Integrated effects of polymer type, size and shape on the sinking dynamics of biofouled microplastics

Sinking of microplastics (MPs) after biofouling is considered an important mechanisms responsible for the downward transport/sedimentation of MPs in the ocean and freshwaters. Previous studies demonstrated MP sinking caused by an increase in the composite density of MPs after biofouling, while MPs with smaller size or shapes with higher surface area to volume ratios (SA:V), such as films, are speculated to sink faster. In this study, we designed an in situ microcosm to simulate the ambient environmental conditions experienced by floating MPs to elucidate the biofouling and sinking of polyethylene (PE), polypropylene (PP), and expanded-polystyrene (EPS) MPs of various sizes and shapes. Our results showed smaller PE and PP MP granules sank faster than large ones. Even EPS granules of 100 μm diameter, having a much lower density (0.02 mg/mm³) than water, started to sink after 2 weeks of biofouling. Moreover, PE film and fiber MPs with higher SA:V did not sink faster than PE MP granules of the same mass, implying that mechanisms other than SA:V, such as fouling contact area and drag coefficient, play a role in the regulation of biofouling and sinking of MPs.

Introduction and Perspectives of DNA Electrophoresis

Gel electrophoresis of DNA is one of the most frequently used techniques in molecular biology. Typically, it is used in the following: the analysis of in vitro reactions and purification of DNA fragments, analysis of PCR reactions, characterization of enzymes involved in DNA reactions, and sequencing. With some ingenuity gel electrophoresis of DNA is also used for the analysis of cellular biochemical reactions. For example, DNA breaks that accumulate in cells are analyzed by the comet assay and pulsed-field gel electrophoresis (PFGE). Furthermore, DNA replication intermediates are analyzed with two-dimensional (2D) gel electrophoresis. Moreover, several new methods for analyzing various chromosomal functions in cells have been developed. In this chapter, a brief introduction to these is given.

Measurement of Rice Grain Dimensions and Chalkiness, and Rice Grain Elongation Using Image Analysis

Measurements of rice grain dimensions, percent grain chalkiness, and grain elongation used to be tedious and slow due to the manual nature of measurements (e.g., use of calipers to measure grains one at a time) and the subjective nature of scoring based on visual inspection (i.e., chalkiness). Recent developments in imaging technologies have enabled more high-throughput means for measuring physical traits (i.e., grain dimensions and chalkiness) in raw grains and grain elongation by comparing ratio between raw versus cooked rice. The digital images of rice grains are captured through computer scanning and analyzed using software that can calculate area and pixel value statistics of user-defined parameters. The improvements in throughput made possible by the use of imaging technologies will allow faster quality grading of rice varieties. Market quality is usually defined based on the rice grain physical traits (grain size and shape), degree of chalkiness, and the ability of rice to elongate on cooking. In this chapter, the routine methods to measure the physical traits of rice and grain elongation using image analysis are described.

Prenatal phthalate exposure and placental size and shape at birth: A birth cohort study

OBJECTIVE

There is concern over the potential placental effects of prenatal phthalate exposure, and the potential adverse effects of prenatal phthalate exposure require further study; however, few data are available in humans. We investigated the associations between phthalate exposure in each trimester and both placental size and shape at birth.

METHODS

We measured the urinary concentrations of phthalate metabolites among 2725 pregnant women in the Ma'anshan Birth Cohort. Before collecting urine samples from each of the three trimesters, the pregnant women were interviewed via questionnaires. Placental information was obtained from hospital records. We estimated the sex-specific associations between urinary phthalate concentrations in each trimester and both placental size and shape at birth using adjusted multiple regression. A linear mixed model was used for the repeated measures analysis with subject-specific random intercepts and slopes for gestational age at sample collection to test the effect of phthalate levels on placental size and shape and to estimate the effect sizes.

RESULTS

Overall, placental breadth increased by 0.148cm (95% CI: 0.078, 0.218) with each 1 ln-concentration increase in MBP in the first trimester. The difference between placental length and breadth (length-breadth) decreased by 0.086cm (95% CI: -0.159, -0.012) and 0.149cm (95% CI: -0.221, -0.076) with each 1 ln-concentration increase in MMP and MBP, respectively, in the first trimester. In the second trimester, placental thickness increased by 0.017cm (95% CI: 0.006, 0.027), 0.020cm (95% CI: 0.004, 0.036), 0.028cm (95% CI: 0.007, 0.048), and 0.035cm (95% CI: 0.018, 0.053) with each 1 ln-concentration increase in MMP, MBP, MEOHP, and MEHHP, respectively. In the third trimester, placental thickness increased by 0.037cm (95% CI: 0.019, 0.056) and 0.019cm (95% CI: 0, 0.037) with each 1 ln-concentration increase in MBP and MEHP, respectively. Multiple linear regression for each offspring sex indicated that prenatal phthalate exposure increased placental thickness in both the first and second trimesters in males, whereas the corresponding relationship was close to null in females. Linear mixed models (LMMs) yielded similar results.

CONCLUSION

Our results suggest the presence of associations between prenatal phthalate exposure and placental size and shape. Exposure to certain phthalates may cause the placenta to become thicker and more circular. Associations appeared stronger for the subsample representing male offspring than those for the subsample representing female offspring. Given the few studies on this topic, additional research is warranted.