The effects of powerboat emissions on the water quality of Loch Lomond

Bannan, Mark (1999) The effects of powerboat emissions on the water quality of Loch Lomond. PhD thesis, University of Glasgow.

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Recently, there has been increased concern about the potential impact of
powerboating on freshwater ecosystems. In the case of Loch Lomond, such concern led
to the commencement of a programme of boat counting surveys in 1989. In these
surveys, it was found that maximum boat numbers are increasing in Loch Lomond. As a
logical progression from these surveys, the present study examined the impact of
powerboat chemical pollution on the water quality of Loch Lomond.
In the first stage of this study, the scale of powerboat pollution was assessed.
This was achieved by constructing a simple mathematical model to estimate the total
annual discharge of hydrocarbons (HCs) from powerboat emissions into Loch Lomond.
By using boat census data and published information about the emission rates of
different types of powerboat engines, the total annual input for Loch Lomond was
estimated at 25.50 tonnes in 1989 and this input has greatly increased since then. This
indicates that there is real potential for hydrocarbon (HC) pollution of Loch Lomond
from powerboat operation. Most of the HC material discharged emanated from
speedboats powered by outboard motors.
To identify and quantify HC pollutant compounds entering water from outboard
engines, Gas Chromatography-Mass Spectrometry (GC-MS) analysis was performed on
water subject to a controlled pollution discharge from an outboard motor. Altogether, 47
compounds were detected in this exhaust-polluted water (EPW), with most of these
being volatile aromatic HCs, such as benzene and alkylated benzenes.
Water samples were also taken from three sites in Loch Lomond on two
occasions: once in winter, during negligible boat activity and once in summer, at a time
of high powerboat activity. No HCs were detected in winter, but some volatile aromatic
HC compounds were clearly detectable in summer. These compounds were the same as
those most abundant in EPW and found in similar relative proportions. Further experiments in this study involved the analysis of a large number of
water samples. To enable this, it was necessary to develop an appropriate new method
for the analysis of powerboat exhaust pollutants, which are mostly aromatic HC. All
aromatic HCs fluoresce and the new method involved fluorescence spectroscopy
analysis, following sample purification by normal-phase column chromatography. This
technique is non-destructive allowing subsequent confirmatory analysis by GC-MS. It
was found that the new method was fast, precise, highly sensitive and specific to volatile
aromatic HCs.
The capability of measuring HCs in a large number of samples allowed
previously unfeasible experiments investigating:
1) The geographical distribution of powerboat exhaust HCs in Loch Lomond.
2) The depth profile of powerboat exhaust pollutants in the top 1.5 m of the water
3) Recovery of water quality, following peak weekend boat activity in summer.
It was found that:
1) Volatile aromatic HCs from powerboat exhaust are detectable over much of Loch
Lomond on days of heavy powerboat activity, with concentrations of up to 37 ug.l"
2) Pollutant HCs are found at depths of at least 1.5 m, and are not confined to the
surface microlayer (100 urn), The HC distribution with depth was mostly uniform in
the field and this was confirmed in controlled experiments in a tank.
3) Recovery of water quality was difficult to demonstrate in the field, possibly as
pollution incidents occur continually during summer.
4) HC concentration declined in controlled experiments, in which water was subjected
by a controlled pollution discharge from an outboard motor. The time taken for the
HC concentration to reach 50 % of the initial HC loading varied but was
approximately 7 - 9 days.
The toxicity of EPW was investigated by performing 24 hour LC50 (Lethal
Concentration for 50 % of test organisms) tests, using the water flea, Daphnia magna
(an international standard test organism). The mean LC50 recorded in this study,
expressed as the total concentrations ofHC compounds, was 3.72 mg.l". Previous studies suggest that multiplying the Le50 for D. magna by an
application factor of 0.001 gives an approximate safe level of a pollutant. Using data
collected in this study, a safe level of exhaust He compounds of 3.72 Jlg.r1 would
result. In summer, during times of high powerboat activity, such levels are exceeded at
many locations in Loch Lomond.
The current study has shown that He pollution from a relatively small number of
inefficient powered recreational craft using Loch Lomond poses a potential threat to the
maintenance of water quality.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Q Science > QH Natural history > QH301 Biology
Colleges/Schools: College of Science and Engineering
Supervisor's Name: Adams, Dr. Colin E. and Tippett, Dr. Roger
Date of Award: 1999
Depositing User: Ms Mary Anne Meyering
Unique ID: glathesis:1999-5325
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 26 Jun 2014 14:13
Last Modified: 10 Oct 2014 09:55

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