Particulate matter in seawater
Particulate matter in seawater
Source: Plymouth Marine Laboratory and ICES (2004)
Introduction
This procedure addresses determination of Total Suspended Solids (TSS; which is also known as Suspended Particulate Matter; SPM = total particulate matter, TPM), Particulate Inorganic Matter (PIM) and Particulate Organic Matter (POM).
The particle size of organically bound carbon of particles (POC) generally ranges between 0.45 µm and 300 µm. This includes both living organisms, such as phytoplankton, yeasts, bacteria, and microzooplankton, and detrital particles and aggregates. The production and decomposition of biogenic particles as well as their fractional removal to the deep sea control the distribution of most trace elements in the oceans. Microbial decomposition, desorption, and dissolution of suspended or sinking marine particles can release elements associated with labile (e.g., organic) fractions back to the sea water. On the other hand, particles can scavenge trace elements from the dissolved phase and thereby transport them to sediments. Analysis of the composition and distribution of the particulate fractions in the oceans is therefore required to understand the behaviour and geochemical cycling of both major and trace elements.
Required
pre-washed, ashed and weighed GF/F 47mm filters, prepared as below, stored in clean petri plates
clean forceps
100% acetone in wash bottle for washing off all surfaces that come in contact with filters
Freshly distilled water in wash bottle
Filtration manifold with filter holders for 47mm filters
0.5M Ammonium formate (31.5 g/l)
Dessicator
Drying oven
Muffle furnace
Concentrated HCl in Erlenmeyer or beaker for acid-fuming filters
Long (>20cm) forceps for holding filter over acid fumes
Fume hood for acid-fuming process
50mm (diameter) Petri plates
Filter-preparation:
a. To remove fine loose particles of filter, separate and soak in distilled water for > 1h; agitate and rinse 3-4 times in distilled water.
b. Partially dry each filter on suction head to remove excess water (this prevents sticking to foil in the next step).
c. Place filters individually into foil envelope/fan and oven dry overnight.
d. Carefully number each filter on the exposed margin (soft lead pencil or pre-tested pen) and lay out (slightly overlapping) on foil tray, fit a lid and ash in muffle furnace at 450°C for >4h.
e. Cool in dessicator; all handling of filters, from this point on, using clean (acetone) forceps only to avoid contamination.
f. Remove individually and weigh to 5 places, standardising the time it takes to weigh (filters increase in weight as they take up atmopheric moisture), and store place in numbered petri-slides.
Particulate Organic Matter and Total Particulate Matter determination :
a. Filter the required volume of homogenised material (see below)
b. Rinse filter twice with 10 ml of 0.5M Ammonium formate solution to remove salt and then rinse with distilled water around margin of the filtration cup, having removed filter head (do all of the above with pump running), and when dry, return filter to petrislide.
c. Oven dry filters (60°C for 2 days, 40°C for 1 week) and store in dessicator.
d. Weigh (from dessicator, to 5 places, as above, preferably with the same balance) for total particulate matter (TPM).
e. Ash at 450°C in muffle furnace for > 4h
f. Weigh (from dessicator to 5 places, as above, preferably with the same balance) for inorganic particulates (PIM).
g. Do all of the above using at least 10 blank filters (prepared and processed as above, but without sample) for each experimental day (changes in weight before and after experimentation are used to correct for changes in balance calibration and/or filter water content).
Absolute care in the preparation and processing of these filters as described is essential, for small errors in weight at these stages will significantly bias ratios and other results calculated later. Many experiments have been ruined by lack of attention to the above details!
Reference
ICES. 2004. Chemical measurements in the Baltic Sea: Guidelines on quality assurance. Ed. E. Lysiak-Pastuszak and M. Krysell. ICES Techniques in Marine Environmental Sciences, No. 35. 149 pp.
