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Evaluation of the influence of various factors upon HNS spill impact
David Sheahan, Mohammad AL-Sarawi*, John
Aldridge, Thomas McGowan, Mark Kirby, Brett Lyons, Marta Vannoni
Centre for Environment Fisheries and Aquaculture Science (Cefas)
* Head Department of Earth & Environmental Sciences, Kuwait University
Trends in seaborne trade
• Over the past forty years, world seaborne shipments have risen from 2.6 billion tons in 1970 to 9.1 billion tons in 2012 (UNCTAD, 2013)
• A large percentage contribution from developing economies in world seaborne trade, 2012
0 10 20 30 40 50 60
Perc
enta
ge
Loaded
Unloaded
Trends in oil spills
• The number of oil spills and size of spill has steadily reduced over the decades
http://www.itopf.com/knowledge-resources/data-statistics/statistics/
0 10 20 30 40 50 60
Number of spills % >700 ton
Over 50% > 700 ton
Trends in HNS spills
• Cedre reports of pollution by HNS spills >10m3 indicate an increasing trend over the period 1998 -2013 from 28 -77
• Most incidents involve chemical tankers but also
bulk carriers and container ships
http://www.cedre.fr/en/publication/information-day/2014.php
The importance of chemical properties • HNS chemicals have a wide range of properties
that determine where they end up in the environment and what they effect
Density Solubility Volatility
The importance of chemical behaviour
The importance of environmental factors
Sea temperature Salinity Estuarine 20 - ≤30
Depth, Suspended sediment, Light
Coastal UK 30 – 34.5
Arabian Gulf 36 - 44
Offshore UK ≥34.5
Types of chemical spilt
• ARCOPOLplus project identified 23 substances as of priority based on frequency of transport, occurrence of previous incidents, behaviour in seawater and toxicity
To fill data gaps a subset of 7 HNS
were identified for toxicity tests in the laboratory
Choice of chemical for study
• Aniline industry intermediate imports Netherlands 2012 aniline and derivatives around 300,000 tonne (UN commodities trade) – previous spills – Cason 1987 Spanish coast
• Zinc compounds and zinc sulphate - e.g. bulk up to 1000
kg sacs and zinc ores (> 2 million tonnes imported EU 28 2013, UN commodities) –previous spills – Thor Emilie 2000, Mediterranean, Jambo 2003, West coast Scotland
Choice of Model • To simulate chemical plumes the hydrodynamic transport
model CHEMMAP was used (McCay et al., 2006) • Model represents the chemical spill with particles that
follow the water flow and are subject to wind movement
• Chemical properties influence spill behaviour as do: (i) rate of chemical release, (ii) speed of water, (iii) depth water x depth of release, (iv) mixing, horizontal x vertical
Effects of temperature and salinity on spill profiles and effects (Aniline)
30oC
10oC
Salinity - negligible effect between 30 and 40 ppt
Temperature – 25% less Aniline in water column at 30oC
0
4
8
12
16
25 30 35 40 45
LC50
Salinity (ppt)
20°C aniline (Tisbe)
20°C aniline
0
0.1
0.2
0.3
0.4
25 30 35 40 45
LC50
Salinity (ppt)
20°C zinc
20°C zinc
Effects of salinity on HNS toxicity
Copepod
Effects of temperature on HNS toxicity
Zhou et al., 2014 (metal toxicity) range marine species chemical toxicity low at op=mum temperature increase either side (A) or increasing toxicity with temperature increase (B). Data indicate trend for species sensi=vity for metals zinc, chromium and cadmium 1-‐3 =mes increase sensi=vity with 15oC temperature increase.
A B
Conclusions Aniline more toxic at low (30 ppt) relative to intermediate salinity (35 ppt) and high (40ppt) salinity, zinc less toxic at both higher salinities Chemical modelling aniline - 10oC increase 10 - 25% decrease concentration Literature suggests some chemicals 1-3 times increase in toxicity with increase around15oC
For Salinity and temperature
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120
0 6 12 18 24 30 36 42 48 A
nilin
e co
ncen
trat
ion
(mg
l-1)
Time (hours)
spill profile
20km offshore Nearshore
Choice of spill profile – two main types considered
Poole Bay site, ‘snapshot 8 hours after plume start’ 1000 tonne aniline release over 4 hour period -. Output shows 1) release point, 2) spatial
extent of plume at the seabed, 3) vertical distribution (along line AB) of derived chemical concentrations together with the bathymetry and the
particles that represent the modelled plume (blue dots).
1 km
5 -10ppm
50 -55ppm
Choice of spill scenario
Creating a spill profile in the laboratory
(B) Small test chamber
(C ) Peristaltic pump supplies chemical to test beaker
(D) Close up of test beaker
(A) Test species
Copepod
TT 0
20
40
60
80
100
120
0 6 12 18 24 30 36 42 48 Time (hours)
Multiple peak spill profile red line actual concentration achieved in the experiments.
Creating a spill profile in the laboratory
TWA(13 mg l-1) 80% mortality at 48h Constant exposure ∼ 10 mg l-1 80% 48h But exposure to 300 mg l-1 for 2 hours negligible effect after 48 hours For aniline there is some capacity for recovery if periods of low or no exposure between peaks
Aniline
Profile studies for other species and HNS (Seaweed germlings and Benzalkonium chloride)
0
20
40
60
80
100
CONTROL TWA SPILL
Germina(
on (%
)
0
0.04
0.08
0.12
0.16
CONTROL TWA SPILL
Fron
d Lenght (m
m)
Conclusions
Some chemicals specific mode of action little recovery even brief exposure to single high peak, other cases multiple peaks tolerated if time between peaks Different life stages different sensitivities may mean brief high concentration peaks more heavily impact at different times/seasons
For Profiles
Overall conclusions
Chemical spills coastal areas represent most risk threat to humans, operation coastal industries and various wildlife species in shallower water. Where salinity lower and temperature higher in these same areas likely increase susceptibility exposed organisms. In regions where high salinity and high temperature chemical dispersion may be more limited and loss processes higher rate this may limit extent of impact
Acknowledgements This work and ongoing studies is jointly funded by the International Tanker Owners Pollution Federation Ltd annual R&D award and Defra contract ME1314.
