Low mercury risks in paddy soils across the Pakistan

Area of Science:

• Environmental Science
• Geochemistry
• Pollution Studies

Background:

• Mercury (Hg) is a global pollutant. Understanding its sources and levels in Pakistan's paddy soils is crucial for assessing environmental risk.
• Previous assumptions suggested high Hg pollution in Pakistan, necessitating detailed investigation.

Purpose of the Study:

• To determine mercury (Hg) concentration and isotopic composition in Pakistan's paddy soils.
• To identify the primary sources of Hg contamination in these agricultural areas.

Main Methods:

• Analyzed total Hg (THg) concentrations in 500 paddy soil samples across Pakistan.
• Utilized Hg stable isotope analysis (δ²⁰²Hg, Δ¹⁹⁹Hg, Δ²⁰⁰Hg) to differentiate Hg sources.
• Correlated Hg levels with soil physicochemical properties and proximity to industrial/brick kiln sites.

Main Results:

• Average THg concentration was 22.30 ± 21.74 ng/g, indicating lower overall pollution than expected.
• Higher THg levels were found near brick kilns and industrial zones, pointing to localized point sources.
• Isotope analysis suggested coal combustion from local anthropogenic sources at contaminated sites.
• Uncontaminated sites indicated long-range transboundary transport via wet Hg(II) deposition as a dominant source.

Conclusions:

• Hg pollution in Pakistan's paddy soils is generally low.
• Local anthropogenic activities like coal combustion and industrial emissions are significant sources in specific areas.
• Long-range atmospheric transport also contributes to Hg deposition in uncontaminated regions.