C.U. Emenike

Distribution and importance of microplastics in the marine environment: A review of the sources, fate, effects, and potential solutions

The presence of microplastics in the marine environment poses a great threat to the entire ecosystem and has received much attention lately as the presence has greatly impacted oceans, lakes, seas, rivers, coastal areas and even the Polar Regions. Microplastics are found in most commonly utilized products (primary microplastics), or may originate from the fragmentation of larger plastic debris (secondary microplastics). The material enters the marine environment through terrestrial and land-based activities, especially via runoffs and is known to have great impact on marine organisms as studies have shown that large numbers of marine organisms have been affected by microplastics. Microplastic particles have been found distributed in large numbers in Africa, Asia, Southeast Asia, India, South Africa, North America, and in Europe. This review describes the sources and global distribution of microplastics in the environment, the fate and impact on marine biota, especially the food chain. Furthermore, the control measures discussed are those mapped out by both national and international environmental organizations for combating the impact from microplastics. Identifying the main sources of microplastic pollution in the environment and creating awareness through education at the public, private, and government sectors will go a long way in reducing the entry of microplastics into the environment. Also, knowing the associated behavioral mechanisms will enable better understanding of the impacts for the marine environment. However, a more promising and environmentally safe approach could be provided by exploiting the potentials of microorganisms, especially those of marine origin that can degrade microplastics. CAPSULE The concentration, distribution sources and fate of microplastics in the global marine environment were discussed, so also was the impact of microplastics on a wide range of marine biota.

Characterization and toxicological evaluation of leachate from closed sanitary landfill

Landfilling is a major option in waste management hierarchy in developing nations. It generates leachate, which has the potential of polluting watercourses. This study analysed the physico-chemical components of leachate from a closed sanitary landfill in Malaysia, in relation to evaluating the toxicological impact on fish species namely Pangasius sutchi S., 1878 and Clarias batrachus L., 1758. The leachate samples were taken from Air Hitam Sanitary Landfill (AHSL) and the static method of acute toxicity testing was experimented on both fish species at different leachate concentrations. Each fish had an average of 1.3 ± 0.2 g wet weight and length of 5.0 ± 0.1 cm. Histology of the fishes was examined by analysing the gills of the response (dead) group, using the Harris haemtoxylin and eosin (H&E) method. Finneys’ Probit method was utilized as a statistical tool to evaluate the data from the fish test. The physico-chemical analysis of the leachate recorded pH 8.2 ± 0.3, biochemical oxygen demand 3500 ± 125 mg L−1, COD 10 234 ± 175 mg L−1, ammonical nitrogen of 880 ± 74 mg L−1, benzene 0.22 ± 0.1 mg L−1 and toluene 1.2 ± 0.4 mg L−1. The 50% lethality concentration (LC50) values calculated after 96 h exposure were 3.2% (v/v) and 5.9% (v/v) of raw leachate on P. sutchi and C. batrachus, respectively. The H&E staining showed denaturation of the nucleus and cytoplasm of the gills of the response groups. Leachate from the sanitary landfill was toxic to both fish species. The P. sutchi and C. batrachus may be used as indicator organisms for leachate pollution in water.

Remediation of Contaminated Sites

Oil pollution in the environment is now being taken seriously by the oil industries and as such, these companies are always looking for cost-effective methods of dealing with this pollution. The global environment is under great stress due to urbanization and industrialization as well as population pressure on the limited natural resources. The problems are compounded by drastic changes that have been taking place in the lifestyle and habits of people. The environmental problems are diverse and sometimes specific with reference to time and space. The nature and the magnitude of the problems are ever changing, bringing new challenges and creating a constant need for developing newer and more appropriate technologies.

Remediation of Oil Contaminated Media Using Organic Material Supplementation

With the fact that anthropogenic activities are inevitable, especially with the continuous use of fossil fuels and other sources of hydrocarbons, environmental pollution appears to be a recurring issue. However, nascent science and technologies try to identify and apply varied options that can remedy polluted sites, which include oil spill situations. The present review elucidates the remediation options on the event of oil spill/contamination with emphasis on the adoption of biological treatment (supplement addition and phytoremediation), and overview on the potential relevance of remediation via advances in nanotechnology. The associated negativities and cost tend to outweigh the advantages of both methods when sustainability is considered.

Growth kinetics and biodeterioration of polypropylene microplastics by Bacillus sp. and Rhodococcus sp. isolated from mangrove sediment

Interest in the biodegradation of microplastics is due to their ubiquitous distribution, availability, high persistence in the environment and deleterious impact on marine biota. The present study evaluates the growth response and mechanism of polypropylene (PP) degradation by Bacillus sp. strain 27 and Rhodococcus sp. strain 36 isolated from mangrove sediments upon exposure to PP microplastics. Both bacteria strains were able to utilise PP microplastic for growth as confirmed by the reduction of the polymer mass. The weight loss was 6.4% by Rhodococcus sp. strain 36 and 4.0% by Bacillus sp. strain 27 after 40days of incubation. PP biodegradation was further confirmed using Fourier-transform infrared spectroscopy and scanning electron microscopy analyses, which revealed structural and morphological changes in the PP microplastics with microbial treatment. These analyses showed that the isolates can colonise, modify and utilise PP microplastics as carbon source.

Assessing the bioaugmentation potentials of individual isolates from landfill on metal-polluted soil

Heavy metals from leachate are persistent pollutants in soil, especially when landfills lack liners and basic structural system that prevents overflow of leachate beyond restricted areas. It is not ideal to rely only on physical and chemical options for the reclamation/restoration of such contaminated soil. Therefore, it is imperative to adopt bioremediation through the enhancement of microbial potentials. The present study investigated the use of individual isolates for the remediation of soil contaminated by leachate-metals. This is a way to understand the discrete potentials of the gram-positive bacteria species. Environmental isolates taken from contaminated soil were used to remedy soil characterized with various concentrations of metals (Al, Cd, Cr, Fe, Ni, Pb and Zn). Treatments A, B, and C amended with Bacillus sp., Lysinibacillus sp., and Rhodococcus sp., respectively, demonstrated better metal reduction potentials than the control experiment (Treatment D; zero microbial amendment) that depended solely on natural attenuation. With the exception of Ni, the degree of reduction of other metals was less than 50% for all treatments. This study suggests that such result reflects the potential ability of the microbes to metabolize selectively in the presence of metal pollution. However, it is difficult for the individual microbes to attain higher metal reduction efficiency (above 50%) except when blended in the appropriate formulation.

Restoration of Environment Through Phytoremediation

Environmental restoration is a phenomenon required to keep the ecosystem intact, or enhance the rejuvenation of impaired environmental media; soil, water and air. Various methods of remediation exist, yet restoring the environment to the proximal or original state appear elusive to most methods. Interestingly, phytoremediation which is a biological process does not only restore environment in a greener way, but also can adopt diverse mechanisms such phytoextraction, phytodegradation, rhizodegrdation, phytostabilization and phytovolatization, to achieve the desired outcome. The chapter also unlined the merits and a few demerits of this principle, while the identification of sustainable plants and the mitigation of time constraints were the future directions mentioned for the projection of phytoremediation as the ideal approach for the restoration of the environment.

Effect of Interaction between Earthworm and Microbes on the Degradation Time of Agro-Waste

Impact of macro-organisms in biological processes had been considerably studied but some of the discrete interactions that exist between macro- and micro-organisms still remain complex and sometimes elusive. Agro-waste is a type of waste that remains highly inevitable in our society and its disposal is a subject of concern. Therefore, this study aimed to degrade sugarcane bagasse which is a significant agro-waste in Malaysia, while trying to understand the interaction between microbes and earthworm utilized in the bioprocess. Sugarcane bagasse was blended with spent tea in equal ratio before composting with the aid of Eudrilus eugeniae and introduced microbial consortia. Though varied, pH values across the amendments tended towards alkaline state, just as the available Phosphorus (P) and exchangeable Potassium (K) increased in the value. Total organic carbon (TOC) across the amendments showed reduction in value; 47% in TS (tea and sugarcane bagasse), whereas 25% in TS6M (Tea + sugarcane bagasse + 6 microbes) and 68% in TS3M (tea bagasse + 3 microbes). However, weight loss in Eudrilus eugeinae was found to be proportional to the reduced time of degradation. TS3M at 33% worm weight loss was recorded at 11 day degradation time, than TS6M (27%) and TS (16%) that showed 13 and 20 days degradation time respectively. Weight loss in earthworm is correlated with microbial interaction and can be a reflection of rate decomposition of organic components of agro-waste in a vermicomposting process.