Litter simulation

Non-exposed 1 Month 2 Months 5 Months Ultimate elongation (per cent) 

In a litter simulation test in New Jersey, USA, the wintertime outdoor disintegration of E/CO sheeting and other common multican packaging materials were compared by Harlan [11]. Both plastic and paper materials were included. The results are shown in Table 8.5. The E/CO (2.7% CO) lost nearly all elongation within a month, embrittled within two months and broke up and blew away in five months. 

Recycling of degradable plastics is a topic of debate within the plastics industry. Studies have shown that no deleterious effects on tensile strength or ultimate elongation were observed from the addition of 20 weight percent 

the presence of E/CO copolymers in the recycle stream should not be a deterrent to recycling of plastics. 

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A. P. Whitmore, E. Handayanto, Simulating the mineralization of N from crop residues in relation to residue quality. Driven by Nature—Plant Litter Quality and Decomposition (G. Cadish and K. E. Giller, eds.), CAB International, Wallingford, 1997, p. 337. 

Sophisticated decomposition models are being developed. A simulation model developed by Bunnell and Dowding for tundra sites is a nine-compartment model with 23 transfers between compartments. This type of model may provide the only method for understanding the extremely complex litter decomposition process. 

Carreiro, M. M., R. L. Sinsabaugh, D. A. Repert, and M. Parkhurst. 2000. Microbial enzyme shifts explain litter decay responses to simulated nitrogen deposition. Ecology... 

Moorhead, D. L., and R. L. Sinsabaugh. 2000. Simulated patterns of litter decay predict patterns of extracellular enzyme activities. Applied Soil Ecology 14 71-79. 

Figure 8.7 Rates of fresh litter decomposition (y-1) in soils in the USA, using a simulation model based on evapotranspiration rates as a predictive variable. Contour lines represent loss rate (k) during an initial year of decay. (Modified from Meentemeyer, 1978.)...

Additional information on how leaf litter potentially interacts with acid rain was contributed by Lee V7eber (2 ). In their experiments, acid rain was simulated in a field situation on sugar maple and red alder. Rain as throughfall was allowed to interact with leaf litter and the leachate was collected. Litter leachate was found to be higher in S0 , Ca+ and Mg+, and the pH was found to have increased. Thus, they hypothesized that the litter was neutralizing the simulated acid rain, with red alder litter being more effective than sugar maple. 

The term d[P j,]/dt is calculated assuming that the concentration of phosphorus in all decomposing litter is 0.16 mmol 1110 . This is based on the 68% retranslocation of P from leaves and fine roots and the average branch, bole, and coarse root P concentrations (Sec. 3.2). Where the sensitivity of the model to P accumulation in the microbial carbon pool is tested, based on data summarized by Gijsman et al. (1996) we use a tissue P concentration for microbes of 6.4 mmol P moG C. In all simulations, it is assumed that soil phosphorus mineralization proceeds with a rate constant of 0.5 year , with phosphorus mineralization proceeding independently of carbon mineralization. This is on the basis of the evidence discussed in Sec. 2.1. Indeed, inflexible soil carbon pool C/P ratios which effectively link phosphorus mineralization rate to the carbon mineralization rate in models such as CENTURY (Parton et al, 1988) have been strongly criticized by some tropical soil chemists (Gijsman et al, 1996). 

Recent years have seen the development of prediction tools for the transport layers of plastic litter. These tools provide the facility to follow the trajectories of clusters that may be washed ashore. Evenmally, the development of an atlas of risk sensitivity will facilitate the improvment of the management of accidental risks. However, simulations performed globally over several years help in the identification of the most sensitive zones at the global scale, such as the Mediterranean, the Atlantic and Pacific convergence areas, and the Bay of Bengal. These areas on their own should receive within 30 years between 35 and 60% of all litter at sea [LEB 11],... 

Guillet, J. E. and Ainscough, A.N. Studies of the accumulation of plastic litter by computer simulation. Internal report available from the author. 

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