Environmental Erosion Research Journal

---

Extended abstract
1- Introduction
One of the environmental crises that have caused a lot of concern in recent years is the pollution caused by wind erosion in arid and semi-arid regions, especially in Iran. Recently, it has been reported that about 26% of changes in atmospheric dust concentrations occurred due to changes in the drought index resulting from changes in precipitation to evapotranspiration. Increasing air pollutants concentrations, especially dust particles, had negative effects on agricultural production, human health, and the environment. Therefore, temporal and spatial analysis and continuous monitoring of these events in different regions, especially in arid and semi-arid regions, are of great importance. Accordingly, the main purpose of this study is to analyze the trend of dust pollution caused by wind erosion at different time scales and to investigate the spatial distribution of dust particles in Fars province, southwestern Iran, during the years 2000 to 2018.
2- Methodology
In this study, using the pollution of dust storm index (PDSI), the pollution caused by wind erosion events in eleven synoptic stations located in Fars province was calculated. The frequency of local, moderate, and severe dust events was used to calculate this index. Then, the Mann-Kendall test was used to analyze the trend of monthly, seasonal, and annual changes. The trend of changes was calculated separately for the study stations. Furthermore, the map of spatial changes of air pollution in Fars province from 2000 to 2018 was prepared using the reverse distance weighting method. Finally, areas more sensitive to wind erosion were identified based on the generated maps using this method.
3- Results 
Analyzing the trend of monthly changes in PDSI using the Mann-Kendall test showed that the most incremental and significant changes in dust pollution occurred in April, May, and February in Fasa, Shiraz, Dorodzan, and Zarghan stations. Meanwhile, the trend of decreasing and significant changes in PDSI has occurred mainly in Lar and Darab stations and from May to October. The results of the seasonal change trend showed that regardless of the confidence level, more than 70% of the study stations have experienced an upward trend in spring, summer, and autumn. In winter, all stations except Darab station have experienced increasing changes in air pollution. On an annual scale, the trend of decreasing changes was observed only in Darab and Lar stations, while the trend of changes in other stations of Fars province was increasing. The pattern of the spatial distribution of dust particles in Fars province showed that in 2003 and 2005, more than two-thirds of Fars province and mainly the central to southeast areas were faced with high dust concentrations. In recent years, and especially in 2017 and 2018, the distribution of dust particles has changed. In recent years, residents of the central to southwestern Fars province have suffered more from reduced air quality due to increased concentrations of atmospheric dust particles.
4- Discussion & Conclusions
The growing trend of dust pollution caused by wind erosion events in recent decades has raised major concerns at various regional, national and global levels. Therefore, it is necessary to understand the trend of temporal and spatial changes of pollution caused by these events to reduce their adverse consequences in different regions. Based on the findings of this study, the trend of temporal changes in dust events and the pattern of dust particle distribution in the southern half of Fars province is also worrying because, in most cities of Fars province, an increasing trend in air pollution was observed. In addition, according to PDSI maps, a large part of the province is exposed to the dangers of dust storms and air pollution. Considering that PDSI is calculated based on the frequency of local to severe events, it can be concluded that the frequency of wind erosion events has increased in most cities of Fars province. In other words, these findings indicate the intensification of dust events and pollution caused by it in this province. Our results also showed that in the long-term (2000-2018), the southern half of Fars province, compared to the northern half, was more sensitive to dust events and, as a result, played a major role in dust production across the province. One of the reasons is drying the bed of Bakhtegan-Tashk, Maharloo, and Parishan wetlands, located in the southern half of the province, and have acted as dust generating sources, especially in recent years. As a whole, the results of this study can help managers and planners to prioritize managerial and executive measures to combat the risk of desertification and reduce the adverse impacts of dust storms in dusty areas.

---

1- Introduction
In recent years, Minab plain, one of the most important agricultural plains in the south of the country, has experienced extensive land subsidence. Also, the study of the groundwater level of the Minab plain in a long-term periods showed that since 2001, the drop in the aquifer level has intensified and an average annual drop of 42 cm has been observed. Furthermore, previous geotechnical studies in the region have shown that besides the drop in groundwater level, the presence of swollen  and soluble sediments has increased the severity of subsidence in the Minab plain. According to the evidences of the previous studies and damages caused by land subsidence to infrastructure, buildings and agricultural lands, recognizing this phenomenon, identifying areas sensitive to it and investigating the factors affecting its occurrence can play an important and effective role in predicting land subsidence and preventing associated damages. In the current study, unlike other land subsidence studies, which emphasized the drop in groundwater level and the type of geological formations, the characteristics of soil and land surface in the explanation of subsidence phenomenon have been considered.

2- Methodology
The study area of ​​Minab plain with an area of ​​653.6 square kilometers is located between the longitudes of 56° 49' to 57° l5' East and latitudes of 27° 1' to 27° 19' North. First, a time-series analysis of Sentinel-1 radar was performed to identify the land subsidence sites and calculate the displacement rate. After calculating the vertical displacement, for the spatial modeling and the preparation of land subsidence hazard map of Minab plain, data mining methods were employed with soil and land surface features. The investigated time period in the present study covers the years 2015, 2017 and 2019. Spatial variations of 12 variables including soil texture, vegetation, percentages of sand, silt and clay, land surface temperature, soil bulk density, land cover type and soil salinity were gathered and prepared using Google Earth Engine (GEE) and TerrSet software to be used as independent variables of the spatial model. Then, by using Naïve Bayes (NB), Decision Tree (DT) and k-Nearest Neighbor (kNN) data mining models in the RapidMiner software platform, the necessary information was extracted to map the potential land subsidence zones. It is noteworthy that in the constructed models, the land subsidence map for different years (resulting from Sentinel-1 radar image processing) was considered as a dependent variable and the maps accociated with 12 variables mentioned were considered as independent variables. Performance criteria such as classification error, kappa coefficient, absolute error, normalized absolute error, relative error, and root mean squared error were used to evaluate the resulting models with respect to spatial accuracy.
3- Results
The amount of subsidence for 2015, 2017 and 2019 is computed 3.61, 0.92 and 5.69 cm, respectively. The results obtained by interferometry processes showed that the land subsidence progresses from the central parts of the plain to the edges of the plain and the eastern areas of Minab plain have less amount of land subsidence compared to other areas. Overlap of sinkhole points recorded in the field survey also showed good agreement with the results of radar image analysis. The highest rate of land subsidence, which was equal to 5.69 cm, occurred in 2019. This amount of land subsidence is certainly hazardous for agriculture, the environment and the facilities in the study region.
4- Discussion & Conclusions
Among the independent variables, vegetation, heavy soil texture and soil salinity had a more meaningful effect on different land subsidence classes. Also, among the models used for land subsidence risk mapping, the performance of the decision tree method with an accuracy of 63.15, classification error of 36.85, kappa of 29.7, absolute error and relative error of 0.5, normalized absolute error of 0.45 and the sum of the squares error of 0.56 was better than the other two models. Findings of this study showed that soil and land surface characteristics have the ability to express 0.6 of the variance of land subsidence phenomenon in the region and for more accurate modeling, effective data such as changes in groundwater level and the geological material of aquifer can be used. Also, the findings of this study as well as the prepared map of potential land subsidence occurrence in different parts of the study area can play an important role in risk reduction, land use planning and water resources management in the region.
 

---

1- Introduction
Dust aerosols have adverse effects on public health, air quality, and the environment; therefore, continuous monitoring of their spatio-temporal changes in different regions, especially arid and semi-arid regions, is very important. Considering the vast spatial extent of Kerman province, the inappropriate distribution of air pollutant measurement stations, a number of synoptic stations, as well as the large area of the province and the different climatic and biological diversity; the use of remote sensing techniques and especially the use of Aerosol optical depth (AOD) index of the MODIS sensor can be one of the appropriate tools to analyze and investigate the trend of temporal changes and the pattern of spatial distribution of dust particles in different regions of this province. This study has been carried out with the main purpose of analyzing the changes in dust aerosols based on the average monthly, seasonal and annual values of aerosol optical depth in different regions of Kerman province during the period from 2000 to 2022, so that while knowing the state of these changes, the high-risk areas of dust production in recent decades should also be identified.
2-Methodology
In the present study, the MODIS sensor aerosol optical depth index product (MCD19A2) was used to analyze the trend of changes in dust aerosols in different regions of Kerman province. In order to validate this product, the average daily horizontal visibility recorded on the days of dust events was used. The data related to the MCD19A2 satellite product was downloaded through programming in the Google Earth Engine environment for different cities of Kerman province in the period from 2000 to 2022. After filtering the dusty days (AOD>0.5), the average values of the mentioned index on monthly, seasonal and annual time scales were calculated separately for each region. The Mann-Kendall test was then used to analyze the temporal changes of the optical depth of dust aerosols in different regions of Kerman province.

3- Results
Based on the spatial distribution pattern of the air quality, it was found that the air quality of the eastern half in March and April was lower than other areas of the province, while in the central areas, the air pollution was less and the air quality was more favorable. The results of the Mann-Kendall test showed that in June and December, the trend of changes in the dust aerosols optical depth in more than two thirds of Kerman province had a non-significant decrease (Z>-1.96). This is why in November and May, half of the province and in other months more than two-thirds of the province have experienced incremental changes over the last 23 years. The pattern of long-term average spatial changes of the optical depth of aerosols on a seasonal scale showed that Kerman province was more affected by aerosols in the spring and summer seasons. Maximum dust pollution has occurred from Raver to Rigan, Jiroft to Manojan, Sirjan and Anar cities. The mentioned areas in the cold seasons of the year have also experienced the worst conditions in terms of the presence of aerosols, but their concentration has been significantly lower compared to the warm seasons of the year. The results of the Mann-Kendall test showed that 75% of the cities of Kerman province have faced an increasing-insignificant trend of spring dust events, which has led to an increase in the concentration of aerosols. In summer, these changes were increased in more than 95% of the province's regions, and the most changes were observed in Anar, Baft, Fahraj, Kohnouj, Kohbanan, Orzuiyeh and Rafsanjan. Although in the fall season, about 25% of the regions of the province had a decreasing trend and about 4% had no particular trend, but in more than 70% of the regions of Kerman province, the trend of changes in dust aerosols was an increase, and among the regions with a positive trend, the cities Baft and Jiraft had the worst conditions (Z>1.96). The remarkable result is the rising trend of dust and dust aerosols in all regions of Kerman province during winter, particularly in the cities of Anar, Anbarabad, Baft, Faryab, Ghaleganj, Manojan and Rabor. Although Anbarabad, Baft, Orzuiyeh, Shahrbabak and Sirjan exhibit a stronger annual increase compared to other areas, the rise in AOD changes is evident throughout the province. This 23-year trend indicates that Kerman has not experienced favorable conditions, highlighting the increasing frequency of dust events in this desert region.
4- Discussion & Conclusions
Based on the findings of the analysis of the temporal changes of dust aerosols; the western cities of the province have become more sensitive to the phenomenon of wind erosion compared to the past. This can be a serious threat to the residents of these areas. On the other hand, the increasing trend in the southern and eastern regions highlights the intensification of dust events, contributing to the decline in air quality in the province over recent decades. Considering the intensification of the phenomenon of wind erosion and dust storms in many areas of Kerman province, it is necessary to control this phenomenon in order to increase the health security of the residents of the affected areas. Although the awareness of the spatial and temporal changes of dust aerosols has led to an increase in our understanding of the phenomenon of wind and dust erosion in the province, but in order to prevent, control and reduce the risks caused by the occurrence of this destructive environmental phenomenon, it is necessary to identify the main driving factors of these changes that are suggested to be investigated separately for each city in future researches.