Articles | Volume 22, issue 11
Research article
30 Oct 2018
Research article |  | 30 Oct 2018

A small-volume multiplexed pumping system for automated, high-frequency water chemistry measurements in volume-limited applications

Bryan M. Maxwell, François Birgand, Brad Smith, and Kyle Aveni-Deforge

Abstract. An automated multiplexed pumping system (MPS) for high-frequency water chemistry measurements at multiple locations previously showed the ability to increase spatial and temporal data resolution and improve understanding of biogeochemical processes in aquatic environments and at the land–water interface. The design of the previous system precludes its use in volume-limited applications in which highly frequent measurements requiring a large sample volume would significantly affect observed processes. A small-volume MPS was designed to minimize the sample volume while still providing high-frequency data. The system was tested for cross-contamination between multiple sources, and two applications of the technology are reported. Cross-contamination from multiple sources was shown to be negligible when using recommended procedures. Short-circuiting of flow in a bioreactor was directly observed using high-frequency porewater sampling in a well network, and the small-volume MPS showed high seasonal and spatial variability of nitrate removal in stream sediments, enhancing data collected from in situ mesocosms. The results show it is possible to obtain high-frequency data in volume-limited applications. The technology is most promising at the reach or transect scale for observing porewater solute dynamics over daily timescales, with data intervals  < 1 h for up to 12 locations.

Short summary
A multiplexed pumping system (MPS) for obtaining continuous water quality data at multiple locations was previously reported. The existing design was not practical for sampling water in volume-limited applications such as small mesocosms or porewater sampling. This paper discusses the design and performance of a small-volume MPS and illustrates two applications, showing spatial variability in replicate in situ mesocosms and short-circuiting in a woodchip bioreactor using porewater sampling.