Comportement photochimique du nitro-4 phenol en solution aqueuse

The quantum yield of the phototransformation of 4-nitrophenol has been evaluated as 4.5×10⁻⁵±0.6×10⁻⁵ at pH=2; at 3.0×10⁻⁵±0.6×10⁻⁵ at pH=5.5; 1.8×10⁻⁵±0.5×10⁻⁵ at pH=8.3. However the half-life is relatively low and no accumulation of aromatic or quinonic products was observed. Hydroquinone (QH₂) is the main organic primary product formed when an air-saturated or degassed solution was irradiated in 365 nm monochromatic light (about 80% of the 4-nitrophenol initially converted at pH=5.5 in the absence of oxygen). In air-saturated neutral or acidic solution, the formation of NO⁻₃ ions accounted for about 80% of the 4-nitrophenol converted, but in degassed medium a mixture NO : NO⁻₂ : NO⁻₃ is formed. An heterolytical mechanism of photohydrolysis with primary formation of QH₂ and HNO₂ is suggested. Several by-products as benzoquinone, 4-nitrosophenol, 4-nitrocatechol and nitrohydroquinone are formed according to the conditions. Many secondary reactions are involved as the disproportionation or the oxidation of HNO₂, the oxidation of QH₂ by HNO₂ and oxidations induced by excitation of NO⁻₂ and NO⁻₃.     

Instream sensor results suggest soil–plant processes produce three distinct seasonal patterns of nitrate concentrations in the Ohio River Basin

The Ohio River Basin (ORB) is responsible for 35% of total nitrate loading to the Gulf of Mexico yet controls on nitrate timing require investigation. We used a set of submersible ultraviolet nitrate analyzers located at 13 stations across the ORB to examine nitrate loading and seasonality. Observed nitrate concentrations ranged from 0.3 to 2.8 mg L⁻¹ N in the Ohio River's mainstem. The Ohio River experiences a greater than fivefold increase in annual nitrate load from the upper basin to the river's junction with the Mississippi River (74–415 Gg year⁻¹). The nitrate load increase corresponds with the greater drainage area, a 50% increase in average annual nitrate concentration, and a shift in land cover across the drainage area from 5% cropland in the upper basin to 19% cropland at the Ohio River's junction with the Mississippi River. Time-series decomposition of nitrate concentration and nitrate load showed peaks centered in January and June for 85% of subbasin-year combinations and nitrate lows in summer and fall. Seasonal patterns of the terrestrial system, including winter dormancy, spring planting, and summer and fall growing-harvest seasons, are suggested to control nitrate timing in the Ohio River as opposed to controls by river discharge and internal cycling. The dormant season from December to March carries 51% of the ORB's nitrate load, and nitrate delivery is high across all subbasins analyzed, regardless of land cover. This season is characterized by soil nitrate leaching likely from mineralization of soil organic matter and release of legacy nitrogen. Nitrate experiences fast transit to the river owing to the ORB's mature karst geology in the south and tile drainage in the northwest. The planting season from April to June carries 26% of the ORB's nitrate and is a period of fertilizer delivery from upland corn and soybean agriculture to streams. The harvest season from July to November carries 22% of the ORB's nitrate and is a time of nitrate retention on the landscape. We discuss nutrient management in the ORB including fertilizer efficiency, cover crops, and nitrate retention using constructed measures.     

Does educated labor force is managing the green economy in BRCS? Fresh evidence from NARDL-PMG approach

Environmental Science and Pollution Research - It is observed that an educated labor force can increase the absorption capacity of the economy and improve the effectiveness of green technologies...