Mechanistic aspects regarding the direct aqueous environmental photochemistry of phenol and its simple halogenated derivatives. A review

We have reviewed the mechanistic aspects regarding the direct aqueous phase environmental photochemistry of phenol and its simple halogenated derivatives. These compounds are important industrial and natural products, are ubiquitous in aquatic systems, and their acute and chronic toxicity makes their environmental fate of interest. Work over the past two decades has unified the photochemistry of phenol and its simple halogenated derivatives. In general, three photochemical pathways dominate in aqueous solution depending on the nature of the substrate: (1) photoionization, (2) photochemical aryl-halogen bond homolysis, and (3) photochemical aryl-halogen bond heterolysis. Photoionization typically results in an array of biaryl radical coupling products which are only relevant for highly concentrated waste streams. Photolytic aryl-halogen bond homolysis will primarily give photoreduction products where reducing agents such as dissolved organic matter or reduced metal cations are present, and radical coupling products in highly concentrated waste streams. The 2- and 4-substituted halophenols may undergo photochemical aryl-halogen bond heterolysis upon irradiation to give an aryl cation. The aryl cation can be attacked by water to give the corresponding hydroxylated derivative, or may deprotonate to generate alpha- and gamma-ketocarbenes, respectively. Following their formation, the singlet alpha-ketocarbenes may undergo Wolff rearrangements to cyclopentadiene-ketenes that are subsequently hydrolyzed to cyclopentadiene carboxylic acids. The triplet alpha- and gamma-ketocarbenes are attacked by oxygen and hydrolyzed to give benzoquinones, directly hydrolyzed to yield hydroquinones, reduced to give phenols, or could take part in coupling reactions in highly concentrated waste streams to give dimers and hydroxybiaryl complexes. Additional studies in natural water samples are required to assess the relative importance of these direct irradiation mechanisms relative to indirect photolysis and other abiotic and biotic degradation and environmental partitioning pathways across the continuum of marine, freshwater, and wastewater biogeochemical signatures.     

Looking under the hood of local adaptation plans: shedding light on the actions prioritized to build local resilience to climate change

In the face of a changing climate, many United States (US) local governments are creating plans to prepare. These plans layout how a community is vulnerable to existing and future changes in climate as well as what actions they propose taking to prepare. The actions included in these plans provide insight into what local governments feel they have the ability to undertake, as well as what actions they believe are important to building resilience. To date, little to no analysis has been conducted on the content of these plans, leaving researchers, practitioners, and those supporting communities with limited understanding of what gaps need to be filled or how best to support locally prioritized climate action. This paper analyzes the content of 43 stand alone climate adaptation plans from US local communities to identify the types of actions proposed and how those actions compare to what researchers indicate the communities should be prioritizing based on regional climate projections. The results indicate that local communities include numerous and varied actions in their adaptation plans and that the majority of communities are selecting actions that are theoretically appropriate given projected changes in regional climate. Yet some types of actions, such as building codes and advocacy, are not being widely used. These results contrast with previous studies, which found that local communities focus primarily on capacity building approaches. Findings also demonstrate that plans rarely contain significant details about how actions will be implemented, raising questions about whether plans will translate into real-world projects.     

Occurrence and congener profiles of polybrominated diphenyl ethers (PBDEs) in environmental samples from coastal British Columbia, Canada

Environmental levels and detailed congener profiles (31 congeners and 3 coeluting congener groups) of polybrominated diphenyl ethers (PBDEs) were assessed in a number of biota samples taken over a large geographic range covering harbours and industrial sites on Canada's West Coast. Additionally, PBDE congener profiles were determined using semipermeable membrane devices (SPMDs) deployed in the Fraser River, the river in Western Canada with the largest industrial activity. PBDE levels detected in biota were between 4 and 2300 ng/g lipid and these levels were compared with those reported in selected European biota to provide a wider perspective on PBDE contamination on Canada's West Coast. Thirteen-congener PBDE patterns in the environmental samples were examined using principal component analysis (PCA), and additionally, comparisons were made between the PBDE profiles in the sample groups and commercially used PBDE technical mixtures (e.g., Bromkals) on a percent composition basis. PCA on congener specific data revealed that PBDE patterns are remarkably similar over a wide geographical range in Western Canada, however, the general pattern in environmental samples varies significantly from those of the predominant technical mixtures. Finally, correlations between PBDE and other persistent and toxic co-occurring contaminants found in Dungeness crab were determined.     

AIRPORT WASTES AND WATER QUALITY1

ABSTRACT: Waste waters from various operations at the Miami International Airport are characterized. Servicing, maintenance, overhauling, and washing of aircraft seem to be the most significant waste water producing operations. Pollutional constitutents commonly found in the airport wastes include acids, alkalis, detergents, oil, grease, and oxygen demanding substances. Phenols are of concern when stripping and repainting operations occur. Although most airport wastes may be treatable, a great reduction in influent load can be achieved by proper housekeeping methods.