The Direct Effects of Simulated Acid Rain (SAR) - 2018 Experiment

Greenhouse set up in 2018

Overview: This greenhouse-based experiment examines the direct foliar effects of acute, short-term exposure to simulated acid rain (SAR) on seedlings of three domesticated plant species: sunflower, radish, and clover. The photo above shows the typical arrangement of plants during the experiment. At least once during the treatment phase the treatment groups are shifted between tables and the pots randomized to some extent. Simulated acid rain of pH 3.5 and pH 2 (tapwater acidified with a 2:1 molar ratio of sulfuric:nitric acids) is sprayed onto the above-soil foliage of 10 day old seedlings once daily to completely wet the foliage and moisten the soil surface for a total of 19 daily applications in 2018. The controls are similarly treated with plain tap water (typically ~pH 6.8-7.4). The seedlings are also watered once daily with tapwater either several hours before or after treatment application.There are 16 replicates (pots of seedlings) per species per treatment group in 2018. Upon completion of the treatment phase, the plants are measured for leaf area, chlorophyll content, dry biomass per plant, the proportion of plants that exhibit any damage (dead cells, lesions, spotting, etc.), and the percent leaf area exhibiting damage. Leaf wettability is examined by placing water drops on the leaves to observe retention and drop shape (contact angle). Leaf samples are also prepared and viewed using a scanning electron microscope to document microscale effects on tissues, surface structures, and epicuticular wax.

(SEM photo gallery from the 2017 and 2018 experiments)

Seedling Establishment 2018 (2/9/18 - Day 10)


Day 10 of SAR Applications 2-19-2018








 Day 20 SAR applications (3-11-18)






Droplet formation images (from 2009 experiment)



(SEM photo gallery from the 2017 and 2018 experiments)


Following are detail shots of the typical physical effects of the acid treatment on the pH 2 plants. These photos are from various years, but typify direct effects we see routinely in this experiment.


pH 2 sunflower with true leaf petiole
growing from cotyledon position on stem
Abnormal leaf development in sunflowers. These were seen in pH 3.5 and control.

Same as above.
Sunflower pH 2 stem lesions day 19.

 SEM acid burn

Scanning electron micrograph of acid burn on a sunflower leaf treated with pH 2 simulated acid rain.


2018 Bates College
Modified on 3-26-2018 GA