Philip Nti Nkrumah

Chemical Behavior of Phthalates Under Abiotic Conditions in Landfills

The phthalates comprise a family of phthalic acid esters that are used primarily as plasticizers in polymeric materials to impart flexibility during the manufacturing process and to the end product. It is estimated that the annual worldwide production of phthalate esters exceeds five million tons. Plasticizers are one of the most prominent classes of chemicals, but unfortunately, they possess endocrine-disrupting chemical properties. As endocrine-disrupting chemicals, plasticizers have produced adverse developmental and reproductive effects in mammalian animal models.Phthalates are easily transported into the environment during manufacture, disposal,and leaching from plastic materials, because they are not covalently bound to the plastics of which they are a component. Because of their fugitive nature and widespread use, the phthalates are commonly detected in air, water, sediment/soil, and biota, including human tissue. Large amounts of phthalic acid esters are often leached from the plastics that are dumped at municipal landfills.Phthalate esters undergo chemical changes when released into the environment.The primary processes by which they are transformed include hydrolysis, photolysis,and biodegradation. It is noteworthy that all of these degradation processes are greatly influenced by the local physical and chemical conditions. Hence, in the present review, we have sought to ascertain from the literature how the phthalate esters undergo transformation when they are released into lower landfill layers.Within the upper landfill layers, biodegradation prevails as the major degradation mechanism by which the phthalates are dissipated. Generally, biodegradation pathways for the phthalates consist of primary biodegradation from phthalate diesters to phthalate monoesters, then to phthalic acid, and ultimately biodegradation of phthalic acid to form C02 and/or CH4• We have noted that the phthalate esters are also degraded through abiotic means,which proceeds via both hydrolysis and photolysis. Photodegradation generally involves reactions of the phthalates in the atmosphere with hydroxyl radicals. The hydrolysis of phthalate diesters produces the corresponding monoesters, which are subsequently converted to phthalic acid. Phthalic acid has been observed to accumulate within landfill zones where phthalate contamination exists.Hydrolysis is usually not an important fate process for phthalate esters in the environment, including in upper landfill layers. However, the conditions prevalent at lower landfill layers are generally suitable for phthalate transformation via hydrolysis.The conditions in this zone include high temperatures and pressures, presence of chemical catalysts, as well as wide pH fluctuations. Such conditions foster hydrolysis that may be either acid- or base-catalyzed by metal ions, anions, or organic materials catalysts. In addition, research indicates that the propensity for ongoing hydrolysis increases as landfill depth increases.We can be emphatic in asserting that hydrolysis of phthalate esters in lower landfill layers is the dominant process for transforming these esters; in contrast,biodegradation is the predominant process in the upper landfill layers.We recommend that future research be performed to expand the understanding of what influence each reaction condition (high temperature, presence of chemical catalysts, etc.) has on the rate of chemical transformation of the phthalates in lower landfill zones. We also recommend that the combined effects of all conditions on the rate of chemical transformation at lower landfill layers be assessed for the phthalates.Such research could be achieved under simulated conditions.

Different tolerances to chemical contaminants between unicellular and colonial morph of Microcystis aeruginosa: Excluding the differences among different strains

In order to ascertain the different tolerances to chemical contaminants in one strain of Microcystis with different morphology, unicellular and colonial Microcystis in one strain was obtained from different conditions of light intensity and temperature. The samples were divided into 8 groups including control (no chemical addition), CuSO4, chloromycetin, and linear alkylbenzene sulfonatelas (LAS) treatments. The cell density, cell viability, superoxide dismutase (SOD), and malonaldehyde of Microcystis were analyzed. It was observed that cell density of both unicellular and colonial Microcystis increased from the beginning to day-5 in the control and the CuSO4 treatments. However, the growth of Microcystis was significantly inhibited in the culture with chloromycetin and LAS treatments. Notably, the inhibition rate was significantly high in unicellular Microcystis relative to the colonial Microcystis. The esterase activity in all the treatments decreased dramatically relating to the control. In addition, the esterase activity in colonial Microcystis was significantly higher than that of the unicellular Microcystis in all the treatments. Although there were no significant differences in activities of SOD between the two morphologies in the control treatments, in all the other treatments, significant differences were observed. The results proved that colony formation of Microcystis could be considered as a strategy in response to chemical stress.

Biochemical composition of Microcystis aeruginosa related to specific growth rate: insight into the effects of abiotic factors

Abstract The content of different Microcystis biochemical components, including total polysaccharides (TPS), proteins, and RNA, were analyzed at different growth rates obtained under varying light intensities, temperatures, and nutrient concentrations. Higher light intensity and temperature yielded a higher specific growth rate of Microcystis, but the 2 different culture media did not significantly affect growth of Microcystis in the current study. The differences in the cellular content of TPS, protein, and RNA at different temperatures (20 and 25 °C) were significant under both light intensities. The differences under different light intensities (30 and 60 μmol photons m−2 s−1) were significant at 25 °C but negligible at 20 °C. These phenomena suggested that temperature would be the limiting factor influencing the cellular processes when temperature was 20 °C; however, when temperature was 25 °C, the limiting factor was observed to be light intensity. The results also demonstrated that the content of TPS and RNA decreased, but the value of proteins increased with an increase in specific growth rate

Comparative Studies on E-Waste Disposal Practices in Developing Countries and their Environmental Effects: An Example between Guiyu, China and Agbogbloshie, Ghana

E-waste disposal continues to be one of the major environmental concerns across the globe. The method of disposal varies from one region to another. In developing countries, the primitive methods that are employed during the recycling activity pose severe risks to public health and the environment at large. The present study was carried out to ascertain the current practices in Guiyu and Agbogbloshie. The environmental effects of these activities were also evaluated. Prudent solutions were finally proposed. Data were extracted from peer-reviewed articles, books, and reports identified using Web of ScienceSM, PubMed, Google, and document reference lists. The study indicated that the quantities of e-waste that are dumped in the respective areas are rising at an escalating rate despite a ban on the importation of this waste type. The crude methods that are adopted in both areas include manual dismantling, open burning as well as indiscriminate dumping. These activities were observed to release huge chemical contaminants into the air, water and soil. This has dire impact on the environment. The study proposed that to help curb the menace, appropriate measures must be ensured. These include the integration of the informal recycling sector into the formal sector through capacity building of the informal recyclers. Effective recycling systems must also be adopted to minimize the effects on public health and the environment. Strict regulations must also be implemented since the ban is already in place in the areas under consideration. This study adds to the effort already in place to address the issue. Considering the acute paucity of data on the e-waste practices in the respective areas especially on the amount generated as well as the environmental effects, this topic may merit further studies.

Elucidating the origin of milk products on the Chinese market using hydrogen and oxygen stable isotope technique

Preference for foreign milk products is the cause of the economically motivated adulteration of milk products on the Chinese market. 42 milk samples from the United States of America, Canada, Southern China, Northern China, Australia and New Zealand were analyzed using δ2H and δ18O stable isotope technique to differentiate the origin of milk products. An isotope ratio mass spectrometer with a combination of a high-temperature conversion elemental analyzer, Thermo-Fisher was used. Statistical analysis was performed using one-way ANOVA. The study revealed δ2H and δ18O had a wide range of mean values: 13.86 to 22.25‰ and -82.86 to -28.5‰, respectively. There was a significant difference in the δ2H (n=7; F=20880, P=7.876E-43) and δ18O (n=7; F=1399.0; P=9.215E-29) composition of the milk samples from the different regions. It was observed that δ2H and δ18O composition is helpful in elucidating milk products from different regions on the Chinese market (P<0.05).