Issue 3 [November]

Stabilization/solidification (S/S) processes were utilized to immobilize lead (Pb) and tungsten
(W) in contaminated soils, the inclusion of W motivated by the use of the new W-based
ammunition. Artificially contaminated soils were prepared by mixing either kaolinite or
montmorillonite with 10% Pb and 1% W (all percentages by dry weight). Type I/II Portland
cement (PC), silica fume cement (SFC) and cement kiln dust (CKD) were used as S/S agents.
The S/S agents were added at 5, 10 and 15 % for a curing time of 1-, 7- and 28-days. The
toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching
procedure (SPLP) were used to evaluate the effectiveness of the treatments. X-ray powder
diffraction (XRPD) was used to investigate the crystalline mineral phases responsible for Pb
and W immobilization. The TCLP results showed that regardless of clay type and stabilizing
agents, the Pb concentrations decreased with increasing pozzolan content. PC and SFC
exhibited similar performance depending on the particular sample (not consistent with soil
type, dosage, and curing time). The most effective stabilizing agent on Pb leachability was PC
despite SFC being silica-enriched which should have contributed to its greater immobilization
of Pb. TCLP-W was immobilized below 1 mg l-1 in every case. The most effective stabilizing
agent on the SPLP-Pb leachability was CKD, consistently demonstrating among the lowest
concentrations for each soil type due to pH control. PC and SFC exhibited similar
performance depending on the particular sample (not consistent with soil type, dosage, and
curing time). The W concentrations in SPLP leachate were very low in most samples
indicating that W could be immobilized upon S/S processes even though W solubility is very
high at elevated pH conditions (662.9 mg l-1 at pH~11), and would remain immobilized under
SPLP exposure conditions. The XRPD results revealed that the formation of lead silicate
(Pb4SiO6), stolzite (PbWO4) and lead tungsten oxide (Pb0.29WO3) were strongly associated
with the immobilization of Pb in the S/S matrix.

The importance of the development and application of groundwater simulation mathematical
models in the protection of aquifer systems is nowadays recognised as an undisputable fact.
In this paper a mathematical model that was developed in order to simulate the operation of
the Upper Anthemountas aquifer in Chalkidiki, Greece, is presented. The case study
application investigated concerned the possible malfunction of the Waste Water Treatment
Plant located within the study area. According to this scenario a possible malfunction of the
treatment plant could pollute the underlying aquifer. A network of observation wells located
downstream of the plant could detect the pollution and predict the time needed to reach the
productive wells surrounding the area. This allows the local water resources managers to
formulate a priori action-plans including, the alteration of the pumping schedule in order to
prevent polluted water to be abstracted from the nearby wells and at the same time protect
the public health, along with necessary measures concerning the prevention of further
pollution and the restoration of the groundwater aquifer system.

Tungsten in solution may exist as a wide variety of species depending on concentration, pH,
and aging time. Despite a substantial number of studies on this topic, the speciation of
tungsten in aqueous solutions is still not completely understood. To address issues of fate,
transport and potential bioavailability, it is necessary to be able to assess the speciation of
tungsten in environmental systems. This study investigates the use of Laser
Desorption/Ionization mass spectrometry combined with a Time-of-Flight mass analyzer (LDITOF)
as well as Raman spectroscopy as potential techniques in speciation studies. Raman
spectroscopy has been successful in identifying the dominant species under a narrow range
of conditions. The ultimate goal is to extend the range of conditions and concentrations while
also identifying subordinate species.

A mathematical model to simulate microbial growth and lag time is proposed in the present
work in accordance with Sengor et al. (2009). The model is verified experimentally for a mixed
microbial culture growing at metal free and at Cr(III) or Cr(VI) contaminated environments.
The model is further verified using a monoculture of Pseudomonas sp. growing at metal free
and Zn(II) contaminated environment. The effect of temperature on microbial growth and lag
is also simulated by the model. The simulation results show for the mixed culture that growth
rate decrease with parallel increase in lag time, with the rise of either Cr(III) or Cr(VI)
concentration. For Pseudomonas sp., the simulation indicated that there is almost nil lag time
for growth at 35 ºC, while approximately 10 h lag time is calculated for growth at ambient
temperature (20 ºC). The lag time increases by approximately 6 more hours when 0.01 mM
Zn(II) is added in the growth medium (at ambient temperature). The increase of lag time with
temperature reduction is explained by the fact that the biochemical reactions are slowed down
at lower temperatures. A good correlation between model predictions and simulation results is
observed.