خيارات البحث
النتائج 1381 - 1390 من 3,240
Cadmium transfer and detoxification mechanisms in a soil–mulberry–silkworm system: phytoremediation potential النص الكامل
2015
Zhou, Lingyun | Zhao, Ye | Wang, Shuifeng
Phytoremediation has been proven to be an environmentally sound alternative for the recovery of contaminated soils, and the economic profit that comes along with the process might stimulate its field use. This study investigated cadmium (Cd) transfer and detoxification mechanisms in a soil–mulberry–silkworm system to estimate the suitability of the mulberry and silkworm as an alternative method for the remediation of Cd-polluted soil; it also explored the underlying mechanisms regulating the trophic transfer of Cd. The results show that both the mulberry and silkworm have high Cd tolerance. The transfer factor suggests that the mulberry has high potential for Cd extraction from polluted soil. The subcellular distribution and chemical forms of Cd in mulberry leaves show that cell wall deposition and vacuolar compartmentalization play important role in Cd tolerance. In the presence of increasing Cd concentrations in silkworm food, detoxification mechanisms (excretion and homeostasis) were activated so that excess Cd was excreted in fecal balls, and metallothionein levels in the mid-gut, the posterior of the silk gland, and the fat body of silkworms were enhanced. And, the Cd concentrations in silk are at a low level, ranging from 0.02 to 0.21 mg kg⁻¹. Therefore, these mechanisms of detoxification can regulate Cd trophic transfer, and mulberry planting and silkworm breeding has high phytoremediation potential for Cd-contaminated soil.
اظهر المزيد [+] اقل [-]Polycyclic Aromatic Hydrocarbons (PAHs) and Heavy Metal Occurrence in Bed Sediments of a Temporary River النص الكامل
2015
Tzoraki, O. | Karaouzas, I. | Patrolecco, L. | Skoulikidis, N. | Nikolaidis, N. P.
The directive 2008/105/EC suggests the use of sediment or biota matrix for long-term monitoring of specific priority pollutants that tend to accumulate. But, the intermittent nature of flow in the majority of the Mediterranean rivers results in large variability of biological communities and especially fish, making advantageous the examination of pollution trend in sediment matrix and not in living organisms (biota). In this study, sediment environmental quality standards (EQSs) and sediment quality indicators (SQIs) were used to assess pollution by heavy metals (cadmium, nickel, lead, mercury, arsenic, chromium, copper, and zinc) and polycyclic aromatic hydrocarbons (PAHs) in Evrotas River, South Greece, monitored seasonally for 2 years (2009–2010) in five sampling sites. The results showed that, based on SQIs (geoaccumulation index (Igeo), enrichment factor (EF), and modified degree of contamination (mCd)), sediments of the Evrotas River can be classified as “low polluted,” with some exceptions of “extreme pollution.” EQS assessment revealed heavy metal pollution ranging from “low” to “medium high.” Furthermore, based on the Hakanson’s ecological risk index (RI) method, heavy metal potential risk was classified from “low” to “extreme.” Cadmium showed the highest RI values, while mercury reached “moderate” pollution level. The average ΣPAH concentration (24.4 ng g⁻¹) was lower than both the reported EQSs and the values found in literature for unpolluted or moderately polluted river sediments. Increased heavy metal and PAH concentrations were found in sites where mixing of freshwater with reclaimed water occurred. EQSs are suggested to be supplemented with the RI or EF index that consider the natural background to assist a first ecorisk assessment and should be foreseen by 2008/105/EC directive. Sediments can be considered as a valuable matrix in assessing the spatial and temporal trends of several contaminants and should be included in the monitoring program of temporary river management plans. Special attention should be given when defining reference sites and the sampling period. Decreasing flow period at the beginning of the spring prevailed in order to diminish any disturbance by flash flood events.
اظهر المزيد [+] اقل [-]Can Simple Soil Parameters Explain Field-Scale Variations in Glyphosate-, Bromoxyniloctanoate-, Diflufenican-, and Bentazone Mineralization? النص الكامل
2015
Norgaard, Trine | de Jonge, Lis W. | Moldrup, Per | Olsen, Preben | Johnsen, Anders R.
The large spatial heterogeneity in soil physico-chemical and microbial parameters challenges our ability to predict and model pesticide leaching from agricultural land. Microbial mineralization of pesticides is an important process with respect to pesticide leaching since mineralization is the major process for the complete degradation of pesticides without generation of metabolites. The aim of our study was to determine field-scale variation in the potential for mineralization of the herbicides glyphosate, bromoxyniloctanoate, diflufenican, and bentazone and to investigate whether this variation can be predicted by variations in basic soil parameters. Sixty-five soil samples were sampled from an agricultural, loamy field in Silstrup, Denmark, from a 60 × 165 m rectangular grid. The mineralization potential of the four pesticides was determined using a 96-well microplate ¹⁴C-radiorespirometric method. Initial mineralization rates were determined using first-order kinetics for glyphosate and bromoxyniloctanoate and zero-order kinetics for diflufenican and bentazone. The mineralization rates of the four pesticides varied between the different pesticides and the different soil samples, but we could not establish correlations between the pesticide mineralization rates and the measured soil parameters. Only the glyphosate mineralization rates showed slightly increasing mineralization potentials towards the northern area of the field, with increasing clay and decreasing OC contents. The mineralization potentials for glyphosate and bentazone were compared with 9-years leaching data from two horizontal wells 3.5 m below the field. The field-scale leaching patterns, however, could not be explained by the pesticide mineralization data. Instead, field-scale pesticide leaching may have been governed by soil structure and preferential flow events.
اظهر المزيد [+] اقل [-]The Importance of the Mining Subsidence Reservoirs Located Along the Trans-Regional Highway in the Conservation of the Biodiversity of Freshwater Molluscs in Industrial Areas (Upper Silesia, Poland) النص الكامل
2015
Lewin, Iga | Spyra, Aneta | Krodkiewska, Mariola | Strzelec, Małgorzata
The objectives of the survey were to analyse the structure of the mollusc communities in the mining subsidence reservoirs that were created as a result of land subsidence over exploited hard coal seams and to determine the most predictive environmental factors that influence the distribution of mollusc species. The reservoirs are located in urbanised and industrialised areas along the Trans-Regional Highway, which has a high volume of vehicular traffic. They all have the same sources of supply but differ in the physical and chemical parameters of the water. In total, 15 mollusc species were recorded including four bivalve species. Among them Anodonta cygnea is classified as Endangered according to the Polish Red Data Book of Animals and also as Near Threatened according to the European Red List of Non-marine Molluscs. Eleven of the 15 mollusc species are included on the European Red List of Non-marine Molluscs as Least Concern. Conductivity, pH and the concentration of calcium were the parameters most associated with the distribution of mollusc species. Canonical correspondence analysis showed that Potamopyrgus antipodarum, Radix balthica, Physella acuta, Gyraulus crista and Pisidium casertanum were associated with higher conductivity and lower pH values. A. cygnea, Anodonta anatina and Ferrissia fragilis were negatively influenced by these parameters of the water. The results of this survey showed that the mining subsidence reservoirs located in urbanised and industrialised areas provide refuges for rare and legally protected species and that they play an essential role in the dispersal of alien species as well.
اظهر المزيد [+] اقل [-]Isolation and Characterization of an Erythromycin-Degrading Strain and Application for Bioaugmentation in a Biological Aerated Filter النص الكامل
2015
Gao, Pin | Wei, Xin | Gu, Chaochao | Wu, Xiaoqian | Xue, Gang | Shi, Weimin | Sun, Weimin
An erythromycin-degrading bacterium was isolated from the activated sludge of a sewage treatment plant (STP). Based on the morphological and physiological characteristics, the isolated strain was identified and named as Pseudomonas sp. ERY-E. In an inorganic salt medium inoculated at 1 % (v/v) of ERY-E strain containing 50 mg/L of erythromycin (ERY), the removal efficiency of ERY as high as 83.7 % was obtained under the optimum conditions with temperature of 30 °C, pH of 7.0, and 10 mg/L of yeast as the external carbon source. Subsequently, the ERY-E strain was used for bioaugmenting a biological aerated filter (BAF) to treat surface water containing low-concentration ERY. The influence of hydraulic retention time (HRT) and air-liquid ratio (A/L) on the performance of BAF was investigated. The average removal efficiencies of ERY and permanganate index (CODMₙ) were about 60.6 and 26.1 % in bioaugmented system (BAF₂) and 26.9 and 26.0 % in unbioaugmented system (BAF₁), respectively, under the optimum conditions with HRT of 4.0 h and A/L of 4:1 at steady state. Due to the stable removal of CODMₙ in BAF₂ as compared with BAF₁, it can be concluded that the introduction of ERY-E strain could collaborate with the indigenous microorganisms to attain a better ERY removal efficiency. As a result, the bioaugmented BAF method can be considered as an alternative technology for the treatment of surface water containing low-concentration emerging pollutants.
اظهر المزيد [+] اقل [-]Effect of Humic Acid on Arsenic Adsorption and Pore Blockage on Iron-Based Adsorbent النص الكامل
2015
Fakour, Hoda | Pan, Yi-Fong | Lin, Tsair-Fuh
The effect of humic acid (HA), on the adsorption and transport of arsenic (As) onto and within a model iron oxide-based adsorbent, iron oxide-coated diatomite (IOCD), is investigated. Experimental results indicate that the adsorption of both As and HA is highly pH-dependent. As uptake was suppressed by HA, with the level of suppression increasing with HA concentration. The suppression is attributed to the partial coverage of the adsorption sites, as confirmed by elemental analysis. Adsorption energy analysis indicates that for As(III), the main interaction with IOCD is physical adsorption, whereas for As(V), it is more likely ion exchange. The presence of HA may alter the adsorption energy and interaction of As with the adsorbent, particularly at higher HA concentrations. Kinetic results indicate that HA did not affect the diffusional transport of As in systems with both As and HA. However, for IOCD preloaded with HA, the adsorption kinetics of As was significantly slower, although the As uptake was similar to the conditions of co-sorption with HA. The slower kinetics and similar equilibrium uptake of As in the HA-preloaded IOCD system may be attributed to the partial blockage of the intraparticular pores within IOCD, which slowed down the diffusion of As.
اظهر المزيد [+] اقل [-]No delayed behavioral and phenotypic responses to experimental early-life lead exposure in great tits (Parus major) النص الكامل
2015
Ruuskanen, Suvi | Eeva, Tapio | Kotitalo, Päivi | Stauffer, Janina | Rainio, Miia
Early-life exposure to pollutants, such as lead, may have long-lasting consequences on health, behavior, and cognition. However, experiments on delayed effects of specific pollutants are very rare in wild animals. We experimentally exposed wild nestling great tits (Parus major) to dietary lead (high, low, or control group) in levels relevant to exposure levels of wild populations in Europe and studied delayed effects on phenotypic and behavioral traits in captivity. We also included a group of birds from a vicinity of a copper smelter, exposed to a mixture of toxic metals and altered food supply during development. This experimental setup allowed us to compare the strength of direct (exposure to lead per se) and indirect (pollution-related changes in diet) effects of pollutants. Our experimental lead treatment significantly increased lead levels in bone and feces compared with controls. However, we found no carry-over effect of early-life dietary lead on morphology, plumage coloration, or heat shock proteins. Treatment did not affect activity, exploration, neophobia, or success in learning and spatial memory task. We conclude that with the exposure levels and relatively short exposure period used, delayed effects on the measured traits were not found. However, it is important to further study other types of behavioral traits and ultimately fitness effects.
اظهر المزيد [+] اقل [-]Combining Passive Sampling with a GC-MS-Database Screening Tool to Assess Trace Organic Contamination of Rivers: a Pilot Study in Melbourne, Australia النص الكامل
2015
This study assessed the suitability of passive sampler extracts for use with a GC-MS-database rapid screening technique for around 940 organic chemicals. Chemcatcher™ passive sampler systems containing either Empore™ SDB-XC or C18FF disks were deployed at 21 riverine sites in and near Melbourne, Victoria, Australia, for a period of 28 days during September–October 2008. Methanolic elution of the SDB-XC and C18FF disks produced an extract that, after evaporation and inversion into hexane, was compatible with the GC-MS-database method enabling over 30 chemicals to be observed. The sources of the non-agricultural chemicals are still unclear, but this study was conducted in a relatively dry season where total rainfall was approximately 40 % lower than the long-term mean for the catchment during the study period. Thus, the risks may be greater in wetter seasons, as greater quantities of chemicals are likely to reach waterways as the frequency, extent and intensity of surface run-off events increase. This study provides valuable information for policy and decision-makers, both in Australia and other regions of the world, in that passive sampling can be conveniently used prior to analysis by multi-residue techniques to produce data to assess the likely risks trace organic chemicals pose to aquatic ecosystems.
اظهر المزيد [+] اقل [-]Sources of Mercury Exposure to Children in Low- and Middle-Income Countries النص الكامل
2015
Rita Ann Kampalath | Jennifer Ayla Jay
Background. Many children in low- and middle-income countries face enhanced risks of exposure to contaminants via the environment, parental occupation, and other routes. While mercury (Hg) is a global pollutant whose transport properties allow it to have an impact even in pristine areas, the presence of significant Hg sources in the developing world can cause localized effects that are more severe than those observed in other areas. Objectives. This paper provides a narrative review of sources of Hg exposure to people in the developing world with a particular focus on children, and presents an overview of key aspects to this important issue. Methods. We searched Web of Knowledge and Google Scholar using keywords including combinations of “mercury” and one or more of the following: “children,” “exposure,” “breast milk,” “artisanal mining,” “prenatal,” “religion,” “medicine,” “dental amalgam,” “chlor-alkali,” “VCM,” “vaccine,” “e-waste,” “industry,” “beauty,” “cosmetics,” “strategies,” “child labor,” “costs,” and “developing countries” to find peer-reviewed articles pertaining to Hg exposure in the developing world. Results. Sources of Hg exposure include mining, consumption, industrial operations, religious practices, traditional medicines, beauty products, vaccines, dental amalgams, and waste scavenging and recycling. Conclusion. Children in the developing world are often subject to higher levels of Hg exposure than those living in developed countries due to the higher prevalence of Hg-intensive industrial processes and consumer products, lack of environmental regulation, and limits in mobility and food choices, among other factors. This issue can be addressed through additional research to fill in data gaps on exposure sources, establish sound and enforceable policies, and increase education and participation in affected communities. Challenges to addressing this problem include limited resources for needed equipment, training, and manpower to implement solutions. Competing Interests. The authors declare no competing financial interests.
اظهر المزيد [+] اقل [-]E-waste: A Challenge for Sustainable Development النص الكامل
2015
Md. Sahadat Hossain | Sulala M.Z.F. Al-Hamadani | Md. Toufiqur Rahman
Background. E-waste has been identified as the fastest growing waste stream in the world at present. Rapid socio-economic development and technological advancement are the main drivers of this trend. The hazardous chemical components of e-waste have potential adverse impacts on ecosystems and human health if not managed properly. This represents an imminent challenge to achieving sustainable development goals. Although technologically developed countries are the main source of e-product production and e-waste generation, the generated volume has also been increasing in developing countries and those in transition due to transport and transfer from e-waste source countries. Consequently, developing countries are in a vulnerable situation due to their lack of inventory data, waste management policies and advanced technology for environmentally sound management. Objectives. This study aims to demonstrate that the present global e-waste scenarios and health hazards could prolong the achievement of sustainable development targets. This study illustrates scenarios from different perspectives and raises concerns about e-waste, identifies information gaps, and provides a basis for knowledge and awareness building and technological improvement to facilitate global long-term sustainable development. Discussion. Total and per capita global e-waste generation has been increased along with socio-economic development. These products present a significant global challenge due to the hazardous chemicals they contain, their highly technical recycling requirements and the high overhead and costs of environmentally sound management, as well as their adverse impacts to human health. Although high-income countries are the main sources of this waste, low-income countries are experiencing an increase in e-waste due to the shifting process of both recently produced and used electric and electronic equipment (UEEE), as well as cheap management overhead costs. Consequently, they bear the greatest burden of adverse health hazards and ecosystem degradation, prolonging their achievement of sustainable development goals. Conclusions. Sustainability is being prioritized for all development activities by integrating societal, economic, environmental, technological, cultural, and gender perspectives. Considering the adverse potential eco-toxicological impacts and diverse health effects of e-waste, an urgent global multilateral agreement is needed addressing its management (i.e., handling, storage, transportation, recycling, and final disposal), whether by land filling or incineration. Due to the global nature of the issue and the difficulty of establishing sustainable and environmentally sound processing of e-waste in low-income countries, multinational negotiation and collaboration is the only realistic solution. Furthermore, comprehensive global e-waste management and policies could help to off-set the hazards of e-waste and are the best approach for achieving sustainable development.
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