Organic matter quality of forest floor as a driver of C and P dynamics in acacia and eucalypt plantations established on a Ferralic Arenosols, Congo

Background: Land-use change and forest management may alter soil organic matter(SOM) and nutrient dynamics,due in part to alterations in litter input and quality. Acacia was introduced in eucalypt plantations established in the Congolese coastal plains to improve soil fertility and tree growth. Eucalypt trees were expected to benefit from N2 fixed by acacia. However, some indicators suggest a perturbation in SOM and P dynamics might affect the sustainability of the system in the medium and long term. In tropical environments, most of the nutrient processes are determined by the high rates of organic matter(OM) mineralization. Therefore, SOM stability might play a crucial role in regulating soil-plant processes. In spite of this, the relationship between SOM quality, C and other nutrient dynamics are not well understood. In the present study, OM quality and P forms in forest floor and soil were investigated to get more insight on the C and P dynamics useful to sustainable management of forest plantations.Methods: Thermal analysis(differential scanning calorimetry(DSC) and thermogravimetry(TGA)) and nuclear magnetic resonance(solid state13 C CPMASS and NMR and31 P-NMR) spectroscopy have been applied to partially decomposed forest floor and soils of pure acacia and eucalypt, and mixed-species acacia-eucalypt stands.Results: Thermal analysis and13 C NMR analysis revealed a more advanced stage of humification in forest floor of acacia-eucalypt stands, suggesting a greater microbial activity in its litter. SOM were related to the OM recalcitrance of the forest floor, indicating this higher microbial activity of the forest floor in this stand might be favouring the incorporation of C into the mineral soil.Conclusions: In relation with the fast mineralization in this environment, highly soluble orthophosphate was the dominant P form in both forest floor and soils. However, the mixed-species forest stands immobilized greater P in organic forms, preventing the P losses by leaching and contributing to sustain the P demand in the medium term.This shows that interactions between plants, microorganisms and soil can sustain the demand of this ecosystem.For this, the forest floor plays a key role in tightening the P cycle, minimizing the P losses.

Pyrolysis of WEEE plastics using catalysts produced from fly ash of coal gasification

Catalytic pyrolysis of thermoplastics extracted from waste electrical and electronic equipment （WEEE） was investigated using various fly ash-derived catalysts. The catalysts were prepared from fly ash by a simple method that basically includes a mechanical treatment followed by an acid or a basic activation. The synthesized catalysts were characterized using various analytical techniques. The results showed that not treated fly ash （FA） is characterized by good crystallinity, which in turn is lowered by mechanical and chemical treatment （fly ash after mechanical and acid activation, FAMA） and suppressed almost entirely down to let fly ash become completely amorphous （fly ash al^er mechanical and basic activation FAMB）. Simultaneously, the surface area resulted increased. Subsequently, FA, FAMB and FAMA were used in the pyrolysis of a WEEE plastic sample at 400~C and their performance were compared with thermal pyrolysis at the same temperature. The catalysts principally improve the light oil yield： from 59 wt.% with thermal pyrolysis to 83 wt.% using FAMB. The formation of styrene in the oil is also increased： from 243 mg/g with thermal pyrolysis to 453 mg/g using FAMB. As a result, FAMB proved to be the best catalyst, thus producing also the lowest and the highest amount of char and gas, respectively.

Thermal and catalytic pyrolysis of a synthetic mixture representative of packaging plastics residue

A synthetic mixture of real waste packaging plastics representative of the residue from a material recovery facility(plasmix)was submitted to thermal and catalytic pyrolysis.Preliminary thermogravimetry experiments coupled with Fourier transform infrared spectroscopy were performed to evaluate the effects of the catalysts on the polymers’degradation temperatures and to determine the main compounds produced during pyrolysis.The thermal and catalytic experiments were conducted at 370℃,450℃ and 650℃ using a bench scale reactor.The oil,gas,and char yields were analyzed and the compositions of the reaction products were compared.The primary aim of this study was to understand the effects of zeolitic hydrogen ultra stable zeolite Y(HUSY)and hydrogen zeolite socony mobil-5(HZSM5)catalysts with high silica content on the pyrolysis process and the products’quality.Thermogravimetry showed that HUSY significantly reduces the degradation temperature of all the polymers—particularly the polyolefines.HZSM5 had a significant effect on the degradation of polyethylene due to its smaller pore size.Mass balance showed that oil is always the main product of pyrolysis,regardless of the process conditions.However,all pyrolysis runs performed at 370℃ were incomplete.The use of either zeolites resulted in a decrease in the heavy oil fraction and the prevention of wax formation.HUSY has the best performance in terms of the total monoaromatic yield(29 wt-%at 450℃),while HZSM5 promoted the production of gases(41 wt-%at 650℃).Plasmix is a potential input material for pyrolysis that is positively affected by the presence of the two tested zeolites.A more effective separation of polyethylene terephthalate during the selection process could lead to higher quality pyrolysis products.