Torres Bojorges A.X.,Laboratorio Of Calidad Ambiental |
Hernandez Razo N.A.,Laboratorio Of Calidad Ambiental |
Fausto Urquieta A.A.,Laboratorio Of Calidad Ambiental |
Zurita Martinez F.,Laboratorio Of Calidad Ambiental
Revista Internacional de Contaminacion Ambiental | Year: 2017
In this two-year study, three hybrid constructed wetlands were evaluated and compared for Total-N removal, quantifying the content of each of the nitrogen compounds: Ammonium (NH4 +), nitrate (NO3 –) and organic nitrogen (Org-N). The first system (I) consisted of a subsurface flow horizontal wetland (SSFHW) followed by an aerobic stabilization pond (SP); the second one (II) consisted of a SSFHW followed by a subsurface flow vertical wetland (SSFVW); and the third one (III) was configured with a SSFVW followed by a SSFHW. The three systems were very effective for nitrification, reaching a high increase in nitrate concentrations in the effluents and high efficiencies in the N-NH4 + removal. These efficiencies were 76.2% and 78.7%, in the system I; 87.4% and 92.5% in the system II and 82.6% and 97.2% in the system III, during the first and the second year, respectively. With regard to the removal of Total-N, the system I (SSFHW-SP) was the most effective (p <0.05) with removal of 59.4% and 57.7% in the first and the second year, respectively. In the systems II (SSFHW-SSFVW) and III (SSFVW-SSFHW), the removals were 21.2% and 34.4%, and 25.0% and 36.3%, respectively for the first and the second year. The low removal of Total-N in the systems II and III, apparently were due to a low rate of denitrification because of the absence of a larger anoxic/anaerobic area; as a result of the shallow depth of the SSFHWs and the characteristics of the filter medium such as its grain size distribution (ground tezontle) and high porosity. © 2017, Centro de Ciencias de la Atmosfera, UNAM. All rights reserved.
Levy W.,Helmholtz Center for Environmental Research |
Brena B.M.,University of the Republic of Uruguay |
Brena B.M.,Laboratorio Of Calidad Ambiental |
Henkelmann B.,Helmholtz Center for Environmental Research |
And 5 more authors.
Toxicology in Vitro | Year: 2014
Polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) are persistent, toxic, and bioaccumulate in the environment. Due to their high analytical costs, these compounds are hardly regulated and mostly not monitored in the Third World. To overcome this, bioassays have been proposed as low-cost alternative methods. Two of the most established bioanalytical tools, the dioxin antibody-based enzyme-linked immunosorbent assay ELISA and the micro-EROD bioassay are evaluated and compared to high resolution gas chromatography and high resolution mass spectrometry (HRGC/HRMS) analytical methodology. The methods were tested using thirteen soils and sediment samples selected from diverse sites in Montevideo, Uruguay. The WHO2005 total toxic equivalent (WHO2005-TEQ) of soils ranged from 2.4 to 2212 (ng WHO2005-TEQ/kg dry sample) and from 0.14 to 9.4 (ng WHO2005-TEQ/kg dry sample) in sediments. This study shows significant contamination related to dioxin-like compounds, particularly in sites where uncontrolled burnings were carried out. ELISA and micro-EROD bioassay correlated well with HRGC/HRMS, R Spearman 0.773 and 0.913, respectively and were highly correlated to each other, R Spearman 0.879. Preliminary threshold values of bioassay toxic equivalents of 330 (ng/kg dry sample) for the micro-EROD bioassay and 220 (ng/kg dry sample) for ELISA are proposed. © 2014 Elsevier Ltd.