scispace - formally typeset

Book ChapterDOI

A cadmium budget for the Lot-Garonne fluvial system (France)

01 Sep 1999-Hydrobiologia (Springer, Dordrecht)-Vol. 410, pp 331-341

AbstractRoutine measurements of river discharge and total suspended sediment concentration (TSS) are combined with regular analyses for particulate and dissolved cadmium to produce a box model that allows us to propose a cadmium mass balance for the Lot-Garonne man-influenced river system (8400 km2). Nearly half the cadmium in the Garonne river is supplied by the tributary Lot river. Cadmium input onto the Lot river comprises wet deposition from the atmosphere, molecular diffusion at the sediment-water interface, surface-water runoff and discharge from the leaching of waste at a zinc refining plant. Approximately 85% of the cadmium in the Lot river is derived from anthropogenic origin. Cadmium in the industrial discharge is 80% dissolved and 20% in the particulate phase (4.2 and 1.1 t yr−1, respectively). Total inputs are estimated at 4.81 t yr−1 and 1.54 t yr−1 for the dissolved cadmium and for the particulate phase, respectively. Budgeting estimates an output onto the Garonne river of 0.54 t yr−1 for the dissolved cadmium (about 8%) and 6.13 t yr−1 for the particulate cadmium (about 92%) indicating that downstream sediment-associated cadmium fluxes are enhanced by the 4.27 t yr−1 removed from solution and the 0.32 t yr−1 remobilized by the erosion of sediment blanketing the Lot river bed. These figures are found to be comparable with those generated by a dilution model which suggests that 97% of dissolved cadmium is taken up by the particulate phase over 0.5 km downstream from the primary anthropogenic source.

Topics: Cadmium (60%), Tributary (55%)

Summary (2 min read)

Introduction

  • The Lot-Garonne-Gironde fluvial system can be considered as a natural model for pollution in non-ferrous metals such as Cd, Zn, Ba, As (Roux & Simonet, 1987).
  • As oysters are very sensitive to this pollution, the Marennes-Oleron oyster farming located ca. 30 km to the north of the mouth of the Gironde estuary is considered at risk (Jouanneau et al., 1993).
  • This plant was founded in 1840 and is located near Decazeville, a town on the RiouMort that tributes to the Lot river ca. 200 km upstream from the Lot-Garonne confluence.
  • Several large hydroelectric dams which were built from 1945 to 1960 in the upper reaches of the Lot valley, together with the 62 smaller storage structures located downstream from the Riou-Mort confluence, decrease the magnitude of winter and spring floods (Massio, 1976).

Sampling and methods

  • Because the Lot river is the major polluting tributary of the Garonne, and then of the Gironde, it was necessary to obtain a representative estimation of its total suspended sediment (TSS) fluxes.
  • Samples from Temple (Lot) were collected automatically using a Buhler PB-MOS sampler, whilst samples from the five remaining sites were collected manually.
  • At both sites, these tests showed that variations in TSS concentrations due to depth and distance from the bank did not exceed 6% and 2.3% during flood and base flows, respectively.
  • Each sample was left on a hotplate until the residue was completely dissolved and then brought to 5 ml in a volumetric flask using double-deionized water.
  • The results of the cadmium analysis for 79 suspended sediment and 99 water samples collected during year 1996 are reported in Tables 3 and 4.

Results

  • River discharge, total suspended sediment (TSS) and cadmium concentrations are the major parameters for the estimation of dissolved and particulate matter fluxes.
  • Note that the higher TSS concentrations correspond to the higher river water flows, as previously recorded for numerous rivers (Meybeck, 1992).

Discussion

  • As the frequency of TSS sampling is high, the quantification of the annual TSS fluxes (FT SS) in the Lot-Garonne system is based on the assumption that the TSS concentration remained constant between two consecutive samples (i.e. day after day).
  • Considering the errors due to the sampling and analytical methods and those deriving from the Qriv determination, the precision is about 15% for theFTSS at Temple (Lot), Port Pascau and La Reole .
  • As the daily mean TSS fluxes are well known, the annual particulate cadmium fluxes can be estimated from the assumption of the constant concentration given by Meybeck et al. (1994) as follows: = 63651 FTSS .
  • The results calculated for 1996 show that about 48% of cadmium flux through the Garonne is contributed by the Lot river.
  • This result is comparable to others obtained since 1990 (Lapaquellerie et al., 1996).

Sources of cadmium

  • The annual atmospheric cadmium flux (1994) was estimated by determining the cadmium concentration of rain water collected by two rain gauges installed at Temple (downstream Lot) and at Castelnau Lassout (upstream Lot) .
  • These results are comparable to those obtained from two short surveys in February and June 1994 made by the “Agence de l’Eau Adour-Garonne” (1995).
  • Furthermore, the authors note that only about 20% of the cadmium is transported by the Riou-Mort river in particulate forms.
  • Using a corrected temperature diffusion coefficient of 3.3 10−6 cm2 s−1 for cadmium (Lerman, 1979), dissolved cadmium diffusion fluxes of 25 10−6 and 9.2 10−6 ng cm−2 s−1 were computed from the concentration gradients obtained between the interstitial and the deep water at Cajarc and Temple, respectively.

Cadmium mass balance

  • This result can be tested by a simple model that shows the change of the cadmium concentrations as a function of dilution from the Riou-Mort to the Gironde estuary.
  • The parameters for calculation are presented in Table 6, and the calculated concentrations are compared to those measured in Figure 4.
  • This comparison shows that the calculated dissolved cadmium concentrations are higher than those measured from the Riou-Mort to La Réole, whereas the measured concentrations are higher than those calculated in the estuary.
  • They are the natural cadmium delivered by the Lot catchment (i.e. 0.44 t yr−1), the cadmium released from the sediment blanketing the Lot river bed (i.e. 0.32 t yr−1), the Riou-Mort cadmium discharge which is the value given by the dilution model (1.11 t yr−1), and the cadmium which is deduced to be removed from solution (4.26 t yr−1).
  • This value is clearly comparable to that determined using the box model.

Conclusion

  • The annual river discharge for the Lot-Garonne fluvial system during 1996 is representative of the longerterm mean.
  • The flux estimates presented in this study are based upon regular high frequency measurement for a large study basin and algoritihms recommended by Meybeck et al. (1994).
  • These algorithms are similar to those used for British rivers (Webb et al., 1997).
  • Within a distance of 0.5 km from this anthropogenic source, about 97% of dissolved cadmium input is taken up by the suspended solid phase.
  • These are between the Riou-Mort and Bouillac on the Lot river, and from La Réole to Bordeaux at the GaronneGironde fresh/salt water interface.

Did you find this useful? Give us your feedback

...read more

Content maybe subject to copyright    Report

Hydrobiologia 410: 331–341, 1999.
J. Garnier & J.-M. Mouchel (eds), Man and River Systems.
© 1999 Kluwer Academic Publishers. Printed in the Netherlands.
331
A cadmium budget for the Lot-Garonne fluvial system (France)
G
´
erard Blanc, Yvon Lapaquellerie, No
`
ele Maillet & Pierre Anschutz
epartement de G´eologie et Oc´eanographie (D.G.O.), Universit´e Bordeaux 1, UMR CNRS 5805 EPOC., Avenue
des Facult´es, 33405 Talence cedex, France
E-mail: blanc@geocean.u-bordeaux.fr
Key words: pollution, cadmium budget, Lot-Garonne rivers
Abstract
Routine measurements of river discharge and total suspended sediment concentration (TSS) are combined with
regular analyses for particulate and dissolved cadmium to produce a box model that allows us to propose a cad-
mium mass balance for the Lot-Garonne man-influenced river system (8400 km
2
). Nearly half the cadmium in the
Garonne river is supplied by the tributary Lot river. Cadmium input onto the Lot river comprises wet deposition
from the atmosphere, molecular diffusion at the sediment-water interface, surface-water runoff and discharge from
the leaching of waste at a zinc refining plant. Approximately 85% of the cadmium in the Lot river is derived from
anthropogenic origin. Cadmium in the industrial discharge is 80% dissolved and 20% in the particulate phase (4.2
and 1.1 t yr
1
, respectively). Total inputs are estimated at 4.81 t yr
1
and 1.54 t yr
1
for the dissolved cadmium
and for the particulate phase, respectively. Budgeting estimates an output onto the Garonne river of 0.54 t yr
1
for the dissolved cadmium (about 8%) and 6.13 t yr
1
for the particulate cadmium (about 92%) indicating that
downstream sediment-associated cadmium fluxes are enhanced by the 4.27 t yr
1
removed from solution and the
0.32 t yr
1
remobilized by the erosion of sediment blanketing the Lot river bed. These figures are found to be
comparable with those generated by a dilution model which suggests that 97% of dissolved cadmium is taken up
by the particulate phase over 0.5 km downstream from the primary anthropogenic source.
Introduction
Although the Aquitaine basin is one of the least indus-
trialised regions in France, the Lot-Garonne-Gironde
fluvial system can be considered as a natural model for
pollution in non-ferrous metals such as Cd, Zn, Ba, As
(Roux & Simonet, 1987). Historically, chronic pollu-
tion has resulted from industrial and mining activities
that started to develop in the late nineteenth century
and in particular, cadmium, which has a high toxicity
for biota, is considered as the major polluting metal
of this fluvial system. Cadmium pollution was first
recognised in 1979 within the framework of the ‘Na-
tional Observation Network’ (Latouche, 1988) which
documented the high cadmium content in the flesh of
the Gironde oysters (up to 100 µgg
1
of dry matter).
These concentrations are 10 times higher than those
typically found in oysters from French non-industrial
areas (Boutier, 1981) and reflect the high kinetics ac-
cumulation in oysters. As oysters are very sensitive
to this pollution, the Marennes-Oleron oyster farming
located ca. 30 km to the north of the mouth of the
Gironde estuary is considered at risk (Jouanneau et al.,
1993).
The primary source for present day cadmium pol-
lution is probably attributed to leaching from the waste
area of a now abandoned zinc ore manufacturing facil-
ity (Latouche, 1992). This plant was founded in 1840
and is located near Decazeville, a town on the Riou-
Mort that tributes to the Lot river ca. 200 km upstream
from the Lot-Garonne confluence. However, several
large hydroelectric dams which were built from 1945
to 1960 in the upper reaches of the Lot valley, together
with the 62 smaller storage structures located down-
stream from the Riou-Mort confluence, decrease the
magnitude of winter and spring floods (Massio, 1976).
This has resulted in significant sediment and cadmium
accumulation in the lower reaches of the Lot river.
Lapaquellerie et al. (1995) estimated that 0.47 ± 0.9
× 10
6
m
3
of sediment and about 200 tons of cadmium

332
accumulated in the Lot valley between the Riou-Mort
and Garonne river in 1991.
This paper aims to establish a macroscopic de-
scription of cadmium behaviour in the Lot-Garonne
fluvial system (8400 km
2
) by using the annual (1996)
flux of both the particulate and dissolved phases. By
quantifying the contributions from the primary source
(i.e. the Riou-Mort river) and the secondary source
(i.e. the sediment-associated cadmium in the Lot
river), together with internal transfert processes and
the overall output, we propose a tentative cadmium
budget for the Lot-Garonne study basin.
Sampling and methods
Because the Lot river is the major polluting tributary
of the Garonne, and then of the Gironde, it was neces-
sary to obtain a representative estimation of its total
suspended sediment (TSS) fluxes. This was accom-
plished using a total of six sampling sites (Figure 1).
Samples from Temple (Lot) were collected automatic-
ally using a Buhler PB-MOS sampler, whilst samples
from the ve remaining sites were collected manually.
The automatic sampler collects a daily cumulative 1
l sample consisting of 16 elementary samples. The
frequency of TSS measurements and analyses for par-
ticulate and dissolved cadmium is reported in Table 1.
Transverse and depth profiling was undertaken to test
the representativeness of our local sampling at Temple
and La Reole sites (cf. Lapaquellerie et al., 1996).
At both sites, these tests showed that variations in
TSS concentrations due to depth and distance from
the bank did not exceed 6% and 2.3% during flood
and base ows, respectively. TSS concentrations were
determined using filtration (Whatmann GF/F, 0.70 µm
filters) and each sample set typically showed a stand-
ard deviation of 1.5% about the mean. The annual
mean values of the TSS concentrations for each site
are reported in Table 2.
The mean annual discharge (1996) for the Lot
and Garonne rivers was calculated using the daily
measurements undertaken by the autonomous port of
Bordeaux and the hydrological office of Toulouse (see
Table 2). The precisionis generallyabout5% for water
flows higher than 40 m
3
s
1
.
Sediment-associatedcadmiumconcentrationswere
determined from bulk suspended sediment samples re-
trieved by centrifuging between 500 and 1000 l of
water using a Wesfalia separator. The cadmium con-
tamination from this equipment is much less than
the analytical error which is about 5% (Etcheber &
Jouanneau, 1980).
The water samples were collected and filtered for
cadmium analyses using a clean technique. Surface-
water samples were taken from a small rubber dinghy,
by immersing a teflon sampler specially designed to
avoid any contact with the atmosphere. This sampler
holds a 100 cm
3
acid-cleaned polypropylene vial.
The water samples were immediately filtered through
acid-cleaned 47 mm diameter, 0.45 µm pore-size)
Nuclepore polycarbonate membranes.
Triplicate analyses for the particulate and dissolved
cadmium concentrations of individual samples were
undertaken using a graphite furnace atomic absorption
spectrometer. Particulate cadmium analyses required
the complete dissolution of individual dried solid
samples. The total digestion used by this study in-
volved the dissolution of 30 mg of each sample in 750
µl HCl (12N), 2 ml HF (26N) and 250 µl HNO
3
(14N)
in small Teflon bombs. The bomb were then heated at
110
C for 2 h, and after cooling, the digested solution
was evaporated to dryness and the residue dissolved in
150 µl concentrated HNO
3.
Each sample was left on
a hotplate until the residue was completely dissolved
and then brought to 5 ml in a volumetric flask using
double-deionized water. Prior to the determination of
dissolved cadmium content, the samples were precon-
centrated in a class 100 clean room by complexating
with ammonium pyrrolidine dithiocarbamate/ diethyl-
ammonium diethyl dithiocarbamate (APDC/DDDC),
extracting into freon and back extracting with HNO
3
into deionized water (Danielsson et al., 1982). In the
Riou-Mort tributary, dissolved concentrations were
high enough to be analyzed directly, without precon-
centration. Accuracy of the analyses was determined
by comparisons to river sediment (CRM320) and wa-
ter (SLRS3) international standards, and was within
5% for cadmium. The precision of the analyses, as
determined from duplicate samples was generally 5%
for cadmium at concentrations 10 times higher than
the detection limit. The content of cadmium in solid
phases is given in milligrams per kg, whereas the dis-
solved cadmium content is given in nanograms per l.
The results of the cadmium analysis for 79 suspended
sediment and 99 water samples collected during year
1996 are reported in Tables 3 and 4.
Results
River discharge, total suspended sediment (TSS) and
cadmium concentrations are the major parameters for

333
Figure 1. Sampling locations in the Garonne river, Lot river, and its tributaries (Riou-Mort, C
´
el
´
e), and also at the Verdon (estuary mouth).
Table 1. Location and sampling frequencies for the study sites, x and y are the coordinates in Lambert III projection, South
Area
Sites Map Location Sampling Sampling strategy
x / y Type TSS dis.Cd part.CD
Riou-Mort IGN 2238 W 560.05 / 3241.09 manual 8 yr
1
8yr
1
8yr
1
Bouillac IGN 2338 589.00 / 3253.45 manual 8 yr
1
6yr
1
5yr
1
Cajarc IGN 2238 W 560.05 / 3241.09 manual 5 yr
1
39 yr
1
5yr
1
Temple sur Lot IGN 1839 W 453.55 / 3234.00 Automatic sampler 365 yr
1
18 yr
1
18 yr
1
Port Pascau IGN 1739 E 439.07 / 3323.00 manual 365 yr
1
18 yr
1
18 yr
1
La R´eole IGN XV-37 (3–4) 374.22 / 280.20 manual 365 yr
1
18 yr
1
18 yr
1
Le Verdon IGN XIV-33 (1–2) 334.62 / 62.18 manual 4 yr
1
5yr
1
6yr
1
the estimation of dissolved and particulate matter
fluxes. The riverdischarge can vary by factorsof about
45 and 30 for the Garonne and Lot rivers, respectively.
At the beginning of a ood such maximum changes in
river discharge can usually be observed during a single
day. In addition, the TSS concentrations change by a
factor greater than one thousand between the flood and
the lowest water level periods. At La Réole, the TSS
concentration reached up to 1300 mg l
1
in Decem-
ber, whereas it fell down to 0.3 mg l
1
in September
(Table 2). The annual mean value of TSS concentra-
tion varies spatially, increasing from 25 mg l
1
the
Riou-Mort to 110 mg l
1
Cajarc. Conversely, the TSS
concentration at Temple shows an annual mean value
of 98 mg l
1
. This lower value probably results from
the settling of the suspended sediment into the nu-
merous reservoirs. In 1996, the TSS concentration at
Port-Pascau (Garonne) was approximately twice that
of the downstream Lot. The changes in concentration
of the particulate and dissolved cadmium show a tem-
poral variability less than that of TSS concentration.
Thus, it was not necessary to collect a sample every
day, although the oods were sampled.
In 1996, the mean particulate cadmium concentra-
tions decreased progressively from 460 mg kg
1
at
the Riou-Mort to 12.5 mg kg
1
at Temple (Table 3).
They were 10 times lower at Port-Pascau, and,
consequently, a mean cadmium concentration of
2.6 mg kg
1
was determined at La Réole, downstream
of the junction of the Lot and Garonne rivers. Because
of the chlorinity increases in the Gironde estuary, the
particulate cadmium concentrations reach a minimum
mean value of 0.43 mg kg
1
at Le Verdon. The mean
particulate cadmium concentration of 2.59 mg kg
1
,
determined in 1996 at La Réole, is comparable to
that given by Elbaz-Poulichet (1988) for the Rhône
river, and that given by Chiffoleau et al. (1997) for
the Seine river (i.e. 2.8 mg kg
1
), but much lower the

334
Table 2. 1996 mean, maximum and minimum values for river discharge (m
3
.s
1
) and TSS concentration (mg.l
1
) at each sampling
site
Riou-Mort Bouillac Cajarc Temple Port Pascau La R´eole Le Verdon
mean 3 80 89 171 637 808 1200
River discharge (m
3
s
1
) max 35 431 480 922 3523 3928 4748
min 8 18 22 30 32 85 170
mean 25.4 99.9 110.4 98.5 207.4 182.9 151.9
TSS (mg l
1
) max 81 196 205 390 1105 1297 313
min 13 45 10 6 0.2 0.3 35
Table 3. Particulate cadmium concentrations determined at each site in 1996
Riou Mort Bouillac Cajarc Temple Port Pascau La R´eole Le Verdon
(mg kg
1
) (mg kg
1
) (mg kg
1
) (mg kg
1
) (mg kg
1
)(mgkg
1
) (mg kg
1
)
Jan 04 11.3 0.69 2.53
Jan 12 15.2 0.34 2.34
Jan 24 16.1 0.33 1.91
Jan 28 0.56
Feb 5 15.9 0.74 1.47
Feb 28 12.3 1.32 1.58
Mar 28 10.4 1.24 2.34
Apr 17 484 17.3 23.1
Apr 29 16.0 1.2 3.6
May 16 0.94
May 23 10.8 1.31 3.52
May 24 504 29.3 17.1
Jun 10 0.48
Jun 28 767 7.7 1.59 2.34
Jul 10 350 22.5 26.7
Jul 18 8.1 1.69 2.45
Aug 28 13.6 1.39 2.33
Sep 02 244
Sep 06 0.21
Sep 10 689 29.9 21.7
Sep 26 16.9 1.67 3.02
Oct 08 16.9 2.29 3.8
Oct 15 0.18
Oct 28 286 10.2 2.56 2.22
Nov 07 7.4 1.15 3.3
Nov 22 12.1 1.86 2.01 0.21
Dec 04 386 33.1 14.5
Dec 10 14.6 2.44 3.1
Dec 19 9.4 2.13 2.17
Dec 23 432
Mean value 460 26.4 20.6 12.5 1.44 2.59 0.43

335
Table 4. Dissolved cadmium concentrations determined at each site in 1996
Riou-Mort Bouillac Cajarc Temple Port Pascau La R´eole Le Verdon
(ng l
1
)(ngl
1
)(ngl
1
)(ngl
1
)(ngl
1
)(ngl
1
)(ngl
1
)
Jan 04 340 65 16 29
Jan 12 134 48 48 33
Jan 24 420 72 48 28
Jan 28 385
Feb 5 532 97 49 64
Feb 28 158 105 54 42
Mar 28 245 64 58 95
Apr 17 25 000 139 593
Apr 29 169 43 32 88
May 23 433 15 24 59
May 24 25 600 975 150
Jun 03 176
Jun 04 134
Jun 10 481
Jun 28 49 800 810 255 56 200
Jul 10 34 300 346
Jul 18 628 230 120 185
Aug 26 245
Aug 27 284
Aug 28 179 110 110 315
Sep 02 534
Sep 03 157
Sep 04 608
Sep 06
Sep 10 80 300 1860 467
Sep 26 303 20 64 52
Oct 08 252 210 83 32
Oct 15 320
Oct 28 16 500 128 240 45 41
Nov 07 640 35 87 34
Nov 14 635 94 19 38
Nov 22 245
Dec 04 67280 1135 325
Dec 10 436 110 70 44
Dec 19 87 99 32
Dec 23 53600 1230
Mean value 44 048 1025 340 106 60 78 380
32 mg kg
1
given by Van der Weijden et al. (1989) for
the Rhine. However, Idlafkih et al. (1995) gave a value
of 4.9 mg kg
1
for the Seine river.
The dissolved cadmium concentration in 1996 av-
eraged 44000 ng l
1
in the Riou-Mort (Table 4).
This high content rapidly decreased downstream and
reached a value of 106 ng l
1
at Temple. The mean
dissolved cadmium concentrations at the Garonne
river sites in 1996 were slightly lower, and thereafter
increased by a factor of four (i.e. 380 ng l
1
)atLe
Verdon, where the salinity ranged from 14 to 24 ‰.
An average value of 400 ng l
1
was previously de-
termined for a comparable salinity range (Jouanneau
et al., 1990), although Kraepiel et al. (1997) meas-

Citations
More filters

Journal ArticleDOI
TL;DR: 137Cs activities and heavy metal concentration-depth profiles from sediment cores retrieved in 2001 from three reservoirs in the Lot River allow establishing a connection between the temporal evolution of the heavy metal pollution and historical changes in smelting and waste-treatment proceedings.
Abstract: The Lot–Garonne fluvial system is known for its historic heavy metal pollution resulting from mining and smelting activities since the late 19th century. Here, we report 137 Cs activities and heavy metal (Cd, Zn, Cu, Pb and V) concentration–depth profiles from sediment cores retrieved in 2001 from three reservoirs in the Lot River. High mean sedimentation rates of 2.4–2.8 cm a −1 are indicated by 137 Cs dating. The reservoir sediments have recorded the heavy metal deposition and thus allow establishing a connection between the temporal evolution of the heavy metal pollution and historical changes in smelting and waste-treatment proceedings. Based on heavy metal concentrations in sediments upstream of the anthropogenic inputs and bottom-sediments of the furthest downstream core (interpreted as old soil or riverbed), concentrations of ∼17, ∼82, ∼0.33 and ∼28 mg kg −1 for Cu, Zn, Cd and Pb, respectively, are proposed as natural background values for the Lot fluvial system. The geoaccumulation index ( I geo [Muller, G., 1979. Schwermetalle in den Sedimenten des Rheins-Veranderungen seit. Umschav 79, 133–149.]) revealed that the Lot River sediments must be considered as “severely polluted” in Cd and Zn. Moreover, despite remediation efforts undertaken in the former smelting site, the Lot River is still “severely” ( I geo ∼ 4) and “moderately to severely” ( I geo > 2) impacted by Cd and Zn inputs, respectively.

407 citations


Journal ArticleDOI
TL;DR: In a metal-polluted stream in the Riou Mort watershed in SW France, periphytic diatom communities were affected by the metal but displayed induced tolerance, seen through structural impact (dominance of small, adnate species) as well as morphological abnormalities particularly in the genera Ulnaria and Fragilaria.
Abstract: In a metal-polluted stream in the Riou Mort watershed in SW France, periphytic biofilm was analyzed for diatom cell densities and taxonomic composition, dry weight and metal bio-accumulation (cadmium and zinc). Periphytic diatom communities were affected by the metal but displayed induced tolerance, seen through structural impact (dominance of small, adnate species) as well as morphological abnormalities particularly in the genera Ulnaria and Fragilaria. Species assemblages were characterized by taxa known to occur in metal-polluted environments, and shifts in the community structure expressed seasonal patterns: high numbers of Eolimna minima, Nitzschia palea and Pinnularia parvulissima were recorded in Summer and Autumn, whereas the species Surirella brebissonii, Achnanthidium minutissimum, Navicula lanceolata and Surirella angusta were dominant in Winter and Spring. Commonly used indices such as the Shannon diversity index and Specific Pollution Sensitivity Index reflected the level of pollution and suggest seasonal periodicity, the lowest diversities being observed in Summer.

191 citations


Journal ArticleDOI
TL;DR: Results suggest trace metal recycling due to reductive dissolution under suboxic conditions at the sediment surface resulting in trace metal release to the water column and adsorption onto suspended particles.
Abstract: A 15-month experiment combining a geochemical survey of Cd, Cu, Zn and Hg with a bioaccumulation study for three filter-feeding bivalve species (oysters, Crassostrea gigas; cockles, Cerastoderma edule; and clams, Ruditapes philippinarum) was conducted in a breeding basin of the Nord Medoc salt marshes connected to the Gironde estuary, which is affected by historic polymetallic pollution. Regular manual surface measurements of temperature, salinity, pH and dissolved O(2) concentration and hourly multiprobe in situ measurements throughout several periods for 6-8 weeks were performed. The geochemical behavior of metals in water, suspended particulate matter and sediment and their ecotoxicological impact on the three bivalve species were evaluated by in situ exposure of juvenile oysters (water column) and adult cockles and clams (sediment surface). The physico-chemical parameters reflected seasonal variations and basin management. A distinct daily periodicity (except salinity) indicated intense photosynthesis and respiration. In summer, low dissolved O(2) saturations ( approximately 40-50%) occurred in the early morning at 30 cm above the sediment, whereas in depressions, the water column near the sediment surface was suboxic. Cadmium, Zn and Cu concentrations in suspended particulate matter exceeded typical estuarine values and were much higher than the homogeneously distributed concentrations in different depth ranges of the basin sediment. Particles collected in sediment traps showed intermediate metal concentrations close to sediment values. These results suggest trace metal recycling due to reductive dissolution under suboxic conditions at the sediment surface resulting in trace metal release to the water column and adsorption onto suspended particles. Dissolved Cd, Zn and Hg concentrations (e.g. 13-136 ng l(-1); 0.3-25.1 microg l(-1) and 0.5-2.0 ng l(-1), respectively) in the basin corresponded to the concentration range typically observed in the Gironde estuary, except for some maximum values attributed to metal recycling. In contrast, dissolved Cu concentrations (1.08-6.08 microg l(-1)) were mostly higher than typical estuarine values, probably due to recycled Cu complexation by dissolved organic matter. Growth, bioaccumulation rates and kinetics in the whole soft body of the bivalves were analyzed every 40 days. Although Cd bioaccumulation of oysters was lower in the basin than in the estuary during the same period (27,000 ng g(-1), dry weight and 40,000 ng g(-1), respectively) these values are largely above the new human consumption safety level (5000 ng g(-1), dw; European Community, 2002). For cockles and clams, Cd bioaccumulation was lower, reaching 1400 ng g(-1) and 950 ng g(-1), respectively. Similar results were obtained for Zn and Cu suggesting physiological differences between the species and/or differences in the exposure of the organisms due to physico-chemical conditions and metal distribution between dissolved and particulate phases. In contrast, Hg bioaccumulation was highest for cockles reaching bioconcentration factors of approximately 200,000, which even exceeded that of Cd in oysters (50,000) for the same exposition period. Nevertheless, Hg concentrations remained relatively low in the three bivalve species.

130 citations


Journal ArticleDOI
Abstract: ARTICLE I NFO Zn values up to +1.49‰. Zn extraction yields for these samples were calculated using presumable conservative elements (Fe, Ca, Mg, K, Na and Mn) and vary from 95.4% to 99.4%. Extraction yields are related to the intensity of Zn isotopic fractionation. Different Rayleigh isotope fractionation scenarios for Zn refining yielded αore-tailings ranging from 1.00012 to 1.00062. The δ 66 Zn of the Riou Mort sediments downstream from

128 citations


Journal ArticleDOI
Abstract: Heavy metal (Zn, Cd, Cu and Pb) mass balances in the Lot-Garonne fluvial system have been established for 1999 and 2000. The mean annual discharges of these years are close to the mean discharge of the previous decade. The estimated annual dissolved and particulate fluxes in this model watershed integrate daily input from diffuse and point sources, diffusive fluxes at the water/sediment interface, changes in the dissolved-particulate partition and changes in sediment stock. Cadmium, Zn, Cu and Pb entering the Gironde estuary via the Garonne River (11–14 t a−1 of Cd; 1330–1450 t a−1 of Zn; 126–214 t a−1 of Cu and 127–155 t a−1 of Pb) are mainly transported in the particulate phase and the major part (i.e. ∼74 to 96% for Cd, ∼60% for Zn, ∼50 to 60% for Cu and ∼80% for Pb) is transported by the Lot River. The main anthropogenic heavy metal point source is located in a small upstream watershed (Riou-Mort River) accounting for at least 47% (Cd), ∼20% (Zn), ∼4% (Cu) and ∼7 to 9% (Pb) of the total heavy metal inputs into the Garonne River, although it contributes only 1% of the discharge. Mass balances for 1999 suggest that under mean annual hydrologic conditions on the basin scale, the heavy metal budget of the Lot-Garonne fluvial system is balanced and that the stocks of Cd [200 t; Environ. Tech. 16 (1995) 1145] and Zn in the Lot River sediment are constant under mean discharge conditions. Heavy metal input by molecular diffusion at the sediment surface represents an important component of dissolved metal inputs into the system (e.g. 30% for Cu). Except for Cu, these dissolved inputs are totally removed from solution by SPM. Based on the generally constant Zn/Cd (∼50) concentration ratio in sediment cores from the polluted Lot River reaches and the sediment stock of Cd [200 t; Environ. Tech. 16 (1995) 1145], the present day Zn stock in the Lot River sediments has been estimated at about 10,000 t. In addition to the mobilization of river-bed sediment and associated heavy metals by intense floods, local human activities, including river-bed dredging, may strongly modify the heavy metal budget of the river system. In 2000, the dredging-related remobilization of polluted Lot River sediment released 2–6 t Cd. This additional Cd point source was estimated to account for 15–43% of the gross inputs into the Gironde Estuary.

125 citations


References
More filters


Book
01 Jan 1979
Abstract: The approach of this book to geochemistry can be summarized in the question: What happens, and how fast does it happen, when waters, solids, and gases interact in the earths surface environment? The environment of the earths surface is made of solids and fluids, and theinteractions among them are responsible for much of what is taking place in the physical world around us. The dissolved load of natural waters and the materials of which sediments are made are the products of reactions taking place practically everywhere on land, in the atmosphere, and in the hydrosphere. Thus the term water and sediment environments applies effectivelly to much of the surface environment of the earth, including the zone of up to a few kilometers above and below the land and ocean surface. Evolution present itself to us as a more or less complex variety of processes-geological, physical, chemical, and biological. To this end, the inclusive title Geochemical Processes was chosen for the book, to introduce a text that emphasizes processes and time-dependent phenomena.

666 citations


"A cadmium budget for the Lot-Garonn..." refers background in this paper

  • ...for cadmium ( Lerman, 1979 ), dissolved cadmium diffusion fluxes of 25 10 6 and 9.2 10 6 ng cm 2 s 1...

    [...]


Book ChapterDOI
01 Jan 1983
Abstract: The objectives of this paper are to review the role of rivers as a pathway of chemical elements from the land to the ocean and to assess the significance of river input of pollutants to oceanic chemistry.

520 citations


BookDOI
01 Jan 1983
Abstract: Session I: Metalloids and the Hydride Generation.- The Determination of the Chemical Species of Some of the "Hydride Elements" (Arsenic, Antimony, Tin, and Germanium) in Sea Water: Methodology and Results.- Antimony Content and Speciation in the Water Column and Interstitial Waters of Saanich Inlet.- Ultratrace Speciation and Biogenesis of Methyltin Transport Species in Estuarine Waters.- The Relationship of the Distribution of Dissolved Selenium IV and VI in Three Oceans to Physical and Biological Processes.- Session II: Arctic Chemistry.- Trace Metals in the Arctic Ocean.- Copper in Sub-Arctic Waters of the Pacific Northwest.- Low Level Determination of Trace Metals in Arctic Sea Water and Snow by Differential Pulse Anodic Stripping Voltammetry.- The Relationship between Distributions of Dissolved Cadmium, Iron, and Aluminium and Hydrography in the Central Arctic Ocean.- Session III: Intercalibration Exercise.- Intercomparison of Seawater Sampling Devices for Trace Metals.- The Analysis of Trace Metals in Biological Reference Materials: A Discussion of the Results of the Intercomparison Studies Conducted by the International Council for the Exploration of the Sea.- An Intercomparison of Sampling Devices and Analytical Techniques Using Sea Water from a CEPEX Enclosure.- Session IV: Estuarine Processes Involving Metals.- Role of Fresh Water/Sea Water Mixing on Trace Metal Adsorption Phenomena.- Effects of Particle Size and Density on the Transport of Metals to the Oceans.- The Effect of Sewage Effluents on the Flocculation of Major and Trace Elements in a Stratified Estuary.- Impoverishment and Decrease of Metallic Elements Associated with Suspended Matter in the Gironde Estuary.- The Significance of the River Input of Chemical Elements to the Ocean.- Session V: Air/Sea Exchange and Coastal Processes Involving Metals.- Air-Sea Exchange of Mercury.- Separation of Copper and Nickel by Low Temperature Processes.- The Fate of Particles and Particle-Reactive Trace Metals in Coastal Waters: Radioisotope Studies in Microcosms.- Trace Metals in a Landlocked Intermittently Anoxic Basin.- Session VI: Ocean Distribution and Analysis.- Thorium Isotope Distributions in the Eastern Equatorial Pacific.- Aspects of the Surface Distributions of Copper, Nickel, Cadmium, and Lead in the North Atlantic and North Pacific.- Mn, Ni, Cu, Zn, and Cd in the Western North Atlantic.- Some Recent Measurements of Trace Metals in Atlantic Ocean Waters.- Determination of the Rare Earth Elements in Sea Water.- The Cycle of Living and Dead Particulate Organic Matter in the Pelagic Environment in Relation to Trace Metals.- Trace Metal Levels in Sea Water from the Skagerrak and the Kattegat.- Mercury Concentrations in the North Atlantic in Relation to Cadmium, Aluminium and Oceanographic Parameters.- Perturbations of the Natural Lead Depth Profile in the Sargasso Sea by Industrial Lead.- Copper, Nickel and Cadmium in the Surface Waters of the Mediterranean.- Accurate and Precise Analysis of Trace Levels of Cu, Cd, Pb, Zn, Fe and Ni in Sea Water by Isotope Dilution Mass Spectrometry.- Session VII: Chemical Speciation.- Studies of the Chemical Forms of Trace Elements in Sea Water Using Radiotracers.- Trace Metals (Fe, Cu, Zn, Cd) in Anoxic Environments.- The Behavior of Trace Metals in Marine Anoxic Waters: Solubilities at the Oxygen-Hydrogen Sulfide Interface.- Variations of Dissolved Organic Copper in Marine Waters.- Trace Metals Speciation in Nearshore Anoxic and Suboxic Pore Waters.- The Contrasting Geochemistry of Manganese and Chromium in the Eastern Tropical Pacific Ocean.- Potentialities and Applications of Voltammetry in Chemical Speciation of Trace Metals in the Sea.- Studies of Cadmium, Copper and Zinc Interactions with Marine Fulvic and Humic Materials in Seawater Using Anodic Stripping Voltammetry.- Chemical Periodicity and the Speciation and Cycling of the Elements.- Potentiometric and Conformational Studies of the Acid-Base Properties of Fulvic Acid from Natural Waters.- Copper Speciation in Marine Waters.- Session VIII: Metals and the Biosphere.- Plankton Compositions and Trace Element Fluxes from the Surface Ocean.- Metals in Seawater as Recorded by Mussels.- Trace Elements and Primary Production: Problems, Effects and Solutions.- Trace Metals and Plankton in the Oceans: Facts and Speculations.- Sensitivity of Natural Bacterial Communities to Additions of Copper and to Cupric Ion Activity: A Bioassay of Copper Complexation in Seawater.- List of Participants.- Index of Authors.

474 citations


Journal ArticleDOI
Abstract: Using clean techniques, we measured the dissolved, particulate, and (by cross-flow filtration) colloidal fractions of Cd, Ni, Zn, Cu, Pb, Mn, and Fe in the Gironde, an estuary in southwestern France. The fractions of the particulate riverine metals that are apparently mobilized in the estuary vary from >90% for Cd to less than 2% for Pb. Observed mid-salinity maxima for Cd, Ni, and Zn are well reproduced by a simple steady-state conservation model which accounts for the inorganic complexation of the metals by seawater anions. The concentration profiles of other metals, except Fe, can also be modeled by choosing an appropriate desorbable fraction and maintaining equilibrium between particles and solution. While colloidal iron decreases rapidly at low salinities, the colloidal concentrations of the other metals are quasi-conservative in the estuary. It appears that the colloidal fraction contains both iron oxide particles that separate from the rest by coagulation and organic macromolecules which bind most of the other metals and remain in solution.

190 citations