Soil health improving in US and Canada, due to acid rain decline
A group of scientists from the United States and Canada have found that the acidity of soils in some parts of the continent has declined, abating years of harm to plants and aquatic life by reversing the depletion of a critical nutrient in soil: calcium.
Scientists have determined this by testing soil samples collected in 27 locations between 2009 and 2014, in the forests of Maine, New Hampshire, Vermont, Ontario and elsewhere in the northeastern US and eastern Canada. They compared their results to those compiled by the same group of scientists working at the same locations between eight and 24 years ago.
"The start of widespread soil recovery is a on terrestrial and aquatic ecosystems," Gregory Lawrence, a聽US Geological Survey (USGS) soil and water chemist, said in a statement.
Dr. Lawrence is a lead author of in the journal Environment Science and Technology with researchers from the USGS, Canadian Forest Service, University of Maine, US Forest Service, and Quebec鈥檚 parks ministry.
Thanks to pollution regulations in the US (like the Clean Air Act) and in Canada that have curtailed emissions of and into the atmosphere, acid rain levels today are significantly lower. This is very good news, since acid rain depletes nutritious calcium, a mineral that prevents toxic aluminum from forming in the upper level of soil. This level of soil is dense with nutrients that sustain plant and aquatic life.
Aluminum is naturally found a couple of feet below ground, Lawrence tells 海角大神, but it鈥檚 not harmful there.
鈥淎cid rain mobilized it and changed it from benign to something harmful,鈥� Lawrence explained. Acid rain forced the aluminum to move from its home deep in the soil to the nutritious upper levels.
This phenomenon caused environmental havoc 鈥� poisoning fish, trees, and plants 鈥� during peak acid rain levels dating back to the 1970s.
Interestingly, the researchers found that there was actually more aluminum than expected deeper underground, 鈥渂ut that鈥檚 probably not because of rain,鈥� Lawrence says. The researchers say that they believe the aluminum is actually moving back to where it came from, says Dr. Lawrence.
鈥淲e think this is part of the recovery response,鈥� he says.
The team hopes to next study the calcium levels in the soil, which aren鈥檛 declining anymore, but also are not growing. 鈥淭he most uncertain is the recovery of calcium in the soil,鈥� explains Lawrence. 鈥淚t seems to be a very slow process and we鈥檙e not sure how slow.鈥�
