Fingerprinting localized dioxin contamination: Ichihara Anchorage case.

Area of Science:

• Environmental Chemistry
• Marine Pollution
• Chemical Forensics

Background:

• Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) levels in Japanese sediments have generally decreased below environmental standards.
• Localized, high-concentration dioxin contamination persists in areas like Ichihara Anchorage, Tokyo Bay, exceeding standards by up to 100-fold.

Purpose of the Study:

• To identify the source and distribution of localized dioxin contamination in Ichihara Anchorage surface sediments.
• To quantitatively fingerprint the congener patterns and geographical spread of the contaminating factor.

Main Methods:

• Analysis of mono- to octachlorinated dioxins in 12 surface sediment samples from Ichihara Anchorage.
• Application of Positive Matrix Factorization (PMF) to fingerprint dioxin sources and their distribution.

Main Results:

• A PMF-derived fingerprint linked to dioxin impurities in pentachlorophenol (PCP) accounted for over 90% of total dioxins in Ichihara Anchorage sediments.
• While most PCP-derived dioxins remained localized, their contribution increased towards Ichihara Anchorage within Tokyo Bay, indicating broader impact.

Conclusions:

• Ichihara Anchorage is a significant source of PCP-derived dioxins, particularly in eastern Tokyo Bay.
• Runoff from rice paddies treated with PCP historically may also contribute to dioxin contamination in the region.