Liming wetland

Wetland liming. Wetland liming implies a considerably improved duration compared to lake liming, better conditions for biological life, e.g., for chironomid larvae and ephemeroptera in streams and rivers, reduced transport of metals (e.g., Fe, Cu and Al) into the lake, and possibly also reduced the load of Hg and Cs to the lake. The following lime doses in Table 9.4 were applied. 

SjOblom, A., Ilakansson, K. and Allard, B. (2004) River water metal speciation in a mining region — the influence of wetlands, liming, tributaries, and groundwater. Water Air and Soil Pollution, 152(1-4), 173-94. 

Neutralization of acidic water is an important step in reclaiming land that was once mined. Mine run-off renders water around the mine site acidic, and the acid must be neutralized with lime, or calcium oxide (CaO) acting as a base, before the area can be reclaimed. However, this procedure is expensive. Recent studies have shown that constructed wetlands— human-made shallow ponds containing water plants such as cattails—can be an effective and less costly method of neutralizing acid mine drainage. 

To reduce the transport of Hg and Cs from the catchment area into the lake, the measures wetland liming and drainage area liming were tested. 

Wetland liming + selenium (selenium additive according to the Boliden method). 

Fig. 9.3. A. Comparison of how the different remedies (LL=lake liming, WZZ= wetland liming, DAL=drainage area liming, 5e=selenium treatment plus liming and 7F=intensive fishing) influenced the percentage change of Hg-concentration in 7+ perch before time of the introduced remedy (tO-data) and up to 1989...

Wetland liming. About the same results are obtained for the Hg-reduction in perch fry with wetland liming as with lake liming. The most important aspect appears to be not whether use is made of bedrock lime, sedimentary rock lime, "mixed" lime or potash, but how efficiently the remedy is carried out. The Hg-concentration in perch fry can be reduced by about 30% in 2 years. The concentrations in pike may decrease by 15-40% within a further 2-5 years. Wetland liming does not appear to influence lake color or the Hg-transport from land to water to any particular extent (Hakanson et al. 1990a). 

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