Fractionation and concentration of suspended particulate matter in natural waters

Abstract

A scheme for the fractionation and concentration of suspended particulate matter (SPM) from natural waters has been tested. This scheme involves the sequential use of three fractionation techniques-sieving, continuous flow centrifugation and tangential flow filtration to collect gram amounts of SPM over the entire particulate and colloidal size range. The separation scheme is able to process large samples (ca. 100 l), within reasonable times (ca. 1 day) and the apparatus is portable. Reproducibility and potential artifacts introducing during the fractionation and concentration of SPM, particularly when tangential flow filtration is used, are discussed. It has been shown that there is a systematic increase in the content of organic carbon, Mg, Ca, Na, K, Cu and Zn with decreasing particle size, highlighting the importance of the colloidal ( < 1 pm) fraction.

The role of coarse colloids as a carrier phase for trace metals in riverine systems

“…Apart from practical considerations (Horowitz et al, 1996;Shiller and Taylor, 1996), there is an acceptance on theoretical grounds that coarse colloids are likely to contribute only marginally to metal sorption; since the metal complexation capacity of environmental particles is inversely related to their size (Buffle, 1988). Douglas et al (1993) and Douglas et al (1999) report decreasing concentrations of particle bound Cu and Zn with increasing particle size (range 0.003 -> 25 µm), in agreement with theoretical expectations. However, the averaged metal concentration over the total suspended particulate matter (range 0.003 -1000 µm) is comparable to that measured in the 0.2 -1 µm fraction, suggesting that this fraction may be of pre-eminent importance in controlling the transport of Cu and Zn under field conditions.…”

“…Laxen and Harrison (1981) (Douglas et al, 1993;Ran et al, 2000) report over 50 % of Al, Cu, Mn, Fe, Ti, and Zn associated with colloidal material in the range 0.2 -1 µm. Although caution is mandatory when comparing data obtained with different methodologies, the association of trace elements with coarse colloids is clearly a widespread phenomenon.…”

“…rivers (Morrison and Benoit, 2001) or 0.2 -1 µm for some Australian rivers (Douglas et al, 1993;. In this study, we will show that coarse colloids, which are retained on 0.45 µm filters and thus usually included in the particulate fraction, may act as an important carrier for several trace metals in rivers.…”

Export of dissolved and undissolved nutrients from forested catchments in Peninsular Malaysia

“…Apparently, these SPM concentrations are too low compared to average suspended solids (SS) concentrations of 68.3 mg l À1 during storms and 4 mg l À1 Table 6 Nutrient export via stream litter from November 1993 to May 1994 and the projected annual export (in parentheses) in catchments C1 and C2 Load (kg ha À1 ) N (g ha À1 ) P (g ha À1 ) K (g ha À1 ) C a( gh a À1 ) M g( gh a À1 ) N a( gh a À1 ) during low flow conditions (Baharuddin Kasran, unpublished data). The most likely reason for this discrepancy is that the continuous centrifugation technique only fractionates particulates in the size range between 1 and 25 mm (Douglas et al, 1991) compared to typical filtration methods for determining SS that retain all particles greater than 0.45 mm. These low SPM values resulted in very low nutrient export via this mode, generally less than 5% of the dissolved export except for Ca (12%) and Mg (16.7%) (Table 10).…”

Partition of copper between dissolved and particulate phases using aluminum oxide as an aquatic model phase: effects of pH, solids and organic matter

“…Because of that a fairly large sample volume of water needs to be processed to obtain enough suspended solids to perform adsorption or desorption experiments. Methods for SPM concentration from natural waters include settling, centrifugation, flocculation, membrane filtration, reverse osmosis, and hollow fiber ultrafiltration 19 . All of these suffer from many shortcomings in handling colloidal materials.…”