Soil Biodegradation Tests

COMPOST SOIL ERESH WATER MARINE WATER 

T + fungi + bacteria fungi + bacteria bacteria dilute bacteria 

Order of aggressiveness with regard to biodegradation for various environments  

As for aquatic biodegradation, the first standards for soil biodegradation were developed for simple and pure chemical substances, and published as OECD 304 and ISO 11266. For complex samples such as biodegradable polymers, modifications were needed and first introduced by ASTM D5988-96. In 2003, an ISO Norm was also published ISO 17556 - Plastics - Determination of the ultimate aerobic biodegradability in soil by measuring the oxygen demand in a respirometer or the amount of carbon dioxide evolved. 

To improve the reproducibility of the test it is advisable to use a blend of different soils as the texture of the soil is also important. 

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Soil biodegradation tests were done by taking a sandy loam as the source of the soil micro-organisms. All polymer samples were sieved through ASTM sieves and all the samples except poly-e-caprolactone, had a particle diameter between 90 and 53 pm, Poly-e-caprolactone sample was prepared dissolving a commercially... 

Other simple tests include the soil burial test used to demonstrate the biodegradabiUty of polycaprolactone (25), following its disappearance as a function of time, and the clear 2one method which indicates biodegradation by the formation of a clear 2one in an agar medium of the test polymer or plastic as it is consumed (26). The burial test is still used as a confirmatory test method in the real-world environment after quantitative laboratory methods indicate bio degradation. 

Howard PH, S Banerjee (1984) Interpreting results from biodegradability tests of ehemicals in water and soil. Environ Toxicol Chem 3 551-562... 

Soil biodegradation rate constant k = 0.0339 d 1 with t,/2 = 20 d for Kidman sandy loam soil and k = 0.0252 d with t,/2 = 28 d for McLaurin sandy loam soil (Park et al. 1990) t./2 480-672 h, based on aerobic soil die-away test data (Howard et al. 1991). 

PVA films buried in soil were tested after 120 days and showed only very limited signs of biodegradation, and even field tests with PVA sheets buried for 2 years in different natural soil sites showed only limited (10%) weight loss. No traces of colonising microorganisms were detected on the incubated material. Degradable polymers like poly(hydroxy butyrate), PCL or starch are usually extensively... 

Howard, P.H. and S. Banerjee. 1984. Interpreting Results from Biodegradability Tests of Chemicals in Water and Soil. Environ. Toxicol. Chem. 3 551-562. 

Soil t,/2 = 3263-8760 h, based on estimated hydrolysis half-life at pH 9 and 25°C (Mabey et al. 1983 quoted, Howard et al. 1991) and estimated unacclimated aerobic aqueous biodegradation half-life (Howard et al. 1991) and a soil column test in which no biodegradation was observed (Wilson et al 1981 quoted, Howard et al. 1991). 

Biodegradation aerobic t,/2(aq.) = 672-4320 h, based on acclimated aerobic soil screening test data (Tabak et al. 1981 quoted, Howard et al. 1991) anaerobic t,/2(aq.) = 1944-4152 h, based on anaerobic sediment grab sample data (Barrio-Lage et al. 1986 quoted, Howard 1989 Olsen Davis 1990 Howard et al. 1991). 

A model has been developed to describe the vertical transport of low-volatility organic chemicals in soil (Freeman and Schroy 1986). The model was used to make predictions on the transport of 2,3,7,8-TCDD at the Eglin Air Force Base Agent Orange biodegradation test plots (Freeman and Schroy 1986). 

Biodegradation aqueous aerobic biodegradation t,/2 = 48 - 360 h, and aqueous anaerobic biodegradation t,/2 = 192 - 1400 h, both based on grab sample aerobic soil column test data (Fournier Salle 1974 selected, Howard et al. 1991). 

Biodegradation aqueous aerobic t,/2 = 4200-25,920 h, based on unacclimated aerobic soil grab sample data (Castro Yoshida 1971 quoted, Howard et al. 1991 Howard 1991) and reported soil field test data (Kearney et al. 1969 quoted, Howard et al. 1991) t,/2 = 868 d (Nash 1980 quoted, Jury et al. 1983) ... 

Soil burial tests are important in the assessment of the degradation of a range of polymers by the corresponding microflora. They are performed either under field or laboratory conditions with the use of specific strains without the presence of any additional carbon source other than that supplied from the polymer (Whitney, 1996). There are certain drawbacks that should be taken into account, namely the lack of reproducibility due to the climatic conditions and the change of the microbial soil flora when in situ experiments are performed. However, in situ soil burial tests are often the most useful when the extent of biodegradability of a material is sought, especially when combined with tensile strength tests and microscopic examinations (Cain, 1992). 

Batch tests using radiolabeled techniques were employed for both the solubilization and biodegradation tests (33, 52). The soil-water suspensions used... 

Batch leachate samples (24-h short-term test) are tested for various removal, reduction, and retardation (RRR) processes likely to be encountered as runoff moves away from the highway area. For removal, reduction, and retardation (RRR) process tests, soil sorption tests are conducted for both fill and nonfill materials, while volatilization, photolysis, and biodegradation tests are conducted only on non-fill materials that have organic compounds in their leachates. RRR process tests are described briefly in this following section. Detailed procedures for these tests are included in Nelson et al. [4]. The following is a summary of the test procedures. 

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