No abstract

A procedure for the determination and confirmation of acidic herbicides In water Is described. This method is applicable to 13 commonly used herbicides, including the monochlorinated ones, at μg/L and sub-μg/L levels. The water sample is acidified to pH < 2 and extracted by dichloromethane. The herbicides are converted into their pentafluorobenzyl (PFB) derivatives and the products are cleaned up on a silica gel column. A gel permeation cleanup using a Bio-Beads S-X3 column is included to remove the PFB esters of fatty acids, which are the major Interferences in the final analysis using electron capture detection (ECD). Confirmation of herbicides employing electron Impact and negative ion chemical lonlzatlon/ mass spectrometry (NICI/MS) is discussed and applied to river water samples. The mean recoveries of herbicides for water samples fortified at 1 and 0.1 μg/L range from 45 to over 90%. The detection limit of herbicides in natural water samples is 0.05 μg/L with ECD and 0.02 μg/L with NICI/MS.

Can. J. Chem. 65, 1086Chem. 65, (1987.Analytical methodology for polychlorinated dioxins and furans (PCDDs and PCDFs) in environmental samples is not standardized. Many variations exist for the extraction, cleanup, quantitation, and confirmation of these compounds and reported detection limits and recoveries vary over several orders of magnitude. This paper describes research carried out at the Canada Centre for Inland Waters over the past seven or eight years to develop reliable methodology at ultratrace levels (10-'2-10-l 5 g/g) applicable to a wide range of environmental samples. Extraction techniques are described for biological tissue (fish, clams, leaches, eggs), fly ash, sediments, and water. Detailed cleanup procedures for the various matrices consist of most or all of the following: gel permeation chromatography liquid/liquid extraction with Na3P04, liquid/liquid extraction with H2S04, basic alumina chromatography, and carbon fibre chromatography. Preliminary screening of the cleaned extracts is achieved by gas chromatography equipped with a mass selective detector and positive identification by gas chromatography /mass spectrometry operated in electron impact and chemical ionization modes and with full scan and multiple ion detection. Custom software permitting the analysis of a wide range of compounds in a single run by gc/ms is reported. The presence of specific isomers of PCDDs and PCDFs is confirmed by high resolution gas chromatography /mass spectrometry. A radioimmunoassay screening procedure for PCDDs in environmental samples is also described. Les mtthodes d'analyse des dioxinnes et des furannes polychlorts (DPC et FPC) ne sont pas standardisees. Plusieurs variations existent pour l'extraction, le nettoyage, la quantification et la confirmation de la prtsence de ces composCs; de plus, les limites de dttection ainsi que les taux de rtcuptration rapportCs varient par plusieurs ordres de grandeur. Dans ce travail, on dtcrit les etudes effectukes au cours des 7 a 8 dernikres anntes au centre canadien des eaux inttrieures dans le but de dtvelopper une mtthodologie applicable a des niveaux d'ultratraces (lo-" h 10-g/g) et a un grand Cventail d'tchantillons prtlevts dans I'environnement. On dtcrit des techniques d'extraction pour des tissus biologiques (poissons, moules, eaux de lessivage et oeufs), des suies, des sediments et des tchantillons d'eau. Les diverses mCthodes dCtaillCes proposCes pour le nettoyage de diverses matrices comportent la plupart ou toutes les techniques suivantes: chromatographie par permCation de gel; extraction liquide/liquide avec du Na3P04; extraction liquide/liquide avec du &So4; chromatographie standards sur de l'alumine ou des fibres de charbon.On a effectut des essais prtliminaires sur des extraits IavCs en faisant appel a la chromatographie en phase gazeuse couplte h un dttecteur sClectif de masses; on a proctdC I'identification positive par chromatographie en phase gazeuse couplCe la spectromCtrie de masse, optrCe soit dans le mode d'impact Clectronique ou d'ionisat...

No abstract

Terminal lakes throughout the American West provide important amenity and environmental values, but many are shrinking due to reduced inflows and warming temperatures. In California's Imperial Valley, agricultural water use reductions diminish inflows supporting the Salton Sea, a terminal desert lake and important environmental amenity for both the region and the state as a whole. The costs of these reduced inflows are difficult to monetize yet complicate management decisions. We assess the costs of potential future drought‐induced transfers by linking novel hydrologic scenarios to an economic framework for quantifying local and regional damages based on existing estimates of non‐market environmental values from the literature. The costs of lost wetland ecosystems, increases in particulate matter from exposed playa, and other local disamenities are substantial. For the scenarios considered, they range between approximately $500 million and $1 billion in present value (2019 USD). Estimated damages per acre‐foot (or thousand m3) of reallocated water exceed several thousand dollars. The majority arise from loss of wetland habitat; incremental particulate matter damages are relatively modest in our modeling but exacerbate salient air quality issues in the region. Interest in reallocating water from Imperial Valley, the largest user of Colorado River water, to other applications will increase over time. Our work highlights the importance of evaluating the impacts of such efforts.