Degradation of bisphenol A by the UV/H2O2 process: a kinetic study

A theoretical and experimental study of bisphenol A (BPA) degradation by the UV/H₂O₂ process in water is presented. The effects of the H₂O₂ concentration and the specific rate of photon emission (E_P,0) on BPA degradation were investigated. A kinetic model derived from a reaction sequence was employed to predict BPA and hydrogen peroxide concentrations over time using an annular photochemical reactor in batch recirculation mode. The local volumetric rate of photon absorption (LVRPA) inside the photoreactor was computed using a Line Source with Parallel Plane emission model (LSPP). From the proposed kinetic model and the experimental data, the second order rate constants of the reactions between hydroxyl radicals and the main reacting species (H₂O₂ and BPA) were estimated applying a nonlinear regression method. A good agreement between the kinetic model and experimental data, for a wide range of operating conditions, was obtained. For BPA, H₂O₂, and TOC concentrations, the calculated root means square errors (RMSE) were 2.3?×?10^??2, 9.8?×?10^??1, and 9.0?×?10^??2 mmol L^??1, respectively. The simplified kinetic model presented in this work can be directly applied to scaling-up and reactor design, since the estimated kinetic constants are independent of the reactor size, shape, and configuration. Further experiments were made by employing low BPA initial concentration (100 μg L^??1) in water and real wastewater. A lower degradation rate of BPA was observed in the real wastewater, although the UV/H₂O₂ process has also been able to completely degrade the target pollutant in less than 1 h.

     

Impacts of market economy access and livelihood conditions on agro-food transition in rural communities in three macro-regions of Brazil

Environment, Development and Sustainability - Urbanization has threatened rural communities’ livelihoods worldwide, changing their agro-food systems from locally produced traditional items to...     

Organochlorine pesticides and polychlorinated biphenyls in soil and water samples in the Northeastern part of São Paulo State, Brazil

Detailed analyses of persistent organic pollutants (POPs) such as organochlorine pesticides (OCPs), hexachlorocyclohexane (HCH) isomers (HCHs), dichlorodiphenyltrichloro ethane (DDT) and its metabolites (DDTs) and congeners of polychlorinated biphenyls (PCBs) in soil and surface water from the northeastern São Paulo, Brazil allowed the evaluation of the contamination status, distribution and possible pollution sources. The pesticides and PCBs demonstrated markedly different distributions, reflecting different agricultural, domestic and industrial usage in each region studied. The ranges of HCH, DDT, and PCBs concentrations in the soil samples were 0.05–0.92, 0.12–11.01, 0.02–0.25 ng g⁻¹ dry wt, respectively, and in the surface water samples were 0.02–0.6, 0.02–0.58 and 0.02–0.5 ng l⁻¹, respectively. Overall elevated levels of DDT and PCB were recorded in region 2, a site very close to melting, automotive batteries industries, and agricultural practice regions. High ratios of metabolites of DDT to DDT isomers revealed the recent use of DDT in this environment. The sources of contamination are closely related to human activities, such as domestic and industrial discharge, street runoff, agricultural pesticides and soil erosion, due to deforestation as well as atmospheric transport.     

The complexation of Cu(II) by anthropogenic fulvic acids extracted from composted urban and livestock wastes

Abstract

The fulvic acid (fua) fractions of two samples of composted solid wastes [urban (urfua) and livestock (lsfua) wastes], commercialized to be used in agriculture as organic correctives or fertilizers, were analyzed for their affinity towards Cu(II) at pH=6. Molecular fluorescence spectroscopy (synchronous mode) was used to monitor the quenching caused by the complexation upon addition of Cu(II) to fua. Spectral data were preprocessed by a chemometric self‐modeling mixture analysis method (SIMPLISMA) to detect the number of different types of fluorescent binding sites that exist in each fua, their spectra and the corresponding quenching profiles [fluorescence intensity as function of the total Cu(II) concentration]. From the analysis of the quenching profiles, the amount of binding sites (Cl) and the corresponding conditional stability constants (K') were calculated. Both fua samples have approximately Cl = 0.21 mmol/g and the logarithms of K’ are 4.21(3) and 4.51(8), respectively for urfua and lsfua. The differences detected between these fua samples and those extracted from natural soils can be attributed mainly to the relatively small humification extent of the present anthropogenic fua samples.     

An innovative statistical approach for analysing non-continuous variables in environmental monitoring: assessing temporal trends of TBT pollution

The current work presents an innovative statistical approach to model ordinal variables in environmental monitoring studies. An ordinal variable has values that can only be compared as "less", "equal" or "greater" and it is not possible to have information about the size of the difference between two particular values. The example of ordinal variable under this study is the vas deferens sequence (VDS) used in imposex (superimposition of male sexual characters onto prosobranch females) field assessment programmes for monitoring tributyltin (TBT) pollution. The statistical methodology presented here is the ordered logit regression model. It assumes that the VDS is an ordinal variable whose values match up a process of imposex development that can be considered continuous in both biological and statistical senses and can be described by a latent non-observable continuous variable. This model was applied to the case study of Nucella lapillus imposex monitoring surveys conducted in the Portuguese coast between 2003 and 2008 to evaluate the temporal evolution of TBT pollution in this country. In order to produce more reliable conclusions, the proposed model includes covariates that may influence the imposex response besides TBT (e.g. the shell size). The model also provides an analysis of the environmental risk associated to TBT pollution by estimating the probability of the occurrence of females with VDS ≥ 2 in each year, according to OSPAR criteria. We consider that the proposed application of this statistical methodology has a great potential in environmental monitoring whenever there is the need to model variables that can only be assessed through an ordinal scale of values.     

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.     

Shifts of the feeding niche along the size dimension of three juvenile fish species in a tidal mudflat in southeastern Brazil

The diet of three cooccurring abundant fish species (Eucinostomus argenteus, Diapterus rhombeus and Micropogonias furnieri) and its ontogenetic changes in a mudflat area of a tropical bay in southeastern Brazil were described. The working hypothesis is that these three species shift the use of the available resources throughout their growth. Early juveniles of D. rhombeus and M. furnieri fed mainly on Cyclopoida copepods, shifting to Nematoda (D. rhombeus) and errant Polychaeta (M. furnieri) as they increased in size. In contrast, the early life stages of E. argenteus fed mainly on errant Polychaeta and Calanoida copepods, with increasing niche breadth as they grew. The relative degree of individual specialisation in resource use indicated specialism for M. furnieri and E. argenteus, and generalism for D. rhombeus. The largest intraspecific overlap was found for the smallest size classes. Niche breadth increased during ontogeny, with a higher average niche breadth at lower prey length/predator length ratios. Therefore, species-specific differences in diet across the resource gradient and increased niche breadth during ontogeny characterised the shifts of resource use, and probably account for the coexistence of these species in zones of sympatry in mudflat areas of southeastern Brazil.