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C2TN

A NORM CASE STUDY: THE WILD VEGETATION ON THE PHOSPHOGYPSUM STOCKPILE FROM A DISABLED PHOSPHATE FACTORY IN BARREIRO (PORTUGAL)

 

Vegetation component

Type of sample

235U

226Ra

210Pb

228Ra

40K

Plantago sp.

PG Substrate

13±10

740±41

870±130

n.d.

93±43

Roots

n.d.

140±10

260±41

3.6±2.0

280±37

Aerial parts

n.d.

110±5

92±14

n.d.

351±33

Bryum sp.

PG substrate

18±4

890±37

1000±132

8.9±1.0

38±12

Moss tissues

66±14

2900±200

4000±660

36±9

n.d.

 

Availability of natural radionuclides, rare earth elements (REEs) and heavy metals in a phosphogypsum (PG) stockpile remaining as the legacy of a disabled phosphate plant in the city of Barreiro, was evaluated by analyzing the transfer to rooted plants (Plantago sp.) and mosses (Bryum sp.) growing naturally on the PG stockpile. Mosses content in 226Ra and 210Pb reached concentrations several fold higher in biomass than in the PG substrate. In rooted plants, concentrations were less than one order of magnitude lower than in moss (Table), but two orders of magnitude higher than those measured in grasses from natural soils. Only 1.6% of 226Ra in the PG matrix is bioavailable, meaning that it is strongly bounded in a crystalline matrix and just a small amount is in an ion-exchangeable form. High concentrations of heavy metals (As, Cd, Zn, W) in plants and mosses are an evidence of their transport from former industrial facilities and present even more important risk to the public health and the environment than natural radionuclides and REEs from the PG stockpile.