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Environmental fate & pathways

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Monitoring was performed both at manufacture site and main industrial user site in continental Europe. Several parameters were monitored:

-         Release flow rate

-         River flow rate

-         Concentration of Perchlorate ion in release

-         Concentration of Perchlorate ion in the river

Concentrations of Perchlorate ion in water were measured by Ion chromatography according to EPA Method 314.2.


Manufacture site (Year 2014):

-         Release flow rate, 90thpercentile : 7462 m3/day

-         River flow rate, 10thpercentile : 4.13E+ 6 m3/day

-         Quantity of Perchlorate ion released, 90thpercentile : 0.196 kg/day

-         Concentration of Perchlorate ion in the river, 90thpercentile : 1.5 µg/L


Main industrial user site (Year 2014):

-         Release flow rate, 90thpercentile : 142.5 m3/day

-         River flow rate, 10thpercentile : 5.52E+ 5 m3/day

-         Quantity of Perchlorate ion released, 90thpercentile : 0.029 kg/day

-         Concentration of Perchlorate ion in the river, 90thpercentile : 27 µg/L

Another study performed in six sites throughout the United States are available. The sites were chosen to include diverse soil types and climatic conditions. Because perchlorate is very soluble in water, its concentrations are highest in sediments near specific releases, but decline rapidly with increasing distance from the source. Perchlorate also degrades rapidly in anaerobic sediments, provided sufficient substrate availability and lower concentrations of competing anions such as sulfate and nitrate.

The following case studies illustrate aquatic exposures resulting from known perchlorate releases.

Case study: Kerr-McGee/PEPCON, Henderson, Nevada:

Sediment samples from the Las Vegas Wash have contained perchlorate at concentrations as high as 56 mg/kg. However this concentration decreased rapidly with distance from the source area as a result of dilution of perchlorate plume by the waters of Las Vegas Wash and Lake Mead. Downstream near Lake Mead, researchers found perchlorate in sediment at concentrations as high as 0.081 mg/kg.

Case study: Naval surface warfare center, Indian head, Maryland:

Parsons Engineering Science, Inc., Scientific and technical report for perchlorate biotransport investigation: a study of perchlorate occurence in selected ecosystems, Interim final, Austin, TX, Contract no. F41624 -95 -D-9018, 2001: Parsons sampled 6 locations downstream from one area of the site, the Low Vulnerability Ordnance Area (LVOA), in the Town Gut Marsh System. Sediments at the three most upstream location contained detectable perchlorate, at concentrations ranging from 0.004 to 0.318 mg/kg. Perchlorate was not detected in the three further locations furthest downstream.

Accumulation of perchlorate in aquatic and terrestrial plants at a field scale, J. Environ. Qual., 33, 1638 -1646, 2004: Tan et al, Looked at 4 sample locations at the Naval Weapons Industrial Reserve Plant (NWIRP) where sediments had been either intermittently or continuously exposed to perchlorate in suface water. The intermittently exposed stream segments were downstream of hte continuously exposed stream segments, and Tan et al. suggested that some of the lower perchlorate concentrations in the intermittently exposed streams were attribuable to bacterial activity in wetland habitats. The team analyzed perchlorate concentrations in surface water, smartweed and watercress.

Subsequently, Tan et al. examined the potential for anaerobic degradation of perchlorate at these four sample locations. Their laboratory mesocosm experiments showed that bacteria in anaerobic sediments can degrade perchlorate, although high concentrations of nitrate may affect degradation. (Degradation kinetics of perchlorate in sediments and soils, Water, Air, and Soil Pollution, 151, 245 -259, 2005)

Tan et al then looked at hte temporal and spatial variation of perchlorate in streamed sediments at NWIRP. The researchers suggested that plant growth may contribute organic substrate for perchlorate degradation, and plant uptake may also have contributed to perchlorate removal from sediments. Overall tan et al. concluded that the sediments were able to degrade perchlorate concentrations within the top 30 cm. (Temporal and spatial variation of perchlorate in streamed sediments: results from in-situ dialysis samplers, Environmental Pollution, 136, 283 -291, 2005)

As these case studies show, perchlorate does not accumulate or persist in sediments due to its solubility and microbial degradation under the proper anaerobic conditions. Therefore, if the source of perchlorate is surface water, then sediment contamination may not be as important an issue as it might be.

Although a careful review of the literature shows a few sites where the maximum value of perchlorate in soil exceeds 1500 mg/kg, it may be misleading to focus on the highest detected concentrations because soil contamination at many sites tends to spatially distribute in clusters or hot-spots, for instance those located in and around targets used at military ranges. The frequency distribution of perchlorate concentrations, like most chemicals in soil at hazardous waste sites is therefore log normal and heavily skewed to the left, meaning the majority of soil analyses would be observed below the detection limit. As a consequence, most terrestrial animals inhabiting a site, due to the selective nature of foraging activity are anticipated to be exposed to, on average, lower soil levels than the maximum values which are measured.

Case study: Massachusetts Military Reservation (MMR), Cape Cod, Massachusetts

Less than 10% of the soil samples (216 out of 2500) at MMR contained detectable perchlorate (range was 0.0012 to 27 mg/kg, with a median and mean concentration of 0.0021 and 0.252 mg/kg, respectively). A careful review of the literature shows that most of soil samples at hazardous waste sites (that have a known history of exposure to perchlorate) are less than 20 mg/kg.

Alsop et al. (Assessing alternate approaches to estimating uptake of compounds by plants and animals in ecological risk assessments, The 19th annuam international conference on soils, sediments and water, University of Massachusetts, Amherst, October 20 -23, 2003) studied perchlorate uptake by plants and small mammals in one area at MMR. Soil in the study area contained perchlorate concentrations that ranged from non-detect to a maximum concentration of 27 µg/kg. They reported that perchlorate was taken up by plants and the perchlorate concentrations ranged between non-detect to 140 µg/kg. Perchlorate was not detected in earthworms exposed to perchlorate containing soil. Perchlorate was not detected in mice or voles collected from the study area but it was detected in a single shrew sample at 140 µg/kg.