RIASSUNTO
Abstract
This paper presents a survey of marine toxicity and biodegradability data for surfactants used in the petroleum industry.
Surfactants are key chemicals in the formulation of products such as emulsifiers, demulsifiers, dispersants and inhibitors. They are also used directly as foaming and defoaming agents. Because they function at low concentrations, below 1%, and have a tendency to adsorb on solid surfaces, their long-term environmental effects are minimal. In applications such as cementing, surfactants cannot migrate into the environment and, thus, have no bioavailability.
The possibility of environmental contamination has caused well operators and regulatory agencies to require fish toxicity and persistence data for products used in servicing wells. This data persistence data for products used in servicing wells. This data has been organized for nonionic, anionic, cationic and amphoteric surfactants. Nonionic surfactants are toxic to fish at concentrations below 10 mg/L to over 2500 mg/L depending on their chemical compositions. Anionic surfactants are toxic to fish at concentrations under 1 mg/L to several hundred mg/L depending on their chemical compositions. Cationic and amphoteric surfactants are generally toxic to fish at concentrations below 50 mg/L.
Overall efforts are aimed at low toxicity and high biodegradability with the least compromise in product efficiency. This requires the continual testing and environmental evaluation of surfactants summarized herein.
Introduction
In keeping with long-standing corporate policy, environmental data has been required for chemical products used in the petroleum-production industry. Minimal data must include petroleum-production industry. Minimal data must include acute mammalian oral toxicity, skin toxicity, effects of eye contact, biodegradability data and toxicity to fish and invertebrates. The fish and invertebrate data have generally involved only fresh water species such as fathead minnows (Pimephales promelas) or rainbow trout (Salmo gairdneri) and the invertebrate water flea (Daphnia magna).
Studies of well flow-back recoveries of cationic and nonionic surfactants were carried out in carefully designed field tests and show that as much as two-thirds of a surfactant may not return with produced fluids. This further reduces their potential toxic impact on marine organisms.
Partition coefficients between 1-octanol and water were Partition coefficients between 1-octanol and water were determined for a number of surfactants. The coefficients are too low to suggest any bioaccumulation potential and are listed in this paper for reference purposes.
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