| patrickve |
26 januari 2012 21:07 |
Ok, heb wat huiswerk gemaakt, en Ars, ge hebt gelijk, zeolieten kunnen inderdaad cesium gevangen houden:
Citaat:
CESIUM, RADIOACTIVE
CASRN: NO CAS RN
This record contains information on the radiological aspects of cesium and its compounds. For information on the general toxicity and environmental fate of cesium ions and cesium compounds, refer to the CESIUM COMPOUNDS record. For general toxicological, safety and handling, and environmental information on ionizing radiation emitted from chemical sources including cesium, refer to the IONIZING RADIATION record.
This record does not address regulatory or licensing requirements that may be imposed by state, local or federal authorities.
For other data, click on the Table of Contents
Soil Adsorption/Mobility:
In soil, cesium has low mobility and usually does not migrate below a depth of 40 cm. The majority of cesium ions are retained in the upper 20 cm of the soil surface(1-3). For example, vertical migration patterns of cesium-137 in four agricultural soils from southern Chile indicated that approx 90% of the applied cesium was retained in the top 40 cm of soil(4). In one soil, essentially 100% was bound in the upper 10 cm(4). Migration rates of radiocesium were derived from depth distribution profiles and were in the range of 0.11 to 0.29 cm/yr(4). No correlations were observed for other soil properties such as pH, water content, cation exchange capacity, and exchangeable calcium. Other studies report that clay and zeolite minerals strongly bind cesium cations and therefore reduce the bioavailability of cesium and the uptake in plants by irreversibly binding cesium in interlayer positions of the clay particles(5). Experiments conducted by growing plants in a peat soil showed that the introduction of zeolites into the soil-plant system decreased the uptake of cesium-134 in plants by a factor of eight(6). The low hydration energy of cesium cations is primarily responsible for their selective sorption and fixation by clays and zeolites(7). Soils rich in organic matter adsorb cesium(8). However, the cesium adsorbed in the organic fraction is readily exchangeable and highly available for plant uptake(8). Regions in Venezuela, Brazil, and Russia where the soils are peaty or podzolic, the mobility of cesium is considerably greater than in other soils(9,10).
[(1) Korobova E et al; Appl Geochem 13: 803-4 (1998) (2) Ruse ME, Peart MR; Chemosphere 41: 45-51 (2000) (3) Takenaka C et al; Sci Total Environ 222: 193-9 (1998) (4) Schuller P et al; Sci Total Environ 193: 197-205 (1997) (5) Paasikallio A; Plant Soil 206: 213-2 (1999) (6) Shenber MA, Johanson KJ; Sci Total Environ 113: 287-95 (1992) (7) Hakem N et al; pp. 652-7 in Conf. Proc. - Inter Containment Tech Conf Exhib, 9-12 Feb, 1997. St. Petersburg, FL. Springfield, VA: Natl Tech Info Srv NTIS DE98001967 (1997) (8) Sanchez Al et al; Environ Sci Technol 33: 2722-57 (1999) (9) LaBrecque JL, Rosales PA; J Trace Microprobe Tech 14: 213-21 (1996) (10) WHO; Selected radionuclides: Tritium, carbon-14, krypton-85, strontium-90, iodine, cesium-137, radon, plutonium. Environmental Health Criteria 25. Geneva, Switzerland: World Health Organization (1983)] **PEER REVIEWED**
Levels of cesium-134 and cesium-137 were monitored for accumulation and vertical migration from May, 1986 until November 1987 in the podzoic Parabrown earth soil of the Hoeglwald spruce forest situated between Munich and Augsburg, Germany following the Chernobyl accident in 1986(1). Residence half-times of 90 days for the time period of 1-130 days and 230 days for the time period of 130-600 days after the passage of the radioactive plume mere measured for the combined isotopes(1).
[(1) Bunzyl K et al; Z Pflanzenernaehr Bodenk 152: 39-44 (1989)] **PEER REVIEWED**
The vertical migration patterns of cesium-137 produced from the atomic bomb that exploded in Nagasaki, Japan were studied over a 40-year period(1). Over this period, 95% of the cesium remained in the top 10 cm of the soil surface and no cesium was detected below a depth of 40 cm(1). The migration rate of cesim-137 was 0.10 cm/yr(1). Cesium-137 had the largest median distribution coefficient (Kd) of five radionuclides (manganese-54, cobalt-60, zinc-65, strontium-85, and cesium-137), and a positive correlation was observed between the adsorption coefficient and exchangeable potassium content in soil(2). In all 25 soil and sediment samples collected from a variety of contrasting locations in the Esk estuary on the Cumbrian coast in the United Kingdom (10 km south of the British Nuclear Fuels Ltd plant at Sellafield) in May 1990, >50% of cesium-137 appeared to be firmly bound within a residual phase(3). Four sediment samples (cesium-137 concentrations ranging from 1470 to 5680 kBq/kg)collected from Reservoir 10 in the Techa river near the Mayak Production Association in the Urals mountains were tested to determine the remobilization of cesium-137 using freshwater and seawater extractions(4). The total apparent distribution coefficient (Kd) values of cesium-137 in the four samples in a sediment-freshwater system ranged from 4,100 to 156,000 ml/g. In the seawater sediment system, the mean apparent Kd values decreased by 94% and remobilization in seawater was 5% of total activities (i.e. releases of 165 kBq/kg dry weight) for cesium-137(4).
[(1) Mahara Y; J Environ Qual 22: 722-30 (1993) (2) Yasuda H et al; Water Air Soil Pollut 83: 85-96 (1995) (3) Davies KS, Shaw G; Sci Total Environ 132: 71- 92 (1993) (4) Standring WJF et al; Environ Sci Technol 36: 2330-7 (2002)] **PEER REVIEWED**
Cesium-137 and cesium-134 are firmly bound to clay mineral particles in river or lake sediments(1).
[(1) Sawidis T; Arch Environ Contam Toxicol 30: 100-6 (1996)] **PEER REVIEWED**
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(van http://toxnet.nlm.nih.gov/cgi-bin/si...m,+radioactive ) |
