Development of observation and analytical techniques to quantify the speciation of trace nutrients.

Primary productivity of continental and marine ecosystems is often limited or co-limited by phosphorus. The atmosphere is considered a principal source of externally-supplied nutrients for large areas of the surface ocean, and oligotrophic open oceans. Atmospheric inorganic P species (e.g. mono- or diprotonated orthophosphate) comprise the most bioavailable P form, and have been studied for many decades. Inorganic P are currently studied using filter samples with poor temporal resolution (1 sample/day or longer) and potentially significant sampling artifacts. To address the above limitation, we have developed an automated online system that measures P in atmospheric particles spectrophotometrically, using the molybdenum blue complex method (Violaki et al., 2016). The system consists of a Particle-In-Liquid sampler coupled with a reaction coil and a liquid capillary waveguide detection cell.

This novel technique offers at least an order of magnitude enhancement in sensitivity over existing approaches allowing for SRP measurements of unprecedented frequency (6-8 min), leading to greater understanding of the sources and impacts of SRP in atmospheric chemistry. The detection limit was 0.4 nM P, equivalent to 0.03 nmol P m−3 in atmospheric particles.

a) Online PILS-LWCC system in the lab b) Schematic diagram of PILS-LWCC for online measurements of SRP. The two 2-position valves were synchronized with an Arduino microprocessor module. Data acquisition was recorded by the software Spectra Suite (Ocean Optics).
Typical detector signal obtained during calibration by using the LWCC of 2.5m path length. The working standards are in the range 6.1−97.1 nM P. Error bars based on standard deviation are included (n = 3).


Kalliopi Violaki, Ting Fang, Nikos Mihalopoulos, Rodney. Weber, Athanasios Nenes, A real-time, online automated system for measurement of water soluble reactive Phosphate (SRP) ions in atmospheric particles, Anal. Chem., 88 (14), pp 7163–7170, 2016. DOI: 10.1021/acs.analchem.6b01264