1,721,057 research outputs found
Sewage sludge in Europe and in the UK: environmental impact and improved standards for recycling and recovery to land
No full textSewage treatment and sewage sludge (also called biosolids) represent a serious environmental issue that has affected modern society for the past century. In response to this, an increasing number of controls and resulting regulations have been introduced to avoid polluting our rivers and seas with pathogens, oxygen-demanding organic debris, potentially toxic elements (PTEs) and eutrophying nutrients. Over the past few decades, improved technology and more stringent regulations, driven in Europe by the increasingly precautionary European Community (EC) legislation, have worked together to achieve a net decrease of the amount of some of the pollutants, both through treatment of the wastewater and by cutting or forbidding the intake of contaminants at source. The growing importance of cleaning up wastewater before returning it to natural waters has led to (1) a vast increase of the quantity and the quality of the sludge resulting from the treatment of wastewater, with a greater amount of pollutants removed during the treatment process; (2) a greater effort towards the reuse and recycling of the sludge as opposed to disposal (e.g. landfilling, incineration). One of the consequences of this situation is a rising interest in using soils (agricultural or not) to address the latter through various applications. In fact, as the sludge has to be disposed off safely, soils can be used as a system of assimilating, recycling or disposing off the sewage sludge. Science and legislation are trying to provide the safest possible route to accomplish these targets, but the subject is not free from controversy, often causing hot debates between the interested parties. This chapter aims to review the improved standards achieved with sewage sludge, touching in particular the British experience in the field of regulating the disposal and reuse of these materials
Decomposition of carboxymethyl cellulose based on nano-knife principle
No full textThe traditional degradation of organic pollutants is based on the sacrifice of chemical or biological reagents. In this study, a purely physical technique was developed to break the chemical bonds and consequently decompose macromolecules in aqueous solution. Assisted with a high-speed mechanical blade, refined quartz sand grains with particularly sharp nano-scale edges can act as 'nano-knives', which are able to cut the long chain of carboxymethyl cellulose (CMC, as a model molecule). High performance size exclusion chromatography measurements evidenced that the original CMC molecules (41,000 Da) were decomposed into a series of smaller molecules (460, 1000, 2200, 21,000, 27,000 and 31,000 Da). Consequently, the initial viscosity of the CMC solution (2 g/L) rapidly decreased by approximately 50% after 3 min treatment by the nano-knife materials along with the mechanical blade. Fourier transform infrared (FTIR) spectra indicated that the original functional groups were still present and new functional groups were not produced after shearing. The intensity of the main functional group beta-1-4-glycosidic bond (wavenumber 1062 cm(-1)) was observed to markedly decrease after shearing. These results indicated that the long-chain CMC was cleaved into short-chain CMC. A degradation mechanism was proposed whereby the cutting force generated by the rapid motion of the nano-knives may be responsible for the breakage of beta-1-4-glycosidic bonds in the macromolecular cellulose backbone. These results provide support for a potentially more affordable and environment-friendly strategy for physical-based decomposition of recalcitrant organic pollutants from aqueous solution without the need of chemical or biological reagents. (C) 2018 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V
Baseline geochemical mapping of sardinia (Italy)
No full textA total of about 20,000 stream sediment samples from about 13,000 km(2) were collected in Sardinia and analysed for eleven elements (Ag, Co, Cr, Cu, F, Hg, Mn, Mo, Ni, Pb, Sb and Zn) by Ente Minerario Sardo (EMS), aimed at mineral exploration We have reutilized 16,890 samples (covering an area of 7987 km(2)) of the above data to compile geochemical baseline maps for all single elements as well as maps showing the regional variability of factor scores resulting from R-mode factor analysis. This type of maps has a particular relevance to environmental issues, especially in a region such as Sardinia which has been mined since pre-Roman times. (C) 1997 Elsevier Science B.V
Models of Geochemical Speciation: Structure and Applications
No full textBeing able to predict the behavior of trace elements in the environment is crucial for environmental risk assessment studies. For this reason, modeling, in addition to experimental methods, has become an indispensable tool to better understand the (bio)-geochemistry of trace elements and the processes involved in their availability, transport and ecotoxicity. In this chapter we briefly outline the development of geochemical modeling over time and its basic principles. A comprehensive description of the state-of-the-art ion-binding and surface complexation models presently available for dissolved and particulate organic matter, metal (hydr)oxides of aluminum, iron, manganese and silica and clay minerals is given. A significant part of this chapter is dedicated to the application of these models for studying surface waters and soils. The most common model platforms used for this purpose together with the available (thermodynamic) databases of model parameters are summarized. In two separate sections we highlight the application of an assemblage model (with submodels for the various adsorbents) to describe trace element solid-solution partitioning and speciation in surface waters and soils; here particular attention is given to the derivation of site-specific inputs concerning the geochemical reactive metal content and the contents of adsorbents metal (hydr)oxides, clay and organic matter). Consideration is therefore given to the most recent developments in bio-geochemical modeling to link metal speciation to bioavailability, biotic accumulation and toxicity. Finally, future prospects of geochemical modeling are discussed, giving an overview of the potential directions for development
Models of geochemical speciation: Structure and applications
No full textBeing able to predict the behavior of trace elements in the environment is crucial for environmental risk assessment studies. For this reason, modeling, in addition to experimental methods, has become an indispensable tool to better understand the (bio)-geochemistry of trace elements and the processes involved in their availability, transport, and ecotoxicity. In this chapter, we briefly outline the development of geochemical modeling over time and its basic principles. A comprehensive description of the state-of-the-art ion-binding and surface complexation models presently available for dissolved and particulate organic matter, mineral oxides of aluminium, iron, manganese, and silica and clay minerals is given. A significant part of this chapter is dedicated to the application of these models for studying surface waters and soils. The most common model platforms used for this purpose together with the available (thermodynamic) databases of model parameters are summarized. In two separate sections we highlight the application of an assemblage model (with submodels for the various adsorbents) to describe trace element solid-solution partitioning and speciation in surface waters and soils; here particular attention is given to the derivation of site-specific inputs concerning the geochemical reactive metal content and the contents of adsorbents (mineral oxides, clay, and organic matter). Consideration is therefore given to the most recent developments in bio-geochemical modeling to link metal speciation to bioavailability, biotic accumulation, and toxicity. Finally, future prospects of geochemical modeling are discussed, giving an overview of the potential directions for development
Extraction and characterization of pore water from contaminated soils
No full textChemical elements that are either present naturally in the soil or introduced by pollution are more usefully estimated in terms of “availability” of the element since it is this property that can be related to mobility and uptake by plants. A good estimate of the immediately available fraction can be achieved by measuring the concentration, or activity, of chemical species in soil pore water. Current analytical techniques enable the application of this approach to trace elements, such as plant and animal micronutrients, and those defined as potentially toxic elements (PTE) in environmental studies. A complete chemical analysis of soil pore water represents a powerful diagnostic tool for the interpretation of many soil chemical phenomena relating to soil fertility, mineralogy, and environmental fate. This chapter describes some of the current methodologies used to extract soil pore water. In particular, five laboratory-based methods, (i) high-speed centrifugation-filtration, (ii) low (negative-) pressure Rhizon samplers and passive diffusion samplers (Micro-Dialysis Probes MDPs), (iii) high-pressure soil squeezing, (iv) equilibration of dilute soil suspensions, and (v) Diffusive Gradients in Thin-films (DGT), are described and discussed in detail. Several operational factors are presented: pressure applicable (i.e., pore size accessed), moisture prerequisites of the soil, pore water yield, efficiency, duration of extraction, materials, and possible sources of contamination for micronutrient and PTE studies. There is also consideration of the advantages and disadvantages of the methods, including costs and material availability
Geogenic versus anthropogenic behaviour and geochemical footprint of Al, Na, K and P in the Campania region (Southern Italy) soils through compositional data analysis and enrichment factor
Full text linkGeochemical studies that focus on environmental applications tend to approach the chemical elements as individual entities and may therefore offer only partial and sometimes biased interpretations of their distributions and behaviour. A potential alternative approach is to consider a compositional data analysis, where every element is part of a whole. In this study, an integrated methodology, which included compositional data analysis, multifractal data transformations and interpolation, as well as enrichment factor analysis, was applied to a geochemical dataset for the Campania region, in the south of Italy, focusing in particular on the behaviour, footprints and sources of a smaller pool of elements: Al, Na, K and P. The initial dataset included 3669 topsoil samples, collected at an average sampling density of 1 site per 2.3 km2, and analyzed (after an aqua regia extraction) by a combination of ICP-AES and ICP-MS for 53 elements. Frequency based methods (Clr biplot, Enrichment Factor computation) and frequency spatial-method (fractal and multifractal plots) allowed identifying the relationships between the elements and their possible source patterns in Campania soils in relation to a natural occurring concentrations in geogenic material (rocks, soils and sediments) or human input. Results showed how the interpretation of concentration and behaviour of Al, Na, K and P was enhanced thanks to the application of data log-ratio transformation in univariate and multivariate analysis compared to the use of raw or log-normal data. Multivariate analyses with compositional biplot allowed the identification of four element associations and their potential association with the underling geology and/or human activities. When focusing on the smaller pool of elements (Al, P, K and Na), these relationships with the unique geology of the region, were largely confirmed by multifractal interpolated maps. However, when the local background was used for the calculation of the enrichment factor, the resulting interpolated maps allowed to identify smaller areas where the greater concentrations of P could not be possibly associated to a mineralisation (e.g., ultrapotassic rocks) but were more likely to be associated to anthropogenic input such as agriculture activities with potentially extensive use of phosphate fertilizers. The integrated approach of this study allowed a more robust qualitative and quantitative evaluation of elemental concentration, providing in particular new and vital information on the distribution and patterns of P in soils of the Campania region, but also a viable, more robust, methodological approach to regional environmental geochemistry studies
Field sampling of soil pore water to evaluate the mobile fraction of trace elements in the Iglesiente area (SW Sardinia, Italy)
Full text linkField soil pore water monitoring was applied in a highly heavy-metal contaminated area in SW Sardinia, Italy, as a direct, realistic measure of heavy metal mobility. The main chemistry of pore waters well reflects the local characteristics of soils, ranging from Ca-SO4 to (Ca)Mg-HCO3 to Ca(Na)-SO4(CI), with a wide range of conductivity. The mobility of Zn and Pb is apparently controlled by equilibrium with minerals such as hydrozincite or smith-sonite, and cerussite, respectively. These results allow a correct estimate of the actual environmental risk associated with the presence of heavy metals in soils, and may serve as a supporting tool for phytoremediation planning. (C) 2015 Elsevier B.V. All rights reserved
Mercury speciation in environmental samples associated with artisanal small-scale gold mines using a novel solid-phase extraction approach to sample collection and preservation
Full text linkIn artisanal small-scale gold mines (ASGM), mercury (Hg) is known to pollute nearby river waters and sediments where it can be methylated to the highly bioavailable methylmercury (MeHg). The assessment of Hg speciation in water samples has been challenging for many years, with recommended procedures often not adequately allowing for analysis of samples in a suitable timeframe. Using a novel solid-phase extraction (SPE) method for sampling and preservation of Hg species, representative speciation data can be safely and easily collected and retained for up to 4-weeks (MeHg = 115 +/- 8% refrigerated and 109 +/- 13% unrefrigerated storage; Hg2+ = 100 +/- 14% refrigerated and 94 +/- 12% unrefrigerated storage). Concentrations of MeHg in environmental water samples and drinking water were below detection limit across two ASGM sites in western Kenya and concentrations of Hg2+ were below drinking water guidelines; however, drinking water sources contribute 20-30% of the tolerable weekly intake of Hg, indicating a need to minimise exposure of Hg from dietary sources to prevent Hg poisoning. Sediments from receiving rivers at ASGM sites showed total Hg concentrations above guideline limits (0.08-1.84 mg kg-1 total Hg) along the length of the river; however, MeHg concentrations fluctuated dependent on the stagnation of the river due to damns and ponds (5.9 +/- 14.3 mu g kg-1 MeHg). The findings show that SPE can be used as a robust sample collection and preservation approach for Hg speciation, which can better inform mitigation measures, understand ecological and human health implications, and improve environmental monitoring
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