Model-based analysis of urban settlement process in eco-sensitive area of developing country: a study with special reference to hills of an Indian city

Rapid and unplanned expansion of a city into its eco-sensitive areas like hills, wetlands, and forests is becoming a major concern, particularly in developing countries. Understanding the process and causes of such unplanned urban expansion is of paramount importance for framing sustainable urban development policies. This paper presents a modelling concept that relates urban settlement in such eco-sensitive areas with potential socio-economic, demographic and geographical factors. The model is applied to an Indian city Guwahati, which is experiencing serious environmental degradation due to unplanned urban settlement in its eco-sensitive hilly areas. While topographical and settlement data were derived using satellite data in GIS platform, all other necessary data were collected from relevant government organizations. On validation of the multi-linear regression model, the coefficient of determination and the root mean square error are obtained as 0.938 and 1.7, respectively. Model results show that geographical parameters are less influencing as compared to the other socio-economic and demographic factors. Sensitivity analysis of urban settlements in hills of Guwahati city carried out with respect to the considered factors reveals that land value and free space availability in the surrounding area of a hill are the most sensitive parameters. This indicates that city development plans should give more importance to outward spatial expansion in plain areas with regulated land value and zoning scheme to minimize unauthorized settlement in eco-sensitive hilly areas of Guwahati city.     

Production of Curdlan Grown on Cassava Starch Waste Hydrolysates

Cassava starch waste hydrolysates (CSWHs) with different degrees of polymerisation, i.e., CSWHs-1, CSWHs-2 and CSWHs-3, were prepared through the hydrolysis of cassava starch waste with thermostable a-amylase from Thermococcus sp. HJ21. The prepared CSWHs were then used as a carbon source for curdlan production with Alcaligenes faecalis ATCC 31749. The amount of curdlan produced and the glucosyltransferase activity during curdlan synthesis increased more obviously when CSWHs-2 was used as the carbon source than when glucose was used. Using both carbon sources, the maximum curdlan production was observed at day 5, and the maximum glucosyltransferase activity was observed at day 4. Glucosyltransferase activity decreased thereafter, and biomass continued to increase until the end of the experiment (day 6). Results indicated that the enhanced curdlan production with CSWHs as the carbon source was highly correlated with glucosyltransferase activity.     

Biodegradability and Thermal Properties of Novel Natural Rubber/Linear Low Density Polyethylene/Thermoplastic Starch Ternary Blends

This work aimed to prepare biodegradable thermoplastic elastomers based on NR/LLDPE/TPS ternary simple blends to achieve some exclusive properties, i.e., good biodegradability in terms of water absorption and weight loss after burial, together with reasonable mechanical and thermal properties. A comparative study on biodegradability and other related properties of NR/LLDPE binary and NR/LLDPE/TPS ternary blends was performed. It was found that increasing the TPS proportion decreased storage modulus and complex viscosity. In addition, the size of dispersed TPS domains in the NR/LLDPE co-continuous matrix increased with TPS proportion, while the mechanical properties in terms of 100% moduli, tensile strength, elongation at break, and hardness decreased. This might be attributed to decreased interfacial adhesion with increasing size of TPS domains. Furthermore, increasing the TPS loading in the blend reduced the temperatures for 5 or 50% mass loss (T₅ or T₅₀) and the degradation temperature (T _d ). However, the biodegradability improved, in terms of increased water absorption and weight loss after burial in soil, with the loading level of TPS.     

Biopolymer (Chitin) from Various Marine Seashell Wastes: Isolation and Characterization

Chitin has been produced from different sea waste sources including, molluscs (mussel and oyster shell), crustacean (prawn and crab) and fish scale (pang and silver scales) using deproteinization and demineralization as chemical methods. The conditions of chemical extraction process determine the quality of chitin. The obtained results revealed that, about 1 and 10% HCl and NaOH were adequate concentrations for deproteinization and demineralization process respectively. Chitin from oyster and crab shell waste had the highest yield of 69.65 and 60.00% while prawn, mussel shell, pang and silver scales had the lowest yield of 40.89, 35.03, 35.07 and 31.11% respectively. Chitin solubility is controlled by the quantity of protonated acetyl groups within the polymeric chain of the chitin backbone, thus on the percentage of acetylated and non-acetylated d-glucos-acetamide unit. Good solubility results were obtained in mussel, oyster and crab shells respectively. The chitin molecular weight characteristics and activity are controlled by the degree of acetylation (DA) and the distribution of acetyl group extending in the polymer chain. DA is determined by acid-base titration methods and molecular weight determined by Brookfield viscometry. Both methods are found to be effective.     

PCDD/PCDF formation in the chlor-alkali process—laboratory study and comparison with patterns from contaminated sites

Studies on the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) during the electrolysis of sodium chloride solution (brine) using graphite or titanium electrodes were carried out at a laboratory scale. High concentrations of PCDFs but no PCDDs were formed in tests using graphite electrodes. With titanium electrodes, PCDFs were only formed when tar pitch was added and mainly originated from the dibenzofuran present in the tar. For the first time, a detailed assessment of the formation of mono- to octachlorinated PCDD/PCDF from tar pitch was investigated. The assessment included of the chlorination steps proved that PCDFs were formed by successive lateral chlorinated from dibenzofuran to MonoCDFs, DiCDFs, and TriCDFs to form the typical known “chlorine pattern” of TetraCDF to OctaCDF with a dominance of 1,2,7,8- and 2,3,7,8-TetraCDFs, 1,2,3,7,8-PentaCDF, and 1,2,3,4,7,8-HexaCDF as marker congeners. The final homologue distributions depended on reaction time and reaction temperature. In addition, electrolysis with non-chlorinated dibenzo-p-dioxins, dibenzofuran, and biphenyl was carried out. As a result, PCDDs, PCDFs, and PCB were formed at comparable yields. Congener patterns in soil samples from a PCDD/F-contaminated site where chlor-alkali electrolysis had been operated for decades in Japan had identical isomer distribution demonstrating the source and contamination potential and risk of these processes. Therefore, sites where in the past 120 years chlor-alkali electrolysis has been operated or where residues from chlor-alkali production or other chlorine using industries have been disposed should be assessed for their pollution level and exposure relevance. The assessment of total organohalogen content revealed that PCDF is only a small fraction of organohalogens in the contaminated soils. For an appropriate risk assessment, also other chlorinated aromatic compounds such as PCBs or PCNs need to be considered.     

Treatment technologies for PAH-contaminated sites: a critical review

To reduce environmental and human health risks of contaminated sites, having a comprehensive knowledge about the polycyclic aromatic hydrocarbon (PAH) removal processes is crucial. PAHs are contaminants which are highly recognized to pose threats to humans, animals, and plants. PAHs are hydrophobic and own two or more benzene rings, and hence are resistant to structural degradation. There are various techniques which have been developed to treat PAH-contaminated soil. Four distinct processes to remove PAHs in the contaminated soil, thought to be more effective techniques, are presented in this review: soil washing, chemical oxidation, electrokinetic, phytoremediation. In a surfactant-aided washing process, a removal rate of 90% was reported. Compost-amended phytoremediation treatment presented 58–99% removal of pyrene from the soil in 90 days. Chemical oxidation method was able to reach complete conversion for some PAHs. In electrokinetic treatment, researchers have achieved reliable results in removal of some specific PAHs. Researchers’ innovations in novel studies and advantages/disadvantages of the techniques are also investigated throughout the paper. Finally, it should be noted that an exclusive method or a combination of methods by themselves are not the key to be employed for remediation of every contaminated site but the field characteristics are also essential in selection of the most appropriate decontamination technique(s). The remedy for selection criteria is based on PAH concentrations, site characteristics, costs, shortcomings, and advantages.     

Salinity evolution of the Tigris River

Major modifications regulating the Tigris River, originated in the 1940s and continuing to the present, have resulted in changes in salinity in the system over time and in different portions of the river course. The increase in salinity is due to decreases in stream discharge due to dams, water management structures such as the Lake Tharthar system, irrigation return flow, and soluble minerals in the basin. This research documents the increase and evaluates the causes of the salinity increase of the river from predevelopment to present using published and previously unavailable data. The predevelopment salinity was under 600 ppm, since 1984 has exceeded the 1000 ppm threshold recommended for drinking water downstream of Amara. A minimum instream flow for the river is calculated at Baghdad and Kut at 185 cubic meters per second (cms), approximately 15% of the mean historical flow of the river, but above the lowest minimum flow recorded at 140 cms. Recommended salinity management options discussed include (1) eliminating Lake Tharthar as a water storage facility, (2) managing saline inflows from tributaries, and (3) employing a minimum instream flow for the river.     

Gasification characteristics of biomass for tar removal by secondary oxidant injection

Gasification experiments for sawdust were conducted using a fixed bed reactor at 900 °C by varying the secondary oxidant injection ratio to determine the optimal conditions for tar removal along with the enhancement of gasification efficiency. Secondary oxidant was injected as an oxidant at the top zone of the gasifier in varying ratios of 10–30% of the total amount of oxidant. This method was based on the primary method of tar removal and gasification efficiency improvement by thermal cracking of tar. Various gasification performance parameters were evaluated and tar content was estimated by measuring the fluctuation of weight of the activated carbon filter. The results showed that the concentration of tar in the producer gas decreased by injecting the secondary oxidant, even though syngas yield decreased. The recycling potential of the char produced in the gasification experiments was also assessed with the purpose of utilizing char as an adsorbent by determining its surface area and pore volume. The results demonstrated that the char produced from the gasification experiment had similar quality to that of the activated carbon used in this experiment.     

Environmental Impact Assessment of Polylactide(PLA)/Chicken Feathers Biocomposite Materials

The aim of this study is to analyse the environmental impacts (EIs) of the process of preparation of new biocomposite materials obtained from polylactide (PLA) and chicken feathers (CFs). Two CFs stabilization methods and different percentages of CFs have been studied. The EIs of these new composites were compared to the impact of virgin PLA. Cradle-to-gate life cycle inventories were assessed for 0–35% v/v of CFs in a CFs/PLA biocomposite. Two CFs stabilization processes, autoclave and surfactant, were tested and compared with the aim to prioritize one of them from the environmental point of view. A composite plate of 184?×?184?×?2.2 mm³ was defined as the functional unit. Autoclave stabilization process exhibited lower environmental impact compared with surfactant stabilization process mainly due to both the lower requirements of electricity and water and the reduced pollution loads of the generated wastewater. Thus, the autoclave process was selected as the standard method when comparing the EIs of the proposed CFs/PLA biocomposites. In this sense, the addition of CFs to PLA matrix proportionally reduces all the EIs compared to pure PLA due to the replacement of PLA with CFs. This behaviour can be explained because the PLA production accounts for the 99% of the impact of the biocomposite. Consequently, CFs conveniently stabilized might be an alternative raw material to prepare CFs/PLA biocomposites with less environmental impact compared to pure PLA.     

Adsorption of Ammonium by Graphene Oxide-Based Composites Prepared by UV Irradiation and Using as Slow-Release Fertilizer

A novel sodium alginate-grafted poly(acrylic acid)/graphene oxide (NaAlg-g-PAA/GO) composite hydrogel was prepared via ultraviolet irradiation, and characterized by infrared spectroscopy spectrometer. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. It was employed to adsorb NH₄⁺ from aqueous solution and used as slow-release nitrogen fertilizers (SNFs). Result indicated that the adsorption process for NH₄⁺ reached equilibrium within 50 min, with the adsorption capacity of 6.6 mmol g^?1 even if 30 wt% GO was incorporated. The results of adsorption kinetic and isotherm were well described by the pseudo-second-order and Freundlich model. The thermodynamics analysis showed the adsorption process was spontaneous. The study indicated excellent water-holding ratio of soil with 2 wt% SNFs was 81.2%, and nitrogen release was up to 55.1% within 40 days in soil. Overall, NaAlg-g-PAA/GO could be considered as an efficient adsorbent for the recovery of nitrogen with the agronomic reuse as a fertilizer.