Geochemistry of cryoconite and soils in the Central Caucasus region and its environmental implications

Climate change and deglaciation are active processes in current changing environments.In the Central Caucasus region rapid degradation of glaciers is caused often by the formation of superficial blackcolored sediments-cryoconite.Cryoconite plays a crucial role in changing ecosystems and may contribute to the formation of primary soils after glacier retreat.Over the past 20 years,the frequency of mudflows and other dangerous mountain events have increased in the Central Caucasus,which is associated with the glacial retreats.Intensification of tourism results in increasing of traffic,recreational activity and environment contamination.Determination of the cryoconites geochemical properties in comparison with other types of sediments and local soils is crucial for investigation of geochemistry and contamination state of superficial glacial sediments.This environmental aspect is important in terms of the Central Caucasus settlements safety under conditions of deglaciation and anthropogenic influence.The sediments studied(cryoconite,mudflow,moraine)were sampled at Garabashi and Skhelda glaciers as well as some local soils at the Baksan gorge.Sampled materials were investigated in terms of physicochemical and agrochemical parameters.The concentrations of trace elements(Cu,Pb,Zn,Ni,Cd)were also determined and contamination indices(geoaccumulation index-Igeo,contamination factor-CF and degree of contamination-Cdegree)were used to evaluate the pollution status of studied material.Data obtained shows much higher content of organic carbon in soils(up to 7.82%)in comparison with cryoconite(max.1.63%)due to presence of vegetation,however,the basal respiration values in some cases were similar betweenсryoconite and soils,indicating high rates of microbial activity in a cryoconite holes.It was found that almost all materials studied have sandy structure.Cryoconite sediments on both of the glaciers are enriched with phosphorus,high values of K_(2)O(max.298 mg·kg^(-1))and N-NH4(max.247 mg·kg^(-1))are identified at Garabashi glacier which could be influenced by long-distant transfer but mostly a result of local anthropogenic activity.In case of trace elements,the highest content is identified for Zn(62 mg·kg^(-1) for cryoconite and 60.5 mg·kg^(-1) for soils)and the most contaminated materials are cryoconite from Garabashi glacier and Entisols,up to moderate level,which is mostly associated with local anthropogenic activity.

Genesis and Classification of Some Soils of the River Nile Terraces: A Case Study of Khartoum North, Sudan

Soils developed in the alluvium terraces of the River Nile at Khartoum North, Sudan was analyzed in an attempt to classify it as well as to refer them to their origin. Three river terraces comprising nine profiles were selected to cover the physiographic positions. Lack of B horizon and carbonate accumulation were main pedogenic processes in subsurface horizons, whereas orhric epipedon was developed on top soil surface. The microscopic inspection of heavy sand mineralogy indicated that the origin of the sand was the Ethiopian plateau. The most abundant clay mineral was smectite, followed by illite, kaolinite and chlorite. The presences of micas (illite) and chlorite in all studied soil samples might emphasize that these soils were young from the pedological viewpoint and less weathered. The soils of the River Nile terraces at Khartoum North were classified into: Typic Torrifluvents (1st terrace), Entic Haplocambids (2nd terrace) and Typic Haplocambids (3rd terrace). Mineralogy analysis indicated that the Entisols and Aridisols of the River Nile terraces in the study area had the same origin that of the igneous and metamorphic rocks from Ethiopian plateau.