The effects of agricultural practice and land-use on the distribution and origin of some potentially toxic metals in the soils of Golestan province, Iran

Soil samples were collected from the agricultural lands of Golestan province, north of Iran and analyzed for 24 elements including eight toxic metals of As, Cd, Co, Cr, Cu, Pb, Se and Zn. Electrical conductivity, pH, organic matter, soil texture, calcium carbonate content as well as soil cation exchange capacity were also determined. The possible sources of metals are identified with multivariate analysis such as correlation analysis, principal component analysis (PCA), and cluster analysis. In addition, enrichment factors were used to quantitatively evaluate the influences of agricultural practice on metal loads to the surface soils. The PCA and cluster analysis studies revealed that natural geochemical background are the main source of most elements including Al, Co, Cr, Cs, Cu, Fe, K, Li, Ni, Pb, V and Zn in the arable soils of the province (more than 90 %), however, those soils which have been developed on the mafic and metamorphic rocks were considerably contributed on metal concentration (43 %). Calcium and Sr were constituents of calcareous rocks and Na and S were mainly controlled by saline soils in the north of the province. Loess deposits was also accounting for high levels of selenium concentration. Phosphorous was mostly related to application of P-fertilizers and organophosphate pesticides. The comparison of metal load and enrichment factor for dry and irrigated farmlands showed that Cd, Co, Pb, Se and Zn had higher concentrations in the irrigated lands where considerable amounts of agrochemicals had been applied. However, it also found that proximity of arable lands to urban and industrial areas resulted in higher Pb and Cd values in the irrigated agricultural sources relative to dry ones.     

Dead Sea influence on the chemical and mineralogical characteristics of the dry deposition fallen over the eastern highland of central Jordan

The Dead Sea as a unique geological and geographical phenomenon has an effect on its adjacent areas. Therefore, 17 sampling sites at the eastern highlands facing the Dead Sea; beside three blank sites were collectedlocated during summer (2005). The aim was to investigate such influence on the chemical and mineralogical composition of dry deposition, and to measure the settling rate. The investigations showed that the depositional rate at the studied sites was much lower than other areas at central and southern Jordan. The average heavy metal contents are almost similar in all sampling sites and the blanks, and they exhibit similar enrichment series, whereas, the meaningful difference between sampling sites and blank was in cation and anion content, which caused different enrichment series between the two sites. The index of pollution (IP) confirms that mainly cations and anions have IP > 1.0 and they dominate the southern and the closest sampling sites to the Dead Sea. The XRD results reveals that the studied samples have minor phases such as halite, gypsum, and dolomite. Meanwhile, these mineral phases are not found in blank samples. All these results indicates the influence of the Dead Sea, as it is a highly saline large water mass, which accompanied with by high evaporation rates causing causes the atmosphere over the Sea to be enriched with these cations, anions, elements and minerals, which eventually are adsorbed in air particulate or carried out as dry deposition and transported by the NW–SE prevailing winds, and fall over the eastern highlands.