ISSN 0016-7029, Geochemistry International, 2019, Vol. 57, No. 13, pp. 1361–1454. © Pleiades Publishing, Ltd., 2019. Material Composition and Geochemical Characteristics of Technogenic River Silts E. P. Yanin* Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] Received May 20, 2019; revised June 7, 2019; accepted June 7, 2019 Abstract—The paper discusses the results of many years of studying the material composition and geochem- ical characteristics, conditions, and processes in the formation of technogenic river silts: a new type of mod- ern river sediments formed in riverbeds within the boundaries and zones of influence of industrial–urbanized areas. The article examines the main sources and most important characteristics of technogenic sedimentary material flowing into rivers, as well as the geochemical conditions of technogenic alluvial sedimentation, the morphology and structure of technogenic silts, the extent of their spatial distribution in riverbeds, their grain size characteristics, and mineral and chemical composition. Special attention is paid to analyzing the group composition of organic matter in river sediments and the features of its transformation in pollution zones. The study analyzes the technogenic geochemical associations that form in silts in zones of influence of various impact sources, the features of the concentration and distribution of chemical elements, heavy metal specia- tion, the composition of exchangeable cations in technogenic silts and natural (background) alluvium, and the composition of silt water. Possible secondary transformations of technogenic silts and their significance as a long-term source of pollution of the water mass and hydrobionts are substantiated. Keywords: alluvium, sedimentary material, river, river channel, technogenic silt, city, pollution source, geo- chemistry, material composition, chemical elements, heavy metals, speciation, geochemical anomaly DOI: 10.1134/S0016702919130020 INTRODUCTION eral background that predetermines the lithological, mineralogical, and geochemical characteristics of allu- Sedimentogenesis, i.e., the formation of loose sedi- vial sediments. The end result of the concomitant ments, is rightly regarded as the most important process impact of these processes, manifested in the accumula- in the natural dynamics of the Earth’s surface. It is tion of alluvium, also depends on the hydrological manifested on the entire surface of our planet and in regime of watercourses, which in turn is governed by the fact is a global geochemical process associated with dif- interacting factors that directly or indirectly influence ferentiation of sedimentary material and migration of river runoff. Mechanical differentiation and fraction- chemical elements. The characteristics of the end prod- ation of solid phases, the physicochemical parameters ucts of sedimentogenesis largely depend on the input of the alluvial sedimentation setting, and processes that sources, the material composition of the material determine the behavior of chemical elements in the involved in sedimentation, and the geochemical condi- water column and bottom sediments, as well as seasonal tions of the sedimentation setting. In the general sedi- changes in the hydrological regime of the river, water mentogenesis scheme, two successive stages are distin- flow hydraulics, and the degree of saturation of its sed- guished: (1) catchment-area (slope–valley–delta) and imentary material—all of these are particularly import- (2) basin sedimentogenesis (Strakhov, 1983). One of ant for the material composition of alluvium and its the products that forms at the first stage is alluvium, i.e., subsequent transformation. Usually, under natural con- sediments that accumulate in river channels and valleys ditions, there is a certain sedimentary material balance and the floodplains and terraces making them up. in catchment area–riverbed and erosion–transport– Under natural conditions, the formation of alluvium accumulation systems. is controlled by the nature and intensity of erosion and In industrial–urbanized areas (in technogenic removal of soil and rock and the transport and deposi- landscapes), considerable masses of material are tion of sedimentary material by watercourses, all of involved in alluvial sedimentogenesis, the occurrence which act as an erosion–accumulation complex (Mak- of which in the sedimentary cycle is related to human kaveev and Chalov, 1986). The geological structure and economic activity and is characterized by a specific vegetative–soil cover of catchment areas create the gen- material composition and high concentrations of 1361 1362 YANIN speciation, the composition of exchangeable cations in technogenic silts and natural alluvium, and the com- Verbilki position of silt water. Possible secondary transforma- N tions of technogenic silts and their significance as a Vysokovsk Dmitrov Lotoshino Klin long-term source of pollution of the water mass and hydrobionts are substantiated. Volokolamsk Lake Senezhskoe Katuar The author is grateful to his teacher, doctor of geol- Shchelkovo ogy–mineralogy Yu.E. Saet (1934–1988), at whose Lake Glubokoe Obukhovo Moscow initiative and under whose leadership studies of the Moscow R. Kosinskie Lakes I processes and products of technogenic alluvial sedi- mentogenesis were begun in 1978. The author is par- Vereya Podolsk Khorlovo ticularly grateful to Academician E.M. Galimov for Voskresensk II valuable comments and friendly support in preparing Kolomna Karasevo the work for publication. Oka R. Zaraysk Kamira BRIEF DESCRIPTION OF THE MAIN AREAS AND RESEARCH METHODS Expeditionary studies, the results of which form the basis of this work, were carried out in different years within Moscow oblast (Moscow region), the Republic Fig. 1. Sketch map of Moscow region (not to scale): I, back- of Mordovia (Mordovia region), and central Kazakh- ground area; II, Pakhra River basin. stan (Kazakhstan region). These regions are character- ized, on the one hand, by a high degree of economic development, and on the other, their borders contain many chemical elements and compounds (Yanin, territories not directly affected by technogenesis. This 2002a, 2007b, 2018). This ultimately disrupts the made it possible to obtain material reflecting the differ- above-mentioned sedimentary material balance and ent intensities of technogenic impact on water systems leads to the formation of a new type of sediment in riv- and study a number of situations unique from the eco- erbeds: technogenic silts, which differ from natural logical and geochemical aspect, largely due to active channel alluvium in morphological appearance, technogenic alluvial sedimentation. material composition, physicochemical properties, and geochemical characteristics (Yanin, 1994, 2013a, Within the Moscow region, field studies were car- 2018). In most cases, it is the intensity and scale of ried out in the Pakhra River basin (the Pakhra proper technogenic alluvial sedimentation, the main material and nearly all of its tributaries), on rivers (Moscow, product of which is technogenic silts, that determine Klyazma, Vokhonka, Lavrovka, Lama, Vyaz, Protva, the most important ecological and geochemical fea- Osyotr, Sestra, Istra, etc.), and large streams in the tures of rivers in developed areas. zones of influence of various cities and towns (Mos- cow, Shchelkovo, Noginsk, Elektrostal, Obukhovo, The proposed work is based on materials and data Kolomna, Dmitrov, Voskresensk, Volokolamsk, obtained by the author in 1978–2018 in different Vereya, Khorlovo, Zaraysk, Lotoshino, Katuar, Kara- regions of the former Soviet Union and contemporary sevo, Klin, etc.), and on lakes (Glubokoe, Senezhs- Russia while carrying out scientific and applied hydro- koe, Kosinskoe) (Fig. 1). The most detailed studies chemical, ecological, and geochemical studies, as well were carried out within the typical small Pakhra River as scientific and problem-oriented prospecting, engi- basin, a right tributary of the Moscow River (Resursy…, neering, and environmental surveys. The article con- 1973a). The length of the Pakhra is 135 km, and the siders the main sources and the most important char- catchment area is 2720 km2. acteristics of technogenic sedimentary material flow- ing into rivers, as well as the geochemical conditions of The materials of the geological survey indicate that technogenic alluvial sedimentation, the morphology the rocks that have the main influence on local land- and structure of technogenic silts, the extent of their scapes are characterized by relative depletion of the spatial distribution in river channels, the grain size mineral composition and the content of most chemical characteristics, and mineral and chemical composi- elements within their global distribution parameters in tion. Special attention is paid to analyzing the group the lithosphere and sedimentary rocks. The main type composition of organic matter in river sediments and of relief in interfluvial spaces is loamy moraine plain, the features of its transformation in pollution zones. dissected by an erosion network of gullies and ravines. The study analyzes the technogenic geochemical asso- Up to 50% of the Pakhra catchment area is covered with ciations that form in silts in zones of influence of var- mixed forests on soddy-podzolic soil. ious impact sources, the features of the concentration The hydrological regime and water content of the and distribution of chemical