Errors in coarse particulate matter mass concentrations and spatiotemporal characteristics when using subtraction estimation methods

In studies of coarse particulate matter (PM_10-2.5), mass concentrations are often estimated through the subtraction of PM_2.5 from collocated PM₁₀ tapered element oscillating microbalance (TEOM) measurements. Though all field instruments have yet to be updated, the Filter Dynamic Measurement System (FDMS) was introduced to account for the loss of semivolatile material from heated TEOM filters. To assess errors in PM_10-2.5 estimation when using the possible combinations of PM₁₀ and PM_2.5 TEOM units with and without FDMS, data from three monitoring sites of the Colorado Coarse Rural–Urban Sources and Health (CCRUSH) study were used to simulate four possible subtraction methods for estimating PM_10-2.5 mass concentrations. Assuming all mass is accounted for using collocated TEOMs with FDMS, the three other subtraction methods were assessed for biases in absolute mass concentration, temporal variability, spatial correlation, and homogeneity. Results show collocated units without FDMS closely estimate actual PM_10-2.5 mass and spatial characteristics due to the very low semivolatile PM_10-2.5 concentrations in Colorado. Estimation using either a PM_2.5 or PM₁₀ monitor without FDMS introduced absolute biases of 2.4 µg/m³ (25%) to –2.3 µg/m³ (–24%), respectively. Such errors are directly related to the unmeasured semivolatile mass and alter measures of spatiotemporal variability and homogeneity, all of which have implications for the regulatory and epidemiology communities concerned about PM_10-2.5. Two monitoring sites operated by the state of Colorado were considered for inclusion in the CCRUSH acute health effects study, but concentrations were biased due to sampling with an FDMS-equipped PM_2.5 TEOM and PM₁₀ TEOM not corrected for semivolatile mass loss. A regression-based model was developed for removing the error in these measurements by estimating the semivolatile concentration of PM_2.5 from total PM_2.5 concentrations. By estimating nonvolatile PM_2.5 concentrations from this relationship, PM_10-2.5 was calculated as the difference between nonvolatile PM₁₀ and PM_2.5 concentrations.

Implications: Errors in the estimation of PM_10-2.5 concentrations using subtraction methods were shown to be related to the unmeasured semivolatile mass when using certain combinations of TEOM instruments. For the northeastern Colorado region, the absolute bias associated with this error significantly affects mean and 95th percentile values, which would affect assessment of compliance if PM_10-2.5 is regulated in the future. Estimating PM_10-2.5 mass concentrations using nonvolatile mass concentrations from collocated PM₁₀ and PM_2.5 TEOM monitors closely estimates the total PM_10-2.5 mass concentrations. A corrective model that removes the described error was developed and applied to data from two sites in Denver.

Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association.     

Selective Lead(II) Adsorption and Flocculation Characteristics of the Grafted Sodium Alginate: A Comparative Study

Synthesis of sodium alginate-g-poly(acrylamide-co-N-methylacrylamide) [S-III], sodium alginate-g-poly(N-methylacrylamide-co-N,N-dimethylacrylamide) [S-II], sodium alginate-g-poly(acrylamide-co-N,N-dimethylacrylamide) [S-I]. Sodium alginate-g-poly(N,N-dimethylacrylamide) [SAG-g-PDMA] and sodium alginate-g-poly(acrylamide) [SAG-g-PAM] were prepared by solution polymerization technique using potassium peroxydisulfate as the initiator at 70?°C in water medium. The graft copolymers were characterized by FTIR and NMR (¹H and ¹³C) spectroscopy, SEM and XRD studies. All the five graft copolymers were used to remove Pb(II) ions from the aqueous solution and also in flocculation studies of kaolin clay (1.0 wt%), silica (1.0 wt%) and iron ore slime (0.25 wt%) suspensions. A comparative studies of all the five graft copolymers were also made in both the two cases. The Pb(II) ion removal capacity of all the graft copolymers follows the order S-III?>?SAG-g-PAM?>?S-II?>?SAG-g-PDMA?>?S-I. But the flocculation performance of the graft copolymers follows the order S-II?>?S-I?>?S-III?>?SAG-g-PDMA?>?SAG-g-PAM. S-III was also used for the competitive metal ion removal with Hg(II), Cd(II), Cu(II) and Zn(II). Pb(II) adsorption of S-III (the best Pb(II) ion adsorber) follows pseudo second order rate equation and Langmuir adsorption isotherm.     

生产体系对肉产品(主要是猪肉)品质的影响

肉产品的技术、营养和感官品质在屠宰前后可能会受到多种交互作用因素的影响.从文献来看,以创造猪肉可持续生产体系为目标的各种变革,通常对肉的最终pH值没有影响或影响较小.一些研究表明,可持续生产体系降低了猪肉的持水能力.与常规饲养体系相比,户外生产被认为更能增加猪肉的剪切力值.肉色的影响因素很多,这些因素可能导致猪肉颜色更暗、色素含量增加,或猪肉颜色更浅淡、结构有所变化.在使用含有多不饱和脂肪酸饲料的生产体系中,肉产品所含类脂的不饱和性更强,肉产品的营养价值更高.一句话,必须考虑各因素间的组合效应如:饲养、生产体系、遗传型、性别和宰前处理等对肉品质量的影响.     

Thermo- and fluid-dynamical modelling of two-phase multi-component carbon dioxide mixtures

A method for calculating the transport and depressurization of a two-phase multi-component CO₂ mixture is presented. The thermodynamical and transport properties for a CO₂–CH₄ mixture are calculated using the Soave–Redlich–Kwong equation of state (SRK). The fluid flow is described by a drift-flux model, which is solved using the multi-stage (MUSTA) centred scheme. Numerical results are shown, illustrating the effect of mixture composition and the feasibility of the approach.     

Cognitive processes in procedural justice judgments: The role of ease‐of‐retrieval,uncertainty, and experience

In a field experiment with 517 job applicants, the processes underlying the formation of procedural justice judgments were investigated. It was hypothesized that procedural justice judgments may be based not only on content information (e.g., “What are fair aspects of the selection procedure?”), but also on the felt ease or difficulty with which this content information can be retrieved from memory (ease‐of‐retrieval; e.g., “How easily can I recall fair aspects of the selection procedure?”). Evaluations of the company's online application procedure show that job candidates based procedural justice judgments on content information or on ease‐of‐retrieval, depending on their uncertainty regarding the online application procedure as well as their prior experiences with online applications. Specifically, experienced applicants who felt certain based their judgments on ease‐of‐retrieval, whereas all other applicants based their judgments on content information. Implications for research on the formation of justice judgments as well as practical applications are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Statistical evaluation of photon count rate data for nanoscale particle measurement in wastewaters

The dynamic light scattering (DLS) technique can detect the concentration and size distribution of nanoscale particles in aqueous solutions by analyzing photon interactions. This study evaluated the applicability of using photon count rate data from DLS analyses for measuring levels of biogenic and manufactured nanoscale particles in wastewater. Statistical evaluations were performed using secondary wastewater effluent and a Malvern Zetasizer. Dynamic light scattering analyses were performed equally by two analysts over a period of two days using five dilutions and twelve replicates for each dilution. Linearity evaluation using the sixty sample analysis yielded a regression coefficient R(2) = 0.959. The accuracy analysis for various dilutions indicated a recovery of 100 ± 6%. Precision analyses indicated low variance coefficients for the impact of analysts, days, and within sample error. The variation by analysts was apparent only in the most diluted sample (intermediate precision ~12%), where the photon count rate was close to the instrument detection limit. The variation for different days was apparent in the two most concentrated samples, which indicated that wastewater samples must be analyzed for nanoscale particle measurement within the same day of collection. Upon addition of 10 mg l(-1) of nanosilica to wastewater effluent samples, the measured photon count rates were within 5% of the estimated values. The results indicated that photon count rate data can effectively complement various techniques currently available to detect nanoscale particles in wastewaters.     

Robust Energy Portfolios Under Climate Policy and Socioeconomic Uncertainty

Concerning the stabilization of greenhouse gases, the UNFCCC prescribes measures to anticipate, prevent, or minimize the causes of climate change and mitigate their adverse effects. Such measures should be cost-effective and scientific uncertainty should not be used as a reason for postponing them. However, in the light of uncertainty about climate sensitivity and other underlying parameters, it is difficult to assess the importance of different technologies in achieving robust long-term climate risk mitigation. One example currently debated in this context is biomass energy, which can be used to produce both carbon-neutral energy carriers, e.g., electricity, and at the same time offer a permanent CO₂ sink by capturing carbon from the biomass at the conversion facility and permanently storing it. We use the GGI Scenario Database IIASA [3] as a point of departure for deriving optimal technology portfolios across different socioeconomic scenarios for a range of stabilization targets, focusing, in particular, on new, low-emission scenarios. More precisely, the dynamics underlying technology adoption and operational decisions are analyzed in a real options model, the output of which then informs the portfolio optimization. In this way, we determine the importance of different energy technologies in meeting specific stabilization targets under different circumstances (i.e., under different socioeconomic scenarios), providing valuable insight to policymakers about the incentive mechanisms needed to achieve robust long-term climate risk mitigation.     

Distribution and Environmental Risk Assessment of Heavy Metal in Surface Sediments and Red Mullet (<Emphasis Type="Italic">Mullus barbatus</Emphasis>) from Algiers and BouIsmail Bay (Algeria)

BouIsmail (BIB) and Algiers (AB) are the most important bays in Algeria, where busy shipping activities and various industry complexes introduce different pollutants including heavy metals to the aquatic environment. The main goal of this study was to assess the contamination levels of heavy metals (Cd, Cr, Cu, Fe, Hg, Mn, Pb, Zn) in surface sediments and red mullet (Mullus barbatus) of the BIB and AB and to examine the possibility of the use of their enrichment factors (EFs) to track down the sources of metals (natural processes or human activity). The geoaccumulation index (I _geo) was calculated as a criterion to indicate the contamination level for each heavy metal. Moreover, geographical information systems based on spatial analysis methods (inverse distance weighting (IDW)) and statistical approaches (the principal component (PCA)) were performed to assess the spatial influences of multiple anthropogenic sources in different sampled areas. The results of both EF and I _geo revealed that the study area is exposed to various anthropogenic activities. The pollution load index (PLI) values of sediment samples in the different sites of Algiers and BIB ranged from 0.2 to 3.4 illustrating highly contaminated sediments. Significant bioaccumulation of Cd, Cu, Hg, Pb, and Zn (bioaccumulation factor >100%) were observed in muscle and liver of red mullet, suggesting potential health risks through consuming this fish species.