A critical analysis of sources, pollution, and remediation of selenium, an emerging contaminant.

Selenium (Se) is an essential metalloid and is categorized as emerging anthropogenic contaminant released to the environment. The rise of Se release into the environment has raised concern about its bioaccumulation, toxicity, and potential to cause serious damages to aquatic and terrestrial ecosystem. Therefore, it is extremely important to monitor Se level in environment on a regular basis. Understanding Se release, anthropogenic sources, and environmental behavior is critical for developing an effective Se containment strategy. The ongoing efforts of Se remediation have mostly emphasized monitoring and remediation as an independent topics of research. However, our paper has integrated both by explaining the attributes of monitoring on effective scale followed by a candid review of widespread technological options available with specific focus on Se removal from environmental media. Another novel approach demonstrated in the article is the presentation of an overwhelming evidence of limitations that various researchers are confronted with to overcome achieving effective remediation. Furthermore, we followed a holistic approach to discuss ways to remediate Se for cleaner environment especially related to introducing weak magnetic field for ZVI reactivity enhancement. We linked this phenomenal process to electrokinetics and presented convincing facts in support of Se remediation, which has led to emerge 'membrane technology', as another viable option for remediation. Hence, an interesting, innovative and future oriented review is presented, which will undoubtedly seek attention from global researchers.

Biochar-induced immobilization and transformation of silver-nanoparticles affect growth, intracellular-radicles generation and nutrients assimilation by reducing oxidative stress in maize.

Silver nanoparticles (AgNPs) are used in a wide range of consumer products inevitably releases in massive quantities in the natural environment, posing a potential thread to ecosystem-safety and plant health. Here, the impact of AgNPs (100-1000 mg L-1) without and with biochar (@2 % w/v) amendment on maize plants was assessed in hydroponics exposure medium. AgNPs exposure to plants induced dose-dependent phytotoxicity by suppressing plant growth, disturbing photosynthesis and gas exchange traits and alteration in macro- and micronutrients assimilation. At the same time, AgNPs with addition of biochar alleviated the phyto-toxic effects of AgNPs through approximately 4-8 times reduction in uptake and tissue accumulation of Ag. Moreover, activities of antioxidant enzymes in AgNPs + biochar treated plants indicated the lower oxidative stress. Electron paramagnetic resonance (EPR) spectroscopy confirmed that superoxide (O2-) radical was the dominant reactive oxygen species. Fourier-transform infrared spectroscopic (FTIR) and X-ray photoelectron spectroscopic (XPS) results revealed that biochar surface carboxyl and sulfur functional groups were involved in complexation process with NPs, which inhibited the oxidative dissolution and release of Ag+ ions besides of biochar space shield effect. Thus, the interaction of biochar with AgNPs immobilizes these NPs and can effectively reduce their bioavailability in the environmental matrix.

A comprehensive review on environmental transformation of selenium: recent advances and research perspectives.

Selenium (Se) is an important micronutrient and essential trace element for both humans and animals, which exist in the environment ubiquitously. Selenium deficiency is an important issue worldwide, with various reported cases of its deficiency. Low selenium contents in some specific terrestrial environments have resulted in its deficiency in humans. However, high levels of selenium in the geochemical environment may have harmful influences and can cause a severe toxicity to living things. Due to its extremely narrow deficiency and toxicity limits, selenium is becoming a serious matter of discussion for the scientists who deals with selenium-related environmental and health issues. Based on available relevant literature, this review provides a comprehensive data about Se sources, levels, production and factors affecting selenium bioavailability/speciation in soil, characteristics of Se, biogeochemical cycling, deficiency and toxicity, and its environmental transformation to know the Se distribution in the environment. Further research should focus on thoroughly understanding the concentration, speciation, Se cycling in the environment and food chain to effectively utilize Se resources, remediate Se deficiency/toxicity, and evaluate the Se states and eco-effects on human health.

Developmental selenium exposure and health risk in daily foodstuffs: A systematic review and meta-analysis.

Selenium (Se) is a trace mineral and an essential nutrient of vital importance to human health in trace amounts. It acts as an antioxidant in both humans and animals, immunomodulator and also involved in the control of specific endocrine pathways. The aim of this work is to provide a brief knowledge on selenium content in daily used various foodstuffs, nutritional requirement and its various health consequences. In general, fruits and vegetables contain low content of selenium, with some exceptions. Selenium level in meat, eggs, poultry and seafood is usually high. For most countries, cereals, legumes, and derivatives are the major donors to the dietary selenium intake. Low level of selenium has been related with higher mortality risk, dysfunction of an immune system, and mental failure. Selenium supplementation or higher selenium content has antiviral outcomes and is necessary for effective reproduction of male and female, also decreases the threat of chronic disease (autoimmune thyroid). Generally, some advantages of higher content of selenium have been shown in various potential studies regarding lung, colorectal, prostate and bladder cancers risk, nevertheless results depicted from different trials have been diverse, which perhaps indicates the evidence that supplementation will merely grant advantage if the intakes of a nutrient is deficient. In conclusion, the over-all people should be advised against the usage of Se supplements for prevention of cardiovascular, hepatopathies, or cancer diseases, as advantages of Se supplements are still ambiguous, and their haphazard usage could result in an increased Se toxicity risk. The associations among Se intake/status and health, or disease risk, are complicated and need exposition to notify medical practice, to improve dietary recommendations, and to develop adequate communal health guidelines.

Combustion characteristics and retention-emission of selenium during co-firing of torrefied biomass and its blends with high ash coal.

The combustion characteristics, kinetic analysis and selenium retention-emission behavior during co-combustion of high ash coal (HAC) with pine wood (PW) biomass and torrefied pine wood (TPW) were investigated through a combination of thermogravimetric analysis (TGA) and laboratory-based circulating fluidized bed combustion experiment. Improved ignition behavior and thermal reactivity of HAC were observed through the addition of a suitable proportion of biomass and torrefied. During combustion of blends, higher values of relative enrichment factors in fly ash revealed the maximum content of condensing volatile selenium on fly ash particles, and depleted level in bottom ash. Selenium emission in blends decreased by the increasing ratio of both PW and TPW. Higher reductions in the total Se volatilization were found for HAC/TPW than individual HAC sample, recommending that TPW have the best potential of selenium retention. The interaction amongst selenium and fly ash particles may cause the retention of selenium.

Bisphenol A exposure and healing effects of Adiantum capillus-veneris L. plant extract (APE) in bisphenol A-induced reproductive toxicity in albino rats.

The current study presents the bisphenol A exposure and the ameliorative effects of Adiantum capillus-veneris on testicular toxicity induced by bisphenol A. Adult male albino rats were divided into five groups of five animals each: A (control), B (vehicle control), C (toxic), D (protective), and E (ameliorative) were served distilled water, olive oil, bisphenol A (BPA) at 100 mg/kg body weight, A. capillus-veneris plant extract at 25 mg/kg body weight, and BPA + A. capillus-veneris, respectively. All of the doses were administered orally for 15 days, and the rats were then sacrificed. Blood samples for the testosterone assay and both testes were collected for histological examination. The body weight, paired testes weight, relative tissue weight index, Johnsen scoring of tubules, and level of serum testosterone decreased in BPA-treated rats. Similarly, histological examination of the testes in BPA-treated animals revealed a lower number of Leydig cells, an irregular basement membrane, sloughing of germinal layers, vacuolization, a lower number of spermatocytes, and debris in the lumen. However, co-administration of A. capillus-veneris with BPA increased the total antioxidative capacity (330.82 ± 22.46 µmol/mg protein) of the testes and restored the serum testosterone level (1.70 ng/ml); histological features showed restoration in the stages of spermatogenesis. Conclusively, A. capillus-veneris plant extract overcomes the estrogenic effects of BPA on the reproductive system of rats and protects rats' testes against BPA-induced injury/damage via an antioxidative mechanism that appears to be conciliated.