# Biogenic Volatile Organic Compounds from Pennsylvanian Lakes Sampled during the 2024 Algal Bloom Season

## TL;DR

This study measures biogenic volatile organic compounds from freshwater lakes during algal blooms, revealing new insights into their atmospheric impact.

## Contribution

The first real-time freshwater flux measurements of alkylamines, pyrroline, and pyridine during algal blooms.

## Key findings

- Ammonia, pyrroline, and pyridine showed the highest emission fluxes across lake samples.
- No clear correlation was found between BVOC fluxes and cyanobacterial indicators like chlorophyll a.
- Two outlier samples showed elevated ammonia and an unknown compound, suggesting unexplored factors influence emissions.

## Abstract

Biogenic volatile
organic compounds (BVOCs) emitted from
aquatic
systems are increasingly recognized for their influence on atmospheric
chemistry. However, emissions from freshwater environments, specifically
during harmful algal bloom (HAB) events, remain poorly quantified.
These HAB events are increasing globally in frequency and intensity,
driven by climate change, nutrient runoff, and land-use changes. This
study investigates the water-to-air gas exchange rates of BVOCs from
southwestern Pennsylvanian freshwater lakes during peak HAB conditions,
with a focus on nitrogen-containing compounds that are typically underrepresented
in atmospheric measurements. Using atmospheric pressure, hydronium
chemical ionization mass spectrometry (CIMS), we measured BVOC emissions
from 18 lake samples in the laboratory, capturing real-time fluxes
of 900 unique masses. Ammonia, pyrroline, and pyridine consistently
exhibited the highest emission fluxes across samples. Alkylamines
were less abundant, although they remain atmospherically important
due to their role in new particle formation. These results represent
the first reported real-time freshwater flux measurements of alkylamines,
pyrroline, and pyridine, offering new insight into the atmospheric
implications of HABs. Notably, no clear correlation was observed between
BVOC fluxes and chlorophyll a and phycocyanin concentrations,
which were taken to represent the cyanobacterial concentrations in
the samples. This suggests that emissions are influenced by other
biological or chemical factors not captured in this study. Principal
component analysis identified two significant outlier water samples,
driven by elevated ammonia, pyrroline, and an unknown compound at
124.101 amu, though the underlying cause of these deviations remains
unresolved. The remaining lake emissions were similar. These findings
provide foundational observations to better understand the role of
freshwater system emissions in regional air quality and atmospheric
processes.