Zobrazení zdroje stránky Sextondowns0847

Since the Chernobyl and Fukushima nuclear power plant accidents, extensive research has focused on the distribution and cycle of radiocesium in forest systems. Nevertheless, direct chemical speciation analyses of Cs by spectroscopic methods are limited by the low abundances of stable Cs as well as radiocesium in trees. In this study, we investigated coordination structures of Cs in 133Cs-doped bark, sapwood, heartwood, needle, and branch samples of trees collected in Fukushima by extended X-ray absorption fine structure (EXAFS) spectroscopy. We examined four representative tree species in Fukushima, Cryptomeria japonica, Pinus densiflora, Quercus serrata, and Eleutherococcus sciadophylloides. EXAFS spectra suggested that Cs was adsorbed as an outer-sphere complex on all parts of the four species, with electrostatic binding to negatively charged functional groups in components of tree tissues. These results were supported by extraction experiments where more than 98.5% of the sorbed Cs was desorbed from all parts of each tree species using 1 M CH3COONH4. Sorption experiments of Cs on cellulose, an important component of plant cell walls, were carried out in ultrapure water, NaCl, and KCl solutions. The Kd values for cellulose and solutions were not high enough to fix Cs, considering the composition of sap in trees. Overall, the results of this study are consistent with previous field observations indicating that radiocesium is translocated in mobile form to metabolically active tree parts.Fathead minnows (Pimephales promelas) were continuously exposed to the herbicide atrazine (0.15, 0.25, 0.46, 0.99, and 2.0 mg a.i./L, plus dilution water and solvent controls) for a complete life cycle (274 days). Concentrations of atrazine up to 2.0 mg a.i./L did not significantly reduce hatching success, larval survival at 30 or 60 days post-hatch, or reproduction (eggs/spawn, total eggs, spawns/female, or eggs/female) in the F0 generation. However, at 60 days of exposure, total length and total survival to study completion were significantly reduced in ≥0.46 mg a.i./L and ≥ 0.99 mg a.i./L treatments, respectively. In the F1 generation, hatchability of embryos at ≥0.25 mg a.i./L (range 74-82%) was significantly less than that of pooled control organisms (86%). Following 30 days' post-hatch exposure, F1 survival was not significantly different from pooled control for any treatment. Finally, tissues representing major life stages had bioconcentration factors ranging from 3.7× (F1 embryos, less then 24 h) to 8.5× (F0 adults), indicating little to no evidence of bioconcentration. We developed a series of questions to assess the consistency of observed responses in order to place the data in context with the wider available and relevant literature (e.g., Observed between studies? Observed between species? Observed at lower levels of biological organization?). The analysis for consistency supports the conclusion that atrazine does not pose a significant chronic risk to freshwater fish in terms of growth, reproduction, or survivorship at concentrations of up to at least 100 μg/L.Plastic based products are ubiquitous due to their tremendous utility in our daily lives. However, the limited biodegradable nature of plastics has recently raised pollution concerns globally, especially micro- and nanoplastics. These anthropogenic pollutants are either manufactured specifically in the small size range for various commercial applications or formed due to fragmentation of macro plastics in the environment. Micro- and nanoplastics are currently widespread in the oceans, freshwater bodies, land and even present in our food. The biological effects of micro- and nanoplastics on aquatic organisms are well documented but their impacts on mammalian system have not been rigorously investigated. This review discusses the potential routes of exposure to micro- and nanoplastics, biological effects of these particles in mammalian cells, factors influencing toxicity, and the probable mechanisms of cytotoxicity. In general, small size, positive charge, high dose, and presence of toxic additives or pollutants in the micro/nanoplastics appear to induce cellular toxicity through oxidative stress, membrane damage, immune response and genotoxicity. Understanding the cellular fate and toxicity of these materials may help extrapolate risks to mammals.Dairy milk and infant formula play important roles in the diet of adolescents, adults and infants, respectively, in the South African population. However, data on the occurrence of legacy and emerging contaminants such as PFAS in these important food sources is lacking. In this study, the concentration of fifteen PFAS were measured in 23 pooled retail dairy milk and 7 pooled infant formulas by means of an ultrahigh performance liquid chromatography tandem mass spectrometric method. [https://www.selleckchem.com/products/jhu-083.html JHU-083] The concentrations of Σ15PFAS ranged from 0.08-15.51 ng mL-1 and 0.42-5.74 ng mL-1 in dairy milk and infant formulas, respectively. PFBA, PFPeA, PFuDA, PFTrDA and PFDoA were the most prevalent PFAS in both matrices with detection frequency &gt; 96%. Highest PFAS concentrations of 2.02 ng ml-1 and 2.76 ng ml-1 were recorded for PFDoA in infant formulas and dairy milk, respectively. The concentrations of legacy PFAS -PFOA and PFOS, shows resemblance with global data, however, elevated concentrations of long chain C9 - C14 PFAS were observed in this study. Though, higher concentrations of PFAS were measured in full cream dairy milk, no statistical significant difference (P = 0.546) was observed for the various classes of dairy milk. The EDI of Σ15PFAS through infant formulas were 184.92, 329.47 and 166 ngkg-1BWday-1 for partially breastfed, exclusively formula fed and older infants, respectively. Similarly, the EDI of PFAS through dairy milk for toddlers, adolescents, female and male adults for the rural population were 14.17, 1.09, 2.59 and 3.16 ngkg-1BWday-1 respectively while they were 20.41, 3.84, 4.13 and 4.26 ngkg-1BWday-1 respectively in the urban population. Although, the EDI of PFAS through the consumption of infant formulas and dairy milk are lower than the daily tolerable limits, the relative importance of long-term exposure and the cumulative effects of multiple exposure pathways cannot be overemphasized.