TY - JOUR
T1 - Development and application of functional assays for freshwater dissolved organic matter
AU - Thacker, SA
AU - Tipping, E
AU - Baker, Andrew
AU - Gondar, D
PY - 2005/11/1
Y1 - 2005/11/1
N2 - A series of 11 standardised, reproducible, assays have been developed of physico-chemical functions of dissolved organic matter (DOM) in freshwaters. The assays provide quantitative information on light absorption, fluorescence, photochemical fading, pH buffering, copper binding, benzo(a)pyrene binding, hydrophilicity and adsorption to alumina. To obtain DOM for the assays, a 45 L sample of filtered freshwater was rotary-evaporated to reduce the volume to ca. 500 cm(3). The concentrate was then passed through a strong cation exchanger, in the Na+ form, to remove alkaline-earth cations, and then through 0.7 and 0.2 pm filters. Eight samples, two each from a lake and three streamwaters, were processed. The yields of dissolved organic carbon (DOC) ranged from 70% to 107% (average 91%). The samples of DOM, stored in the dark at 4 degrees C, retained their functional assay characteristics for up to 7 months. When assaying the concentrates, parallel assays were performed with Suwannee River fulvic acid (SRFA), as a quality control standard. For most of the assays, the results for eight freshwater DOM samples are similar to those obtained with SRFA, the chief exception being the greater hydrophilicity of the DOM samples. For eight of the assays, variability among the DOM samples is significantly (p <0.01) greater than can be explained by analytical error, i.e. by comparison with results for the SRFA quality standard; the three exceptional assays are photochemical fading, copper binding and benzo(a)pyrene binding. The two lakewater samples studied gave the most extreme assay results, probably because of the influence of phytoplankton-derived DOM. Significant correlations of hydrophilicity and adsorption with optical absorbance may mean that some DOM functional properties can be predicted from comparatively simple measurements. (c) 2005 Elsevier Ltd. All rights reserved.
AB - A series of 11 standardised, reproducible, assays have been developed of physico-chemical functions of dissolved organic matter (DOM) in freshwaters. The assays provide quantitative information on light absorption, fluorescence, photochemical fading, pH buffering, copper binding, benzo(a)pyrene binding, hydrophilicity and adsorption to alumina. To obtain DOM for the assays, a 45 L sample of filtered freshwater was rotary-evaporated to reduce the volume to ca. 500 cm(3). The concentrate was then passed through a strong cation exchanger, in the Na+ form, to remove alkaline-earth cations, and then through 0.7 and 0.2 pm filters. Eight samples, two each from a lake and three streamwaters, were processed. The yields of dissolved organic carbon (DOC) ranged from 70% to 107% (average 91%). The samples of DOM, stored in the dark at 4 degrees C, retained their functional assay characteristics for up to 7 months. When assaying the concentrates, parallel assays were performed with Suwannee River fulvic acid (SRFA), as a quality control standard. For most of the assays, the results for eight freshwater DOM samples are similar to those obtained with SRFA, the chief exception being the greater hydrophilicity of the DOM samples. For eight of the assays, variability among the DOM samples is significantly (p <0.01) greater than can be explained by analytical error, i.e. by comparison with results for the SRFA quality standard; the three exceptional assays are photochemical fading, copper binding and benzo(a)pyrene binding. The two lakewater samples studied gave the most extreme assay results, probably because of the influence of phytoplankton-derived DOM. Significant correlations of hydrophilicity and adsorption with optical absorbance may mean that some DOM functional properties can be predicted from comparatively simple measurements. (c) 2005 Elsevier Ltd. All rights reserved.
KW - humic substances
KW - dissolved organic matter
KW - dissolved organic carbon
KW - assays
KW - natural waters
KW - characterisation
UR - http://www.scopus.com/inward/record.url?scp=27544443269&partnerID=8YFLogxK
U2 - 10.1016/j.watres.2005.08.020
DO - 10.1016/j.watres.2005.08.020
M3 - Article
C2 - 16214200
SN - 1879-2448
VL - 39
SP - 4559
EP - 4573
JO - Water Research
JF - Water Research
IS - 18
ER -