Application of a vegetative cover on phosphogypsum stacks

The treatment of phosphates for the production of phosphoric acid and ferti lisers at Navodari, Romania, has resulted in the production of over 3,000,0 00 m(3) of phosphogypsum, which have been disposed of in three stacks over an. area of 40 ha. An environmental characterisation study followed by a risk assessment analy sis performed on a source-pathway-target basis has shown that phosphogypsum is characterised by residual acidity, elevated concentrations of sulphates , heavy metals and radionuclides and due to the lack of a vegetative cover aerial transportation of fine particles as well as solubilisation and migra tion of heavy and radioactive elements occurs contaminating surrounding soi ls, surface and ground waters. Therefore the application of a remediation s cheme is considered necessary in order to prevent further contamination of the ecosystem in the area. The establishment of a vegetative cover on phosp hogypsum stacks is considered as a viable option for the prevention of futu re environmental impacts. In this paper, the experimental work conducted in order to study the establ ishment of a vegetative cover on phosphogypsum stacks is presented and disc ussed. The major part of this work is focused on the study of glasshouse po t experiments testing a number of herbaceous species and bushes which show tolerance and a potential for growth in such environments. Modification of substrates, in order to increase soil pH, add nutrients in. the system and in general to provide the optimum growth characteristics for the species pl anted, was performed by mixing phosphogypsum tailings with several additive s such as dolomite, kaolin, sewage sludge and clean soil in various modific ations. Preliminary experimental data show that several perennial species a nd bushes tested show an excellent growth potential and can be used for the establishment of an in situ vegetative cover. (C) 1999 Elsevier Science Lt d. All rights reserved.