Distribution, Bioavailability and Speciation of Mercury
2
Material and Methods
2.1
Field Sampling
2.1.1
Soil
183
The sampling areas were subdivided according to site and site use (ornamental
and vegetable gardens, public and private lawns, playgrounds), soil samples were
recovered by means of a cylindrical steel drill down to a maximum depth of 30
cm applying a 1 x 2 or 1 x 1 m grid. Individual samples were filled into brown
glass bottles (250 ml) or mixed on site as composite samples in order to obtain a
representative of that site (cf. Anonymous 1993a). Pre-treatment of the samples,
such as homogenization and separation of partial samples for determination of
dry weight, were carried out in the laboratory.
In order to determine the vertical contaminant distribution and to laterally
delineate the original Hg release areas, exploratory borings were established to a
maximum depth of 6 m, applying a decreasing diameter of 80 to 36 mm to avoid
cross-contamination.
2.1.2
Groundwater
In the course of several investigation phases, 6" groundwater monitoring wells
were installed which fully penetrate the shallow groundwater down to the base of
the aquifer. After purging the wells, the groundwater was sampled by means of a
submersible pump via a Teflon hose as rising main.
Sampling was carried out after the conductivity readings of the recovered
water stabilized and the water column in the well was exchanged more than three
times. The water samples for total Hg determination were stabilized by adding
HN0 3 (sample pH < 2) and 0.05% K2 Cr2 0 r In the case of analysis for the various
fractions, no reagent was added.
2.2
Analytical Procedures
2.2.1
Total Mercury
Total Hg contents was determined by cold vapour atomic absorption spectroscopy (CVAAS) after digestion of the samples in aqua regia at 160°C for 3 h (DIN
38414 S7, DIN 38406 El2).
2
Material and Methods
2.1
Field Sampling
2.1.1
Soil
183
The sampling areas were subdivided according to site and site use (ornamental
and vegetable gardens, public and private lawns, playgrounds), soil samples were
recovered by means of a cylindrical steel drill down to a maximum depth of 30
cm applying a 1 x 2 or 1 x 1 m grid. Individual samples were filled into brown
glass bottles (250 ml) or mixed on site as composite samples in order to obtain a
representative of that site (cf. Anonymous 1993a). Pre-treatment of the samples,
such as homogenization and separation of partial samples for determination of
dry weight, were carried out in the laboratory.
In order to determine the vertical contaminant distribution and to laterally
delineate the original Hg release areas, exploratory borings were established to a
maximum depth of 6 m, applying a decreasing diameter of 80 to 36 mm to avoid
cross-contamination.
2.1.2
Groundwater
In the course of several investigation phases, 6" groundwater monitoring wells
were installed which fully penetrate the shallow groundwater down to the base of
the aquifer. After purging the wells, the groundwater was sampled by means of a
submersible pump via a Teflon hose as rising main.
Sampling was carried out after the conductivity readings of the recovered
water stabilized and the water column in the well was exchanged more than three
times. The water samples for total Hg determination were stabilized by adding
HN0 3 (sample pH < 2) and 0.05% K2 Cr2 0 r In the case of analysis for the various
fractions, no reagent was added.
2.2
Analytical Procedures
2.2.1
Total Mercury
Total Hg contents was determined by cold vapour atomic absorption spectroscopy (CVAAS) after digestion of the samples in aqua regia at 160°C for 3 h (DIN
38414 S7, DIN 38406 El2).