Is PCBs concentration variability between and within freshwater fish species explained by their contamination pathways?

Many chemical, physiological, and trophic factors are known to affect bioaccumulation of polychlorinated biphenyls (PCBs) in biota. Understanding the primary factors affecting fish contamination is critical for predicting and assessing risks to upper-trophic level consumers, including humans. Here we identify PCB contamination pathways that could explain within- and between-species variability in fish concentration levels. Three freshwater river fish species (barbel, chub and bream) were sampled at three sites along the Rhone River (France) where fish consumption is partially prohibited because of PCB levels exceeding the European health-based benchmark. The trophic position was assessed using an innovative approach based on stable isotope analyses and Bayesian inference, which takes into account both isotope data variability and parameter uncertainty. The effect of foraging habitat on fish contamination was addressed using stable isotope mixing models. The fish trophic position and PCB concentrations were found to be unrelated while the exploitation of sediment detrital carbon as a food source appeared to be a critical factor affecting fish contamination. Fish length, PCB concentration of the sediment, and individual fish foraging habitat (exploitation of detrital versus planktonic carbon sources) explained 80% of within- and between-species variability observed in PCB concentrations. These results, obtained for species that have overlapping TPs and exploit different carbon sources, reveal that the important factor in fish PCB contamination is not only what fish consume, but also and essentially the feeding location.     

The variability of polychlorinated biphenyls levels in urban soils from five European cities

The concentration of PCBs in topsoils from five European cities was assessed and the highest levels were found in Glasgow (Scotland), followed by Torino (Italy), Aveiro (Portugal), Ljubljana (Slovenia) and Uppsala (Sweden). All cities showed the presence of local sources in addition to diffuse contamination from global atmospheric transport. The association of general soil parameters with PCBs in Glasgow and with heavier congeners in Torino and Ljubljana indicates that retention of these compounds is occurring. The profiles obtained resemble Aroclor 1254 and 1260, which are important local sources. Nevertheless, differences in PCB profiles were observed among cities, due to the combined effects of the age of the contamination (which determines the time available for volatilisation and degradation), different sources of PCBs and differences in climate (which influence volatilisation and deposition).     

Inventory of heavy metal content in organic waste applied as fertilizer in agriculture: evaluating the risk of transfer into the food chain

Background, aim, and scope  

In this work, an environmental risk assessment of reusing organic waste of differing origins and raw materials as agricultural fertilizers was carried out. An inventory of the heavy metal content in different organic wastes (i.e., compost, sludge, or manure) from more than 80 studies at different locations worldwide is presented.     

Integrating Modeling and Field Experiments to Evaluate Impacts of Vegetative Practices on Ponderosa Pine Watersheds1

Abstract: Determining watershed response to vegetation treatment has been the subject of numerous hydrologic studies over the years. However, generalizing the information obtained from traditional paired‐watershed studies to other watersheds in a region is problematic because of the empirical nature of such studies and the context dependence of hydrologic responses. This paper addresses the issue of generalizing hydrologic information through integration of process‐based modeling and field observations from small‐scale watershed experiments. To this end, the results from application of a process‐based model were compared with the results from small‐scale watershed experiments in ponderosa pine forests of Arizona. The model simulated treatment impacts reasonably well when compared to the traditional paired‐watershed approach. However, the model tended to overestimate water yields during periods of low flow, and there was a significant difference between the two approaches in the estimation of treatment impacts during the first four years following treatment. The results indicate that the lumped‐parameter modeling approach used here may be limited in its ability to detect small changes, and tends to overestimate changes that occur immediately following treatment. It is concluded that watershed experiments can be highly informative due to their direct examination of cause‐effect relationships, while process‐based models are useful for their processing power and focus on functional relationships. The integrated use of both watershed experiments and process‐based models provides a way to generalize hydrologic information, illuminate the processes behind landscape treatment effects, and to generate and test hypotheses.     

Degradation of tetracycline at a boron-doped diamond anode: influence of initial pH,applied current intensity and electrolyte

The anodic oxidation of tetracycline was performed in an up-flow reactor, operating in batch mode with recirculation, using as anode a boron-doped diamond electrode. The influence on the degradation rate of solution initial pH (2 to 12), applied current intensity (25 to 300 A m^?2) and type of electrolyte (sodium sulphate or sodium chloride) were investigated. For the assays run at equal current density, with sodium sulphate as electrolyte, the solution’s initial pH of 2 presented the highest absorbance and chemical oxygen demand removals. Regarding the influence of current density, for equal charge passed, the organic load removal rate decreased with the increase in applied current. When sodium sulphate was used as an electrolyte, high-performance liquid chromatography (HPLC) results have shown an almost complete removal of tetracycline after a 2-h assay. HPLC results have also shown the presence of oxamic acid as one of the intermediates of tetracycline anodic oxidation. The complete removal of tetracycline was much faster in the presence of chloride ions that promoted the complete degradation of this antibiotic in 30 min. However, in the presence of chloride ions, the tetracycline mineralization is slower, as observed by the lower organic carbon removal rate when compared to that of the tetracycline degradation in the presence of sulphate.     

Impacts of water resources development on flow regimes in the Brazos River

The Brazos River, the second largest basin in Texas, represents one of the most highly developed river systems in the state. Thirty-nine reservoirs with capacities greater than 5,000 acre-feet are currently in operation in the basin. Impacts on stream ecosystems are evidenced by changes in flow regimes and resulting changes in fish assemblages over the past 50 years. These changes have been widely attributed to human impacts, through the construction of dams, diversion of water supplies for agricultural and municipal uses, and land use change. However, streamflow regimes result from a complex mix of drivers that include climate, topography, land cover, land use practices, reservoir management practices, dam releases, and water consumption patterns, making determination of anthropogenic impacts problematic. This study quantifies changes in flow regime and probable historical drivers including precipitation, dam construction, population growth, and changing water demand in the Brazos River basin over the past 100 years. Results indicate that the climate of the basin has been relatively stable over the study period, while large-scale changes in human population densities and intense water resources development are correlated with impacts on flow regimes, decreasing the frequency and magnitude of high flow events and stabilizing low flows. These changes have resulted in an increase of habitat generalist fish species, a decrease of native obligate riverine fishes, and an overall homogenization of species assemblages. The results of this study indicate the importance of combining ecological data with an assessment of social drivers for a greater understanding of the dynamics of river basin systems.     

Evaluation of optimal conditions for determination of low selenium content in shellfish samples collected at Todos os Santos Bay,Bahia, Brazil using HG-AFS

This work proposes a procedure for the determination of total selenium content in shellfish after digestion of samples in block using cold finger system and detection using atomic fluorescent spectrometry coupled hydride generation (HG AFS). The optimal conditions for HG such as effect and volume of prereduction KBr 10 % (m/v) (1.0 and 2.0 ml) and concentration of hydrochloric acid (3.0 and 6.0 mol L^?1) were evaluated. The best results were obtained using 3 mL of HCl (6 mol L^?1) and 1 mL of KBr 10 % (m/v), followed by 30 min of prereduction for the volume of 1 mL of the digested sample. The precision and accuracy were assessed by the analysis of the Certified Reference Material NIST 1566b. Under the optimized conditions, the detection and quantification limits were 6.06 and 21.21 μg kg^?1, respectively. The developed method was applied to samples of shellfish (oysters, clams, and mussels) collected at Todos os Santos Bay, Bahia, Brazil. Selenium concentrations ranged from 0.23?±?0.02 to 3.70?±?0.27 mg kg^?1 for Mytella guyanensis and Anomalocardia brasiliana, respectively. The developed method proved to be accurate, precise, cheap, fast, and could be used for monitoring Se in shellfish samples.     

Assessment of indoor airborne contamination in a wastewater treatment plant

The main objective of this work was to quantify and characterize the major indoor air contaminants present in different stages of a municipal WWTP, including microorganisms (bacteria and fungi), carbon dioxide, carbon monoxide, hydrogen sulfide ammonia, formaldehyde, and volatile organic compounds (VOCs). In general, the total bacteria concentration was found to vary from 60 to >52,560 colony-forming units (CFU)/m³, and the total fungi concentration ranged from 369 to 14,068 CFU/m³. Generally, Gram-positive bacteria were observed in higher number than Gram-negative bacteria. CO₂ concentration ranged from 251 to 9,710 ppm, and CO concentration was either not detected or presented a level of 1 ppm. H₂S concentration ranged from 0.1 to 6.0 ppm. NH₃ concentration was <2 ppm in most samples. Formaldehyde was <0.01 ppm at all sampling sites. The total VOC concentration ranged from 36 to 1,724 μg/m³. Among the VOCs, toluene presented the highest concentration. Results point to indoor/outdoor ratios higher than one. In general, the highest levels of airborne contaminants were detected at the primary treatment (SEDIPAC 3D), secondary sedimentation, and sludge dehydration. At most sampling sites, the concentrations of airborne contaminants were below the occupational exposure limits (OELs) for all the campaigns. However, a few contaminants were above OELs in some sampling sites.