In situ determination of dissolved organic carbon in freshwaters using a reagentless UV sensor.
Reliable, high temporal and spatial resolution data are essential for enhancing our understanding of aquatic dissolved organic carbon (DOC) biogeochemical cycling. This paper describes a novel UV spectrophotometric sensor for the real time, in situ, high resolution (every 30 s) mapping of DOC in freshwaters. The sensor incorporates high resolution, multi-wavelength spectral acquisition (256 channel photodiode array) and a hybrid linear analysis (HLA) curve fitting algorithm. The portable and reagentless in situ UV sensor has a good linear range (0.5-15 mg C L(-1)) and precision (mean RSD 8.5%, n = 7 standards each measured 5 times) and quantitative recoveries were obtained for spiked river water (93.8 +/- 6.2%, n = 35). The DOC field data were in good agreement with results from a laboratory high temperature combustion method (t test (p = 0.05) gave P = 0.20 (n = 14), 0.89 (n = 21) and 0.92 (n = 15) for three separate freshwater deployments). These data suggested that solar radiation, coupled with microbial uptake and release, together with the physico-chemical parameters of hydrological flow, temperature and pH were significant drivers of DOC cycling in this ecosystem. Real time data processing provided an immediate data stream for mapping diurnal and/or seasonal DOC cycling. This capability will enhance our understanding of DOC sources, delivery mechanisms and internal cycling and support sustainable catchment management.
Sandford
Richard Charles
RC
Biogeochemistry and Environmental Analytical Chemistry (BEACh) Group, School of Geography, Earth, and Environmental Sciences, University of Plymouth, Plymouth, PL4 8AA, England, UK. rsandford@plymouth.ac.uk
Bol
Roland
R
Worsfold
Paul John
PJ
D002244:Carbon / Q000032:analysis* / Q000737:chemistry; D057486:Carbon Cycle; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry*; D010783:Photometry; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
D014874:Water Pollutants, Chemical; D002244:Carbon