Toxic chemicals, volatilization from water

The U.S. ERA currently supports and maintains the WASP model, including various versions from 4 through 7 (Ambrose et al., 1988 1993 Wool et al., 2001). The first ERA public domain WASP applications to examine toxic chemicals in receiving waters and sediments date back to late 1980s with evaluations of volatile organics in the Delaware Estuary (Ambrose, 1987) and heavy metals in the Deep River, North Carolina (JRB, 1984). As a public domain model, various enhancements of the WASP model have been made over the years in order to address site-specific needs and improve on the standard transport and kinetic formulations to simulate a variety of toxics, especially hydrophobic organic chemicals (HOCs) and metals. Several modified versions of the WASP model incorporate settling and resuspension functions that are not available in the EPA-supported model. The WASP model discussion... 

Mackay, D. (1981) Environmental and laboratory rates of volatilization of toxic chemicals from water. In Hazardous Assessment of Chemicals, Current Development. Volume 1, Academic Press. 

Quantitative estimation of ventilation by indirect methods in mussels requires four assumptions (16) a) reduction of concentration results from uptake, b) constant ventilation (pumping) rate, c) uptake of a constant percentage of concentration (first order process), d) homogeneity of the test solution at all times. Our transport studies have utilized antipy-rine (22, 23) a water soluble, stable chemical of low acute toxicity to mussels. It is readily dissolved in ocean water or Instant Ocean and is neither adsorbed nor volatilized from the 300 ml test system. Mussels pump throughout the 4 hour test period and this action is apparently sufficient to insure homogeneity of the solution. Inspection of early uptake and elimination curves (antipyrine concentration as a function of time) prompted use of Coughlan s equation (16) for water transport. 

Atrazine, however, would be a nonvolatile compound - 1/(HKg)>> /Kl -because equilibrium is strongly to the liquid phase due to the small Henry s law constant. There is also a strong gas phase resistance to the transfer. Atrazine was manufactured to remain in the hquid phase, where it will act as a herbicide, rather than in the gas phase, where farm personnel will be breathing this toxic chemical. If you were going to pick a compound that is not made by humans from the list of those that are a gas or liquid in our environment, a good guess is that it would be a volatile or semivolatile compound. There are only a few nonionic environmental compounds that are nonvolatile. Remarkably, one of them is water. While the atmosphere may be as much as 3 % water, the water bodies in the world are very close to 100% water. The equilibrium is strongly to the hquid side because of the small Henry s law constant. 

Environmental and Laboratory Rates of Volatilization of Toxic Chemicals from Water... 

A common use of vacuums involves their utility for removing volatiles from reactions or filtering materials. It is common to use house vacuum systems, water aspirators, or vacuum pumps for these purposes. Besides the risks of implosions, there can be potential hazards from exposures to toxic products released from the vacuum exhaust. Maintenance workers have been exposed to toxic chemicals that were allowed to enter into a house vacuum system. Others have been exposed to toxic products from unventilated vacuum pumps used to evaporate volatile organics. It is important to use techniques to set up traps to prevent these kinds of releases of hazardous materials. 

Most general-purpose release agents have been developed for this market in part because of their low toxicity and chemical inertness and do not usually present health and safety problems. Some of the solvent dispersions require appropriate care in handling volatile solvents, and many supphers are offering water-based alternatives. Some of the sohds, particularly finely divided hydrophobic sohds, can also present inhalation problems. Some of the metallic soaps are toxic, although there is a trend away from the heavier, more toxic metals such as lead. The reactive type of release coating with monomers, prepolymers, and catalysts often presents specific handling difficulties. The potential user with health and safety questions is advised to consult the manufacturer directly. 

The new antimicrobial is an order of magnitude less toxic, several orders of magnitude less volatile, easier to handle, more compatible with other water treatment chemicals, more effective against biofilms, and it generates less than half the disinfection by-products compared to chlorine or other alternatives. One hundred fifty billion gallons of industrial water have by now been successfully treated globally. Use of this new antimicrobial has substantially reduced environmental and human health risks from industrial water treatment by replacing nearly thirty million pounds of chlorine. The new product is proven to comparatively perform better, more safely, and it is substantially easier to apply than chlorine. 

STABREX is easier and simpler to use compared to any other oxidant available for industrial water treatment. The product is pumped directly from returnable transporters (PortaFeed Systems)17 with standard chemical feed equipment. Previously, the only practical ways to apply bromine were to oxidize bromide solutions on-site with chlorine in dual liquid feed systems, or with one of the solid organically-stabilized bromine products applied from sidestream erosion feeders. The former is cumbersome and complex, and the latter is prone to dusting and difficult to control. Other oxidants require complex handling and feed of toxic volatile gases, unstable liquids, multiple-component products, or reactive solids. Simplicity in use results in reduced risk to workers and to the environment. 

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