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Hydrocarbons in seawater

oil and fuel spills also occur, characterized by a higher activities that cause hydrocarbon pollution sometimes
frequency. Minor incidents, such as spills from fishing escape the control of the relevant authorities or public
vessels or small commercial boats also contribute to awareness, and therefore, the extent of the impact may
chronic oil pollution. Other examples of accidental spills be underestimated. However, several investigations
include offshore drilling blowouts and subsea pipeline suggest that operational discharges from shipping
ruptures. These events can occasionally be caused by collectively release more oil into the oceans annually
corrosion, geological activity, or external damage. than catastrophic spills, probably representing the
Anthropogenic activities, including shipping traffic, main source of chronic and widespread hydrocarbon
offshore drilling, and coastal development, dictate the contamination in the sea. Some estimates indicate
frequency and type of hydrocarbon inputs. Regions that 90% of all oil discharged by ships is attributed
with intensive human activity often face chronic to deliberate, illegal dumping of oily residues from
pollution and a greater risk of large-scale spills. On the routine operations, potentially accounting for hundreds
other hand, biodiversity plays a critical role, as diverse of thousands to over 2.5 million tons of hydrocarbons
ecosystems often exhibit greater resilience and a wider annually. 29,30 Additional sources of hydrocarbons are
array of microbial communities capable of hydrocarbon characterized by urban runoff; stormwater runoff
degradation. However, highly specialized or endemic from urban areas is a diffuse but significant source
species can be particularly vulnerable to oil exposure, of oil residues and fuel. Rain washes oil, grease, and
leading to severe ecological disruption. other petroleum products from roads, parking lots,
Offshore drilling blowouts and pipeline ruptures and other impervious surfaces into drainage systems
incidents can release substantial hydrocarbons over that ultimately discharge into coastal waters. These
extended periods, often in less accessible deep-sea hydrocarbons originate from vehicle emissions, leaky
environments, making response efforts particularly engines, spills at gas stations, and industrial activities.
challenging. Quantifying global inputs from these Urban runoff usually contains a complex mixture
accidents may be complex due to the varying sizes and of petrogenic (petroleum-derived) and pyrogenic
durations of such events, but they remain a consistent (combustion-derived) hydrocarbons. While difficult to
source of episodic, localized pollution. While large quantify precisely on a global scale, studies of urban
spills grab headlines, chronic discharges contribute waterways consistently report the presence of total
a substantial, often unquantified, cumulative load extractable and aromatic hydrocarbons in sediments
of hydrocarbons to the marine environment. These and water, with concentrations varying depending on
continuous, smaller releases can have insidious long- the level of urbanization and industrial activity. Urban
31
term impacts on marine life and ecosystems. 29-33 In oil runoff varies significantly based on natural factors
and gas production, “produced water” is a byproduct (precipitation intensity and duration, soil characteristics,
that emerges to the surface along with oil and gas. This land cover, slope) and anthropogenic factors (level of
water, often of geological origin, can be highly saline urbanization, type of impervious surfaces). Quantifying
and contains various organic and inorganic compounds, pollution from urban runoff on a global scale is
including dissolved and dispersed hydrocarbons (e.g., inherently difficult. The most sophisticated models are
aliphatic hydrocarbons, benzene, toluene, ethylbenzene, based on simulating the accumulation of pollutants on
xylenes, and PAHs). The volume of produced water urban surfaces during dry weather, followed by washing
discharged globally is enormous, with estimates of during storm events, but the uncertainty in such models
millions of barrels daily. While there are treatment is often very elevated. While some detailed studies are
technologies to reduce hydrocarbon concentrations available at local and regional levels (e.g., in Europe or
before discharge, even low concentrations released the United States), reliable global data are completely
consistently can accumulate and have localized impacts, lacking. 31
particularly in coastal and shelf environments. 30,62 Atmospheric deposition of combustion products
In addition, routine operations of the global shipping may also represent a significant source of hydrocarbons
fleet contribute significantly to hydrocarbon pollution. in the environment. The combustion of fossil fuels,
These include ballast water discharges, tank cleaning whether from vehicles, industrial processes, or power
residues, and engine room bilge water. Due to the generation, releases hydrocarbons and their derivatives
continuous, point-based nature of this type of pollution, directly into the atmosphere. These airborne pollutants
it is extremely difficult to estimate its true impact can then be transported globally and deposited onto the
and overall volumetric contribution over time. Many ocean surface through wet deposition (rain, snow) and

Volume 22 Issue 6 (2025) 29 doi: 10.36922/AJWEP025290224