Celosia trigyna, which belongs to the plant family Amaranthaceae, is a plant used in traditional medicine to treat several conditions such as sores, chest pains, diarrhoea and menstrual cramps in many countries in Africa. It is also consumed by the local people in Nigeria as soups, sauces and stews. In this study, the distribution and bioaccumulation of the elements in C. trigyna species and growth soil from the western and northern regions of Nigeria was investigated to determine the effects of geographical location on the uptake of elements by the plant. Elemental concentrations in the leaves from the western region were found to be in decreasing order of Ca?>?Mg?>?Fe?>?Mn?>?Zn?>?Cu?>?Pb?>?As?>?Ni. Concentrations of elements in the leaves from the northern region were found to be in decreasing order of Ca?>?Mg?>?Fe?>?Mn?>?Zn?> Cu?>?As?>?Pb?>?Ni?>?Co?>?Cd. Proximate analysis of leaves from both regions compared well with the recommended dietary allowance making the leaves safe for human consumption. Principal component analysis was used to group elements having the same sources irrespective of their geographical locations. Cd, Co and Cr were not detected in the leaves from the western region. Concentrations of As and Pb were above maximum permissible limits in both regions, while Ayegunle and Bida (in the northern region) had the highest concentrations of Cd. The high level of these toxic metals may be attributed to anthropogenic activities. It is therefore important that the Nigerian agricultural extension system emphasizes the dangers of heavy metal contamination in leafy vegetables to farmers. Activities of the manufacturing industries in the study area should be adequately monitored under standard environmental protection laws. 相似文献
The oxidation of imidazolium (1-hexyl-3-methylimidazolium chloride, HmimCl) and pyridinium (1-butyl-4-methylpyridinium chloride, BmpyrCl) ionic liquids (ILs) by Fenton’s reagent has been studied. Complete conversion was achieved for both ILs using the stoichiometric H2O2 dose at 70 °C, reaching final TOC conversion values around 45 and 55% for HmimCl and BmpyrCl, respectively. The decrease in hydrogen peroxide dose to substoichiometric concentrations (20–80% stoichiometric dose) caused a decrease in TOC conversion and COD removal and the appearance of hydroxylated oxidation by-products. Working at these substoichiometric H2O2 doses allowed the depiction of a possible degradation pathway for the oxidation of both imidazolium and pyridinium ILs. The first step of the oxidation process consisted in the hydroxylation of the ionic liquid by the attack of the ·OH radicals, followed by the ring-opening and the formation of short-chain organic acids, which could be partially oxidized up to CO2 and H2O. At H2O2 doses near stoichiometric values (80%), the resulting effluents showed non-ecotoxic behaviour and more biodegradable character (BOD5/COD ratio around 0.38 and 0.58 for HmimCl and BmpyrCl, respectively) due to the formation of short-chain organic acids.
The idea of sustainability is intrinsically normative. Thus, understanding the role of normativity in sustainability discourses is crucial for further developing sustainability science. In this article, we analyze three important documents that aim to advance sustainability and explore how they organize norms in relation to sustainability. The three documents are: the Pope’s Encyclical Laudato Si’, the Sustainable Development Goals and the Paris Agreement. We show that understanding the role of different types of norms in the three documents can help understand normative features of both scientific and non-scientific sustainability discourses. We present the diverse system of norms in a model that interrelates three different levels: macro, meso, and micro. Our model highlights how several processes affect the normative orientation of nations and societies at the meso-level in different ways. For instance, individual ethical norms at the micro-level, such as personal responsibility, may help decelerate unsustainable consumerism at the aggregate meso-level. We also show that techno-scientific norms at the macro-level representing global indicators for sustainability may accelerate innovations. We suggest that our model can help better organize normative features of sustainability discourses and, therefore, to contribute to the further development of sustainability science. 相似文献
The semi-arid Amboseli landscape, southern Kenya, is characterised by intermittent groundwater-fed wetlands that form sedimentary geoarchives recording past ecosystem changes. We present a 5000-year environmental history of a radiocarbon dated sediment core from Esambu Swamp adjacent to Amboseli National Park. Although radiocarbon dates suggest an unconformity or sedimentary gap that spans between 3800 and 500 cal year BP, the record provides a unique insight into the long-term ecosystem history and wetland processes, particularly the past 500 years. Climatic shifts, fire activity and recent anthropogenic activity drive changes in ecosystem composition. Prior to 3800 cal year BP the pollen data suggest semi-arid savanna ecosystem persisted near the wetland. The wetland transgressed at some time between 3800 and 500 cal year BP and it is difficult to constrain this timing further, and palustrine peaty sediments have accumulated since 400 cal year BP. Increased abundance of Afromontane forest taxa from adjacent highlands of Kilimanjaro and the Chyulu Hills and local arboreal taxa reflect changes in regional moisture budgets. Particularly transformative changes occurred in the last five centuries, associated with increased local biomass burning coeval with the arrival of Maa-speaking pastoralists and intensification of the ivory trade. Cereal crops occurred consistently from around 300 cal year BP, indicative of further anthropogenic activity. The study provides unique insight in Amboseli ecosystem history and the link between ecosystem drivers of change. Such long-term perspectives are crucial for future climate change and associated livelihood impacts, so that suitable responses to ensure sustainable management practices can be developed in an important conservation landscape. 相似文献
Access to extractive resources relies as much on technology and prices as it does on the power to designate ecological and economic meanings to water and other environmental goods. This paper examines the ways in which the mining industry uses scientific models to create meanings for water that in turn legitimizes their access to and control over it. To do so, this paper explores the relevance of combining biophysical analyses—in this case water metabolism—with an examination of those power relations and social constructions that coexist with and affect the flows of water. Based on empirical research, this paper analyzes the evolution of water management in the process of copper production at the Cobre las Cruces mine in southern Spain to identify present contradictions in the strategies adopted by the mining company to avoid water degradation. These contradictions are revealed by examining how water has been framed as a resource not susceptible to being used for purposes other than mining processes. We argue that those framing this environmental explanation—the regional government and the mining industry—are promoting net subtractions of water from an aquifer against current regulations. 相似文献
IntroductionWhen studying the effects of organochlorine compounds (OCs) on human health it is common to correct serum concentrations of OC by total lipids (TL). However, the relationship between serum OCs and serum TL is far from established in many diseases, including several cancers. Our aim was to analyze the relationship between serum OC and TL in patients with pancreatic ductal adenocarcinoma (PDA), and to explore several alternatives to perform the OC lipid correction.MethodsIncident cases of PDA were interviewed and had blood drawn soon around hospital admission (n = 144). Serum concentrations of OCs were analysed by high-resolution gas chromatography with electron-capture detection.ResultsMost patients with high TL had moderate or low concentrations of OCs. By contrast, the variability of OC values among patients with normal TL was large. Correlations were of a similar magnitude between OC and TL and between OC and total cholesterol; while these correlations were weak (all Spearman's ρ < 0.3 and R2 < 0.11), no OC were significantly correlated with triglycerides. Although all alternatives to the OC/TL linear ratio were statistically significant for at least one OC, their R2 was always below 10%.ConclusionsIn patients with severe diseases as PDA, linear correction of OC by TL as commonly performed in epidemiologic studies may be inappropriate. Results contribute to the scant literature on the rationale to correct serum concentrations of OC by lipids. They suggest that it is unwarranted to routinely correct OC by TL, offer ways to assess such need, and present alternatives as no TL correction, correction by total cholesterol only or use of different statistical models. 相似文献
After urban sources, mineral dust in Madrid is the second biggest contributor to PM10, making up 40% on average, of total emissions. Approximately, 50% of the days on which the daily limit of 50 μg m?3 marked by the European Directive, are ascribable to Saharan outbreaks. The present study has focused on individual particle characterization of North African dust over Madrid by SEM/EDX, since no previous works on this type of characterization have been found in the region. More than 30,000 particles from 6 different samples have been measured to characterize 4 African episodes with very different meteorological scenarios, transport processes and source origins. Different samples from the same episode have also been characterized to evaluate homogeneity of dust characteristics over time. Silicates, mainly composed of clay minerals, are the main component, with abundances ranging from 65 to 85% by particle volume. Chemical cluster distribution of silicates has been linked to the major topsoil mineralogical composition in the origin of the episodes. Aspect Ratio (AR) has been used to compare particle morphology between episodes. AR values from samples taken under the same scenarios are statistically equal. For all the samples and size ranges AR values are found to be in the same order: ARsulphates > ARsilicates > ARcarbonates. Particles not only maintained morphology during the episode, but also chemical composition, since clusters turned out to be very similar in samples taken on the same day and different days. Similarities and differences in particle chemical composition and morphology between the different transport patterns are discussed in detail throughout the paper. 相似文献
The study of light-duty diesel engine exhaust emissions is important due to their impact on atmospheric chemistry and air pollution. In this study, both the gas and the particulate phase of fuel exhaust were analyzed to investigate the effects of diesel reformulation and engine operating parameters. The research was focused on polycyclic aromatic hydrocarbon (PAH) compounds on particulate phase due to their high toxicity. These were analyzed using a gas chromatography–mass spectrometry (GC–MS) methodology.Although PAH profiles changed for diesel fuels with low-sulfur content and different percentages of aromatic hydrocarbons (5–25%), no significant differences for total PAH concentrations were detected. However, rape oil methyl ester biodiesel showed a greater number of PAH compounds, but in lower concentrations (close to 50%) than the reformulated diesel fuels. In addition, four engine operating conditions were evaluated, and the results showed that, during cold start, higher concentrations were observed for high molecular weight PAHs than during idling cycle and that the acceleration cycles provided higher concentrations than the steady-state conditions. Correlations between particulate PAHs and gas phase products were also observed.The emission of PAH compounds from the incomplete combustion of diesel fuel depended greatly on the source of the fuel and the driving patterns. 相似文献
Twenty-three soft drink samples (i.e., four pineapple-based fruit drinks, eight citrus-based fruit juices, one soya-based drink, three cola carbonated drinks, one apple-based fruit drink, and six cocktail fruit drinks) were randomly purchased from retail outlets in an urban market in Accra and analyzed for the concentrations of iron, cobalt, cadmium, zinc, lead, and copper using flame atomic absorption spectrometry. The mean concentration of iron and cadmium were 0.723?±?0.448 mg/L and 0.032?±?0.012 mg/L, respectively. The mean cobalt concentration was 0.071?±?0.049 mg/L, while the mean Zn concentration in the samples was 0.060?±?0.097 mg/L. The mean concentrations of Pb and Cu in the fruit juice samples were 0.178?±?0.091 mg/L and 0.053?±?0.063 mg/L respectively. About 78 % of the samples exceeded the United States Environmental Protection Agency (USEPA) maximum contaminant level of 0.3 mg/L prescribed for iron, whereas all the samples exceeded the USEPA maximum contaminant level of 0.005 mg/L prescribed for cadmium. About 91 % of the samples exceeded the EU maximum contaminant level prescribed for lead insoft drinks. 相似文献