Summary
Determination of the potential of surfactants to bioaccumulate in marine
species has long been problematic in the chemical-hazard and
environmental-impact assessments performed for offshore operations. Recently,
this issue has become increasingly significant because regulators have invoked
the precautionary principle and assume that all surfactants with molecular
weight of less than 700 will bioaccumulate, leading to an increased number of
oilfield-chemical products labeled as environmentally unacceptable.
The relationship between the bioconcentration factor (BCF) of nonsurfactant
substances and their corresponding octanol/water partition coefficient
(Pow) value is well studied, and many relationships have been
developed. Log Pow is generally, therefore, used as a surrogate for the BCF of
nonsurfactant substances.
This methodology cannot be applied directly to surfactants because the
formal log Pow of such substances is difficult, if not
impossible, to determine accurately. By their very nature, surfactants tend to
form emulsions or accumulate at interfaces; therefore, the standard OECD 107
[Test No. 107: Partition Coefficient (n-octanol /water): Shake Flask Method
1995] or OECD 117 [Test No. 117: Partition Coefficient (n-octanol
/water), HPLC Method 2004] protocols cannot be used.
This paper describes a simple method for accurately determining the BCF of
linear alcohol ethoxylates (LAEs), an important group of nonionic surfactants
that are commonly used in the oil industry. Quantitative structure-activity
relationship (QSAR) software built on fragment contributions averaged over a
large number of mostly nonsurfactant substances is initially used to calculate
a pseudolog Pow. This hydrophobic parameter is then
correlated to BCF values determined in flow-through experiments, with excellent
agreement (R2 > 0.99). The method involves no animal
testing, is inexpensive to set up and perform, is accessible to all, is quick
and easy to use and verify, and gives clear output.
© 2011. Society of Petroleum Engineers
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History
- Original manuscript received:
30 July 2009
- Meeting paper published:
9 September 2009
- Revised manuscript received:
2 October 2010
- Manuscript approved:
18 January 2011
- Published online:
11 July 2011
- Version of record:
10 August 2011
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