The Baseline - Mining and the Environment: From Ore to Metal - page 382

TABLE 8.10
(Continued)

Parameter Statistical summary Parameter Statistical summary

Nutrients (e.g. nitrite plus nitrate or
total phosphorus)

Seasonal average
Flow-weighted average
Median
Quartiles
Confi dence intervals or standard
deviation

Water clarity/transparency Seasonal average

Seasonal median
Maximum and minimum
Range
Quartiles
Confi dence intervals or standard
deviation

Conductivity Average

Median Quartiles

Bacteria (water contact safety) Geometric mean Quartiles

TABLE 8.11
Graphs and Comparisons to Consider when Assessing Aquatic Data (Minnesota Pollution Control Agency 2003)

Graph Comment

Flow vs. any parameter May show non-point source pollution effects or dilution of dissolved parameters at high fl ows

Date vs. observed values/concentrations May show trends or seasonal variation

Precipitation vs. any parameter May show how parameters respond to rainfall and/or non-point source pollution effects

Parameters vs. numerical standards/criteria May indicate problem areas

Dissolved oxygen and temperature depth profi les May show stratifi cation or mixing status in lakes

Bacteria vs. total suspended solids or turbidity May indicate that bacteria are associated with solids, and reductions in bacteria could be achieved

with technologies that trap solids

Observed values or biometrics vs. river station May show trends by location or points/locations where major changes are noticeable

To assess i ndings, graphs are useful to visually display results. They are also helpful in
comparing parameters. Table 8.11 lists some common forms of graphic data presentation.

Reaching Conclusions

Once data are organized into i ndings, conclusions can be made. Clear presentation of
conclusions is essential to effectively communicate and gain credibility for study results.
In reducing data to usable information, the key is to make only those conclusions that are
supported by the data. One conclusion may be that additional data is needed. Sometimes
conclusions are controversial. This is acceptable providing that controversial conclusions
follow a logical process with scientii c basis, and assumptions are well documented. Often
controversial i ndings and conclusions can be explained by natural conditions, human
alterations, and/or errors in sampling and analysis. Independent professional input always
helps to verify and to understand controversial i ndings and conclusions ( Case 8.10 ).
Various questions help to decide if human alterations or natural conditions affect i nd-
ings and conclusions.

Independent professional input
always helps to verify and to
understand controversial fi ndings
and conclusions.