Enzyme-Retted Flax Fiber and Recycled Polyethylene Composites

Municipal solid wastes generated each year contain potentially useful and recyclable materials for composites. Simultaneously, interest is high for the use of natural fibers, such as flax (Linum usitatissimum L.), in composites thus providing cost and environmental benefits. To investigate the utility of these materials, composites containing flax fibers with recycled high density polyethylene (HDPE) were created and compared with similar products made with wood pulp, glass, and carbon fibers. Flax was either enzyme- or dew-retted to observe composite property differences between diverse levels of enzyme formulations and retting techniques. Coupling agents would strengthen binding between fibers and HDPE but in this study fibers were not modified in anyway to observe mechanical property differences between natural fiber composites. Composites with flax fibers from various retting methods, i.e., dew- vs. enzyme-retting, behaved differently; dew-retted fiber composites resulted in both lower strength and percent elongation. The lowest level of enzyme-retting and the most economical process produces composites that do not appear to differ from the highest level of enzyme-retting. Flax fibers improved the modulus of elasticity over wood pulp and HDPE alone and were less dense than glass or carbon fiber composites. Likely, differences in surface properties of the various flax fibers, while poorly defined and requiring further research, caused various interactions with the resin that influenced composite properties.     

Heavy metal concentrations in two barb, Barbus xanthopterus and Barbus rajanorum mystaceus from Atatürk Dam Lake, Turkey

Concentration of some heavy metals (Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb and Zn) were determined in muscle, liver, kidney and gill of two barb, Barbus xanthopterus and Barbus rajanorum mystaceus, which have great economic values, in the Atatürk Dam Lake (Turkey). Heavy metal levels in fish samples were analyzed by inductively coupled plasma spectroscopy (ICP/OES). Heavy metal concentrations vary significantly, depending on the type of the tissue in fish species. The metal accumulation in the liver, kidney and gill of Barbus xanthopterus and Barbus rajanorum mystaceus was found to be quite high in comparison with that in the muscle. The mean concentrations of heavy metals in muscle tissues of Barbus xanthopterus were as follows: Co, 0.09; Cr, 0.12; Cu, 0.27; Fe, 5.26; Mn, 0.20; Ni, 0.08; Pb, 0.68; Zn, 1.39, whereas in muscle tissues of Barbus rajanorum mystaceus were as follows: Co, 0.11; Cr, 0.10; Cu, 1.07; Fe, 3.97; Mn, 019; Ni, 0.04; Pb, 0.66; Zn, 1.70 microg/g wet weight. Cd levels in gill and muscle tissues were below detection limits. All metal levels detected in tissues were safe for human consumption and within the limits for fish proposed by FAO/ WHO, EU and Turkish Food Codes.     

Green preparation of a novel red mud@carbon composite and its application for adsorption of 2,4-dichlorophenoxyacetic acid from aqueous solution

This study reports the eco-friendly preparation of a novel composite material consisting of red mud and carbon spheres, denoted as red mud@C composite, and its application for the removal of 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from aqueous solution. The preparation route has a green approach because it follows the low-energy consuming one-step hydrothermal process by using starch as a renewable carbon precursor and red mud as a waste from aluminum production industry. Characterization of the red mud@C composite was performed by FT-IR, TGA, SEM, TEM, BET, XRD, and Raman microscopy analyses. The batch adsorption studies revealed that the red mud@C composite has higher 2,4-D adsorption efficiency than those of the red mud and the naked carbon spheres. The maximum removal at initial pH of 3.0 is explained by considering the pKa of 2,4-D and pH of point of zero charge (pH_pzc) of the composite material. The adsorption equilibrium time was 60 min, which followed the pseudo-second-order kinetic model together with intra-particle diffusion model. The isotherm analysis indicated that Freundlich isotherm model better represented the adsorption data, with isotherm parameters of k [15.849 (mg/g) (mg/L)^?1/n] and n (2.985). The prepared composite is reusable at least 5 cycles of adsorption-desorption with no significant decrease in the adsorption capacity.

     

The evolving sedentary lifestyle among nomadic pastoralists in the humid zone of Nigeria: implications for land-use policy

SUMMARY

The humid zone of Nigeria has traditionally been considered unsuitable for extensive cattle production because of the prevalence of tsetse fly. Over the years, nomadic pastoralists, mainly Fulani, from the northern part of the country paid seasonal visits to this zone in search of pasture and water for their cattle during the dry season when the threat of the tsetse menace is less. The recent increase in the number of settled pastoralists has been associated with changing trends in the ecology and economy of the zone.

Relying on recent survey data, this paper attempts a systematic analysis of the adaptive strategies of the Fulani in pursuit of a sedentary lifestyle in the humid frontier of southwest Nigeria. Some of the adaptive strategies identified include: establishment of grazing orbits within a 20 km radius of their settlements, adjustment of herd size and structure, adoption of a multiple livelihood system, production of arable crops and appropriation of traditional social structures and kinship networks for herd management.

Long-term insecure land-holding arrangements, incessant seasonal bush burning for regeneration of pasture by the Fulani and the gradual destruction of the native forest cover are some of the problems arising from the sedentarisation of livestock production in the area. It was observed that the present land-use arrangement, even though it appears to guarantee the pastoralists security of tenure in the short term, is not sustainable in the long run, given the increasing commercialization of land in the area and rapid population growth. It was, therefore, concluded that government should put in place a land redistribution arrangement that will ensure secure land ownership by the Fulani. Development initiatives in the area should also focus on reinforcing those traditional practices of the Fulani that would guarantee a sustainable land-use system in the area.     

A cluster-based decision support system for estimating earthquake damage and casualties

This paper describes a Decision Support System for Disaster Management (DSS-DM) to aid operational and strategic planning and policy-making for disaster mitigation and preparedness in a less-developed infrastructural context. Such contexts require a more flexible and robust system for fast prediction of damage and losses. The proposed system is specifically designed for earthquake scenarios, estimating the extent of human losses and injuries, as well as the need for temporary shelters. The DSS-DM uses a scenario approach to calculate the aforementioned parameters at the district and sub-district level at different earthquake intensities. The following system modules have been created: clusters (buildings) with respect to use; buildings with respect to construction typology; and estimations of damage to clusters, human losses and injuries, and the need for shelters. The paper not only examines the components of the DSS-DM, but also looks at its application in Besiktas municipality in the city of Istanbul, Turkey.     

Movement and feeding activity of red sea urchins (Strongylocentrotus franciscanus) adjacent to a kelp forest

Movement and feeding were studied in a population of red sea urchins, Strongylocentrotus franciscanus (Agassiz, 1863), found within and immediately seaward of a kelp forest offshore from Santa Cruz, California, USA. Mean sea urchin movements varied from 7.5 cm/day inside the kelp forest to over 50 cm/day at 15 and 100 m outside the kelp forest. The percentage of sea urchins feeding decreased from 66% inside the kelp forest to 16 and 15% at 15 and 100 m outside the kelp forest. These data indicate that movement by these sea urchins is a response to a low food supply.     

Biobased Fiber Production: Enzyme Retting for Flax/Linen Fibers

Flax (Linum ustitatissimum L.) is the source of natural fibers that provides biobased products for a variety of existing markets, but considerable processing and cleaning is required. Flax fibers, and bast fibers generally, are produced in the outer regions of the stem between bark and inner core tissues and require retting, which is the microbial separation of fiber from nonfiber tissues, as the first and most limiting stage of processing. Enzyme retting offers a method to overcome disadvantages of the current method, i.e., dew-retting, for high- and consistent-quality fibers with tailored properties for specific applications. Using chemical analyses, microscopy, and microspectroscopy, sites of carbohydrates, aromatics, and waxes plus cutins were identified in flax stems and their relationship to effective enzyme retting determined. Aromatics occur mostly in the inner, core tissues, with the fibers containing only small amounts located sporadically in cell corners of fiber bundles. Therefore, effective retting using enzymes to separate the aromatic-containing tissues from the fibers, but not to degrade aromatic compounds per se, is required. Waxes and cutin in the epidermal regions are effective barriers to enzyme penetration, and mechanical disruption facilitates enzyme penetration into the stems. Pectinases, with chelators to remove Ca⁺⁺ and destabilize pectin molecules, remove matrix compounds holding fibers within the stem and have been used in effective formulations to ret flax stems.     

Analysis of Flax and Cotton Fiber Fabric Blends and Recycled Polyethylene Composites

Manufacturing composites with polymers and natural fibers has traditionally been performed using chopped fibers or a non-woven mat for reinforcement. Fibers from flax (Linum usitatissimum L.) are stiff and strong and can be processed into a yarn and then manufactured into a fabric for composite formation. Fabric directly impacts the composite because it contains various fiber types via fiber or yarn blending, fiber length is often longer due to requirements in yarn formation, and it controls the fiber alignment via weaving. Composites created with cotton and flax-containing commercial fabrics and recycled high-density polyethylene (HDPE) were evaluated for physical and mechanical properties. Flax fiber/recycled HDPE composites were easily prepared through compression molding using a textile preform. This method takes advantage of maintaining cotton and flax fiber lengths that are formed into a yarn (a continuous package of short fibers) and oriented in a bidirectional woven fabric. Fabrics were treated with maleic anhydride, silane, enzyme, or adding maleic anhydride grafted polyethylene (MAA-PE; MDEX 102-1, Exxelor^® VA 1840) to promote interactions between polymer and fibers. Straight and strong flax fibers present problems because they are not bound as tightly within yarns producing weaker and less elastic yarns that contain larger diameter variations. As the blend percentage and mass of flax fibers increases the fabric strength, and elongation generally decrease in value. Compared to recycled HDPE, mechanical properties of composite materials (containing biodegradable and renewable resources) demonstrated significant increases in tensile strength (1.4–3.2 times stronger) and modulus of elasticity (1.4–2.3 times larger). Additional research is needed to improve composite binding characteristics by allowing the stronger flax fibers in fabric to carry the composites load.     

Heavy metal deposition in moss samples from East and South Marmara Region, Turkey

A survey of atmospheric heavy metal deposition in the east and south Marmara region, Turkey was carried out in September 2004. For this purpose, moss samples (Hypnum cupressiforme) were collected in a systematic network of 125 sites. Concentrations of the elements (Al, B, Ba, Ca, Cd, Fe, Co, Cr, Cu, K, Li, Mn, Na, Ni, Pb, Sr, Mg, Ti, and Zn) in the moss were used as an indication of the level of air pollution in the region. Significant differences in heavy metal concentrations, especially for Pb, Cd, Cu, and Zn, were recorded in the moss samples collected around industrialized and heavily populated cities (Istanbul, Bursa, Band?rma, Kocaeli, Biga-?an) and in an abandoned lead-mining area (Bal?kesir-Balya). A map of the spatial distribution of each element in the region was plotted, and enrichment factors were calculated. VARIMAX principal component analysis was applied to the data obtained, and five different components were obtained. The results showed that Pb, Cu, Cd, and Zn derived from anthropogenic and industrial sources while other elements came mostly from natural sources.