Environmental Engineering Reference
In-Depth Information
measured in the area. In general, the regional aquifer is aerobic with concentrations
of oxygen between 6 and 10 mg L
−
1
. Nitrate concentrations in the range of the legal
limit (50 mg L
−
1
) were observed in the vicinity of the site, which originate from
intensive fertilization in agriculture. Directly down-gradient of the landfill, anaero-
bic conditions prevail at a width of 150 m with zero concentrations of oxygen and
nitrate. Within this area elevated ammonium concentrations were measured between
10 and 40 mg L
−
1
, which are substantially above the legal limit of 0.5 mg L
−
1
.
Multilevel sampling demonstrated that the whole thickness of the aquifer is con-
taminated by the ammonium plume. Dissolved organic carbon (DOC) was measured
less abundant between 1 and 8 mg L
−
1
and contributes to a minor degree (< 20%)
to oxygen demand compared to NH
4
+
. Groundwater samples also indicate that the
concentrations of other electron donors such as Fe(II) or Mn(II) are negligible.
The groundwater concentrations and total mass fluxes of ammonium from the
landfill were determined by the method of integral pumping tests at two consecu-
tive control planes perpendicular to the flow direction at the site. This method is
especially suited to obtain highly reliable information even for large scale investi-
gations (Bayer-Raich et al.
2004
). The first control plane was installed directly at
the edge of the landfill and the second control plane is approximately 450 m down-
gradient in the groundwater flow direction of the landfill. At the second control
plane much lower concentrations of NH
4
+
were observed. An overview of the site
and two multilevel sampling control planes are given in Fig.
19.14
.
Fig. 19.14
The monitored Natural Attenuation (MNA) reference site “Osterhofen” in SW-
Germany. The municipal landfill is emitting an ammonium plume which is monitored at 2
consecutive control planes (modified from Maier and Grathwohl,
2006
)
Search WWH ::
Custom Search