# Real-Time Measurements of Gas-Phase Medium-Chain Chlorinated Paraffins Reveal Daily Changes in Gas-Particle Partitioning Controlled by Ambient Temperature

## TL;DR

The study measures gas-phase medium-chain chlorinated paraffins in real time, revealing how temperature affects their gas-particle partitioning and environmental behavior.

## Contribution

The paper introduces real-time in situ measurements of 18 gas-phase MCCPs using NO3–CIMS, providing new insights into their environmental dynamics.

## Key findings

- Real-time measurements of 18 gas-phase MCCPs were conducted using NO3–CIMS in the Southern Great Plains.
- MCCP concentrations averaged single-digit ng/m3, with diel behavior influenced by gas-particle partitioning.
- Ambient temperature controls daily changes in MCCP gas-particle partitioning, affecting transport and lifetimes.

## Abstract

Chlorinated paraffins (CPs) are synthetic polychlorinated n-alkanes produced as mixtures of a range of C
x
Cl
y
H2x–y+2 formulas. CPs have numerous industrial
applications but are toxic, long-lived, and environmentally ubiquitous
with environmental releases occurring throughout their production,
use, and disposal. Short-chain chlorinated paraffins (SCCPs, C10–13) have been regulated by the United States Environmental
Protection Agency since 2009 and by the Stockholm Convention since
2017. SCCP regulation is expected to cause increased production of
medium-chain chlorinated paraffins (MCCPs; C14–17), which are currently under consideration for Stockholm Convention
regulations. Thus, there is a need to improve the understanding of
MCCP environmental transport, distribution, and fate. Existing measurements
are limited in their spatial and temporal coverage. Measurements of
CP atmospheric loading are particularly scarce. Historically, these
measurements have required long sampling times, obscuring the temporal
behavior of atmospheric CPs. We report real-time in situ measurements of 18 gas-phase MCCPs. These measurements were made
in the United States Southern Great Plains with nitrate ion chemical
ionization mass spectrometry (NO3–CIMS). The estimated
average lower-limit concentration of MCCPs is on the order of single-digit
ng/m3. MCCP diel behavior is partially explained by gas-particle
partitioning with implications for MCCP transport and lifetimes.