Air quality management in the uMhlathuze municipality using air dispersion modelling.

The results revealed that the permitted emission scenario led to exceedances of the SAAAQS 1-hour and 24-hour average concentrations over most of the uMhlathuze municipal area. 50 4.2 Comparison of the maximum 1-hour average concentration (µg/m3) of current and previous studies and the total SO2 emissions used for modelling.

INTRODUCTION

Introduction
Rationale for this Study
Aims and Objectives
Study Area

Land Use Zoning
Meteorological Characteristics of Richards Bay

Structure of Dissertation

UMhlathuze Municipality in KwaZulu-Natal was chosen as the site where dispersion modeling could be used to inform air quality management in the municipal area. To compare the results of the Calpuff model used in this study with other recent modeled results in uMhlathuze municipality;.

Table 1.1 Air Pollution Sources within the uMhlathuze Municipality (uMhlathuze SER, 2002)

AIR QUALITY MANAGEMENT APPROACH AND URBAN AIR

Introduction
Legislative Context

Atmospheric Pollution Prevention Act (APPA)
Air Quality Act (AQA)

Urban Air Pollution Dispersion Models

Types of Urban Air Pollution Models
Uncertainties in Air Dispersion Modelling

Air Pollution Potential

Synoptic Scale Circulations
Meso-scale Circulations

An air quality guideline is a recommendation on the limit value for the ambient concentration of a pollutant in the atmosphere that is necessary to protect human health. A comparison of the EU, US, UK, WHO, SANS and DEAT guidelines is presented in Table 2.1.

Table 2.1 Comparison of the SO 2 standards and guidelines for the EU, US, UK, WHO, SANS and the DEAT

METHODOLOGICAL FRAMEWORK

Introduction
The Air Pollution Model (TAPM)

General Description
Rationale for using the TAPM model
Limitations of TAPM

Calpuff Model

General Description
Rationale for using the Calpuff Model
Modelling Options Selected

Receptor Network
Sources of Data and Data Description

Emissions Inventory
Meteorological Data

The upper air data provide information such as the extent of the mixing layer in the modeling domain, which is not measured in uMhlathuze municipality. Validation studies performed for the Calpuff model are detailed in USEPA guidance documents (United States Environmental Protection Agency b; 2005). The use of Calpuff will be a valuable comparison with other models in the uMhlathuze municipality area.

In addition, the HAWK model has been validated twice by the model developer in the Richards Bay area (CSIR. This study has therefore focused on planned process industries as the largest source of SO2 emissions in uMhlathuze Municipality. In the study conducted by CSIR ( 2004) and CSIR ( 2005), the meteorological surface data were obtained from the RBCAA monitoring network and SAWS, while the upper air data were obtained from the CSIRO TAPM model.

Figure 3.1 Map showing regions where meteorological analyses are available for TAPM (http://www.cmar.csiro.au/research/tapm/index.html)

MODEL RESULTS

Introduction

Scenario 1: Control Run

Maximum 1-hour Concentrations
Annual Average Concentrations

The results of the current study are greater than those of the other two and it is likely that the higher SO2 emissions used in this study lead to the increase in results. It should be noted that due to its proximity to major industries in the industrial cluster, the. The frequency of exceedances of the 1-hour standard of 350 μg/m3 over a period of 3 years at the 9 selected receptors is shown in Table 4.3, with 1216 exceedances occurring in the industrial cluster.

The Airshed (2006) and CSIR (2005) studies did not report on the number of exceedances of SANS 1929 or DEAT ambient standards. The position of the highest 24-hour SO2 concentration shown in Figure 4.2 occurs in the industrial cluster and shows a north/south oriented scatter pattern. The frequency of exceeding the 24-hour average standard is highest in the industrial cluster and is limited to the CBD as shown in Table 4.5 and Figure 4.2.

Figure 4.1 Scenario 1: Maximum 1-hour average SO 2 concentrations in µg/m 3

Scenario 2: Worst Case with Permitted SO 2 Values

The concentration at all receptors exceeded the 1-hour standard of 350 μg/m3. The Airshed (2006) study recorded a maximum 1-hour average of 3750 μg/m3 for all industries operating at the permitted emission rates as shown in Table 4.8. Compared to the 24-hour maximum concentrations predicted from actual emissions, the permitted scenario shows a larger area exceeding the daily average standard of 125 µg/m3 (Fig. 4.5). The Airshed (2006) study gave a result of 985 μg/m3 for the maximum 24-hour average shown in Table 4.10, which is very similar to the results obtained in this study.

The number of times the 24-hour standard was exceeded at each selected receptor is shown in Table 4.11. Compared to the control run which produced 226 24-hour average exceedances in the industrial cluster, the permitted emissions scenario produced 567 24-hour average exceedances in the same area. Compared to the annual concentrations in the control run, the permitted scenario affects a slightly larger area (Fig. 4.6).

Scenario 3: Permitted Values reduced by 25%

Maximum 1-hour Concentration

In the control run, the maximum one-hour average SO2 concentration of 2520 µg/m3 was predicted in the area of the industrial cluster, and a reduction of the permitted emissions by 25% results in a concentration of 3172 µg/m3 in the same area. The number of exceedances of the 1-hour average standard in Table 4.14 compared to the control is higher at all receptors, except for Mondi Felixton, where the actual emissions from Mondi Felixton were higher than allowed. The number of exceedances in Alton and the industrial cluster is above the EU limit of 24 one-hour average exceedances per year.

The isoline of the 125 μg/m3 24-hour average limit shown in Figure 4.8 encroaches on the residential areas of Brackenham, Veldenvlei and Arboretum, but there are no exceedances at the receptors in these areas. The number of exceedances in Alton and the industrial cluster is above the EU limit of 3 permitted 24-hour average exceedances per year. The area beyond the annual average standard of 50 µg/m3 is limited to the industrial cluster area (Fig. 4.9), without exceeding the standard in the residential or business areas.

Table 4.13 Summary of SO 2 sources for scenario 3

Scenario 4: Permitted Values reduced by 50%

The number of exceedances of the 1-hour standard at the industrial cluster, the CBD, Arboretum and Veldenvlei is higher for this scenario (50% reduction in permitted emissions) than the corresponding results of the control run depicted in Table 4.5. So far, the results obtained for this scenario are closer to the results obtained in the control scenario, implying that the industries are currently operating at approximately 50% of their permitted limits. The number of exceedances in the industrial areas is above the EU limit of 24 1-hour average exceedances allowed per year.

The area surrounded by the 125 μg/m3 SO2 isoline is limited to the industrial areas and does not have a significant impact on the residential areas as shown in Figure 4.11. The number of exceedances is above the EU limit of 3 24-hour average exceedances allowed per year in the industrial areas, but not in the residential areas (Table 4.18). The maximum annual mean concentration obtained is 80 μg/m3 compared to 86 μg/m3 obtained in the control run.

Table 4.16 Summary of SO 2 sources for scenario 4

Scenario 5: Permitted Values reduced by 75%

Maximum 1-hour Concentration

The DEAT National Framework describes the implementation of air quality standards based on five classes of air quality impact zones. The results from the Calpuff model were compared with other recent modeling studies conducted in the area and with the South African Ambient Air Quality Standards for SO2. The municipality must take this new guideline into consideration when setting its own air quality limits (WHO, 2005).

Concerns about the health impacts of air pollution are increasing in the uMhlathuze Municipality following the trend in air quality complaints. CSIR, 2004: Air Quality Specialist Study for the proposed Tata Steel ferrochrome smelter at Richards Bay. European Union, 2004: Comparison of EU and US air quality and planning requirements, Case Study 2, p14.

Table 4.19 Summary of SO 2 sources for scenario 5

Summary of Modelled Results

Comparison of the Modelled and Ambient Monitoring Results

The RBCAA monitoring network has five surrounding stations which are described in more detail in the RBCAA monthly and annual reports which can be accessed via the RBCAA website (www.rbcaa.co.za) and are depicted in the map shown in Figure 4.15. Offenses occurred at Scorpio station (between Hillside and Foskor); the Caravan Station (in the CBD) and the Arboretum Station in the Arboretum residential area. Compared to the control run in this study, which represents the actual or baseline emission scenario, the number of exceedances of the maximum hourly and daily averages is significantly higher than that based on the RBCAA measured results.

There were 13 exceedances of the 1-hour average standard measured by the RBCAA in 2005 and 7 of these exceedances occurred in the CBD area (RBCAA, 2005). By comparison, in the modeled control, there were 18 exceedances of the 1-hour average standard at the receptor in the CBD area, which is approximately three times more than the measured results. It is generally observed that with an averaging period of 24 h, a close correlation occurs between the results from this study and the Airshed (2006) study for the 24 h permitted scenario and the number of SO2 exceedances measured by the RBCAA during the 24 h period at the CBD station.

Implications for Air Quality Management

Implications for Industry to Comply with Ambient Air Quality Standards The current interpretation of AQA means that ambient air quality beyond the boundary of an industry must comply with ambient air quality standards. Based on AQA's goal to regulate ambient air, the scenarios in this study show that all major industries must implement emission reduction measures in order to comply with ambient air quality standards along their lines of production. the fence. Consequently, the municipality is responsible for ensuring that discrepancies between point source emissions and ambient air quality compliance are addressed in the AEL process of all major industries.

The zones include target levels that are expected to represent 80% of national air quality standards; alert levels that can be 90%. In countries such as the United Kingdom (UK), local authorities must implement air quality action plans for areas where ambient air quality standards are exceeded. If limit values are exceeded, local authorities must submit air quality action plans.

CONCLUSION

Summary

It will be the municipality's responsibility to drive emission reduction plans through its AQMP. The results of this study were compared with Airshed (2006), CSIR (2004) and CSIR, (2005) studies which used the HAWK model to estimate ambient concentrations of SO2. The results are consistent and the variations can be attributed to differences in the input SO2 emissions used in the modeling exercises.

A direct comparison of the results can be made with the Airshed (2006) study regarding the permitted levels of SO2. Based on the assumption that the allowable levels of SO2 for all major industries in the uMhlathuze area have not changed since 2004, there is close correlation between the allowable emission scenario in this study and the Airshed (2006) study.

Recommendations

Airshed, 2006a: Revision of spatial development framework for the city of uMhlathuze based on an air quality investigation. Cairncross, E.K., 2005a: Peer review of the air quality and health impact study undertaken as part of the Tata Steel Proposed Ferrochrome Project (Draft). Document reviewed: CSIR Environmentek (2005) air quality specialist study for the proposed Tata Steel ferrochrome project at Richards Bay – Alton North site.

CSIR, 2005: Specialist air quality survey for Tata Steel's proposed ferrochrome project at Richards Bay – Alton North Site. Douglas, G.F., 1982: Uncertainty in air quality modeling, a summary of the AMS workshop on Quantifying and communicating model uncertainty, Bulletin. South Africa, 2005a: Commencement of certain parts of the National Environmental Management: Air Quality Act 2004 (Act No. 39 of 2004).

A Comparison of the Gaussian Plume and Gaussian Puff Model

Calpuff Modelling System