The degradation of poly[(R,S)-3-hydroxybutyrate], a-PHB, binary blends with natural PHB (n-PHB) and poly(L-lactic acid), PLLA, respectively, has been investigated in soil. In such a natural environment, a-PHB blend component was found to biodegrade. The degradation of a-PHB-containing blends proceeded faster than that of respective plain n-PHB and PLLA. The molecular weight decrease of the n-PHB component was higher, while the same rate of bioerosion of both components was observed for the a-PHB/n-PHB binary blend. For the a-PHB blend with PLLA, the weight loss was accompanied by blend composition changes and the decrease of a-PHB content. However, the PLLA molecular weight decrease was lower in the blend in comparison with the plain PLLA sample. The increase of the number of microorganisms particularly observed for the soil where binary blends were incubated indicates that microbial degradation of a-PHB takes place. The terrestrial plant growth test (cress and barley) demonstrates no environmental toxicity of the materials studied.

Degradacja wybranych syntetycznych poliestrów w warunkach naturalnych Streszczenie-Przedstawiono wyniki badañ degradacji wybranych syntetycznych poliestrów, mianowicie poli(L-laktydu) (PLLA), poli[(DL)-laktydu] (PLA) oraz alifatyczno-aromatycznego kopoliestru kwas tereftalowy/kwas adypinowy/1,4-butanodiol (BTA) w warunkach kompostowania przemy-s³owego, a tak¿e w kompooecie z osadem czynnym, w standaryzowanej glebie i w dynamicznej wodzie morskiej. Przebieg procesu degradacji oeledzono oceniaj¹c zmiany ciê¿aru cz¹steczkowego próbek metod¹ GPC, makroskopowe zmiany ich powierzchni oraz zmiany masy. Stwierdzono, ¿e najwiêksze zmniejszenie ciê¿aru cz¹steczkowego oraz wyraŸna dezintegracja badanych materia³ów polimerowych (zw³aszcza próbki PLA) zachodzi podczas degradacji w warunkach kompostowania przemys³owego. Jest to wiêc w³aoeciwe oerodowisko degradacyjne badanych, podatnych na kompostowanie polimerów, albowiem proces ich degradacji w pozosta³ych oerodowiskach zachodzi znacznie wolniej. Oceniono równie¿ zmiany charakterystycznych w³aoeciwooeci stosowanych oerodowisk w toku trwaj¹cego do 6 miesiêcy procesu degradacji polimerów. Ponadto na podstawie testu fitotoksycznooeci stwierdzono brak jakiegokolwiek niekorzystnego wp³ywu produktów degradacji inkubowanych w glebie próbek PLLA oraz PLA na wzrost i rozwój wysianych w niej nasion rooelin. S³owa kluczowe: polilaktyd, poliestry alifatyczno-aromatyczne, biodegradacja, kompost przemys³owy, standaryzowana gleba, dynamiczna woda morska, kompost z osadem czynnym. DEGRADATION OF SELECTED SYNTHETIC POLYESTERS IN NATURAL CONDITIONS Summary-The results of the study on degradation of selected synthetic polyesters namely poly(L-lactide) (PLLA), poly[(DL)-lactide] (PLA) and aliphatic-aromatic co-polyester terephthalic acid/ adipic acid/1,4-butanediol (BTA) in the industrial compost heap, a compost containing activated sludge, standardized soil or dynamic sea water were presented. The course of degradation process was monitored by evaluation of changes of molecular weights of the samples by GPC method (Fig. 1, 3, 4 and 7), macroscopic changes of the surface (Fig. 2) and weight loss. It has been found that most significant decrease in molecular weight and clear disintegration of the materials investigated (particularly PLA samples) took place during the degradation under the industrial composting conditions. So this is the proper degradation environment for the tested compostable polymers, for their degradation processes in the other environments go much more slowly. The changes in the characteristic properties of the environments used were also evaluated during the process of polymers' degradation up to six-month time (Table 1, 2 and 5). Additionally, on the basis of the results of phytotoxicity test, no harmful effects of the degradation products of PLA and PLLA samples, incubated in the soil, on the growth and development of the plants seeds sown in the soil has been found (Fig. 5 and 6, Table 3 and 4).

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The influence of N, P, K supply on the contents of dry mass, chlorophyll (a+b), vitamin C, saccharides and the activities of peroxidase (E.C.I.ll.I.7), catalase (E.C.I.ll.I.6), and acid phosphatase (E.C.3.1.3.2) in leaves of celery plants during their growth stages was investigated. A correlation between the amount of N, P, K and the chemical composition and catalytic activities of enzymes was found.