The Environmental Protection Agency (EPA) provides access to information on a variety of topics related to the environment and strives to inform citizens of health risks. The EPA also has an extensive library network that consists of 26 libraries throughout the United States, which provide access to a plethora of information to EPA employees, scientists, and researchers. The EPA implemented a reorganization project to digitize their materials so they would be more accessible to a wider range of users, but this plan was drastically accelerated when the EPA was threatened with a budget cut. It chose to close and reduce the hours and services of some of their libraries. As a result, the agency was accused of denying users the “right to know” by making information unavailable, not providing an adequate strategic plan, and discarding vital materials. This case study explores the background of the digitization project, the practices implemented, and the critiques of the project.

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The Environmental Protection Agency

An overview on the advanced oxidation processes applied for the treatment of water pollutants defined in the recently launched Directive 2013/39/EU.

As an alternative to the gold standard TiO2 photocatalyst, the use of zinc oxide (ZnO) as a robust candidate for wastewater treatment is widespread due to its similarity in charge carrier dynamics upon bandgap excitation and the generation of reactive oxygen species in aqueous suspensions with TiO2. However, the large bandgap of ZnO, the massive charge carrier recombination, and the photoinduced corrosion–dissolution at extreme pH conditions, together with the formation of inert Zn(OH)2 during photocatalytic reactions act as barriers for its extensive applicability. To this end, research has been intensified to improve the performance of ZnO by tailoring its surface-bulk structure and by altering its photogenerated charge transfer pathways with an intention to inhibit the surface-bulk charge carrier recombination. For the first time, the several strategies, such as tailoring the intrinsic defects, surface modification with organic compounds, doping with foreign ions, noble metal deposition, heterostructuring with other semiconductors and modification with carbon nanostructures, which have been successfully employed to improve the photoactivity and stability of ZnO are critically reviewed. Such modifications enhance the charge separation and facilitate the generation of reactive oxygenated free radicals, and also the interaction with the pollutant molecules. The synthetic route to obtain hierarchical nanostructured morphologies and study their impact on the photocatalytic performance is explained by considering the morphological influence and the defect-rich chemistry of ZnO. Finally, the crystal facet engineering of polar and non-polar facets and their relevance in photocatalysis is outlined. It is with this intention that the present review directs the further design, tailoring and tuning of the physico-chemical and optoelectronic properties of ZnO for better applications, ranging from photocatalysis to photovoltaics.

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Zinc oxide based photocatalysis: tailoring surface-bulk structure and related interfacial charge carrier dynamics for better environmental applications

https://research.aalto.fi/files/41268358/1_s2.0_S0959652620307411_main.pdf

A critical review on application of photocatalysis for toxicity reduction of real wastewaters

Photocatalysis is an ecofriendly technique that emerged as a promising alternative for the degradation of many organic pollutants. The weaknesses of the present photocatalytic system which limit their industrial applications include low-usage of visible light, fast charge recombination, and low migration ability of the photo-generated electrons and holes. Therefore, various elements such as noble metals and transition metals as well as non-metals and metalloids (i.e., graphene, carbon nanotube, and carbon quantum dots) are doped into the photocatalyst as co-catalysts to enhance the photodegradation performance. The incorporation of the co-catalyst which alters the photocatalytic mechanism was discussed in detail. The application of photocatalysts in treating persistent organic pollutants such as pesticide, pharmaceutical compounds, oil and grease and textile in real wastewater was also discussed. Besides, a few photocatalytic reactors in pilot scale had been designed for the effort of commercializing the system. In addition, hybrid photocatalytic system integrating with membrane filtration together with their membrane fabrication methods had also been reviewed. This review outlined various types of heterogeneous photocatalysts, mechanism, synthesis methods of biomass supported photocatalyst, photocatalytic degradation of organic substances in real wastewater, and photocatalytic reactor designs and their operating parameters as well as the latest development of photocatalyst incorporated membrane.

An overview of photocatalytic degradation: photocatalysts, mechanisms, and development of photocatalytic membrane

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants of special concern because they are carcinogenic and mutagenic compounds. In this paper, photodegradation of a mixture of six PAHs in groundwater at pilot plant scale is reported. Semiconductor materials (ZnO and TiO 2 ) as photocatalysts in tandem with Na 2 S 2 O 8 as oxidant under natural sunlight were used. The PAHs were benzo[ a ]pyrene, benzo[ b ]fluoranthene, benzo[ ghi ]perylene, benzo[ k ]fluoranthene, fluoranthene, and indene[1,2,3- cd ]pyrene. As expected, the influence of both semiconductors on the degradation of PAHs was very significant in all cases. Photocatalytic experiments show that the addition of photocatalyst, especially for ZnO/Na 2 S 2 O 8 system, strongly improves the elimination of PAHs in comparison with photolytic tests; significantly increasing the reaction rates. The first-order equation (monophasic model) satisfactorily explained the disappearance process although it ignores small residues remaining late in the process. These residues are important from an environmental point of view and the Hoerl function (biphasic model) better predict the results obtained. In our conditions, the time required for 90% degradation was in the range 7–15 min and 18–76 min for ZnO and TiO 2 systems, respectively. Thus, the use of the tandem ZnO/Na 2 S 2 O 8 makes possible the economical decontamination of groundwater containing non-biodegradable pollutants like PAHs.

Removal of polycyclic aromatic hydrocarbons (PAHs) from groundwater by heterogeneous photocatalysis under natural sunlight

Adsorption, degradation, and movement are the key processes conditioning the behavior and fate of pesticides in the soil. Six processes that can move pesticides are leaching, diffusion, volatilization, erosion and run-off, assimilation by microorganisms, and plant uptake. Leaching is the vertical downward displacement of pesticides through the soil profile and the unsaturated zone, and finally to groundwater, which is vulnerable to pollution. Pesticides are frequently leached through the soil by the effect of rain or irrigation water. Pesticide leaching is highest for weakly sorbing and/or persistent compounds, climates with high precipitation and low temperatures, and soils with low organic matter and sandy texture. On the contrary, for pesticides with a low persistence that disappear quickly, the risk of groundwater pollution considerably decreases. Different and varied factors such as physicalchemical properties of the pesticide, a permeability of the soil, texture and organic matter content of the soil, volatilization, crop-root uptake, and method and dose of pesticide application are responsible for the leaching rate of the pesticides. Soils that are high in clays and organic matter will slow the movement of water, attach easily to many pesticides, and generally have a higher diversity and population of soil organisms that can metabolize the pesticides.

Environmental Risk of Groundwater Pollution by Pesticide Leaching through the Soil Profile

Assessment of agro-industrial and composted organic wastes for reducing the potential leaching of triazine herbicide residues through the soil.

Reclamation of agro-wastewater polluted with pesticide residues using sunlight activated persulfate for agricultural reuse.

Photocatalytic transformation of sixteen substituted phenylurea herbicides in aqueous semiconductor suspensions: intermediates and degradation pathways.

Gabriel Pérez-Lucas

Papers

Removal of polycyclic aromatic hydrocarbons (PAHs) from groundwater by heterogeneous photocatalysis under natural sunlight

Environmental Risk of Groundwater Pollution by Pesticide Leaching through the Soil Profile

Assessment of agro-industrial and composted organic wastes for reducing the potential leaching of triazine herbicide residues through the soil.

Reclamation of agro-wastewater polluted with pesticide residues using sunlight activated persulfate for agricultural reuse.

Photocatalytic transformation of sixteen substituted phenylurea herbicides in aqueous semiconductor suspensions: intermediates and degradation pathways.