Kaisa Vaaramaa

Distribution of 210Pb and 210Po concentrations in wild berries and mushrooms in boreal forest ecosystems.

The activity concentrations and distribution of 210Pb and 210Po in wild berries and edible mushrooms were investigated in Finnish forests. The main study areas were located in Scots pine (Pinus sylvestris L.) forests in southern and northern Finland. The activity concentrations of 210Pb and 210Po in blueberry (Vaccinium myrtillus L.) and lingonberry (Vaccinium vitis-idaea L.) samples decreased in the order: stems>leaves>berries (i.e. fruits). The activity ratios of 210Po/210Pb in the wild berry samples were mainly higher than one, indicating elevated activity concentrations of polonium in the samples. In mushrooms the activity concentrations of 210Pb and especially 210Po were higher than in fruits of the wild berries. The highest activity concentration of 210Pb was detected in Cortinarius armillatus L. (16.2 Bq kg(-1) d.w.) and the lowest in Leccinum vulpinum L. (1.38 Bq kg(-1) d.w.). The 210Po activity concentrations of the whole fruiting bodies ranged from 7.14 Bq kg(-1) d.w. (Russula paludosa L.) to 1174 Bq kg(-1) d.w. (L. vulpinum L.). In general, the highest activity concentrations of 210Po were recorded in boletes. The caps of mushrooms of the Boletaceae family showed higher activity concentrations of 210Po compared to the stipes. In most of the mushrooms analyzed, the activity concentrations of 210Po were higher than those of 210Pb. 210Po and 210Pb dominate the radiation doses received via ingestion of wild berries and mushrooms in northern Finland, while in southern Finland the ingested dose is dominated by 137Cs from the Chernobyl fallout.

Uptake of zinc, nickel, and chromium by N-isopropyl acrylamide polymer gels

Pure N-isopropyl acrylamide (NIPA) polymer gel and NIPA copolymers containing 2-acrylamido-2-methylpropane sulfonic acid (AMPS), 2-acetamidoacrylic acid (AAA), and acrylic acid (AA) were prepared and evaluated with respect to their capability for taking up zinc, nickel, and chromium ions from solutions. AAA-containing NIPA gels were found to take up these metal ions most efficiently. Titration of these gels verified the strong acidic nature of the AMPS–NIPA gel and the weakly acidic nature of the AA–NIPA and AAA–NIPA gels. The ion-exchange capacities, derived from the titration curves, were, however, rather low in all cases. NIPA gels are known to collapse at temperatures about 32°C. This, however, was found to have no effect on the ion-exchange behavior of the gels.

137Cs, 239,240Pu and 241Am in boreal forest soil and their transfer into wild mushrooms and berries

Profiles of podzolic soil from boreal forests were sampled from eight sites in Finland and the distribution of (137)Cs in the soil layers was determined. In addition, (239,240)Pu and (241)Am were determined from two soil profiles taken at one sampling site. Inventories of (137)Cs in the soil profiles varied between 1.7 kBq/m(2) and 42 kBq/m(2), reflecting known variation in (137)Cs fallout from the Chernobyl accident. The highest proportions of the radionuclides were found in the organic layer at a depth of less than 5 cm, which on average contained 47% of (137)Cs, 76% of (239,240)Pu and 79% of (241)Am. In the litter, clearly higher proportions of (137)Cs were found compared to (239,240)Pu and (241)Am, probably indicating its more effective recycling from the organic layer back to the surface. Only very minor proportions of (137)Cs were recorded below 20 cm. The concentration of (137)Cs in the soil profiles could be approximated with a declining logarithmic trend. The activity concentrations of (137)Cs were determined for six wild mushroom species and three wild berry species at two sites, as well as the aggregated transfer factors and the distribution of (137)Cs between their various parts. In addition, (239,240)Pu and (241)Am were determined in one mushroom and three berry species at one site. Very high concentrations of (137)Cs, up to 20 kBq/kg (d.w.), were found in mushrooms, and their transfer factors were between 0.1 m(2)/kg and 1.0 m(2)/kg. In berries, the transfer factors were an order of magnitude lower. (137)Cs accumulated more in the caps of mushrooms and in the fruits of berries than in other parts. Transfer factors for (239,240)Pu and (241)Am were two to three orders of magnitude lower than those of (137)Cs.

Titanium antimonates in various Ti∶Sb ratios: ion exchange properties for radionuclide ions

Ion exchange properties of titanium antimonates have been investigated with the main objective being selective removal of radionuclides from acidic nuclear waste solutions and in the presence of strongly interfering calcium. Five samples with Ti∶Sb ratios between 0.21–4.9 were synthesized by hydrolysis in distilled water under reflux. Products of either a mopungite, rutile or pyrochlore phase crystallized depending on the Ti∶Sb ratio, the order of metal prehydrolysis and the synthesis temperature (20 °C, reflux at ∼100 °C or hydrothermal treatment at 200 °C). The acidity of the exchanger and 85Sr selectivity in acid increases with increasing antimony content, while Sr2+/Na+ exchange is favored as the acidity decreases. The tolerance for Ca2+ in strontium uptake has a reverse trend and the 85Sr/Ca2+ selectivity coefficients (kSr/Ca) increase with the Ti∶Sb ratio from 1.2 to 130 in 0.01 M Ca(NO3)2. In addition to the Ti∶Sb ratio, the crystal phase directs the radionuclide affinity through the ion sieve effect. The pyrochlore structure favors strontium while the rutile phase seems to prefer caesium in acid.

Distribution of 210Pb and 210Po in boreal forest soil.

Vertical distribution and activity contents of (210)Pb and (210)Po were investigated in forest soils of Scots pine-dominated (Pinus sylvestris L.) stands from seven different locations in Finland. The mean total inventory in the soil profile, up to 20cm, of (210)Pb was 4.0kBqm(-2) (range3.1-5.0kBqm(-2)) and (210)Po 5.5kBqm(-2) (range 4.0-7.4kBqm(-2)), the organic soil layer containing 45% of the total inventory of both nuclides. In both the organic and the mineral layers the (210)Po/(210)Pb ratio was close to unity indicating a radioactive equilibrium between them. In the litter layer there was, however, a clear excess of (210)Po suggesting that polonium is recycled via root uptake from the root zone to the ground surface. The activity concentration (Bqkg(-1)) of (210)Pb clearly correlated with organic matter and the Fe, Al and Mn concentrations in soil indicating that radioactive lead is associated both with humic substances and the oxides of iron, aluminium and manganese. Radioactive lead was also seen to follow the behavior of stable lead. No systematic correlation between polonium and soil properties was seen.

Removal of 234,238U, 226Ra, 210Po and 210Pb from drinking water by ion exchange

Six organic and five inorganic ion exchangers were studied for the removal of natural radionuclides from drinking water. In the first phase, distribution coefficients (KD) of uranium and radium were determined in three model solutions: a good quality water, an Fe-Mn-rich water and a saline water simulant. The exchangers showing highest KD´s for U and Ra were tested in column mode experiments for the removal of U, 226Ra, 210Po and 210Pb from a real ground water. Considering the total 1800 processed bed volumes, the best decontamination factors (DF) for U, 20-120, were obtained with the strong base anion exchange resin. The most efficient exchangers for the removal of 226Ra were the weak and strong cation resins and zeolite A. With use of long regeneration intervals, conventional organic resins are thus most suitable for the removal of radionuclides. When only a few hundred bed volumes were processed, with the corresponding regeneration interval about one week, the aminophosphonate resin was most effective for the removal of both uranium and radium. 210Po and 210Pb in ground water were mainly bound in particles and adsorbed on the surface of the anion resins. The use of the aminophosphonate resin to remove uranium and radium would therefore require an anion resin to take up polonium and lead.

Ion exchange of zinc on an aminophosphonate-chelating resin

The distribution coefficient (KD) of trace zinc in 1 M NaCl solution on an aminophosphonate-chelating resin Duolite C467 increased with pH to a peak value close to 200 000 ml/g at pH about 6. At higher pH values the KD dropped to 25 000 ml/g due to competition of zinc hydrolysis. Increasing NaCl concentration up to about 1 M improved zinc uptake on sodium-form Duolite C467 since it prevented exchanger hydrolysis, but at higher concentrations KD decreased somewhat due to Zn2+Na+ competition. Also, increasing zinc concentration, from 6 x 10−7 M to 1 mM, improved zinc uptake, since the exchanger is less hydrolysable in zinc form. EDTA interfered strongly with zinc uptake when present at concentrations higher than 1 μM, sodium cyanide at concentration higher than 1 mM, citrate in concentrations higher than 10 mM while gluconate did not interfere at all.

Effects of pH and uranium concentration on the removal of uranium from drinking water by ion exchange

Effects of pH in the range of 5 to 8 and uranium concentration in the range of 0.02 mg/l to 25 mg/l on the removal of uranium with a strong base anion exchange resin (SBA) and a chelating aminophosphonate resin were studied. The results of the batch and column mode experiments clearly showed that the aminophosphonate resin was an efficient exchanger for the removal of uranium at pH values close to 5 and the SBA resin at higher pH values. In the column experiments, where altogether 2000 bed volumes of drinking water simulant were processed with these exchangers, the uptake of uranium was as high as 99.8% by the aminophosphonate resin at pH 5 and 99.7% by the SBA resin at pH 8.

H+Na+ exchange in an aminophosphonate-chelating resin

Abstract Titration of an aminophosphonate-chelating ion-exchange resin Duolite C467 in hydronium form with 1 M NaOH in 1 M NaCl reflected the diprotic nature of this exchanger. Two inflection points were detected: at pH values 9.3 and about 6.1. Ion-exchange capacity calculated from the second inflection point was 4.80 meq per g of dry hydronium-form resin. Sodium ion uptake exceeded this value by as much as 2.6 meq/g, which is assumed to have been caused by sorption of NaCl electrolyte. Exchange of the less acidic hydronium ion for sodium ion showed a constant corrected selectivity coefficient ( K H ) value of −6.5 (log K H ) in the sodium ion conversion range 50–90%. The corresponding value for the exchange of the more acidic hydronium ion was between −4 and −5 in the sodium ion conversion range 10–50%. Hydrolysis of the sodium-form resin in NaCl solutions does not essentially convert the resin into hydronium form but considerably increases the solution pH.

210Po and 210Pb in Forest Soil and in Wild Berries in Finland

The behaviour of 210Po and 210Pb was investigated in forests in the Southern Finland site and in the Northern Finland site. Sampling sites were in Scots pine (Pinus sylvestris) forests. Maximum activities of 210Po and 210Pb in soil columns were found in organic layers. According to preliminary results of wild berry samples, the lowest 210Po concentrations were found in berries. The highest concentration of 210Po was found in stems of the blueberry (Vaccinium myrtillus) and the lingonberry (Vaccinium vitis‐idaea) samples.