Ships: Water And Air Polluters?

Shipping is the most energy-efficient method to transport cargo, but the industry's sheer size means it has a significant environmental impact. Ships burn heavy fuel oil, which leads to harmful air pollution, including nitrous oxide, sulfur dioxide, and particulate matter. Marine diesel engines contribute to ozone and carbon monoxide, exceeding air quality standards, and impacting human health. Additionally, ships produce water pollution through ballast water discharge, which contains biological materials, and oily bilge water, which, even in minute concentrations, can kill fish. Shipping is also a source of acoustic pollution, threatening marine life that relies on sound. To address these issues, regulations and initiatives have been implemented, such as emission control areas and alternative fuel research, but more international action is needed to mitigate the environmental impact of shipping on our oceans and atmosphere.

Ships burn heavy fuel oil, causing air pollution

Commercial ships burn heavy fuel oil, which releases harmful air pollutants into the atmosphere. These pollutants include nitrogen oxides, sulphur dioxide, carbon monoxide, carbon dioxide, hydrocarbons, and particulate matter. Nitrogen oxide emissions are a product of high combustion temperatures, while sulphur emissions depend on the type of fuel used.

The burning of heavy fuel oil by ships has significant environmental and health impacts. Nitrogen oxides contribute to smog formation, degrade air quality, and harm aquatic life by causing toxic algal blooms and reducing water oxygen levels. Sulphur dioxide emissions lead to acid rain, which can travel hundreds of kilometres inland and affect both the environment and human populations.

Additionally, carbon monoxide emissions contribute to ozone and carbon monoxide nonattainment, adversely affecting air quality and human health. The US Environmental Protection Agency (EPA) has classified diesel exhaust, which contains carbon monoxide and particulate matter, as a likely human carcinogen.

To mitigate the environmental and health impacts of burning heavy fuel oil, some ships have been equipped with "scrubbers" to clean exhaust gases. However, these devices can inadvertently pump pollution into the sea. Alternative measures to reduce air pollution from ships include speed reduction, which decreases fuel consumption and, in turn, lowers air pollutant emissions. The development of alternative fuels, such as green ammonia, hydrogen, and biofuels, also offers a promising approach to reducing the reliance on heavy fuel oil and mitigating its environmental and health consequences.

Ships' ballast water discharge can contain biological pollutants

Ships can pollute both the water and the air. While air pollution is caused by the burning of heavy fuel oil, water pollution can be caused by ballast water discharge, which often contains biological pollutants.

Cruise ships, large tankers, and bulk cargo carriers use a lot of ballast water, which is often taken on in coastal waters after ships discharge wastewater or unload cargo. This ballast water is then discharged at the next port of call when more cargo is loaded.

Ballast water discharge typically contains biological materials, including plants, animals, viruses, and bacteria. These materials often include non-native, invasive, exotic species that can cause ecological and economic damage to aquatic ecosystems, as well as serious human health issues, including death. For example, a form of cholera, Vibrio cholerae, reportedly arrived in Peru via ballast water in 1991, killing more than 10,000 people over the next three years. The zebra mussel, native to the Caspian and Black Seas, also arrived in Lake St. through ballast tanks.

To minimize the spread of invasive species, the Environmental Protection Agency and the U.S. Coast Guard regulate the concentration of living organisms discharged in ballast water. The International Maritime Organization (IMO) has also adopted the "International Convention for the Control and Management of Ships' Ballast Water and Sediments" to control the environmental damage from ballast water. This convention requires all ships to implement a "Ballast Water Management Plan" and carry out ballast water management procedures to a given standard.

Various treatment methods have been developed to treat ballast water, such as hydrodynamic cavitation, which is effective in destroying microorganisms and micro-pollutants.

Acoustic pollution from ships harms marine life

Ships pollute both the water and the air. They are responsible for harmful air pollution, water pollution, acoustic pollution, and oil pollution.

Marine life relies on underwater sounds for essential life functions such as searching for prey, avoiding predators, locating offspring, and finding a mate. Therefore, underwater noise pollution from ships can have a detrimental impact on marine life.

The noise produced by ships can travel long distances, and marine species that rely on sound for orientation, communication, and feeding can be harmed by this sound pollution. The major contributors to this noise pollution include cargo vessels, which produce very low-frequency sounds that can travel hundreds of kilometres underwater. As global shipping operates day and night, the constant drone masks the natural soundtrack of the sea and interferes with important biological and ecological processes over vast distances.

Marine mammals, such as whales, dolphins, and porpoises, are particularly affected by underwater noise pollution. They rely on sound to communicate, locate mates and prey, navigate, and defend their territories. Increased ambient noise from ships can mask these signals, making it difficult for them to find a mate and organize behaviours within their groups. For example, increased ship noise has caused bottlenose dolphins to simplify their vocal calls, potentially reducing the information content of their calls and decreasing effective communication.

Underwater noise can also cause temporary or permanent hearing loss, behavioural and physiological changes, injury, and even death in marine mammals. Very loud sounds can cause panic, leading to rapid ascents to escape the noise, which can result in decompression sickness and tissue damage. Additionally, the loudest underwater noise comes from naval sonar devices, which can cause mass stranding events, as seen with beaked whales.

To mitigate the impact of acoustic pollution from ships, the International Maritime Organization (IMO) has established guidelines encouraging the adoption of quieter ship designs and technologies. These measures include modifications to hull designs, the use of quieter propellers, and the implementation of bubble curtains during offshore construction to absorb and scatter sound waves. Declaring noise-sensitive habitats as Marine Protected Areas (MPAs) can also help regulate human activities in critical regions.

Bilge water contains oil, solid waste, and other harmful chemicals

The environmental impact of shipping includes air pollution, water pollution, acoustic pollution, and oil pollution. While shipping is the most energy-efficient method to move a given mass of cargo over a given distance, the sheer size of the industry means that it has a significant effect on the environment.

Bilge water is a mixture of various substances, including fresh water, seawater, oil, sludge, chemicals, and other fluids. Oil enters the bilge well through fuel oil purifiers, leakage in the fuel line, and oil spills. Bilge water also contains solid wastes and other harmful chemicals, such as hydrocarbon residue, which can be extremely harmful to marine life and water quality. A typical large cruise ship generates an average of 8 tonnes of oily bilge water for each 24 hours of operation.

To prevent the discharge of untreated bilge water, which can have detrimental impacts, bilge water is passed through an oily water separator to reduce the level of suspended oil particles. The clean water is then discharged, while the extracted oil can be reused, incinerated, or offloaded at the port. However, if the separator is faulty or bypassed, untreated oily bilge water can be discharged directly into the ocean.

In addition to the harmful effects of oil pollution, the solid waste generated by ships can also have negative consequences. Plastic waste, for example, is hazardous to the marine ecosystem due to ingestion and entanglement by aquatic organisms. While plastic waste is typically stored on ships and disposed of at onshore facilities, it still contributes to the overall pollution generated by the shipping industry.

Fuel and oil spills from ships pollute the water

The environmental impact of shipping includes air and water pollution, acoustic, and oil pollution. While air pollution from ships is generated by diesel engines that burn high-sulfur content fuel oil, water pollution is caused by fuel and oil spills from ships.

Oil spills are the release of liquid petroleum hydrocarbons into the environment, especially the marine ecosystem, due to human activity, and they contribute to water pollution. Oil spills can result from the release of crude oil from tankers, offshore platforms, drilling rigs, and wells. They may also involve spills of refined petroleum products such as gasoline and diesel fuel, as well as heavier fuels used by large ships, and oily refuse or waste oil. These spills can have severe environmental and economic consequences.

For instance, oil spills can harm sea creatures, ruin beaches, and make seafood unsafe to eat. Oil penetrates the structure of the plumage of birds and the fur of mammals, reducing its insulating ability and making them more vulnerable to temperature changes and less buoyant in the water. Large zones may need to be cordoned off, banning fishing activities and affecting fishermen, ship owners, and companies in the industry.

Furthermore, a large cruise ship can generate an average of 8 tonnes of oily bilge water for each 24 hours of operation. Bilge water is supposed to be filtered and cleaned before being discharged. However, if the separator used to extract the oil is faulty or bypassed, untreated oily bilge water can be discharged directly into the ocean.

Ballast water discharges by ships can also negatively impact the marine environment. Cruise ships, large tankers, and bulk cargo carriers use a lot of ballast water, often taken from coastal waters. This ballast water discharge typically contains biological materials, including invasive species that can cause ecological, economic, and human health problems.

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