Long-term effects of heavy metals on aouatic plants

In long-term experiments lasting up to 73 days the effect of rather low levels of zinc, copper, lead and cadmium on the growth and metal uptake was studied by investigating four aquatic plant species: Elodea nuttallii, Callitriche plataycarpa, Spirodela polyrhiza and Lemma gibba. Except Elodea, which was already very sensitive to 5 μmol Cu 1^?1, no differentiation in growth or mortality could be detected depending on species or elements. There was a clear differentiation between the uptake levels of the heavy metals with regard to the plant species, resulting in a higher heavy metal content in de submerged species in comparison to the floating ones. For zinc, lead and cadmium, an equal ratio was detected between the concentration in the medium and in the plant tissue independent of the plant species. The involvement of roots in element absorption by aquatic plants and the possibility of using aquatic plants as indicators of heavy metal pollution in Dutch waters are discussed.     

Detection and localization of aluminum and heavy metals in ectomycorrhizal Norway spruce seedlings

Norway spruce seedlings colonized with Hebeloma crustuliniforme were grown in growth pouches. After formation of ectomycorrhizas, the seedlings were exposed to Al or the heavy metals Cd, Cu, Ni, or Zn at various concentrations for 5 weeks to estimate the detection limits of metals with X-ray microanalysis in the cryo-scanning electron microscope. When the lowest metal concentrations (1 mM Al(3+), 0.1 mM Cd(2+), 0.2 mM Cu(2+), 0.5 mM Ni(2+), 2 mM Zn(2+)) were applied, only Al and Zn were detected at low X-ray counts in the ectomycorrhizas. After application of 10-fold higher metal concentrations, distinct metal accumulation patterns were observed. Cd was detected predominantly in the Hartig net, Al and Ni in the Hartig net and in the cell walls of the cortex, and Zn in the Hartig net, the cortical cell walls and the fungal mantle. Cu was not detected at all. By combining X-ray microanalysis with absolute metal concentrations found in the roots, the estimated detection limits of X-ray microanalysis were: Al> or =0.86 mg g(-1), Cd> or =0.26 mg g(-1), Ni> or =1.30 mg g(-1), and Zn> or =0.54 mg g(-1), whereas Cu was not detectable even at root concentrations of 0.47 mg g(-1). Treatments with the highest metal concentrations showed high X-ray counts of metals in cells of the stele but reduced concentrations of the macronutrients K, Mg, and P in roots, indicating a possible disturbance of root and ectomycorrhizal function.     

Concentrations of metals in mink and other mammals from Washington and Idaho

From 1981 to 1983, concentrations of metals were determined in mink Mustela vison, muskrats Ondatra zibethica, and small mammals at one contaminated site in Idaho and at two less contaminated sites in Idaho and Washington. The highest concentrations of Pb and Cd occurred in samples from the Coeur d'Alene River system near or downstream from an extensive mining-smelting complex in northern Idaho. Maximum concentrations of Pb in the liver of a mink (22 microg g(-1)) and in pooled liver samples of both voles (Microtus spp., 5.8 microg g(-1)) and deer mice (Peromyscus maniculatus, 10.5 microg g(-1)) were higher than those inducing serious problems, including mortality, in experimental mammals on Pb-contaminated diets. Concentrations of Cd, Cu, Hg, and Zn were generally low. Declines in certain mammal populations have probably occurred in northern Idaho as a result of direct toxicity of metals and associated secondary effects on cover and food supply.     

Sub-lethal effects of heavy metals on activated sludge microorganisms

The effects of heavy metals, at sub-lethal concentrations, on activated sludge microbial ecosystem were investigated. Adsorption capacity and rate of copper, chromium, lead and zinc on microbial flocs were much faster than that of organic matters. Metals affected not only the adsorption rate of organic matters but also the COD adsorption capacity of the activated sludge. Effects of heavy metals. on wastewater treatment performance of a sequencing batch reactor were also studied. Metal-laden wastewater at sub-lethal levels affected the performance to different extents, depending on the hydraulic retention time. Metal ions acted as a strong competitor against the organic compounds for active sites on the bioflocs instead of acting as a toxic microbial inhibitor, thus hampering organic adsorption and affecting the COD removal efficiency under shorter HRTs.     

The effects of elevated metals on benthic community metabolism in a Rocky Mountain stream

The effects of elevated metals (dissolved Zn, Mn and/or Fe) in a Rocky Mountain stream were assessed using measures of primary productivity, community respiration and water-column toxicity. Primary productivity was measured as rates of O2 evolution from natural substrates incubated in situ in closed chambers. Oxygen depletion within these chambers, when incubated in the dark, provided estimates of periphyton community respiration. Sediment community respiration on fine-grained sediments, collected and composited along each stream study reach, was measured on-site by incubating these sediments in closed chambers and measuring O2 depletion. Toxicity was measured as percent mortality of Ceriodaphnia dubia during 48 h acute tests. Gross (GPP) and net primary productivity (NPP) decreased significantly with increasing metal concentrations, from 10.88 +/- 1.46 g O2 m(-2) day(-1) to 0.83 +/- 0.20 g O2 m(-2) day(-1) and 9.85 +/- 1.43 g O2 m(-2) day(-1) to 0.81 +/- 0.20 g O2 m(-2) day(-1), respectively for the reference and most impacted site. Community respiration (CR) declined from 0.65 +/- 0.08 g O2 m(-2) day(-1) to 0.02 +/- 0.01 g O2 m(-2) day(-1) with increasing metal concentrations. Sediment community respiration (SCR) decreased from 0.26 +/- 0.02 g O2 m(-2) day(-1) to 0.01 +/- 0.01 g O2 m(-2) day(-1) at these same sites. Ceriodaphnia dubia mortality increased from 0% at the reference site to 95 +/- 5% at the most impacted sites. Net daily metabolism, quantum yield and assimilation ratio all decreased with increasing metal concentrations, suggesting that both autotrophic and heterotrophic components of the periphyton community were impaired. Overall, functional measures were able to discern sites receiving greater metal impacts from less-impacted sites, with combinations of dissolved metals explaining between 25 and 92% of the variance in the regression models. Using these regression models we were able to calculate lethal and inhibition concentrations of dissolved Zn in the Eagle River. The lethal concentration (LC50) of Zn for Ceriodaphnia dubia is 123 mg liter(-1). The concentrations of Zn which inhibited respiration (IC50) were 177 mg liter(-1) for CR and 199 mg liter(-1) for SCR. These results indicate functional measures may be as sensitive to metal concentrations as acute toxicity tests.     

Heavy metals effects on proteolytic system in sunflower leaves

Plant proteolytic system includes proteases, mainly localized inside the organelles, and the ubiquitin-proteasome pathway in both, the cytoplasm and the nucleus. It was recently demonstrated that under severe Cd stress sunflower (Helianthus annuus L.) proteasome activity is reduced and this results in accumulation of oxidized proteins. In order to test if under other heavy metal stresses sunflower proteolytic system undergoes similar changes, an hydroponic experiment was carried out. Ten days old sunflower plants were transferred to hydroponic culture solutions devoid (control) or containing 100 microM of AlCl(3), CoCl(2), CuCl(2), CrCl(3), HgCl(2), NiCl(2), PbCl(2) or ZnCl(2) and analyzed for protein oxidative damage and proteolytic activities. After 4 days of metal treatment, only Co(2+), Cu(2+), Hg(2+), and Ni(2+) were found to increase carbonyl groups content. Except for Al(3+) and Zn(2+), all metals tested significantly reduced all proteasome activities (chymotrypsin-like, trypsin-like and PGPH) and acid and neutral proteases activities. The effect on basic proteases was more variable. Abundance of 20S protein after metal treatments was similar to that obtained for control samples. Co(2+), Cu(2+), Hg(2+), Ni(2+), Cr(3+), and Pb(2+) induced accumulation of ubiquitin conjugated proteins. It is concluded that heavy metal effects on proteolytic system cannot be generalized; however, impairment of proteasome functionality and decreased proteases activities seem to be a common feature involved in metal toxicity to plants.     

Bioavailability and cellular effects of metals on Lumbricus terrestris inhabiting volcanic soils

Whether the radial thickness (RT) of the chloragogenous tissue and intestinal epithelium of earthworms (Lumbricus terrestris) reflects the bioavailability of metals in soils was investigated in two areas, one with active volcanism (Furnas) and another with no volcanic activity since 3 million years ago (Santa Maria), in the Azores. Metal contents in soil samples and earthworms from the two areas were analyzed. Autometallography and measurements of the RT were performed in the chloragogenous tissue and intestinal epithelium. Earthworms from the active volcanic area demonstrated lower RT of chloragogenous tissue and intestinal epithelium as well as higher levels of bioavailable metals, especially Zn and Cd. Comparison of bioavailable metal contents between both areas suggests a higher risk for uptake of potentially toxic metals in the active volcanic area than in the non-active volcanic area, which is reflected by the lower RT of the chloragogenous tissue and intestinal epithelium in the former.     

Biomonitoring of concentrations of platinum group elements and their correlations to other metals

Biomonitoring of Pt, Pd, Pb, Mn, Cu, Fe and Zn was conducted using leaves (two and six months old) of laurel (Laurus nobilis L.) ornamental shrubs grown in 14 sampling sites located on the central green belts of six avenues and streets of Athens. In this biomonitoring, we determined, for the first time in Greece, the concentrations of the new urban 'pollutants' Pt and Pd, and we estimated the correlations among the concentrations of all the above-mentioned metals as well as among the metal concentrations and the traffic load. Cluster analysis and principal component analysis (PCA) of the data revealed three distinct groups of metals and two groups of sites (one with high and the other with relatively low levels of pollution). Using varimax-rotated PCA for the metals, four factors were extracted explaining 92.3% of the total shared variance, which are further discussed. The importance of seasonal timing of sampling is revealed by the data and discussed in connection with the meteorological conditions.     

The effect of wastewater cations on activated sludge characteristics: effects of aluminum and iron in floc.

Wastewater samples collected from seven wastewater treatment plants (WWTPs) were characterized to assess the impacts of wastewater cations on the activated sludge process. The cations included in this study were sodium (Na+), potassium, ammonium, calcium, magnesium, aluminum (Al), and iron (Fe). Among the selected cations, Al and Fe were of most interest to this study because their role in bioflocculation has not been extensively studied and remains largely unknown. The data showed that WWTPs contained highly varying concentrations of Na+, Al, and Fe in the wastewater and that these cations were responsible for differences between WWTPs as to sludge dewatering rates and effluent quality. In general, a high influent Na+ concentration caused poor sludge dewatering and effluent characteristics. However, when sufficient Al and Fe were present in floc, the deleterious effects of Na+ were offset. The data associated with Al further revealed that waste activated sludge with low Al contained high concentrations of soluble and colloidal biopolymer (protein + polysaccharide), resulting in a high effluent chemical oxygen demand, high conditioning chemical requirements, and poor sludge dewatering properties. These results suggest that Al will improve activated sludge effluent quality by scavenging organic compounds from solution and binding them to floc.     

Interaction effects of metals and salinity on biodegradation of a complex hydrocarbon waste

The presence of high levels of salts because of produced brine water disposal at flare pits and the presence of metals at sufficient concentrations to impact microbial activity are of concern to bioremediation of flare pit waste in the upstream oil and gas industry. Two slurry-phase biotreatment experiments based on three-level factorial statistical experimental design were conducted with a flare pit waste. The experiments separately studied the primary effect of cadmium [Cd(II)] and interaction effect between Cd(II) and salinity and the primary effect of zinc [Zn(II)] and interaction effect between Zn(II) and salinity on hydrocarbon biodegradation. The results showed 42-52.5% hydrocarbon removal in slurries spiked with Cd and 47-62.5% in the slurries spiked with Zn. The analysis of variance showed that the primary effects of Cd and Cd-salinity interaction were statistically significant on hydrocarbon degradation. The primary effects of Zn and the Zn-salinity interaction were statistically insignificant, whereas the quadratic effect of Zn was highly significant on hydrocarbon degradation. The study on effects of metallic chloro-complexes showed that the total aqueous concentration of Cd or Zn does not give a reliable indication of overall toxicity to the microbial activity in the presence of high salinity levels.     

Acid and aluminum effects on the survival of littoral macro-invertebrates during acute bioassays

Six common macro-invertebrates were exposed to soft water at pH 4.5, with or without 200 microg liter(-1) Al added. Survivals were determined at 6, 12, 24 and 48 h and compared with neutral pH, Al-free controls. The order of acid-sensitivity among the test animals, from greatest to least (with mean 24/48 h survivals in the pH 4.5, low Al treatment in parentheses), was: Caenis sp. (2%) > Hyalella azteca (12%) > Enallagma sp. (20%) > Gyraulus sp. (55%) > Chironomidae (94%) > Hydracarina (99%). Aluminum significantly reduced the survivals of Gyraulus, Hyalella and Chironomidae. The latter group experienced no significant mortality at pH 4.5 except when Al was present. In contrast, the Hydracarina were unaffected by both acid and acid plus Al exposure, and the survivals of Enallagma and Caenis at low pH were enhanced by Al. These differential responses to the treatments indicate that both acid and Al stress may control the structure of the littoral macroinvertebrate community in acid lakes.     

The interactive effects of low pH, toxic metals, and DOC on a simulated temporary pond community

The effects of pH, potentially toxic metals, and dissolved organic carbon (DOC) on a freshwater, palustrine wetland assemblage (three amphibian species, one mosquito genus, and 18 genera of algae) were examined in 500 liter outdoor mesocosms. The design was fully factorial and exposure levels were set to represent concentrations that occur naturally in temporary ponds in central Pennsylvania, an acid-impacted region of the USA. Water chemistry was precisely regulated by use of an artificial pond water rather than using stream water or well water with partially unknown composition. Jefferson (Ambystoma jeffersonianum) and spotted salamanders (A. maculatum) were negatively impacted by low pH and high metal concentrations. Wood frogs (Rana sylvatica) were negatively impacted by high DOC and low pH. These negative effects included increased time to metamorphosis and decreased survival and wet body mass at metamorphosis. Mosquito emergence was unaffected by pH, metals, or DOC. All three abiotic factors (metals, pH, and DOC) interacted to determine algal taxonomic composition. Hence, abiotic conditions may determine amphibian reproductive success both directly and indirectly, via effects on algae, since a primary food source of salamanders, zooplankton, are affected by changes in algal composition. These complex interactions should be considered in evaluating the possible toxicity of pond waters to fauna and flora. Until now, pH alone has been considered the primary limiting factor for amphibians breeding in temporary ponds.     

铜、镉对水螅的急性和联合毒性作用

试验研究重金属铜(Cu2 )、镉(Cd2 )对水螅的急性毒性和联合毒性作用,探索水螅(Hydra sp.)对Cu2 、Cd2 以及两者混合的毒性效应,为水产动物病害的防治中合理使用消毒、杀虫剂以及水体污染评价提供一些参考信息.结果表明,Cu2 对水螅的24 h半致死浓度(LC50)、48 hLC50、72 hLC50、96 hLC50分别为0.072、0.054、0.042、0.037 mg/L;Cd2 对水螅的24 hLC50、48hLC50、72 hLC50、96 hLC50分别为0.001 70、0.000 63、0.000 36、0.000 36 mg/L;Cu2 、Cd2 对水螅的安全浓度分别为3.7×10-4、3.6×10-6mg/L.水螅对两种重金属的毒性反应既快速又敏感,其中Cu2 对水螅的毒性较Cd2 快,但Cd2 的毒性比Cu2 的强.等毒性配比的两种重金属混合液对水螅的毒性大于单一毒性,为协同作用.两种重金属对水螅的LC50随试验时间的延长而减小,它们对水螅的安全浓度远低于渔业水质标准.     

The effects of exogenous plant growth regulators in the phytoextraction of heavy metals

The term "assisted phytoextraction" usually refers to the process of applying a chemical additive to contaminated soil in order to increase the metal uptake by crop plants. In this study three commercially available plant growth regulators (PGRs) based on cytokinins (CKs) were used to boost the assisted phytoextraction of Pb and Zn in contaminated soil collected from a former manufactured gas-plant site. The effects of EDTA treatment in soil and PGR treatment in leaves of Helianthus annuus were investigated in terms of dry weight biomass, Pb and Zn accumulation in the upper parts of the plants, Pb and Zn phytoextraction efficiency and transpiration rate. Metal solubility in soil and its subsequent accumulation in shoots were markedly enhanced by EDTA. The combined effects of EDTA and cytokine resulted in an increase in the Pb and Zn phytoextraction efficiency (up to 890% and 330%, respectively, compared to untreated plants) and up to a 50% increase in foliar transpiration. Our results indicate that exogenous PGRs based on CKs can positively assist the phytoextraction increasing the biomass production, the metal accumulation in shoots and the plant transpiration. The observed increase in biomass could be related to its action in stimulation of cell division and shoot initiation. On the other hand, the increase in metal accumulation in upper parts of plant could be related to both the role of PGRs in the enhancement of plant resistance to stress (as toxic metals) and the increase in transpiration rate, i.e. flux of water-soluble soil components and contaminants by the regulation of stomatal opening.     

Fate and effects of heavy metals in salt marsh sediments

The fate and effects of selected heavy metals were examined in sediment from a restored salt marsh. Sediment cores densely covered with Spartina patens were collected and kept either un-amended or artificially amended with nickel (Ni) under standardized greenhouse conditions. Ni-amendment had no significant effect on the fate of other metals in sediments, however, it increased root uptake of the metals. Metal translocation into the shoots was small for all metals. Higher Ni concentrations in plants from amended cores were accompanied by seasonal reductions in plant biomass, photosynthetic capacity and transfer efficiency of open photosystem II reaction centers; these effects, however, were no longer significant at the end of the growing season. Root colonization by arbuscular mycorrhizal fungi (AMF) resembled that of natural salt marshes with up to 20% root length colonized. Although Ni-amendment increased AMF colonization, especially during vegetative growth, in general AMF were largely unaffected.     

Inter- and intra-specific variation on sensitivity of larval amphibians to nitrite

Several authors have suggested that nitrogen-based fertilizers may be contributing to the global amphibian decline. We have studied the impact of sodium nitrite on early aquatic stages of Epidalea calamita, Pelophylax perezi and Hyla meridionalis larvae from Do?ana National Park (coastal wetland) and P. perezi from Gredos Mountain (high mountain ponds), exposed during 10 to 16 days. After 8 days of exposure all P. perezi larvae from Do?ana presented 100% mortality at 5 mg l(-1)N-NO2(-) while E. calamita larvae mortality rates were significantly lower at that concentration after 15 days. However, for H. meridionalis at day 15 no deaths were registered at 5 mg l(-1)N-NO2(-) and at 20 mg l(-1)N-NO2(-) presented intermediate mortality rates. In Do?ana the 10 d LC50 of older H. meridionalis larvae was between 20 and 30 mg l(-1)N-NO2(-) whilst for P. perezi it was below 5 mg l(-1)N-NO2(-). These results indicate inter-specific variation of the sensitivity of larval amphibians to nitrite. Gredos Mountain P. perezi larvae exposed since the egg stage were highly sensitive to nitrite, with a 16 d LC50 below 0.5 mg l(-1)N-NO2(-). The same species in Do?ana had a 15 d LC50 between 5 and mg l(-1)N-NO2(-). These results suggest that there is also intra-specific variation in sensitivity of amphibian larvae to nitrite: mountain amphibian populations appear to be more sensitive to polluted environments than coastal populations. Geographic and genetic variation and evolutionary adaptation of tolerance may also be the keys to variation amongst populations of the same species.     

Acid and aluminum effects on freshwater zooplankton: an in situ Mesocosm study

An in situ mesocosm experiment was performed to evaluate the role of aluminum toxicity in determining zooplankton community responses to take acidification. Large plastic enclosures were suspended in East Twin Lake, Ohio, USA, and duplicates were either untreated controls (pH 8.8), acidified to pH 4.5 over a 23 day period, or acidified and also spiked with incremental additions of Al, to produce a final inorganic monomeric Al level of 180 microg/liter at pH 4.5. Zooplankton abundance and species richness declined in both acid treatments, relative to the control, as numerous acid-sensitive species were eliminated. All of the acid-sensitive species were also Al-sensitive, declining in abundance more rapidly in the acid plus Al treatment than in the acid-alone treatment. Only two small cladocerans (Bosmina longirostris and Chydorus sphaericus) were acid tolerant. Both were also tolerant of elevated Al levels.     

养护条件对二次铝灰-垃圾飞灰基地聚物中重金属稳固化的影响

以添加SiO2粉末后的二次铝灰和垃圾焚烧飞灰为原料,经过碱激发制备地聚物固化体。将制备好的地聚物固化体样品分别放在30、35、40、45和50 ℃,相对湿度为80%的恒温恒湿培养箱内养护,探究不同养护条件对固化体中重金属浸出特性的影响,并考察生活垃圾焚烧飞灰处理前后重金属化学形态、晶体结构和微观形貌的改变。结果表明：重金属Cr的相对浸出率在30～45 ℃下降明显,45～50 ℃内趋于平缓;而Cd和Pb的相对浸出率在30～40 ℃略微上升,40～50 ℃呈下降趋势,并且Pb的相对浸出率在40～45 ℃下降明显;Zn的相对浸出率随着养护温度的升高缓慢下降。重金属Cr、Cd、Zn和Pb的相对浸出率在前10 d内下降较大,10～14 d下降缓慢。当养护温度为50 ℃时,地聚物中重金属Cr、Cd、Zn和Pb的浸出浓度分别降到0.172、0.072、0.218和3.803 mg·L-1,满足《生活垃圾填埋场控制标准》（GB 16889-2008）的浸出要求。