High Metal Content Research Articles

ANALISIS KANDUNGAN UNSUR DAN SENYAWA KIMIA PADA IKAN SAPU-SAPU (Pterygoplichthys pardalis) DI DANAU SIDENRENG

A Suckermouth catfish is one type of fish that is considered a pest in the waters because it is invasive (invasive species). In addition to being a pest species, Suckermouth catfish is also known as one type of fish species that has a fairly high heavy metal content in some waters that are classified as polluted waters. This research was conducted with the aim of knowing the content of chemical elements contained in Suckermouth catfish. Based on the results of XRF (X-Ray Fluoroscence) analysis, it shows that there are 14 chemical elements found in the organs of the broom fish, including Sulfur (S), Potassium (K), Calcium (Ca), Phosphorus (F), Silicon (Si). ), Chlorine (Cl), Iron (Fe), Zinc (Zn), Niobium (Nb), Molybdenum (Mo), Antimony (Sb), Ruthenium (Ru), Indium (In), Tin (Sn) and Titanium (Ti ). Meanwhile, based on the results of XRD (X-Ray Diffraction) analysis on the scales of the Suckermouth catfish, the micrograph results obtained in the form of an amorphous which is indicated by the presence of a hump on the graph consisting of 10% Cadmium Mercury, 81% Phosphorus and 9% Calcium, while in the bone Suckermouth catfish consists of 40% Calcium Hydride, 59% Akermanite, and 0.96% Cadmium.

Accurate Identification and Quantification of Chinese Yam Powder Adulteration Using Laser-Induced Breakdown Spectroscopy.

As a popular food, Chinese yam (CY) powder is widely used for healthy and commercial purposes. Detecting adulteration of CY powder has become essential. In this work, chemometric methods combined with laser-induced breakdown spectroscopy (LIBS) were developed for identification and quantification of CY powder adulteration. Pure powders (CY, rhizome of winged yam (RY) and cassava (CS)) and adulterated powders (CY adulterated with CS) were pressed into pellets to obtain LIBS spectra for identification and quantification experiments, respectively. After variable number optimization by principal component analysis and random forest (RF), the best model random forest-support vector machine (RF-SVM) decreased 48.57% of the input variables and improved the accuracy to 100% in identification. Following the better feature extraction method RF, the Gaussian process regression (GPR) method performed the best in the prediction of the adulteration rate, with a correlation coefficient of prediction (Rp2) of 0.9570 and a root-mean-square error of prediction (RMSEP) of 7.6243%. Besides, the variable importance of metal elements analyzed by RF revealed that Na and K were significant due to the high metabolic activity and maximum metal content of CY powder, respectively. These results demonstrated that chemometric methods combined with LIBS can identify and quantify CY powder adulteration accurately.

Trace metal accumulation in tissues of wedge clams from sandy habitats of the Bulgarian Black Sea coast

The aim of the present study was to carry out an initial screening of trace metals bioaccumulation in soft tissues of the wedge clam (Donax trunculus Linnaeus, 1758) from different localities of the Bulgarian Black Sea coastal area and to evaluate the bioindicator potential of this species. Wedge clams were collected in June and September 2020 from sublittoral sandy habitats at different localities of the Bulgarian Black Sea coast. Soft tissues of individual clams were digested with nitric acid followed by ICP-OES analytical determination. The content of trace metals in the wedge clams differed significantly amongst localities. Higher metal content was present in wedge clams from Sveti Vlas, Shkorpilovtsi, Slanchev Bryag, Ahtopol and Kranevo. The highest values of lead (Pb) (2.51 mg/kg) and cadmium (Cd) (0.32 mg/kg) were found in samples from Sveti Vlas and the highest concentration of copper (Cu) (34.12 mg/kg), iron (Fe) (269.52 mg/kg) and nickel (Ni) (0.32 mg/kg) were detected in wedge clams from Shkorpilovtzi. Maximum content of chromium (Cr) (0.58 mg/kg) was present in samples from Slanchev Bryag, together with high values of Fe. The highest concentration of zinc (Zn) (18.04 mg/kg) together with high values of Cr and Fe were measured in wedge clams from Irakli. In conclusion, the wedge clams from the localities known to have higher coastal inflows and touristic pressures, i.e. Varna, Shkorpilovtzi, Sveti Vlas, Slanchev Bryag and Ahtopol accumulated significantly higher metal elements in their tissues. Only few significant seasonal differences in the concentration of metal elements in wedge clams were present and the observed seasonal variations were probably connected to the hydrological parameters of the ecosystems. The wedge clam D. trunculus is a suitable bioindicator for assessment and monitoring of metal pollution in the Bulgarian Black Sea environment.

Preparation and characterization of fully waste-based glass-ceramics from incineration fly ash, waste glass and coal fly ash

Municipal solid waste incineration (MSWI) fly ash (FA) is a typical hazardous waste due to its high contents of toxic heavy metals, and hence its disposal has attracted global concern. In this work, it was recycled into environmental-friendly CaO–Al2O3–SiO2 system glass-ceramics via adding coal fly ash (CFA) and waste glass (WG). The effects of CaO/SiO2 ratios and sintering temperatures on the crystalline phases, morphologies, mechanical and chemical properties, heavy metals leaching and potential ecological risks of glass-ceramics were investigated. The results showed that wollastonite (CaSiO3), anorthite (CaAl2Si2O8) and gehlenite (Ca2Al2SiO7) were the dominant crystals in the glass-ceramics, which were not affected by CaO/SiO2 ratio and sintering temperature. The compressive strength increased, while the Vickers hardness and microhardness decreased as increasing the sintering temperatures from 850 to 1050 °C, which reached their maximum values of 660.69 MPa, 6.14 GPa, and 7.43 GPa, respectively. However, the increase of CaO/SiO2 ratio resulted into the reduction of the three mechanical parameters. As varying CaO/SiO2 ratio from 0.48 to 0.86, the maximum compressive strength, Vickers hardness and microhardness were 611.80 MPa, 5.43 GPa, and 6.56 GPa, respectively. Besides, all the glass-ceramics exhibited high alkali resistance of >97%. The extremely low heavy metals leaching concentrations and low potential ecological risk of glass-ceramics further revealed its environmentally friendly property and potential application feasibility.

Incorporation of bioleached sulfidic mine tailings in one-part alkali-activated blast furnace slag mortar

Sulfidic mine tailings are potential waste materials from mining and mineral processing, and they can contain a high content of sulfur and metal(loid)s, even after bioleaching. Due to the large amount of tailings waste from historical mining, it is crucial to find alternative methods for utilizing such waste rather than permanent storage in tailings impoundments. One-part alkali-activated slag mortars are promising co-binder systems for the recycling of sulfidic mine tailings thanks to their practicability, easy transportation, and user-friendly production. In this work, up to 50 wt% mine tailings were incorporated into alkali-activated blast furnace slag mortars. C-(N)-A-S-H gels were formed in all final samples with hydrotalcite zeolites. Tailings hardly participate in alkali activation, but they do have a considerable influence on physical and chemical properties. The 20 wt% tailings-containing sample showed the highest compressive strength of 91.1 MPa after 90 days of curing. The results of isothermal calorimetry indicate that incrementally increasing the percentage of tailings promotes the pre-induction reaction but hinders the slag hydration process. In addition, the results of X-ray microcomputed tomography showed higher porosity when the mortar contains more tailings; thus, the sample with 10 wt% mine tailings showed the lowest porosity. According to the European Union batch leaching test, up to 20 wt% bioleached sulfidic mine tailings can be valorized in a co-binder system while remaining below the nonhazardous waste thresholds.

Examining Metal Contents in Primary and Secondhand Aerosols Released by Electronic Cigarettes.

The usage of electronic cigarettes (ECs) has surged since their invention two decades ago. However, to date, the health effects of EC aerosol exposure are still not well understood because of insufficient data on the chemical composition of EC aerosols and the corresponding evidence of health risks upon exposure. Herein, we quantified the metals in primary and secondhand aerosols generated by three brands of ECs. By combining aerosol filter sampling and inductively coupled plasma mass spectrometry (ICP-MS), we assessed the mass of metals as a function of EC flavoring, nicotine concentration, device power, puff duration, and aging of the devices. The masses of Cr, Cu, Mn, Ni, Cu, and Zn were consistently high across all brands in the primary and secondhand aerosols, some of which were above the regulated maximum daily intake amount, especially for Cr and Ni with mass (nanograms per 10 puffs) emitted at 117 ± 54 and 50 ± 24 (JUUL), 125 ± 77 and 219 ± 203 (VOOPOO), and 33 ± 10 and 27 ± 2 (Vapor4Life). Our analysis indicates that the metals are predominantly released from the EC liquid, potentially through mechanisms such as bubble bursting or the vaporization of metal-organic compounds. High metal contents were also observed in simulated secondhand aerosols, generally 80-90% of those in primary aerosols. Our findings provide a more detailed understanding of the metal emission characteristics of EC for assessing its health effects and policymaking.

Separation of Mineral from Brown Algae Extract using Micro Filtration (MF) and Ultra Filtration (UF) Membrans – Review

Brown algae ( Phaeophyta ) contain active compounds such as carbohydrates, proteins, phenolics, fats, pigments, vitamins and minerals. The mineral content of brown algae is around 8% to 40% consisting of cations Na + , K + , Mg ++ , Fe ++ , Zn ++ , Mn ++ and heavy metals. Bioactive brown algae has many benefits, including Fucoidan as a cancer drug. The barrier of using Fucoidan as a medicine is its high mineral content. Therefore, the minerals must be separated. The extraction process of brown algae using various methods has been carried out with the aim of isolating the active component of Fucoidan that is free from minerals that will be an obstacle in utilizing the active component. This paper will describe some of the latest methods of extracting the active ingredients of brown algae and mineral separation processes using Micro Filtration (MF) and Ultra Filtration (UF) membrane. MF and UF membrane can separate small molecules such as cations (minerals) that can pass through the membrane so that macromolecules such as carbohydrates, fats, proteins, pigments, phenolics and vitamins can be separated from minerals and active ingredients in the absence of minerals can be obtained. The purpose of this paper is to provide research directions in the exploration of the active ingredients of brown algae for pharmaceutical and cosmetic applications without side effects caused by high metal or mineral content above the threshold value in brown algae extracts.

Spatial and temporal variations of metal fractions in paddy soil flooding with acid mine drainage

Environmental release of acid mine drainage (AMD) poses a potential threat to the environment and human health due to its high content of heavy metals. The impact of AMD flooding on unpolluted soil leads to serious pollution over time via a complex process, related to the geochemical behavior of toxic metals that so far has only been partially investigated. Here, a soil column study was conducted to investigate the migration of Cu and Cd fractions in unpolluted paddy soil following treatment with AMD collected from the Dabaoshan Mining area. Tessier's sequential extraction was performed to fractionate the metals at various depths over time. After 160 days of experimental flooding, the soil pH stabilized at 2.52 at a column depth of 5 cm. The fractions of Cu and Cd that were highly mobile increased significantly during AMD flooding. For Cd, the latter already occurred on day 67. At a depth of 20 cm, the total content of Cu maximally increased from initially 26.89 mg kg−1 to 696.96 mg kg−1 on day 160, while the content of Cd maximally increased from 0.22 mg kg−1 to 391.30 mg kg−1 on day 67. Reduced partition index analysis conformed that the mobility of both Cu and Cd significantly increased in contaminated soil during continuous AMD flooding. Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) identified a changed distribution of the elements in the soil, with Fe appearing to have aggregated. The correlation analysis between Cu and Cd in pore water and in different fractions in the soil's solid phase identified a dynamic distribution of these metals in certain geochemical components during their migration. The results of this study contribute to a scientific foundation to describe the geochemical behavior of heavy metals in soil subject to AMD flooding.

Mineral composition and seasonal dynamics of the content of heavy metals in bed loads of ravines and small rivers in the city of Kamyshin (Volgograd oblast, Russia)

The article presents the study of the mineral composition and content of heavy metals (Ni, Cu, Cd, Cr, Pb, Zn) in bed loads (0–1 cm layer) of ravines and small rivers in the city of Kamyshin (Volgograd oblast, Russia). We established that quartz is the most widespread rock-forming mineral found all-over the place. In areas, where proportion of quartz decreases, the content of hydromica and feldspars increases. We discovered that the content of heavy metals in the bed loads increases in 61.1% of cases in spring compared to summer due to the inflow of pollutants from the urban watersheds with snowmelt runoff. Bed loads with a high content of heavy metals should be considered as an object of accumulated environmental damage. Reclamation of the beds of small rivers and ravines is required in order to create a comfortable urban environment and reduce the negative impact on the Volgograd Reservoir.

Preparation of concentrated stabilizer-free dispersions of uniform silver nanoparticles

Stable concentrated aqueous dispersions of uniform 10 nm silver nanoparticles were prepared in absence of colloid stabilizers by reducing silver nitrate with phloroglucinol at room temperature and elevated pH. The key feature of the precipitation process entails triggering suddenly the electrons transfer between the reacting species coexisting in a homogeneous solution (‘latent reaction mixture’). The ensuing silver nucleation occurs rapidly and uniformly in the entire reaction volume leading to the formation of highly uniform dispersed nanoparticles. The phloroglucinol oxidation byproducts play an important role in preventing the aggregation of nanoparticles and facilitating the preparation of highly stable dispersions containing up to 62 wt% Ag (5.7 mol.dm−3). A mechanism rationalizing the long-term stability of silver sols at such high metal content is proposed. The rheological properties of concentrated dispersions permit the inkjet printing of electrically conductive patterns suitable for incorporation in sensors, RFID tags, solar cells, displays, and other electronic devices.

Alkali-Activated Materials with Pre-Treated Municipal Solid Waste Incinerator Bottom Ash

This study presents the results of an experimental campaign on the use of municipal solid waste incinerator bottom ash (MIBA) and fly ash (FA) as precursors for the production of alkali-activated materials. MIBA was subjected to a pre-treatment stage in response to two issues: high metallic aluminum content, which reacts in a high pH solution, releasing hydrogen; and low amorphous content of silica-, aluminum- and calcium-bearing phases, which translates into a limited formation of reaction products. The proposed pre-treatment stage oxidizes most of the metallic aluminum fraction and compensates for the low reactivity of the material via the formation of additional reactants. Different combinations of MIBA and FA were tried—mass-based ratios of 0/100, 25/75, 50/50, 75/25, and 100/0 for MIBA/FA. Two mix designs of the alkaline activator with sodium hydroxide and sodium silicate were evaluated by varying the Na2O/binder and SiO2/Na2O ratios. These mortars were tested in the fresh and hardened state. The results showed that the pre-treatment stage was effective at stabilizing the dimensional variation of MIBA. Despite the lower reactivity of MIBA, mortars with 50/50 of MIBA/FA presented a maximum 28-day compressive strength of 25.2 MPa, higher than the 5.7 MPa of mortars made with MIBA only.

Changes in the biochemical parameters of soybeans depending on the growing conditions

The results of the analysis of changes in biochemical parameters of soybeans depending on growing conditions are presented. The object of the study was samples of soybean (Glycine max (L.) Merr) of the Lydia variety and wild soybean (Glycine soja Sieb. & Zucc.) forms of KA-1344 grown on natural soils (control and with a high content of heavy metals). The analysis was carried out in leaves, stems, roots, flowers and seeds of cultivated and wild soybeans in the phase of the first triple leaf, flowering and fruiting. The content of malonic dialdehyde and the specific activity of acid phosphatase were determined by spectrophotometric method, the activity of peroxidase – by colorimetric method, the content of zinc, copper and lead – by atomic absorption. Electrophoretic spectra of acid phosphatase were detected by electrophoresis on columns of 7.5% polyacrylamide gel. Identification of zones with enzymatic activity on the gel was carried out by appropriate histochemical methods. It has been established that the cultivation of soybeans on soil with a high content of zinc, copper and lead leads to their accumulation in the organs of soybeans. The highest content of the studied metals is found in the roots. Growing soybeans on soil with a high content of zinc, copper and lead led to an increase in the specific activity of peroxidase in its organs. At the same time, the content of malonic dialdehyde in cultivated soybeans significantly increased only in stems during the phase of the first triple leaf and in roots during the flowering phase, and in wild soybeans in leaves, stems and roots during the phase of the first triple leaf and in stems during the flowering phase. It has been revealed that the flowers have the maximum specific activity of acid phosphatase. Cultivated soybeans, under conditions of increased zinc, copper and lead content in the soil, were characterized by an increase in the specific activity of acid phosphatase and the appearance of new multiple forms. For wild soybeans, in general, there was a decrease in the specific activity of acid phosphatase and an increase in the number of multiple forms of the enzyme.

Characterisation of dust emissions from machined engineered stones to understand the hazard for accelerated silicosis

Engineered stones are novel construction materials associated with a recent upsurge in silicosis cases among workers in the stonemason industry. In order to understand the hazard for the short latency of lung disease among stonemasons, we simulated real-time dust exposure scenario by dry-machining engineered stones in controlled conditions, capturing and analysing the respirable dust generated for physical and chemical characteristics. Natural granite and marble were included for comparison. Cutting engineered stones generated high concentrations of very fine particles (< 1 µm) with > 80% respirable crystalline silica content, in the form of quartz and cristobalite. Engineered stones also contained 8–20% resin and 1–8% by weight metal elements. In comparison, natural stones had far lower respirable crystalline silica (4- 30%) and much higher metal content, 29–37%. Natural stone dust emissions also had a smaller surface area than engineered stone, as well as lower surface charge. This study highlighted the physical and chemical variability within engineered stone types as well as between engineered and natural stones. This information will ultimately help understand the unique hazard posed by engineered stone fabrication work and help guide the development of specific engineering control measures targeting lower exposure to respirable crystalline silica.

Porous coal char-based catalyst from coal gangue and lignite with high metal contents in the catalytic cracking of biomass tar

In this study, coal gangue and lignite with high metals-containing are used to prepare porous coal char-based catalysts for biomass tar decomposition via a simple pyrolysis method under CO2 atmosphere. The CO2 etching during the preparation process of the catalysts helps to improve the porosity of the coal char, and the metals in coal are exposed on the surface of the catalyst, thus enhancing the adsorption of the catalysts to the reactants and contact possibility of the reactants with the metals. The activity of the catalysts is influenced by the metals content and preparation temperature, and the coal gangue char prepared at 800 °C (CG-800) exhibits the highest catalytic activity in this work. At a reforming temperature of 700 °C, the conversion efficiency of biomass pyrolysis tar reaches 91.2% using CG-800 as the catalyst with a high total syngas yield of 516 mL/g. Moreover, part of the metal oxides in the catalysts can be reduced by the reducing gases during the tar reforming process, which can further help the catalysts maintain high catalytic activity in the recycling process. During the five-time reuse, the catalysts exhibit excellent stability with only a slight loss in tar conversion and total gas yield.

Comparison of Four Tourmalines for PS Activation to Degrade Sulfamethazine: Efficiency, Kinetics and Mechanisms.

Four types of tourmalines (TMs, S1, S2, S3 and S4) for activating persulfate (PS) to degrade sulfamethazine (SMT) were compared to find the most efficient catalyst. The four TMs were mesoporous materials with abundant functional groups, but were different in terms of size, composition, specific surface area, contact angle, and zero potential point. The removal of SMT in S1, S2, S3 and S4 systems with PS at the optimum reaction conditions ([SMT]0 = 5 mg/L, [PS]0 = 4 mM, [TM]0 = 5 g/L, pH0 = 5, and T = 25 °C) were 99.0%, 25.5%, 26.0%, and 51.0%, respectively, which might be related to the metal content of TM. Although the degradation of SMT in the S1/PS/SMT system was not dominated by SO4•− and •OH, the radicals contributed to the SMT removal in the S2, S3, and S4 systems. 1O2 and holes both contributed to the degradation of SMT in the four systems. The metal at the X position might be related to the generation of 1O2 and holes, while Fe of TM was mainly related to the generation of free radicals, such as SO4•−. Electrochemical impedance spectroscopy tests confirmed that the separation of electrons and holes on the TM surface could be promoted by adding PS and SMT. S1 presented a higher electron-transfer rate than the other three TMs. The PS activation by TM with a high metal content at the X position provided an efficient and low-consumption treatment for antibiotic refractory wastewater.

The Impact of Bio-Based Fertilizer Integration Into Conventional Grassland Fertilization Programmes on Soil Bacterial, Fungal, and Nematode Communities

Phosphorus (P) is an essential plant macro-nutrient applied to soil in agriculture, mainly sourced from non-renewable mined phosphate-rock, of which readily accessible reserves are currently under pressure, while global food demand continues to grow. Meanwhile, an abundance of P is lost in waste-streams. Hence, bio-based fertilizers are increasingly produced using nutrient-recovery technologies and evaluated as a sustainable fertilizer alternative. However, there is little knowledge of how these products affect soil microorganisms. In this study, four new phosphate bio-based fertilizers (two struvite and two incinerator ashes) were assessed in permanent grassland-plots to understand their impact on soil bacterial, fungal, and nematode community responses. The experiment consisted of 40 plots (each 6 × 2 m2) of 8 treatments (2 struvite, 2 ash, cattle slurry, 100% mineral fertilizer, zero P fertilizer, and a control without fertilization) with 5 replications arranged in a randomized complete block design. Community data were obtained by amplicon sequencing of DNA extracted from soil samples and subsequent analysis of community composition, diversity, structure and influencing environmental variables. Diversity of the soil microorganisms was maintained by all bio-based fertilizer treatments. Results showed that soil bacterial, fungal, and nematode communities of the struvite-treatments were similar to those in 100% mineral treatment. Communities in ash-treatments were more disturbed in their compositions, abundances and structures, possibly due to their high pH and heavy metal content. From canonical correspondence analysis, available P, K, and Mg, as well as plant P uptake and biomass yield, were identified as factors significantly influencing bacterial and nematode communities across different treatment groups. In particular, the abundance of environmental disturbance sensitive nematodes (e.g., Dorylaimida) was significantly reduced by one of the ash products. Overall, results indicate that both struvites are benign to soil bacterial, fungal, and nematode communities and can be safely applied as a source of renewable P to meet crop nutrition requirement. The ash products require further investigations before recommending their regular application as fertilizer. As the application of novel bio-based fertilizers will increase in the foreseeable future, the findings of this study would be valuable to feed into developing environmental risk assessment protocols.

PRECIOUS METALS RECOVERED BY URBAN MINING

The circular economy generates major environmental benefits, which result from the use of energy and renewable materials or from reuse and recycling. Being a complex mixture of materials and components, from an economic point of view, the separate collection and recycling of electronic and electric wastes can be cost-effective for products because they contain many hazardous substances, rare or precious metals. This paper presents some aspects regarding the waste with high content of precious or nonferrous metals contained in the electronic/electrical components. Their presence in electronic/electrical waste makes it necessary to recycle and treat them in an ecological way, generating a true industrial symbiosis. In the paper this fact is exemplified by the presentation of a reconditioning-recovery technology that allows the full recovery of all components of some types of electrical contacts widely used in economics. Disposable or defective electrical contact waste was used, as well as technological waste resulting from the manufacture of electrical contact pieces.

Formation of fine particles (PM10) from Zhundong high‑sodium coal at entrained flow gasification condition in a flat-flame burner reactor

Zhundong coal has very high content of alkali metals and alkaline earth metals (AAEMs), which produces much particulate matter (PM) during combustion and gasification, resulting in many ash related problems. Fine PM with aerodynamic size less than 10 μm (PM10) during entrained flow gasification is a critical factor which affects deposition behavior of fly ash in syngas heat exchanger. In this work, a novel flat-flame assisted entrained flow reactor was used to characterize formation of PM10 from Zhundong high‑sodium coal under entrained flow gasification. Results show that the mass concentration particle size distribution (PSD) curves of PM10 exhibited three peaks at 0.0308 μm, 0.255 μm, and 2.47 μm, respectively. NaCl and sodium aluminosilicate were mainly enriched in PM0.1 (fine PM with aerodynamic size less than 0.1 μm). Besides, the increase of water vapor ratio in volume decreased the mass concentration yield of PM10, while it promoted the number concentration yield of PM0.1. In addition, three particle formation modes of PM10 were observed in the mass fraction size distribution curves of Al. The particle size ranges of PM10 in the ultrafine, central and coarse modes and their formation mechanisms from Zhundong high‑sodium coal at entrained flow gasification condition were identified.

Identification of the sources and influencing factors of the spatial variation of heavy metals in surface sediments along the northern Jiangsu coast

Determining the sources and factors influencing the spatial variation of heavy metals in the surface sediments of tidal flats is important for controlling and reducing heavy metal pollution. We used principal component analysis and partial least square regression to analyse the distribution characteristics, sources, and factors influencing the spatial variation of nine heavy metals (As, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn) in the surface sediments of tidal flats along four sites located on the northern Jiangsu coast. Our results indicate that the northern three sampling areas had a high heavy metal content, whereas the southern sampling area had a low heavy metal content. The heavy metals Mn and Pb are related to both natural and anthropogenic sources, whereas V and Cr are primarily derivatives of human activities, and As, Co, Cu, Ni, and Zn are primarily a result of natural processes. The spatial variation of Mn and Pb was primarily affected by the total inorganic carbon and clay content (positive affect) as well as the sand and silt content (negative affect). The spatial variation of V and Cr was primarily related to silt, clay, and total phosphorus content (positive influence) as well as sand (negative influence). In addition, the spatial variation of As, Co, Cu, Ni, and Zn was primarily influenced by the total organic carbon and clay content (positive effect) as well as sand and pH (negative effect). The grain size of sediments plays an important role in the spatial variation of heavy metals in the surface sediments of tidal flats, with fine-grained clay materials being related to the enrichment of heavy metals. The results of our study are important for the control and reduction of heavy metal pollution in coastal sediments, protecting both the ecological environment and human health.

СЕРЕБРЯНАЯ МИНЕРАЛИЗАЦИЯ ХОРОГОЧИНСКОГО КОРЕННОГО ИСТОЧНИКА (СТАНОВАЯ ГРАНИТ-ЗЕЛЕНОКАМЕННАЯ ОБЛАСТЬ, ВЕРХНЕЕ ПРИАМУРЬЕ)

The morphology and chemical composition of minerals of the Khorogochi silver ore occurrence (Upper Amur region) were studied by the analytical scanning electron microscopy. The mineral association is represented by high-grade native silver, basically silver minerals (silver sulphide, sulphoantimonites and silver sulfoarsenides), Ag-containing (fahl ore and galenite), as well as a number of associated minerals (pyrite, chalcopyrite, sphalerite, loellingite, ankerite, hydromica-smectite, etc.). Based on the revealed chemical composition of silver minerals and associated minerals, the features of their spatial relationship, as well as experimental data known from the literature on the resistance of silver-containing systems, the formation temperatures of silver mineralization, which fit into the range of 300–100 oC, and the order of crystallization of its constituent minerals were estimated – from multicomponent compositions with a low silver content (Agtennantite-tetrahedrite, proustite) to compositions with a high content of noble metal (stephanite, polybasite, pearceite, acanthite, native silver). The ore body of silver mineralization in the ore-placer cluster Khorogochi-2 is spatially dissociated from the ore sources of gold-silver mineralization.