Simulação do transporte de partículas em suspensão e de poluentes dissolvidos pelo escoamento em superfícies impermeáveis: uma contribuição ao saneamento urbano / Simulation of the transport of suspended particles and dissolved pollutants by runoff on impervious surfaces: a contribution to urban sanitation

RESUMO Um dos impactos da urbanização no meio ambiente é a alteração do processo de transformação da chuva em escoamento superficial, levando à alteração da qualidade dos recursos hídricos. Com este trabalho, objetivou-se simular o transporte de partículas em suspensão e de poluentes dissolvidos, transportados pelo escoamento, sobre uma superfície impermeável em escala de laboratório. O modelo experimental consistiu de um simulador para a aplicação de chuva artificial sobre uma superfície acrílica impermeável com 8,40 m2, na qual foram definidas quatro posições para a distribuição do cloreto de sódio e da areia fina, simulando fontes difusas de poluição. Os resultados indicaram diferenças entre os tempos de pico do transporte de poluentes dissolvidos e em suspensão, em função da posição desses. O efeito de first flush foi verificado para os poluentes dissolvidos independentemente da posição da fonte, enquanto para os poluentes transportados em suspensão o mesmo efeito só foi verificado quando a fonte estava mais próxima da saída da superfície impermeável.

ABSTRACT One of the impacts of urbanization on the environment is the changes in the rainfall-runoff process, causing changes in water resources quality. The objective of this project was to simulate the transport of suspended particles and pollutants dissolved on runoff, an impermeable surface at laboratory scale. The experimental model consisted on a simulator for the application of artificial rainfall on an impermeable surface with 8,40 m2, in which sodium chloride and fine sand were distributed in four defined regions, simulating sources of diffuse pollution. The results showed differences between peak transport times of dissolved and suspended pollutants, depending on their position. The first-flush effect was observed for the dissolved pollutants independently of the source position, whereas for the pollutants transported in suspension the same effect was only found when the source was closer to the outlet of the impervious surface.

Comparison of the distribation of doses calculated with Monte Carlo N-particle transport code and those practically measured by 60Co therapy facility / 中华放射医学与防护杂志

Objective To discuss the feasibility of Monte Carlo N-particle transport code(MCNP)simulated calculation.Methods The calculation in water phantom was contrasted with the practical measurements and the reported values using the percent depth dose(PDD)curve and normal peak scatter factor.Results There Was no significant difference between calculated and measured results in the 10 cm×10 cm field(t＝-0.41,P>0.05),however,there were significant differences in the 5 cm×5 cm field(t=7.2,P<0.05)and in the 12 cm×12 cm field(t=-4.6,P<0.05).There was no significant difierence between the calculated results and the reported values(t=-1.91,P>0.05).In the same radiation field,the PDD decreased as the depth increased,but increased as the size of the radiation field increased at the same depth.PDD and normal peak scatter factor were both important parameters for calculation of prescribed dose.Conclusions It is possible to establish a set of accurate and comprehensive percent depth doses and normal peak scatter factor parameters so as to provide the basis of clinical use, quality assurance and quality control for radiotherapy.