# GETCO2: A Compact and Portable System for Automated Gas Transfer Velocity Measurements of Natural Waters

## TL;DR

The paper introduces GETCO2, a compact and portable system for measuring CO2 gas transfer in natural waters, improving accuracy and portability over previous models.

## Contribution

The novel GETCO2 system integrates a cost-effective NDIR CO2 sensor and an automated equilibrator for precise gas transfer velocity measurements.

## Key findings

- Measurement errors for equilibrated CO2 in air and water are 1.3% and 3.4%, respectively.
- GETCO2 achieves k_w precision of 7.21 ± 0.18 cm h–1 with a 2.5% coefficient of variation.
- The system's k_w suppression levels match those of previous automated gas exchange tanks.

## Abstract

To enhance our understanding of surfactants in the exchange
of
climatically active gases across the water–atmosphere interface,
we introduce a novel CO2 gas exchange tank equipped with
a gas transfer velocity (k
w) estimation
tool, significantly improving upon earlier designs. This advanced
platform integrates a commercially available, cost-effective, high-performance
nondispersive infrared (NDIR) CO2 sensor with a closed
controlled environment gas exchange tank. The tank is designed to
induce precisely controlled water-side turbulence, allowing for the
exploration of biological and chemical factors controlling the k
w. The new system features a bespoke 3D-printed
automated equilibrator, enabling precise measurements of the water
CO2 concentration. CO2 concentrations in both
air and water phases are measured using a novel setup that minimizes
errors from sensor drift and incomplete mixing or equilibration. Measurement
errors for equilibrated CO2 concentrations in air and water
are 1.3 and 3.4%, respectively. The precision achieves k
w values of 7.21 ± 0.18 cm h–1 with
a coefficient of variation (CV) of 2.5% for deionized water. Testing
with freshwater and marine waters yielded k
w suppression levels comparable to an earlier automated gas exchange
tank system utilizing gas chromatography. This next-generation GETCO2
system is smaller, easier to maintain, and more portable than previous
models, allowing for wider-scale studies aimed at investigating the
impact of surfactants and other organic compounds on k
w suppression and enhancement across various natural water
environments.