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Microplastics are emerging as a steadily increasing environmental threat. Wastewater treatment plants efficiently remove microplastics from sewage, trapping the particles in the sludge and preventing their entrance into aquatic environments. Treatment plants are essentially taking the microplastics out of the waste water and concentrating them in the sludge, however. It has become common practice to use this sludge on agricultural soils as a fertilizer. The aim of the current research was to evaluate the microplastic contamination of soils by this practice, assessing the implications of successive sludge applications by looking at the total count of microplastic particles in soil samples. Thirty-one agricultural fields with different sludge application records and similar edaphoclimatic conditions were evaluated. Field records of sludge application covered a ten year period. For all fields, historical disposal events used the same amount of sludge (40 ton ha−1 dry weight). Extraction of microplastics was done by flotation and particles were then counted and classified with the help of a microscope. Seven sludge samples were collected in the fields that underwent sludge applications during the study period. Soils where 1, 2, 3, 4, and 5 applications of sludge had been performed had a median of 1.1, 1.6, 1.7, 2.3, and 3.5 particles g−1 dry soil, respectively. There were statistical differences in the microplastic contents related to the number of applications that a field had undergone (1, 2, 3 < 4, 5). Microplastic content in sludge ranged from 18 to 41 particles g−1, with a median of 34 particles g−1. The majority of the observed microplastics were fibers (90% in sludge, and 97% in soil). Our results indicate that microplastic counts increase over time where successive sludge applications are performed. Microplastics observed in soil samples stress the relevance of sludge as a driver of soil microplastic contamination. Unlabelled Image • Sludge holds microplastics that could enter soils by sludge disposal. • 31 fields that underwent sludge applications at different rates were evaluated. • Microplastics were found in soil samples (0.6–10.4 p g−1). • Microplastic counts increased where increased rates of sludge were applied. • Sludge is proposed as a primal driver of soil microplastic pollution. [ABSTRACT FROM AUTHOR]

Highlights • Antarctic bacterial strain So13.3 produces a pigment with DSSC sensitizer activity. • Pigment from Antarctic bacteria can produce energy and is a type of melanin. • Pigment-producing microorganisms from Antarctic can be a source for DSSC use. Abstract The study of bacterial pigment for their application in DSSC is an in-development area of solar energy. However, studies on bacterial pigments for application in solar cells are scarce. We evaluated the use of a pigment obtained from the Antarctic So13.3 bacterial strain as a sensitizer in DSSC. Based on the sequence of the 16S gene, the So13.3 strain was identified as Streptomyces fildesensis. The bacterial pigment was characterized by UV–Vis and Fourier-Transform Infrared Spectroscopy (FTIR). Results indicate that the pigment has very similar characteristics to melanin. DSSC showed the best performance at a concentration of 6500 (μg/mL), obtaining a voltage of 493 [mV], a current density of 0.091 [mA/cm2], 0.026% efficiency and a 0.579 Filling Factor (FF). Considering that there are few studies on bacterial pigments applied in DSSC, we demonstrate the importance of focusing research on pigment-producing microorganism isolation and evaluating their potential use in DSSC. [ABSTRACT FROM AUTHOR]