Spatial distribution and source identification of heavy metals (As, Cr, Cu and Ni) at sub-watershed scale using geographically weighted regression

Heavy metals are among the most important sources of water and soil pollution.These elements accumulate in the agricultural soil through using contaminated water for irrigation,fertilizers,pesticide and enter to the river systems by water erosion.Therefore,land use plays a serious role in water and sediment pollution.In this regards,geographically weighted regression was used to investigate the spatial correlation between sediment heavy metals and land uses in a highland watershed.The landuse map was used to calculate the area percentage of landuse types in sub-watersheds,followed by geographically weighted regression method to investigate the spatial correlation of As,Cr,Cu and Ni versus three types of land uses.The highest correlation was observed for irrigated plots versus As and Ni in upstream and for rainfed plots versus AS,Ni and Cr in the downstream.The relationship between heavy metals and developed lands was more complicated and the highest correlation was found for Ni and As at outlet (R2 =0.52-0.89),for Cr in the upstream (R2 =0.50-0.76),and for Cu in the upstream and downstream (R2 =0.36-0.60).The results indicated that there is a positive correlation between heavy metals and land uses which varies with the level of agricultural and urbanization development at subwatershed.Based on the findings,appropriate policies and decisions should be taken on agricultural land to prevent the transfer of heavy metals by sediment to aquatic environments.

Country-scale spatio-temporal monitoring of soil erosion in Iran using the G2 model

The aim of this study was the spatial and temporal monitoring of soil erosion patterns in Iran.The G2 model was used,as an appropriate tool to provide the required month-time step country-wide soil loss maps and statistical outputs.The input parameters were derived with field surveys and remote sensing imagery(MODIS,SRTM,SPOT,and Sentinel-2 scenes).An innovation for G2 was the consideration of the snow cover effect on the rainfall erosivity.It was also the first time G2 was used to map such a big country like Iran on a country scale.The mean annual soil erosion in Iran was found to be 16.5 t ha−1,which is equal to about 2.7 billion tons of soil loss.In spatial terms,the highest soil loss values were found in the north,west and southwest part of Iran,in the steep slopes in Alborz and Zagros mountains.In temporal terms,the highest and lowest monthly erosion values of 3.2 and 0.09 t ha−1 correspond to January and July,respectively.

Effects of type, level and time of sand and gravel mining on particle size distributions of suspended sediment

Monitoring the sediment transport behavior induced by different interventions, particularly sand mining from rivers, is needed to adaptively manage the watersheds. The particle size distribution of the sus-pended sediment in up and downstream of rivers is one of the main indicators to know about fate of sediments, which may be varied in different conditions. We investigated the effect of some types of sand and gravel (i.e., manual and low, semi-heavy, and heavy machinery) mining on particle size distribution of suspended sediment in the Vaz-e-Owlya, Vaz-e-Sofla and Alesh-Roud riverine mines located in Ma-zandaran Province, northern Iran. The study was conducted on a monthly basis from February, 2012 to January, 2013. Laser granulometry was used to analyze the particle size distribution of suspended se-diment samples taken from up and downstream sections of the study mines. The results revealed that the level and intensity of mining activity affected particle size distribution of suspended sediments. Further statistical assessments in up and downstream sections of the mines proved that sorting, D50, mean, D90, kurtosis, skewness and D10 of the suspended sediment were not significantly influenced by mining activities at levels of 0.09, 0.11, 0.12, 0.15 to 0.69, 0.15–0.69, 0.77, 0.87, 0.97, respectively. While it was not statistically significant, we found that the type of mine and the level of the exploitation changed the particle size distribution of the suspended sediment.

Spatiotemporal dynamic of environmental indices of watershed sustainability in connection with land-use change

Exploring spatial and temporal land-use changes is valuable for local governments to address issues of sustainability and planning policy where urbanization and industrialization are taking place.Besides anthropogenic effects,natural driving forces like climate change may also affect sustainability.However,such relationships have not been studied minutely.Hence,this study first investigates the land-use changes and their relationship with land surface temperature(LST)for the Shazand Watershed,Iran,in 1986,1998,2008,and 2016 coincided with supplementary industrialization stages.Furthermore,the relations among LST and other biophysical parameters,including Normalized Difference Vegetation Index(NDVI),Normalized Difference Buildup Index(NDBI),and Normalized Difference Water Index(NDWI),were analyzed,and corresponding variations were explored.The results indicated that the mean LST of the study watershed has an increasing trend from 1986 to 2008 due to land-use change and drought intensification.Later,LST decreased in 2016.Lower LST was associated with irrigation farming and orchard,and higher LST was related to sparse oak forest areas.There was also a negative correlation between LST and NDVI.As a result,it was inferred that greenery declined LST.Conversely,a positive correlation was found between LST and NDBI resulting from the built-up areas.Since LST could influence biological,physical,chemical processes,it can therefore be supported as an effective index for environmental sustainability assessment.

Assessing the health and ecological security of a human induced watershed in central iran

Assessment of the watershed health and associated ecological security is crucial for the proper land resources management,notably when sufficient money and time have lacked.The present study aimed to prepare health and ecological security for the Pishkuh Watershed in Yazd Province,central Iran.To prepare the health atlas of the Pishkuh Watershed,the conceptual framework of pressure,state,response(PSR)was employed.The pressure index was investigated by analyzing the driving forces of natural and human-induced factors.Then,the existing conditions of the natural environment and the watershed performance were analyzed using the state index.Besides,the response index was also calculated as a criterion for expressing the degree of community response or different watershed outcomes to the driving forces imposed on the watershed system.The study results revealed that some 91 and 9%of the watershed were classified as moderately healthy and relatively unhealthy.The results of the ecological security index further showed that some 41%of the area was categorized as relatively poor status.The results of the current study can be used by local managers and decision-makers to adaptively designate appropriate,economic,and goal-targeted solutions for the resources management in the region.