Plastic products with tremendous consumption are ubiquitous in our daily lives and the annual production of plastics is drastically increasing [1]. It is now expected to reach 33 billion tonnes by 2050 [2] with plastic waste in the environment projected to reach 67.8 million metric tons by the same year [3]. The pollution of plastic cum microplastics (MPs) from degradation in the environment is currently a hot issue attracting the global attention of many scientists, governmental and non-governmental organization and the public media [3-7]. Although few studies have investigated the chemical behavior and toxicity of MPs in the natural environment, studies focusing on its toxicity in tandem with toxic chemicals to ecosystems are scarce [1,4,8]. There are many toxicology reports that MPs are harmful to ecosystems. Terrestrial organisms such as earthworms, soil collembolans, and other animals, as well as plants have been affected by MPs [1,4,9-13]. Also, aquatic organisms such fish, sandhoppers, sea turtle, crustacean and mussel have also been affected by MPs [14-15]. In addition, humans are exposed to MPs via trophic transfer or by direct ingestion, contact and inhalation and plausible effects include lung inflammation and genotoxicity may occur [1,3,16,17]. Aside from the innate toxicity of MPs, they can carry different toxic chemicals such as heavy metals and organic pollutant by adsorption process, and double the effect of such pollutants [1,8,18]. Succinctly, plastic products are made up of mixtures of polymers, fillers, and multiple additives to improve its usability. Also, there are other chemicals including unreacted monomers, starting substances and non-intentionally added substances (NIAS; impurities, side or breakdown products) that are also present in plastic. However, most of these chemicals are not covalently bound to the polymer, so they can be released at all stages of the plastics' life cycle via migration to liquids or solids or via volatilization [1]. Therefore, plastic materials are an important source of human exposure to chemicals.

Soils of different types affect crop production according to their capability as a nutrient supplier based on plant requirement. Soil provides physical support to plant as well as supplies necessary water and nutrient elements for plant growth and development. Suitable soil for stevia cultivation in Bangladesh is yet to be identified. A high concentrate sweetness producer plant, stevia (Stevia rebaudiana Bertoni) was grown in earthen pots in some soils of Bangladesh to choose the most suitable soil/s for the growth and leaf yield of stevia. Seven soil types namely acid, calcareous, non-calcareous, charland, saline, peat and acid sulphate were used as treatments. The soils were mostly light grey in colour and clay to clay loam in texture. Bulk density, particle density and field capacity ranged from 1.24-1.45, 2.20-2.58 and 27.03-30.19%, respectively. pH, EC and organic matter content ranged from 3.90-8.00, 0.25-14.00 dS m -1 and 0.88-16.40%, respectively. Total N, exchangeable K, available P and S contents ranged from 0.05-0.96%, 0.17-0.70 cmol kg -1 soil, 3-12 and 11-735 µg g -1 soil, respectively. Different soil types significantly influenced the growth and leaf yield of stevia. The highest values of plant height, branch and leaf number, leaf area, fresh and dry weight of leaves were obtained from the plant grown in non-calcareous soil which was identical with the plant those grown on acid soil while the lowest values of all the parameters were found from the plant grown in acid sulphate soil. Leaf biomass yield increase ranged from 16.18% in peat soil and 90.11% in non-calcareous soil over acid sulphate soil. The performance of the soils in terms of stevia leaf production was of the order non-calcareous> acid> calcareous> charland> saline(4.43 dS m -1 )> saline(6.08 dS m -1 )> saline(8.68 dS m -1 )> peat >acid sulphate soils. The overall results suggest that farmers could be advised to grow stevia either in non-calcareous soil or acid soils of Bangladesh.

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Because of its slow rate of disintegration, plastic debris has steadily risen over time and contributed to a host of environmental issues. Recycling the world’s increasing debris has taken on critical importance. Pyrolysis is one of the most practical techniques for recycling plastic because of its intrinsic qualities and environmental friendliness. For scale-up and reactor design, an understanding of the degradation process is essential. Using one model-free kinetic approach (Friedman) and two model-fitting kinetic methods (Arrhenius and Coats-Redfern), the thermal degradation of Polyethylene Terephthalate (PET) microplastics at heating rates of 10, 20, and 30 °C/min was examined in this work. Additionally, a powerful artificial neural network (ANN) model was created to forecast the heat deterioration of PET MPs. At various heating rates, the TG and DTG thermograms from the PET MPs degradation revealed the same patterns and trends. This showed that the heating rates do not impact the decomposition processes. The Friedman model showed activation energy values ranging from 3.31 to 8.79 kJ/mol. The average activation energy value was 1278.88 kJ/mol from the Arrhenius model, while, from the Coats-Redfern model, the average was 1.05 × 104 kJ/mol. The thermodynamics of the degradation process of the PET MPs by thermal treatment were all non-spontaneous and endergonic, and energy was absorbed for the degradation. It was discovered that an ANN, with a two-layer hidden architecture, was the most effective network for predicting the output variable (mass loss%) with a regression coefficient value of (0.951–1.0).

Nitrogen is recognized as one of the most limiting nutrient for crop growth in Bangladesh and can be supplemented with inorganic fertilizers like urea. The experiment was conducted in the net house of the Department of Agricultural Chemistry, Bangladesh Agricultural University during March to July 2012. The objective was to examine the effects of different levels of N on the growth, leaf biomass yield, N content and to estimate minimum N requirement and critical N content of stevia. The treatments included six N rates (0, 100, 150, 200, 250 and 300 kg ha -1 ). Plant sampling was done at 15, 30, 45 and 60 days after planting (DAP) to measure plant height, number of branches and leaves, fresh and dry weight of leaves, leaf area and N concentration. The results revealed that all the characters were significantly affected by different N rates. The highest values of all parameters except plant height and N concentration were obtained from 250 kg N ha -1 and the lowest values from N control. Nitrogen application at all levels increased leaf dry yield at harvest by 99 to 505% in acid soil and 69 to 438% in noncalcareous soil, respectively over control. The growth of most parameters was rapid at the later stages (30 to 60 DAP). Leaf N content proportionately increased with the increasing rates of N. The highest N concentration was obtained from its highest application (300 kg N ha -1 ). The minimum amount of N for maximum leaf biomass production in the plants grown in acid and non-calcareous soils was estimated to be ca 273 and 257 kg ha -1 , respectively. The critical N concentration to achieve 80% of the maximum production of stevia leaf was also estimated to be ca 1.43 and 1.50% in the leaves of stevia plants grown in acid and non-calcareous soils, respectively.