Acid rain: Rain containing acids that form when compounds - released into the atmosphere from the burning of fossil fuels, agricultural practices and other human activities -combine with water. Rain that has not been affected by these factors generally has a slightly acidic pH of ~ 5.6, while acid rain has a lower pH. For example, at the HBEF rain [..]

Deposition that is acidic.

Precipitation that is acidic. Acid rain is a type of acid precipitation.

The accumulation of gases, liquids, or solutes on the surface of a solid or liquid. At the HBEF scientists often examine how different compounds in the soil (e.g., nitrate) adsorb, or attach, to soil particles.

Food material reaching an aquatic community in the form of organic detritus.

This is the process in which organic forms of nitrogen (e.g., nitrogen present in dead plant material compounds) are converted to ammonium (NH4+) by decomposers (bacteria).

Negatively charged ions such as nitrate (NO3-) or chloride (Cl-).

No oxygen present.

Soils that have low levels of base cations such as magnesium, sodium, potassium, and calcium.

(in terms of HB research): Acid rain has caused the leaching of calcium, a natural component of HBEF soils very important to plant growth, from forest soils over the past several decades. In 1999 an experiment started in which calcium was added to an entire watershed in an effort to restore soil calcium pools to pre-acid rain levels and study the c [..]