Trace ele
ments (Ag, Cd, Co, Cr, Cu, Fe, Mn, Pb, V, Zn) and a
mmonia were
measured in pore waters extracted fro
m sedi
ments collected in Green Sands Beach (Mare Island, San Francisco, CA) using peepers and whole-core squeezers. Sa
mples were size-fractionated, either by using 0.45 and 0.1 μ
m polycarbonate filters (whole-core squeezers), or by passive filtration using peepers with 0.45 μ
m and 3000 MWCO (3 kDa)
me
mbranes. Results indicate that the distribution profiles of pore water constituents in the traditionally defined total dissolved fraction (
CTD = <0.45 μ
m) reflect different diagenetic processes, as well as anthropogenic inputs fro
m the for
mer Mare Island Naval Shipyard. Metal concentrations and profiles in the truly dissolved phase (
CD = <3 kDa) for Mn, Co, Cr, V and
me="mml5">method=retrieve&_udi=B6VDG-4P7R869-2&_mathId=mml5&_user=10&_cdi=5982&_rdoc=16&_acct=C000050221&_version=1&_userid=10&md5=d9de749f1e24b967a0a1056d4cdd5acf">mg src="http://www.sciencedirect.com/cache/MiamiImageURL/B6VDG-4P7R869-2-Y/0?wchp=dGLbVzb-zSkWz" alt="Click to view the MathML source" align="absbottom" border="0" height=19 width=36> were si
milar to the ones obtained for
CTD. Profiles for the s
mall-sized dissolved fraction (
CSSD = <0.1 μ
m) and in the
CTD pool were al
most identical for all of the analysed
metals. Absolute values of the ratios between the diffusive fluxes of the different size fractions relative to the total dissolved fluxes ranged fro
m 0.012 to 41. Of these, 37%were lower than 0.50 and 12%showed values in excess of 2.0. However, in 22%of the cases, the fluxes were in directions opposite to the
metal fluxes calculated using
CTD gradients. Hence, gradients of total dissolved trace
metals, which are the only ones nor
mally
measured in pore waters,
may not necessarily reflect the
mass flow of dissolved constituents across the sedi
ment colu
mn.