Low Concentrations Of Heavy Metals Research Articles

Soil heterogeneity within a vineyard impacts the beta but not the alpha microbial agro-diversity

Here we investigate the effect of agricultural integrated management on soil microbial diversity within a vineyard with a history (20 years) of exposure to frequent applications of fertilizers and pesticides each season. Considering that these practices were mainly directed to the target plant (i.e. grapevine) and its surrounding area, we expected that these practices have influenced the soil alpha and beta bacterial and fungal diversity differently. Soil samples were collected from three different sites: row, inter-row (space between vines rows) and headland.The soil microbial community was investigated by targeted amplicon sequencing of the 16SrRNA gene (for bacteria) and the ITS region (for fungi), and the chemical and physical soil properties have been characterized.Soil samples collected in row and inter-row were chemically and microbiologically different from the headland soil (PERMANOVA: row/inter-row vs headland P ≤ 0.01), exhibiting this latter a significantly lower concentration of heavy metals. This soil heterogeneity seemed to play a crucial role in the variation of species diversity of microbial communities among sites (i.e. beta-diversity). In contrast, the mean species diversity in each site (i.e. alpha-diversity) did not change among the sites.The sole variation of the beta-diversity could indicate a possible turnover of soil microbial communities to agricultural practices without compromising the alpha-diversity values.

DISTRIBUTION PATTERNS OF MACRO- AND MICROELEMENTS IN THE “SOIL – PLANT” SYSTEM IN THE MIDDLE TAIGA OF EASTERN FENNOSCANDIA

The distribution patterns of macro- and microelements in the “soil – plant” system were studied in different aqueo-glacial plain landscapes and geochemical environments in the middle taiga of Eastern Fennoscandia, in the Kivach Strict Nature Reserve. Data on the chemical composition of different parts of dominant plant species are provided. Mosses and lichens are noted for low ash content and relatively low concentrations of macro- and microelements. The low content of heavy metals (nickel, copper, chromium, cobalt) indicates the absence of air-borne industrial pollution in the study area. Dwarf shrubs of the genus Vaccinium are phylogenetically specialized – bilberry and cowberry are calciphagous and accumulate manganese. Pine needles contain equal amounts of potassium and calcium, as well as high concentrations of magnesium and manganese. Potassium, and also copper and cobalt are further translocated to newly formed plant organs. Data on the chemical composition of soils and plants were used to calculate the biological absorption factor and the index of biochemical activity for plants. Chemical elements were groups by the rate of their involvement in the biological cycle. Manganese, calcium and potassium prove to be the most biogenic. Zinc and copper are also actively involved in the biogenic cycle. Among the studied plant species, the index of biochemical activity was the highest in bilberry. The results reveal a slight variation in the content of a majority of the studied chemical elements and the rate of biological uptake by plants across the range of landscape-geochemical conditions. A general finding is that the principal factors for variation in macroelements are the plant’s species identity and physiological characteristics, while the content of microelements varied in relation to the topographic position and hydrological conditions.

Investigation of inorganic elemental content of honey from regions of North Island, New Zealand

Determination of geographical origin of honey is important to consumers to confirm authenticity. This study investigated the elemental fingerprint of 181 honey samples collected from apiary sites in six regions of North Island, New Zealand to determine if differences were observed due to region of collection or land use surrounding the hive (e.g. agricultural, rural, urban). Using principal component analysis, soil related elements (Ca, K, Mg, Mn, Na) provided 75.2% discrimination of samples in the first two principal components. Overall, low concentrations of heavy metals were observed; lead was present in close proximity to highly trafficked roads (28.1% of samples; 9.50–76.5 µg kg−1) and cadmium was primarily present in honey collected from agricultural land in the Waikato (<51.6 µg kg−1). The use of an elemental fingerprint of New Zealand honey may be advantageous to determine the geographical origin compared to honey produced from other countries.

Distribution characteristics and correlation of heavy metals in soil and total suspended particles of Urumqi City

In this study, soil and total suspended particles samples (TSP) were collected from different soil layers in four functional areas of Urumqi City, Northwest China, and electric heating plate digestion and inductively coupled plasma-optical emission spectrometry (ICP-OES) were used to determine the mass fractions and spatial distribution of six heavy metals. The aim was to determine the effects of human activities on the urban soil and atmosphere and provide a theoretical basis for environmental protection and management in Urumqi. The results showed that: (1) The average mass fractions of Cr, Cu, Mn, Ni, Pb, and Zn were 129.24, 42.445, 691.70, 48.705, 31.36, and 126.5 mg kg−1, respectively; the average mass fractions of Cr, Zn, Ni, and Cu exceeded the limit of the national soil standard; the pollution indexes were 1.44, 1.27, 1.22, and 1.21, respectively. (2) The heavy metal contents of surface soils are higher in the industrial, traffic, and cultural and educational areas than in the clean park area; in the vertical section, the heavy metals in the industrial, traffic, and culture and education areas show a weak epimerism, and the soil in the park area shows a good primitivity. (3) The ratios of the highest to lowest concentration of heavy metals in TSP can be ranked as follows: Pb (9.75) > Mn (2) > Ni (1.48) > Cr (1.36) > Cu (1.32) > Zn (1.17). (4) The correlations of heavy metals between the soil and TSP are significant, indicating that dry and wet deposition significantly affect the heavy metal content of the soil.

Rapid Determination of Low Heavy Metal Concentrations in Grassland Soils around Mining Using Vis-NIR Spectroscopy: A Case Study of Inner Mongolia, China.

Proximal sensing offers a novel means for determination of the heavy metal concentration in soil, facilitating low cost and rapid analysis over large areas. In this respect, spectral data and model variables play an important role. Thus far, no attempts have been made to estimate soil heavy metal content using continuum-removal (CR), different preprocessing and statistical methods, and different modeling variables. Considering the adsorption and retention of heavy metals in spectrally active constituents in soil, this study proposes a method for determining low heavy metal concentrations in soil using spectral bands associated with soil organic matter (SOM) and visible–near-infrared (Vis–NIR). To rapidly determine the concentration of heavy metals using hyperspectral data, partial least squares regression (PLSR), principal component regression (PCR), and support vector machine regression (SVMR) statistical methods and 16 preprocessing combinations were developed and explored to determine an optimal combination. The results showed that the multiplicative scatter correction and standard normal variate preprocessing methods evaluated with the second derivative spectral transformation method could accurately determine soil Cr and Ni concentrations. The root-mean-square error (RMSE) values of Vis–NIR model combinations with PLSR, PCR, and SVMR were 0.34, 3.42, and 2.15 for Cr, and 0.07, 1.78, and 1.14 for Ni, respectively. Soil Cr and Ni showed strong spectral responses to the Vis–NIR spectral band. The R2 value of the Vis–NIR-based PLSR model was higher than 0.99, and the RMSE value was 0.07–0.34, suggesting higher stability and accuracy. The results were more accurate for Ni than Cr, and PLSR showed the best performance, followed by SVMR and PCR. This perspective has critical implications for guiding quantitative biogeochemical analysis using proximal sensing data.

Thiobacillus Acidophilus Removes Lead and Copper From Wastewater Containing Low Concentration of Heavy Metals

One of the main source of heavy metal wastewater is the electronics industry. If treated ineffectively, it may be discharged into water bodies, causing water body pollution and endangering human health. Traditional treatment methods have a poor quality of wastewater and high treatment process costs. This subject takes the low concentration of lead and copper wastewater from a lead storage battery factory as the research object, and uses the principle of the precipitation of Thiobacillus acidophilus to remove lead and copper from the wastewater. The results show that at a temperature of 30°C, pH of 2.5, and rotation speed of 130r/min, acidophils have the highest removal rate of 74.69%, 38.48% for lead and copper, respectively.

Impact of heavy metals on water quality and indigenous Bacillus spp. prevalent in rat-hole coal mines.

The present study reports pollution evaluation indices employed to assess the intensity of metal pollution in water systems affected by acid mine drainage from rat-hole coal mines prevalent in North-east India. The concentration of seven eco-toxic metals was evaluated from coal mine waters which showed concentration order of Iron (Fe) > Manganese (Mn) > Zinc (Zn) > Chromium (Cr) > Lead (Pb) > Copper (Cu) > Cadmium (Cd). The water samples were acidic with mean pH 2.67 and burdened with dissolved solids (924.8mg/L). The heavy metal pollution index (HPI) and heavy metal evaluation index (HEI) displayed high and medium range of pollution level in majority of the water samples. Statistical correlation suggested strong positive correlation between metals such as Cr with Mn (r = 0.780), Mn with Fe (r = 0.576), Cr with Fe (r = 0.680), Pb with Mn (r = 0.579) and Cr with Pb (r = 0.606), indicating Mn, Pb, Fe and Cr to be major metal contaminants; an unequivocal affirmation of degradation in water quality. The sampled waters had lower heavy metal concentration during monsoon and post-monsoon seasons. The commonly occurring bacterial species Bacillus pseudomycoides and Bacillus siamensis were chosen to understand their behavioral responses toward metal contamination. Findings demonstrated that Bacillus spp. from control environment had low tolerance to metals stress as evident from their MTC, MIC and growth curve studies. The survival of the native isolates across varying pH, salinity and temperature in the coal mine areas suggest these isolates as promising candidates for reclamation of rat-hole coal mining sites.

Environmental Risk Assessment of Petroleum Activities in Surface Sediments, Suez Gulf, Egypt

The present study focuses on the risk assessment of heavy metal contamination in aquatic ecosystems by evaluating the current situation of heavy metals in seven locations (North Amer El Bahry, Amer, Bakr, Ras Gharib, July Water Floud, Ras Shokeir, and El Marageen) along the Suez Gulf coast that are well-known representative sites for petroleum activities in Egypt. One hundred and forty-six samples of surface sediments were carefully collected from twenty-seven profiles in the intertidal and surf zone. The hydrochemical parameters, such as pH and salinity (S‰), were measured during sample collection. The mineralogy study was carried out by an X-ray diffractometer (XRD), and the concentrations of Al, Mn, Fe, Cr, Cu, Co, Zn, Cd, and Pb were determined using inductively coupled plasma mass spectra (ICP-MS). The ecological risks of heavy metals were assessed by applying the contamination factor (CF), enrichment factor (EF), geoaccumulation index (Igeo), pollution load index (PLI), and potential ecological risk index (RI). The mineralogical composition mainly comprised quartz, dolomites, calcite, and feldspars. The average concentrations of the detected heavy metals, in descending order, were Al &gt; Fe &gt; Mn &gt; Cr &gt; Pb &gt; Cu &gt; Zn &gt; Ni &gt; Co &gt; Cd. A non-significant or negative relationship between the heavy metal concentration in the samples and their textural grain size characteristics was observed. The coastal surface sediment samples of the Suez Gulf contained lower concentrations of heavy metals than those published for other regions in the world with petroleum activities, except for Al, Mn, and Cr. The results for the CF, EF, and Igeo showed that Cd and Pb have severe enrichment in surface sediment and are derived from anthropogenic sources, while Al, Mn, Fe, Cr, Co, Ni, Cu, and Zn originate from natural sources. By comparison, the PLI and RI results indicate that the North Amer El Bahry and July Water Floud are considered polluted areas due to their petroleum activities. The continuous monitoring and assessment of pollutants in the Suez Gulf will aid in the protection of the environment and the sustainability of resources.

A comprehensive evaluation of the potential of semiterrestrial isopods, Ligia exotica, as a new animal food

The semiterrestrial isopod, Ligia exotica represents one of the oldest documented species introductions of marine organisms and is known as an intermediate form between marine and strictly terrestrial isopods. In order to explore the potential value of Ligia as an animal food source, this study focused on the growth rate under laboratory rearing conditions and conducted a detailed analysis of the overall nutrient content of the species in comparison to two other marine food media (krill and fish meal). Evaluation of the growth rate of juveniles suggests it is a relatively fast-growing species of the Ligiidae family. The essential amino acids content Ligia meal is the lowest amongst the three studied media but the proportion of flavor amino acids, and in particular taurine, was higher. The most restricted amino acids of isopod meal are methionine and cysteine. The significantly unbalanced amino acid composition of Ligia meal may affect the absorption and utilization by consumers. In terms of fatty acids, the total polyunsaturated fatty acids in the isopod is very low. A total of 12 vitamins were examined. The VK1, VE, VB2, VB3, VB5 content of isopod meal were significantly higher than those of krill meal and fish meal. Similarly, most of the 11 mineral elements are highest in the isopod meal. Ligia therefore offers potential as an alternative natural food source in animal given the growth rate under culture and the overall nutrient content. But Ligia collected in most of the field would be deemed unfit for human consumption because of the relatively low nutritional value and heavy metal content exceeding the provided standard. Further study is warranted to elucidate the biological characteristics of isopods and how its diet is reflected in its nutritional value to consumers.

Cultivation of microalgae in palm oil mill effluent (POME) for astaxanthin production and simultaneous phycoremediation

Haematococcus pluvialis and Chromochloris zofingiensis are freshwater microalgae exploited to produce the high-value carotenoid, astaxanthin. Nonetheless, a copious amount of freshwater is consumed for microalgae cultivation, thereby raising concerns regarding sustainable astaxanthin production. Characterization of palm oil mill effluent (POME) obtained from a commercial facility in southern Sri Lanka revealed high concentrations of total nitrogen (TN), total phosphorous (TP) and low concentrations of heavy metals, thus showcasing the potential of POME as an alternative growth media for astaxanthin production. Hence, H. pluvialis and C. zofingiensis were cultivated in 2.5%, 5.0% and 7.5% POME with the aim of producing astaxanthin, reducing freshwater consumption, and simultaneous phycoremediation. H. pluvialis exhibited better adaptability to higher POME concentrations, with its maximum astaxanthin yield (22.43 mg/L) achieved in 7.5% POME, whilst reducing specific freshwater consumption for astaxanthin production by 43%. However, only moderate performance in phycoremediation was achieved, with removal of 50.9% chemical oxygen demand (COD), 49.3% total nitrogen and 69.4% total phosphorous at rates of 3.95 mg/L/d, 0.50 mg/L/d and 0.11 mg/L/d respectively. The heavy metal content in biomass was within permissible limits. Characterization of astaxanthin-extracted residual biomass of H. pluvialis revealed possible applications as protein-rich animal feed or feedstock for biofuel production. Results indicated that POME generated in Sri Lankan palm oil mills has the potential to be utilized for large scale production of microalgal astaxanthin. Nevertheless, pilot-scale experiments, product toxicology evaluation and techno-economic feasibility studies are required prior to implementation of large-scale POME-integrated astaxanthin production facilities.

Heavy metals uptake and its impact on the growth dynamics of the riparian shrub Ricinus communis L. along Egyptian heterogenic habitats.

Heavy metals are well known for their toxicity and become significant environmental pollution with a continually rising technology and public outcry to ensure the safest and healthiest environment. The present study aims to investigate the uptake capability of heavy metals and its impact on the growth dynamics of Ricinus communis L. (castor bean), along various habitats in Qalyubia Province, Egypt. Three composite plants and soil samples were collected from four different habitats: urban (residential area), canal banks, field edges, and drain banks. The samples were analyzed for nutrients and heavy metals. At the same time, forty quadrats (5 × 5 m) were selected to represent the micro-variations of castor bean in the selected habitats to determine its growth criteria and normalized vegetation index (NDVI). The lowest size index, volume, and number of leaves of castor bean were recorded along canal banks and they were characterized by high soil heavy metal concentration, especially Zn, Cu, and Ni, while the highest values were recorded along field edges with lower heavy metal concentration. Moreover, the NDVI indicated that castor bean from most studied habitats, except field edges, was healthy population. This study revealed that the leaves collected from all habitats were considered to be toxic with Cu. The bioconcentration factor (BF) of the investigated heavy metals was greater than 1. The BF order for heavy metals uptake by castor bean leaves was Fe > Ni > Mn > Cu > Zn. Consequently, the species selected in the present study can be used as a biomonitor of these heavy metal polluted soils. Moreover, it could be used as a phytoremediator, taken into consideration its use in all medicinal purposes.

Assessment of soil washing for heavy metal contaminated paddy soil using FeCl3 washing solutions.

In this study, soil washing is applied for the remediation of heavy-metal (Pb, Cu and Zn) contaminated paddy soil located near an abandoned mine area. FeCl3 washing solutions were used in bench-scale soil washing experiments at concentrations in the range of 0.1 to 1M. The strong acid, HCl was also used in this study for comparison. The washing process was performed at room temperature, mixing at 200 RPM for 1h and a liquid to solid ratio of 2. A sequential extraction technique was performed to evaluate the chemical fractions of Pb in the soils. The soil washing effectiveness was evaluated and compared against regulations applicable to residential districts (Korean warning standards). The soil washing results showed that the heavy metal concentrations were reduced with increasing concentrations of FeCl3. Moreover, the lowest heavy metal concentrations were obtained with a 1M FeCl3 washing solution. In the case of Pb removal, a 0.3M FeCl3 washing solution was required to comply with the Korean warning standard of 200mg/kg. The lowest Pb concentration of 117mg/kg was obtained with 1M FeCl3. Similar washing results were also obtained with HCl. The initial total concentrations for Cu and Zn were below the Korean warning standards of 150 and 300mg/kg, respectively. Consequently, the reduction in Cu and Zn from the contaminated paddy soil using FeCl3 washing solutions was rather limited. The sequential extraction results showed that the exchangeable and weak acid-soluble fractions of Pb were significantly reduced upon FeCl3 washing.

The Santorini Volcanic Complex as a Valuable Source of Enzymes for Bioenergy

Marine microbial communities are an untapped reservoir of genetic and metabolic diversity and a valuable source for the discovery of new natural products of biotechnological interest. The newly discovered hydrothermal vent field of Santorini volcanic complex located in the Aegean Sea is gaining increasing interest for potential biotechnological exploitation. The conditions in these environments, i.e., high temperatures, low pH values and high concentration of heavy metals, often resemble harsh industrial settings. Thus, these environments may serve as pools of enzymes of enhanced catalytic properties that may provide benefits to biotechnology. Here, we screened 11 metagenomic libraries previously constructed from microbial mat samples covering the seafloor and the polymetallic chimneys of Kolumbo volcano as well as mat samples from Santorini caldera, to mine, in silico, genes associated with bioenergy applications. We particularly focused on genes encoding biomass hydrolysis enzymes such as cellulases, hemicellulases and lignin-degrading enzymes. A total of 10,417 genes were found for three specific groups of enzymes—i.e., the endoglucanases, the three different beta-glucosidases BGL, bglX and bglB, and the alpha-galactosidases melA, and rafA. Overall, we concluded that the Santorini–Kolumbo volcanic ecosystems constitute a significant resource of novel genes with potential applications in bioenergy that deserve further investigation.

The Evolution of the Waters Chemical Composition in the Areas of Lead-Zinc Deposits Mining in East Transbaikalia

A feature of the studied objects is the formation of waters under conditions of combination in the mineral composition of the tailings of sulfide and carbonate mineralization. The studied drainage waters are mainly fresh (salinity 0.33-1.82 g/L), neutral and alkaline (pH 7.25-8.30). They belong to the bicarbonate, sulfate-bicarbonate, bicarbonate-sulfate and sulfate magnesium-calcium and calcium-magnesium chemical types. Arsenic, zinc, cadmium, lead, antimony and manganese in the microelement composition of drainage waters are predominant. Drainage waters of lead-zinc deposits are characterized by a significant excess of the heavy metals concentrations (As, Zn, Cd, Pb, Sb, Mn, Mo, U, La, Se) over the average composition of leaching zone waters, with a maximum for arsenic – more than 800 and for zinc – 200 times. The waters are saturated with respect to secondary carbonates and arsenates, which indicates the existence of thermodynamic conditions for the removal from the solution of Ca, Mg, Cu, Zn, Pb, As into the solid mineral phase. The neutralizing effect of host rocks carbonates and ore bodies carbonates causes a neutral reaction of waters and low heavy metal concentration.

Assessment of the Composition of Forest Waste in Terms of Its Further Use.

This paper presents the results of the analysis of the chemical composition and content of heavy metal contamination in forest logging residues, in order to assess the possibility for their further utilisation. The samples were divided into 9 groups, which included coniferous tree cones, wood, and other multi-species logging residues. The elementary composition, ash content, and calorific value were determined as energy use indicators for the samples. Additionally, the content of heavy and alkali metals, which may affect combustion processes and pollutant emissions, was tested. The high content of heavy metals may also disqualify these residues for other uses. The research shows that the test residues are suitable for energy use due to their high calorific value and low content of heavy metals. However, an increased ash content in some samples and the presence of alkali metals, causing high-temperature corrosion of boilers, may disqualify them as a potential fuel in the combustion process. The forest residues may be used in other thermal processes such as pyrolysis or gasification. A low content of heavy metals and a high content of organic matter permit the use of these residues for the production of adsorbents or composite materials.

A polymer - zeolite composite for mixed metal removal from aqueous solution.

Heavy metals become inevitable pollutants that are toxic to life. Lots of treatment methods are available; adsorption is a cheap option. Metals are mostly found as mixtures in wastewaters. Taking this into account, a natural composite adsorbent aims to remove multiple heavy metals (Pb2+, Cu2+, Cd2+). Alginate was combined with clinoptilolite to form alginate - clinoptilolite (A-C) beads. First, factors influencing the removal efficiency of metals were investigated. Then, continuous column experiments were performed to evaluate the real application potential of the adsorbent. A-C beads preferably adsorbed Pb2+. Batch experiments showed metal uptake reached equilibrium after 24 hours and kinetics were compatible with the first-order. Also, pH values near neutral levels were observed to increase heavy metal removal. On the other hand, adsorption equilibrium was well described by the Langmuir model for Cu2+ and Cd2+ and by the Freundlich model for Pb2+. The highest heavy metal uptake was calculated as 2,145 mg /g A-C beads for Pb2+. Continuous column operations were suggested to apply low flow rates (<2 mL/min) and heavy metal concentration (<10 mg/L) for effectiveness. A-C beads can be a good candidate for mixed heavy metal removal composed of environmentally friendly and low-cost materials.

Trophic status, phytoplankton diversity, and water quality at Kafr El-Shinawy drinking-water treatment plant, Damietta

Abstract This work aims to study the seasonal fluctuation in physicochemical characteristics, trophic status, and some pollutants influencing phytoplankton diversity, and water quality at a compact Kafr El-Shinawy drinking-water treatment plant, Damietta – Egypt seasonally during 2018. Phytoplankton distribution was affected by the trophic status of water, level of pollutants, and physicochemical treatment processes of water. The predominance of phytoplankton species, especially Aphanizomenon flos aquae (Cyanophyta), Gomphosphaeria lacustris (Cyanophyta), Microcystis aeruginosa (Cyanophyta), Nostoc punctiforme (Cyanophyta), Oscillatoria limnetica (Cyanophyta), Pediastrum simplex (Chlorophyta), and Melosira granulata (Bacillariophyta) in treated water was much less than that in raw water. Trihalomethanes (THMs) levels in treated waters were higher than in raw water, while lower concentrations of heavy metals were recorded in treated water. Intracellular levels of microcystins were lower, whereas the extracellular levels were higher in treated water than raw water, and the former recorded the highest level in raw water during summer. Hence, the levels of dissolved microcystins and THMs in treated water were higher especially during summer, the season of luxurious growth of Microcystis species. Trophic state index (TSI) was relatively high in raw water compared with treated water due to high concentrations of nutrients (total-P, total-N, nitrite, nitrate, and ammonia) in raw water.

A national wide evaluation of heavy metals pollution in surface sediments from different marginal seas along China Mainland

Sediments, both act as sink and source of heavy metals, played an important role in their global cycle. In coastal ecosystems, heavy metals will be deposited and accumulated in sediments via complex chemical, physical and biological processes and pose potential risks to ecosystems. In the past 3 decades, studies have reported the heavy metal contamination in different ecosystems along China Mainland on local or regional scales, and their concentrations, distribution patterns, sources, as well as ecological risks showed large spatial variabilities. Here, the concentrations of heavy metals in different coastal ecosystems along China Mainland were reviewed from more than 150 published papers. Their distributions patterns, sources and the ecological risks were investigated. As a result, Cr, Cu, Ni, Zn and Pb were the most reported heavy metals with high concentrations observed in nearshore estuaries and coastal bays, which is closely related to the intensive human activities in nearshore areas. Whereas, low heavy metal concentrations were observed in offshore sediments. Source identification suggested that the heavy metals in coastal ecosystems were mainly from phosphate fertilization, atmospheric deposition, weathering and industrial activities. Results from ecological risk assessment indicated that there were high ecological risks in some pollution hot-spots, associated with their high As, Cd, Zn and Pb concentrations.

The temporal variability of hydrothermal activity of Wocan hydrothermal field, Carlsberg Ridge, northwest Indian Ocean

The Wocan is a basalt-hosted hydrothermal field on the slow-spreading Carlsberg Ridge (CR), northwest Indian Ocean. It consists of two hydrothermal sites: Wocan-1 which is active, and Wocan-2 which is inactive. Three push-cores collected by the manned submersible Jiaolong from these two sites were investigated on their mineralogy, geochemistry, Pb-Sr isotopes, and chronology to understand the characteristics of hydrothermal sediments and their hydrothermal history. Core JL125-S17 (26-cm long) was collected from the Wocan-1 site with its lithology characterized by metalliferous sediments, mainly composed of sulfides, sulfates, Fe-oxides, and Fe-oxyhydroxides. Cores JL123-S03 (18-cm long) and JL124-S04 (20 cm long) were retrieved from the Wocan-2 site, mainly composed of calcareous oozes. Geochemically, Wocan-1 sediments exhibit strong metal and S enrichment. Ag, As, Cd, Co, Cu, Fe, Mg, Pb, Zn, and S are mainly incorporated into sulfides, while As, Ga, Mo, P, U, and V are mainly scavenged from seawater by Fe-Mn oxyhydroxides. In contrast, Wocan-2 sediments are rich in Ca and have much lower heavy metal content. The temporal variations of hydrothermal metal fluxes, which corrected for lithogenic input with Ti show that the intensity of hydrothermal activity at the Wocan-1 site has been extremely strong over the past ~1069 years, with hydrothermal Fe (FeH) fluxes varying from 9483 to 10834 mg·cm−2·kyr−1. During this period, 699–1069 yr BP and 0–411 yr BP represent two stages of increased hydrothermal activity. The Wocan-2 site has been inactive since 4864 ± 114 years before present (yr BP) but the cores still contained weak hydrothermal signatures evidenced by a slightly elevated flux of FeH at the base of the cores, which could be explained by the mineralization of low-temperature diffuse flow and distal plume fall-out from Wocan-1.

Comparative Effects of Organic and Conventional Cropping Systems on Trace Elements Contents in Vegetable Brassicaceae: Risk Assessment

Genotypes selected from 3 plant species (Brassica rapa, Eruca vesicaria and Sinapis alba) belonging to the Brassicaceae family were chosen to compare the concentrations of 9 inorganic elements (Cd, Co, Cr, Cu, Fe, Ni, Mn, Pb and Zn) in these varieties, that were grown under both conventional and organic conditions during two agricultural seasons (2018/2019 and 2019/2020) on two different experimental farms (Farm I and Farm II). We found that, together with agriculture practices, the inorganic element concentrations in Brassicas depended on many other factors, including soil characteristics. However, there were no conclusive results indicating a lower heavy metal content or a higher nutritionally beneficial trace elements content in vegetables grown under organic agriculture. Finally, a probabilistic assessment (@Risk) derived from the consumption of 150–200 g of these vegetables showed that organic Brassicas fulfill in comparison with the conventional ones, similar Dietary Reference Intakes (DRI) percentages for Co, Cr, Cu, Fe, Mn and Zn. Regarding heavy metals (Cd, Ni and Pb), we only found slight differences (mainly in the case of Pb) in the Tolerable Intakes (TI) between both cropping systems.