| dc.description.abstract | Acidification of South West Nova Scotia’s (SWNS) watersheds from acid rain deposition
has led to the depletion of base cations from catchment soils (Clair & Hindar 2005). This has led
to a reduction in the acid neutralizing capacity (ANC) of the catchments, acidification of surface
waters, and the release of aluminum ions (Ali) into surface waters, which can cause deleterious
changes to aquatic ecosystems, and can be particularly harmful to Salmo salar smolts (Clair &
Hindar, 2005). There are decreasing trends in calcium concentration in acidified watersheds as
calcium is released into streams as a result of ion exchange (Clair, 2004). Catchment liming, the
addition of neutralizing compounds such as calcium carbonate (CaCO3), to acidified watersheds
has been demonstrated to be an effective mitigation strategy to assist in the recovery of such
environments (Clair & Hindar, 2005). The application of 30 tonnes of CaCO3 to an acidified
watershed in SWNS in 2012 has been attempted in order to artificially replenish the depleted
base cations from the soil and to mitigate the effects of acid rain deposition.
This research examined, using a mass balance approach, the calcium budget of an
acidified watershed in SWNS. The study addressed the following questions: What were the
annual exports and imports of Ca at the Maria Brook catchment, and were they balanced? And
did catchment liming change the calcium budget of the Maria Brook catchment in SWNS?
Using data from The Canadian Air and Precipitation Monitoring Network (CAPMoN)
and from grab samples of the catchment drainage waters, a pre-liming and post-liming calcium
budget was constructed. A stage-velocity model was constructed to estimate drainage of water
from the system both pre- and post-liming. The nutrient balance was determined from calcium
entering the system through precipitation and leaving the system through drainage water
(Bormann and Linkens, 1967).
It was found that the pre-liming Ca budget was negative, demonstrating that Ca is
continually being depleted from the system and that inputs were insufficient to balance exports.
The application of 30 tonnes of CaCO3 resulted in increased Ca export from the system and
increased stream water Ca concentrations; however these increases only represented a fraction of
the Ca added to the system, suggesting that the remainder was taken up by vegetation or was
stored in the soil pool. It is recommended that further liming applications be conducted and
monitored in order to assess efficacy of catchment liming in remediating the detrimental effects
to aquatic communities (Clair et al., 2004) and in replenishing Ca-depleted soils that potentially
decrease forest productivity (Yanai, 2005). | en_US |
