Relative Importance of Non-Point Sources of Mercury
211
important landfill of Rio de Janeiro's metropolitan area. The landfill covers an
area of approximately 105 000 m 2 and receives over 105 t of urban wastes per year
(ABES 1983). Nearly all inputs of Hg go to the soil. However, since the landfill is
located along the major tributary of Sepetiba Bay, the Canal de Sao Francisco,
weakly bound forms of Hg can be leached to groundwater or carried out by
surface runoff and reach the adjacent rivers (Behrendt 1993). Inputs of Hg to soils
from this landfill can range from 66 to 198 kg ga -\ contributing with 75 to 90%
of the total Hg inputs to the basin soils, being the most important single source
from this urban sources group.
Plastics and rubber manufacturing and the chemical industry, are a major
industrial activity in the basin employing over 6000 people (Barcellos and
Lacerda 1994). Emissions are mostly to waterways, and account for the third
most important source of Hg to waterbodies in the basin. We use general
emission factors for this industrial category (EPA 1993), which consider Hg as an
accidental component of effluents. However, Hg is frequently used as catalyst in
the production of polyurethane and vinyl chlorine and the Hg emission is
variable, but has not been reported for Sepetiba Bay industrial park. A detailed
survey of the local plastic and chemical industry is advisable since it can
represent a significant Hg source.
Metal manufacturing is the major component of the Sepetiba Bay industrial
park. Many small and medium-sized metallurgic workshops, as well as three
larger plants, employ over 5000 people, producing over 175000 tons of metals
per year, in particular of AI, Zn and Cd. Mercury is a component of liquid and
solid wastes from metallurgical plants and these industries are an important
diffuse source of Hg in the basin. Annual contribution from this sector to water
systems is, however, very small, less than 0.4 kg. Contributions to soils as solid
residues are higher than to waters reaching 18 kg a-I and contributing with 10 to
25% of the total Hg inputs to soils. Compared to other regions, however, metal
production in Sepetiba Bay basin is a relatively small contributor of Hg. The
reason for this is probably the type of ore used by Sepetiba Bay basin plants.
Whereas most ores worked as sources of metals are sulphides, particularly
enriched in Hg, in Sepetiba Bay basin AI, Zn and Cd are produced from oxides,
with very low content of Hg. For example, emission factors from Zn and Cd
production from sulphide ores, range from 8 to 45 g C
I
(Nriagu and Pacyna
1988), which are orders of magnitude higher than the range used in our
estimates, calculated from the use of oxides.
Iron and steel production in Sepetiba Bay basin produces more than 1 million t
per year and is the major source of Hg to the atmosphere, mostly due to the
technology employed (open furnace-electric arc) and the intense use of scrap
metal, particularly enriched in Hg (OECD 1985). Inputs reach 104 kg a-I to the
atmosphere. Contribution to soils and waters from large steel and iron
production facilities may exist but they are in general small (Hutton and
Symons 1986). Apart from the large steel plants, hundreds of small iron
metallurgic workshops exist throughout the basin, producing iron houseware
and tools and construction material. They certainly contribute with a significant
Hg load to the basin, but presently there is no data base available to estimate
such a contribution.
211
important landfill of Rio de Janeiro's metropolitan area. The landfill covers an
area of approximately 105 000 m 2 and receives over 105 t of urban wastes per year
(ABES 1983). Nearly all inputs of Hg go to the soil. However, since the landfill is
located along the major tributary of Sepetiba Bay, the Canal de Sao Francisco,
weakly bound forms of Hg can be leached to groundwater or carried out by
surface runoff and reach the adjacent rivers (Behrendt 1993). Inputs of Hg to soils
from this landfill can range from 66 to 198 kg ga -\ contributing with 75 to 90%
of the total Hg inputs to the basin soils, being the most important single source
from this urban sources group.
Plastics and rubber manufacturing and the chemical industry, are a major
industrial activity in the basin employing over 6000 people (Barcellos and
Lacerda 1994). Emissions are mostly to waterways, and account for the third
most important source of Hg to waterbodies in the basin. We use general
emission factors for this industrial category (EPA 1993), which consider Hg as an
accidental component of effluents. However, Hg is frequently used as catalyst in
the production of polyurethane and vinyl chlorine and the Hg emission is
variable, but has not been reported for Sepetiba Bay industrial park. A detailed
survey of the local plastic and chemical industry is advisable since it can
represent a significant Hg source.
Metal manufacturing is the major component of the Sepetiba Bay industrial
park. Many small and medium-sized metallurgic workshops, as well as three
larger plants, employ over 5000 people, producing over 175000 tons of metals
per year, in particular of AI, Zn and Cd. Mercury is a component of liquid and
solid wastes from metallurgical plants and these industries are an important
diffuse source of Hg in the basin. Annual contribution from this sector to water
systems is, however, very small, less than 0.4 kg. Contributions to soils as solid
residues are higher than to waters reaching 18 kg a-I and contributing with 10 to
25% of the total Hg inputs to soils. Compared to other regions, however, metal
production in Sepetiba Bay basin is a relatively small contributor of Hg. The
reason for this is probably the type of ore used by Sepetiba Bay basin plants.
Whereas most ores worked as sources of metals are sulphides, particularly
enriched in Hg, in Sepetiba Bay basin AI, Zn and Cd are produced from oxides,
with very low content of Hg. For example, emission factors from Zn and Cd
production from sulphide ores, range from 8 to 45 g C
I
(Nriagu and Pacyna
1988), which are orders of magnitude higher than the range used in our
estimates, calculated from the use of oxides.
Iron and steel production in Sepetiba Bay basin produces more than 1 million t
per year and is the major source of Hg to the atmosphere, mostly due to the
technology employed (open furnace-electric arc) and the intense use of scrap
metal, particularly enriched in Hg (OECD 1985). Inputs reach 104 kg a-I to the
atmosphere. Contribution to soils and waters from large steel and iron
production facilities may exist but they are in general small (Hutton and
Symons 1986). Apart from the large steel plants, hundreds of small iron
metallurgic workshops exist throughout the basin, producing iron houseware
and tools and construction material. They certainly contribute with a significant
Hg load to the basin, but presently there is no data base available to estimate
such a contribution.