High Concentrations Of Heavy Metals Research Articles

Downstream Torrefaction of Wood Pellets in a Rotary Kiln Reactor—Impact on Solid Biofuel Properties and Torr-Gas Quality

Solid biofuels produced from torrefaction have improved coal-like properties in comparison to raw biofuels, yet ensuring uniform product quality is still a challenge. In this study, downstream torrefaction of wood pellets was performed at temperatures between 200 and 270 °C in a rotary kiln reactor to understand the effect of torrefaction temperature on product quality. The torrefied solid biofuel was compared with dedicated fuel properties defined in ISO/TS 17225-8:2016-12. Based on the results, the optimal temperature for downstream torrefaction was found at temperatures of 230 and 250 °C. Above this temperature, the effect of bulk density superimposes not only the increased net calorific value but also values for mechanical durability, amount of fines, and bulk density of the solid biofuel, which were below the thresholds of the fuel standard. Moreover, increasing process temperatures caused higher heavy metal concentrations in torrefied pellets. The composition of condensable and non-condensable fractions of the torr-gas substantially increased between temperatures of 230 and 250 °C and remained on a similar level at higher temperatures. Thus, the utilization of torr-gas for energy recovery purposes and as a precursor for the recovery of valuable chemicals should be balanced with the quality of the solid biofuel in the aforementioned range of torrefaction temperatures to enable the utilization of torrefaction products at further steps.

Indigenous rhizosphere microbial community characteristics of the phytostabilizer Athyrium wardii (Hook.) grown in a Pb/Zn mine tailing

Plant rhizosphere microbiome usually changes dramatically in adaptation to the mine environment to endure high heavy metal concentration, which in turn improves the process of revegetation and phytostabilization of mine tailing and deserves deep investigation. A field study was conducted to investigate the indigenous microbial community of a mining ecotype (ME) of the phytostabilizer Athyrium wardii (Hook.) grown in a Pb/Zn mine tailing and a corresponding non-mining ecotype (NME) grown in an uncontaminated adjacent site. Our study found a slight difference in microbial α-diversity between the ME and NME, and no significant difference between the rhizosphere and bulk soil. Both bacterial and fungal community compositions differed between the ME and NME, for which the differences were mainly driven by pH and metal contaminants. The ME harbored a unique microbial community in the rhizosphere soils different from the bulk soil and NME counterparts. The dominant phyla in the ME rhizosphere were Proteobacteria, Chloroflexi, Actinobacteria, Nitrospirae, and Ascomycota. Several genera from Proteobacteria, Acidobacteria, and Ascomycota were more abundant in the ME rhizosphere than in the NME rhizosphere. Network analysis revealed that keystone taxa were different in the two sites. Some keystone taxa from Gemmatimonadaceae, and Burkholderiaceae and Ascomycota played a critical role in microbial interactions within the mine tailing network. The unique microbial community with high tolerance in the rhizosphere soils of ME may show great benefit for plant growth and metal tolerance of the ME and thereby contributing to the process of revegetation and phytostabilization of mine tailings.

Analyzing the Quality of Dialysis Machines Input Water in Hospitals of Kashan City, in 2019

Introduction: According to high volumes of water used in hemodialysis, quality of water entering the dialysis machine is very important. The current study aims to analyze microbial and chemical quality of water used for hemodialysis in hospitals of Kashan city in 2019.
 Materials and Methods: This descriptive cross-sectional study was performed on 54 water samples used in dialysis machines in hospitals of Kashan city during 3 months of the fall season in 2019. Microbial tests of the samples were done, and also heavy metals were assessed using inductively coupled plasma optical emission spectrometry. Statistical tests, sample t-test, and ANOVA were used to compare the mean results with standards.
 Results: Based on the results, the mean concentrations of magnesium (Mg) (2.7 ± 2.22 mg/L), sulfate (13.09 ± 21.06 mg/L), sodium (Na) (17.27 ± 24.47 mg/L), and potassium (K) (0.09 ± 0.17 mg/L) in all samples were based on the standard levels. However, the mean concentrations of nitrate (3.22 ± 1.21 mg/L), aluminum (Al) (0.26 ± 0.16 mg/L), silver (Ag) (0.52 ± 0.85 mg/L), lead (Pb) (0.08 ± 0.13 mg/L), and zinc (Zn) (0.91 ± 0.71 mg/L) were above standard levels in all the samples. Thallium (Tl) ion was reported to be zero. Moreover, heterotrophic bacteria were not observed in any of the samples.
 Conclusion: Given the high concentration of chemicals and heavy metals in dialysis machines water input, it is necessary to plan for periodic monitoring of water treatment systems and heavy metals and regular replacement of reverse osmosis filters.

Environmental Geochemistry of the Surface Sediments of Sabkhat Daryana, NE Libya

The present paper discriminates between nearshore and farshore sabkha sediments at Daryana Coast,NE Libya, using geochemical viewpoints. The nearshore sediments are mostly sand with low amounts ofmud (Al). High contents of heavy metals found in these sediments can be due to their incorporation incarbonate phases. The farshore sediments are mostly sandy mud with higher contents of Al and lowercontents of heavy metals, except higher contents of Pb. The heavy metals are mainly of anthropogenicorigin (EF > 1.5). Generally, Igeo values indicate that the study area is unpolluted with most heavymetals (except with As and Hg).

Synergistic solidification of lead-contaminated soil by magnesium oxide and microorganisms

Although microbially induced carbonate precipitation (MICP) technology effectively promotes the remediation of heavy metal contaminated soils in low concentrations, the high concentration of heavy metals has a toxic effect on microorganisms, which leads to the decline of carbonate yield and makes the soil strength and environmental safety after remediation no up to the standard. This study describes the synergistic curing effect of MgO and microorganisms on soil contaminated with high concentrations of heavy metals. The experimental results with MgO showed 2–6 times increase in unconfined compressive strength (UCS) compared to bio-cemented samples without MgO. Toxicity characteristic leaching procedure experiments indicated that Pb-contaminated soil at 10,000 mg/kg with quantitative MgO for synergistic solidification could meet the international solid waste disposal standards, which leachable Pb2+ are less than 5 mg/L. In addition, the microscopic results showed that the introduction of MgO promoted the formation of magnesium calcite and dolomite, improved the solidification efficiency of heavy metal contaminants, and demonstrated the presence of Pb2+ in carbonate minerals. This study suggests that MgO and microorganisms have broad application prospects for synergistic solidification of Pb2+ soil.

Health Risk Assessment of Hazardous Heavy Metals in Two Varieties of Mango Fruit (Mangifera indica L. var. Dasheri and Langra)

The spatial assessment of four heavy metals (Cd, Cr, Pb, and As) in two mango fruit (Mangifera indica L.) varieties (Dasheri and Langra) collected from the Saharanpur district, Uttar Pradesh, India, was investigated in this study. The samples of ripe mango fruits were collected from the orchards of 12 major towns in the Saharanpur district from May to June 2022. Heavy metal analysis using atomic absorption spectroscopy (AAS) showed the presence of all selected heavy metals. Specifically, the concentration (mg/kg dry weight basis) range of Cd (0.01–0.08), Cr (0.11–0.82), Pb (0.02–0.15), and As (0.01–0.14) did not exceed the safe limits. The geospatial variation in the heavy metal concentration was significantly (p < 0.05) different as indicated by the inverse distance weighting (IDW) interpolation and analysis of variance (ANOVA) results. The multivariate statistical analysis using principal component (PC) and agglomerative hierarchical cluster (AHC) analyses revealed that the Saharanpur city location had the highest levels of selected heavy metals out of the 12 sampling locations. In this, the Dasheri variety was identified to have higher heavy metal concentrations in comparison to the Langra variety. Moreover, the health risk study using the target hazard quotient (THQ) confirmed that the levels did not exceed the safe health risk index (HRI) limit of 1. However, the health risk assessment for the child group showed relatively high HRI values (<0.35) compared to those of the adult group (<0.09). Therefore, considering the importance of the Saharanpur district in massive mango fruit production, this study provides vital information regarding the biomonitoring of heavy metals in the two most consumed varieties.

Influence of Heavy Metals on the Rheology of a Thermophilic Biological Sludge for nutrients Recovery: Effect of Iron, Copper, and Aluminium on Fluid Consistency

Currently, thermophilic membrane biological reactors (TMBRs) are used to treat industrial wastewaters and biological sewage sludge with the aim of nutrients recovery. The performance of the biological process is strongly influenced by rheological behaviour of the thermophilic biological sludge (TBS) inside the reactor. Considering the high concentration of heavy metals in matrices fed to the reactors, this work aims to evaluate the influence of heavy metal types and concentration on rheological properties of TBS. Sludge has been extracted from a full-scale TMBR and conditioned with Fe3+, Cu2+, and Al3+. Rheological measures have been conducted and constants k and n of Herschel–Bulkley model were used to define the rheological properties of TBS. Rheological properties of high consistency TBS (0.06 ≤ k0 < 0.2 and 0.6 ≤ n0 < 0.8) were not significantly affected by the conditioning with Fe3+, Cu2+, and Al3+. In case of TBS with initial low consistency (0.02 ≤ k0 < 0.06) and behaviour more similar to Newtonian fluids (0.8 ≤ n0 < 1), Fe3+ and Al3+ determined a significant increase in consistency. On the contrary, the addition of Cu2+ reduced k of conditioned TBS with a lower impact on the distance for Newtonian behaviour (n). This work demonstrates the strong influence of Fe3+, Cu2+, and Al3+ on the rheological properties of TBS depending on the initial consistency of the sludge, and the types and dosage of heavy metals.Graphical

Contamination assessment and potential sources of heavy metals and other elements in sediments of a basin impacted by 500years of mining in central Mexico.

Since the middle of the 1500s, mining has been active in central Mexico. Total estimates for low-grade piles and mine tailing materials in the Guanajuato mining district (GMD) are in the range of 150 million tons, covering an area of 15 to 20 km2. GMD is located in the Guanajuato River sub-basin (GRB), which is part of one of the largest basins in Mexico (Lerma-Santiago). Previous studies on the GRB found unusually high concentrations of heavy metals in mining tailings and sediments. Geochemical and statistical methods were used here to determine the sediment's origin, background values, degree of contamination, and toxicity through different contamination indices. This analysis shows that Cu, Co, As, Sb, and Hg are higher than they are in the upper continental crust (UCC) overbank sediments without human and mining influence, because of the ore deposits and rock weathering in GRB. Geochemistry results in stream sediments show anomalies, where Hg, Cu, Zn, As, and Pb are higher than UCC because those heavy metals and trace elements (HMT) have been influenced by human activities and mineral recovery (smelting, amalgamation, cyanidation). The distribution of high concentrations of HMTs and contamination indices occur in the main channel of the Guanajuato River and downstream of the city of Guanajuato. Statistical analyses (cluster and principal component analysis) reveal relationships between Cr, Ni, Cu, and Pb, which are primarily of natural origin, related to rocks of the upper basin. The middle and lower basins are distinctive in their associations between As, Sb, Zn, Pb, and Hg. Additionally, it is recognized that the origins of Pb, Zn, and Hg are geogenic and anthropogenic. This study demonstrates how crucial it is to understand the geochemistry of various HMT sources, with both natural and anthropogenic contributions (stream sediments and rocks), in order to calculate a more realistic background in a basin with both natural anomalies and anthropogenic contamination. The basin is a regional aquifer recharge area, so the new geochemical data are important for improving basin environmental management.

Assessment of sulfidated nanoscale zerovalent iron for in-situ remediation of cadmium-contaminated acidic groundwater at a zinc smelter

Unprecedented high concentrations of heavy metals have been detected in the groundwater at a zinc smelter in Seokpo, South Korea. The outflow of the contaminated groundwater into the nearby Nakdong River must be prevented by some means such as permeable reactive barrier (PRB). As a reactive material for injection-type PRB, we have tested sulfidated nanoscale zerovalent iron (S-nZVI) to assess its efficacy in remediating the groundwater from the smelter. The S-nZVI efficiently removed Zn, Ni, and Al in the groundwater, and neutralized the groundwater to pH > 6. Sulfidation of nZVI greatly increased the removal of Cd (99.8%) compared to that by nZVI (7.2%). MINEQL+ modeling and particle characterization were performed to elucidate the forms of heavy metals in the solution and on the surface of S-nZVI. Raman and XPS results suggested that FeS on the surface of S-nZVI reacted with Cd(II) and Zn(II), forming more-stable CdS and ZnS. Sequential application of NaHCO3 after S-nZVI treatment in a column setup was suited for the removal of remaining Zn and Fe as well as the reduction of microbial toxicity. This study guides to use of S-nZVI for in-situ remediation of cadmium-contaminated groundwater with other coexisting heavy metals from a zinc smelter.

Copper Effect on Microalgae: Toxicity and Bioremediation Strategies.

Microalgae are increasingly recognised as suitable microorganisms for heavy metal (HM) removal, since they are able to adsorb them onto their cell wall and, in some cases, compartmentalise them inside organelles. However, at relatively high HM concentrations, they could also show signs of stress, such as organelle impairments and increased activities of antioxidant enzymes. The main aim of this review is to report on the mechanisms adopted by microalgae to counteract detrimental effects of high copper (Cu) concentrations, and on the microalgal potential for Cu bioremediation of aquatic environments. Studying the delicate balance between beneficial and detrimental effects of Cu on microalgae is of particular relevance as this metal is widely present in aquatic environments facing industrial discharges. This metal often induces chloroplast functioning impairment, generation of reactive oxygen species (ROS) and growth rate reduction in a dose-dependent manner. However, microalgae also possess proteins and small molecules with protective role against Cu and, in general, metal stress, which increase their resistance towards these pollutants. Our critical literature analysis reveals that microalgae can be suitable indicators of Cu pollution in aquatic environments, and could also be considered as components of eco-sustainable devices for HM bioremediation in association with other organisms.

The role of nanofiltration modelling tools in the design of sustainable valorisation of metal-influenced acidic mine waters: The Aznalcóllar open-pit case

Acid Mine Waters (AMWs) are considered the most challenging environmental problem in the Iberian Pyrite Belt (South of Spain) so far, being characterised by an acidic pH (H2SO4-based), high content of heavy metals (e.g. Co, Pb, rare earth elements (REEs)) and non-metals (e.g. As). Nowadays, AMWs are being contemplated as a source of valuable metals (e.g. Zn, Cu, REEs), and different recovery routes have been studied (e.g. ion-exchange, membrane technologies). Among them, nanofiltration (NF) provides the possibility of water (or H2SO4) recovery and concentration of metals, which can be recovered in a subsequent stage. This work evaluates the performance of the Desal DK NF membrane to treat AMW from Aznalcóllar open-pit, which presents a low pH (2.6) and high contents of Zn (920 mg/L), Mg (2540 mg/L) and REEs (17 mg/L). The effect of solution pH on membrane performance was evaluated. Results showed that the equilibrium SO42-/HSO4- controlled the transport of species. Rejections of sulphate were around 84 % at pH 2.1 (prevalence of HSO4-) and increased to 92 % at pH 3.1 (prevalence of SO42-). Metal rejections remained higher than 74 % (except for monovalent species). Additionally, membrane permeances were determined using the Solution-Electro-Diffusion model coupled with reactive transport, and later used to assess the design of the process treatment of the AMW. Results demonstrated the possibility of concentrating metals and recovering H2SO4 as permeate, but also showed that gypsum and anhydrite precipitation can occur. Additionally, CAPEX and OPEX were estimated for a NF plant treating 2 Hm3/year.

Heavy metal pollution status and deposition history of mangrove sediments in Zhanjiang Bay, China

Mangroves have high ecological service value and play an important role in achieving carbon neutrality. However, the ecological services provided by mangroves are gradually declining due to the threat of various pollutants, especially heavy metal (HM) pollution. Researching the status and history of heavy metals (HMs) in mangrove sediments improves understanding of how mangroves can be protected. We studied the Zhanjiang Bay mangroves, which is an important part of the Zhanjiang Mangrove National Nature Reserve, and is greatly affected by human activities, as an example. We analyzed the pollution levels and deposition process of HMs and their influencing factors. In the mangrove surface sediments of Zhanjiang Bay, Pb, Cr, and Co were slightly to moderate enriched and Cu was moderate-heavy enriched. Zn and Hg showed moderate-heavy enrichment and heavy enrichment, respectively. Cu, Zn, Hg, and Co were 1.5, 1.88, 2.66, and 1.27 times the local background, respectively. Cu, Zn, and Hg mainly originated from anthropogenic sources, and Co may have derived from natural sources. The HM data of mangrove sedimentary cores in Zhanjiang Bay were obtained for the first time; high HM content appeared in the deep layer of the cores but not in the mangrove surface sediments. Both cores were well documented for the effects of natural and anthropogenic factors on the deposition process of HMs. Among them, the high enrichment of Hg in 1909–1921 may be closely related to human activities rather than natural formation. Before 1954, dense mangroves favored the accumulation and gradual increase of HMs. The intense human activity in 1945–1963 during the period of economic construction and reclamation of the Nansan Island Engineering led to significant increases in Cu, Zn, Pb, Cr, and Co, which reached their highest values in more than one hundred years. After 1963, anthropic factors such as deforestation and conversion to aquaculture sharply reduced mangrove area. Reclamation engineering enhanced tidal erosion. Natural factors such as precipitation, storm surge, sea-level rise, and high tides have accelerated the erosion and dilution of mangrove sediments in Zhanjiang Bay. These factors have led to the gradual reduction of HM content in sedimentary cores.

Health Risk Study of Heavy Metals from Consumption of Drugs (Solid and Liquid) Samples Derived from Medicinal Plants in Iraq.

Heavy metals are one of the carcinogenic factors harmful to the safety of human health. In plant-based medications, heavy metals can be found. In February 2022, 28 specimens of medicinal drugs (solid and liquid) were collected from Texas drugstores to investigate heavy metals like zinc, iron, and lead utilizing a Shimadzu AA-7000 atomic absorption spectrophotometer (AAS). The current study used a US EPA model to calculate non-cancer and cancer risk parameters for heavy metals in all medicinal drug specimens. Zinc, iron, and lead levels (mg/kg) in solid samples were 1.95-51.43, 29.09-2055.92, and ND-26.68, respectively, while they were 0.043-4.267, 0.100-5.25, and ND-1.434, respectively, in liquid specimens. The average value of total non-cancer risk (TNCR or HII) and total cancer risk (TCCR) of heavy metals intake in solid specimens was 4.54E - 03 ± 1.1E - 03 and 2.11E - 06 ± 6.0E - 07, while in liquid specimens were 1.98E - 04 ± 4.1E - 05 and 9.44E - 09 ± 2.3E - 09, respectively. Compared to liquid specimens, solid specimens have higher concentrations of heavy metals. The zinc, iron, and lead concentrations in the liquid specimens were lower than the WHO-acceptable standards of 50, 20, and 10mg/kg, respectively. On the other hand, few solid specimen results are more than acceptable. However, all the specimens' TNCR and TCCR results were within the US EPA's globally recommended limits. Finally, the results of the heavy metals show no health hazards associated with using the researched medications.

Heavy metals in lake surface sediments in protected areas in Poland: concentration, pollution, ecological risk, sources and spatial distribution

This paper presents the state and spatial distribution of surface sediment contamination of 77 lakes in Poland by Cr, Ni, Cd, Pb, Zn, and Cu. The analyzed lakes were located within a network of nature protection areas in the territory of the European Union (EU). Spatial distribution of the heavy metals (HMs), factors favoring the delivery/accumulation of HMs in surface sediments, and pollution sources were analyzed. The results indicate the contamination of lake sediments by HMs, but the potentially toxic effects of HMs are only found in single lakes. The spatial distribution of Cr indicates predominant impacts of point sources, while for Pb, Ni, and Zn, the impact of non-point sources. The analysis showed the presence of areas with very high values of particular HMs (hot spots) in the western part of Poland, while a group of 5 lakes with very low values of Ni, Pb, and Zn (cold spots) was identified in the central part of Poland. Principal component analysis showed that presence of wetlands is a factor limiting HMs inflow to lakes. Also, lower HMs concentrations were found in lake surface sediments located in catchments with a higher proportion of national parks and nature reserves. Higher HMs concentrations were found in lakes with a high proportion of Special Protection Areas designated under the EU Birds Directive. The positive matrix factorization analysis identified four sources of HMs. High values of HMs concentrations indicate their delivery from industrial, urbanized, and agricultural areas. However, these impacts overlap, which disturbs the characteristic quantitative profiles assigned to these pollution sources.

Experimental and kinetic study of heavy metals transformation in supercritical water gasification of oily sludge

As an industrial organic waste, oily sludge can be transformed into valuable syngas by supercritical water gasification (SCWG) technology. The transformation behaviors of heavy metals in SCWG of oily sludge must be considered to prevent the secondary pollution attributed to the high contents of heavy metals in oily sludge. In this work, the gasification products distribution after SCWG of oily sludge in a batch reactor under different reaction conditions (550–700 °C, 1–15 min) was studied. The distributions of heavy metals (Cu, Cr and Zn) in different forms including acid-soluble and exchangeable fraction (F1), reducible fraction (F2), oxidizable fraction (F3), residual fraction (F4) and heavy metal ions in liquid residues (M+) were presented and the transformation trend of those five fractions during the SCWG process was demonstrated. A reaction pathway and quantitative kinetic model of Zn transformation in SCWG were proposed. The results indicated that gas yield was enhanced at higher reaction temperature and longer residence time. Heavy metals in oily sludge were mainly composed of F3 and M+, they tended to deposit in F4 with increasing reaction temperature and residence time, which was stable and environmentally harmless. F3 showed better reactivity than F2 and contributed more to the formation of F4. Enhancing the transformation of Zn ions in liquid residues to more stable forms was necessary. This study highlighted that SCWG of oily sludge could realize energy utilization and heavy metals stabilization.

Assessment of Pollution by Heavy Metals in the Water and Sediment of Al-Khosur River Bed

The study was conducted on Al-Khosur River basin passing through the city of Mosul from the waterfalls region to its confluence with Tigris River at the Old Bridge. Six sites were selected along the river. Water and sediment samples were collected from there. The study was carried out at the laboratories of Mosul University, through the period from September 2021 A.D. to May 2022 A.D. The concentrations of heavy metals (lead, cadmium and zinc), in water and sediment were measured quarterly. The results indicated that the heavy metals in the water had the highest concentrations in the fourth site in three elements Pb, Cd and Zn, which amounted to (0.64, 0.62 and 0.49) mg/L, respectively. This can be attributed to the bad quality of the civilian subtractions and estuaries discharged in the river which contain high concentration of heavy metals. The results also indicated high rates of heavy metals in the sediments at the fourth site as it reached the concentration of (3.18, 0.92 and 2.85) mg/kg, for Pb, Cd and Zn, respectively. The concentrations of heavy metals in the sediments increased four times for lead and zinc and two times for cadmium due to the increment in water and the contact period between water and sediment due to undecomposition for heavy metals. Keywords: Heavy metals, Al-Kosur River, Mosul environment, Water, Sediment.

ENVIRONMENTAL ASSESSMENT OF SOME HEAVY METALS IN SELECTED MEDICINAL PLANT SPECIES ALONG A BUSY ROAD IN VRNJAČKA BANJA, SERBIA

This study reported the concentrations of Pb, Cd, Cr, Mn in parts of four medicinal plant species (Cichorium intybus L., Mentha×piperita L., Plantago lanceolata L., Verbascum densiflorum Bertol.) collected from two sites, one few meters away and the other 500 m away from a busy road in Vrnjačka Banja, Serbia. Heavy metals were determined by the atomic absorption method using atomic absorption spectrophotometer. Similar content of tested metals in the soil of the tested locations was recorded, only there was more manganese in the soil closer to the road. The highest concentrations of heavy metals were found in the roots of plants closer to the road. The leaves and stem contain smaller quantities of these metals than root, but there are differences between the studied plant species. In conclusion, all examined metals were present in higher concentrations in plants at the location closest to the road than at the location further away from the road.

Lifetime electrophysiological assessment of the level of contaminants in the body of sheep

Purpose: the research was conducted to study the content of contaminants - arsenic As, cadmium Cd, copper Si, lead Pb, zinc Zn, in the body of sheep with different bioelectric activity of superficially localized biologically active centers and to study the meat productivity of experimental sheep.Materials and methods. Research was conducted at the number of sheep of the Romanov breed. As a result of the examination of the lamb, autumn oster, Romanovsky breed, 6 - 6.5 months of age, two experimental groups are formed by the level of biopotentials - high and low (control), seven heads in each. Based on the metamer and structural organization of centers, the segmental theory of the relationship of nervous centers with various organs and systems of the animal organism, superficially localized biologically active centers (plubs) of young sheep, located in the areas of the greatest number of plexus of sympathetic and parasympathetic nervous systems. The dimension of the bioelectric potential Plbats was carried out in the morning (before feeding) for 3 days in a row using the ELAP device. Topographic search and measurement of bioelectric potential. At the end of the procedures for measuring the level of bioelectric potential in the Plbats, three heads of experienced animals from each group were slaughtered, on the basis of control slaughter, the quantitative characteristics of meat productivity were studied, and then they selected samples of organs and tissues for further research. On the day of slaughter, selected samples (liver, the longest back muscle and femoral bone) were transferred to the laboratory to determine the content of arsenic AS, cadmium CD, PB lead, and zinc zn on an atomic-emission spectrometer with an inductive ICAP 6300 Duo plasma .Results. The amount of contaminants in liver samples, the longest back muscle and femur bones of Romanov sheep aged 6-6.5 months with different levels of bioelectric potential of superficially localized biologically active centers was studied. In experiments, it was found that in animals with a higher concentration of heavy metals and arsenic in the organs, the average bioelectric potential of the centers is significantly higher than in animals with a low average bioelectric potential of the centers. The highest concentrations of contaminants were recorded in the bone tissue of animals with a lower bioelectric potential of centers that significantly differed in this indicator from sheep with a higher average bioelectric potential. As a result of the conducted studies, an inverse correlation was established between the average level of bioelectric potential of superficially localized biologically active centers and the content of contaminants in the body of Romanov sheep raised in the Livensky district of the Oryol region.Conclusion. The data obtained allow us to develop an inexpensive method for rapid assessment of the degree of accumulation of contaminants in the body of sheep at an early age, and timely take measures to adjust the concentration of contaminants in slaughter products.

Supercritical water gasification of hyperaccumulators for hydrogen production and heavy metal immobilization with alkali metal catalysts

The high moisture content and heavy metal concentration of hyperaccumulator are the main bottlenecks of resource utilization. Supercritical water gasification technology was used to convert Sedum plumbizincicola (a hyperaccumulator of Zn and Cd) into hydrogen gas and to immobilize HMs into biochar. Homogeneous alkali metal catalysts such as NaOH, Na2CO3 and Ca(OH)2 were added to optimize the experimental conditions. The results showed that NaOH was effective in capturing CO2in-situ, thereby shifting the water-gas shift reaction equilibrium in the forward direction. And the increase of NaOH concentration had a significant promotion effect on hydrogen production. In the non-catalytic gasification of Sedum plumbizincicola, the highest hydrogen (1.5 mol/kg) and H2 selectivity (22.9%) with greater carbon gasification efficiency (19.3%) and lower H2 gasification efficiency (8.7%) of the gas products were obtained at 400 °C with 6 wt% material concentration for 20 min. However, NaOH at 5% mass fraction maximized hydrogen and H2 selectivity up to 7.5 and 98.2%, respectively. Alkali catalyst not only promoted the generation of hydrogen-rich bio-gas but also enhanced the immobilization efficiency of heavy metals. Compared to non-catalytic, when the addition amount of NaOH was 1 wt%, the Zn、Mn、Cd、Pb、Cr accumulated in biochar increased significantly for 76.8, 42.5, 80.8, 75.6 and 80.0%, respectively. This study highlights the remarkable ability of SCWG with alkali catalyst for hydrogen production and heavy metal stabilization.

Agent-assisted electrokinetic treatment of sewage sludge: Heavy metal removal effectiveness and nutrient content characteristics

Sewage sludge (SS) is rich in nutrient elements such as phosphorus (P), nitrogen (N), and potassium (K), and therefore a candidate material for use in agriculture. But high content of heavy metals (HMs) can be a major obstacle to its further utilization. Therefore, an appropriate HM removal technology is required before its land application. In this study, an innovative biodegradable agent (citric acid, FeCl3, ammonium hydroxide, tetrasodium iminodisuccinate (IDS), and tea saponin) assisted electrokinetic treatment (EK) was performed to investigate the HM removal efficiency (RHMs) and nutrient transportation. Citric acid, IDS, and FeCl3-assisted EK showed a preferable average RHMs (Rave) reduction of 52.74−59.23%, with low energy consumption. After treatment, the content of Hg (0.51 mg kg−1), Ni (13.23 mg kg−1), and Pb (26.45 mg kg−1) elements met the criteria of national risk control standard, in all cases. Following the treatment, most HMs in SS had a reduced potential to be absorbed by plants or be leached into water systems. Risk assessment indicated that the Geoaccumulation index (Igeo) value of HMs has decreased by 0.28−2.40, and the risk of Pb (Igeo=−0.74) reduced to unpolluted potential. Meanwhile, no excessive nutrient loss in SS occurred as a result of the treatment, on the contrary, there was a slight increase in P content (18.17 mg g−1). These results indicate that agent-assisted EK treatment could be an environmentally-friendly method for RHMs and nutrient element recovery from SS, opening new opportunities for sustainable SS recycling and its inclusion into circular economy concepts.