James Li

A physiologically‐based pharmacokinetic model for disposition of 2,3,7,8‐TCDD in fathead minnow and medaka

A physiologically-based pharmacokinetic model was developed for the disposition of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in 2 fish species--fathead minnow and medaka. The model was developed based on the empirical data on disposition of dioxins in fish tissues, as well as existing knowledge on the mechanisms of uptake, distribution, storage, and elimination of dioxins in various species (other than fish). The present study examined the applicability of mechanisms known to occur in other species for fish and concluded that the same mechanisms defined for disposition of 2,3,7,8-TCDD in (mostly) rodents can be applicable for the 2 fish species examined as well. Parameter values for the model were selected and/or calibrated using available databases. Model compartments included the gill, kidney, liver, and other richly-perfused tissues, as well as fat and other slowly-perfused tissues. The model was calibrated using 2 independent datasets for exposure of fathead minnow and medaka to 2,3,7,8-TCDD in water. The initial values of the model parameters were selected from several sources, and calibrated to represent the 2 exposure datasets. With very few exceptions, the estimated parameter values for the 2 species were comparable, and the final predictions were in strong agreement with the observations. The model developed in the present study can therefore be used in the prediction of the body burden of 2,3,7,8-TCDD in fathead minnow and medaka. Uncertainty in the model prediction as a result of variability in input parameters is discussed for the parameters with the highest impacts on the model outcome.

Characterization of Urban Runoff Quality: A Toronto Case Study

This chapter presents an overview of the characterization of urban runoff quality constituents. Characterization includes descriptive statistics, correlation a…

Modeling low impact development potential with hydrological response units

Evaluations of benefits of implementing low impact development (LID) stormwater management techniques can extend up to a watershed scale. This presents a challenge for representing them in watershed models, since they are typically orders of magnitude smaller in size. This paper presents an approach that is focused on trying to evaluate the benefits of implementing LIDs on a lot level. The methodology uses the concept of urban hydrological response Unit and results in developing and applying performance curves that are a function of lot properties to estimate the potential benefit of large-scale LID implementation. Lot properties are determined using a municipal geographic information system database and processed to determine groups of lots with similar properties. A representative lot from each group is modeled over a typical rainfall year using USEPA Stormwater Management Model to develop performance functions that relate the lot properties and the change in annual runoff volume and corresponding phosphorus loading with different LIDs implemented. The results of applying performance functions on all urban areas provide the potential locations, benefit and cost of implementation of all LID techniques, guiding future decisions for LID implementation by watershed area municipalities.

Characterization of Green Roof Stormwater Runoff Quality

Green roofs are recognized as effective means of stormwater quantity control through runoff volume reduction and peak discharge attenuation. A properly designe…

Correction of discrepancies in dioxin quantification between immunoassay and gas chromatography–high-resolution mass spectrometry

AbstractDue to the toxicity of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F), efforts are made to quantify their emission into the environment. Typically, this quantification is done using gas chromatography–high-resolution mass spectrometry (GC–HRMS). However, GC–HRMS is extremely expensive and time consuming, and GC–HRMS facilities are overly requested. In order to decrease the workload on GC–HRMS, another alternative is to use an enzyme-linked immunosorbent assay (ELISA) as a semi-quantitative screening tool. One problem of this solution is that ELISA measures the total PCDD/F content of a sample differently than GC–HRMS; a disparity exists between the two techniques. This paper introduces a congener correction factor that adjusts ELISA results for this incompatibility. The importance of the correction factor is explored by examining the congener profiles of 27 different dioxin sources. The congener profiles for many of these sources are such that large incompatibilities in predicted PCDD/F content would likely exist between uncorrected ELISA and GC–HRMS. The effect that the correction factor has on the correlation between ELISA and GC–HRMS for samples from a test site with dioxin-contaminated soils was also examined. The congener profile at this site was such that the inconsistencies between uncorrected ELISA and GC–HRMS results were relatively small. However, application of the congener correction factor still improved the correlation between ELISA and GC–HRMS by 11% when using sample-specific correction factors and by 5% when using an average site-wide correction factor. The findings of this paper suggest that application of the correction factor is necessary to remove incompatibilities between ELISA and GC–HRMS—particularly when the congener profile at a site would lead to incompatibilities that are large. FigureMinimal GH-HRMS determinations for calculating ELISA correction factor for a dioxin contaminated site

The Perceptions of Stakeholders in Low Impact Development Planning

As part of measures to mitigate the impact of contaminants on Lake Simcoe, a project is being carried out by the Lake Simcoe Region Conservation Authority (LSR…

Modeling the Stormwater Benefits of Green Roofs in the City of Toronto

Stormwater best management practices (BMPs) provide a number of tools to reduce the quantity and improve the quality of stormwater runoff at the source, along …

Comprehensive Urban Runoff Quantity/Quality Management Modelling

This study introduces an analysis methodology for the preliminary planning of urban runoff quantity and quality control systems. The methodology consists of fi…

Probabilistic spill occurrence simulation for chemical spills management.

Inland chemical spills pose a great threat to water quality in worldwide area. A sophisticated probabilistic spill-event model that characterizes temporal and spatial randomness and quantifies statistical uncertainty due to limited spill data is a major component in spill management and associated decision making. This paper presents a MATLAB-based Monte Carlo simulation (MMCS) model for simulating the probabilistic quantifiable occurrences of inland chemical spills by time, magnitude, and location based on North America Industry Classification System codes. The models aleatory and epistemic uncertainties were quantified through integrated bootstrap resampling technique. Benzene spills in the St. Clair River area of concern were used as a case to demonstrate the model by simulating spill occurrences, occurrence time, and mass expected for a 10-year period. Uncertainty analysis indicates that simulated spill characteristics can be described by lognormal distributions with positive skewness. The simulated spill time series will enable a quantitative risk analysis for water quality impairments due to the spills. The MMCS model can also help governments to evaluate their priority list of spilled chemicals.

Fuzzy TOPSIS Model for Pollution Assessment of Unintentional Produced Polychlorinated Biphenyls in China

Due to Chinese air concentration of polychlorinated biphenyls (PCBs) was increasingly from 2004 to 2008, and PCBs were banned in the past decade in China. With rapidly development of Chinese economy, the unintentional produced PCBs (UP-PCBs) may become the main sources of air concentration. We pay attention to investigate the production amount of different industries of different provinces in China. Through emission factor of different pollutant sources to calculate the weights, then using the fuzzy TOPSIS to assess pollutant emission, the results showed a strong and significant coefficient between cement production and emission, and between closeness coefficient (C*) and Gross Domestic Product (GDP) of different provinces in 2009, then we compare the total amount of emission to C* values in different provinces that found the order of emission assessment very approximately. Hence, the fuzzy TOPSIS methods can effectively assess the pollution emission condition of UP-PCBs.