Physical and Geochemical Transports Along the Ancona Coastal Area
11
pies for the determination of nutrients (silicate.
phosphate. nitrate, nitrite and ammonium) were
collected directly from the Niskin bottle, filtered
throughout 0.7 pm GFF filter and stored at -30
DC in 100 ml LDPE (low density poly-ethylene)
containers, until analysis. Water samples for the
determination of suspended matter were filtered
through prewashed 47 mm diameter Millipore
(cellulose acetate-nitrate) filters having a nominal diameter of 0.45 p.m and stored in petri dishes at -30
D
C.
Continuous current measurements were
acquired using three moored instruments located in two different positions (A and B. Fig. I).
The coastal mooring (12 m depth) was equipped
with one current meter at the nominal depth of
5 m; the offshore mooring was located at 40 m
depth with two instruments at the nominal
depth of 5 m and 18 m. All instruments recorded hourly average data during the summer period while only the hourly averaged time series of
the coastal mooring is available for the winter
season. High frequencies (tidal and inertial
oscillations) were filtered applying a low-pass
numerical filter to the hourly averaged current
data.
Samples Analysis
Measurements of nutrients were performed by
an Autoanalyzer Techicon II, according to the
Hansen and Gras shoff methods (1983).
Estimated detection limits for nitrate, nitrite,
ammonium, phosphate and silicate were 0.05,
0.01, 0.05, 0.05, 0.1 pM. respectively.
Total particulate matter (TPM) was determined by weight change of the sample filter after
drying over silica gel. To correct for weight
changes induced by humidity reference filters
from the same lot were used. Combustible organic matter was determined by ashing the filter at
lOOOGC in preweighted porcelain crucibles; the
increase in weight of the crucible is reported as
inorganic particulate matter (IPM) and the difference between TPM and IPM was reported as
organic particulate matter (OPM) (Strickland
and Parsons 1968).
Dimensional analysis was performed immediately after collection with a Coulter Counter
Multisizer II using a 140 p.m tube (Krank 1980).
Particle sizes were separated in 256 channels in a
range between 0.6-65 pm.
Transport Estimations
Using the hydrological and low-pass filtered current meter data the longshore transports were
calculated.
Transport values were obtained on the basis
of the classical geostrophic method imposing the
zero reference level, on first step, at the depth of 5
m. In such a shallow area, it is well known that the
geostrophic method has obvious limitation
because the friction with the bottom can not be
considered negligible. This evident restriction is
not dramatic when the barotropic component of
the motion is prevailing. with respect to the baroclinic one, and it is available from direct measurements. For this purpose the baroclinic fields
were adjusted using the low-pass filtered current
meter time series recorded close to the coast and
more offshore (Fig. I), both at the depth of 5 m.
Daily averaged data were used to calculate the
current f:tled with the geostrophic method.
The summer evaluations were made using
the data recorded by the two surface current
meters and linearly interpolated to get the reference speed for each couple of stations. Because of
the lack of current data, the winter evaluations
were obtained using only the information coming from the coastal current meter close to
Senigallia. This approximation did not affect our
estimation since in winter the coastal flow, as discussed in the next section, is confmed in a smaller area and therefore it was well monitored by
the coastal instrument.
In order to evaluate the fresh water concentration this simple relationship was applied:
S-S
c=-5
where 5 is the salinity of the local MLIW (5 =
38.4 in our computations) and S the salinity of
the in situ data.
The calculated fresh water, the velocity data
and the measured geochemical concentrations
were interpolated on a regular grid by using the
kriging method with 1 km horizontal and 2 m
vertical resolution. In order to normalize the
data an anisotropic ratio of 500 was imposed
during the gridding procedures. The transport
matrix was obtained by multiplying two by two
the corresponding elements of concentration
and corresponding velocity matrices. By integrating over all the section we got the total transport for each transect.
11
pies for the determination of nutrients (silicate.
phosphate. nitrate, nitrite and ammonium) were
collected directly from the Niskin bottle, filtered
throughout 0.7 pm GFF filter and stored at -30
DC in 100 ml LDPE (low density poly-ethylene)
containers, until analysis. Water samples for the
determination of suspended matter were filtered
through prewashed 47 mm diameter Millipore
(cellulose acetate-nitrate) filters having a nominal diameter of 0.45 p.m and stored in petri dishes at -30
D
C.
Continuous current measurements were
acquired using three moored instruments located in two different positions (A and B. Fig. I).
The coastal mooring (12 m depth) was equipped
with one current meter at the nominal depth of
5 m; the offshore mooring was located at 40 m
depth with two instruments at the nominal
depth of 5 m and 18 m. All instruments recorded hourly average data during the summer period while only the hourly averaged time series of
the coastal mooring is available for the winter
season. High frequencies (tidal and inertial
oscillations) were filtered applying a low-pass
numerical filter to the hourly averaged current
data.
Samples Analysis
Measurements of nutrients were performed by
an Autoanalyzer Techicon II, according to the
Hansen and Gras shoff methods (1983).
Estimated detection limits for nitrate, nitrite,
ammonium, phosphate and silicate were 0.05,
0.01, 0.05, 0.05, 0.1 pM. respectively.
Total particulate matter (TPM) was determined by weight change of the sample filter after
drying over silica gel. To correct for weight
changes induced by humidity reference filters
from the same lot were used. Combustible organic matter was determined by ashing the filter at
lOOOGC in preweighted porcelain crucibles; the
increase in weight of the crucible is reported as
inorganic particulate matter (IPM) and the difference between TPM and IPM was reported as
organic particulate matter (OPM) (Strickland
and Parsons 1968).
Dimensional analysis was performed immediately after collection with a Coulter Counter
Multisizer II using a 140 p.m tube (Krank 1980).
Particle sizes were separated in 256 channels in a
range between 0.6-65 pm.
Transport Estimations
Using the hydrological and low-pass filtered current meter data the longshore transports were
calculated.
Transport values were obtained on the basis
of the classical geostrophic method imposing the
zero reference level, on first step, at the depth of 5
m. In such a shallow area, it is well known that the
geostrophic method has obvious limitation
because the friction with the bottom can not be
considered negligible. This evident restriction is
not dramatic when the barotropic component of
the motion is prevailing. with respect to the baroclinic one, and it is available from direct measurements. For this purpose the baroclinic fields
were adjusted using the low-pass filtered current
meter time series recorded close to the coast and
more offshore (Fig. I), both at the depth of 5 m.
Daily averaged data were used to calculate the
current f:tled with the geostrophic method.
The summer evaluations were made using
the data recorded by the two surface current
meters and linearly interpolated to get the reference speed for each couple of stations. Because of
the lack of current data, the winter evaluations
were obtained using only the information coming from the coastal current meter close to
Senigallia. This approximation did not affect our
estimation since in winter the coastal flow, as discussed in the next section, is confmed in a smaller area and therefore it was well monitored by
the coastal instrument.
In order to evaluate the fresh water concentration this simple relationship was applied:
S-S
c=-5
where 5 is the salinity of the local MLIW (5 =
38.4 in our computations) and S the salinity of
the in situ data.
The calculated fresh water, the velocity data
and the measured geochemical concentrations
were interpolated on a regular grid by using the
kriging method with 1 km horizontal and 2 m
vertical resolution. In order to normalize the
data an anisotropic ratio of 500 was imposed
during the gridding procedures. The transport
matrix was obtained by multiplying two by two
the corresponding elements of concentration
and corresponding velocity matrices. By integrating over all the section we got the total transport for each transect.