Chloroform in the environment: occurrence, sources, sinks and effects

Area of Science:

• Environmental Chemistry
• Atmospheric Science
• Ecotoxicology

Background:

• Chloroform (CHCl3) is a volatile organic compound with both natural and anthropogenic sources.
• Understanding its environmental flux and fate is crucial for assessing ecological and atmospheric impacts.

Purpose of the Study:

• To quantify chloroform emissions from various environmental sources.
• To determine chloroform's atmospheric concentration, distribution, and removal processes.
• To evaluate the ecotoxicological risks and atmospheric effects of chloroform.

Main Methods:

• Quantification of chloroform flux from oceanic and terrestrial sources.
• Atmospheric modeling to determine distribution and concentration.
• Assessment of environmental partitioning and degradation pathways.

Main Results:

• Total environmental chloroform flux is approximately 660+/-220 Gg/yr, with 90% from natural origins (offshore seawater and soil processes).
• Anthropogenic sources contribute 66+/-23 Gg/yr, mainly from industrial oxidation of organic matter.
• Chloroform predominantly partitions to the atmosphere (>99%), with an average concentration of 18.5 pmol/mol; atmospheric oxidation balances emissions.
• No significant ecotoxicological risk was found, even for sensitive aquatic life stages.
• Chloroform does not materially deplete ozone or act as a photochemically active VOC, with a low global warming potential.

Conclusions:

• Natural processes dominate chloroform emissions, with significant contributions from marine and soil environments.
• Current environmental concentrations of chloroform do not pose a substantial risk to ecosystems or human health.
• Chloroform's limited stratospheric transport and low photochemical reactivity mean it has negligible impact on ozone depletion and climate change.