A comparison of dust impacts on polycrystalline and monocrystalline solar photovoltaic performance: an outdoor experimental study

Environmental Science and Pollution Research - Solar cells are considered one of the most important and widespread solar applications in the world. However, the performance of the PV modules is...     

The performance of an anaerobic sequencing batch biofilm reactor treating domestic sewage colonized by anoxygenic phototrophic bacteria

There are few reports on morphological characterization of microbial population colonizing anaerobic bioreactors and the aim of this work was to access such variable in an anaerobic sequencing batch biofilm reactor treating the University of Sao Paulo (Sao Carlos city, Brazil) domestic sewage. This pilot-scale reactor (1.2m3) has been treating 0.65 m3 of liquid waste under cycles of 8h. The ASBBR has the distinct characteristics of being filled with support material for biomass attachment with the aim of skipping the sedimentation phase during the operational cycles, as it is commonly observed in anaerobic sequencing batch reactors (ASBR). Physical, chemical and physico-chemical variables were accessed in the influent and in the effluent for performance evaluation. Microbial characterization was made by means of direct microscopy and samples were taken over 150 d with a 25 d period interval. The ASBBR attained approximately 60% of COD removal efficiency. Microscopic analysis of biomass showed the presence of anoxygenic phototrophic bacteria probably influencing the ASBBR performance in the domestic sewage treatment. It is very likely that the exclusion of phototrophic sulfur bacteria by efficiently restraining the light would enhance the bioreactor efficiency.     

Changed vegetation composition in coniferous forests near to motorways in Southern Germany: the effects of traffic-born pollution

To estimate the effect of traffic emissions on the vegetation composition of coniferous forests near to motorways, three transects of 520 m length were studied by analysing vegetation composition, soil parameters and deposition data in the Munich-area, Southern Germany. The detected patterns suggest that motorways have an impact on the vegetation composition in the neighbourhood of roads. Depending on the wind direction, the influences of the motorways reaches up to 230 m on downwind side and up to 80 m on upwind side. The vegetation is mainly affected by the deposition of nitrogen deriving from fuel combustion and by basic substances added to road salt. By monitoring vegetation changes near to motorways, it is possible to estimate the areas where harmful alterations of the ecosystem can be expected.     

Feasibility of Applying a Stable Isotopic Tracer for Direct Determination of Dry Particulate Deposition to Soybean Plants

ABSTRACT

A stable rare-earth isotopic tracer was used to measure the deposition of KNO₃ particles on soybean leaves by direct measurement of the tracer on the plant surfaces by thermal-ionization mass spectrometry. Submicrometer particles, made from a solution containing 3 |mg mL^-1 neodymium isotope (¹⁴⁸Nd, 87.9%) and 1,000 mg mL^-1 KNO₃, were dispersed with a two-fluid nozzle and released upwind of a soybean field. Total suspended- and size-fractionated-aerosol particles were collected on an open-face filter and in a micro-orifice impactor, respectively, at a distance of 40 m from the release point. Soybean leaves exposed to the plume were collected at distances ranging from 25 to 100 m. As little as 5.5 pg of the tracer (i.e., excess ¹⁴⁸Nd) was detected in soybean leaves at signal-to-noise ratios ranging from 7,500 to 240,000, in the presence of 200 to 2,700 pg of naturally occurring Nd. The dry-particle deposition velocity, determined from the ratio of the aerial concentration and directly deposited aerosol (geometric mass mean diameter, 0.20 mm) flux, and its corresponding analytical uncertainty were 0.30 cm sec^-1 and 2.5%, respectively.     

Uranium transport around the reactor zone at Bangombé and Okélobondo (Oklo): examples of hydrogeological and geochemical model integration and data evaluation

The sites at Bangombé and Okélobondo (Oklo) in Gabon provide a unique opportunity to study the behaviour of products from natural nuclear reactions in the vicinity of reactor zones which were active around two billion years ago. The Commission of the European Communities initiated the Oklo Natural Analogue Programme. One of the principal aims was to study indications of present time migration of elements from the reactor zones under ambient conditions. The hydrogeological and hydrochemical data from the Oklo sites were modelled in order to better understand the geochemical behaviour of radionuclides in the natural system, by using independent models and by comparing the modelling outcome. Two modelling approaches were used: M3 code (hydrochemical mixing and mass balance model), developed by the Swedish Nuclear Fuel and Waste Management Company (SKB) and HYTEC (reactive transport model) developed by Ecole des Mines de Paris. Two different reactor zones were studied: Bangombé, a shallow site, the reactor being at 11 m depth, and OK84 at Okélobondo, situated at about 450 m depth, more comparable with a real repository location. This allowed the validation of modelling tools in two different sedimentary environments: one shallow, with a more homogeneous layering situated in an area of meteoric alteration, and the other offering the opportunity to study radionuclide migration from the reaction zone over a distance of 450 m through very heterogeneous sedimentary layers. The modeling results indicate that the chemical reactions retarding radionuclide transport are very different at the two sites. At Bangombé, the decomposition of organic material consumes oxygen and at Okélobondo the oxygen is consumed by inorganic reactions resulting, in both cases, in uranium retardation. Both modelling approaches (statistic with M3 code and deterministic with HYTEC code) could describe this situation. The goal of this exercise is to test codes which can help to describe and understand the processes taking place at the sites, validate the models with in situ data, and thus build confidence in the tools used for future site characterization. Ultimately, this allows identifying and selecting processes and parameters that can be used as input into repository performance assessment calculations and modelling exercises.