Detrimental Effects Of Heavy Metals Research Articles

Effect of copper and temperature on the photosynthetic physiological characteristics of Ulva linza under elevated CO2 concentrations

Copper (Cu) is vital for macroalgae's functions, but high concentrations can be toxic. Rising CO2 levels affect algal growth and Cu bioavailability. In this study, the results reveal that at 5 °C, low Cu increased Ulva linza growth, while high Cu and elevated CO2 decreased growth. At 10 °C, low Cu and elevated CO2 enhanced growth, but high Cu did not have a significant impact. At 15 °C, high Cu reduced growth, but elevated CO2 offset this effect. Furthermore, under elevated CO2 conditions, the chloroplast structure of the algae appeared to be denser, accompanied by a large amount of starch granules, compared to low CO2 conditions. These results emphasize that lower temperatures, in conjunction with elevated CO2 concentration, could intensify the toxic effects of high Cu concentrations on thalli. However, at higher temperatures, elevated CO2 concentration appeared to be capable of mitigating the detrimental effects of heavy metals on algae.

Complexation and immobilization of arsenic in maize using green synthesized silicon nanoparticles (SiNPs)

Arsenic (As) is a heavy metal that is toxic to both plants and animals. Silicon nanoparticles (SiNPs) can alleviate the detrimental effects of heavy metals on plants, but the underlying mechanisms remain unclear. The study aims to synthesize SiNPs and reveal how they promote plant health in Arsenic-polluted soil. 0 and 100% v/v SiNPs were applied to soil, and Arsenic 0 and 3.2 g/ml were applied twice. Maize growth was monitored until maturity. Small, irregular, spherical, smooth, and non-agglomerated SiNPs with a peak absorbance of 400 nm were synthesized from Pycreus polystachyos. The SiNPs (100%) assisted in the development of a deep, prolific root structure that aided hydraulic conductance and gave mechanical support to the maize plant under As stress. Thus, there was a 40–50% increase in growth, tripled yield weights, and accelerated flowering, fruiting, and senescence. SiNPs caused immobilization (As(III)=SiNPs) of As in the soil and induced root exudates Phytochelatins (PCs) (desGly-PC2 and Oxidized Glutathione) which may lead to formation of SiNPs=As(III)–PCs complexes and sequestration of As in the plant biomass. Moreover, SiNPs may alleviate Arsenic stress by serving as co-enzymes that activate the antioxidant-defensive mechanisms of the shoot and root. Thus, above 70%, most reactive ROS (OH) were scavenged, which was evident in the reduced MDA content that strengthened the plasma membrane to support selective ion absorption of SiNPs in place of Arsenic. We conclude that SiNPs can alleviate As stress through sequestration with PCs, improve root hydraulic conductance, antioxidant activity, and membrane stability in maize plants, and could be a potential tool to promote heavy metal stress resilience in the field.

The detrimental effects of heavy metals on tributaries exert pressure on water quality, Crossocheilus aplocheilus, and the well-being of human health

The escalating presence of heavy metals (HMs) in the Panjkora River water and their impact on fish pose a significant challenge to both the ecological community and human health. Consequently, a study was conducted with the primary aim of elucidating their influence on human health-related issues. To address this, the concentrations of heavy metals, including arsenic (As), cadmium (Cd), iron (Fe), manganese (Mn), lead (Pb), and zinc (Zn), in both water and the fish species Crossocheilus diplocheilus were investigated across various locations within the study area. The quantification of HMs concentration was carried out utilizing an atomic absorption spectrophotometer. The highest concentration in water was found as 0.060 mg/L for Pb and lowest for Fe, whereas the highest concentration in fish was 2.028 mg/kg for Pb and lowest for As. Human health risk associated with fish eating was evaluated by using health risk indices (HRI) for non-carcinogenic health risks and targeted cancer risk (TR) for carcinogenic health risks. The values of the health risk index (HRI) were found greater than 1 except Fe (0.0792), Zn (0.782), and Mn (0.541). The highest mean HRI > 1 was recorded for As (62.99), Cd (26.85), and Pb (10.56). This implies that fish consumption from river Panjkora is not safe up to some extent. Similarly, the TR value for As, Cd, and Pb was found 2.8 ×10-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes {10}^{-2}$$\\end{document}, 1.6 ×10-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes {10}^{-2}$$\\end{document}, 2.8 ×10-3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{-3}$$\\end{document} which showed cancer risk. There is a detected risk to human health associated with the consumption of fish from the Panjkora River. The government must implement adaptive measures to address this significant issue of water pollution in the study area. Additionally, there is a need for further extensive and prolonged research studies in this context.

Biochar and vermicompost modulated Pb toxicity in summer savory (Satureja Hortensis L.) plants through inducing physiological and biochemical changes

The primary environmental factor affecting the biochemical attributes of plants is soil pollution by heavy metals. The detrimental effects of heavy metals on plants can be lessened by soil amendments. The goal of the current research was to determine the potential of biochar (BC) and vermicompost (VC) as soil amendments in reducing Pb toxicity in summer savory (Satureja HortensisL.) though physiological and biochemical modifications. Therefore, the pot experiment was conducted with Pb toxicity (control (non-Pb), 300, and 600 mg kg soil-1) and soil amendments (control, 2% BC, 10% VC, and 1% BC+5% VC) based on a completely randomized design. The results showed that Pb toxicity at 600 mg kg soil-1 led to significant decreases in shoot weight (41%), root weight (25%), leaf relative water content (20%), and chlorophyll content (39%) compared to the control. However, it resulted in increases in malondialdehyde (61%) and electrolyte leakage (49%) when BC and VC were not applied. The results showed that Pb toxicity at 600 mg kg soil-1 led to decreases in shoot weight (41%), root weight (25%), leaf relative water content (20%), and chlorophyll content (39%), but increases in malondialdehyde (61%), and electrolyte leakage (49%) compared to the control in the treatments without BC and VC application. However, BC and VC, particularly their combination were more effective in improving plant growth. The interaction of Pb at 300 mg kg-1 and combined BC and VC resulted in higher total phenolic content, total flavonoid content, essential oil (EO) content, and EO yield with 29, 62, and 39, and 35% raises compared with the control. Agglomerative hierarchical clustering revealed that Pb at 300 and 600 mg kg soil-1 differed from the control, and that combined VC and BC significantly varied from their individual values. Combining BC and VC is more effective than using them separately in alleviating Pb toxicity, as it enhances plant growth and secondary metabolite production. The results have the potential to benefit the improvement of summer savory resistance in Pb-polluted soils.

Hybrid ionogel membrane of PVDF incorporating ionic liquid-reduced graphene oxide for the removal of heavy metal ions from synthetic water

The biggest challenge around the world is water contamination by heavy metal ions. The detrimental effects of heavy metals on humans as well as on aquatic ecosystems are of great concern. In this regard, membrane technology is playing its role in the separation of these non-biodegradable heavy metal ions from the waste water, though improvement in the technology is still the need of time. The present work deals with the novel strategy of developing PVDF/rGO nanocomposite membrane with the inclusion of IL via phase inversion method to remove heavy metal ions. Inclusion of rGO and IL as filler into the PVDF hydrophobic matrix improved the antifouling characteristics and solvent contents of the hybrid ionogel membranes. In addition, the decrease in the contact angle from 90° (Pure PVDF) to 46° (PVDF/IL/rGO) was observed pointing towards the hydrophilic nature of the resulting membranes. Among various compositions, 0.5 w/v % rGO demonstrated maximum efficiency by removing up to 90% of various divalent cations including Cu2+, Cd2+, Zn2+, and Mn2+.The flux recovery ratio was observed to be 94% after testing the membrane several times. Up to 70% removal of As3+ from the same membrane is a hope to design a membrane with improved efficiency for removing As3+.

A Review and Analysis of Heavy Metals in Freshwater Reservoirs of Pakistan: their Bioaccumulation, Biological Magnification and Biotic Transmission

Problems associated with pollution are becoming more severe as industrialization advances rapidly. Inorganic and organic wastes, both water-soluble and insoluble, are discharged into the aquatic environment, contributing to one of the most critical problems: water pollution. The discharge of waste in water channels allows heavy metal ions, which are toxic to all kinds of life, to enter the food chain. Lead, nickel, sodium, potassium, zinc, copper, iron lithium, cadmium, and chromium (VI) are among the most hazardous metal ions. Because they don't break down, metal ions build up in the environment and move up the food chain. Therefore, higher trophic level animals are more susceptible to their toxicityHeavy metals found in freshwater and sediments have been found to bioaccumulate in fish tissues. Rawal Dam, Mangla Dam, and Zabi Dam were identified as highly contaminated areas of freshwater that had detrimental effects on fish and human health. The Rawal Dam, which received a lot of industrial and sewage drainage from Punjab's metropolitan areas and industry, was significantly contaminated compared to other Pakistani Dams. Changhoz and Ghol Dams, with their massive water flows and relatively few accompanying industrial facilities, have the healthiest ecosystems of all Pakistan's dams. Changhoz Dam's freshwater fish are considered to be safe for human consumption. Heavy metals are accumulated by migratory birds at Rawal Dam from eating fish from freshwater reservoirs. Heavy metal pollution has been linked to a variety of social, ecological, and economic issues. The detrimental effects of heavy metals on aquatic organisms and human well-being can be reduced if wastewater is purified before being released into freshwater.

Co-Precipitation of Cd, Cr, Pb, Zn, and Carbonates Using Vibrio harveyi Strain Isolated from Mediterranean Sea Sediment

Heavy metal contamination is listed among the most alarming threats to the environment and human health. The detrimental effects of heavy metals in the natural environment span from a reduction of biodiversity to toxic effects on marine life—through microplastic born heavy metals, to impairment of microbial activity in the soil, and to detrimental effects on animal reproduction. A host of different chemical and biological technologies have been proposed to alleviate environmental contamination by heavy metals. Relatively less attention has been paid to the microbial precipitation of heavy metals, as a side mechanism of the most general process of microbially induced calcite precipitation (MICP). This process is currently receiving a great deal of interest from both a theoretical and practical standpoint, because of its possible practical applications in concrete healing and soil consolidation, and its importance in the more general framework of microbial induced mineral precipitation. In this study, we analyse the ability of the marine bacteria Vibrio harveyi in co-precipitating CaCO3 minerals, together with Cd, Cr, Pb, and Zn added in form of nitrates, from solutions containing CaCl2. The precipitated carbonatic minerals were a function of the different heavy metals present in the solution. The process of co-precipitation appears to be rather effective and fast, as the concentrations of the 4 heavy metals were reduced in 2 days by 97.2%, on average, in the solutions. This bioremediation technology could be used as environmental friendly procedure to de-contaminate suitable environmental matrices. The high performance of this process makes it particularly interesting for an upscaling from lab to field.

Effect of long-term manganese exposure on oxidative stress, liver damage and apoptosis in grouper Epinephelus moara ♀ × Epinephelus lanceolatus ♂

Manganese is an indispensable trace element, however, it may be present at high concentrations in water and sediments of aquatic ecosystems due to natural and anthropogenic activities, and can interfere with physiological and biochemical mechanisms in fish. This study was conducted to determine the toxic effects associated with exposure to Mn2+ (0, 0.5, 1, 2, and 4 mg/L) for 30 d, regarding liver damage and apoptosis in Yunlong grouper (Epinephelus moara♀×E. lanceolatus♂). Expression of superoxide dismutase (sod) and catalase (cat) genes in the liver was significantly increased on days 10 and 20 following Mn2+ exposure (4 mg/L), but was reduced on day 30. Similarly, expression of glutathione peroxidase (gpx) and glutathione reductase (gr) genes was elevated after 10 d of exposure to 2 and 4 mg/L Mn2+, but decreased after 20 and 30 d. After 30 d of exposure to high concentrations (2 and 4 mg/L) of Mn2+, liver tissue showed hepatic sinusoidal gap congestion, dilatation, cell vacuolation, and necrosis. In addition, the activities of alanine aminotransferase (ALT) and aspartate transaminase (AST) as well as 8-hydroxydeoxyguanosine (8-OHdG) levels were significantly increased after Mn2+ exposure. Moreover, Mn2+ exposure altered the expression pattern of some pivotal genes associated to apoptosis (p53, bax, bcl-2, apaf-1, caspase-9, and caspase-3), which suggested that Mn2+ exposure induces apoptosis through the mitochondrial pathway. The above results showed that excessive Mn2+ induced apoptosis and liver damage in grouper through elicitation of oxidative stress. These insights help elucidate the mechanism by which Mn2+ induces toxicity in marine fish, and provide a new perspective regarding the detrimental effects of heavy metals in fish.

Association of urinary or blood heavy metals and mortality from all causes, cardiovascular disease, and cancer in the general population: a systematic review and meta-analysis of cohort studies.

Amounting epidemiological evidence has shown detrimental effects of heavy metals on a wide range of diseases. However, the effect of heavy metal exposure on mortality in the general population remains unclear. The primary objective of this study was to clarify the associations between heavy metals and mortality from all causes, cardiovascular disease (CVD), and cancer based on prospective studies. We comprehensively searched Pubmed, Embase, and Web of Science electronic databases to identify studies published from their inception until 1 March 2022. Investigators identified inclusion criteria, extracted study characteristics, and assessed the methodological quality of included studies according to standardized guidelines. Meta-analysis was conducted if the effect estimates of the same outcome were reported in at least three studies. Finally, 42 original studies were identified. The results of meta-analysis showed that cadmium and lead exposure was significantly associated with mortality from all causes, CVD, and cancer in the general population. Moderate evidence suggested there was a link between arsenic exposure and mortality. The adverse effects of mercury and other heavy metals on mortality were inconclusive. Epidemiological evidence for the joint effect of heavy metal exposure on mortality was still indeterminate. In summary, our study provided compelling evidence that exposure to cadmium, lead, and arsenic were associated with mortality from all causes, CVD, and cancer, while the evidence on other heavy metals, for example mercury, was insignificant or indeterminate. Nevertheless, further prospective studies are warranted to explore the joint effects of multiple metal exposure on mortality.

Bioaccumulation of manganese and its effects on oxidative stress and immune response in juvenile groupers (Epinephelus moara ♀ × E. lanceolatus ♂)

We evaluated the effects of Mn in juvenile Yunlong groupers (Epinephelus moara ♀ × E. lanceolatus ♂). The groupers were exposed to Mn2+ (0, 0.5, 1, 2, and 4 mg/L) for 30 days after which they were assessed. The results indicate the accumulation of Mn in fish depended on dose and time. Mn2+ accumulation in tissues occurred in the following order: liver > gills > intestine > muscle. The concentrations of SOD and CAT in the fish significantly increased after 10 and 20 days of treatment with 4 mg/L Mn2+ but decreased after 30 days. Similarly, GSH and GPx levels increased after 10 days of exposure to 2 and 4 mg/L Mn2+ but decreased after 20 and 30 days of exposure. Additionally, malondialdehyde levels significantly increased after exposing the fish to 2 and 4 mg/L Mn2+ for 10, 20, and 30 days. In addition, liver HSP70 and HSP90 levels significantly increased at days 20 and 30 in all fish exposed to Mn2+. In addition, when Mn2+ concentration was 1, 2, and 4 mg/L, liver C3 and C4 levels were significantly increased after 10, 20, and 30 days. Conversely, the levels of LZM and IgM significantly decreased. Mn2+ also significantly upregulated the expression of genes associated with immunity (tlr3, tnf-α, il-1β, and il-6) in the fish, which suggests that it induces immunotoxicity by altering the immune response. Overall, the findings showed that Mn2+ can disrupt grouper health by bioaccumulating in the fish and subsequently inducing oxidative stress and immune responses. These results can help elucidate the mechanism by which manganese induces toxicity in marine fish. Additionally, they provide a new perspective regarding the detrimental effects of heavy metals in fish.

Physiological disturbances in rams chronically exposed to the chimney emissions of a copper smelter

Detrimental effects of heavy metals on animals and humans are of considerable concern. This research describes the long-term effects of exposure of male sheep to emissions from a copper smelter. Blood parameters and reproductive hormones were measured in male Kermani sheep reared around a copper smelter in KhatoonAbad, Kerman province, Iran. Representative blood samples were collected from randomly-selected rams (3–4 years old) at 4 geographical directions (south, north, east and west) and 4 distances (approximately 10, 20, 30 and 40 km) from the smelter. Hematological and biochemical parameters including WBC, HCT, HGB, AST, ALT, ALP and LDH were higher (P < 0.05) in flocks located at 10 km south from the smelter and lower at 40 km west; indicating liver and kidney damage in the sheep reared at shorter distances to the smelter. The relative expressions of HSD17B3 and CYP11A1 mRNA levels in the testis were lower at 10 km and highest at 40 km distance. Expression levels of HSD17B3 and CYP11A1 in the west direction were 11.3 and 11.1 percent higher than in the south direction. The lowest concentration of FSH, LH and T, were observed at 10 km south, an indication of deranged hypothalamic- hypophyseal- testicular function in these sheep. At 10 km distance, FSH concentration was 70 percent lower, and at 10 km south, T and LH levels were 92 and 83 percent lower than the highest values obtained at 40 km west. It was concluded that long-term exposure to heavy metals around this smelter may reduce the general health and normal reproductive function in male sheep, and probably other living species. However, more detailed studies in the region are warranted.

Counteracting effects of heavy metals and antioxidants on male fertility

Infertility is regarded as a global health problem affecting 8-12% of couples. Male factors are regarded as the main cause of infertility in 40% of infertile couples and contribute to this condition in combination with female factors in another 20% of cases. Abnormal sperm parameters such as oligospermia, asthenospermia, and teratozoospermia result in male factor infertility. Several studies have shown the deteriorative impact of heavy metals on sperm parameters and fertility in human subjects or animal models. Other studies have pointed to the role of antioxidants in counteracting the detrimental effects of heavy metals. In the currents study, we summarize the main outcomes of studies that assessed the counteracting impacts of heavy metal and antioxidants on male fertility. Based on the provided data from animal studies, it seems rational to administrate appropriate antioxidants in persons who suffer from abnormal sperm parameters and infertility due to exposure to toxic elements. Yet, further human studies are needed to approve the beneficial effects of these antioxidants.

Adverse Impact of Heavy Metals on Bone Cells and Bone Metabolism Dependently and Independently through Anemia.

Mounting evidence is revealing that heavy metals can incur disordered bone homeostasis, leading to the development of degenerative bone diseases, including osteoporosis, osteoarthritis, degenerative disk disease, and osteomalacia. Meanwhile, heavy metal‐induced anemia has been found to be intertwined with degenerative bone diseases. However, the relationship and interplay among these adverse outcomes remain elusive. Thus, it is of importance to shed light on the modes of action (MOAs) and adverse outcome pathways (AOPs) responsible for degenerative bone diseases and anemia under exposure to heavy metals. In the current Review, the epidemiological and experimental findings are recapitulated to interrogate the contributions of heavy metals to degenerative bone disease development which may be attributable dependently and independently to anemia. A few likely mechanisms are postulated for anemia‐independent degenerative bone diseases, including dysregulated osteogenesis and osteoblastogenesis, imbalanced bone formation and resorption, and disturbed homeostasis of essential trace elements. By contrast, remodeled bone microarchitecture, inhibited erythropoietin production, and disordered iron homeostasis are speculated to account for anemia‐associated degenerative bone disorders upon heavy metal exposure. Together, this Review aims to elaborate available literature to fill in the knowledge gaps in understanding the detrimental effects of heavy metals on bone cells and bone homeostasis through different perspectives.

Bioavailability of heavy metal load in soil, groundwater, and food crops manihot esculenta and carica papaya in dumpsite environment

The need for consciousness of the impact of heavy metal on crop production and human health risk through policy formulation necessitated the study. Screening of the total heavy metal iron (Fe), nickel (Ni), cadmium (Cd), lead (Pb), chromium (Cr), and copper (Cu) concentration in soils collected at random at a depth of 0–30 cm within and around dumpsite environment in Ikhueniro, Iguomo, and Okhuahe suburban communities, Benin City, Nigeria was carried out. Cassava tubers, Pawpaw pods (manihot esculenta and carica papaya) cultivated and groundwater within and around the dumpsite environment were also tested for the selected heavy metal. The study employed integrated scientific methods in actualizing its aim. The results show that mean values of 520.97 ± 1.66 mg/kg Fe, 39.07 ± 0.33 mg/kg Ni, 1.41 ± 0.10 mg/kg Cd, 1.92 ± 0.00 mg/kg Pb, 1.24 ± 0.02 mg/kg Cr, and 24.97 ± 5.16 mg/kg Cu were recorded for soil. On the other hand, 127.00 ± 2.01: 22.36 ± 1.20 mg/kg Fe and 5.70 ± 2.11: 0.98 ± 1.11 mg/kg, respectively, amongst other metals measured in cassava and pawpaw. The results were compared to Standard Organization of Nigeria (SON), National Food and Drug Administration Control (NAFDAC), and Food and Agricultural Organisation/World Health Organisation (FAO/WHO) standards; it was observed that Fe, Ni, and Pb exceeded the threshold values for metal concentration in soil and drinking water. Policy formulation restricting farming and drilling of boreholes within the locus of dumpsite environment is advocated to fostering the attainment of green environment for sustainable development and public consciousness of the detrimental effects of heavy metals on human health.

Detrimental Effects of Heavy Metals in Soil, Plants, and Aquatic Ecosystems and in Humans.

Environmental pollution has posed a major threat to flora as well as fauna for the past few decades. Industries release effluents into the environment which act as the major source of pollution. The hazardous effects of heavy metals released from these industries impact the soil and due to bioaccumulation of these compounds in the food chain, they ultimately result in a serious human health hazard. The concentration of metals like chromium (Cr), lead (Pb), nickel (Ni), cadmium (Cd), zinc (Zn), titanium (Ti), cobalt (Co), and several others in plants as well as in aquatic animals is above permissible limits according to the World Health Organization (WHO) and the Federal Environmental Protection Agency (FEPA) guidelines. This is why we need to prevent the aquatic ecosystem and human health from detrimental effects. In this review we will be discussing the harmful effects of these metals on soil, plants, aquatic ecosystems, and human health.

Nano-hydroxyapatite alleviates the detrimental effects of heavy metals on plant growth and soil microbes in e-waste-contaminated soil.

The crude recycling activities of e-waste have led to the severe and complex contamination of e-waste workshop topsoil (0-10 cm) by heavy metals. After nano-hydroxyapatite (NHAp) application in June 2013, plant and soil samples were obtained in November 2013, December 2013, March 2014 and June 2014. The results showed that NHAp effectively reduced the concentration of CaCl2-extractable Pb, Cu, Cd, and Zn in the topsoil and significantly reduced the metal content in ryegrass and also increased the plant biomass compared with that of the control. Moreover, the concentrations of CaCl2-extractable metals in the soil decreased with increasing NHAp. NHAp application also increased the activities of soil urease, phosphatase and dehydrogenase. Moreover, the soil bacterial diversity and community structure were also altered after NHAp application. Particularly, Stenotrophomonas sp. and Bacteroides percentages were increased. Our work proves that NHAp application can alleviate the detrimental effects of heavy metals on plants grown in e-waste-contaminated soil and soil enzyme activities, as well as soil microbial diversity.

Effect of pH and time on the accumulation of heavy metals in Gram-negative bacteria

The release of heavy metals into our environment is very important and causes an environmental pollution problem. Contamination of the aquatic environment by toxic heavy metals is a serious pollution problem because they can reach water-courses either naturally through a variety of geochemical processes or by direct discharge of municipal, agricultural and industrial wastewater. The bioremediation of heavy metals using microorganisms has received a great deal of attention in recent years because their potential application in industry. Microorganisms uptake metal either actively (bioaccumulation) and passively (biosorption). Some bacteria have developed chromosomally or extra-chromosomally controlled detoxification mechanisms to overcome the detrimental effects of heavy metals. In the present work, we have studied resistance to heavy metals and the capacity of a Gram-negative bacteria to accumulate lead and zinc. Results obtained indicated that the bacterial strain exhibited high Minimal Inhibitory Concentration (MIC) values for metal ions tested ranging from 75 mg/l to 500 mg/l and it was able to accumulate more than 90% of lead and zinc during the active growth cycle. Effect of pH and time on heavy metal removal was also studied properly.

Increased heavy metal tolerance of cowpea plants by dual inoculation of an arbuscular mycorrhizal fungi and nitrogen-fixer Rhizobium bacterium

Through biological inoculation technology, the bacterial-mycorrhizal-legume tripartite symbiosis in artificially heavy metal polluted soil was documented and the effects of dual inoculation with arbuscular mycorrhizal (AM) fungus and Rhizobium (N-fixing bacteria, NFB) on the host plant cowpea (Vigna sinensis) in pot cultures were investigated at six concentrations of Zn (0.0 ‐ 1000 mg/kg dry soil) and Cd (0.0 ‐ 100 mg/kg dry soil). From a number of physiological indices measured in this study, microsymbionts significantly increased dry weight, root : shoot ratios, leaf number and area, plant length, leaf pigments, total carbohydrates, N and P content of infected plants as compared with non infected controls at all levels of heavy metal concentrations. Tolerance index of cowpea plants was increased in the presence of microsymbionts than in their absence in polluted soil. Microsymbionts dependencies of cowpea plants tended to be increased at higher levels of Zn and Cd in polluted soil. Metals accumulated by microsymbionts-infected cowpea plant were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance widely exists in them. This study provides evidence for benefits of NFB to AM fungi in the protection of host plants against the detrimental effects of heavy metals. If so, bacterial-AM-legume tripartite symbiosis could be a new approach to increase the heavy metal tolerance of legumes plants under heavy metal polluted soil. Key word: Mycorrhiza, Vigna sinesis, heavy metals, microsymbiosis, Rhizobium.

Ultrastructural Responses of the LichenBryoria fuscescensto Simulated Acid Rain and Heavy Metal Deposition

Effects of simulated acid rain and heavy metal deposition on the ultrastructure of the lichenBryoria fuscescens(Gyeln.) Brodo and Hawksw. were examined in a field study conducted in northern Finland. Lichens were exposed to simulated rain containing two levels of a mixture of copper (Cu2+) and nickel (Ni2+) ions alone or in combination with acid rain (H2SO4) at pH 3 over 2 months in addition to ambient rainfall. The algal and fungal components responded differently to pH and there was an interaction with metal toxicity. The algal partner was the most sensitive to acid rain and heavy metal combinations and had more degenerate cells than the fungal partner. Damage was apparent in chloroplasts and mitochondria, where thylakoid and mitochondrial cristae were swollen. The fungal partner was the more sensitive to high concentrations of metal ions in the absence of acidity, suggesting an ameliorating interaction between the metals and acidity. For algae, critical metal concentrations in the thallus were >50 μg g−1for Cu and >7 μg g−1for Ni in the presence of acidity, and >20 μ g g−1for Ni in the absence of acidity. Detrimental effects of heavy metals on fungal ultrastructure were seen when thallus metal concentrations exceeded 400 μg g−1for Cu and 100 μg g−1d. wt for Ni. The results suggest that acid wet deposition containing metal ions may reduce survival of lichens in northern environments.

The effects of heavy metals (other than mercury) on marine and estuarine organisms.

Heavy metals such as copper, zinc and lead are normal constituents of marine and estuarine environments. When additional quantities are introduced from industrial wastes or sewage they enter the biogeochemical cycle and, as a result of being potentially toxic, may interfere with the ecology of a particular environment. In different marine organisms, the behaviour of heavy metals is described in terms of their absorption, storage, excretion and regulation when different concentrations are available in the environment. At higher concentrations, the detrimental effects of heavy metals become apparent and their different toxic effects and factors affecting them are also described.