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Howell N.L.,University of Houston | Rifai H.S.,University of Houston | Koenig L.,Texas Commission on Environmental Quality TCEQ
Chemosphere | Year: 2011

PCDD/F and PCB field data (1041 samples) in five media (dissolved, suspended sediment, bed sediment, catfish, and blue crab) were studied to explore dual contaminant patterns in the Houston Ship Channel, Texas, USA. PCDD/Fs showed greater concentration than PCBs in suspended sediments while PCBs were higher in apparent dissolved (truly dissolved+DOC-associated), fish, and crab. PCDD/Fs at nearly all locations contributed more strongly to dioxin-like toxicity. The fraction of PCB TEQ was, however, enriched in biotic over abiotic media due in large part to the presence of PCB 126, which was mostly undetected in water and sediment and yet exhibited a BAF three times greater than 2,3,7,8-TCDD. Dissolved-suspended sediment and suspended-bed sediment relationships showed that (1) observed apparent dissolved concentration differences (as fraction of total water were mean 10% PCDD/Fs and 63% PCBs) can reasonably be explained by a four-phase partition model (truly dissolved, DOC-associated, suspended OC, and suspended BC) for PCBs but not for PCDD/Fs and (2) the contaminants behaved similarly in bed to suspended sediment concentration ratios (Cbed/Csusp) upstream of a major confluence but not downstream. PCA-cluster analysis pointed to the possibility that suspended sediment PCB contamination originates from resuspended bed sediment while PCDD/Fs in suspended sediment originates more probably from other sediment sources such as upstream wash load or air deposition. Finally, examinations of a congener marker ratio (PCB 209/206) seemed to indicate that a source of pure PCB 209 may exist in bed sediment near Patrick Bayou though the source was not completely localized. © 2011 Elsevier Ltd. Source


Howell N.L.,University of Houston | Lakshmanan D.,University of Houston | Rifai H.S.,University of Houston | Koenig L.,Texas Commission on Environmental Quality TCEQ
Science of the Total Environment | Year: 2011

All 209 PCB congeners are quantified in water in both dry and wet weather urban flows in Houston, Texas, USA. Total water PCBs ranged from 0.82 to 9.4. ng/L in wet weather and 0.46 to 9.0. ng/L in dry. Wet weather loads were 8.2 times higher (by median) than dry weather with some increases of over 100-fold. The majority of the PCB load was in the dissolved fraction in dry weather while it was in the suspended fraction in wet weather. Dissolved PCB loads were correlated with rain intensity and highly developed land area, and a multiple linear regression (MLR) equation was developed to quantify these correlations. PCA generated five PCB components with nearly all positive loadings. They were interpreted as DOC-associated A1248, wet weather primarily suspended fraction A1254/A1260 likely from building sealants, truly dissolved-associated wastewater dechlorination, watershed-sourced PCB 11, and monochlorinated PCBs (likely connected to a different state or source of dechlorination). The PCB 11 component was statistically higher in wet versus dry weather when no other component showed such clear distinctions. Hierarchical cluster analysis (HCA) did not always group dry and wet weather samples from the same location together illustrating the different congener composition that often exists between dry and wet conditions. Four wet weather samples from high percentage developed land (> 90%) watersheds had nearly the same fingerprint suggesting a generic "urban" signature in runoff, which in this case was caused by residual A1254/A1260 PCB stocks and currently produced PCB 11 in consumer goods. © 2011 Elsevier B.V. Source


Daniel S.,Texas Commission on Environmental Quality TCEQ | Lou C.,Iowa State University | Jo Min K.,Iowa State University
Electric Power Systems Research | Year: 2013

In the Public Utilities Regulatory Policies Act (PURPA) in the USA, to promote cogeneration, there exists a key provision for qualifying facilities to sell the cogenerated electric power to host utilities at a pre-determined price. In this paper, we investigate the economic implications and consequences of this "right to sell" provision. First, under PURPA, we show how the interaction between a cogeneration facility and an electric utility can be modeled as a Stackelberg game, and derive the equilibrium generation quantities, prices, as well as the corresponding profits and total surplus. We next construct a benchmark model under a deregulated environment. By comparing and contrasting these two models, we obtain various results of managerial insights, economic implications, and policy ramifications. For example, under the right to sell provision, we identify the conditions for a qualifying facility's arbitrage to occur. Also, relative to the deregulated benchmark model, we show how the government's right to sell provision may lead to inferior economic performance. © 2013 Elsevier B.V. All rights reserved. Source


Haney J.T.,Texas Commission on Environmental Quality TCEQ | Erraguntla N.,Texas Commission on Environmental Quality TCEQ | Sielken R.L.,Sielken and Associates Consulting Inc. | Valdez-Flores C.,Sielken and Associates Consulting Inc.
Regulatory Toxicology and Pharmacology | Year: 2012

The carcinogenicity of hexavalent chromium(CrVI) is of significant interest to regulatory agencies for the protection of public health and to industry. Additionally, the mode of action (MOA) and conditions under which CrVI may induce carcinogenicity (e.g., reductive capacity considerations) have recently been the subject of significant scientific debate. Epidemiological data supported by data relevant to the carcinogenic MOA support considering nonlinear-threshold carcinogenic assessments for comparison to default linear low-dose extrapolation approaches. This study reviews epidemiological studies available in the scientific literature and conducts additional statistical dose-response analyses to identify potential carcinogenic thresholds and points of departure (PODs) in the context of supportive MOA information for a nonlinear-threshold inhalation carcinogenic assessment. Dosimetric adjustments and application of appropriate uncertainty factors (total UF of 30) to the selected cumulative exposure POD results in a cancer-based chronic inhalation reference value (ReV) of 0.24μgCrVI/m 3. This chronic ReV is 300 times higher than the 1 in 100,000 excess cancer risk air concentration of 8E-04μg/m 3 based on USEPA's unit risk factor. © 2012 Elsevier Inc. Source


Shaw B.,Texas Commission on Environmental Quality TCEQ | Lange S.,Texas Commission on Environmental Quality TCEQ | Honeycutt M.,Texas Commission on Environmental Quality TCEQ
EM: Air and Waste Management Association's Magazine for Environmental Managers | Year: 2015

The Texas Commission on Environmental Quality argues that the thoughtful integration of scientific data does not support the assumption that tightening the ozone standard will result in measurable health benefits. © 2015, Air and Waste Management Association. All rights reserved. Source

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