These standards and guidelines specify PM₁₀ maximum values for short-term exposure (24 hours) and long-term exposure (annual) limits; the exceedance of concentration limits might adversely affect human health and the environment. Limits values given in Table 1 are applicable to most individuals in the general population.

Mussafah area is an industrial town located 30 kilometers Southeast of Abu Dhabi City, UAE. Also known as “Mussafah Sanaiya”, it is one of the most important economic areas of the UAE and has been designated a special economic zone, with numerous factories and port. The concrete batching facilities are mainly located and clustered in the Mussafah industrial area- M35 zone, which is located in the old industrial area of the Abu Dhabi Emirate, surrounded by mixed-use industrial, commercial, and residential areas. The estimated total area is approximately 1,000,000 m² as shown in Figure 1, and the study area boundary is represented in Table 2. M35 has more than 25 concrete batching facilities equipped with 176 cement silos in one location operating under the cement and cement products industrial sector. Consequently, it is imperative to conduct an environmental assessment of this industrial area to determine and assess the impacts on the environment and sensitive receptors.

Field visits and interviews were conducted on 25 concrete batching facilities located in the study area to collect facility-specific information such as annual production, raw material usage, additives, energy consumption, and other process-related details. Data collection surveys to each plant were distributed to get sufficient data to calculate emissions rates. Critical review and quality check on survey responses using statistical software to ensure the data is adequate to provide robust and accurate input to the model.

One of the critical steps in conducting air dispersion modeling is to quantify the emission rates for each single cement silo at the 25 targeted facilities in M35. The emission rates for the sources identified were derived from US EPA Air Pollutant Emissions Factors (AP-42), Section 11.12 Concrete Batching emission factors. Cement annual consumption for each facility (average per facility is 88 159.72 MT/year) and emissions factor for controlled pneumatic transfer of cement to a storage silo using efficient air pollution control devices (APCD) was 0.00017 kg/Mg of cement transferred. The emissions factor for uncontrolled emissions for the pneumatic transfer of cement to a storage silo was 0.24 kg/Mg of cement transferred. The uncontrolled scenario means the filter was not operating properly, and there was no level of control [16] .

In this work, a commercialized air dispersion model utilizes EPA’s AERMOD is used (AERMOD View, Version: 9.9.0, Lakes Environmental Software). It calculates the hourly and annual air concentrations and deposition fluxes resulting from air pollutants emitted from the cement silos at selected downwind sensitive receptors to address the potential air quality issues by estimating and predicting the GLC of air pollutants. The required input files were created using sources’ emissions rates and meteorological inputs to run the chosen study area domain model.

Scenario 1: represents the ideal operations of the concrete batching facilities, where all the 176 cement silos capture emissions to APCD, such as fabric filters that are capable of collection efficiencies greater than 99.9 percent [6] [7] . Cement annual consumption for each facility and emission factor (0.00017 kg/mg) was used to calculate PM₁₀ emission rates (g/s) for every single controlled silo. The calculations estimated that the PM₁₀ cement dust emissions from 176 controlled cement silos located in the selected domain would contribute to air pollution by a total of 374.68 kg/year, and the average emission value per facility is 14.99 kg/year.

The maximum annual average PM₁₀ resulting from regular concrete batching facilities operations in M35 is presented in the form of contour plots in Figure 9. The highest average yearly concentration predicted outside the M35 area towards the West was 0.065 μg/m³. Within the M35 boundary area, the highest concentration predicted was 0.199 μg/m³. PM₁₀ maximum annual average values at all sensitive receptors were predicted to be negligible, corresponding to (15 μg/m³) WHO guidelines.

The maximum daily average PM₁₀ resulting from controlled cement silos are presented in the form of contour plots in Figure 10. The highest daily average concentration predicted outside the M35 area boundary line towards the East was 0.6 μg/m³; however, the highest concentration value predicted in 2190 days (6 years) within the M35 area boundary line was 0.725 μg/m³. The maximum daily average PM₁₀ predicted values at all the sensitive receptors are not significant and negligible compared to the 24-hour average (150 μg/m³) NAQS and (45 μg/m³) WHO guidelines. Therefore, the incremental increase incurred by the 176 controlled cement silos for annual and daily concentrations of PM₁₀ will not lead to significant air quality degradation in the entire study domain.

Scenario 2: represents the worst-case operational scenario of concrete batching facilities, where all 176 cement silos fail to capture cement dust PM₁₀ emissions. Cement annual consumption for each facility and emission factor (0.24 kg/mg) was used to calculate PM₁₀ emission rates (g/s) for every single uncontrolled silo. The calculations of total PM₁₀ emissions from entire facilities are estimated to be 528958.32 kg/year, and the average PM₁₀ emissions value per facility is 21158.33 kg/year. These calculations indicated that the uncontrolled PM₁₀ emission sources would significantly contribute to air pollution by multiplying PM₁₀ emission quantities emitted to the atmosphere by 1400 times than quantities emitted from controlled sources, as shown in Figure 11.

The maximum five daily average PM₁₀ emissions predicted are 1250.09 μg/m³, 1236.57 μg/m², 1187.06 μg/m², 1078.47 μg/m^3, and 992.59 μg/m^3, respectively, inside the study area boundary line as presented in Table 3. These elevated concentrations in the vicinity of the study area boundary may have a short-term impact on the local air quality within the study area boundary; consequently, this will significantly affect the overall air quality.

Uncontrolled or dis-repaired cement silos have no control efficiency. They would lead to high PM₁₀ emissions resulting in a predicted maximum daily average PM₁₀ of 800 μg/m³ outside the study area boundary towards the West and East directions, as presented in Figure 12. The predicted concentration value

was 5.3 times the maximum PM₁₀ daily average of NAQS (150 μg/m³) and 16 times the 24-hour mean of WHO guidelines (45 μg/m³).

The maximum PM₁₀ predicted concentration values at the top 8 impacted sensitive receptors locations within the computational domain were presented in Table 4. The maximum predicted PM₁₀ concentration value is 393.92 μg/m³ at the school 720 meters away from the study area boundary towards the North direction. The maximum daily average PM₁₀ predicted values at eight sensitive receptors are significant compared to the 24-hour average of NAQS (150 μg/m³) and WHO guidelines (45 μg/m³) and may cause significant health effects.

The maximum annual average GLCs of PM₁₀ resulting from uncontrolled cement silos are presented in the form of a contour plot in Figure 13. The highest annual average concentration of 328.08 μg/m³ was predicted inside the study area boundary and was presented in Table 3. The highest concentration predicted outside the M35 boundary towards the West direction was 100 μg/m³. This predicted value is five times higher than the (15 μg/m³) WHO annual mean. However, at all sensitive receptors, the maximum annual average GLC was predicted to be more than or equal to 20 μg/m³ at only two residential area locations, as presented in Table 5. This may cause significant health effects on residents. However, guideline values would not be expected to protect everyone because human responses do not occur at precise exposure levels.

Comparable results have been found in the Environmental Impact Statement (EIS) of Hanson Eastern Creek’s Concrete Batching Plant in NSW, Australia, operating 24 hours a day, seven days a week. The estimated particulate matter (PM₁₀) emissions from unloading 131 tons of cement per day, equating to 47,808 tones annual average into four controlled silos, is 81 kg/year on a typical operational day and 168 kg/year on a peak operational day. The annual average predicted downwind concentrations of PM₁₀ at 30 sensitive receptors recorded a minimum value < 0.01 (μg/m³) and a maximum value of 0.828 (μg/m³) from the overall activities [18] . Also, Windlectric Inc Ready Mix Concrete Batching Plant

in Ontario, Canada, operates 12 hours daily, five days a week, and has two controlled silos. The PM₁₀ emissions estimate is 0.0002856 (kg/day) from the daily usage of 335 (kg/m³) of cementation material, and the maximum daily predicted concentration from all the facility emission sources is 3.9 (μg/m³) [19] . Both cases undertook air quality assessment for permitting purposes and were conducted using AERMOD air dispersion modeling. Emissions rate inputs and predicted concentrations observed vary based on several main factors that affect the calculations, such as cement loading quantities and flow rate into the silos, APCD efficiency, facility capacity, production rate, and operating hours.