Soil Burial Research Articles

Effects of Tensile Stress and Soil Burial on Mechanical and Chemical Degradation Potential of Agricultural Plastic Films

Plastic film mulching is widely practiced in arid and semiarid farming systems, but the accumulation of plastic residues in soils can negatively affect soil properties. Therefore, efficient means of plastic film degradation are urgently needed to mitigate its unfriendly environmental impacts for sustainable land use. Here, we characterized the effects of tensile stress (TS) and soil burial (SB) on potential degradation properties of three film types: Polyethylene film (PEF), oxo-biodegradable film (OBDF), and biodegradable film (BDF). Weight loss, mechanical properties, hydrophilicity, functional groups, and crystallinity were recorded after TS and SB treatments. The results indicated that: (1) Weight loss of plastic films was associated with SB, although the extent of weight loss depended on film type and was highest in BDF, (2) application of TS before SB weakened the mechanical properties of the films and increased their hydrophilicity, creating favorable conditions for the settlement of microorganisms on the film surface, (3) PEF treated with TS and SB had higher functional group indices and lower crystallinity. Our results highlighted that the combination of TS and SB has the potential to accelerate plastic film degradation.

Effect of soil burial on silane treated and untreated kenaf fiber filled linear low-density polyethylene/polyvinyl alcohol composites

In recent decades, natural fibers have become widely used with petroleum based polymers such as polyethylene (PE) and polypropylene (PP) because of their light weight, lower cost, and inherent biodegradability. In the present work, linear low-density polyethylene/polyvinyl alcohol (LLDPE/PVOH) composites with untreated kenaf and silane-treated kenaf at filler loadings of 0, 10, and 40 phr were prepared via the melt mixing process. The soil burial test was used to evaluate the degradability of the composites for different durations (90 and 180 d). The tensile properties, surface morphology, chemical composition, percentage of weight loss, and crystallinity of the composites before and after degradation were evaluated. With increased kenaf loading and soil burial duration, all the composites showed a decrease in tensile properties. This was further confirmed by the changes in surface morphology and chemical structure of the buried composites. The increase in weight loss percentage and crystallinity after soil burial indicated that the longer burial duration had increased the degradation of composites. Composites with silane-treated kenaf exhibited lower degradability than that of composites with untreated kenaf after being buried for 90 and 180 d. This may be attributed to the improved adhesion of kenaf to the LLDPE/PVOH matrix via silane treatment.

The Effects of Micro-organisms in Simulated Soil Burial on Cellulosic and Proteinaceous Textiles and the Morphology of the Fibres

ABSTRACT The aim of this research was to compare the performance of different cellulosic and proteinaceous textiles when exposed to the action of micro-organisms and to produce reference data for fibre identification of biodegraded textiles. Thus, the effects of micro-organisms grown in simulated soil burial on the textiles and their fibres were investigated. Cotton, linen, hemp, nettle, silk, and wool textiles were used for the experiments. Samples were buried in loam soil for 2, 4, 8, 16, and 32 weeks in a laboratory environment away from light. The cellulosic textiles were more readily attacked by microorganisms, followed by the wool, while the preservation of the silks was remarkable. The molecular composition and structure of the fibres, as well as the structure of the textiles themselves seem to be responsible for the different degrees of deterioration. The morphology of all fibres apart from silk was severely affected, in some cases to unrecognisable degrees. Notable degradation patterns developed like diagonal splits and grooves in cotton; longitudinal splits, erosion, and fibrillation in linen, hemp, and nettle; shedding of the scales and fibrillation in wool; and exposure of the inner fibrils in silk.

Release of Medicago truncatula Gaertn. and Pisum sativum subsp. elatius (M. Bieb.) Asch. et Graebn. Seed Dormancy Tested in Soil Conditions

Medicago truncatula (barrel medic) and Pisum sativum subsp. elatius (wild pea) accessions originating from variable environmental conditions in the Mediterranean basin were used to study physical seed dormancy (PY) release. The effect of soil burial on PY release was tested on 112 accessions of medic and 46 accessions of pea over the period of 3 months in situ at three common gardens (Hungary, Spain and Greece) from 2017 through 2019. PY release after soil exhumation followed by experimental laboratory germination of remaining dormant seeds (wet, 25 °C, 21 days) were related to the environmental conditions of the common garden and macroclimatic variables of the site of origin of the accessions. Higher PY release was observed in buried seeds under humid rather than under dry and hot environments. Exposure of remaining dormant seeds to experimental laboratory conditions increased total PY release up to 70% and 80% in barrel medic and wild pea, respectively. Wild pea showed higher phenotypic plasticity on PY release than barrel medic, which had higher bet-hedging within-season. Wild pea showed lower bet-hedging among-season (PY < 10%) in relation to precipitation than barrel medic, which was more conservative (PY ≈ 20%). Observed variability suggests that these species have the capability to cope with ongoing climate change.

Physical, dielectric and biodegradation studies of PVC/silica nanocomposites based on traditional and environmentally friendly plasticizers

PVC/nano-SiO2 nanocomposites based on a bio-based plasticiser (castor oil) and dioctyl phthalate (DOP) were prepared using solution casting method. Castor oil (CO) was used as a complete alternate plasticiser of dioctyl phthalate (DOP) in PVC. The prepared films were characterised by different techniques. In addition, the biodegradation of the films was tested by soil burial, hydrolytic and enzymatic degradation tests. The presence of CO facilitates the dispersion of SiO2 in PVC matrix and enhances the thermal stability. Besides, it has a significant contribution in reduction of HCl emission during the decomposition of PVC nanocomposites. FTIR spectra of the nanocomposite films showed a considerable change in the intensity of the characteristic peaks of the functional group by addition of SiO2 and after proceeding hydrolytic and enzymatic degradation as well. Additionally, the presence of SiO2 plays a dominant role in improving the migration stability and volatility of the plasticiser. Further, the permittivity (ε’), loss factor (tanδ), electric modulus (M’) and conductivity (σ) of PVC were also investigated. It is found that the values of ε’ and σ of PVC/CO/SiO2 nanocomposites are higher compared to those of PVC/DOP/SiO2 nanocomposites. Moreover, electric modulus (M’) demonstrates two dielectric relaxation processes. The conductivity values revealed that PVC nanocomposites can perform as antistatic materials. This makes them a good choice for electronic components packaging.

Efficient removal of atmospheric dust by a suppressant made of potato starch, polyacrylic acid and gelatin

Air pollution by dust particles is a major health concern in urban and industrialized areas. Actual methods to reduce dust contamination, such as water spraying, are limited, calling for new dust suppressants. Here, we synthesized a liquid starch-based dust suppressant by grafting polyacrylic acid onto NaOH-pretreated potato starch and then crosslinking the grafted copolymer with gelatine. This dust suppressant was characterized by Fourier-transform infrared spectrometry, thermogravimetry, viscosity and contact angle measurements. We also measured permeability, water retention, anti-wind erosion and degradability of the dust suppressant. Field experiments tested the dust suppressing effect on particle matter 2.5 (PM2.5) and particulate particle matter 10.0 (PM10). We found that the addition of NaOH to potato starch improved the reaction efficiency and simplified the preparation process. The dust suppressant demonstrated excellent degradability, as shown by weight loss of 82 wt % after 60 days of soil burial, and the total dust suppression rates reached 57% for PM2.5 and 56% for PM10 in the field. Compared with spraying water, total dust suppression was higher by 25% and 33%, respectively.

Germination response of invasive plants to soil burial depth and litter accumulation is species‐specific

AbstractQuestionsPlant invasions are considered among the biggest threats to biodiversity worldwide. In a full‐factorial greenhouse experiment we analysed the effect of soil burial depth and litter cover on the germination of invasive plants. We hypothesised that: (a) burial depth and litter cover affect the germination of the studied species; (b) the effects of burial and litter cover interact with each other, and (c) the effects are species‐specific, but dependent on seed size.MethodsWe tested the germination and seedling growth of 11 herbaceous invasive species in a full‐factorial experiment using four levels of seed burial depths and litter cover. We analysed the effect of burial, litter cover, and their interactions on germination, seedling length and biomass across species and at the species level.ResultsSoil burial depth and litter cover had a significant effect on the germination of the studied species, but there were considerable differences between species. We observed a general trend of species with bigger seeds being not or less seriously affected by soil burial and litter cover than smaller‐seeded species. Correlations between seed weight and effect sizes mostly confirmed this general trend, but not in the case of soil burial.ConclusionsOur findings confirmed that seed size is a major driver of species’ response to litter cover and to the combined effects of litter cover and soil burial, but there is no general trend regarding the response to soil burial depth. Despite its very small seeds, the germination of Cynodon dactylon was not affected by soil burial. The germination of Ambrosia artemisiifolia was hampered by both soil burial and litter cover despite its relatively large seeds. Thus, specific information on species’ response to burial depth and litter accumulation is crucial when planning management or restoration in areas threatened by plant invasions.

Effect of blend composition on characteristics and performance of Jatropha bio-epoxy/epoxy matrix in composites with carbon fiber reinforcement

Characteristics and performances of a blended jatropha bio-epoxy/epoxy as a matrix in carbon fiber reinforcement was studied. The amount of bio-epoxy was arranged from 0 wt%, 25 wt%, 30 wt%, 40 wt%, and 50 wt% of the total matrix. Several analyses were performed to characterize and observe their performance. Fourier transform infrared spectroscopy, thermal analysis, physical characteristics, flammability, and soil burial were conducted, as well as mechanical tests. The results showed that introducing bio-epoxy in the matrix changed characteristics and increased or decreased their performance. Blending more than 25 wt% of bio-epoxy led to improved thermal stability between 280 °C to 350 °C and better biodegradability. However, tensile and flexural strength as well as modulus of elasticity decreased once the proportion of bio-epoxy was greater than 25 wt%. The paper proposed an optimal amount of jatropha bio-epoxy so that an alternative biocomposite application could be introduced to minimize carbon footprint in the environment.

Development of biodegradable natural rubber latex composites by employing corn derivative bio‐fillers

AbstractThis study aims to investigate the viability of employing corn‐based fillers (powdered corn grain [CG], corn flour [CF] and cornstarch [CS]) to improve the biodegradability of natural rubber latex (NRL) composites by varying filler loading from 0 to 50 phr. Notable variation in both physical and mechanical properties were observed for the different filler types, with CG‐filled NRL demonstrating the better adhesion with NRL. Thus, CG‐filled composites were selected for investigation of biodegradability. Increased CG loading in NRL compounds enhanced biodegradation; with over 70% degradation observed for 50 phr CG loading upon 15 weeks of soil burial. However, the trade‐off between mechanical properties and biodegradability limits the CG loading in the NRL matrix to 20 phr for manufacturing NRL‐based products. It was observed that NRL with CG filler loading of 20 phr conforms to the ASTM D3578 standard for manufacturing rubber gloves; with 50% biodegradation upon 15 weeks of soil burial.

The Effect of Carbodiimide on the Stability of Wood Fiber/Poly(lactic acid) Composites During Soil Degradation

To prolong the service lives of wood fiber (WF)/poly(lactic acid) (PLA) composites, composites with different contents of bis (2,6-diisopropylphenyl) carbodiimide (BDICDI) were prepared. The composites were buried in natural soil for 150 days to evaluate the stabilizing effect of BDICDI on the WF/PLA composites. It was also used to evaluate the properties changes of WF/PLA composites under extreme conditions. The changes in the chemical structures, molecular weights and thermal properties of the WF/PLA composites during soil burial and the stabilization mechanism of BDICDI on the composites were studied. The results showed that the addition of BDICDI reacted with both the formed acid and the water absorbed by the WF/PLA composites, which inhibited the breaking of ester bonds in the WF/PLA composites. After 120 days of soil burial, the tensile strengths of the WF/PLA/1 wt% BDICDI composites were 1.31 times to those of the WF/PLA composites. This research provided theoretical support to prolong the service lives of WF/PLA composites and expanded the application scope of WF/PLA composites.

Accelerated Weathering and Soil Burial Effect on Biodegradability, Colour and Textureof Coir/Pineapple Leaf Fibres/PLA Biocomposites.

Accelerated weathering and soil burial tests on biocomposites of various ratios of coir (CF)/pineapple leaf fibres (PALF) with polylactic acid (PLA) were conducted to study the biodegradability, colour, and texture properties as compared with PLA.The biodegradability of a lignocellulosic composite largely depends on its polymer matrix, and the rate of biodegradation depends on many environmental factors such as moisture, light(radiation), temperature and microbes. Biodegradation was evaluated by soil burial and accelerated weathering tests. Changes in physical and morphological properties were observed in the biocomposites after weathering. These results allowed us to conclude that untreated CF/PALF/PLA biocomposites would be a more favourable choice owing to their better biodegradability and are suitable for the suggested biodegradable food packaging applications.

Soil Inoculation with Pseudomonas geniculata WS3 for Accelerating the Biodegradation Process of In Situ Compatibilized PBS/PLA Blends Doped with HPQM

This work studied the biodegradative activity of Pseudomonas geniculata WS3 and Stenotrophomonas pavanii CH1, PLA-degrading bacteria, on films with different ratios of polybutylene succinate (PBS)/polylactic acid (PLA), in submerged cultures. Effects of PBS, dicumyl peroxide (DCP) and 2-hydroxypropyl-3-piperazinyl quinoline carboxylic acid methacrylate (HPQM) of in situ compatibilized PBS/PLA blends were also examined under soil burial biodegradation at mesophilic and thermophilic conditions. The results from the submerged experiments showed that the weight loss of PBS/PLA blends increased with increasing PBS content. All blending ratios of PBS/PLA were more degraded by P. geniculata WS3 than S. pavanii CH1. After soil burial, PBS/PLA films with 40/60 wt% showed higher biodegradation than those with 20/80 wt% with or without P. geniculata WS3 inoculation. However, the biodegradation of PBS/PLA blends inoculated with P. geniculata WS3 was higher than that of the uninoculated treatment. The addition of DCP in PBS/PLA blends decreased the biodegradation and weight loss. Unexpectedly, the degree of biodegradation and weight loss of PBS/PLA at a ratio of 20/80 wt% with DCP added were higher than that of PBS/PLA at a ratio of 40/60 wt% with DCP added. The addition of HPQM, showing antibacterial properties, decreased the biodegradation of PBS/PLA blends by 1.4 to 1.8-fold compared to those without HPQM addition. It could be concluded that the inoculation of P. geniculata WS3 mainly promoted the biodegradation of PBS/PLA blends under mesophilic condition. However, the addition of DCP and HPQM decreased the biodegradation of the PBS/PLA blends.

Rice straw powder/polylactic acid biocomposites for three-dimensional printing

The research aim of this work was to understand the effects of the soil burial of rice straw on the morphology and properties of 3D-printed rice straw powder (RSP)/polylactic acid (PLA) biocomposites. The rice straw buried in the soil for various days was grounded and sieved into powder at 120 mesh. The RSP was then mixed with PLA at a mass ratio of 15/100 and the mixture was extruded into filament, followed by a fused deposition modeling 3D printing process. The as-prepared products were characterized in terms of morphological, mechanical, thermal, and nonisothermal crystallization properties. The results show that cavities with large holes induced by fused deposition modeling exhibit on the cross section of RSP/PLA biocomposite. The longer the burial duration of rice straw, the more the cavities with large holes could be observed on the surface. Therefore, soil burial of rice straw improved the thermal stability of the biocomposites while depressing their mechanical properties due to the amplification of the cavities. The crystallinity of the biocomposites was maintained at a low level (<9%) before and after the soil burial process.

Effect of Soil Burial on Mechanical Properties of Bamboo Fiber Reinforced Epoxy Composites

Nowadays, natural fiber reinforced composites in structural strengthening and rehabilitation was preferable due to its environmentally friendly, low cost and biodegradable characteristics compared to the synthetic strengthening material, fiber reinforced polymer (FRP). However, limited information is available on natural fiber composite durability when exposed to environmental elements. This paper presents the effect of environmental exposure to the durability of bamboo fiber reinforced epoxy composite. Bamboo fiber reinforced epoxy composite samples were prepared and buried in soil for 20, 40, 60 and 80 days. The composite samples were prepared using 40% fiber volume fractions. The mechanical properties (tensile and flexural) and surface morphology of the samples before and after degradation were investigated. The experimental results show that the mechanical properties deteriorate as the exposure time increases. The tensile and flexural properties of the composites decreased by about 6-19% compared to the fresh sample. The result from this work may be useful to determine the durability of natural fiber composite when exposed to environmental elements.

Biodegradability of Cassava Starch/High Density Polyethylene Reactive Blend During Compost Burial

Starch is promising material to answer the environmental hot issues related to plastic wastes. Plasticized and gelatinized starch can behave as thermoplastic that completely biodegrade in nature. This study was aimed to investigate the biodegradability of cassava starch (CS) blended with high density polyethylene (HDPE). Simulated soil burial was applied using the compost. The blends were prepared by reactive mixing using Haake Rheomix internal mixer. The ratio of starch and HDPE was ranging from 30/70, 40/60, 50/50, 60/40, and 70/30. Dual hydrophobization was employed, i.e. addition acetic acid and polyethylene-grated maleic anhydride (PE-g-MA). Compost burial was performed indoor for 56 days. The surface appearance and morphology were investigated. Weight loss and change in tensile strength and elongation at break after burial also determined. Results findings showed that the increasing of cassava starch content and burial time decrease the tensile strength and elongation at break, however increased the weight loss of CS/HDPE reactive blend. In addition, evidence of biodegradation is shown by the appearance of some microorganism colonies on the surface of reactive blend and morphological changes in CS/HDPE reactive blend.

Enhancing long-term biodegradability and UV-shielding performances of transparent polylactic acid nanocomposite films by adding cellulose nanocrystal-zinc oxide hybrids

We investigated UV-shielding performances and biodegradation abilities under controlled hydrolytic, soil burial, and thermal conditions of transparent polylactic acids (PLA) nanocomposite films embedded with cellulose nanocrystal-zinc oxide (CNC-ZnO) hybrids. By adding high content of 15wt %CNC-ZnO hybrids into the PLA matrix, the highest UV radiation was blocked out by (85.31%) of UV-A and (95.90%) of UV-B. It is found that the weight loss of PLA nanocomposites after being hydrolytic degraded for 70 days increased from 9% for PLA to 25% with 15 wt% CNC-ZnO hybrids. Meanwhile, in soil burial test, pure PLA shows smallest degradation rate with only 8% weight loss after 110 days, while the PLA nanocomposite film with 15 wt% CNC-ZnO hybrids was degraded by about 28%. Besides, the resultant degradation byproducts from the thermally-decomposed catalysis have been identified by Fourier transform infrared spectroscopy (FT-IR). Moreover, the morphologies and appearances changes during the hydrolytic and soil degradation of PLA nanocomposite films were evaluated. This study is expected to provide meaningful insights into nanocomposite films embedded with CNC-ZnO hybrids as a result of contourable degradation and high ultraviolet protection factor value (UPF).

Insights into the evaluation of the abiotic and biotic degradation rate of commercial pro-oxidant filled polyethylene (PE) thin films

In this study, commercial products formulated from polyethylene (PE) with pro-oxidant additives, were subjected to abiotic and biotic environments. The materials were presumed to be oxo-biodegradable plastics with thicknesses varying between 30 and 70 μm, and calcium carbonate (CaCO3) filler content reaching up to 11 wt%. Accelerated (aging) weathering tests conducted revealed that UV radiation triggered the biodegradation mechanism. Weight loss reached 50% after exposure to weathering which was attributed to triggering the fragmentation of the plastic films. Furthermore, some 83% of weight loss was estimated after 12 months of soil burial. Fluctuation of weight in mid exposure time spans was related to the cross-linking reaction within the polymeric matrix. The mechanical properties investigated along with the thermal stability profile determined for the materials showed that weathering was more severe than soil burial. Thermogravimetry revealed that onset temperature (Tos) was lower than conventional PO products by 25 °C. This could be attributed to the thermal response of the materials due to presence of ion salts and sterates within their composition. The claims by the manufacturing companies which provided the original specimens under an environmentally friendly pretence is disputed due to the fact that none of the products actually showed evidence of major fragmentation or deterioration after exposure to harsh environments. The work also paves the way in standardising assessment methodology for examining biodegradable plastics.

Effect of Soil Burial on Physical, Mechanical and Thermal Properties of Sugar Palm Fibre Reinforced Vinyl Ester Composites

The aim of this research is to investigate the effect of soil burial on physical, mechanical and thermal properties of sugar palm fibre (SPF) reinforced vinyl ester (VE) composites. Neat VE and SPF/VE composites at weight ratio of 10 wt.% SPF were prepared using wet hand lay-up method. The specimens were buried in the soil for 0, 200, 400, 600, 800 and 1000 hours to investigate the effect of soil burial to its physical properties (i.e. water absorption), mechanical properties (i.e. tensile, flexural and impact strength) and thermal properties. Obtained results indicated that, the longer soil burial period led to high water absorption of the composites. After 200 hours of soil burial, the SPF/VE composites water uptake increased 0.92 % compared to neat VE which is 0.42 %. Based on the results, soil burial reduces the mechanical strength of the composites. Tensile, flexural and impact strength decreased rapidly after 200 hours of soil burial compared to neat VE which were 28.24 %, 8.04 % and 14.83 %, respectively. Thermal stability after 200 hours of soil burial increase temperature onset of the SPF composites compared to neat VE. Overall, soil burial increased water absorption, temperature onset of the SPF composites and at the same time decreased the tensile, flexural and impact strength of the composites.

Accelerated weathering and soil burial effects on colour, biodegradability and thermal properties of bamboo/kenaf/epoxy hybrid composites

This study aims to gain insight into the influence of environmental effects on the colour, biodegradability, oxidation stability, thermal stability and complex modulus of bamboo/kenaf fiber reinforced epoxy hybrid composites. The composites were prepared by the hand lay-up technique, with a fixed loading of 40% fibers for all the composites. Three types of hybrid composites were prepared with different mixing ratios of bamboo fibers (B) to kenaf fibers (K): (i) 30:70, (ii) 50:50, and (iii) 70:30. Kenaf/epoxy and bamboo/epoxy composites, as well as pure epoxy, were also prepared for comparison purposes. The kenaf, bamboo and hybrid composites were exposed to UV radiation at elevated temperature and humidity, for a total exposure period of 156 h. The colour changes occurring during the weathering process were assessed by colorimetric analysis. The effects of soil burial on the developed composites were also studied for different time periods of 3, 6 and 12 months. Thermal properties, in terms of oxidation stability, thermal stability and dynamic mechanical properties, were determined by differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical analysis, respectively. The results obtained from colorimetric analysis indicated that increasing the bamboo fiber loading in the formulation of hybrid composites induced higher total colour changes. The biodegradability of hybrid composites at higher kenaf loading increased as the soil burial period was longer. Overall, soil burial has led to more pronounced degradation, as compared to accelerated weathering, in terms of oxidation stability, thermal stability and dynamic mechanical properties. The findings of this work reveal that the hybrid composite formulation B:K:50:50 presents a balance of resistance to environmental effects, while maintaining the biodegradability characteristic, which makes it suitable for its use as a potential biocomposite material for structural applications.

The Eneolithic Burial of Maksimovka I Soil Burial Ground from the Samara Trans-Volga Region

Introduction. In the early 1980s the materials of soil burial grounds served as a base for identifying a special Eneolithic period in the history of the Middle and Lower Volga regions. Gathering of source basis on burial Eneolithic complexes is being effected rather slowly. Due to this fact the publication of new information on burial complexes of the Copper Age is quite urgent. This article enters the materials found during the excavations on Maksimovka I soil burial ground situated within the Samara river basin into scientific life. Methods. The collective burial on Maksimovka I burial ground consisted of three or probably four skeletons. They were supine, their legs bent at the knees and their heads oriented towards the North-East. Grave goods included a bone tool, a pressure tool, a sandstone pendant, flint scrapers and a borer, arrowheads with straight or emarginated foundation. Results. While comparing the burial rite with materials of other Eneolithic burial grounds one can see the greatest similarity in the complexes of the Khvalynsk Eneolithic culture (the presence of collective burials, supine position of skeletons with bent legs, orienting the buried people’s heads towards the North-East). Leaf-like arrowheads with narrowed bases and a cavity on the foundation were used in a wide range of activities in the Eneolithic period and Early Bronze Age in the Volga-Don interfluve. However they are typical for Caspian and Altatin complexes in the steppe area of the Volga region. Discussion. In accordance with the latest radiocarbon dates concerning the Eneolithic materials of soil burial grounds and settlement monuments one should date the burial on Maksimovka soil burial ground tentatively 5200–4500 BC.