Geochemical features of the distribution of major and trace elements in sediments and soils of the Zarafshon River Valley

Purpose The aim of this research was to estimate impact of the geochemical features to distribution of major and trace elements in soil and sediments, assess of anthropogenic and natural factors in terrestrial ecosystems of Zarafshon. As well as to answer the common criticism of the water, soil and sediment pollution in Zarafshon. In this way this research will be reasonable substantial information about distribution of major and trace elements in mountains and piedmont regions.


Introduction
Page 3/27 The Zarafshon River rises in a homonym glacier, at an altitude of 2775 m at the junction of Turkestan and Zarafshon ranges (Prokhorov, 1969(Prokhorov, -1978. The initial part of the river, about 300 km long, lies in a narrow and deep valley. On the southern left bank, owing between Turkestan and Zarafshon ranges, it receives Fondarya, Arthuch (Kshtut) and Mogiyon, as well as many small tributaries (Prokhorov, 1969-1978, Panjakent, 1989, Urgut, 1989. After the city of Panjakent, the river follows a at region and crosses, the Tajikistan-Uzbekistan border (Urgut, 1989) passes the city of Samarkand and Bukhara and nally, it is lost in the desert in the vicinity of the city of Karakul without reaching the Amu Darya river whose formerly it was a major tributary (Sadikov et al. 1979).
The Zarafshon catchment basin, with an area of 17700 km 2 covers diverse geological formations which are spread from the alpine zone 3200-3500 m above sea level to less than 150 m westward the city of Karakul, where the Zarafshon river disappears in the vicinity of Kyzylkum desert. In the Zarafshon mountain gorges, below 1500 m there are small areas of semi-savannahs as well as mountain-forests.
Here, the sierozem is prevalent (Geoportal, 2020), while in the western sector of Zarafshon valley, loess deposits reaching a thickness of 100 m are common. In mountain gorges terraces of alluvial deposits and out ow cones of lateral tributaries serve as the basis for soil components. However, in some areas, due to the geographical features and diversity of rock formation, a thin layer of soil cover was formed.
For this reason, these places could be considered highly arid zones while sandstone generated by weathering of surrounding rocks represents the major components of soil.
The "Zarafshon" which in Farsi means "spreader of gold" re ects the existence of ore elds along the river valley. These together with other outcrops of nonferrous ores makes the eastern valley as well as its tributaries a mineral rich province which requires detailed investigation. Moreover, until present there are no systematic studies concerning the geochemistry of the Tajik section of Zarafshon Valley. This investigation could provide more data evidencing the origin of clastic material which compose the recent sediments as well as the interrelation between them and adjacent soil. For this reason, the distribution of major and rock-forming elements as well as of incompatible lithophile elements such as Sc, Ti, V, Cr, Zr, lanthanides Th or more soluble U together with siderophile Co and Ni showed to be very useful in inferring the nature of source rocks (Bhatia and Crook, 1986, Taylor and McLennan, 1991, McLennan et al., 1993, Armstrong-Altrin, 2009).
To accomplish this project, in the period of spring-autumn 2018 the Institute of Water Problems, Hydropower and Ecology of the Academy of Science of Tajikistan organized a eld expedition to collect the most representative samples of sediments and soils from the Tajik sector of Zarafshon catching basin. The samples were collected along the Zarafshon River, its main tributaries, as well as lakes and mine adits located on their upper reaches (Fig. 1). This permitted collection of 116 samples of sediments as well as an equal number of soil samples which further were analysed at the Neutron Activation Analysis Section of the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR), Dubna, Russian Federation. To determine the mass fractions of all above mentioned elements in sediments and soil samples, we have used the Instrumental Neutron Activation Analysis (INAA), in both thermal and epithermal neutron variants (Zeisler et al., 2011, Frontasyeva, 2011. The INAA permits determining the mass fractions of about 40 elements with a sensitivity of about 1 mg/kg without any preliminary chemical processing of samples such as acid digestion. The results of this project will be further presented and discussed.

The Geochemical Features Of The Investigated Regions
When studying the distribution of major and trace elements in soils and sediments it is important to take into account the in uence of parent rocks, mineralization and geochemical parameters of the studied objects. Since the Zarafshon River and its sub-basins originate from the high mountains glaciers and wash away the soils and minerals of rocks on their way. Therefore, it is very important to take this factor into account both in studying the geochemical features of the distribution of major and trace elements by waterways and during the ecological assessing of the investigated region. By addition, depending on the biogeochemical and physical processes, the distribution and accumulation of major and trace elements occurs in different ways. Due to its location between two important mountain ranges -Turkestan and Zarafshon, the Zarafshon catchments basin covers a great diversity of geological formation whose clastic material represents the main component of its sediments and of bordering soils.
The Djidjikrut River owing in the Ayni district with an area of 112 km 2 and 17 km long is a left tributary of the Yagnob River and falls into it in 9.4th km from the estuary of the river. According to the reference book "Surface Water Resources of the USSR' ' (1971), the Djidjikrut ows among rocks such as carbonates, clays, marls, limestones, dolomites and salts, which are strongly affect to the elemental composition of waters and sediments of the river. And the chemical composition of bank soil is also strongly associated with these rocks. In addition, at the estuary of the river within the eponymous ore eld is located the Djidjikrut deposit, relating to Zarafshan-Gissar mercury-antimony belt with folded carbonate and terrigenous formations of the Middle and Upper Paleozoic. The main ore minerals in this deposits are antimonite (Sb 2 S 3 with an admixture of As, Bi, Pb, Fe, Cu, Au, and Ag), and cinnabar (α-HgS), and metacinnabarite (β-HgS), pyrite (FeS 2 with an admixture of Co, Ni, As, Cu, Au Se), marcasite (FeS 2 with an admixture of As, Sb, Co, Ta, Bi, Cu), realgar (AsS), orpiment (As 2 S 3 ), sphalerite (ZnS), hematite (Fe 2 S 3 ).
The main components of the ores are antimony and mercury (in a ratio of 100: 1), but the presence of thallium, selenium, tellurium and arsenic has been established.
At present, at the con uence of the Djidjikrut and Yagnob on the northern slope of the Gissar range is operating the Anzob mining and processing plant (Geoportal, 2020) specializing on the underground mining of ores with the nal release of Hg-Sb concentrate. Sb and Hg rich ore fractions are separated by a lead nitrate otation which may be signi cantly contaminates sediment and soil in the downstream of the river.
The Yagnob River ows westward through the narrow mountain gorge along the southern edge of the Zarafshon mountains being the rst tributary of the Fondarya River. The total length of the Yagnob River is 114 km, and its basin area is 1660 km 2 . The mineral composition in the upper reaches of the Yagnob River is poorly studied. It should be noted that the Fon-Yagnob coal deposit is located downstream occupying almost the entire left-bank site between Djidjikrut and Pasrud tributaries. In this territory in the Kuhi Malik tract on the Fon-Yagnob coal deposit, located in the valley of the Yagnob river due to exothermic oxidation of sul des-containing compounds of the near surface coal layers (mainly pyrite and marcasite) a self-ignition process take place. The coal deposit occupies almost the entire left-bank part of the Yagnob river valley between its tributaries Djidjikrut and Pasrud.
Recently, is not excluded a certain role of a human in the emergence of new foci of ignition due to the development of coal seams. According by research work devoted to the mineralogy of one of paralavas, which is the highest-temperature formation of a coal re in the Kuhi-Malik tract it was revealed that they are products of complete melting sedimentary rocks enclosing coal seams (Sharygin, et al., 2009). The paralava contains such rocks like fayalite (Fe 2 SiO 4 ), sekaninaite (Fe 2+ , Mg) 2 Al 3 [AlSi 5 O 18 ] with an admixture of Ti, Mn, Ca, Na, K), hercynite (FeAl 2 O 4 ), Ti-magnetite, as well as minerals belonging to the silicas -tridymite (SiO 2 )and sour glass. Also the globules of sul des (mainly pyrrhotite), Fe-Ti-oxides, and greenalite (Fe 2+ , Fe 3+ ) 2−3 Si 2 O 5 (OH) 4 were identi ed. In addition, in the locally present hematites (Fe 2 O 3 ) and low-calcium pyroxenes (clinoferrosilite -Fe 2+ SiO 3 ) contains the high concentrations of Al 2 O 3 and MnO (4.5-5.8 and 0.6-0.8 wt%, respectively) and low concentrations of CaO, TiO 2 , and Na 2 O (< 0.25 wt%). In coal re formation paralava, besides the product of complete melting of rocks and coal seams were identi ed a native Se. (Novikov., 1986, Belakovsky., et al., 1988, Sharygin et.al., 2009, Mirakovet al., 2017, Nasdala L., et al., 1993. Also, the underground coal re may contribute to diagenesis of some REE minerals such as godovikovite, efremovit, maskanite and so on.
The Fondarya River with a signi cant catchment basin of 3230 km 2 is formed by the con uence of the Yagnob and Iskandardarya which crosses the Zarafshon ridge and ows into the Zarafshon River. In addition, the Fondarya is fed by the waters of the Sarvoda River which originates from the Alovdin lakes, as well as the lower and upper Kumarg tributaries, Chore and Pete.
It should be noted that in the upper ows of the Iskandardarya River operates the mining and processing plant "Tolko-Gold", which extracts and processes Au,Ag, Hg, Sb ore as well as uorite. Also the operation is carried out at the gold deposit in the Kumargi Bolo gorge. The Chore gorge (Chore river gorge) are classi ed as gold-quartz deposits and it is a gold ore deposit at the Turkestan-Chore ore zones of Central Tajikistan (Madzhidov B., 2017). This deposit was discovered in 1960, and during 1974-1984 a detailed exploration was carried out within drilling of wells and adits at seven horizons a depth of 500-600 meters. In the Chore gorge are widespread carbonate-terrigenous deposits and rocks of granitoid magmatism are quite rare. In addition to pyrite and arsenopyrite which constitute more than 95% of all ore minerals, also occur antimonites, chalcopyrite, sphalerite, pyrrhotite, and others [Novozhilov Yu.I. et al.1999].
The Pete tributary ows between the Pete-Takfon ore eld representing Takfon, Pete, Simich and other deposits. In the geological structure of the ore eld Paleozoic formations are widely developed, which are represented by Silurian (shales, limestones, dolomites with interlayers of quartzites), Devonian (siliceous and micaceous shales with interlayers of cherts and limestones) and Carboniferous (limestones with horizons of clay shales, sandstones) and Cong deposits. To the south of the ore eld area the complex of Paleozoic formations is overlapped by sub-platform sediments of the Mesozoic. The Igneous formations are represented by the Pete intrusions of granodiorites, dikes of granodiorite-porphyry and lamprophyres.
There are also tin and silver, lead and zinc-containing ores ).
At its turn, the Mogiyon River with a length of 68 km and a basin area of 1100 km 2 is one of the largest Zarafshon tributaries. From the source to the village of Mogin in a narrow valley, the river ows in a northern direction, cutting through the Zarafshon ridge with a deep transverse gorge. Further, having received its largest tributary -the Shing River, it continues to ow in a narrow rapids channel with a width of up to 10 m. Nine kilometers above the city of Panjakent, leaving the gorge and passing through the village of Sujina falls into the Zarafshon River. Between the Shing and Mogiyon inter uve is located the Taror ore eld, belonging to the Western Zarafshon-Gissar metallogenic zone (Blokhina, 1984). However, along with gold-sulphide mineralization, silver-tin-base metal mineralization, localized in its upper and middle horizons is also developed. The silver deposit in the Taror ore eld belongs to the Mirkhant deposit and its mineralization is predominantly represented by a silver-tin-polymetallic association spatially combined with sulphide showing the closest correlation between Ag and Sb . It is worth noting that in the Tarror gold ore deposit operates the Joint Venture "Zarafshon" whose main product consists of Ag-Au alloy (Solihov, 2018).
In the valley of the Zarafshon River and around its tributaries is quite developed the mining and metallurgical industry, based on the extraction and processing of non-ferrous metals. The main metallurgical industries could be listed as including the Anzob mining and processing plant (AMPP) and Taror gold ore plant (TGOP). Recently, work has been carried out at the Upper Kumarg and Kanchoch elds. AGOK specializes in the production of antimony-mercury concentrates, TGOP in the production of gold.
In this regard, the investigated regions are the object of controversy between scientists and environmental experts from governmental and non-governmental organizations. The activities of industrial enterprises are often criticized which is the main goal of this research. Since, disregarding the geochemical features of a particular region, it is not entirely correct to assess their ecological state. So that authors decided to analyse the unexposed and exposed to anthropogenic impacts sediments and soil samples and compare the obtained data between it.

Samples
An equal number of 116 sediment and soil samples were collected in the investigated area, using an AMS 12 Multi Stage Sediment Sampler equipped with tubular glass sampler (AFMS Inc. American Falls, ID).
Unconsolidated columns of sediment, 20 to 30 cm long, were handpicked from the riverbeds during a high-water period. From each sampling point, three sub-samples covering an area of about 10m 2 were collected and carefully mixed to form a composite sample. Any possible recent contamination was avoided by removing the top layers of soil and sediment columns and by washing the glass sampler with acid before any sampling.
To highlight a possible local human in uence, sampling zones were divided into two parts: -i. A number of unexposed 91 sediments and 92 soil samples were collected directly on the banks of the lakes, rivers and mountain tributaries with no human activities. -ii. Opposite these, 25 sediments and 24 soil samples were collected around the road tunnels, near the industrial zones, coal mining, mines and adits, some of still under exploration ( Fig. 1 ((b)), Table S1 and Table S2).
Samples consisting of silty greyish sand without organic detritus were placed into the plastic container with cooled refrigerant and kept at a 4 0 C. In the laboratory, all samples were again cleaned from alien materials and dried at 70 0 C at constant weight and ground. Finally, the dried material was sieved using a 0.425 mm (42 mesh) sieve, homogenized and sent to the Frank Laboratory of Neutron Physics (FLNP) of Joint Institute for Nuclear Research (JINR) for further Instrumental Neutron Activation Analysis (INAA).
Here, 10 g of each sample were homogenized again for 15 min in a planetary ball mill (PULVERISETTE 6, Fritsch Laboratory Instruments GmbH, Germany) at 400 rpm. To increase the precision and accuracy of measurements, six aliquots of about 0.3 g were selected from each sample and independently analysed.

INAA measurements
For INAA, before irradiation at the IBR-2 reactor of the JINR FLNP in Dubna, each aliquot was packed in polyethylene bags for the determination of short-living isotopes (three aliquots) and in aluminium foil (three aliquots) for long-living ones. It is worth mentioning that the mass fractions of short-living isotopes were determined by thermal neutron activation while in the case of long-living isotopes we have used epithermal neutrons. More details concerning irradiation time and neutron ux densities in each irradiation channel can be found in ).
The gamma spectra of each sample were measured with an HPGe detector with a resolution of 1.9 keV for the 60 Co 1332 keV line, analysed using the Canberra software Genie 2000 and processed by using a proprietary (Pavlov et al. 2016). By means of this software, the mass fractions of each element together with the associated Combined Standard Uncertainty (CSU) (Farrance and Frenke, 2012) were calculated. It is worth mentioning that the CSU was estimated by taking into account the statistical error, in uence of measurement geometry, detector e ciency, the content as well the error of each element for all Certi ed Standard Material (CSM) utilized for calibration. To avoid any environmental contamination, all resulting radioactive materials were deposited in a permanent low activity repository.

Quality control
The quality control was assured in the case of sediments and soils by a simultaneous analysis of Standard Reference Materials (SRM) provided by the National Institute for Standard and Technologies (NIST), i.e. 1633c Coal y ash, 667 Estuarine sediment, 2710 Montana Soil and 1547 Peach leaves for short half-life time isotopes. In the case of long life-time isotopes in sediments, the best results were obtained by using -SRM − 2709 Trace elements in soil, SRM-1632c Trace elements in coal, SRM-690CC Calcareous soil and SRM − 2709a San Joaquin soil, SRM-1632c Trace elements in coal and SRM-AGV2 Andesite in the case of soil samples.
Further, by using all the above-mentioned SRM it was realized a Group of Standard Sample (GSS) which were irradiated together with the investigated samples permitting in this way to calculate the mass fractions of about 40 elements. This was done by proprietary software which, besides determining the mass fractions of chosen elements, checked to which extent the mass concentration of CRM corresponds to certi ed ones (Pavlov et al. 2016, Zinicovscaia et al. 2018. Following this procedure, the accuracy quanti ed by means of standard deviation corresponding to each group of three aliquots was lower than 10%. In the case of SRM, the CSU varied between 3 and 26%, higher in the case of REE. In our opinion, the observed discrepancy was due not to the experimental conditions of measurements, but to the fact that only in a few cases, the SRM provides certi ed values instead of recommended ones whose interval of uncertainty was signi cantly higher. Regardless of these remarks, the CSU was never greater than 20%.

Results And Discussion
The complete data concerning the content of 38 elements in 116 soil and sediment samples can be found in Mendeley repository , while in Table 1 reproduced only the average values of mass fractions of these elements together with corresponding values of the Upper Continental Crust (UCC), (Rudnick and Gao, 2003), North American Shale Composite (NASC) (Gromet et al. 1984), Post Archaean Australian Shale (PAAS), (Taylor and McLennan, 1991), Average Earth Crust (AEC) (Vinogradov, 1961), Suspended Matter of the World's Rivers (SMWR), (Savenko, 2007), as well as Average World Suspended Sediment (AWSS) (Viers et al., 2009). Table 1 The mass fraction of investigated elements in sediments and soil with the main literature references: UCC (Rudnick and Gao, 2004), NASC (Gromet et al., 1984), PAAS (Taylor and McLennan, 1991), Average Earth Crust (AEC) (Vinogradov, 1961), SMWR (Savenko, 2007), AWSS (Viers et al., 2009 In this regard, in (Fig. 2) was illustrated by means of box and whiskers diagrams the mass fractions of investigated elements in soils and sediments normalized to the UCC (Rudnick and Gao, 2004) and SMWR (Savenko, 2007) respectively. The UCC (Rudnick and Gao, 2004) was chosen as one of the best descriptors of the most accessible portion of the continental crust. A choice of SMWR (Savenko, 2007) to normalize sediments are drawing on the theory of lithogenesis (Strakhov, 1960). According to the theory of lithogenesis the mobilization of suspended and dissolved materials in drainage basins are the initial stage of the formation of sedimentary rocks. The major portion of chemical elements are transported by the river suspensions, including alkaline and calc-alkaline metals, which are highly mobile in the supergene zone. Indeed, other descriptors such as NASC (Gromet et al. 1984), AWSS (Viers et al. 2009) or Post Achaean Australian Shale (PAAS) (Taylor and McLennan, 1991) showed to be almost identical.
When the compositional interpreting data of the elemental content of river sediment and soil their geochemical features should be taken into account, which is determined in a great measure by the geochemistry of local geological formations. Therefore, due to sediment mobility various mineral fractions are mixed and deposited depending on water speed, grain sizes and speci c gravity.
According to (Fig. 2) from the point of view of mass fraction the investigated soils and sediments shows both major and trace elements and excepting chalcophile Zn, As, Sb ad Hg, are closer to UCC (Rudnick and Gao, 2003) and SMWR (Savenko, 2007). Moreover, at more careful analysis of mass fraction data, reproduced in (Table 1S and 2S), the content of As, Sb and Hg showed higher mass fractions only in few sediment and soils samples collected in the vicinity of mines and adits located on Djidjikrut, Kanchoch, Chore and Mogiyon tributaries (Fig. 1).
In spite of these small inconsistencies, the elemental content of sediment and soils showed to be relatively closer as Spearman's correlation coe cient of 0.83 suggests (Fig. 3). As sediment and soil samples were collected from the same locations, this fact suggests also that sediments represent in a greater measure the basic component of soil.

Major elements
The average values of the mass fractions of major, rock-forming elements excepting MgO and CaO showed to be relatively closer to UCC (Rudnick and Gao, (2004), to the other sedimentary system and even to AEC (Vinogradov, 1961). It should be also remarked that silica represents the main major constituent of all investigated samples, its mass fraction varying around 62.8 ± 11.9% percent in the case of sediments and 59.4 ± 8.8% in the case of soils. Represented on total alkali-silica discriminating diagrams SiO 2 -Al 2 O 3 -Na 2 O + K 2 O + CaO and SiO 2 -Na 2 O + K 2 O the composition of investigated materials suggests a rather felsic to the intermediate origin with small contribution of ma c material, as the case of Pete intrusion mentioned before this one of granodiorites, dikes of granodiorite porphyries and lamprophyres. Its average mass fraction is closer to the UCC (Rudnick and Gao, 2004) but with only a few exceptions in the sediments collected in the vicinity of Anzob tunnel, Sarvoda 1 and Sarvoda 2 as well as soils from Chore1 and 3, Djidjikrut 1, Obi Sara 1, Saritag 2, as well as Sarvoda 1 to Sarvoda 7. In all these points, the lower content of silica was due to an increased content of calcium oxide whose mass fractions varied between 26 and 47%.
With respect to UCC the aluminium oxide Al 2 O 3 showed in sediment an average mass fraction 9.91 ± 3.2%, lower than the soils one of 12.92 ± 3.7%, both of them lower than the UCC (Rudnick and Gao, 2004) and NASC (Gromet et al. 1994) ones of 15.4 and 16.96% respectively and probably due to low content of plagioclase. In its turn, the sodium oxide Na 2 O has an average mass fraction in sediments and especially in soils smaller than the corresponding UCC (Rudnick and Gao, 2004), suggesting a low content of albite, and by consequence predominance of a sedimentary substrate (Fig. 4 ((a ,b)). This nding is con rmed by the discriminating ternary diagram reproduced in (Fig. 4 ((b)), the points corresponding to sediment and soils are grouped around UCC (Rudnick and Gao, 2004) and NASC (Gromet et al., 1984). Here, some points are shifted towards lower SiO 2 content, which could be due to an increased content of CaO, whose mass fraction in some places reached 28 % (Table 1S and 2S).
The third discriminating diagram, the ternary K-A-CN one, evidenced a clear in uence of weathering on both sediment and soils (Fig. 4 ((c)). Here the increased fraction of CaO can be remarked on the lower left corner of the diagram. In this regard, it is an interest to remark that, according to the tables of Spearman's correlation coe cients (Table 2), CaO correlates positively only with MgO in sediment as well as in soils. The most plausible, this could be explained by the presence of dolomite where CaO mass fraction signi cantly overpass the UCC (Rudnick and Gao, 2004) one. On the other hand, the signi cant variability of the rest of the major elements could be explained by the fact that both sediment and soils were collected along about 600 km of Zarafshon Valley and its tributaries, at altitudes varying between 883 and 3629 m. Therefore, the sampling points cover a signi cant diversity of geological formations with different geochemistry (see the previous Geochemistry section). The mass fractions of the oxides of other major elements, i.e. TiO 2 , FeO, and MnO were closer to the UCC (Rudnick and Gao, 2004) ones in conformity with the previous remarks concerning a rather felsic origin of both sediment and soils (Table 1).

Trace Elements
More data concerning the origin of investigated sedimentary materials can be inferred by analysing the distribution of trace elements and especially those considered incompatible and insoluble. The same kind of analysis could reveal a possible anthropogenic in uence in particular concerning mines and quarries of mineral resources such as non-ferrous minerals or building material.
In the rst case, using by geochemical indexes for low mobility and incompatible trace elements such as Sc, Zr, La, Ce, Nd, Sm, Eu, Gd, Tm, Yb as well as Th and U (Bhatia and Crook, 1986, Taylor and McLennan, 1991, Wang et al., 2012 the geochemical features of sediment and soils were characterized. Also, in the case of possible anthropogenic contamination V, Cr, Ni, Zn, As, Sb and Hg showed to be the most appropriate. Notably, the felsic rocks are richer in Th and light REE, whereas ma c rocks contain more Sc, Cr, Co, Ni and an increased fraction of heavy REE. In this regard, the Sc whose average mass fraction is less than 20 mg/kg in felsic rocks but increases to 20-40 mg/kg in ma c ones, (Norman and Haskin 1968) has proven to be one of the most appropriate discriminating elements. In the case of our investigated sediment and soils the Sc mass fractions were 9.56 ± 4 and 11.4 ± 4.6 mg/kg respectively and con rming the previous inference concerning the felsic origin of sedimentary material in Zarafshon Valley. On this reason, there are different discriminating diagrams able to evidence the sedimentary provenance or the source of rock compositions (Armstrong at al., 2013).
Accordingly, discriminating ternary Sc-La-Th diagram (Fig. 5 ((a)) and Th/Co vs La/Sc bi-plot (Cullers, 2002) (Fig. 5 ((b)) suggests that analysed samples are closer to acidic than to basic rocks, supporting the hypothesis of felsic nature of the source some with possible traces of the basic rocks as well. At the same time, most experimental data of sediment and soil on both diagrams are distributed around UCC (Rudnick and Gao, 2004) and NASC (Gromet et al. 1984).
Using the La/Th vs Hf diagram (Floyd and Leveridge, 1987) provides another discriminating useful evidence for the source material, because Hf has an increasing tendency to be enriched during the erosion of ancient (meta) sedimentary rocks. This peculiarity allows more detailed analysis of the sediment and soil source material along great investigated areas. With few exceptions the investigated sediment and soil presented to have a felsic origin con rming the previous inference based on distribution of major and trace elements for the same samples. Only the sediments and soils collected around Fondarya tributary, Kumargi poyon, Yangob and Chore estuary showed a mixed felsic/basic soured characterized by a higher a La/Th radio simultaneously with a reduced Hf mass fraction (Fig. 6 ((a)), Table 1S and 2S). On contrary, the increased mass fraction of Hf together with reduced values of La/Th ratio suggest the presence of old sediment sources in the Mastchohi kuhi, Shahriston and some regions of Panjekent (Fig. 6 ((a)), Table 1S and 2S).
Application aspects of the geochemical indexes can be extended using a Th/Sc versus Zr/Sc bivariate plot which characterized the hydraulic sorting and sedimentary recycling (McLennan, 1993). Whereas Th is incompatible in igneous systems and Sc is compatible in igneous systems (Lee et al. 2009). Therefore, the Th/Sc ratio is a good proxy for igneous chemical differentiation processes. Unlike Zr, which is strongly enriched due to the extreme resilience of zircon mineral to abrasion, Sc generally preserves a signature of provenance. This makes Zr/Sc ratio a useful index for Zr enrichment (McLennan et. al., 1993) (Fig. 6 ((b)). At a more detailed analysis the Th/Sc versus Zr/Sc curve presents two trends, i.e. the rst one, for a Th/Sc ration less than unity corresponds to a natural igneous differentiation which does not involve to Zr enrichment, and a second one, above this limit which characterizes Zr enrichment occurring during sedimentary sorting and recycling (McLennan et al. 1993, Nagarajan et al 2015. In the case of Zarafshon sediment and soils illustrates the Zr enrichment seems to be less signi cant suggesting a weak sorting process, in good correlation with the fresh nature of sedimentary material ( Fig. 6 ((b)).
REE represents a group of 17 elements, including 15 lanthanides, Sc and Y as well. In this regard, lanthanides play a special role in investigating the provenance of rocks, because all of them have closer chemical properties, but ionic radii monotonously decrease from La to Lu. Traditionally, lanthanides are classi ed in light lanthanide or light REE (LREE) -La to Sm and heavy REE (HREE) -from Eu to Lu. Moreover, REE are not easily fractionated during sedimentation so they keep the " ngerprints" of mother rocks making them helpful in establishing their origin. Moreover, the Eu which can exist in two valence states (Eu 2+ and Eu 3+ ) in its bivalent state, due to a smaller ionic radius can substitute by Sr 2+ ions in plagioclase feldspars. As this process takes place only in reduced conditions which can be found only in the superior mantle or lower crust and this leads to a distinct negative anomaly in rocks coming from the upper crust. Another lanthanide REE distinctive characteristic, useful in evidencing the rock origin is related to the asymmetry of LREE and HREE in felsic rocks being enriched in LREE with respect to ma c ones, depleted in this category of REE.
In its turn, the La/Th ratio could be useful in inferring the provenance of sedimentary material, by considering that for the UCC (Rudnick and Gao, 2004) and NASC (Gromet et al. 1984) this ratio is around 2.8 while in the case of average MORB (Gale et al. 2013) it is estimated between 7.2 and 15.6. In the case of Zarafshon the La/Th ratio for sediments and soils were closer to 3.23 ± 1and 3.03 ± 0.9 respectively, for a Spearman's correlation coe cient of 0.621at p < 0.01 and both of them closer to the UCC ratio of 2.96 (Rudnickand Gao, 2004) and of 2.53 for NASC (Gromet et al. 1984) (Fig. 7 ((a)).
Further analysis of the distribution function of the mass fraction of eight REE, i.e. La, Ce, Nd, Sm, Eu, Gd, Tb, Tm and Yb, showed to be closer to the UCC (Rudnick and Gao, 2004) one. The same peculiarity we have noticed in the case of La/Yb ratio, as well as concerning the Eu negative anomaly (Fig. 7 ((b)), Table 3). Table 3 The La/Yb and Eu* values for sediment, soils, and, for comparison, for UCC (Rudnick and Gao, 2004) and NASC (Gromet at al. 1986 The Th/U ratio represents another proxy useful in characterizing the investigated systems. In the case of Zarafshon sediment and soils, the Th/U ratio was equal to 3.01 ± 0.9 and 3.12 ± 1.1 respectively, comparable within one St.Dev, but smaller than 3.89 in the case of UCC (Rudnick and Gao, 2004) or 4.62 for NASC (Gromet et al. 1984). A possible explanation of this small discrepancy could be rather related to an increased U content whose average mass fraction varied between 3.04 ± 1.38 mg/kg in sediment and 3.8 ± 1.5 mg/kg in soils.
These results con rm once more the previous conclusion, which point toward a felsic origin of sedimentary martial, sustaining the hypotheses that sediments are the main material of the Zarfashon soils. On the other hand, it should be mentioned that, although the average values of all above mentioned ratios are closed to the UCC ones, the REE mass fractions showed a considerable spreading which could sustain the hypothesis of the prevalence of the felsic material, the other constituents from basaltic to rich silica rhyolite ( Fig. 4 ((b)).

Anthropogenic In uence
The assessment of ecological condition of investigated more details described on the second part of this research  which was previously published. As expected, the impact of anthropogenic sources was quite speci c in the case of As, Sb, Hg and at a lesser extent for Zn and V. In this regards it is worth mentioning that we have restrained our study only to elements considered as contaminants according to the most severe o cial regulations of the Tajikistan, Russian Federation (Anonymous, 1992) and Romania (Anonymous, 2020).
The most serious contamination we have noticed in the vicinity of Anzob ore-mining combine (Djidjikrut 1,2 and 7 sampling points) and Kanchoch mine adit (Supplementary Material). Here, the mass fractions of Zn, Hg and especially Sb were ten to a hundred times greater than the Russian Federation (Anonymous, 1992) and Romania (Anonymous, 2020) norms (Fig. 2, Table 1S and 2S). At the same time, we have noticed increased amounts of V, Cr and Ni, all of them related to mining and processing plants. This is the case of V whose mass fractions varied between 154 and 14500 mg/kg around Anzob mining and processing plant, Kumargi Bolo gold-mining combine, Chore 2 to Chore 4 adits or Shahriston tunnel.
In the last case, the shredded solid were scattered near the Shahriston tributary contaminating both soil and sediment along Shahriston tunnel.
The in uence of local geochemical features leads to increased mass fraction values of As, Sb, Hg, REE as well as Ta and natural radioactive elements Th and U. But these uctuations had a local character, mass fraction rarely exceeding the UCC ones (Rudnick and Gao, 2004) values.

Conclusion
The Instrumental Neutron Activation Analysis due to its ability to simultaneously determine the content of up to 40 elements, including rock-forming ones was used to investigate the distribution of 38 major and The signi cant information was obtained by analysing the distribution of low mobility and incompatible Sc, Zr, La, Ce, Nd, Sm, Eu, Gd, Tm, Yb as well as Th and U. The Sc presented an average mass fraction of 10 to 11 mg/kg which characterise for the felsic origin. This conclusion sustained also by the reciprocal distribution of Sc, Co, La and Th, La, Th and Hf, or Sc, La and Th which con rmed in different modes. The relative freshness of the sedimentary material was con rmed by the Th/Sc vs. Zr/Sc bi-plot which suggested the absence of a signi cant sorting and recycling of both sediment and soils.
Also, the felsic origin was con rmed by analyzing the distribution of eight REEs and an average value of La to Sm ratio (for LREE) and Gd to Yb (for HREE) are closer to UCC and NASC ones. The same peculiarity was observed in the case of negative Eu anomaly and showed to be closer to UCC for both sediments and soils.
For a possible anthropogenic contamination, the content of Zn, V, As, Sb and Hg showed to be the most appropriate. But in spite of pristine nature in the Zarafshon Valley in very few places with mining and non-ferrous ore factories were found which could be signi cantly polluting an environment with As, Sb and Hg. Even in unexposed (normal and uncontaminated) sediment and soils samples the content of As, Sb and Hg showed to be higher at levels exceeding tens to hundred times compared by reference materials, which evidence about geochemical features of investigated regions.
Given the surface of the investigated area, more than 15 000 km 2 as well as the diversity of geological formation still insu ciently explored and investigated, the presented results should be seen as an original data for further detailed exploration. CRediT authorship contribution statement Daler Abdusamadzoda: conceptualization, methodology, validation, formal analysis, investigation, data curation, roles/writing-original draft, writing-review and editing, visualization; Djamshed A. Abdushukurov: conceptualization, methodology, validation, data curation, visualization; Octavian G. Duliu: conceptualization, data curation, methodology, validation, investigation, resources, data curation, writing-review and editing, visualization; Inga Zinicovskaia:
Founding No funds, grants, or other support was received for conducting this research and the authors did not receive support from any organization for the submitted research.
Compliance with ethical standards Con ict of interest The authors declare that they have no con ict of interest.
Code availability Not applicable Consent to participate Field study was carried out on agreement of local authorities and all orally consented to performing this study. The study did not involve endangered or protected zone.  Discriminating total alkali metal oxides vs. SiO2 biplot (a), ternary SiO2-Al2O3-Na2O+K2O+CaO (b) and K-A-CN illustrating the preponderance of felsic material in Zarafshon sediment and soils as well as the signi cant presence of weathered material.

Figure 5
Discriminating bi-plot Th/Co vs. La/Sc (a) and ternary Sc-La-Th diagram (b) con rming the felsic origin of investigated sediment and soils. The La vs. Th bi-plot (a) proving that both Zarafshon sediment and soils are signi cantly closer to UCC (Rudnick and Gao, 2004) and NASC (Gromet et al. 21984) then to MORB (Allison et al., 1986) and the eight REE average values of Zarafshon sediment and soils normalized to chondrite together with the corresponding UCC data (b).