order derivative is replaced with a fractional-order derivative. In contrast to the classical ADE, the fractional ADE has solutions that resemble the highly skewed and heavy-tailed breakthrough curves observed in field and laboratory studies. These solutions, known as alpha-stable distributions, are the result of a generalized central limit theorem which describes the behavior of sums of finite or infinite-variance random variables. We use this limit theorem in a model which sums the length of particle jumps during their random walk through a heterogeneous porous medium. If the length of solute particle jumps is not constrained to a representative elementary volume (REV), dispersive flux is proportional to a fractional derivative. The nature of fractional derivatives is readily visualized and their parameters are based on physical properties that are measurable. When a fractional Fick's law replaces the classical Fick's law in an Eulerian evaluation of solute transport in a porous medium, the result is a fractional ADE. Fractional ADEs are ergodic equations since they occur when a generalized central limit theorem is employed.     

Estimation of local scale dispersion from local breakthrough curves during a tracer test in a heterogeneous aquifer: the Lagrangian approach

The local scale dispersion tensor, Dd, is a controlling parameter for the dilution of concentrations in a solute plume that is displaced by groundwater flow in a heterogeneous aquifer. In this paper, we estimate the local scale dispersion from time series or breakthrough curves, BTCs, of Br concentrations that were measured at several points in a fluvial aquifer during a natural gradient tracer test at Krauthausen. Locally measured BTCs were characterized by equivalent convection dispersion parameters: equivalent velocity, v(eq)(x) and expected equivalent dispersivity, [lambda(eq)(x)]. A Lagrangian framework was used to approximately predict these equivalent parameters in terms of the spatial covariance of log(e) transformed conductivity and the local scale dispersion coefficient. The approximate Lagrangian theory illustrates that [lambda(eq)(x)] increases with increasing travel distance and is much larger than the local scale dispersivity, lambda(d). A sensitivity analysis indicates that [lambda(eq)(x)] is predominantly determined by the transverse component of the local scale dispersion and by the correlation scale of the hydraulic conductivity in the transverse to flow direction whereas it is relatively insensitive to the longitudinal component of the local scale dispersion. By comparing predicted [lambda(eq)(x)] for a range of Dd values with [lambda(eq)(x)] obtained from locally measured BTCs, the transverse component of Dd, DdT, was estimated. The estimated transverse local scale dispersivity, lambda(dT) = DdT/U1 (U1 = mean advection velocity) is in the order of 10(1)-10(2) mm, which is relatively large but realistic for the fluvial gravel sediments at Krauthausen.     

Variation in the relationship between blood lead and air lead

Estimates of the slope of the relationship between blood lead (μg dl⁻¹) and air lead (μg m⁻³) obtained in ten independent studies are compared. No significant differences were detected among the estimates which ranged from 0.6 to 3.1 μg dl⁻¹ per μg m⁻³ and represented male adult, female adult and child populations. A single best estimate of 1.2 μg dl⁻¹ per μg m⁻³ ( ± 0.2,95 per cent confidence limits) was obtained. It is concluded that, if the blood lead-air lead slope depends on various physical and biological factors, then studies providing more precise estimates are required to detect these differences.     

State-space modeling of the relationship between air quality and mortality

A portion of a population is assumed to be at risk, with the mortality hazard varying with atmospheric conditions including total suspended particulates (TSP). This at-risk population is not observed and the hazard function is unknown; we wish to estimate these from mortality count and atmospheric variables. Consideration of population dynamics leads to a state-space representation, allowing the Kalman Filter (KF) to be used for estimation. A harvesting effect is thus implied; high mortality is followed by lower mortality until the population is replenished by new arrivals. The model is applied to daily data for Philadelphia, PA, 1973-1990. The estimated hazard function rises with the level of TSP and at extremes of temperature and also reflects a positive interaction between TSP and temperature. The estimated at-risk population averages about 480 and varies seasonally. We find that lags of TSP are statistically significant, but the presence of negative coefficients suggests their role may be partially statistical rather than biological. In the population dynamics framework, the natural metric for health damage from air pollution is its impact on life expectancy. The range of hazard rates over the sample period is 0.07 to 0.085, corresponding to life expectancies of 14.3 and 11.8 days, respectively.     

On the relationship between ozone and its precursors in the Pearl River Delta: application of an observation-based model (OBM)

Background, aim, and scope  

Photochemical smog, characterized by high concentrations of O₃ and fine particles, is of great concern in the urban areas, in particular megacities and city clusters like the Pearl River Delta.     

The relationship between elimination rates and partition coefficients

Rate constants for uptake and elimination of chemicals in organisms are often related to partition coefficients (typically the octanol-water partition coefficient). We show that the well-mixed one-compartment model for toxico-kinetics implies that the elimination rate is inversely proportional to the square root of the partition coefficient. When chemical exchange is limited by diffusion in the boundary layers adjacent to the interface, two-film models are appropriate, which have more complex implications for the relationships between the exchange rates and the partition coefficient. We also show that the popular steady-flux approximation of the two-film model is not a conceptual generalization of the one-compartment model, although it shares the first-order kinetics. We compare the kinetics of a series of models with an increasing number of well-mixed compartments for exchange, such that the two-film model results for an infinite number of compartments. The latter model formulation in terms of partial differential equations, and more in particular its boundary condition at the interface of the two media, is believed to be new. In the steady-flux approximation and in the model with single well-mixed boundary layers and low diffusivities, the elimination rate depends hyperbolically on the partition coefficient. The available data for abiotic systems (SPME fibers) supports a hyperbolic relationship, whereas the data for aquatic biota are less discriminating between a hyperbolic or a square root relationship with the partition coefficient. The daphnia data showed less scatter than the fish data, possibly due to the small variance in body sizes, since elimination rates are inversely proportional to body length. The square root relationship fitted these data best.     

Temporal and spatial variations in the relationship between urbanization and water quality

With the development of economy, most of Chinese cities are at the stage of rapid urbanization in recent years, which has caused many environmental problems, especially the serious deterioration of water quality. Therefore, the research of the relationship between urbanization and water quality has important theoretical and practical significance, and it is also the main restriction factor in the urbanization advancement. In this work, we investigated the impact of urbanization on the water quality of the nearby river. We established a comprehensive environmental assessment framework by combining urbanization and water quality, and one model was designed to examine the impact of urbanization on the water quality in Jinan from 2001 to 2010 with factor component analysis. The assessment of urbanization level was accomplished using a comprehensive index system, which was based on four aspects: demographic urbanization, economic urbanization, land urbanization, and social urbanization. In addition, synthetic pollution index method was utilized to assess the water pollution of Xiaoqing River in the study area. Through the analysis of regression curves, we conclude that (1) when the urbanization level is below 25 %, the relationship is low and irregular; (2) if the urbanization level varies between 25 and 40 %, there will be an irreversible degradation of stream water quality; (3) there is a positive correlation between urbanization and pollution levels of urban river after the adjustment period; and (4) land and demographic aspects have the highest independent contribution. This study is a useful reference for policymakers in terms of economic and environmental management.     

The relationship between flow and bacteria in streams

A method is proposed to relate the statistics of in-stream bacteria concentrations to the surface-runoff fraction of stream flow. The parameters of this relationship include the characteristic concentration of bacteria in surface runoff and the characteristic concentration of bacteria in the base flow, and these parameters can be derived from synoptic bacteria and flow measurements. The effectiveness of the proposed method is demonstrated at several U.S. locations for both Escherichia coli and fecal coliform bacteria. Application of the proposed method at a particular location showed that the method can be used to identify the most effective bacteria source controls and that conventional application of the load-duration curve might lead to erroneous identification of target sources.     

The relationship between indoor and outdoor airborne particles in the residential environment

The relationship between indoor and outdoor airborne particles was investigated for 16 residential houses located in a suburban area of Brisbane, Australia. The submicrometer particle numbers were measured using the Scanning Mobility Particle Sizer, the larger particle numbers using the Aerodynamic Particle Sizer and an approximation of PM_2.5 was also measured using a DustTrak. The measurements were conducted for normal and minimum ventilation conditions using simultaneous and non-simultaneous measurement methods designed for the purpose of the study. Comparison of the ratios of indoor to outdoor particle concentrations revealed that while temporary values of the ratio vary in a broad range from 0.2 to 2.5 for both lower and higher ventilation conditions, average values of the ratios were very close to one regardless of ventilation conditions and of particle size range. The ratios were in the range from 0.78 to 1.07 for submicrometer particles, from 0.95 to 1.0 for supermicrometer particles and from 1.01 to 1.08 for PM_2.5 fraction. Comparison of the time series of indoor to outdoor particle concentrations shows a clear positive relationship existing for many houses under normal ventilation conditions (estimated to be about and above 2 h⁻¹), but not under minimum ventilation conditions (estimated to be about and below 1 h⁻¹). These results suggest that for normal ventilation conditions, outdoor particle concentrations could be used to predict instantaneous indoor particle concentrations but not for minimum ventilation, unless air exchange rate is known, thus allowing for estimation of the “delay constant”.     

上海市交通碳排放量与城市发展的关系研究

随着社会经济快速发展,上海市交通需求量逐年增长,导致交通运输行业的能源消费量以及碳排放量不断增加。研究了1998—2012年上海市交通碳排放量与城市发展的关系,并对该市的交通碳排放量进行了预测与情景分析。结果表明,上海市交通碳排放量与人均GDP、人均消费支出、城市化率均呈显著的正相关关系。协整检验显示,上海市交通碳排放量与上海市城市发展存在协整关系。对交通碳排放量影响最显著的是城市化率,其次是人均GDP,再次是人均消费支出。在正常、低碳、强化低碳情景下,2050年上海市的交通碳排放量分别为46 599.24万、28 196.70万、9 575.47万t。通过转变发展方式,有望科学合理地减少交通碳排放量。     

污泥的粘度与浓度、温度三者关系式的实验推导

通过融合污泥粘度与污泥浓度关系式、污泥粘度与温度关系式,得到一个新的关系式:污泥粘度与污泥浓度、温度的关系式,并通过实验数据拟合出各项参数,拟合效果比较理想.得出的污泥粘度与污泥浓度、温度的关系式对了解污泥的粘度变化非常有帮助,同时,该关系式也将为污泥处理、处置方案的制定提供参考依据.     

The relationship between the convective boundary layer and dispersion from tall stacks

This paper discusses the structure of the convective planetary boundary layer in relation to dispersion of pollutants. As tall stack plumes are brought down to the ground primarily during unstable conditions, we have investigated the conditions under which the PBL is convective. Our analysis indicates that the convective PBL occurs more often than is commonly thought. The second part of the paper describes some aspects of dispersion in the convective PBL. We propose a simple model capable of providing factor-of-two type estimates of ground-level concentrations. We also discuss some of the factors which complicate attempts to obtain more accurate results. In this context, we point out the problems associated with using model-predicted ensemble means to estimate observed concentrations.     

污泥的粘度与浓度、温度三者关系式的实验推导

通过融合污泥粘度与污泥浓度关系式、污泥粘度与温度关系式，得到一个新的关系式：污泥粘度与污泥浓度、温度的关系式，并通过实验数据拟合出各项参数，拟合效果比较理想。得出的污泥粘度与污泥浓度、温度的关系式对了解污泥的粘度变化非常有帮助，同时，该关系式也将为污泥处理、处置方案的制定提供参考依据。