Risk assessment of etofenprox (vectron) on non-target aquatic fauna compared with other pesticides used as Simulium larvicide in a tropical environment

Within the rotational scheme developed by the Programme to fight the resistance of Simulium damnosum to chemical larvicides, there was an operational gap at discharges between 5 and 70 m³ s⁻¹ for the treatment of rivers where resistance to organophosphates was present. The use of permethrin and carbosulfan was precluded because of risk of environmental impact and, Bacillus thuringiensis ser. H-14 treatments were not envisageable due to cost and logistics constraints. Among the possible complementary groups of larvicides tested, the pseudo-pyrethroids, held promise, because of a mode of action similar to that of pyrethroids, but along with a usually lower toxicity for fish. Etofenprox, one of the pseudo-pyrethroids tested, shows a global detachment of non-target insects in 24 h close to that of pyraclofos, an organo-phosphorus compound (27 against 23%). In laboratory conditions, six times the operational dose which is 0.03 mg l⁻¹ 10 min, is needed to cause 50% mortality of Caridina sp. (a small shrimps species) and 30 times this same dose for 95% mortality. For fish species, a safety margin of 400–800 times the operational dose is observed for Oreochromis niloticus and 200–400 times for Tilapia zillii.     

Kinetic analysis of constructed systems for the recovery of contaminated areas by acid mine drainage

INTRODUCTION: Flowing of the acid mine drainage may contaminate the adjacent water bodies causing substantial changes in the aquatic ecosystem. This aspect is the most relevant problem in the southern of Santa Catarina once the contaminated areas are inserted in the watershed of the Araranguá, Urussanga, and Tubar?o rivers, increasing the need for recovery studies. These areas are between Criciúma, I?ara, Urussanga, Siderópolis, Lauro Müller, Orleans, and Alfredo Wagner towns where a conservation unit exist called the Environmental Preservation Area of Baleia Franca. Aiming to compare the kinetics of the ash derived from burning coal and to neutralize acid mine drainage, different neutralizer, limestone, fly, and bottom ash, was mounted on a pilot scale experiment. DISCUSSION: The transport parameters showed the same order of infiltration and dispersion: fly ash < bottom ash < limestone. The order of measured alkalinity was: limestone < fly ash < bottom ash, with pH values of 9.34, 12.07, and 12.25, respectively. The limestone kinetics of acidic drainage neutralization was first order with reaction rate constant k?=?0.0963 min(-1), bottom ash was 3/4 with k?=?0.0723 mol(1/4) L(-1/4) min(-1), and the fly ash had higher order kinetics, 4/3, with reaction rate constant k?=?27.122 L(1/3) mol(-1/3) min(-1). However, by mathematical modeling, it was found that due to a combination of transport and kinetics, only limestone treatment reached a pH above 6 within 5 years, corresponding to the ideal as planned.     

Value of information analysis in remedial investigations

Site investigations of contaminated land are associated with high costs. From a societal perspective, just enough economic resources should be spent on investigations so that society's limited resources can be used optimally. The solution is to design investigation programs that are cost effective, which can be performed using value of information analysis (VOIA). The principle of VOIA is to compare the benefit at the present state of knowledge with the benefit that is expected after an investigation has been performed. A framework for VOIA of site investigations is presented based on Bayesian risk-cost-benefit decision analysis. The result is an estimate of the value of an investigation program and, for specific problems, the optimal number of samples. The main strength of the methodology is that it promotes clear thinking and compels the decision maker to reflect on issues that otherwise would be ignored. The main weakness is the complexity of VOIA models.     

Risk assessment of etofenprox (Vectron) on non-target aquatic fauna compared with other pesticides used as Simulium larvicide in a tropical environment

Within the rotational scheme developed by the Programme to fight the resistance of Simulium damnosum to chemical larvicides, there was an operational gap at discharges between 5 and 70 m³ s⁻¹ for the treatment of rivers where resistance to organophosphates was present. The use of permethrin and carbosulfan was precluded because of risk of environmental impact and, Bacillus thuringiensis ser. H-14 treatments were not envisageable due to cost and logistics constraints. Among the possible complementary groups of larvicides tested, the pseudo-pyrethroids, held promise, because of a mode of action similar to that of pyrethroids, but along with a usually lower toxicity for fish. Etofenprox, one of the pseudo-pyrethroids tested, shows a global detachment of non-target insects in 24 h close to that of pyraclofos, an organo-phosphorus compound (27 against 23%). In laboratory conditions, six times the operational dose which is 0.03 mg l⁻¹ 10 min, is needed to cause 50% mortality of Caridina sp. (a small shrimps species) and 30 times this same dose for 95% mortality. For fish species, a safety margin of 400–800 times the operational dose is observed for Oreochromis niloticus and 200–400 times for Tilapia zillii.     

GEOCHEMICAL INTERPRETATIONS OF GROUNDWATER FLOW SYSTEMS1

ABSTRACT. Interest in the geochemistry of groundwater is increasing owing to the great number of current projects involving underground liquid waste storage, artificial recharge of potable water, accidental contamination of groundwater bodies, sanitary landfills, and pollution monitoring. Geochemical techniques used to facilitate the understanding of a groundwater system range from extremely simple to those requiring sophisticated theories, equipment, and procedures. An interpretation of the simple trilinear diagram for samples collected from the Yucatan Peninsula of Mexico provided evidence that the fresh-water body was only a few tens of meters thick and was underlain everywhere by an extensive body of salt water. A geochemical technique that has been used effectively to identify the source of salt water in coastal aquifers is measurement of the carbon-14 concentrations. Carbon-14 has been used in a regional carbonate aquifer to determine the velocity of groundwater movement, rates of chemical reactions, and distribution of hydraulic conductivity. The application of principles of irreversible thermodynamics to groundwater systems provides a basis for constructing models which permit prediction, over both time and space, of changes in head distribution and chemical character of the water resulting from imposed stresses on the system. In essence, proper application of irreversible thermodynamics combines the potential theory of Hubbert with principles of reversible chemical thermodynamics, such as solution of carbonate minerals, to describe and explain controlling chemical reactions and processes of groundwater systems.     

Application of powdered activated carbon coating to fabrics in a hybrid filter to enhance mercury removal

Elemental mercury(Hg0) is predominant constituent of flue gas emitted from coal-fired power plants. Adsorption has been considered the best available technology for removal of Hg0 from flue gas. However, adsorbent injection increases the amount of ash generated. In the present study, powdered activated carbon(PAC) was coated on polytetrafluoroethylene/glass fiber filters to increase Hg0 removal while concurrently reducing the amount of ash generated. The optimal PAC coating rate was determined in laboratory experiments to ensure better Hg0 removal with low pressure drop. When PAC of particle size less than 45 μm was used, and the areal density was 50 g/m2, the pressure drop remained under 30 Pa while the Hg0 removal efficiency increased to 15.8% from4.3%. The Hg0 removal efficiency also increased with decrease in filtration velocity. The optimal PAC coating rate was applied on a hybrid filter(HF), which was combined with a bag filter and an electrostatic precipitator in a single chamber. Originally designed to remove fine particulates matter, it was retrofitted to the flue gas control device for simultaneous Hg0 removal. By employing the PAC coating, the Hg removal efficiency of the HF increased to 79.79% from 66.35%. Also, a temporary reduction in Hg removal was seen but this was resolved following a cleaning cycle in which the dust layer was removed.     

Inventory of twenty-six combustible wastes as sources of potentially toxic elements: B,Cr, Cu,Zn, As,Sb, Ba,and Pb

Journal of Material Cycles and Waste Management - Municipal solid waste (MSW) is converted to various materials through treatment processes, which in turn distributes potentially toxic elements...     

Nutrient Bioassays of Growth Parameters for Algae in the North Bosque River of Central Texas1

Abstract: Nutrient dose‐response bioassays were conducted using water from three sites along the North Bosque River. These bioassays provided support data for refinement of the Soil and Water Assessment Tool (SWAT) model used in the development of two phosphorus TMDLs for the North Bosque River. Test organisms were native phytoplanktonic algae and stock cultured Pseudokirchneriella subcapitata (Korshikov) Hindak. Growth was measured daily by in vivo fluorescence. Algal growth parameters for maximum growth (μ_max) and half‐saturation constants for nitrogen (K_N) or phosphorus (K_P) were determined by fitting maximum growth rates associated with each dose level to a Monod growth rate function. Growth parameters of native algae were compared between locations and to growth parameters of P. subcapitata and literature values. No significant differences in half‐saturation constants were indicated within nutrient treatment for site or algal type. Geometric mean K_N was 32 μg/l and for K_P 7 μg/l. A significant difference was detected in maximum growth rates between algae types but not between sites or nutrient treatments. Mean μ_max was 1.5/day for native algae and 1.2/day for stock algae. These results indicate that watershed‐specific maximum growth rates may need to be considered when modeling algal growth dynamics with regard to nutrients.