THE PREDICTION OF TOXIC FUGITIVE DUST DISPERSION DURING SOIL REMEDIATION WORKS USING FDM MODEL

Transcription

1 THE PREDICTION OF TOXIC FUGITIVE DUST DISPERSION DURING SOIL REMEDIATION WORKS USING FDM MODEL I.PANAGOPOULOS *, A.KARAYANNIS *, P. KASSOMENOS **, G.GOUVALIAS *, AND E.GAKI * * Sybilla ltd, Ispilantou 16, Maroussi , Athens, Greece ** Dept of Physics, University of Ioannina, GR-45110, Ioannina, Greece. SUMMARY : This work is part of a Risk assessment Study of an Acid Sulphate Soil Remediation project in Greece and presents a methodology of assessing the risk associated with the dispersion of airborne particles (fugitive dust) containing S, As, Cd, Pb and Ni during construction works using dispersion model techniques. A mathematical model, using the USA/EPA/FDM Dispersion Mode, is used to predict the dispersion of fugitive dust, during the excavation and material handling activities in a soil remediation construction area. Particle Emissions, as well as the effect of the geometrical details of the area structure were studied. This methodology applied provides qualitative and quantitative data in order to assess the environmental impacts of soil remediation works and ensure the prevention of adverse environmental impacts and the protection of human health. The mathematical model analysis employed provided the basis in achieving good practice environmental management in the confrontation of fugitive dust dispersion during Soil Remediation Projects. It can also assist decision-making and provide greater certainty to the construction firms and the community in carrying out planning for Soil Remediation activities. 1. INTRODUCTION Fugitive dust emissions in soil remediation projects can occur from land clearing, excavation, hauling, dumping, spreading, grading, compaction, wind erosion, and traffic over unpaved areas. Actual quantities of emissions depend on the extent and nature of the land clearing operations, the prevailing meteorological conditions, excavation and haulage activities, the type of equipment employed, the physical characteristics of the contaminated soils and the underlying soils formations, the speed at which construction vehicles are operated, and the type of fugitive dust control methods employed. Much of the fugitive dust generated by construction activities consists of relatively large-size particles, which are expected to settle within a short distance from the construction site and to not significantly impact nearby buildings or people. All appropriate fugitive dust control measures including watering of exposed areas and dust covers for trucks would be employed during construction of the projected development sites.

2 When trying to assess the impact of dust emissions associated with material handling and excavation during the implementation of soil remediation projects, the following issues need to be taken into account: Determination of effective preventive dust control measures (fences etc). Dispersion of dust and particulates in complex geometrical terrains. Location and sizing of fences used to eliminate dispersion of dust and particulates.(where, how many, how large, orientation, etc.). Environmental properties and fugitive dust and particulates. Meteorological Conditions. The aim of the design of a soil reclamation project to carry on construction works effectively, economically and to minimize the effect of pollution. On the other hand, usually, the goal of the contractor is to complete the construction project as quickly as possible and re-establish protective cover, either vegetation or pavement. In one way, this goal is compatible with fugitive dust control: the shorter the period of exposure, the less is the risk for wind and water erosion to occur. The issues associated with airborne particles (fugitive dust) containing S, As, Cd, Pb and Ni during Construction works in Soil Remediation project are complex and deserve special attention [Panagopoulos and Malliaros, 2005] since the fugitive dust given its composition may be characterized as dangerous to the natural and manmade environment. A model, based on USA/EPA/FDM mode, was developed for the estimation of dispersion of dust and particulate emissions associated with material handling and excavation during the implementation of soil remediation projects as a measure to eliminate dispersion of air pollutants was developed by SYBILLA Ltd. with close co-operation with engineering firms J.Panagopoulos-C.Malliaros in the framework of a reclamation study project [Panagopoulos and Malliaros, 2005] assigned by Prefecture of Athens. 2. THE PHYSICAL PROBLEM The physical set-up considered in this study is Thoriko Bay in Lavrion, an area of m 2, which is located S-E of Athens. Uncontrolled disposing of mining and metallurgical wastes during historical mining activities in the area resulted in the contamination of the site. Comprehensive research project conducted in the area as well as measurement performed during the current project [Panagopoulos and Malliaros, 2005], demonstrated that the area is extensively contaminated with heavy metals and increased levels of acid generating materials. The objective of this study is to use FDM model to predict the particle concentration patterns distribution in the above basic geometrical configuration as related to different meteorological scenarios. The study area is presented in Figure 1. A 2-d section of this area in considered in this analysis for the application of the FDM model. The dimensions of the modelled region are 2500m in length and 2500m in width,

3 Figure 1. Geometrical Details of the Thoriko Bay Area considered for the environmental Remediation program. The above-mentioned different fencing techniques - configurations are depicted in Figure 2. The scenario 1 configuration serves as a base case in order to study the influence of the various fence arrangements to the final pollutant dispersion. 3. DISPERSION MODEL AND METHOD OF ANALYSIS 3.1 Short Description of FDM model The Fugitive Dust Model (FDM) is a computerized air quality model specifically designed for computing concentration and deposition impacts from fugitive dust sources. The sources may be point, line or area sources. The model has not been designed to compute the impacts of buoyant point sources, thus it contains no plume-rise algorithm. The model is generally based on the well-known Gaussian Plume formulation for computing concentrations, but the model has been specifically adapted to incorporate an improved gradient-transfer deposition algorithm. Emissions for each source are apportioned by the user into a series of particle size classes. A gravitational setting velocity and a deposition velocity are calculated by FDM for each class. Concentration and deposition are computed at all user-selectable receptor locations. FDM accepts hourly meteorological data allows printer and plotter output for 1-hour, 3-hour, 8-hour, 24-hour averages and a long-term average which is the average over the entire meteorological data base provided. More details are given at reference [USA EPA, 1990] 3.2 Meteorological Data Hourly wind measurements data for a period of five year were provided by Public Power Corporation (PPC) station located around 1 kilometer from the site. An analysis of data is shown in Figure 2.

4 Days 100 Ημέρες N NE E SE S SW W NW WIND Διεύθυνση DIRECTION Ανέμου WS > >= WS > 5 5 >= WS > 2 WS <= 2 Figure 2. Number of days with wind-speeds >10 m/s, between 5 and 10 m/s, 2 and 5 m/s and less than 2 m/s vs Wind Direction. Yearly Basis 3.2 Meteorology- the scenario examined For the assessment of air pollution impact two worse case real life meteorological scenarios were selected: May 2004 with max wind speed 10.8 m/s, min 7.0 m/s, mean 8.9 m/s, and direction N (towards city of Lavrion) June 2004 with max wind speed 5.7 m/s, min 2.8 m/s, mean 4.1 m/s and direction N again. 3.6 Boundary conditions PM emissions Dust is produced at the worksite at a rate of 1x10-6 g/m 2.s as proposed by US EPA AP42 methodology [USA/EPA, 1995]. Following on site soil sampling and analysis the dust particle size is considered as 20% of 10 microns and 80% of 30 microns. The incoming air entering the computational domain is considered free of dust. 4. RESULTS In the present work results for the pollutant PM concentration increments and the pollutant PM concentration increments due to the local construction activities are presented. These results are shown in Figures 3 to 6.

5 Figure 3. 25/5/2004 Mean Daily PM concentration increment (μg/m 3 ) from sites construction activities. Figure 4.25/5/2004 Mean Daily PM Surface Deposition Rate increment (μg/m 2 s) from sites construction activities.

6 Figure 5 28/5/2004 Mean Daily PM concentration increment (μg/m 3 ) from sites construction activities Figure 6.28/5/2004 Mean Daily PM Surface Deposition Rate increment (μg/m 2 s) from sites construction activities. As it shown in the figures the area experiences significant PM10 daily increment which became higher during the second day of the episode, contrary the surface deposition rate increment which seem to be reduced during the second day. 5. CONCLUSIONS The dispersion model (USA/EPA/FDM) was used in order to predict the PM dispersion patterns for heavy metals and toxic elements containing fugitive dust emitted from contaminated soil remediation construction activities. The model provides the tool to calculate the impact of different severe worse meteorological conditions on the PM dispersion patterns.

7 This methodology applied provides qualitative and quantitative data in order to assess the environmental impacts of soil remediation works and ensure the prevention of adverse environmental impacts and the protection of human health. The mathematical model analysis employed provided the basis in achieving good practice environmental management in the confrontation of fugitive dust dispersion during Soil Remediation Projects. It can also assist decision-making and provide greater certainty to the construction firms and the community in carrying out planning for Soil Remediation activities. 7. REFERENCES AP 42, Fifth Edition. Compilation of Air Pollutant Emission Factors, Volume 1: Stationary Point and Area Sources, US EPA, January Markatos, N.C. Computer simulation in techniques for turbulent flows. Encyclopedia of Fluid Mechanics. Vol. 6: Complex flow phenomena and modelling, GULF Publishing Company,Houston, Panagopoulos J.K, and Malliaros C. Environmental Remediation Study for the Thoriko Bay Prefecture of Athens, October Panagopoulos G., and Markatos N.C. A method of assessing the contribution of various pollution sources through mathematical modelling, International Conference on Environmental Pollution, Lisbon, April Panofsky, H.A. Atmospheric turbulence models and methods for engineering applications, John Wiley & Sons, New York, Region 10, U. S. Environmental Protection Agency, USER'S GUIDE FOR THE FUGITIVE DUST MODEL (FDM) (revised) Volume I: User's Instructions, EPA-910/ R, May, 1990.