In-situ immobilization of arsenic in the subsurface on an anthropogenic contaminated site - In-Situ Remediation of Arsenic-Contaminated Sites - page 141

CHAPTER 7

In-situ immobilization of arsenic in the subsurface
on an anthropogenic contaminated site

Timo Krüger, Hartmut M. Holländer, Jens Stummeyer, Bodo Harazim,
Peter-W. Boochs & Max Billib

7.1 ARSENIC IN CHEMICAL WARFARE AGENTS

Due to its natural toxicity arsenic (As) has been used in many chemical warfare agents (CWA)
during World War (WW) I and II. These CWA are on a cellular level more toxic than pure arsenic
(Henriksson et al ., 1996). CWA were used during WW I in combat and were merely produced
during WW II. These compounds are persistent to these days in soil and groundwater (Haas et al .,
1998). Decomposition products which are mainly analyzed in present groundwater are phenylar-
sonic acid, phenylarsine oxide and diphenylarsinic acid (Daus et al ., 2008). These decomposition
products mostly do not exhibit the high toxicity of the original compounds (Schneider et al .,
2005). As containing substances were predominantly used in so-called “Blue Cross” CWA. The
name is derived from the fact that substances with low volatility and high irritation potential were
marked with a blue cross or ring (Martinetz, 1993). “Blue Cross” CWA containing As are e.g.,
adamsite, arsenic trichloride and Clark I.
In 1996, it was suspected that over 3200 military sites have been contaminated in the Federal
Republic of Germany (Thieme, 1996). However, CWA were produced at 27 sites and had possibly
been used at 132 filler points for explosives. Additionally, CWA have possibly been handled at
decommissioning points inclusive blasting and burning areas (overall 480) as well as testing sites
(45), ammunition factories and storages (Thieme, 1996). The necessity to remediate or at least
secure the contaminated sites results from the toxicity of these compounds.
We developed and tested an in-situ technique for the immobilization of organic and inorganic
arsenic compounds based on the subterranean deferrification and demanganesation under addition
of dissolved iron which has been studied at laboratory scale before (Holländer et al ., 2008;
Krüger et al ., 2008).

7.2 SITE DESCRIPTION

The groundwater at the investigated military site in Northern Germany is contaminated with As
containing CWA. Other contaminants are NAPL, explosives and decomposition products of sul-
furous CWA. More detailed information on the CWA is missing based on the poor documentation.
The total As-concentrations (t-As) in the groundwater at the site as measured in 2005 ranges from
0.03 mg L − 1 to 9.05 mg L − 1 with arithmetic mean concentration of 2.38 mg L − 1 and a median
concentration of 0.98 mg L − 1 (Holländer et al ., 2008). The center of the plume started near the
surface (StO-01, Fig. 7.1 ) at one potential source of the As-contamination and lowers its depth
with increasing length along the groundwater flow path. We observed the central part of the
plume down to 40 m below surface along a flow length of about 130 m in this study. However, it
is expected that the plume does further outreach since the observed t-As-concentration at StO-04
is still 2.40 mg L − 1 . t-As is predominantly organically bound As (org-As) and thus mainly occurs
in the form of phenylized As compounds. However, we were not able to distinguish the species of

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