Increasing Metal Concentration Research Articles

Electrical and Structural Properties and Facile Synthesis of Alumina Modified by Metal Nanoparticles

Abstract: Alumina catalysts modified by platinum and nickel nanoparticles were prepared by chemical reduction and microwave stimulated techniques, and their relationship to electrical properties was studied. The structural and textural properties of such nanocatalysts were examined by XRD, DSC-TGA, N2 physisorption and TEM. The electrical properties of nanoparticle catalysts as functions of the increase of metal concentration are discussed. The electrical measurements were performed in the frequency domain. Three mechanisms are suggested for the electrical behaviour of all systems. The increment observed in conductivity with extra amounts of metal may be due to the expansion in the movement ability of uncontrolled transporters that disperse in the pores of the material. Upon arrival at the electrodes, these transporters evacuate their charge and, accordingly, increase the dispersion impedance. The results show high thermal stability up to 1000 °C. The isotherms obtained display almost the same behaviour for samples prepared by both the microwave and the chemical method. This may be linked to high-dispersion particles and their nanoscale metal concentration. The XRD results exhibit small diffraction line characteristics.

Analysis of Trace Element Concentrations and Antioxidant Enzyme Activity in Muscle Tissue of the Atlantic Sharpnose Shark, Rhizoprionodon terraenovae.

Metals occur naturally in the environment; however, anthropogenic practices have greatly increased metal concentrations in waterways, sediments, and biota. Metals pose health risks to marine organisms and have been associated with oxidative stress, which can lead to protein denaturation, DNA mutations, and cellular apoptosis. Sharks are important species ecologically, recreationally, and commercially. Because they occupy a high trophic level, assessing muscle tissue metal concentrations in sharks may reflect metal transfer in marine food webs. In this study, concentrations of cadmium, copper, lead, nickel, selenium, silver, and zinc were measured in the muscle of Rhizoprionodon terraenovae (Atlantic sharpnose shark) from 12 sites along the coast of the southeastern United States. Activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase) also were examined in the muscle tissue of R. terraenovae. A total of 165 samples were analyzed, and differences in trace element bioaccumulation and enzyme activity were observed across sites. R. terraenovae samples collected from South Florida and South Carolina had the highest cumulative trace element concentrations whereas those collected from North Carolina and Alabama had the lowest cumulative concentrations. Trace element concentrations in shark muscle tissue were significantly correlated to antioxidant enzyme activity, particularly with glutathione peroxidase, suggesting that this enzyme may serve as a non-lethal, biomarker of metal exposure in R. terraenovae. This is one of the most extensive studies providing reference levels of trace elements and oxidative stress enzymes in a single elasmobranch species within the U.S.

ИЗМЕНЕНИЕ КОНЦЕНТРАЦИЙ ТЯЖЕЛЫХ МЕТАЛЛОВ В КОМПОНЕНТАХ МАЛОЙ РЕКИ (НА ПРИМЕРЕ ОСУШИТЕЛЬНОЙ МЕЛИОРАЦИИ)

Актуальность исследованиязаключается в необходимости оценки таких природныхкомпонентов малой реки,как донные отложения и водные растения, которые способны аккумулировать различные поллютанты, поступающие с территории водосбора, и могут служить индикатором экологического состояния загрязнения воды в реке. Цель:анализ изменения концентраций тяжелых металлов в компонентах малой реки (на примере осушительной мелиорации). Объекты:поверхностные воды, донные отложения и водные растения, подверженные влиянию осушительной мелиорации. Методы:фильтрация проб воды через мембранные фильтры с диаметром пор 0,45 мкм для раздельного определения растворенной и взвешенной форм тяжелых металлов. Отбор проб донных отложений штанговым дночерпателем Гр-91 на глубине 25 см от поверхности залегания. Кислотное разложение проб донных отложений и растительности в микроволновой системе «Mars-6», измельчение в планетарной мельнице «Pulverisette 6», определение тяжелых металлов методом атомно-абсорбционной спектрометрии на спектрометре «Solaar 6M». Результаты.Под влиянием осушения в поверхностных водах происходит увеличение концентраций растворенных и взвешенных форм тяжелых металлов, в особенности Fe и Pb, превышающих значения предельно-допустимых концентраций в 3 раза. В донных отложениях происходит накопление тяжелых металлов в 1,5–2 раза выше по отношению к верхнему течению реки, однако при изменении химических и гидрологических параметров среды металлыпереходят опять в водоток, являясь источником вторичного загрязнения. Наиболее интенсивные процессы осаждения рассчитаны для Fe (lgКраспр=5,06), Pb (lgКраспр=4,76), а также для Zn (lgКраспр =4,60). Средний характер седиментации прослеживается для Mn и Cu (lgКраспр=3,36). Для Ni коэффициент имеет минимальное значение (lgКраспр=2,82), что говорит об обратных процессах миграции металла из донных отложений в воду. Осушительная мелиорация, меняя гидрохимические и гидрологические характеристики водотоков, приводит к увеличению концентраций тяжелых металлов в макрофитах в 2–3 раза.

Effects of sludge on heavy metals release from peppermint-planted soils during time as assessed by DGT technique

ABSTRACT The desorption kinetics of Cd, Pb, and Zn was investigated as a function of sewage sludge amount (0, 10, and 30 g kg−1), incubation time length (30 and 120 days) and plant cultivation (Mentha pipertia L.) using diffusive gradient in thin-film (DGT) technique. Kinetic parameters result of studied metals suggested that an increase in desorption rate constant (K−1), distribution coefficient (Kd), and resupply (R) values as well as a decrease in response time (Tc) over time in planted soils treated with 30 g kg−1 sewage sludge, which then resulted in a significant increase in plant metals concentrations. In 10 g kg−1 sewage sludge treated soils, a reverse trend was observed for the parameters over time (except for Kd values of Cd). Statistical analyses showed that Zn and Pb desorption rates were more influenced by dissolved organic carbon (DOC) compared to pH. For Cd, there was a significant agreement between K−1 and clay content. It is concluded that unlike Zn and Pb, the decreased R value of Cd that was reflected by the increased Tc and the reduced K−1 after extended incubation period may be the main factor limiting the Cd availability.

Comparison of Sensitivity of Tropical Freshwater Microalgae to Environmentally Relevant Concentrations of Cadmium and Hexavalent Chromium in Three Types of Growth Media.

Sensitivity of tropical freshwater microalgae (Mesotaenium sp., Chlorococcum sp. and Scenedesmus sp.) to environmentally relevant concentrations of hexavalent chromium (Cr6+) and cadmium (Cd2+) was compared individually in three growth media viz. Bold's Basal Medium (BBM), Test Medium 1 (TM1) and Test Medium 2 (TM2) based on fluorescence reduction. Free metal content of growth media was determined by Visual MINTEQ (version 3.1). After 24h, relative fluorescence of microalgae in the three media decreased with increased metal concentration showing a concentration dependent graded toxicity response. All microalgae were more sensitive to the metals when grown in TM1, when compared, more sensitive to Cr6+ than Cd2+. Metal speciation indicated that TM1 and TM2 media have higher percentage of bioavailable Cd2+ than BBM, and chromium was present mainly as CrO42- and HCrO4-. The results suggest that the TM1 medium is more suitable under short term exposure of microalgae to metals in environmental monitoring.

Bioremoval of heavy metals from polluted soil by Schoenoplectus litoralis (Schrad.) Palla and Cyperus rotundus L. (Cyperaceae)

The present work aimed to assess the ability of plant species namely, Schoenoplectus litoralis and Cyperus rotundus belonging to family Cyperaceae in bioremoval of heavy metals from polluted soil by As, Pb, Cd, Zn. Soil planted with both plant species was regularly irrigated (twice a week) by water containing different concentrations of 10, 20, 30, 40, and 50 ppm of the metals in a laboratory experiment. The tested metals residues were determined in the shoot and root system of plants after 45 days and expressed as mg/g dry weight of the plant. C. rotundus had a high power for absorbing and accumulating heavy metals from the contaminated soil by higher rate by roots than by shoot system (root: As 183 mg/g, Pb 82 mg/g, Cd 122 mg/g, and Zn 137 mg/g, shoot: As 145 mg/g, Pb 512 mg/g, Cd102 mg/g, and Zn 110 mg/g ). S. litoralis absorbed and accumulated heavy metals from soil in less amount (root: As 148 mg/g, Pb 46 mg/g, Cd 113 mg/g, and Zn 127 mg/g, shoot: As 132 mg/g, Pb 44 mg/g, Cd 100 mg/g, and Zn 105 mg/g). The bioaccumulation power increased with the increase of heavy metal concentrations in soil and with the time exposure in the both plant species.

Electrocoagulation Treatment of Electroplating Wastewater: A Review

Electrochemical methods such as electrocoagulation (EC), electrooxidation (EO), and electroreduction (ER) are promising technologies to remove organics and heavy metals contained in industrial effluents discharged from numerous industries such as electroplating, textile, and metal processing. EC is widely applicable to treat wastewater that has a wide range of pollutants as well as being applicable to treating organic pollutants having a chemical oxygen demand (COD) range of 1,000–13,000 mg/L, and metals concentration in the range of 10–2,500 mg/L depending on the type of pollutants/metals. Several parameters such as pH, current density, electrode gap, electrolysis time, and agitation speed plays a major role during EC. Various laboratory results show that EC works effectively in the pH range 2–8, current density 20–200 A/m2, electrode gap 1.5–3 cm, electrolysis time 10–150 min, and stirrer speed 30–200 rpm for the reactor size 1–2.5 L depending on the type of wastewater/effluent. Moreover, this process has been proved to be versatile and environmentally friendly. This review mainly focuses on the separation of heavy metals from electroplating effluent (EPE), including other pollutants removal from various industrial effluents such as textile, distillery, paint, and tannery. EC operation is oriented on the supply of direct current in metal electrodes and, consequently, metal ions released into the solution. This results in an increased metal concentration in the solution that finally precipitates as metal hydroxides along with pollutants. Numerous techniques are available to treat heavy metals bearing effluent, which includes precipitation, adsorption, bioadsorption, ion exchange, and membrane separation. These methods have several limitations in term of high operating costs and a large amount of sludge generation, while the EC process has several advantages over conventional technologies such as requirement of less external chemicals, easier installation, lower secondary pollutants formation, odor and color removal, and lower residence time. However, high electricity consumption due to formation of oxide film on the surface of the electrode is a major drawback of this process because oxide film works as an electric insulator. Overall, the EC method has wide potential to treat different kinds of effluents.

Assessing the Distribution and Concentration of Heavy Metals in Soils of an Agricultural Frontier in the Brazilian Cerrado

The continuous use of agricultural inputs for grain, fiber, and energy production in the Brazilian savannah can increase heavy metal (HM) concentrations in the soils. In this context, we aimed to determine the natural concentrations and establish the quality reference values (QRVs) of HMs in reference soils of a sedimentary watershed under native vegetation in one of the latest agricultural frontiers of Brazil in order to assess the impact of cultivation on the metal concentrations in cropped soils. Additionally, we studied the spatial variability of HMs and the efficiency of the multivariate analyses to distinguish between natural and anthropogenic sources of metals in the soils. Thirty-two and 30 composite soil samples were collected in areas under agricultural exploration and natural vegetation with minimal anthropic interference (low impact areas), respectively. The QRVs established could be ranked as follows (mg kg−1): Fe (18,700) > V (47.83) > Cr (43.44) > Ba (9.11) > Pb (2.73) > Ni (0.80) > Cu (0.74) > Zn (0.46) > Mo (0.34) > Cd (0.05) > Sb ( Co (< 0.00008). Natural concentrations observed in non-anthropogenic soils are lower than those found in other regions, with the exception of Cr. Also, we found that the mean concentrations of Cd, Cu, Cr, Mo, Mn, Ni, Sb, V, and Zn in agricultural soil were far higher than their background values of the watershed topsoil. Based on our findings, the increased metal concentration in the agricultural soils increases the ecological risk. On the other hand, the mean metal concentrations remain close to the prevention value for soils established by the Brazilian Council for the Environment for agricultural land, which indicates that these areas require monitoring to guarantee foodstuff safety. Our results are useful for public policies not only in the studied area but also worldwide where soils are derived predominantly from sedimentary rocks such as sandstones, siltstones, shales, and limestones.

Copper and mercury induced oxidative stresses and antioxidant responses of Spirodela polyrhiza (L.) Schleid

Duckweed is recognized as a phytoremediation aquatic plant due to the production of large biomass and a high level of tolerance in stressed conditions. A laboratory experiment was conducted to investigate antioxidant response and mechanism of copper and mercury tolerance of S. polyrhiza (L.) Schleid. To understand the changes in chlorophyll content, MDA, proline, and activities of ROS-scavenging enzymes (SOD, CAT, GPOD) during the accumulation of Cu+2 and Hg+2, S. polyrhiza were exposed to various concentrations of Cu+2 (0.0–40 μM) and Hg+2 (0.0–0.4 μM). antioxidant activity initially indicated enhancing trend with application of 10 μM Cu+2; 0.2 μM Hg+2 (SOD), of 20 μM Cu+2; 0.2 μM Hg+2 (CAT) and of 10 μM Cu+2;0.2 μM Hg+2 (GPOD) and then decreased consistently up to 40 μM Cu+2 and 0.4 μM Hg+2. In the experiment chlorophyll and frond multiplication initially showed increasing tendency and decreased gradually with the application of increased metal concentration. Application of heavy metal has constantly enhanced proline and MDA content while the maximum increase was observed with the application of 40 μM Cu; 0.4 μM Hg for proline and MDA respectively. The upregulation of antioxidant enzymes and proline reveals that S. polyrhiza has strong biochemical strategies to deal with the heavy metal toxicity induced by the accumulation of Cu+2 and Hg+2.

Concentrations and sources of heavy metals in shallow sediments in Lake Bafa, Turkey

The concentrations and sources of heavy metals in shallow sediments in Lake Bafa were investigated. The concentrations of nine heavy metals and the total organic carbon content in sediment samples were determined for between Summer 2015 and Spring 2016. The mean contents of heavy metals were in decreasing order Fe > Mn > Ni > Cr > Zn > Cu > Co > Pb > Cd. Sediment quality guidelines indicate that Cr, Cu, and Ni pose a considerable threat to the aquatic ecosystem in Lake Bafa. Site L3 was found to be contaminated with Cd, Cr, and Ni, and the pollution load indices suggest that these metals had anthropogenic sources. The sediment samples were notably enriched with Cd and Ni. There is no consistent trend for seasonal effect in terms of the sample locations. However, at all sampling points, an increase in heavy metal concentrations was observed in the autumn. The results of a multivariate analysis indicate that the sources of Co, Cu, Fe, Mn, Pb, and Zn were all natural, the sources of Cd were anthropogenic, and the sources of Ni and Cr were both anthropogenic and natural. These results highlight that Cd, Cr, and particularly Ni represent the most serious threat in terms of heavy metal pollution in the ecosystem of the lake.

Study on Catalyst Deactivation During the Hydrodeoxygenation of Model Compounds

To address the pressures associated with an increasing energy demand and rising cost of liquid fuel production, alternative feedstocks are being developed. One such potential replacement is bio-oils, which are derived from biomass, however the oil produced is often chemically unstable, corrosive and has low heating values due to the high oxygen content. Thus, an upgrading process is required to lower the oxygen content, with catalytic hydrodeoxygenation being one such technology currently being developed, with mechanistic studies commonly completed utilising model compounds. The current study examines factors that influence catalyst deactivation during hydrodeoxygenation of common bio-oil model compounds over zeolite-supported nickel catalysts, indicating the contribution of functional groups on the formation of condensed-ring products and catalyst deactivation. It was determined that phenolic-hydroxyl groups present in model compounds can facilitate catalyst deactivation through the formation of condensed-ring compounds, identified through decreased cycloalkane yields, causing blockage of catalyst pores. Conversely, when toluene, cyclohexanol and anisole were used as model compound feeds, there were no notable changes in cycloalkane yields, indicating aromatic, alkyl–OH and aromatic–OCH3 have negligible effect on catalyst deactivation. The effect of catalyst metal loading was also examined, and while increased metal content enhanced cyclohexane yields, so to was the formation of condensed-ring products, suggested to be the result of an increased concentration of surface cyclohexane carbocations. Modifications to reaction conditions was studied, with catalyst activity and stability found to improve with increasing reaction temperatures up to 230 °C. Based on the product distributions observed, a coupling reaction pathway (leading to the formation of condensed-ring products and cycloalkanes) is proposed as the hydrodeoxygenation mechanism.

Effect of bioaugmentation on digestate metal concentrations in anaerobic digestion of sewage sludge.

This study examined the influence of bioaugmentation on metal concentrations (aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, molybdenum, nickel and zinc) in anaerobically digested sewage sludge. To improve the digestion efficiency, bioaugmentation with a mixture of wild-living Archaea and Bacteria (MAB) from Yellowstone National Park, USA, was used. The total concentration of all metals was higher in the digestate than in the feedstock. During anaerobic digestion, the percent increase in the concentration of most of metals was slightly higher in the bioaugmented runs than in the un-augmented runs, but these differences were not statistically significant. However, the percent increase in cadmium and cobalt concentration was significantly higher in the bioaugmented runs than in the un-augmented runs. At MAB doses of 9 and 13% v/v, cadmium concentration in the digestate was 211 and 308% higher than in the feedstock, respectively, and cobalt concentration was 138 and 165%, respectively. Bioaugmentation increased over 4 times the percentage of Pseudomonas sp. in the biomass that are able to efficiently accumulate metals by both extracellular adsorption and intracellular uptake. Biogas production was not affected by the increased metal concentrations. In conclusion, bioaugmentation increased the concentration of metals in dry sludge, which means that it could potentially have negative effects on the environment.

Natural Flocculant VS Chemical Flocculant Where Is Better To Used In Wastewater Treatment

Nowadays, Coagulation-flocculation process is still common method were used in both large and small scale in wastewater treatment. It’s process an effective method as pretreatment. Flocculant (natural aid) can use many material is an important factors for coagulation-flocculation process. Many materials were used for coagulant-flocculant aid, but typically can be divided into chemical, grafted and or natural aid. Chemical flocculant was made from monomers formed to electrolytes polymers, that is cationic polymers, anionic polymers or non-ionic polymers, such as polyacrylamide have been widely used for decades. Grafted flocculants were synthesized by combining the properties of polymers, both synthetic and natural by ‘connect to’ method, such as Polydiallyldimethylammonium chloride (polyDADMAC or polyDDA). Whereas natural flocculant can be derived from seed of plantago, ovata, moringa, olifiera, etc. Some natural starch can be used as natural aid also. The main advantages of natural flocculant are their renewability, biodegradability, nontoxicity and relative costeffectiveness. but for development in the future constrained by some challanges, Natural flocculant tend to have shorter live which caused by biodegradability of active component, floc will loose. Besides that, chemical flocculants are used because of their easy use. However, in many studies, the usage of chemical flocculant will have an important environmental impact, such as, producing toxic sludge containing metal hydroxides which causes problems with their disposal and increasing metal concentrations (eg aluminum) which can have an impact on the sustainability of human health. This paper will review some chemical flocculant and natural flocculant also tell about environmental affect, both disadvantages and potential which is better used to wastewater treatment.

Urinary metals and incident diabetes in midlife women: Study of Women’s Health Across the Nation (SWAN)

IntroductionEnvironmental exposure to metals may play a role in the pathogenesis of diabetes; however, evidence from human studies is limited. We prospectively evaluated the associations of 20 urinary metal concentrations...

Organic polyelectrolytes as the sole precipitation agent in municipal wastewater treatment

In municipal wastewater treatment, inorganic coagulants (IC), e.g. polyaluminium chloride (PAC), are normally used to remove pollutants such as dissolved and particulate nutrients, in a process called coagulation/flocculation. However, IC use has been linked to issues e.g. in effluent water post-treatment, sludge management and disposal (IC increase sludge volume and metal concentrations in sludge), etc., raising uncertainties about their overall cost-efficiency and environmental benefits. In this study, the suitability of organic coagulants (OC) as sole precipitation agents to replace IC (PAC) was investigated. A total of 10 synthetic (i.e. polyDADMACs and polyamines) and semi-natural (chitosan, starch, and tannin-based) OC products were tested in treatment of samples from primary sedimentation and secondary sedimentation stages of municipal wastewater treatment, and their performance was compared with that of PAC. The study was conducted using the jar test methodology. The coagulants were tested for their ability to remove target pollutants (e.g. BOD7, COD, SS, tot-P, PO4-P, tot-N) and form rapidly settling flocs. In general, higher (up to 60%) coagulant doses were needed in treatment of secondary wastewater samples than primary samples. In comparison with the OC doses required for effective treatment, the PAC doses were higher (up to 80%). In treatment of secondary wastewater samples, OC with high molecular weight (MW) and high charge density (CD) (e.g. pAmine1) achieved best removal of target pollutants (e.g. 72% SS, 87% PO4-P, 88% BOD7), followed by PAC. In treatment of primary wastewater, PAC performed best (removing e.g. 96% SS, 96% PO4-P), closely followed by chitosan and polyamine products. Based on these results, polyamine products with high MW and (very) high CDs have the potential to act as the sole precipitation agent in both primary and secondary stages of municipal wastewater treatment. Further research is needed to determine the effect of residual coagulant on downstream water and sludge treatment processes (e.g. activated sludge process, sludge dewatering, etc.).

Differential Growth and Metal Accumulation Response of Brachiaria Mutica and Leptochloa Fusca on Cadmium and Lead Contaminated Soil

ABSTRACT This work aims to assess growth, physiology, and metal uptake response of Brachiaria mutica and Leptochloa fusca under different contamination levels of Cd (10 and 50 mg kg−1) and Pb (50 and 250 mg kg−1) stress. Results of pot trial showed increasing metal concentration affected B. mutica more as compared to L. fusca. In B. mutica metal stress substantially reduced shoot dry biomass, root dry biomass, total chlorophylls, and carotenoids contents by 89%, 85%, 65%, and 61%, respectively, while enhanced the SOD activity up to 62 U min−1 g−1 FW. L. fusca showed better growth, chlorophylls and carotenoid contents, SOD activity (up to 79 U min−1 g−1 FW), shoot metal uptake potential (Cd 110 µg pot−1, Pb 91.57 µg pot−1), and root metal concentration (Cd 126 mg kg−1 dm, Pb 117 mg kg−1 dm) compared to B. mutica under Pb and Cd stress. While both grass species showed metal translocation factor less than unity under all levels of metal stress. Keeping in view the above results, it is concluded that L. fusca having better growth and physiology with TF < 1 could be used for phytostabilization of Pb and Cd to reclaim the soil having moderate to lower levels of contamination.

Surge of ore metals in seawater and increased bio-activity: a tracer of VHMS mineralization in Archaean successions, Yilgarn Craton, Western Australia

The Nimbus Ag–Zn(–Au) deposit is a hybrid VHMS deposit with epithermal characteristics formed in the Eastern Goldfields Superterrane, Yilgarn Craton, under shallow water (~ 700 mbsl), low-temperature conditions. Intersections of some ore lenses are high-grade and polymetallic, making similar styles of mineralization attractive Yilgarn exploration targets. The mineralization at Nimbus is hosted by a bimodal felsic–mafic succession of volcanic rocks, which are overlain by a succession of least-altered polymict conglomerates with a carbonaceous to dacitic matrix. A new Re–Os age (2680 ± 34 Ma; nodular pyrite and black shale) suggests that the overlying polymict conglomerate is coeval to ~ 2.70 Ga volcanism and mineralization at Nimbus. The pyrite within the high-grade polymetallic sulfide assemblages has a consistently lower Sb/Ag ratio (1–30) than pyrite from other sulfide phases (e.g., 30 to 1000 in colloform and barren pyrite). Trace elements (TEs) in sedimentary nodular pyrite from multiple intervals along a single drillhole (NBDH010), indicate the existence of an enriched sedimentary interval with higher total TE content, Ag/Au and Sb/Au, lower S/Se, and polymetallic-like signature of Sb/Ag. Within this enriched interval, the black shale matrix of the polymict conglomerate shows higher total organic carbon (TOC), Mo content, and Co/Ni ratios and suggest increased bio-activity at that time, interpreted to be associated with the Ag–Zn(–Au) mineralization. The TE characteristics in sedimentary pyrite, reflecting increased metal content in seawater inferred from in situ pyrite trace element analysis has the potential to be developed into an exploration tool for successions, adjacent and coeval to similar ore deposits.

Effects of heavy metal pollution on germination and early seedling growth in native and invasive Spartina cordgrasses

Seed germination and seedling establishment are the stages most sensitive to abiotic stress in the plant life cycle. We analyzed the effects of copper, zinc and nickel on seed germination and early seedling growth of native Spartina maritima and invasive S. densiflora from polluted and non-polluted estuaries. Germination percentages for either species were not affected by any metal at any tested concentration (up to 2000 μM). However, the increase in metal concentration had negative effects on S. densiflora seedlings. The primary effect was on radicle development, representing initial seedling emergence. Spartina densiflora seedlings emerging from seeds from Tinto Estuary, characterized by high bioavailable metal loads, showed higher tolerance to metals than those from less polluted Odiel and Piedras Estuaries. Comparing our results to metal concentrations in the field, we expect S. densiflora seedling development would be negatively impacted in the most metal-polluted areas in Odiel and Tinto Estuaries.

Assessment of copper, chromium, and lead toxicity in fish (Ctenopharyngodon idella Valenciennes, 1844) through hematological biomarkers.

Hematological variances were seen in Ctenopharyngodon idella when exposed to (LC50 and LC85) copper, chromium, and lead concentration groups. The metal-exposed blood samples after collection were analyzed for comparative analysis of hematological alterations in the reference and treated groups at the different exposure hours. A significant reduction (p < 0.05) in hemoglobin, RBC, hematocrit, total leucocyte, and lymphocyte counts was observed with the increase in metal concentrations, whereas a significant incline (p < 0.05) in granulocyte and monocyte counts was observed with the administered doses of selected toxic metals as compared with the values obtained from the reference group. More pronounced changes in hematological indices both for the red and white blood cells were noticed at the highest dose of LC85-administered metal groups. The induced hematological changes were independent of the exposed duration pattern. The present investigation has significantly contributed in knowledge assessment of metal toxicity based on inclusive evaluation ofdose-response relationships.

Enzyme activities in soil at increasing metal (Cu, Ni, Pb) doses and time-dependence in a model experiment

Aim of this paper is to examine the effect of spiked copper (Cu), nickel (Ni) and lead (Pb) metal salts on the dehydrogenase (oxydo-reductase) and phosphatase (hydrolase) enzyme activities in a characteristic Hungarian soil, the pseudomycelliar chernozem. Pot-experiment was performed with a soil, originating from a spot of the Hungarian soil-information-monitoring (TIM) system of Bicserd. The added metal salts were used in water soluble forms and incorporated uniformly to the soil. Soils were treated with increasing metal concentrations to give the following metal amounts: 0, 50, 200, and 800 kg.ha-1. Enzyme activities of the soil were analysed at the 0th, 7 th, 14 th, and 28th days after the metal addition. The laboratory model-experiment has been set up in three replicates.&#x0D; Effects of metal salts were largely dependent on the chemical and physical properties of pseudomycelliar chernozem soil, the applied heavy metal-types, the doses of used metals and the elapsed time after the pollution. Considering the different metals, the copper prowed to be the most toxic one on the studied enzyme activities, whereas the lead induced those. By comparison with copper the nickel affected a smaller decrease in the soil microbial activity. The dehydrogenase, oxydo-reductase enzyme was found to be more sensitive parameter in comparison with the phosphatase, hydrolase enzyme among the studied condition. Studied enzymes and used methods are suggested, as fast and rather reliable tools for estimating the soil-resilience capacities at heavy metal pollution.