High Metal Values Research Articles

Using Bottom Marine Sediments as Environmental Indicator State of (Tolmaitha – Toukra) Region at Eastern North Coast of Libya

This study was carried out on sediment samples collected from the region extended between Tolmaitha and Toukra towns at (Libya) North eastern coast. The study aimed to use the marine sediment as indicator pollution of the studied area. Different heavy metals of (Fe‚ Mn‚ Zn‚ Cu‚ pb‚ Cd‚ Co and Cr) beside the organic matter (O.M)‚ Total phosphorus (T.P) and total nitrogen (T.N) were determined. The results showed variations in concentrations of total phosphorus (T.P) contents and ranged between (0.0037-0.319 ppm) and (0.007-0.240 ppm) during winter and summer seasons‚ respectively. The total nitrogen contents were fluctuated in the ranges of (0.0017-0.370 ppm) and (0.014 – 710ppm) during winter and summer seasons‚ respectively. Also the results showed that the organic matter (O.M) values were ranged between (0.072-0.720%) and (0.097-0.502%) during winter and summer seasons‚ respectively. The contents of heavy metals in sediment samples during summer season were ranged as follows:(16.5 – 398.1 µg/g)¸ (10.436 – 33.879 µg/g)¸ (13.8 – 287.6 µg/g)¸ (0.78 – 31.56 µg/g)¸ (1.34 – 46.72 µg/g)¸ (2.36 – 128.76 µg/g)¸ (9.15 – 28.16 µg/g)¸ (2.17 – 323.41 µg/g) ¸ for Fe¸ Mn¸ Zn¸ Cu¸ Pb¸ Cd¸ Co¸ and Cr¸ respectively. The results showed high values of calcium in the studied sediment samples compared to the potassium and sodium contents. The results of the studied gave indication that area under investigated contain high values of heavy metals, total phosphorus and total nitrogen, this is mainly attribute to the human activities at the studied locations.

Metal contamination, their ecological risk, and relationship with other variables in surface sediments of urban rivers in a big city in Asia: case study of Hanoi, Vietnam.

Urban rivers are significantly impacted by anthropogenic pressure. This study presents the updated assessment of the concentrations of 11 metals and other variables (pH, total organic carbon (TOC) and nutrients (total nitrogen, total phosphorus, and total silica)) in the sediments of four urban rivers in inner Hanoi city, Vietnam, during the period 2020-2022. The mean concentrations of Fe, Zn, As, and Cr were higher than the permissible values of the Vietnam National technical regulation on the surface sediment quality. Moreover, Zn and Cr were at the severe effect level of the US EPA guidelines for sediment quality. The calculation of pollution indices (Igeo and EF) demonstrated that Mn, Ni, and Fe were from natural sources whereas other metals were from both anthropogenic and natural sources. The ecological risk index revealed that metals in Hanoi riverine sediments were classified at considerable ecological risk. High values of metals, TOC, and nutrients in the sediments of these urban rivers mostly originate from the accumulation of untreated urban wastewater that is enhanced by low river discharge. Our results may provide scientific base for better management decisions to ensure environmental protection and sustainable development of Hanoi city.

Distribution Characteristics and Ecological Risk Assessment of Soil Heavy Metals in Baiyangdian Lake

To understand the spatial distribution characteristics and potential ecological risk of heavy metals in soil of Baiyangdian Lake, 55 soil samples were collected and the contents of eight heavy metals (Mn, Cr, Cu, Zn, As, Cd, Pb, and Ni) were detected. The spatial variation structure and distribution pattern were analyzed using geostatistical methods (Moran index and semi-variance model). The degree of heavy metal pollution and its risk were assessed using the geoaccumulation index (Igeo) and potential ecological risk index (Eri and RI). The results showed that the average of ω(Mn), ω(Cr), ω(Cu), ω(Zn), ω(As), ω(Cd), ω(Pb), and ω(Ni) were 467.75, 43.59, 28.57, 89.04, 12.32, 0.18, 19.26, and 30.56 mg·kg-1, respectively, all of which were lower than the screening values of soil pollution risk in agricultural land. However, the contents of Cu, Zn, and Cd were significantly higher than their background values, with two highly variable elements of Cu (48.65%) and Cd (37.52%). The Moran index indicated that Mn, Cu, Cd, and Pb showed weak spatial autocorrelation. Nugget coefficients of both of Cd and Pb shown by the semi-variance model were 100%, suggesting random variation as a main spatial variation driven by anthropogenic factors. High values of soil heavy metals were mainly distributed in the southwest of Baiyangdian Lake with a significant correlation between the heavy metals. The Igeo of soil heavy metals from high to low was Cd>Cu>Zn>Ni>As>Pb>Mn>Cr. Cd pollution was the most common, in which 67.27% of the samples were lightly polluted. Ecological risk assessment revealed that the average Eri of Cd was 58.81, belonging to the middle ecological risk level, and the rest were at light ecological risk. As a whole, the RI of soil heavy metal pollution in Baiyangdian Lake was at a light ecological risk level (87.81), with the highest contribution rate of Cd to RI (66.39%). Thus, it is necessary to strengthen the control of soil heavy metal Cd pollution in Baiyangdian Lake in the future.

Multiproxy analysis in contaminated sediments from Niterói Harbour (Guanabara Bay), Brazil

Harbours are located in major urban centres around the world and are of great economic importance to the cities in their surroundings. However, the intense traffic of boats and ships can generate environmental impacts that can directly affect the local biota as well as the population that lives in surrounding areas. Therefore, this work aimed to analyse the surface sediment of the Niterói Harbour using chemical, biological and micropalaeontological tools to investigate the environmental condition of this important harbour in Rio de Janeiro State. The pseudototal trace metal data analysed in the surface samples showed values far above those of the greater Guanabara Bay background. These data were corroborated by a high mortality rate of Artemia sp. and elevated presence of the bacterium Vibrio fischeri, indicating a high rate of local pollution. Dinoflagellate cysts also showed a direct response to high values of pseudototal trace metals. The data obtained in this study emphasize a need for greater monitoring of ports since the experience gained through this study in a Brazilian harbour can serve as an example for the management of other harbours located in large urban centres around the world.

Effects of bio-chemo-mechanical processes on the properties of contaminated marine sediments

A detailed multi-scale investigation of the geotechnical, chemical and mineralogical properties was conducted on contaminated sediment samples collected within the Mar Piccolo, a marine basin in the south of Italy. The basin is located close to one of the most important industrial sites in Europe, which has also been declared ‘at high risk of environmental crisis’ and prioritised for remediation activities. A multidisciplinary investigation campaign showed that the samples collected close to the sea floor are characterised by high values of both heavy metals and organic pollutants and by the presence of significant amount of organic matter. Several samples in the top layer exhibited peculiar geotechnical properties, in terms of plasticity and activity indexes, compressibility and hydraulic permeability. While the prime suspect for such unconventional behaviour was chemo-mechanical coupling between the soil skeleton and contaminants, it turned out that the biogeochemical degradation of organic matter and the presence of microfossils and diatoms is likely to affect significantly the micro to macro behaviour of polluted marine sediments.

Heavy Metals and Nutrients Loads in Water, Soil, and Crops Irrigated with Effluent from WWTPs in Blantyre City, Malawi

Heavy metals may cause acute and chronic toxic effects to humans and other organisms, hence the need to treat wastewater properly, as it contains these toxicants. This work aimed at assessing zinc, copper, cadmium, and chromium in water, soil, and plants that are irrigated with effluent from Manase and Soche Wastewater Treatment Plants (WWTPs) in Blantyre, Malawi. Atomic Absorption Spectrophotometry (AAS) was used to assess the heavy metals. Heavy Metal Health Risk Assessment (HMHRA) on plants (vegetables) around both WWTPs was also conducted. Average daily dose (ADD) and target hazard quotients (THQ) were used to assess HMHRA. Physicochemical parameters were determined using standard methods from American Public Health Association (APHA). The heavy metal ranges were below detection limit (BDL) to 6.94 mg/L in water, 0.0003 to 4.48 mg/kg in soil, and 3 to 32 mg/L in plants. The results revealed that plants irrigated with effluent from WWTP had high values of aforementioned metals exceeding the Malawi Standards and WHO permissible limits. Furthermore, the health risk assessment values showed that vegetables consumed for a long period of time from Manase WWTP were likely to cause adverse health effects as compared to those from Soche WWTP.

Assessment of Groundwater Quality at Selected Location of three Wells and Al-Warrar Canal, Ramadi City, Iraq.

To classification groundwater quality in the study area, three wells were drilled at a depth of 10m and selected two locations across Al Warrar Canal to represent their water quality. Water samples were collected from these wells and the Warrar Canal to examine water quality. Then results were compared against the World Health Organization (WHO) limits to study the Index of Water Quality (WQI). WQI was calculated according to the Canadian Council of Ministers of the Environment (CCME), and the quality of water was evaluated for domestic and irrigation uses. The samples were tested for electrical conductivity, pH, temperature, total dissolved solids, chloride, total hardness, nitrate, and alkalinity according to the standard methods. The results of laboratory analysis showed significant differences among the wells and Warrar Canal water quality in the measured parameters according to WHO limits. Due to many human activities like urbanization, agrarian overflow, drainage of untreated sewage, and industrialization, high values of trace elements and heavy metals were recorded in wells three. For agriculture purposes, the results show that the water in the three wells is very high salinity, where the Warrar Canal is high salinity, and Canal water causes saline and alkali damages. It was recommended that the WQI in three wells was poor water quality whereas, marginal water quality was pointed in AL Warrar Canal.

Integration of ASTER satellite imagery and 3D inversion of aeromagnetic data for deep mineral exploration

Due to high metal values and raised difficulties in finding superficial deposits, the exploration for mineral resources needs to reach greater depths. To achieve this objective, integrating ASTER and 3D inversion of aeromagnetic can be a useful tool in imaging deep magnetic mineralization hosting-structures. In this study, we present such integrated approach for deep mineral exploration in some promising zones of Gabal (G) Semna region, Eastern Desert (ED) of Egypt. Aeromagnetic data was used to delineate the structures and their relation to ore deposits and ASTER data was utilized for mapping lithological units and the hydrothermal zones. The 3D inversion was employed to imagine the depth and geometry of the magnetized ore bodies in the zones that identified by processing ASTER data. The 3D magnetic inversion revealed that mafic rocks and metavolcanics exhibit high-amplitude magnetic anomalies. High amplitude (positive) magnetic anomalies are joined with the large susceptibilities metavolcanics. Alteration zones in the mafic to basic bedrock and alongside major fault systems are high potential zones that revealed by ASTER image analysis. Aster and aeromagnetic data were used to map and alteration zones surface geology that can host mineralization and the 3D inversion was applied to outline the subsurface extent of these promising areas. This approach can be broadly used for deep mineral exploration in the Egyptian ED and identical areas around the world.

Variation of the heavy metals concentration in some wells and springs water between Haditha dam and the site of Al-Baghdadi dam

The study area is located between latitude 33° 51.9 -34° 19 and latitudes 42° 15.83 to 42° 40.3 in the northwest part of the Governorate of Anbar. The research focuses upon the analysis of Heavy Metal variation between the dam of Haditha and the dam of Al Baghdadi in (8) wells and (4) springs. Nine heavy metals, including Zn2+, Fe2+, Cd2+, Mn2+, Pb2+, B2+and As2+, were analyzed for the wells and springs samples in August 2019 and March 2020. Present study shows a spatial and temporal change in heavy metals, whereas all well samples did not exceed allowable limits suggested by WHO and IQS. A major source of High values of heavy metals in some water samples of springs may be due to the effects of Agriculture, Fertilizers, pesticides and fish lake. The results also show a variation in the depth and source of wells, reflected by different co-existing sources. In addition to some human activities, which raise the level of concentrations.

Sediment Contamination by Heavy Metals and PAH in the Piombino Channel (Tyrrhenian Sea)

Sediment contamination is of major concern in areas affected by heavy maritime traffic. The spatial variation and contamination of 11 trace elements and 17 PAHs in surface sediments were studied along a 31 km transect along the seaway from the port of Piombino (Tuscany) to the port of Portoferraio (Elba Island) in the Northern Tyrrhenian Sea. Heavy metal contamination was detected at sites near Piombino (Ni, Pb, Hg, Cu and Zn) and at sites near Portoferraio (Pb, Zn, Hg, Cr and Cd). Each of the 35 sampled sites showed PAH contamination, with the highest concentrations at sites near Portoferraio. The most abundant isomers detected were 2- and 4-ring PAHs. PAH ratio analysis showed a prevalence of PAHs of pyrolytic origin. High values of PAHs and heavy metals were related to high sediment water content, TOC, silt, and clay content. Arsenic increased with increasing depth. The correlation between concentrations of metals and PAHs suggests common anthropogenic sources and is of concern for possible synergistic adverse effects on the biota.

A sustainable solution for fresh-water demand in mining sectors: Process water reclamation from POX effluent by membrane distillation

Direct contact membrane distillation (DCMD) was applied to the oxidation under pressure (POX) effluent treatment at different feed temperatures (50–70 °C) and recirculation flowrates (0.3–1.5 L/min). Two different commercial membranes made of poly(tetrafluoroethylene) (PTFE) and poly(vinylidenefluoride) (PVDF) were compared, including the contribution of an additional spacer, in terms of distillate recovery rate and retention efficiency. Lower wetting rates were obtained for lower feed temperatures and recirculation flowrate, which allowed for a greater permeate recovery rate. In contrast, an increase in both feed temperature and recirculation flowrate led to lower resistances. Among them, the resistance imposed by the membrane had the highest contribution to mass transfer resistance, whereas fouling resistance had negligible effects. Due to its lower hydrophobicity, PVDF membranes were more subjected to wetting if compared to PTFE membranes. Under the best conditions (PTFE with spacer, feed temperature of 60 °C and 0.3 L/min) the process had an average distillate flux of 6.82 L/m2 h and a permeate recovery rate of 33.91%, without compromising the permeate physicochemical quality. That corresponds to high values of metals and acidy retention, >95.7% and >99.9%, respectively, generating a permeate that can be used directly as reuse water in the mining plant. Regardless of that, both membranes maintained its rejection efficiency and distillate flux after 240 days exposed to the effluent under similar experimental conditions. Moreover, no significant changes were observed in their morphology or structure. Overall, DCMD was considered as a promising alternative for process water reclamation since the final temperature of this effluent can reach up to 80 °C, which corroborates the use of its residual heat as a driving force of DCMD, thus reducing the energy demand for the processing of this effluent.

Distribution, source, and pollution assessment of heavy metals in Sanya offshore area, south Hainan Island of China

Forty-four surface sediments from Sanya offshore area are analyzed for assessing heavy metals (Cu, Pb, Zn, Cr, Cd, Hg, and As) pollution. High metal values except for As are located in the southern areas which have fine-particle presence. However, high values of the metal As appear at a depth of 15–30 m in the Yazhou Bay. As and Pb show moderate contamination, and other metals show low contamination. The metals (except for As) are confirmed not to be enriched to slightly enriched, which are controlled by the grain size and mainly derived of the natural weathering products. The moderately severe to severe enrichment of As occurs in the Yazhou Bay and the nearshore area of the Sanya Bay. The reason is due in part to the excessive use of agricultural fertilizers. Further, it is also likely to be related to the high background value of As in the sea area.

Distribution of heavy metals, soil microbial enzymes and their relationship in Kano, Northwestern Nigeria

The increase in population and industrial growth has led to increased production of industrial and domestic waste which contain heavy metals in various forms. Therefore, affect the diversity and activities of soil microbes and subsequently affect environmental sustainability. This research aimed at assessing the distribution of heavy metals, soil enzymes, and evaluate the functional relationship if any. The study area was divided into two locations as contaminated and control; thus, each location one square kilometre was demarcated and divided into 25 small square (grid). A Sample was collected in each grid from 0 – 15 cm depth using point composite sampling technique. The properties investigated are heavy metals, enzymes, pH, and soil temperature. The results of the analyses were subjected to statistical analyses to undertake one-way analysis of variance, and a t-test of means at 𝛂 value of <0.05, also correlation, and regression at a P<0.05 significant level. The results revealed that there is a gradual accumulation of all heavy metals and the concentration is higher in the contaminated than control locations. The soil is potentially polluted with Cd is clean from Cr, Fe, Mn, Zn, Pb, and Cu. High values of heavy metals were discovered in the dry season than the wet season due to rainfall which enhanced the dissolution, leaching, and runoff of heavy metals which is capable of removing the metals from the subsurface. High pH and temperature in the contaminated location influenced the toxicity and microbial activity respectively, this results in high enzymatic activity in the contaminated location. Favourable environmental conditions in the wet season led to the higher activity of the enzymes than the dry season. The finding also revealed that phosphatase and urease were negatively correlated with Cd and Ni. Inversely, dehydrogenase was negatively correlated with Ni and Zn. It was concluded that the determination of the heavy metals and enzymes reflects the microbial activities in soils and is considered as soil quality indicators. Keywords: soil enzymes, contamination, soil microbes, biological indicator, soil quality DOI: http://dx.doi.org/10.7454/jglitrop.v4i2.81

Occurrence of Liddicoatite-Bearing LCT Pegmatites in Sirohi Region, Northwest India and their Rare Metal Potentiality

Rare and trace element study of pegmatites around Sibagaon area of Sirohi region, Rajasthan, India revealed that the pegmatites are of rare element class and LCT (Li–Cs–Ta) type. Rare metal concentration in these pegmatites is notably high against crustal abundance, with Li ranging from 1007 to 10785 ppm, Rb from 1285 to 9147 ppm, Cs from 36 to 1142 ppm, Ta from 12 to 386 ppm, Sn from 54.22 to 2283.61 ppm and F from 2724 to 48,275 ppm. Integration of EPMA and LA-ICPMS analyses indicated that the main Li-bearing mineral in pegmatites is lepidolite with Li ranging from 21,599 to 28,178 ppm, which is economically worthwhile to process for Li, followed by elbaite and rare mineral liddicoatite, which has not been reported so far in India. Rare earth element (REE) distribution pattern shows enrichment of LREEs than HREEs, indicating that pegmatites are fractionated and thus causing enrichment of rare metals. This reporting of liddicoatite-bearing LCT pegmatites from Sirohi region with high anomalous values of rare metals can therefore be a good prospect for rare metal exploration in India in the present economic scenario. These pegmatites have indicated a syn-collisional signature and may be related to the accretion of Marwar craton with greater Indian land mass along the Phulad Shear zone.

Assessment of heavy metal contamination in natural waters of Dereli, Giresun: an area containing mineral deposits in northeastern Turkey.

The concentration of heavy metals in the natural waters of the area surrounding Dereli (Giresun), a mineralized area, was determined. In addition, the physicochemical parameters (such as pH, Eh, and HCO3-) influencing the concentration of dissolved metals in waters were evaluated. Samples were collected from stream, spring, and main river waters, some of which are used by local residents for drinking, fish farming, and animal husbandry. The present data indicate that the water-rock interaction is the main process controlling the chemical composition of waters in the area. The waters are predominantly CaMgHCO3-type waters with alkaline pH values. Heavy metal concentrations (Pb, Zn, Cu, Fe, Mn, U, Cd, As, Hg, Sb, Ni, Co, and Ba) in waters were generally low. Relatively high values of certain metals were determined in waters of the Kotana and Kurtulmus sites of Dereli. The levels of Pb in the river, stream, and spring water samples in these sites were somewhat higher than the Pb values reported in the literature for natural waters. However, these values only slightly exceeded the Pb water limit values proposed by the USEPA and the WHO. In addition, the concentrations of other heavy metals, except Pb, were fairly similar to those of other natural waters and these values were also under the drinking water limits set by the WHO and the USEPA. This study shows that waters in the area of Dereli were not significantly affected by mineralization. This is most likely caused by the bicarbonate-rich waters affecting the dissolved metal concentrations.

Distribution characteristics and potential risk assessment of heavy metals in seawater and sediment of Liaodong Bay

Distribution of heavy metals (Hg, Cu, Pb, Zn, Cd and Cr) in the seawater and sediments were studied based on data from two oceanographic surveys carried out in Liaodong Bay in May and October 2016. The results showed that the values of heavy metals in seawater represent a uniform distribution, while no trends were detected for spatial distribution. High values of heavy metals in sediment were generally distributed nearshore areas in October. Concentrations of Pb, Zn, Hg in seawater were higher than the national guideline values of Mar. sediment quality of China. Values of Cu, Zn, Cd and Hg were higher than the national guideline values of Mar. sediment quality of China in October, while quality was in good condition in May. Correlation analysis showed that TOC was mainly contributed for the variations of heavy metals. The potential ecological risk analysis of heavy metals indicates that Hg, Cd and Cu should be listed as the priority contaminant metals in Liaodong Bay.

Risk assessment, spatial patterns and source apportionment of soil heavy metals in a typical Chinese hickory plantation region of southeastern China

Chinese hickory (Carya cathayensis Sarg.) is a famous woody nut in China. Currently, there is an increasing concern related to the soil heavy metal pollution in Chinese hickory plantations. In this study, a total of 188 soil samples were collected from Lin’an city, a typical Chinese hickory production area. The results showed that the average background concentrations of Cd, Cu, Zn, Pb, Ni and Cr in soils were 0.37, 40.76, 87.61, 30.10, 28.33 and 56.57 mg kg−1, respectively. The Cd and Pb concentrations in Chinese hickory plantation soils had strong variability coefficients of 186.49% and 95.42%, respectively. Compared with the background values in Zhejiang province, the heavy metals were enriched in the plantation soils. The accumulation ratio followed the order of Cu > Cd > Pb > Ni > Zn > Cr. Part of the study area was seriously contaminated by Cd and Cu, as 31.38% of soil Cd and Cu samples exceeded the second grade standardized value of Environmental Quality Standards of Soils (EQSS). The soils in our study area generally reached a moderate ecological risk, as its average RI value reached 103. Moran’s I and Kriging interpolation results revealed that all the studied heavy metals in soils had clear spatial distribution patterns. The high values of soil heavy metals (except Pb) were mainly distributed in the localities closest to the mine area. The apportionment of heavy metal pollution sources showed that the Cu, Ni and Cr in soils were mainly related to mining activities, Pb was closely related to fertilizer application, Cd and Zn were related to both. The heavy metals in soils may pose a potential threat to local ecosystem and human health. Our results implied that soil heavy metals should be tested, and risk-based management should be performed in the economic plantations in China. These maps could provide useful information for forestry and environmental management.

Evaluation of Potential Toxic Metals Accumulation in Wheat Irrigated with Wastewater.

The present study was carried out to ascertain the level of various metals in wheat variety (Chagi-4) irrigated with diverse doses of wastewater. The concentration of metals in soil, water and wheat grain samples was examined through an atomic absorption spectrophotometer. In wheat grains, the mean values of metals (mg/kg) varied from 0.06 to 0.2 for Pb, 1.2 to 1.6 for Cd, 0.6 to 0.9 for Ni, 0.8 to 1.6 for Fe, 0.4 to 1.0 for Mn, 0.7 to 1.4 for Cu, 0.3 to 0.5 for Cr, 0.1 to 0.9 for Zn and 0.03 to 0.2 for Co, correspondingly. Measured concentrations were found within the permissible limit given by FAO/WHO except for cadmium whose concentration exceeded an acceptable limit 0.2mg/kg suggested by FAO/WHO. It might be due to high soil pH, which hinders the efficient transfer of metals between different mediums. Wastewater irrigated soil, wheat and water had high metal values, but the low rate of transfer was noticed from soil to grains. Higher bioconcentration factor was obtained for manganese and cadmium; cadmium had even higher pollution load index, which could indicate the contamination status of soil. Therefore, regular monitoring of wastewater is necessary to prevent the excessive build-up of metals.

INFLUENCE OF CONSTANT MAGNETIC FIELD ON STRUCTURE FORMATION IN STEELS AT HIGH-SPEED LASER PROCESSING

Experimental studies of laser-irradiated layers in a magnetic field (MF) have shown a non-trivial morphology of the surface of handling zone of material in case of reflow. Twisting of a thin layer of liquid metal is observed, irradiated area is getting a crescent appearance, definitely strictly oriented in relation to magnetic flux. This is probably due to the effect of Righi-Leduc, as well as the action of Lorentz forces, which deflect the electrons flow. As a result, there is significant mixing of metal in the irradiation zone, chemical composition equalization, which positively affects the strength properties of the products. One of the important consequences of the MF-effect on the results of laser processing is the phenomenon of magnetostriction. In laser irradiation without MF slide lines were observed on the pre-polished surface patterns resulting from the emerging thermal and structural stresses. By analyzing the topography of irradiated surfaces using modern analysis techniques and computer image processing, it was established that irradiation in MF in conditions of magnetostriction decreases the stress level in irradiated areas and reduces the risk of cracking. The results of temperature measurements at the irradiated spot on cooling stage allow establishing that the cooling rate during laser processing in a MF is considerably higher than without the field. It affects the processes of phase and structural transformations. At laser heating in MF microheterogenic austenite is supercooled with great speed to temperatures of martensite transformation. After that its transformation begins, the sequence of which is determined by the level of local saturation, degree of deformation and is controlled by temperature. The first crystals of martensite are formed in the least saturated areas of austenite, and a very high speed (thousands or tens of thousands of °С/s) of the transformation process beginning γ → α prevents martensite self tempering, which partially can occur when the temperature decreases further due to transformation spread on the remaining volume of austenite, grabbing areas of different saturation. As a result, along with the “fresh-formed” martensite in the areas of laser quenching the martensite is formed, in which segregation of carbon or even ε-carbide may occur and residual austenite with high carbon intensity are formed. Released dispersed carbides contribute to obtaining a sufficiently high hardness values of metals irradiated in a MF.

Spatial Variation of Heavy Metals in Soils and Its Ecological Risk Evaluation in a Typical Carya cathayensis Production Area

In recent years, the problem of soil pollution has become more and more serious. The problem of soil heavy metal pollution and its related human health risks has become a hot spot at home and abroad. Carya cathayensis is a unique high-grade woody nut and oil tree from China, and there are few reports on heavy metal pollution in Carya cathayensis plantation soils. Therefore, in order to study the spatial variability of heavy metals and the risk of pollution in Carya cathayensis soil and to promote the sustainable development of the Carya cathayensis industry, Lin'an, a typical Carya cathayensis plantation area, was selected for this study. A total of 188 soil samples were collected from the study area. We systematically studied the spatial heterogeneity of soil heavy metal content in the study area based on GIS technology, geostatistics, Moran's I, and other spatial analysis methods. The single factor pollution index method, the Nemerow comprehensive pollution index method, and the potential ecological risk assessment method were used to evaluate the heavy metal pollution in the study area. The results indicated that the mean content of soil cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), and chromium (Cr) were 0.37, 40.76, 87.61, 30.10, 28.33, 56.57 mg·kg-1, respectively. The average values of Cd and Cu were 1.33 and 2.87 times of the background values, respectively, and the average content of other heavy metals did not exceed the background values. The results of the single factor Nemerow pollution index and potential ecological risk assessment methods showed that heavy metals in the study area exceeded the soil background values in some samples, and the second grade standard of soil environmental quality was exceed for Cd, Cu, Zn, Pb, and Ni in 31.38%, 31.38%, 2.65%, 0.53%, and 17.02% of the samples, respectively. This indicated that the soils in the study area had different accumulation characteristics for Cd, Cu, Zn, Pb, Ni, and Cr, and the local soil had reached pollution levels for Cd, Cu, Zn, Pb, and Ni. Among them, Cd was the most serious, reaching the degree of strong ecological damage, followed by Cu. In general, the heavy metal contents indicated a moderate degree of ecological damage. Based on the analysis of the semi-variance function, the Cd, Cu, and Ni in the soil were best fit with exponential models, the Zn and Pb were better fit with the Gaussian model, and Cr was consistent with the spherical model. Cd, Cu, Pb, Ni, and Cr had the strong spatial autocorrelation, with Nugget/Sill ratios of 12.1%, 4.6%, 14.9%, 2.6%, and 11.2%, respectively, while the Nugget/Sill ratio of Zn was 48.8%, indicating a medium spatial autocorrelation. Moran's I and Kriging interpolation results found that the heavy metals Cd, Cu, Zn, Pb, Ni, and Cr all had obvious spatial distribution patterns and local spatial aggregation phenomena. The high values of heavy metals in soils were mainly found in Taiyang, Daoshi, Qingliangfeng, Heqiao, and Tuankou, and the probability of the risk for contamination by Cd and Cu was higher in the study area. The high values of Cd, Cu, Zn, Ni, and Cr were mainly related to mining, while Pb was closely related to the application of potassium.