Ammonium perchlorate

Bioaccumulation: terrestrial

Additional information

Terrestrial bioaccumulation is not a REACH requirement.

Laboratory studies have clearly demonstrated that perchlorate, being a dissociable salt, is readily taken up by most types of plants. The rate of translocation from the soil to the plant, however, varies markedly with the type of plant tested, the concentration of perchlorate in the soil,and, in some cases, the season the plant matter was sampled.

Perchlorate appears to concentrate in plants via a simple "salting out" mechanism.The perchlorate ion is taken up into the plant from soil pore water, translocated to the leaves and/or distal portions of the plant and, through evapotranspiration, is concentrated in the leaves (although seeds typically have a low concentration of perchlorate). This type of mechanism is important from the standpoint of both human and ecological exposures.

Bioconcentration factors, which are simply the ratio of the concentration ofperchlorate in the plant to the concentration in the soil, generally range from 2 to 200 (a few citations report higher bioconcentration factors but those studies includedmore toward aquatic plants or hydroponic testing). Some plants, such as kelp, appear to bioconcentrate perchlorate from natural sources. Others, like tobacco fertilized with Chilean salt peter, appear to accumulate the salt to a much higher degree than other plants tested.

Wild or inedible plants have primarily been sampled from areas with naturally occurring elevated levels of perchlorate (e.g., in the arid areas of the southwestern U.S.), or impacted military sites. Therefore the analytical results reported are most likely biased high rather than representative of a broad range of conditions. With this caveat in mind, the available literature cites concentrations of perchlorate in samples of wild plants (inclusive of grasses, shrubs, succulents and Crees) ranging from below the limit of detection (ND) to 5,500 mg/kg.Most values measured in vegetation, however, are in the low-to-mid parts per billionrange (trees, ND-220 µg/kg; succulent cactus, 66-3,200 µg/kg; desert scrub, 16-900 µg/kg; winter wheat, 720-8,600 µg/kg fresh weight (FW); garden vegetables, 40-1,650 µg/kgFW).

It seems extremely difficult to find a representative way (soil matrix and plant) to address the problem and find a BCF value in terrestrial plants. However, it should be noted that ammonium perchlorate is not emitted in terrestrial soil due to an absence of spread of STP sludge, and would distribute without particular retention in soil as based on Kow (estimated) and the ionic nature meaning a high mobility.