Browsing by Subject "degradation"

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  • Islam, Md. Safiqul (Helsingfors universitet, 2016)
    Mulching, as a cultivation technique, has been adopted since the early twentieth century in agriculture for improving various aspects of crop production. However, the use of mulching was boosted by the introduction of plastic mulch, which has been reported as a harmful substance to the farm environment. Therefore, the need for an environmentally benign mulch material is obvious. The present study investigated the effects of paper and biodegradable plastic mulches on the cucumber yield, soil temperature and moisture content (at 10 cm depth), and the control of weed growth in an agricultural field located at the University of Helsinki in Southern Finland. The degradability of mulches was also investigated. The null hypothesis was that all the mulches would have a similar effect on the abovementioned aspects. Four paper mulches, i.e., BP, KB, CK, and OB, accompanied by biodegradable mulch (BIO) and a bare soil (BG) treatment were under investigation. Each of these treatments had 4 replicates, and a randomized complete block design (RCBD) was adopted. Sensors were installed at 10 cm depth in each study plot to measure the soil temperature and moisture content. In addition, the experimental plots were watered by drip irrigation. All the attained data were analyzed using SPSS statistical software. The results of the study revealed noteworthy positive effects (P<0.05) of mulch application on cucumber yields together with soil temperature, early fruiting, and weed growth regulation compared to the un-mulched bare ground, exclusive of soil moisture content. The daytime soil temperature (DST) was higher than at night (NST), indicating a positive association of the mulch effect with plant growth and crop earliness. However, no suggestive improvement in soil moisture was found through mulch application during the study period. Edge degradation was only found for paper mulches during the study period, suggesting their environment friendliness. The CK and KB papers were the most effective and most environmentally positive mulch materials, and could be a suitable choice for Finnish vegetable growers. The findings of this study could assist paper manufacturers in improving the qualities of mulch papers regarding vegetable production. Future research aims at assessing the effects of mulches on the physiology of plants studied under mulched techniques together with the development of cheaper and more environmentally benign mulch materials.
  • Silvola, Jouko; Välijoki, Jukka; Aaltonen, Heikki (Suomen metsätieteellinen seura, 1985)
    At sites in SE Finland, hourly respiration varied mainly in the range 100-500 mg CO2/msuperscript 2 with changes following those in soil surface temp. with a time lag of 3 h. After groundwater table was reduced by about 0.5 m, respiration increased 2.5-fold (resulting in a rate of peat decomposition considerably in excess of the rate of production of new organic matter in the peat). Application of fast-dissolving PK or urea rapidly increased soil respiration at the site poorest in nutrients. Ash gave the greatest steady increase. At sites rich in nutrients, fertilizer treatment reduced soil respiration for 1-2 yr. Treatment with micronutrients caused an intial reduction in respiration followed by a pronounced increase.
  • Hakala, Kati P. (2020)
    Fungal disease late blight (Phytophthora infestans) causes considerable damage to potato crops worldwide. Fluazinam is a widely used pesticide employed against the late blight in potato cultivation. It ends up into soil during spraying and at the end of the growing season when potato foliage is incorporated into the soil. Nevertheless, there is very little literature about behaviour of fluazinam in soil, especially in the conditions that exist in Finland. Therefore, in the preparation of user guidelines, studies made elsewhere are used. From the environmental risks point of view, behaviour of fluazinam in Finnish conditions should be known better. Soils in the boreal zone are characterised by low pH and low temperatures that delay microbiological decomposition and they are typically high in organic matter and saturated by water for long periods in autumn, winter and spring. A prerequisite for assessing the environmental risk of fluazinam is knowledge of its sorption and desorption tendency as well as its degradation rate in boreal conditions. This information is needed, because more aggressive strains of Phytophthora infestans have spread to northern latitudes, increasing the need to use fungicides. In this study, a specific and repeatable high-performance liquid chromatography method utilizing a diode array detector was developed to determine the presence of fluazinam in soil. This method differs from most of the methods found in the literature, which used gas chromatography or gas chromatography-mass spectrometry as an instrument for analysing fluazinam. The method consists of acetonitrile extraction, clean-up with solid-phase extraction and separation using a mobile phase consisting of 70% acetonitrile and 30% water (v v-1), including 0.02% acetic acid. The method was successfully applied to various laboratory experiments and to soil samples collected from potato fields in which fluazinam had been used. In the systematic experiments carried out in controlled conditions, performed with both the fluazinam standard and the commercial product Shirlan®, the effect of soil organic matter on the fluazinam degradation was tested, as well as the persistence of fluazinam in the boreal zone soils for a maximum of one year. The major outcomes of the laboratory experiments were that fluazinam degradation was enhanced by the presence of soil organic matter and even after one year of incubation, more than half of the added fluazinam was recovered. Additionally, soil samples were collected from intensively cultivated potato fields. Over half of these field samples contained varying concentrations of fluazinam, but no substantial accumulation of fluazinam was detected.
  • Korpela, Heta (Helsingin yliopisto, 2020)
    One of the most common packaging materials for food is polymers. The properties offered by plastic packaging are good for food, but there is a general demand to reduce the usage of plastic. The demand for reduction is due to the fact that plastic is often made from fossil raw materials. In the case of foodstuffs, it is not possible to completely remove the plastic packaging material as this would result in faster food spoilage and thus greater food waste. The amount of plastic can be reduced by using it as part of the multilayer material. In multilayer materials, the most common raw material is cardboard, which is generated from renewable raw materials. In addition to plastic packaging made of virgin material, plastic materials made from recycled polymers may also be used in food packaging in future, provided that their safety conditions are met. The aim of the study was to investigate the effect of freezing temperatures and ultraviolet radiation (UV) on the properties and aging of recycled plastic. The research methods were divided into physical, barrier and chemical measurements. Samples were imaged using a scanning electron microscope. The hypothesis in the study was that freezing conditions and UV treatment both age the packaging material. UV radiation is expected to age samples more than freezing conditions. The study will focus on PET (polyethylene terephthalate) and LDPE (low density polyethylene) coated cardboards. The study partially answers to the hypothesis. Frost conditions were had weaker aging effect than UV radiation, as expected. On the other hand, recycled plastics cannot be said to be easier to age than virgin materials. Particularly between the different measurements, the materials did not differ clearly in their aging.
  • Dilokpimol, Adiphol; Peng, Mao; Di Falco, Marcos; Chin A Woeng, Thomas; Maria Wilhelmina Hegi, Rosa; Granchi, Zoraide; Tsang, Adrian; Hildén, Kristiina S.; Mäkelä, Miia R.; de Vries, Ronald P. (2020)
    Penicillium subrubescens is able to degrade a broad range of plant biomass and it has an expanded set of Carbohydrate Active enzyme (CAZyme)-encoding genes in comparison to other Penicillium species. Here we used exoproteome and transcriptome analysis to demonstrate the versatile plant biomass degradation mechanism by P. subrubescens during growth on wheat bran and sugar beet pulp. On wheat bran P. subrubescens degraded xylan main chain and side residues from the Day 2 of cultivation, whereas it started to degrade side chain of pectin in sugar beet pulp prior to attacking the main chain on Day 3. In addition, on Day 3 the cellulolytic enzymes were highly increased. Our results confirm that P. subrubescens adapts its enzyme production to the available plant biomass and is a promising new fungal cell factory for the production of CAZymes.
  • Hakala, Kati P.; Yli-Halla, Markku J.; Tuomainen, Paivi M.; Hartikainen, Helina (2020)
    Fluazinam, a widely used pesticide in conventional potato cultivation, is effective against epidemics of the fungal disease late blight. To assess fluazinam persistence in soil, laboratory experiments were conducted with fluazinam added to soil as a pure chemical or contained in the commercial product Shirlan (R). In a follow-up experiment, the persistence was monitored under constant temperature and water content conditions during a maximum period of 1 year. In an annual climatic rotation experiment, fluazinam added to soil was exposed to the year-round temperature and water content conditions occurring in the boreal zone. A third experiment was undertaken to clarify the effect of soil organic matter (SOM) on the recovery of fluazinam. In the follow-up and annual climatic rotation experiments, more than half of the added fluazinam was recovered after 1 year of incubation. The estimated half-life of fluazinam ranged between 355 and 833 days. The degradation of fluazinam was enhanced by an abundance of SOM, a warm temperature, and wetness. Additionally, in over half of soil samples collected from fields where potato had been intensively cultivated for many years, varying concentrations of fluazinam were detected. Fluazinam can carry over to the next growing season in professional potato production.
  • Wu, Laiyan; Pflugmacher, Stephan; Yang, Anping; Esterhuizen-Londt, Maranda (2018)
    Background: Uniquely synthesised titanium dioxide (TiO2) with high-energy {001} exposed facets denoted HF8 was used for the photocatalytic degradation of microcystin-LR (MC-LR) under ultraviolet irradiation at 365 nm. Methods: The influence of various conditions including environmental pH, nutrient anions, TiO2 dose, and MC-LR concentration was studied, and concentration of MC-LR measured using liquid chromatography-tandem mass spectrometry. Results: Within 120 min, 72.6% of an environmentally relevant MC-LR concentration (120 µg/L) was degraded under pH conditions ranging from 3 to 11. Stability tests revealed no loss of TiO2 activity after four applications of the same dose, indicating its stability, reusability, and potential to be re-used for sustainable remediation of MC-LR in eutrophic waters. Mechanism studies suggested that the reaction obeyed the pseudo-first-order equation and that hydroxyl radicals are the major reactive intermediate contributing to the reaction. The structure elucidation of intermediates suggested that hydroxylation and bond cleavage between the Adda chain and Mdha site could be the initiation of reactions in the degradation of MC-LR by HF8 TiO2. Conclusion: The results present a fast, sustainable, and practical method using modified TiO2 to improve MC-LR remediation.
  • Kambire, Hermann; Djenontin, Ida Nadia; Kabore, Augustin; Djoudi, Houria; Balinga, Michael; Zida, Mathurin; Assembe-Mvondo, Samuel; Brockhaus, Maria (Center for International Forestry Research, 2016)
    Occasional paper
  • Thu Thuy Pham,; Wong, Grace; Le, Dung Ngoc; Brockhaus, Maria (Center fo International Forestry Research, 2016)
    Occasional paper