The formation mechanism of low leaching glassy slag during plasma arc vitrification treatment of fly ash

In this paper, the glass formation theory is applied to study the formation mechanism of the low leaching glassy slag during the process of plasma waste treatment. The research shows that SiO2 acts as network former to form a 3-dimensional Si-O tetrahedral network in which heavy metals are bonded or encapsulated, so the Si-O tetrahedron protect heavy metals against leaching from the vitrified slag or acid corrosion. For given chemical compositions of waste, the formation ability of the vitrified slag can be represented by the ratio of the whole oxygen ions to the whole network former ions in glass (O/Si) which is appropriate in the range of 2~3. A plasma arc reactor is used to conduct the vitrification experiments of two kinds of fly ashes with additives in which effects of various parameters including arc power, cooling speed, treatment temperature are studied. The chemical compositions of fly ashes are analyzed by X-ray fluorescence (XRF) spectrometry. The experimental results show that both cooling speed and O/Si have important influence on the formation of the vitrified slag, which is qualitatively in accordance with the predictions of the glass formation theory.

Exploitation of soil biota ecosystem services in agriculture: a bioeconomic approach

24 p.

Modelling the Effect of Climate Change on Environmental Pollution Losses from Dairy Systems in the UK

21 p.

A GIS-based model of soil erosion and transport

Soil erosion is a natural process that occurs when the force of wind, raindrops or running water on the soil surface exceeds the cohesive forces that bind the soil together. In general, vegetation cover protects the soil from the effects of these erosive forces. However, land management activities such as ploughing, burning or heavy grazing may disturb this protective layer, exposing the underlying soil. The decision making process in rural catchment management is often supported by the predictive modelling of soil erosion and sediment transport processes within the catchment, using established techniques such as the Universal Soil Loss Equation [USLE] and the Agricultural Nonpoint Source pollution model [AGNPS]. In this article, the authors examine the range of erosion models currently available and describe the application of one of these to the Burrishoole catchment on the north-west coast of Ireland, which has suffered heavy erosion of blanket peat in recent years.

Modelling soil erosion and transport in the Burrishoole catchment, Newport, Co. Mayo, Ireland

The Burrishoole catchment is situated in County Mayo, on the northwest coast of the Republic of Ireland. Much of the catchment is covered by blanket peat that, in many areas, has become heavily eroded in recent years. This is thought to be due, primarily, to the adverse effects of forestry and agricultural activities in the area. Such activities include ploughing, drainage, the planting and harvesting of trees, and sheep farming, all of which are potentially damaging to such a sensitive landscape if not managed carefully. This article examines the sediment yield and hydrology of the Burrishoole catchment. Flow and sediment concentrations were measured at 8-hourly intervals from 5 February 2001 to 8 November 2001 with an automatic sampler and separate flow gauge, and hourly averages were recorded between 4 July 2002 and 6 September 2002 using an automatic river monitoring system [ARMS]. The authors describe the GIS-based model of soil erosion and transport that was applied to the Burrishoole catchment during this study. The results of these analyses were compared, in a qualitative manner, with the aerial photography available for the Burrishoole catchment to see whether areas that were predicted to contribute large proportions of eroded material to the drainage network corresponded with areas where peat erosion could be identified through photo-interpretation.

Avaliação dos teores de resíduos do pesticida ditiocarbamato no solo de uma cultura de couve (Brassica Oleracea L.) utilizando cloridrato de L-cisteina para preservação das amostras

Os pesticidas etileno-bis-ditiocarbamatos da classe dos ditiocarbamatos estão entre os fungicidas mais empregados em todo o mundo para o controle de pragas. Muitos métodos para determinar ditiocarbamatos são baseados na hidrólise ácida em presença de cloreto estanoso e análise do CS2 gerado por diferentes técnicas. Nesse contexto, constituiram em objetivos do presente trabalho, como primeira etapa, o estudo de condições adequadas à estocagem de amostras de solo, e como segunda etapa, a avaliação das taxas de degradação e de lixiviação do fungicida mancozebe num cambissolo distrófico através do método espectrofotométrico. O sítio de estudo foi uma área delimitada de 36 m2, de uma cultura de couve, localizada em São Lourenço no 3 distrito do município de Nova Friburgo-RJ. As análises foram realizadas no laboratório de tecnologia ambiental (LABTAM/UERJ). Na primeira etapa, duas sub-amostras de solo contaminadas com mancozebe foram submetidas a tratamento com cloridrato de L-cisteina e estocadas às temperaturas ambiente e de -20C, sendo posteriormente analisadas em intervalos de 1, 7, 15 e 35 dias após a aplicação do fungicida. Outras duas sub-amostras não tratadas com cloridrato de L-cisteina foram submetidas às mesmas condições de temperatura e analisadas nos mesmos intervalos de tempo. Na segunda etapa, foi efetuada a aplicação do fungicida MANZATE 800 (Dupont Brasil, 80% mancozebe) na dose recomendada de 3,0 Kg ha-1 e coletadas amostras do solo nas profundidades de 0-10, 10-20 e 20-40 cm em intervalos de 2,5,8,12,15,18 e 35 dias após aplicação. As amostras de cada profundidade foram tratadas com cloridrato de L-cisteina e acondicionadas sob temperatura de -20C. Através dos resultados obtidos na primeira etapa, pôde-se concluir que o tratamento com cisteina foi eficaz para conservação do analito, tanto para a amostra mantida a -20C quanto para a amostra mantida à temperatura ambiente. Os dados obtidos na segunda etapa do estudo mostraram que mancozebe apresentou comportamento semelhante ao descrito na literatura, para persistência no solo. Os resultados de lixiviação mostraram que nas condições pelas quais foi conduzido o experimento, resíduos de mancozebe foram detectados em profundidades de até 40 cm, porém através dos modelos de potencial de lixiviação, concluiu-se que o fungicida não oferece risco de contaminação de águas subterrâneas