Comparison of batch leaching tests and influence of pH on the release of metals from construction and demolition wastes

Construction and demolition wastes are suitable for use in road construction. However, leaching characterization of recycled materials is required to determine their pollutant potential and the consequence of their application in different scenarios. The motivation of this paper is derived from the increasing use of different leaching test methods. In Europe, the confusion resulting from the wide variety of tests used to evaluate environmental properties of construction materials implies that an evaluation of the current practices and the attempt to consolidate the approaches are required.Two equilibrium-based leaching tests (the Dutch test and the European standard) were conducted to assess the environmental impact of four recycled aggregates. Three natural limestone aggregates were used as controls. Both tests measure the potential release of hazardous elements under extreme conditions using different leaching parameters (L/S ratio, pH value and contact time). The results proved that pH is the most relevant factor on the assessment of the differences between leaching methods due to its strong control on the pollutant release.To classify the materials according to their environmental effects, the concentration limit values of the metals imposed by Council Decision 2003/33/EC were used as a reference. The comparison allowed the classification of the recycled aggregates as inert wastes, with the exception of the MR-2 aggregate, which was classified as non-hazardous material.     

Trace metal dynamics in an industrialized Brazilian river: A combined application of Zn isotopes, geochemical partitioning, and multivariate statistics

The Paraiba do Sul (PSR) and Guandu Rivers (GR) water diversion system (120 km long) is located in the main industrial pole of Brazil and supplies drinking water for 9.4 million people in the metropolitan region of Rio de Janeiro. This study aims to discern the trace metals dynamics in this complex aquatic system. We used a combined approach of geochemical tools such as geochemical partitioning, Zn isotopes signatures, and multivariate statistics. Zinc and Pb concentrations in Suspended Particulate Matter (SPM) and sediments were considerably higher in some sites. The sediment partition of As, Cr, and Cu revealed the residual fraction (F4) as the main fraction for these elements, indicating low mobility. Zinc and Pb were mostly associated with the exchangeable/carbonate (F1) and the reducible (F2) fractions, respectively, implying a higher susceptibility of these elements to being released from sediments. Zinc isotopic compositions of sediments and SPM fell in a binary mixing source process between lithogenic (δ^66/64Zn_JMC ≈ + 0.30‰) and anthropogenic (δ^66/64Zn_JMC ≈ + 0.15‰) end members. The lighter δ^66/64Zn_JMC values accompanied by high Zn concentrations in exchangeable/carbonate fraction (ZnF1) enable the tracking of Zn anthropogenic sources in the studied rivers. Overall, the results indicated that Hg, Pb, and Zn had a dominant anthropogenic origin linked to the industrial activities, while As, Cr, and Cu were mainly associated with lithogenic sources. This work demonstrates how integrating geochemical tools is valuable for assessing geochemical processes and mixing source effects in anthropized river watersheds.     

Poly(lactic acid)/Cellulose Composites Obtained from Modified Cotton Fibers by Successive Acid Hydrolysis

This work is focused on the hydrolysis of cotton fibers from waste textiles to obtain micro and nanofibers to be used as reinforcements in polymer composites. To promote their compatibility with polymeric matrix, hydrolyzed cotton fibers were surface modified with various silane compounds. Thus, these fibers were mixed with commercial poly(lactic acid) (PLA) at 5% w/w loading by melt compounding. Acid treatments caused a decrease of the crystallinity index whereas the thermal stability was significantly improved, especially for cellulose fibers hydrolyzed in two steps. Morphological analysis revealed a reduction of the fibers diameter and a decrease of their length as a consequence of the hydrolysis. NMR analysis confirmed the silanization of the fibers by reaction with the silane agent. Tensile tests revealed that silanization treatments were able to increase the composite Young’s modulus and the stress at break with respect to the neat matrix, indicating that silanization improved the polymer/fiber compatibility interfacial adhesion. The overall results demonstrated that applying suitable surface modification strategies, waste cotton textiles can be effectively recycled as fillers in polymer based composites.     

Intensification of the ultrafiltration of real oil-contaminated (produced) water with pre-ozonation and/or with TiO2, TiO2/CNT nanomaterial-coated membrane surfaces

Environmental Science and Pollution Research - In the present study, commercial PES, PVDF, PTFE ultrafilter membranes, and two different nanomaterial (TiO2 and TiO2/CNT composite)-covered PVDF...     

Removal of pharmaceutical compounds from urban wastewater by an advanced bio-oxidation process based on fungi <Emphasis Type="Italic">Trametes versicolor</Emphasis> immobilized in a continuous RBC system

Conventional wastewater treatment plants (WWTPs) are not able to remove completely some emerging contaminants, such as residual pharmaceutical compounds (PCs) with potential ecotoxicity to water bodies. An advanced bio-oxidation process (ABOP) using white-rot fungi (WRF) has been proposed as alternative biological treatment for degradation of non-biodegradable compounds. A synthetic and real wastewater spiked with 12 PCs at 50 μg L^?1 was treated by means of ABOP based on WRF in a rotating biological contactor (RBC) at 1 day of hydraulic retention time (HRT). The ABOP achieved a remarkable biological performance in terms of TOC removal and reduction of N-NH₄ ⁺ and P-PO₄ ^3? nutrients. Likewise, 5 of the 12 PCs were eliminated with removal efficiencies ranging from 80 to 95%, whereas 6 of 12 PCs were eliminated with removal values ranging from 50 to 70%. The anaerobic digestion of the fungal sludge generated upon the treatment was also evaluated, obtaining a methane yield of 250 mL CH₄ g_VS ^?1. These results evidenced that the proposed ABOP is a promising alternative for the sustainable wastewater treatment of urban effluents, combining advanced oxidation with biological operation for the removal of emerging PCs and energy recovery.     

Natural concentrations and reference values of heavy metals in sedimentary soils in the Brazilian Amazon

The soils of the Brazilian Amazon exhibit large geochemical diversity reflecting the different soil formation processes in an area covering 49% of the Brazilian territory. Soil contamination by heavy metals is one of the threats to the sustainability of this Biome but establishing quality reference values (QRVs) for the region is a challenging owing to the immense territorial area of the Amazon. This study aimed to determine the natural background of heavy metals in soils from the southwestern Brazilian Amazon in order to propose QRVs for Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, and Zn for alluvial sedimentary soils. One hundred and twenty-eight soil samples were collected at a depth of 0.0–0.2 m in sites with minimal anthropogenic interference. Soil sample digestion was based on the EPA 3051A method and metal concentrations were determined by ICP-OES. QRVs calculated for the southwestern Brazilian Amazon are among the lowest recorded in Brazil (mg kg^?1): Ba (16.5), Cd (0.1), Cr (6.9), Cu (2.8), Fe (15.4), Mn (13.4), Ni (1.7), Pb (4.4), Sb (0.9), and Zn (5.7). The low metal concentration is likely a result of the sedimentary origin of the soils. The results of this study can serve as a basis for defining public policies to investigate the environmental impacts resulting from changes in land use in areas of the Brazilian Amazon.     

Adapting to urban challenges in the Amazon: flood risk and infrastructure deficiencies in Belém,Brazil

Regional Environmental Change - Sustainable urban infrastructure transition is perhaps the biggest challenge confronting cities in the global south in a time of climate change. Fast-growing cities...     

Comparison of USEPA digestion methods to heavy metals in soil samples

The use of appropriate analytical methods is of paramount importance for risk assessment and monitoring of potentially toxic metals in soils. In this sense, the objective of this study was to compare the effectiveness of two sample digestion methods, recommended by the Brazilian legislation for the management of contaminated areas (CONAMA 2009), aiming at the determination of environmentally available metal concentrations (USEPA 3050B, USEPA 3051A), as well as a total digestion method (USEPA 3052). Samples from 10 classes of soils were analyzed for Cu, Zn, Cd, Pb, Ni, and Hg. The results showed that the USEPA method 3051A is more efficient than the USEPA method 3050B in the extraction of levels considered environmentally available of Zn, Cu, Cd, Pb, and Ni. Besides providing a higher recovery of these elements, the method requires shorter digestion time, lower consumption of acids, and reduced risk of contamination. The USEPA method 3051A showed greater efficiency in Hg extraction in soils with higher clay content. Therefore, it is suitable for situations where a wide range of soils with different mineralogical characteristics are analyzed or in order to decrease the losses due to volatilization of the element in open systems.     

Biogeochemical indicators of elevated nitrogen deposition in semiarid Mediterranean ecosystems

Nitrogen (N) deposition has doubled the natural N inputs received by ecosystems through biological N fixation and is currently a global problem that is affecting the Mediterranean regions. We evaluated the existing relationships between increased atmospheric N deposition and biogeochemical indicators related to soil chemical factors and cryptogam species across semiarid central, southern, and eastern Spain. The cryptogam species studied were the biocrust-forming species Pleurochaete squarrosa (moss) and Cladonia foliacea (lichen). Sampling sites were chosen in Quercus coccifera (kermes oak) shrublands and Pinus halepensis (Aleppo pine) forests to cover a range of inorganic N deposition representative of the levels found in the Iberian Peninsula (between 4.4 and 8.1 kg N ha^?1 year^?1). We extended the ambient N deposition gradient by including experimental plots to which N had been added for 3 years at rates of 10, 20, and 50 kg N ha^?1 year^?1. Overall, N deposition (extant plus simulated) increased soil inorganic N availability and caused soil acidification. Nitrogen deposition increased phosphomonoesterase (PME) enzyme activity and PME/nitrate reductase (NR) ratio in both species, whereas the NR activity was reduced only in the moss. Responses of PME and NR activities were attributed to an induced N to phosphorus imbalance and to N saturation, respectively. When only considering the ambient N deposition, soil organic C and N contents were positively related to N deposition, a response driven by pine forests. The PME/NR ratios of the moss were better predictors of N deposition rates than PME or NR activities alone in shrublands, whereas no correlation between N deposition and the lichen physiology was observed. We conclude that integrative physiological measurements, such as PME/NR ratios, measured on sensitive species such as P. squarrosa, can provide useful data for national-scale biomonitoring programs, whereas soil acidification and soil C and N storage could be useful as additional corroborating ecosystem indicators of chronic N pollution.     

Buccal micronucleus cytome assay of populations under chronic heavy metal and other metal exposure along the Santiago River,Mexico

The Santiago River is one of the most contaminated rivers in Mexico, with heavy metal levels above the allowed limits. Scientific evidence indicates that chronic heavy metal exposure leads to cytogenotoxic effects. The aims of this study were to evaluate the genotoxic and cytotoxic effects of such exposure in buccal mucosa cells by micronucleus (MN) assay and to identify other nuclear abnormalities (NAs), such as nuclear buds (NBUDs), binucleated cells (BNs), pyknotic nuclei (PNs), karyorrhexis (KX), karyolysis (KL), and abnormally condensed chromatin (CC). Assays were performed on samples from four populations located alongside the Santiago River that are under chronic exposure to heavy metals and other metals (HMMs), and the results were compared with those of a population without exposure to HMMs. The exposed group showed increased frequencies of NAs (KX, CC, and KL), which are associated with cytotoxic damage, and NBUDs, which are associated with genotoxic damage. Increased frequencies of NBUDs and CC were observed in subjects from El Salto/Juanacatlán, Ocotlán, and Paso de Guadalupe, and an increase in KX frequency was observed in subjects from El Salto/Juanacatlán. Significant differences in KL frequency were observed in subjects from La Barca, El Salto/Juanacatlán, Paso de Guadalupe, and Ocotlán. Predictors for increased development of MNs and NBUDs were high concentrations of Al, Zn, and Cu. In conclusion, chronic exposure to HMMs, especially Al, Cu, and Zn, in the studied population could be related to increased frequencies of NAs, such as NBUDs, KX, CC, and KL, in the buccal mucosa cells.