Maritime Traffic's Impact On Water Pollution

Maritime traffic has a significant impact on water pollution, with the shipping industry contributing heavily to global pollution and climate change. The sheer size of the industry means that it has a substantial effect on the environment, despite ships being the most energy-efficient method to transport cargo over long distances. The annual increase in shipping volume outweighs any gains made by efficiency improvements such as slow-steaming. The industry is responsible for large quantities of pollutants, including greenhouse gas emissions, air pollution, oil spills, ballast water discharges, underwater noise pollution, and chemical spills. Cruise ships, in particular, generate enormous amounts of sewage, wastewater, and solid waste, with a large portion of this waste being dumped into the sea.

Oil pollution

Accidental oil spills are the result of ship collisions, fires, groundings, human error, equipment malfunction, or natural disasters. Intentional spills, which make up a larger proportion of marine oil pollution, usually involve the illegal cleaning of ships' tanks at sea or the improper management of oily residues and ballast water.

Oil spills have devastating and irreversible effects on marine ecosystems and biodiversity. Polycyclic aromatic hydrocarbons (PAHs) in crude oil are toxic to marine life and can remain in the marine environment and sediment for years, hindering the development, reproduction, and disease resistance of many species, including fish, seabirds, mammals, invertebrates, and reefs. Oil spills can also be harmful to humans, as they can contaminate commercially important species of fish and shellfish, making them unsafe for human consumption.

The shipping industry is a major contributor to oil pollution, with tanker traffic and other shipping operations accounting for about 35% of global marine oil pollution. Oil spills from tankers and other vessels can occur during accidents or when oil is released from faulty engine systems, improper repair work, or illegal cleaning operations. In addition, the burning of heavy fuel oil by large cruise ships releases dangerous levels of sulfur and heavy metals, further contributing to oil pollution.

To combat marine oil pollution, measures such as the designation of marine protected areas, increased controls, and the use of double-hull tankers have been implemented. International conventions, such as the International Convention for the Prevention of Pollution from Ships (MARPOL), and national regulations also play a crucial role in reducing oil pollution from maritime sources.

Ballast water discharge

In addition to the ecological impact, ballast water may also contain harmful pathogens and diseases that can be transferred to native species. For instance, a form of cholera, Vibrio cholerae, arrived in Peru via ballast water in 1991, killing more than 10,000 people over three years.

To address the environmental impact of ballast water discharge, the International Maritime Organization (IMO) adopted the "International Convention for the Control and Management of Ships' Ballast Water and Sediments" in 2004. The convention aims to minimise the uptake of organisms and sediments during ballasting and requires ships to implement a ballast water management plan. The IMO convention came into force in September 2017.

Furthermore, the Environmental Protection Agency and the US Coast Guard regulate the concentration of living organisms discharged in ballast water to minimise the spread of invasive species in US waterways.

While most ships now have on-dock ballast water treatment, there are concerns about the potential release of toxic disinfection by-products from chemical treatments such as chlorination, oxidation, and ozonation. These by-products, including tri-halo methane and haloacetic acid, can reach concentrations of more than 10 μg/L and pose risks of acute toxicity, carcinogenicity, genotoxicity, and mutagenicity to aquatic organisms.

Air pollution

Maritime traffic is a major contributor to air pollution, which has adverse effects on human health and the environment. The shipping industry, which moves over 80% of the world's goods, is responsible for more than 18% of nitrogen oxides pollution and 3% of greenhouse gas emissions. These emissions, which include nitrogen oxides, sulfur oxides, and particulate matter, can cause respiratory issues such as asthma and lung inflammation, and increase the risk of heart disease and premature death.

The impact of maritime traffic on air pollution is particularly significant in coastal areas, with about 70% of ship emissions occurring within 400 km of the shore. The burning of high-sulfur fuel oil by ships results in sulfur dioxide emissions, which can cause lung inflammation and are known to have respiratory effects, increasing the risk of heart attacks when inhaled.

In addition to the direct health impacts, maritime traffic also contributes to climate change through the emission of greenhouse gases. Carbon dioxide, a primary greenhouse gas, is absorbed by seawater, leading to ocean acidification, which can have adverse effects on marine life and ecosystems.

To address these issues, regulations such as MARPOL Annex VI have been implemented to limit air pollutants from ships. The International Maritime Organization (IMO) has also adopted new sulfur emissions regulations and set targets for reducing greenhouse gas emissions. While these measures are a step in the right direction, more action is needed to mitigate the adverse effects of maritime traffic on air pollution.

Grey and blackwater pollution

Greywater and blackwater pollution are significant environmental concerns caused by maritime traffic. Greywater is wastewater from sinks, showers, galleys, laundry, and cleaning activities aboard a ship. Blackwater, on the other hand, refers to sewage or wastewater from toilets and medical facilities. Together, they contribute to water pollution and pose risks to marine ecosystems and human health.

Greywater contains various pollutants, including fats, oils, harmful chemicals, bleaches, and pathogens that affect human health. Untreated greywater can cause water quality issues and harm public health due to high bacterial loads, nutrient discharge, biological oxygen demand, and salinity impacts. It can turn septic within 24 hours if left untreated, and its discharge is particularly problematic in localized areas such as marinas, mooring locations, and sheltered bays. A large cruise ship can release around one million gallons of greywater during a week-long voyage, and this wastewater can accumulate pollutants and harm marine life.

Blackwater, or sewage, contains disease-causing bacteria and viruses that can contaminate fisheries and shellfish beds, posing risks to public health. It also contributes to nutrient build-up in ecosystems, leading to changes in habitat and the proliferation of nuisance pest species. Blackwater discharged from vessels is more concentrated than domestic sewage and can have significant environmental and public health impacts, especially when released near swimming beaches, shellfish gathering areas, and other ecologically sensitive areas.

To address these issues, regulations such as the Code of Practice for Vessel and Facility Management (marine and inland waters) have been implemented to set mandatory requirements for vessel operators managing greywater and blackwater. The International Maritime Organization (IMO) has also established regulations to control emissions and pollution from the shipping industry. Additionally, organizations are advocating for more stringent guidance on greywater discharge in the forthcoming revisions to MARPOL (International Convention for the Prevention of Pollution from Ships).

Solid waste pollution

The improper disposal of solid waste by ships has severe environmental consequences. Plastics, for example, can float in the ocean for years, endangering marine mammals and fish that may mistake them for food or become entangled in them. Other solid wastes, such as metals, glass, batteries, medical waste, and oily rags, can also have harmful effects on marine ecosystems if not disposed of properly.

To address this issue, international regulations such as MARPOL Annex V have been implemented. This regulation prohibits the discharge of garbage into the sea, with specific provisions for food waste, cargo residues, cleaning agents, and animal carcasses. Ships are required to have a garbage management plan and a garbage record book to ensure proper disposal and compliance with regulations.

Additionally, waste management teams on vessels play a crucial role in understanding and complying with waste reduction, recycling, and management strategies. The adoption of the Hong Kong International Convention for the Safe and Environmentally Sound Recycling of Ships has also led to improvements in ship recycling and waste management.

To further reduce solid waste pollution from maritime traffic, it is essential to implement waste reduction and recycling programs, improve waste disposal infrastructure at ports, and raise awareness about the environmental impact of improper waste disposal among seafarers and the general public.

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