Mercury speciation in the Persian Gulf sediments

Area of Science:

• Environmental Chemistry
• Marine Science
• Geochemistry

Background:

• Mercury (Hg) is a persistent environmental pollutant with significant ecological and health implications.
• Understanding mercury speciation, particularly methyl mercury (MMHg), is crucial for assessing its bioavailability and toxicity in marine ecosystems.
• Sediments act as a sink and potential source for mercury in aquatic environments.

Purpose of the Study:

• To quantify total mercury (Hg) and methyl mercury (MMHg) concentrations in marine sediments along the Iranian coast of the Persian Gulf.
• To assess the percentage of methyl mercury (MMHg) relative to total mercury (Hg).
• To investigate the relationship between mercury levels, methyl mercury fraction, and organic carbon content in marine sediments.

Main Methods:

• Collection of 78 marine sediment samples from nine transects in the Persian Gulf.
• Analysis of total mercury (Hg) and methyl mercury (MMHg) concentrations using established analytical techniques.
• Determination of organic carbon (OC) content in the sediment samples.

Main Results:

• Total Hg concentrations ranged from 10 to 56 ng g(-1) d.w., and MMHg from 0.1 to 0.4 ng g(-1) d.w.
• Methyl mercury (MMHg) constituted 0.3% to 1.1% of the total mercury (Hg).
• Organic carbon (OC) content varied between 0.4% and 1.8%.
• Hg and MMHg levels were found to be significantly correlated.
• Higher concentrations of total Hg, MMHg, and OC were observed at deeper stations.
• Sediment mercury levels were below the threshold for polluted areas (<100 ng g(-1)).

Conclusions:

• The Iranian coastal waters of the Persian Gulf are generally unpolluted with respect to mercury in marine sediments.
• Deeper marine environments in the study area tend to accumulate higher levels of mercury and organic matter.
• While total mercury and methyl mercury are linked, organic carbon content does not show a significant correlation with mercury levels in these sediments.