transported into the estuarw Second, it seems that only direct anthropogenic sources of methylmercuty can cxplain the high proportion of
this toxic compound. Additionally, the highest average concentrations
of methylmercury were obtained in the middle and lower sections of
the Nerviôn estuary for the dissolved phase and in the upper section
for the particulate phase.
Mercury distribution and speciation in the Nerviôn river and its tributaries during the period
November 1998 to October 1999 (n is the number of the sampies).
Stations
SPM
mg 1
1
Hg(U) D
ng 1 1
MMHg D
ngl'
Hg(H) r
Mfig 1
drv wt.
MMHg p
Ogg’
1
drv wt.
Hg T
ng 1 -1
%Hg p % MMHg
Toral
1. Nerviôn
99.8
1150
402
79.8
17.8
4195
64
21
low estuaty
(Galindo)
n=6
6-3X5
21-71157
0-2055
7-374
0.1-107
236-10779
/ 5-95
3- IX
2. Nerviôn
11.9
846
501
48.6
4.7
1996
47
34
middie
estuaty
(Zorrotsa)
n=6
4.2-16.4
0-1977
X-2604
0-19/
o-l 1
IX-9X13
16-79
8-100
3. Nerviôn
15.2
466
190
292.6
29.0
1251
44
32
upper estuary
n=6
0.X-55.3
9-97/
14-462
0.S-/X4X
0-121
60-10 5X
12-71
11-56
4. Nerviôn
9.4
419
284
21.4
10.9
988
38
31
river
n=6
4. 5-/7.x
1-1120
7-7 3 X
0-46
0-26.1
54-26 55
0-X5
5-55
5. Nerviôn
6.1
241
169
18.9
17.8
505
37
38
river
(Arrigoriaga)
n=5
0.7-X.9
7-624
0-57 X
O-XO
0-57
4 5-146!
5-XI
0-66
6. Ibaizabal
10.0
739
199
25.3
7.1
1101
40
20
n=6
2.6-20.9
0-25X2
0-655
1.6-141
0-17.7
32-1411
5-100
0-49
7. Kadagua
5.3
304
119
3.2
8.3
463
29
36
n=6
1-11.4
0-1 101
0-592
0-14.4
0-3S.7
IX-20 56
0-97
0-94
The mcrcurv species concentrations vaty significantly during the sampling period. Maximal concentrations were obtained in May 1999 for
the estuarine samples and in March 1999 for the Ibaizabal and Kadagua
rivers (tributaries) (fig. 2). For all samples, the maximums for the Hg(JI)
and MMHg concentrations do not correspond to the peak of the river
discharge, but were found two months after the flood periods. It is suggested that the higher river discharge has a dilution effect, like in the
Seine estuary (Coquerv et al, 1997), which is then followed bv a
remobilization and accumulation period at low river discharge (Tseng,
2000). Both Hg(ll) and MMHg usually present similar seasonal trends,
indicating that they have both identical pollution pathways.
310
this toxic compound. Additionally, the highest average concentrations
of methylmercury were obtained in the middle and lower sections of
the Nerviôn estuary for the dissolved phase and in the upper section
for the particulate phase.
Mercury distribution and speciation in the Nerviôn river and its tributaries during the period
November 1998 to October 1999 (n is the number of the sampies).
Stations
SPM
mg 1
1
Hg(U) D
ng 1 1
MMHg D
ngl'
Hg(H) r
Mfig 1
drv wt.
MMHg p
Ogg’
1
drv wt.
Hg T
ng 1 -1
%Hg p % MMHg
Toral
1. Nerviôn
99.8
1150
402
79.8
17.8
4195
64
21
low estuaty
(Galindo)
n=6
6-3X5
21-71157
0-2055
7-374
0.1-107
236-10779
/ 5-95
3- IX
2. Nerviôn
11.9
846
501
48.6
4.7
1996
47
34
middie
estuaty
(Zorrotsa)
n=6
4.2-16.4
0-1977
X-2604
0-19/
o-l 1
IX-9X13
16-79
8-100
3. Nerviôn
15.2
466
190
292.6
29.0
1251
44
32
upper estuary
n=6
0.X-55.3
9-97/
14-462
0.S-/X4X
0-121
60-10 5X
12-71
11-56
4. Nerviôn
9.4
419
284
21.4
10.9
988
38
31
river
n=6
4. 5-/7.x
1-1120
7-7 3 X
0-46
0-26.1
54-26 55
0-X5
5-55
5. Nerviôn
6.1
241
169
18.9
17.8
505
37
38
river
(Arrigoriaga)
n=5
0.7-X.9
7-624
0-57 X
O-XO
0-57
4 5-146!
5-XI
0-66
6. Ibaizabal
10.0
739
199
25.3
7.1
1101
40
20
n=6
2.6-20.9
0-25X2
0-655
1.6-141
0-17.7
32-1411
5-100
0-49
7. Kadagua
5.3
304
119
3.2
8.3
463
29
36
n=6
1-11.4
0-1 101
0-592
0-14.4
0-3S.7
IX-20 56
0-97
0-94
The mcrcurv species concentrations vaty significantly during the sampling period. Maximal concentrations were obtained in May 1999 for
the estuarine samples and in March 1999 for the Ibaizabal and Kadagua
rivers (tributaries) (fig. 2). For all samples, the maximums for the Hg(JI)
and MMHg concentrations do not correspond to the peak of the river
discharge, but were found two months after the flood periods. It is suggested that the higher river discharge has a dilution effect, like in the
Seine estuary (Coquerv et al, 1997), which is then followed bv a
remobilization and accumulation period at low river discharge (Tseng,
2000). Both Hg(ll) and MMHg usually present similar seasonal trends,
indicating that they have both identical pollution pathways.
310