Reload Index (ZRiChK UMCS)

 

 

MEASUREMENTS OF 90Sr AND 137Cs RADIOISOTOPES AND HEAVY METAL CONCENTRATIONS IN HERBAL PLANTS APPLIED IN PHARMACY FROM LUBLIN (POLAND) REGION

 

Jan SOLECKI, Marek RESZKA, Stanisław CHIBOWSKI

DEPARTMENT OF RADIOCHEMISTRY AND COLLOID CHEMISTRY

 

 

From dawn of human history a lot of plants that contain chemical substances of specific influence on living beings were used as nutrients and medicine. Contamination of environment by heavy metals and radioactive substances may be dangerous or markedly influence effect of herbal plants.  A special attention should be paid to these elements, which in specific conditions may be substituted by radioactive isotopes, especially - 90Sr and 137Cs. The examination of their concentration in soil and knowledge of soil to plant transfer factor of the respective element is of the great importance as it allows select plant for cultivation on the specific area.

For measurements some soil samples and seventeen species of herbal plants, widely used in pharmacy, were collected from cultivated areas as well as from natural stands in two sites of Lublin region.

Spectrometric analysis of gamma radioactivity of the surface layer (5 cm) of soil samples revealed presence of natural isotopes and their daughters as well as these ones resulting from human activity (nuclear explosions and nuclear power plant failures). In herbal plants samples as for soils, the dominating values for 40K isotope are much higher than for other natural isotopes and depend markedly on the type of the plant as well as kind of collected plant tissue. Higher concentration of cesium was detected in plant tissues exposed to air for longer period of time (twigs or cortex) than for flowers or fruits. Concentration of cesium isotope was used to the calculation of soil to plant transfer factors. These values range from 0.016 to 1,060 and suggest that transportation of cesium depends on the type of plant as well as the type of examined tissues whereas the concentration of he isotope in soil is of smaller importance. Generally, TF values are below 10-2 that proves minute contamination of studied plants by radioactive cesium. Cinquefoil may be regarded as an exception and treated as herb that can accumulate radioactive cesium from the soil.

As mentioned previously, every one plant has some ions that are more eagerly assimilated by root system from soil. In a group of monovalent cations is the most important for the life of plants. In the case of shortage of potassium - cesium may take its place. For this reason concentration of potassium in the soil may markedly influence the transfer of cesium by root system to plant tissues. It may be noticed that the lower absolute values of Kd the smaller transfer of cesium to the plant. The much higher Kd factor was calculated for cinquefoil, which confirms it plant as cesium concentrating plant.

The concentration of strontium ranged from 0.004 to 1.808 Bq/kg. data, revealing that fruits and flowers cumulate less isotope of 90Sr than leaves or cortex. A reason for such behavior may come from different way of nourishment of specific plant. Calculated soil to plant transfer factors of 90Sr isotope ranged from 0.296 to 0.611 that proves no accumulation of 90Sr in examined herbal plants (TF<1). Appreciable differences may result from type of species as well as radioactivity contents in the soil. As can be seen, accumulation of strontium is usually ten times higher than cesium except cinquefoil. To clear such behavior concentrations of selected cations were determined in soil and herbal plant samples by ED-XRF method. Calcium ions are competitive towards strontium ones, but consideration of obtained do not reveal influence of stable calcium on the concentration of radioactive 90Sr in studied samples of herbal plants. One can see that examined samples contain considerable amounts of potassium and calcium and smaller amounts of magnesium. In all samples stable strontium was detected that confirms higher affinity of the plants for 90Sr than 137Cs accumulation. In all examined samples, heavy metal ions such as Zn, Rb and Pb were detected with varied concentrations that were characteristic for particular species.

 

Table 1. Radioactivity of 90Sr and 137Cs in herbal plants.

No

Herbal plant

Radioactivityof 90Sr [Bq/kg]

Radioactivity of 137Cs [Bq/kg]

leaves

1

sage

0.192

0.428

2

plantain

0.383

0.245

3

cetyna

0.195

9.853

4

wild pansy

0.366

0.635

5

marsh mallow

0.077

0.087

6

melissa

0.197

0.679

7

cinquefoil

0.135

5.549

8

field horsetail

0.209

<0.146

flower

9

wild camomile

0.050

0.670

10

linden

0.073

0.777

11

horse-hesnut

0.004

0.246

fruit

12

elder

0.092

0.053

13

black currant

0.028

<0.085

14

rowan-berry

0.155

<0.116

15

raspberry

0.043

<0.148

16

gooseberry

0.014

0.531

cortex

17

alder buckhorn

1.808

3.435