Environmental Engineering Reference
In-Depth Information
50
40
30
20
10
0 cm
Fig. 7.11 Illustration showing placement of mylar grid around a 15 cm portion of an IRIS tube.
By marking and counting sectors where paint has been removed, paint removal can be easily
quantified (Modified from Rabenhorst
2012
with kind permission of
The Soil Science Society of
©
America, Inc. 2012. All Rights Reserved)
that occurs somewhere within the upper 30 cm of the soil.
4
Therefore each group
must determine which 15 cm zone within the upper 30 cm of each IRIS tube shows
the maximum paint removal, and quantification should proceed for this zone.
4. A clear mylar grid should be wrapped around that portion of each IRIS tube
showing the greatest degree of paint removal and should be secured using rubber
bands. Using a fine point permanent marker, each sector with greater than 50 %
paint removal should be marked. Once all the sectors are marked, the sectors
should be counted and the percentage of the area can be calculated.
Part 3: Comparison of IRIS Data with Eh, pH and
d Data
αα
1. Using Eh and pH data collected and plotted on an Eh-pH stability diagram you
should be able to evaluate whether the soil is reducing (or at what depths, the soil
is reducing).
2. Based on the data you have collected, you now have 3 independent assessments
of whether the soil is reducing: (1) Eh-pH; (2)
d; (3) IRIS tubes.
3. Provide a thorough discussion of your data, being sure to include:
αα
• A summary of whether or not the soil was reducing according to each of the
three assessment tools;
• How results from each of these assessment methods were similar to or
different from the others;
• What factors might account for any differences that you observed; and
• Your own conclusions (based upon your data) regarding whether or not the
soil is reducing. Note that according to the Technical Standard of the NTCHS,
in order for a soil to be reducing, it must meet the reducing specifications of
one of the three methods, within the zone of 0-30 cm for a period of 14 days.
For Eh and IRIS, a majority of the instruments (three-fifth) must fall within
the specified range (not the mean).
4
Other work has suggested that 20 % removal from a 10 cm zone somewhere within the upper
30 cm might be a better assessment of reducing conditions in soils (Castenson and Rabenhorst
2006
; Rabenhorst
2008
).
