Thursday, February 20, 2014

Shipping emissions can lead to high local ocean acidification

                                                              Image from: How 16 ships create as much pollution as all the cars in the world

From European Commission - Science for Environment Policy - 18 July 2013
Issue 337

Strong acids formed from shipping emissions can produce seasonal ‘hot spots’ of
ocean acidification, a recent study finds. These hot spots, in ocean areas close to
busy shipping lanes, could have negative effects on local marine ecology and
commercially farmed seafood species.

Oceans have become more acidic since pre-industrial times. The average global ocean pH –
which decreases with increasing acidity – has dropped by 0.1 because the seas have
absorbed 30-40% of manmade CO2. However, it is not only CO2 that can acidify oceans.
Shipping emissions, a significant source of atmospheric pollution, annually release around
9.5 million metric tons of sulphur and 16.2 million metric tons of nitric oxides.

When dissolved in seawater, these pollutants are converted into the strong sulphuric and
nitric acids, adding to ocean acidification. Increasing acidity poses a threat to marine
ecosystems, harming species such as coral and algae, as well as commercial aquaculture                   
species, such as shellfish.

The researchers used state of the art computer modelling techniques and datasets to create
a high resolution simulation of global shipping emissions’ effects on ocean acidity. The
simulation calculated the acidifying impacts of shipping sulphur and nitric oxide emissions on
a month by month basis, over one year. In addition to shipping-related influences on acidity,
the model also included many physical and environmental factors, such as ocean surface
water mixing and atmospheric effects.

The results agreed with previous studies of the average annual ocean acidification, but,
importantly, revealed significant differences between regions and seasons. Ocean
acidification was highest in the northern hemisphere, occurring in ‘hot spots’ close to coastal
areas and busy shipping lanes during the summer months. These ‘hot spots’ coincide with
peak activity of some biological processes, such as plankton blooms and fish hatching,
where they may cause greater harm. On a local scale, the acidification – a pH drop of
0.0015-0.0020 – was equal to CO2’s global annual acidifying effects.

The model did not include some coastal ocean areas, such as the Mediterranean Sea, as
there were limitations in the oceanographic atlases used. However, acidification is likely to
be high in these areas given the heavy shipping traffic from ports.

International regulation is in place to reduce shipping atmospheric sulphur emissions
through the International Maritime Organization’s Emission Control Areas (ECA), which are
in force in four ocean areas, including the Baltic and North Seas. One technology commonly
used to achieve ECA targets is ‘seawater scrubbing’, where exhaust pollutants are removed
using seawater.

This study drew on data from 2000 and 2002, prior to the enforcement of ECAs. However,
the researchers note that seawater scrubbing, without additional steps to neutralise the
acids that it produces, causes acidification in regions where biodiversity or commercial
aquaculture may be most negatively affected. These previously overlooked sources of ocean
acidification and policy impacts could be used to inform future discussions of controls
relating to shipping emissions or ocean acidification

Original article:

The study:

Shipping contributes to ocean acidification
Ida-Maja Hassellöv et al DOI: 10.1002/grl.50521


[1] The potential effect on surface water pH of emissions of SOX and NOX from global ship routes is assessed. The results indicate that regional pH reductions of the same order of magnitude as the CO2-driven acidification can occur in heavily trafficked waters. These findings have important consequences for ocean chemistry, since the sulfuric and nitric acids formed are strong acids in contrast to the weak carbonic acid formed by dissolution of CO2. Our results also provide background for discussion of expanded controls to mitigate acidification due to these shipping emissions.

 Other readings:

Ship impacts on the marine atmosphere: insights into the contribution of shipping emissions to the properties of marine aerosol and clouds

M. M. Coggon et al. doi:10.5194/acp-12-8439-2012

Abstract. We report properties of marine aerosol and clouds measured in the shipping lanes between Monterey Bay and San Francisco off the coast of Central California. Using a suite of aerosol instrumentation onboard the CIRPAS Twin Otter aircraft, these measurements represent a unique set of data contrasting the properties of clean and ship-impacted marine air masses in dry aerosol and cloud droplet residuals. Below-cloud aerosol exhibited average mass and number concentrations of 2 μg m−3 and 510 cm−3, respectively, which are consistent with previous studies performed off the coast of California. Enhancements in vanadium and cloud droplet number concentrations are observed concurrently with a decrease in cloud water pH, suggesting that periods of high aerosol loading are primarily linked to increased ship influence. Mass spectra from a compact time-of-flight Aerodyne aerosol mass spectrometer reveal an enhancement in the fraction of organic at m/z 42 (f42) and 99 (f99) in ship-impacted clouds. These ions are well correlated to each other (R2>0.64) both in and out of cloud and constitute 14% (f44) and 3% (f99) of organic mass during periods of enhanced sulfate. High-resolution mass spectral analysis of these masses from ship measurements suggests that the ions responsible for this variation were oxidized, possibly due to cloud processing. We propose that the organic fractions of these ions be used as a metric for determining the extent to which cloud-processed ship emissions impact the marine atmosphere where (f42 > 0.15; f99 > 0.04) would imply heavy influence from shipping emissions, (0.05 < f42 < 0.15; 0.01 < f99 < 0.04) would imply moderate, but persistent, influences from ships, and (f42 < 0.05; f99 < 0.01) would imply clean, non-ship-influenced air.

1 Introduction
(My emphasis) Ship exhaust is estimated to account for 14 and 16 % of global NOx and SOx emissions, respectively (Corbett and Fischbeck, 1997). Models show that ship emissions also con-
tribute 1.67 Tg yr−1 to global particulate matter, which is early equivalent to current estimates of particulate matter emitted by all on-road vehicles (Eyring et al., 2005; Yan et al., 2011).


How 16 ships create as much pollution as all the cars in the world
By Fred Pearce
UPDATED: 17:13 EST, 21 November 2009

Read more:

“We've all noticed it. The filthy black smoke kicked out by funnels on cross-Channel ferries, cruise liners, container ships, oil tankers and even tugboats.

It looks foul, and leaves a brown haze across ports and shipping lanes. But what hasn’t been clear until now is that it is also a major killer, probably causing thousands of deaths in Britain alone.

As ships get bigger, the pollution is getting worse. The most staggering statistic of all is that just 16 of the world’s largest ships can produce as much lung-clogging sulphur pollution as all the world’s cars.

Because of their colossal engines, each as heavy as a small ship, these super-vessels use as much fuel as small power stations.

But, unlike power stations or cars, they can burn the cheapest, filthiest, high-sulphur fuel: the thick residues left behind in refineries after the lighter liquids have been taken. The stuff nobody on land is allowed to use.

Thanks to decisions taken in London by the body that polices world shipping, this pollution could kill as many as a million more people in the coming decade – even though a simple change in the rules could stop it.

There are now an estimated 100,000 ships on the seas, and the fleet is growing fast as goods are ferried in vast quantities from Asian industrial powerhouses to consumers in Europe and North America”

Read more:

NOAA-led researchers discover ocean acidity is dissolving shells of tiny snails off the U.S. West Coast
April 30, 2014
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