Growth and photosynthetic responses of the bloom-forming cyanobacterium Microcystis aeruginosa to elevated levels of cadmium

Effects of cadmium (Cd) on the growth and photosynthesis of the bloom-forming cyanobacterium Microcystis aeruginosa Kütz 854 were investigated. The growth was markedly inhibited when it was treated with 4 microM Cd. However, the biomass production was almost not influenced after a prolonged exposure at Cd concentrations < or = 2 microM. Chlorophyll content was more sensitive to Cd toxicity than phycobiliproteins at 0.5 microM Cd. However, the decrease of phycobiliproteins was larger than chlorophyll at the highest Cd concentration. A significant increase of F(v)/F(m) value was observed at Cd concentrations < or = 2 microM. On the other hand, when cells were treated with 4 microM Cd, F(v)/F(m) was significantly increased after 12 h of treatment but decreased after 48 h. The true photosynthesis was decreased with the increase of Cd concentration at 2 h. However, we noticed a recovery when the treatment was prolonged. After 48 h of exposure at the highest Cd concentration, photosynthetic oxygen evolution was markedly inhibited but dark respiration increased by 67%. Cellular Cd contents were augmented with the increase of Cd concentration. To our knowledge, we have demonstrated for the first time that the inhibitory site of Cd in M. aeruginosa is not located at the PSII or PSI level, but is probably situated on the ferredoxin/NADP(+)-oxidoreductase enzyme at the terminal of whole electron transport chain. We noticed also an increase of PSI activity, which is probably linked to the enhancement of cyclic electron transport around PSI. We can conclude that the increase of cyclic electron transport and dark respiration activities, and the decrease of phycobiliproteins might be adaptive mechanisms of M. aeruginosa 854 under high Cd conditions.     

Effective removal of coordinated copper from wastewater using a new dithiocarbamate-type supramolecular heavy metal precipitant

A new dithiocarbamate-type heavy metal precipitant, sodium 1,3,5-hexahydrotriazinedithiocarbamate (HTDC), was prepared and used to remove coordinated copper from wastewater. In the reported dithiocarbamate-type precipitants, HTDC possesses the highest percentage of the effective functional groups. It could effectively precipitate copper to less than 0.5 mg l⁻¹ from both synthetic and actual industrial wastewater containing CuEDTA in the range of pH 3–9. UV–vis spectral investigation and elemental analysis suggested that the precipitate was a kind of coordination supramolecular compound, [Cu₃(HTDC)₂]_n. The toxicity characteristic leaching procedure (TCLP) and semi-dynamic leaching test (SDLT) indicated that the supramolecular precipitate was non-hazardous and stable in weak acid and alkaline conditions. Tests of an anion exchange resin D231 provided a clue to simultaneously remove excess HTDC and residual CuEDTA in practical process of wastewater treatment.     

Toxicokinetics of tilapia following high exposure to waterborne and dietary copper and implications for coping mechanisms

One of the major challenges in assessing the potential metal stress to aquatic organisms is explicitly predicting the internal dose in target organs. We aimed to understand the main sources of copper (Cu) accumulation in target organs of tilapia (Oreochromis mossambicus) and to investigate how the fish alter the process of Cu uptake, depuration, and accumulation (toxicokinetics (TK)) under prolonged conditions. We measured the temporal Cu profiles in selected organs after single and combined exposure to waterborne and dietary Cu for 14 days. Quantitative relations between different sources and levels of Cu, duration of treatment, and organ-specific Cu concentrations were established using TK modeling approaches. We show that water was the main source of Cu in the gills (>94 %), liver (>89 %), and alimentary canal (>86 %); the major source of Cu in the muscle (>51 %) was food. Cu uptake and depuration in tilapia organs were mediated under prolonged exposure conditions. In general, the uptake rate, depuration rate, and net bioaccumulation ability in all selected organs decreased with increasing waterborne Cu levels and duration of exposure. Muscle played a key role in accounting for the rapid Cu accumulation in the first period after exposure. Conversely, the liver acted as a terminal Cu storage site when exposure was extended. The TK processes of Cu in tilapia were highly changed under higher exposure conditions. The commonly used bioaccumulation model might lead to overestimations of the internal metal concentration with the basic assumption of constant TK processes.     

Biomarker responses of the earthworm Aporrectodea tuberculata to copper and zinc exposure: differences between populations with and without earlier metal exposure

Biomarkers in the earthworm Aporrectodea tuberculata (Eisen) were measured to find out their possible induction under Cu and Zn exposure and differences in the responses between two populations with different exposure history. The biomarkers applied were concentration of metallothioneins (MT), and cytochrome P4501A (CYP1A) monooxygenase and glutathione-S-transferase (GST) activities. These were measured from earthworms sampled at three distances from a steel smelter in Finland and from the individuals from two populations, one with and another without earlier metal exposure, exposed to three combined Cu/Zn concentrations in the laboratory. In the field, MT concentration, and cytochrome CYP1A and GST activities decreased with increasing distance from the smelter. In the laboratory, biomarker responses varied in relation to the duration and level of exposure, and they were also dependent on the population. The endpoints appeared to be analytically reproducible and sensitive parameters in A. tuberculata, and thus, they can be used in ecotoxicological field monitoring and in experimental research in the laboratory.     

高分子重金属絮凝剂MCC制备及除铜去浊性能

以壳聚糖、L-半胱氨酸为原料,通过酰胺化反应制备了一种具有重金属捕集功能的高分子重金属絮凝剂-2-氨基-3-巯基丙酰壳聚糖(MCC)。以含铜废水为处理对象,通过正交实验研究了MCC的最佳制备条件,对其除铜性能进行了全面探讨,并对絮体形貌进行了观察和分析。结果表明,在最佳条件下制得的MCC具有除浊和捕集重金属离子双重功能,形成的絮体量较大、沉速快,出水水质好,重金属回收率较高,残渣稳定,不易造成二次污染,絮体分形维数越小,空隙越多,除铜效果越好。     

高效重金属捕集剂TDTC对络合铜的去除性能

传统化学沉淀法存在对酸性及低浓度的络合态重金属去除率低的问题,为解决此问题,以三乙烯四胺、二硫化碳为原料合成了重金属捕集剂N,N-双(二硫代羧基)三乙烯四胺(TDTC),并采用红外光谱等分析方法对其结构和主要官能团进行了表征.以酒石酸铜、柠檬酸铜和EDTA铜3种络合铜为去除对象,研究了TDTC对络合铜的去除性能及去除机...     

Changes in pigment concentration and composition in Norway spruce induced by long-term exposure to low levels of ozone

Rametes of Norway spruce were fumigated with 30 ppb (nl litre(-1)) ozone above ambient level for 4 years in open-top chambers. They were grown under different light conditions, because some of the chambers received approximately 10% less light than the others. Samples from three age classes were analyzed for nitrogen and pigments using HPLC. It could be demonstrated that the ozone treatment reduced the concentration of chlorophyll (a) and (b), alpha- and beta-carotene, but increased the concentration of antheraxanthin. A significant decrease was found for the violaxanthin/antheraxanthin ratio following the ozone treatment. The concentration of all the pigments and of nitrogen were significantly related to the age classes, and a similar relationship was found for the light levels, except for antheraxanthin and total carotenoids. The ratio of chlorophyll a/b was only significantly related to the age classes.     

Accumulation and distribution of platinum and rhodium in the European eel Anguilla anguilla following aqueous exposure to metal salts

The platinum group metals (PGM) Pt and Rh are emitted into the environment mainly by catalytic exhaust gas converters of cars and by effluents of hospitals, which use Pt based anti-cancer drugs. However, there is still a lack of information on the availability of these precious metals to the biosphere. As PGM accumulate in sediments of aquatic ecosystems we focused our study on the uptake of the noble metals by European eels, Anguilla anguilla. Therefore, eels were exposed in tap water and humic water containing Pt(4+) and Rh(3+) at a concentration of 170 and 260 microg/l, respectively. After an exposure period of 6 weeks the mean Pt levels in bile, liver, kidney and intestine of the exposed eels ranged between 68 ng/g and 840 ng/g and the mean Rh levels between 35 ng/g and 155 ng/g whereas the PGM levels of the unexposed controls were below the detection limit of 50 ng/g for Pt and 5 ng/g for Rh. Rh was also taken up by gill and spleen. No PGM uptake was found for muscle and blood. The pattern of metal distribution within the eel differed between Pt and Rh and was dependent on the water type. Due to their accumulation capacity for PGM eels are suitable as accumulation indicators to detect PGM pollution in aquatic ecosystems.     

Growth response of bigcone Douglas fir (Pseudotsuga macrocarpa) to long-term ozone exposure in southern California

Long-term radial growth of bigcone Douglas fir (Pseudotsuga macrocarpa) was studied throughout its range in the San Bernardino Mountains of southern California, where ambient ozone has been high for approximately the past 40 years. A gradient of both ozone concentration and precipitation exists from west (high) to east (low). Growth rates of bigcone Douglas fir are considerably lower since 1950 throughout the San Bernardino Mountains, with the largest growth reductions in the western part of the range where ozone exposure is highest. Needle retention is also somewhat lower at high ozone sites. Lower annual precipitation since 1950 may have some impact on long-term growth reductions, and short-term growth reductions induced by drought are an important component of long-term growth reductions at sites with high ozone exposure. An ozone-climate stress complex may be responsible for recent reductions in the growth of bigcone Douglas fir.     

Growth response and phytoextraction of copper at different levels in soils by Elsholtzia splendens

Phytoremediation is a promising approach for cleaning up soils contaminated with heavy metals. Information is needed to understand growth response and uptake mechanisms of heavy metals by some plant species with exceptional capability in absorbing and superaccumulating metals from soils. Greenhouse study, field trial, and old mined area survey were conducted to evaluate growth response and Cu phytoextraction of Elsholtzia splendens in contaminated soils, which has been recently identified to be tolerant to high Cu concentration and have great potential in remediating contaminated soils. The results from this study indicate that the plant exhibited high tolerance to Cu toxicity in the soils, and normal growth was attained up to 80 mg kg(-1) available soil Cu (the NH4OAc extractable Cu) or 1000 mg kg(-1) total Cu. Under the field conditions, a biomass yield of 9 ton ha(-1) was recorded at the soil available Cu level of 77 mg kg(-1), as estimated by the NH4OAc extraction method. Concentration-dependent uptake of Cu by the plant occurred mainly at the early growth stage, and at the late stage, there is no difference in shoot Cu concentrations grown at different extractable soil Cu levels. The extractability of Cu from the highly polluted soil is much greater by the roots than that by the shoots. The NH4OAc extractable Cu level in the polluted soil was reduced from 78 to 55 mg kg(-1) in the soil after phytoextraction and removal of Cu by the plant species for one growth season. The depletion of extractable Cu level in the rhizosphere was noted grown in the mined area, even at high Cu levels, the NH4OAc extractable Cu in the rhizosphere was 30% lower than that in the bulk soil. These results indicate that phytoextraction of E. splendens can effectively reduce the plant-available Cu level in the polluted soils.     

Status of metal levels and their potential sources of contamination in Southeast Asian rivers

To assess the concentration and status of metal contaminants in four major Southeast Asian river systems, water were collected from the Tonle Sap–Bassac Rivers (Cambodia), Citarum River (Indonesia), lower Chao Phraya River (Thailand), and Saigon River (Vietnam) in both dry and wet seasons. The target elements were Be, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Ag, Cd, Ba, Tl, and Pb and the concentrations exceeded the background metal concentrations by 1- to 88-fold. This distinctly indicates enrichment by human urban area activities. The results of a normalization technique used to distinguish natural from enriched metal concentrations confirmed contamination by Al, Cd, Co, Mn, Ni, Pb, and Zn. Cluster analysis revealed the probable source of metals contamination in most sampling sites on all rivers studied to be anthropogenic, including industrial, commercial, and residential activities. Stable lead isotopes analyses applied to track the sources and pathways of anthropogenic lead furthermore confirmed that anthropogenic sources of metal contaminated these rivers. Discharges of wastewater from both industrial and household activities were major contributors of Pb into the rivers. Non-point sources, especially road runoff and street dust, also contributed contamination from Pb and other metals.     

Evaluating the effects of elevated levels of atmospheric trace gases on herbs and shrubs: a prototype dual array field exposure system

In the context of global climate change, an understanding of the long-term effects of increasing concentrations of atmospheric trace gases (carbon dioxide, CO(2), ozone, O(3), oxides of nitrogen, NO(x) etc.) on both cultivated and native vegetation is of utmost importance. Over the years, under field conditions, various trace gas-vegetation exposure methodologies with differing advantages and disadvantages have been used. Because of these variable criteria, with elevated O(3) or CO(2) levels, at the present time the approach of free-air experimental-release of the gas into study plots is attracting much attention. However, in the case of CO(2), this approach (using 15 m diameter study plot with a single circular array of vent pipes) has proven to be cost prohibitive (about 59000-98000 dollars/year/replicate) due to the consumption of significant quantities of the gas to perform the experiment (CO(2) level elevated to 400 ppm above the ambient). Therefore, in this paper, we present a new approach consisting of a dual, concentric exposure array of vertical risers or vent pipes. The purpose of the outer array (17 m diameter) is to vent ambient air outward and toward the incoming wind, thus providing an air curtain to reduce the velocity of that incoming wind to simulate the mode or the most frequently occurring wind speed at the study site. The inner array (15 m diameter) vents the required elevated levels of trace gases (CO(2), O(3), etc.) into the study plot. This dual array system is designed to provide spatial homogeneity (shown through diffusion modeling) of the desired trace-gas levels within the study plot and to also reduce its consumption. As an example, while in the single-array free-air CO(2)-release system the consumption of CO(2) to elevate its ambient concentration by 400 ppm is calculated to be about 980 tons/year/replicate, it is estimated that in the dual array system it would be approximately 590 tons/year/replicate. Thus, the dual array system may provide substantial cost savings (24000-39000 dollars/year/replicate) in the CO(2) consumption (60-100 dollars/ton of CO(2)) alone. Similarly, benefits in the requirements of other trace gases (O(3), NO(x), etc.) are expected, in future multivariate studies on global climate change.     

Dicamba and 2,4-D residues following applicator cleanout: A potential point source to the environment and worker exposure

This paper presents a survey of pesticide residues in tanks following application and throughout the cleanout procedure as conducted by 46 volunteer operators across Colorado. While many pesticides were detected, this paper focuses on dicamba and 2,4-D, which were detected by liquid chromatography/tandem mass spectroscopy (LC-MS/MS). An exponential decrease in concentration was observed with sequential rinses, although this decrease may be more rapid for more water-soluble pesticides. More than 95% of the pesticide in the prerinse solution was removed by the end of the third rinse in all but three operator samples. Concentrations after three rinses were 0.41 ± 0.25 and 3.3 ± 1.1 mg/L for dicamba and 2,4-D, respectively. These concentrations suggest that the recommended practice of three rinses may not be adequate to eliminate off-target effects or point sources of pesticide waste, and that the recommended standard of personal protective equipment is essential to prevent worker exposure to the chemicals.

Implications:?This paper demonstrates that the waste generated during cleanout of pesticide application devices constitutes a potential source of pollution and worker exposure. In particular, while the first rinse of pesticide containers is often treated as hazardous waste and reapplied to crops, the remaining rinses are not. This work demonstrates that the wastewater generated in subsequent rinses can have high enough concentrations to impact worker health, cause off-target effects on crops, and potentially constitute a point source of pesticides. The practical implication is for improved recommendations and regulations regarding pesticide applicators and their cleanout process.     

Growth and photosynthetic responses to copper in wild grapevine

The present study evaluates the tolerance and accumulation potential of Vitis vinifera ssp. sylvestris under moderate and high external Cu levels. A greenhouse experiment was conducted in order to investigate the effects of a range of external Cu concentrations (0–23 mmol L⁻¹) on growth and photosynthetic performance by measuring gas exchange, chlorophyll fluorescence parameters and photosynthetic pigments. We also measured the total copper, nitrogen, phosphorus, sulphur, calcium, magnesium, iron, potassium and sodium concentrations in the plant tissues. All the experimental plants survived even with external Cu concentrations as high as 23 mmol L⁻¹ (1500 mg Cu L⁻¹), although the excess of metal resulted in a biomass reduction of 35%. The effects of Cu on growth were linked to a reduction in net photosynthesis, which may be related to the effect of the high concentration of the metal on photosynthetic electron transport. V. vinifera ssp. sylvestris survived with leaf Cu concentrations as high as 80 mg kg⁻¹ DW and growth parameters were unaffected by leaf tissue concentrations of 35 mg Cu kg⁻¹ DW. The results of our study indicate that plants of V. vinifera ssp. sylvestris from the studied population are more tolerant to Cu than the commercial varieties of grapevine that have been studied in the literature, and could constitute a basis for the genetic improvement of Cu tolerance in grapevine.     

Development of a model to select plants with optimum metal phytoextraction potential

Purpose  

The aim of the present study is to propose a nonlinear model which provides an indicator for the maximum phytoextraction of metals to help in the decision-making process. Research into different species and strategies plays an important role in the application of phytoextraction techniques to the remediation of contaminated soil. Also, the convenience of species according to their biomass and pollutant accumulation capacities has gained important space in discussions regarding remediation strategies, whether to choose species with low accumulation capacities and high biomass or high accumulation capacities with low biomass.     

Reproduction of mallards following overwinter exposure to selenium

Forty pairs of mallards (Anas platyrhynchos) were fed 15 ppm selenium as selenomethionine for about 21 weeks during winter. Twenty pairs served as controls. At the end of 21 weeks, which coincided with the onset of the reproductive season, selenium treatment was ended. Four birds died while on selenium treatment. Treated females lost weight, and their egg-laying was delayed. Hatching success of some of the first eggs laid by selenium-treated females was lower than that of controls, and a few of these early eggs contained deformed embryos, but, after a period of about two weeks off the selenium-treated diet, reproductive success returned to a level comparable with that of controls. The return to normal reproductive success was the result of a corresponding decrease in selenium concentrations in eggs once selenium treatment ended.     

Growth and trace metal accumulation of two Salix clones on sediment-derived soils with increasing contamination levels

The growth and metal uptake of two willow clones (Salix fragilis 'Belgisch Rood' and Salix viminalis 'Aage') was evaluated in a greenhouse pot experiment with six sediment-derived soils with increasing field Cd levels (0.9-41.4 mg kg-1). Metal concentrations of eight elements were measured in roots, stems and leaves and correlated to total and soil water metal concentrations. Dry weight root biomass, number of leaves and shoot length were measured to identify eventual negative responses of the trees. No growth inhibition was observed for both clones for any of the treatments (max. 41.4 mg kg-1 Cd, 1914 mg kg-1 Cr, 2422 mg kg-1 Zn, 655 mg kg-1 Pb), allowing their use for phytoextraction on a broad range of contaminated sediments. However, dry weight root biomass and total shoot length were significantly lower for S. viminalis compared to S. fragilis for all treatments. Willow foliar Cd concentrations were strongly correlated with soil and soil water Cd concentrations. Both clones exhibited high accumulation levels of Cd and Zn in aboveground plant parts, making them suitable subjects for phytoextraction research. Cu, Cr, Pb, Fe, Mn and Ni were found mainly in the roots. Bioconcentration factors of Cd and Zn in the leaves were highest for the treatments with the lowest soil Cd and Zn concentration.     

Heavy metal exposure and behavioral assessment of vultures in a captive environment

Environmental Science and Pollution Research - Heavy metals are a heterogeneous group of metals that can cause detrimental biological disruptions in vultures. Heavy metals play a threatening role...     

Estimating long-term population exposure to ozone in urban areas of Europe

Tropospheric ozone concentrations regarded as harmful for human health are frequently encountered in Central Europe in summertime. Although ozone formation generally results from precursors transported over long distances, in urban areas local effects, such as reactions due to nearby emission sources, play a major role in determining ozone concentrations. Europe-wide mapping and modeling of population exposure to high ozone concentrations is subject to many uncertainties, because small-scale phenomena in urban areas can significantly change ozone levels from those of the surroundings. Currently the integrated assessment modeling of European ozone control strategies is done utilizing the results of large-scale models intended for estimating the rural background ozone levels. This paper presents an initial study on how much local nitrogen oxide (NOx) concentrations can explain variations between large-scale ozone model results and urban ozone measurements, on one hand, and between urban and nearby rural measurements, on the other. The impact of urban NOx concentrations on ozone levels was derived from chemical equations describing the ozone balance. The study investigated the applicability of the method for improving the accuracy of modeled population exposure, which is needed for efficient control strategy development. The method was tested with NOx and ozone measurements from both urban and rural areas in Switzerland and with the ozone predictions of the large-scale photochemical model currently used in designing Europe-wide control strategies for ground-level ozone. The results suggest that urban NOx levels are a significant explanatory factor in differences between urban and nearby rural ozone concentrations and that the phenomenon could be satisfactorily represented with this kind of method. Further research efforts should comprise testing of the method in more locations and analyzing the performance of more widely applicable ways of deriving the initial parameters.