خيارات البحث
النتائج 251 - 260 من 4,043
Long-term exposure of polychaetes to caffeine: Biochemical alterations induced in Diopatra neapolitana and Arenicola marina النص الكامل
2016
Pires, Adília | Almeida, Angela Maria da | Calisto, Vânia | Schneider, Rudolf J. | Esteves, Valdemar I. | Wrona, Frederick J. | Soares, Amadeu M.V.M. | Figueira, Etelvina | Freitas, Rosa
In the last decade studies have reported the presence of several pharmaceutical drugs in aquatic environments worldwide and an increasing effort has been done to understand the impacts induced on wildlife. Among the most abundant drugs in the environment is caffeine, which has been reported as an effective chemical anthropogenic marker. However, as for the majority of pharmaceuticals, scarce information is available on the adverse effects of caffeine on marine benthic organisms, namely polychaetes which are the most abundant group of organisms in several aquatic ecossystems. Thus, the present study aimed to evaluate the biochemical alterations induced by environmentally relevant concentrations of caffeine on the polychaete species Diopatra neapolitana and Arenicola marina. The results obtained demonstrated that after 28 days exposure oxidative stress was induced in both species, especially noticed in A. marina, resulting from the incapacity of antioxidant and biotransformation enzymes to prevent cells from lipid peroxidation. The present study further revealed that D. neapolitana used glycogen and proteins as energy to develop defense mechanisms while in A. marina these reserves were maintained independently on the exposure concentration, reinforcing the low capacity of this species to fight against oxidative stress.
اظهر المزيد [+] اقل [-]Gaseous polycyclic aromatic hydrocarbon concentrations are higher in urban forests than adjacent open areas during summer but not in winter – Exploratory study النص الكامل
2016
Viippola, Viljami | Rantalainen, Anna-Lea | Yli-Pelkonen, Vesa | Tervo, Peatta | Setälä, Heikki
While the potential of plants to uptake polycyclic aromatic hydrocarbons (PAHs) is widely acknowledged, empirical evidence of the effects of this process on local atmospheric PAH concentrations and human health is tenuous. We measured gaseous PAH concentrations using passive samplers in urban tree-covered areas and adjacent open, treeless areas in a near-road environment in Finland to gain information on the ability of urban vegetation to improve air quality. The ability of urban, mostly deciduous, vegetation to affect PAHs was season dependent: during summer, concentrations were significantly higher in tree-covered areas, while in the fall, concentrations in open areas exceeded those in tree-covered areas. During winter, concentrations in tree-covered areas were either lower or did not differ from those in open areas. Results of this study imply that the commonly believed notion that trees unequivocally improve air quality does not apply to PAHs studied here.
اظهر المزيد [+] اقل [-]Mutielemental concentration and physiological responses of Lavandula pedunculata growing in soils developed on different mine wastes النص الكامل
2016
Santos, Erika S. | Abreu, Maria Manuela | Saraiva, Jorge A.
This study aimed to: i) evaluate the accumulation and translocation patterns of potentially hazardous elements into the Lavandula pedunculata and their influence in the concentrations of nutrients; and ii) compare some physiological responses associated with oxidative stress (concentration of chlorophylls (Chla, Chlb and total), carotenoids, and total protein) and several components involved in tolerance mechanisms (concentrations of proline and acid-soluble thiols and total/specific activity of catalase (CAT) and superoxide dismutase (SOD)), in plants growing in soils with a multielemental contamination and non-contaminated. Composite samples of soils, developed on mine wastes and/or host rocks, and L. pedunculata (roots and shoots) were collected in São Domingos mine (SE of Portugal) and in a reference area with non-contaminated soils, Corte do Pinto, with the same climatic conditions.São Domingos soils had high total concentrations of several hazardous elements (e.g. As and Pb) but their available fractions were small (mainly <5.8 % of the total). Translocation behaviour of elements was not clear according to the physiological importance of the elements. In general, plant shoots from São Domingos had the highest elements concentrations, but only As, Mn and Zn reached phytotoxic concentrations. Concentration of Chlb in shoots from São Domingos was higher than those from Corte do Pinto. No significant differences were obtained between concentrations of Chla, total protein, proline and acid-soluble thiols in shoots collected in both areas, as well as SOD activity (total and specific) and specific CAT activity. Total CAT activity varied with population being lower in the shoots of the plants from São Domingos, but no correlation was obtained between this enzymatic activity and the concentrations of the studied elements in shoots.Lavandula pedunculata plants are able to survive in soils developed on different mine wastes with multielemental contamination and low fertility showing no symptoms (visible and physiological) of phytotoxicity or deficiency.
اظهر المزيد [+] اقل [-]Global-scale patterns in anthropogenic Pb contamination reconstructed from natural archives النص الكامل
2016
Marx, Samuel K. | Rashid, Shaqer | Stromsoe, Nicola
During the past two centuries metal loads in the Earth's atmosphere and ecosystems have increased significantly over pre-industrial levels. This has been associated with deleterious effects to ecosystem processes and human health. The magnitude of this toxic metal burden, as well as the spatial and temporal patterns of metal enrichment, is recorded in sedimentary archives across the globe. This paper presents a compilation of selected Pb contamination records from lakes (n = 10), peat mires (n = 10) and ice fields (n = 7) from Europe, North and South America, Asia, Australia and the Northern and Southern Hemisphere polar regions. These records quantify changes in Pb enrichment in remote from source environments. The presence of anthropogenic Pb in the environment has a long history, extending as far back as the early to mid-Holocene in North America, Europe and East Asia. However, results show that Pb contamination in the Earth's environment became globally ubiquitous at the beginning of the Second Industrial Revolution (c.1850–1890 CE), after which the magnitude of Pb contamination increased significantly. This date therefore serves as an effective global marker for the onset of the Anthropocene. Current global average Pb enrichment rates are between 6 and 35 times background, however Pb contamination loads are spatially variable. For example, they are >100 times background in Europe and North America and 5–15 times background in Antarctica. Despite a recent decline in Pb loads in some regions, most notably Europe and North America, anthropogenic Pb remains highly enriched and universally present in global ecosystems, while concentrations are increasing in some regions (Australia, Asia and parts of South America and Antarctica). There is, however, a paucity of Pb enrichment records outside of Europe, which limits assessments of global contamination.
اظهر المزيد [+] اقل [-]Abundance of antibiotic resistance genes in five municipal wastewater treatment plants in the Monastir Governorate, Tunisia النص الكامل
2016
Rafraf, Ikbel Denden | Lekunberri, Itziar | Sànchez-Melsió, Alexandre | Aouni, Mahjoub | Borrego, Carles M. | Balcázar, José Luis
Antimicrobial resistance is a growing and significant threat to global public health, requiring better understanding of the sources and mechanisms involved in its emergence and spread. We investigated the abundance of antibiotic resistance genes (ARGs) before and after treatment in five wastewater treatment plants (WWTPs) located in different areas of the Monastir Governorate (Tunisia). Three of these WWTPs (Frina, Sahline and Zaouiet) use a conventional activated sludge process as secondary treatment, whereas the WWTP located in Beni Hassen applies an ultraviolet disinfection step after the activated sludge process and the WWTP located in Moknine treats wastewater using naturally aerated lagoons as a secondary treatment process. The abundance of six ARGs (blaCTX-M, blaTEM, qnrA, qnrS, sul I and ermB) and the class 1 integron-integrase gene (intI1) were determined by quantitative PCR. All ARGs and the intI1 gene were detected in the wastewater samples, except the blaCTX-M gene, which was not detected in both influent and effluent samples from Sahline and Beni Hassen WWTPs, and the qnrS gene, which was not detected neither in the WWTP influent in Moknine nor in the WWTP effluent in Beni Hassen. Although the relative concentration of ARGs was generally found to be similar between samples collected before and after the wastewater treatment, the abundance of blaCTX-M, blaTEM, and qnrS genes was higher in the effluent of the Frina WWTP which, unlike other WWTPs, not only receives domestic or industrial sewage but also untreated hospital waste. To the best of our knowledge, this study quantified for the first time the abundance of ARGs in different Tunisian WWTPs, and the results agree with previous studies suggesting that conventional wastewater treatment does not efficiently reduce ARGs. Therefore, these findings could be useful to improve the design or operation of WWTPs.
اظهر المزيد [+] اقل [-]Temporal changes of radiocesium in irrigated paddy fields and its accumulation in rice plants in Fukushima النص الكامل
2016
Yang, Baolu | Onda, Yūichi | Wakiyama, Yoshifumi | Yoshimura, Kazuya | Sekimoto, Hitoshi | Ha, Yiming
About half of the total paddy field area, which is the dominant agricultural land in Fukushima Prefecture, was contaminated by radiocesium released by the Fukushima Daiichi Nuclear Power Plant accident. In this study, we investigated the temporal changes of radiocesium in soil, irrigation water, and rice plant in two adjacent rice paddies, with and without surface-soil-removal, in Fukushima Prefecture for over three years (2012–2014) after the nuclear accident. Our results showed that radiocesium migrated into 24–28 cm soil layers and that the activity concentration of radiocesium in paddy soils showed a significant reduction in 2014. The newly added radiocesium to paddies through irrigation water contributed only a maximum value of 0.15% and 0.75% of the total amount present in control and decontaminated paddies, respectively, throughout the study period. The radiocesium activity concentration in suspended sediment in irrigation water exponentially decreased, and the effective half-lives (Teff) for ¹³⁷Cs and ¹³⁴Cs were 1.3 and 0.9 years, respectively. Additionally, the average suspended sediment concentration in irrigation water increased between 2012 and 2014, suggesting that enhanced soil erosion had occurred in the surrounding environment. Radiocesium accumulation in rice plant also decreased with time in both paddies. However, the concentration ratio of radiocesium for rice plant in the decontaminated paddy increased compared with control paddy, despite approximately 96% of fallout radiocesium removed in paddy soil. Further analysis is required to clarify the reasons of high concentration ratio of radiocesium for rice plant in the decontaminated paddy.
اظهر المزيد [+] اقل [-]Characterization of phenol and cresol biodegradation by compound-specific stable isotope analysis النص الكامل
2016
Wei, Xi | Gilevska, Tetyana | Wetzig, Felix | Dorer, Conrad | Richnow, Hans-Hermann | Vogt, Carsten
Microbial degradation of phenol and cresols can occur under oxic and anoxic conditions by different degradation pathways. One recent technique to take insight into reaction mechanisms is compound-specific isotope analysis (CSIA). While enzymes and reaction mechanisms of several degradation pathways have been characterized in (bio)chemical studies, associated isotope fractionation patterns have been rarely reported, possibly due to constraints in current analytical methods. In this study, carbon enrichment factors and apparent kinetic isotope effects (AKIEc) of the initial steps of different aerobic and anaerobic phenol and cresols degradation pathways were analyzed by isotope ratio mass spectrometry connected with liquid chromatography (LC-IRMS). Significant isotope fractionation was detected for aerobic ring hydroxylation, anoxic side chain hydroxylation, and anoxic fumarate addition, while anoxic carboxylation reactions produced small and inconsistent fractionation. The results suggest that several microbial degradation pathways of phenol and cresols are detectable in the environment by CSIA.
اظهر المزيد [+] اقل [-]Seasonal variation and partitioning of endocrine disrupting chemicals in waters and sediments of the Pearl River system, South China النص الكامل
2016
Gong, Jian | Duan, Dandan | Yang, Yu | Ran, Yong | Chen, Diyun
Endocrine disrupting chemicals (EDCs) were seasonally investigated in surface water, suspended particulate matter, and sediments of the Pearl River Delta (PRD), South China. EDC concentrations in the surface water were generally higher in the summer than in winter. The surface water in the investigated rivers was heavily contaminated by the phenolic xenoestrogens. Moreover, the in-situ log Ksoc and log Kpoc values and their regression with log Kow in the field experiments suggest that binding mechanisms other than hydrophobic interaction are present for the sedimentary organic carbon and particulate organic carbon (SOC/POC). The logKsoc–logKow and logKpoc–logKow regression analyses imply that higher complexity of nonhydrophobic interactions with EDCs is present on the SOC samples comparing with the POC samples, which is related to their different sources.
اظهر المزيد [+] اقل [-]Improving the ecological relevance of toxicity tests on scleractinian corals: Influence of season, life stage, and seawater temperature النص الكامل
2016
Hédouin, Laetitia S. | Wolf, Ruth E. | Phillips, Jeff | Gates, Ruth D.
Metal pollutants in marine systems are broadly acknowledged as deleterious: however, very little data exist for tropical scleractinian corals. We address this gap by investigating how life-history stage, season and thermal stress influence the toxicity of copper (Cu) and lead (Pb) in the coral Pocillopora damicornis. Our results show that under ambient temperature, adults and larvae appear to tolerate exposure to unusually high levels of copper (96 h-LC50 ranging from 167 to 251 μg Cu L−1) and lead (from 477 to 742 μg Pb L−1). Our work also highlights that warmer conditions (seasonal and experimentally manipulated) reduce the tolerance of adults and larvae to Cu toxicity. Despite a similar trend observed for the response of larvae to Pb toxicity to experimentally induced increase in temperature, surprisingly adults were more resistant in warmer condition to Pb toxicity. In the summer adults were less resistant to Cu toxicity (96 h-LC50 = 175 μg L−1) than in the winter (251 μg L−1). An opposite trend was observed for the Pb toxicity on adults between summer and winter (96 h-LC50 of 742 vs 471 μg L−1, respectively). Larvae displayed a slightly higher sensitivity to Cu and Pb than adults. An experimentally induced 3 °C increase in temperature above ambient decreased larval resistance to Cu and Pb toxicity by 23–30% (96 h-LC50 of 167 vs 129 μg Cu L−1 and 681 vs 462 μg Pb L−1).Our data support the paradigm that upward excursions in temperature influence physiological processes in corals that play key roles in regulating metal toxicity. These influences are more pronounced in larva versus adult corals. These findings are important when contextualized climate change-driven warming in the oceans and highlight that predictions of ecological outcomes to metal pollutants will be improved by considering environmental context and the life stages of organism under study.
اظهر المزيد [+] اقل [-]Effects of myclobutanil on soil microbial biomass, respiration, and soil nitrogen transformations النص الكامل
2016
Ju, Chao | Xu, Jun | Wu, Xiaohu | Dong, Fengshou | Liu, Xingang | Zheng, Yongquan
A 3-month-long experiment was conducted to ascertain the effects of different concentrations of myclobutanil (0.4 mg kg⁻¹ soil [T1]; 1.2 mg kg⁻¹ soil [T3]; and 4 mg kg⁻¹ soil [T10]) on soil microbial biomass, respiration, and soil nitrogen transformations using two typical agricultural soils (Henan fluvo-aquic soil and Shanxi cinnamon soil). Soil was sampled after 7, 15, 30, 60, and 90 days of incubation to determine myclobutanil concentration and microbial parameters: soil basal respiration (RB), microbial biomass carbon (MBC) and nitrogen (MBN), NO−3–N and NH+4–N concentrations, and gene abundance of total bacteria, N2-fixing bacteria, fungi, ammonia-oxidizing archaea (AOA), and ammonia-oxidizing bacteria (AOB). The half-lives of the different doses of myclobutanil varied from 20.3 to 69.3 d in the Henan soil and from 99 to 138.6 d in the Shanxi soil. In the Henan soil, the three treatments caused different degrees of short-term inhibition of RB and MBC, NH+4–N, and gene abundance of total bacteria, fungi, N2-fixing bacteria, AOA, and AOB, with the exception of a brief increase in NO−3–N content during the T10 treatment. The MBN (immobilized nitrogen) was not affected. In the Shanxi soil, MBC, the populations of total bacteria, fungi, and N2-fixing bacteria, and NH+4–N concentration were not significantly affected by myclobutanil. The RB and MBN were decreased transitorily in the T10 treatment. The NO−3–N concentrations and the abundance of both AOA and AOB were erratically stimulated by myclobutanil. Regardless of whether stimulation or suppression occurred, the effects of myclobutanil on the two soil types were short term. In summary, myclobutanil had no long-term negative effects on the soil microbial biomass, respiration, and soil nitrogen transformations in the two types of soil, even at 10-fold the recommended dosage.
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