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Resultados 2351-2360 de 4,033
Toxicokinetics of chiral polychlorinated biphenyls across different species—a review
2016
Kania-Korwel, Izabela | Lehmler, Hans-Joachim
Nineteen polychlorinated biphenyls (chiral or C-PCBs) exist as two stable rotational isomers (atropisomers) that are non-superimposable mirror images of each other. C-PCBs are released into the environment as racemic (i.e., equal) mixtures of both atropisomers and undergo atropisomeric enrichment due to biological, but not abiotic, processes. In particular, toxicokinetic studies provide important initial insights into atropselective processes involved in the disposition (i.e., absorption, distribution, biotransformation, and excretion) of C-PCBs. The toxicokinetic of C-PCBs is highly congener and species dependent. In particular, at lower trophic levels, abiotic processes play a predominant role in C-PCB toxicokinetics. Biotransformation plays an important role in the elimination of C-PCBs in mammals. The elimination of C-PCB follows the approximate order mammals > birds > amphibians > fish, mostly due to a corresponding decrease in metabolic capacity. A few studies have shown differences in the toxicokinetics of C-PCB atropisomers; however, more work is needed to understand the toxicokinetics of C-PCBs and the underlying biological processes. Such studies will not only contribute to our understanding of the fate of C-PCBs in aquatic and terrestrial food webs but also facilitate our understanding of human exposures to C-PCBs.
Mostrar más [+] Menos [-]Effects of electromagnetic fields on serum lipids in workers of a power plant
2016
Wang, Zhaopin | Wang, Lijuan | Zheng, Shuangshuang | Ding, Zheyuan | Liu, Hui | Jin, Wen | Pan, Yifeng | Chen, Zexin | Fei, Ying | Chen, Guangdi | Xu, Zhengping | Yu, Yunxian
This study aimed to evaluate the effects of electromagnetic fields (EMF) exposure on levels of serum lipids in workers of an electric power plant. A cross-sectional study was carried out in an electric power plant in Zhejiang province, China, from August to September 2011. All participants were divided into two groups with high occupational EMF exposure and low occupational EMF exposure. The occupational EMF exposure included radiofrequency EMF and extremely low-frequency EMF. Occupational EMF exposure was associated with an increased level of low-density lipoprotein cholesterol (LDL-c; β = 0.17 mmol/L, P = 0.022). High EMF exposure group with longer employment duration, longer daily EMF exposure duration, and more mobile phone or electric fee per month had significantly higher levels of total cholesterol, LDL-c, or triglyceride than the corresponding reference group. However, significantly decreased level of high-density lipoprotein cholesterol was only observed in high EMF exposure group with more mobile phone fee per month. Similar results were also found in 544 participants with available data of serum lipids in 2010. The findings showed that chronic EMF exposure was associated with the change of serum lipid levels. EMF exposure might modulate the process of lipid metabolism.
Mostrar más [+] Menos [-]Microbial community characteristics during simultaneous nitrification-denitrification process: effect of COD/TP ratio
2016
Zhang, Jian | Jia, Wenlin | Wang, Rong | Ngo, Huu Hao | Guo, Wenshan | Xie, Huijun | Liang, Shuang
To evaluate the impact of chemical oxygen demand (COD)/total phosphorus (TP) ratio on microbial community characteristics during low-oxygen simultaneous nitrification and denitrification process, three anaerobic-aeration (low-oxygen) sequencing batch reactors, namely R1, R2, and R3, were performed under three different COD/TP ratios of 91.6, 40.8, and 27.6. The community structures of each reactor were analyzed via molecular biological technique. The results showed that the composition of ammonia-oxidizing bacteria (AOB) was affected, indicated by Shannon indexes of the samples from R1, R2, and R3. Nitrosomonas was identified to be the dominant AOB in all SBRs. Moreover, the copy numbers of nitrifiers were more than those of denitrifiers, and the phosphorus-accumulating organisms to glycogen-accumulating organisms ratio increased with the decrease of COD/TP ratio.
Mostrar más [+] Menos [-]Assessment of metal retention in newly constructed highway embankments
2016
Werkenthin, Moritz | Kluge, Björn | Wessolek, Gerd
Newly constructed embankments should provide both a specific bearing capacity to enable trafficability in emergency cases and a sufficient pollutant retention capacity to protect the groundwater. A number of lysimeters were installed along the A115 highway to determine total and dissolved metal concentrations in road runoff and in the soil solution of newly constructed embankments. Dissolved concentrations in soil solution of the embankments did not exceed the trigger values of the German legislation. Depending on the metal, total concentrations in soil solution were more than twice as high as dissolved concentrations. The high infiltration rates lead to increased groundwater recharge beneath the embankments (up to 4100 mm a⁻¹). Although metal concentrations were not problematic from the legislators’ point of view, the elevated infiltration rates beside the road facilitated the transfer of high metal loads into deeper soil layers and potentially into the groundwater as well.
Mostrar más [+] Menos [-]Water mutagenic potential assessment on a semiarid aquatic ecosystem under influence of heavy metals and natural radioactivity using micronuclei test
2016
Chaves, Luiz Cláudio Cardozo | Navoni, Julio Alejandro | de Morais Ferreira, Douglisnilson | Batistuzzo de Medeiros, Silvia | Ferreira da Costa, Thomas | Petta, Reinaldo Antônio | Souza do Amaral, Viviane
The contamination of water bodies by heavy metals and ionizing radiation is a critical environmental issue, which can affect water quality and, thus, human health. This study aimed to evaluate the water quality of the Boqueirão de Parelhas Dam in the Brazilian semiarid region. A 1-year study (2013–2014) was performed through the assessment of physicochemical parameters, heavy metal content, and radioactivity along with the mutagenicity potential of water using micronuclei test in Orechromis niloticus (in vivo) and the cytokinesis-block micronucleus (CBMN) assay in human lymphocytes (in vitro). A deterioration of water organoleptics characteristics by the presence of high levels of sulfate and total solids was observed. High concentrations of aluminum, nickel, silver, and lead along with the alpha particle content were higher than the limits suggested by the World Health Organization and Brazilian legislation for drinking water. An increase in the frequency of micronuclei and nuclear abnormalities was observed in both experimental models. The results obtained confirmed the mutagenic potential present in water samples. This study highlights that geogenic agents affect water quality becoming a human health concern to be taken into account due to the relevance that this water reservoir has in the region.
Mostrar más [+] Menos [-]Direct mineral carbonation of steelmaking slag for CO2 sequestration at room temperature
2016
Rushendra Revathy, T. D. | Palanivelu, K. | Ramachandran, A.
Rapid increase of CO₂ concentration in the atmosphere has forced the international community towards adopting actions to restrain from the impacts of climate change. Moreover, in India, the dependence on fossil fuels is projected to increase in the future, implying the necessity of capturing CO₂ in a safe manner. Alkaline solid wastes can be utilized for CO₂ sequestration by which its disposal issues in the country could also be met. The present work focuses to study direct mineral carbonation of steelmaking slag (SS) at room temperature and low-pressure conditions (<10 bar). Direct mineral carbonation of SS was carried out in a batch reactor with pure CO₂ gas. The process parameters that may influence the carbonation of SS, namely, CO₂ gas pressure, liquid to solid ratio (L/S) and reaction time were also studied. The results showed that maximum sequestration of SS was attained in the aqueous route with a capacity of 82 g of CO₂/kg (6 bar, L/S ratio of 10 and 3 h). In the gas-solid route, maximum sequestration capacity of about 11.1 g of CO₂/kg of SS (3 bar and 3 h) was achieved indicating that aqueous route is the better one under the conditions studied. These findings demonstrate that SS is a promising resource and this approach could be further developed and used for CO₂ sequestration in the country. The carbonation process was evidenced using FT-IR, XRD, SEM and TG analysis.
Mostrar más [+] Menos [-]Airborne biological hazards and urban transport infrastructure: current challenges and future directions
2016
Nasir, Zaheer Ahmad | Campos, Luiza Cintra | Christie, Nicola | Colbeck, I. (Ian)
Exposure to airborne biological hazards in an ever expanding urban transport infrastructure and highly diverse mobile population is of growing concern, in terms of both public health and biosecurity. The existing policies and practices on design, construction and operation of these infrastructures may have severe implications for airborne disease transmission, particularly, in the event of a pandemic or intentional release of biological of agents. This paper reviews existing knowledge on airborne disease transmission in different modes of transport, highlights the factors enhancing the vulnerability of transport infrastructures to airborne disease transmission, discusses the potential protection measures and identifies the research gaps in order to build a bioresilient transport infrastructure. The unification of security and public health research, inclusion of public health security concepts at the design and planning phase, and a holistic system approach involving all the stakeholders over the life cycle of transport infrastructure hold the key to mitigate the challenges posed by biological hazards in the twenty-first century transport infrastructure.
Mostrar más [+] Menos [-]Repeated application of composted tannery sludge affects differently soil microbial biomass, enzymes activity, and ammonia-oxidizing organisms
2016
Araújo, Ademir Sérgio Ferreira | Lima, Luciano Moura | Santos, Vilma Maria | Schmidt, Radomir
Repeated application of composted tannery sludge (CTS) changes the soil chemical properties and, consequently, can affect the soil microbial properties. The aim of this study was to evaluate the responses of soil microbial biomass and ammonia-oxidizing organisms to repeated application of CTS. CTS was applied repeatedly during 6 years, and, at the sixth year, the soil microbial biomass, enzymes activity, and ammonia-oxidizing organisms were determined in the soil. The treatments consisted of 0 (without CTS application), 2.5, 5, 10, and 20 t ha⁻¹ of CTS (dry basis). Soil pH, EC, SOC, total N, and Cr concentration increased with the increase in CTS rate. Soil microbial biomass did not change significantly with the amendment of 2.5 Mg ha⁻¹, while it decreased at the higher rates. Total and specific enzymes activity responded differently after CTS application. The abundance of bacteria did not change with the 2.5-Mg ha⁻¹ CTS treatment and decreased after this rate, while the abundance of archaea increased significantly with the 2.5-Mg ha⁻¹ CTS treatment. Repeated application of different CTS rates for 6 years had different effects on the soil microbial biomass and ammonia-oxidizing organisms as a response to changes in soil chemical properties.
Mostrar más [+] Menos [-]The effect of Eulaliopsis binata on the physi-chemical properties, microbial biomass, and enzymatic activities in Cd-Pb polluted soil
2016
Yu, Hui | Xiang, Yanci | Zou, Dongsheng
Pot culture experiment using mining wasteland soil was carried out to study the effect of Eulaliopsis binata on the heavy-metal polluted soil with the growth of 90, 180, 270, and 360 days. Soil nutritional components, heavy metal, microbial biomass, and enzymatic activities were analyzed in this study, and the control group had no plants. The results showed that heavy metal contents decreased with E. binata growth, extractable Cd and Pb decreased 28 and 15 % after 1 year, but the difference was not significant compared with the control. While soil nutritional components, microbial biomass and enzymatic activities increased significantly as compared with the control. Comparing with pre-experiment, soil organic matter, N, P, K, microbial biomass C, N, P, invertase, urease, acid phosphatase, and catalase increased 0.9, 1.1, 3.0, 1.1, 0.4, 0.3, and 0.5 times, respectively. The indexes of soil nutritional components, microbial biomass, and enzymatic activities are positively correlated to each other, while they are negatively correlated to heavy metal content respectively. E. binata has positive influence on Cd-Pb pollution soil and broad application prospects in remediating heavy-metal polluted soil.
Mostrar más [+] Menos [-]Sympodial bamboo species differ in carbon bio-sequestration and stocks within phytoliths of leaf litters and living leaves
2016
Xiang, Tingting | Ying, Yuqi | Teng, Jiangnan | Huang, Zhangting | Wu, Jiasen | Meng, Cifu | Jiang, Peikun | Tang, Caixian | Li, Jianmin | Zheng, Rong
Phytolith-occluded carbon (PhytOC) with high resistance against decomposition is an important carbon (C) sink in many ecosystems. This study compared concentrations of phytolith in plants and the PhytOC production of seven sympodial bamboo species in southern China, aiming to provide the information for the managed bamboo plantation and selection of bamboo species to maximize phytolith C sequestration. Leaf litters and living leaves of seven sympodial bamboo species were collected from the field sites. Concentrations of phytoliths, silicon (Si), and PhytOC in leaf litters and living leaves were measured. Carbon sequestration as PhytOC was estimated. There was a considerable variation in the PhytOC concentrations in the leaf litters and living leaves among the seven bamboo species. The mean concentrations of PhytOC ranged from 3.4 to 6.9 g kg⁻¹ in leaf litters and from 1.6 to 5.9 g kg⁻¹ in living leaves, with the PhytOC production rates ranging from 5.7 to 52.3 kg e-CO₂ ha⁻¹ year⁻¹ as leaf litters. Dendrocalamopsis oldhami (Munro) Keng f. had the highest PhytOC production rate. Based on a bio-sequestration rate of 52.3 kg e-CO₂ ha⁻¹ year⁻¹, we estimated that the current 8 × 10⁵ ha of sympodial bamboo stands in China could potentially acquire 4.2 × 10⁴ t e-CO₂ yearly via phytolith carbon. Furthermore, the seven sympodial bamboo species stored 5.38 × 10⁵ t e-CO₂ as PhytOC in living leaves and leaf litters in China. It is concluded that sympodial bamboos make a significant contribution to C sequestration and that to maximize the PhytOC accumulation, the bamboo species with the highest PhytOC production rate should be selected for plantation.
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