Effect of plant growth on copper solubility and speciation in soil solution samples

The effect of plant growth on copper solubility and speciation was studied in a 10-week pot experiment. A copper-tolerant grass variety (Agrostis capillaris L. var. Parys Mountain) was grown in pots that contained either clean (copper-total approx. 30 mg kg(-1)) or copper contaminated soil (copper-total approx. 170 mg kg(-1)) at two pH levels (4.7 and 5.5). Also, similar pots without vegetation were included in the study. Due to the addition of NH(4)NO(3) fertilizer and subsequent nitrification of ammonia to nitrate, soil pH decreased from 4.7 to 3.5 and from 5.5 to 4, respectively. In the planted pots, soil pH recovered faster after depletion of NH(4)(+). This resulted in a decrease in the calcium solution concentrations and an increase in the dissolved organic carbon (DOC) concentrations in the planted pots. However, this was only observed in the clean soil; in the contaminated soil no difference in DOC levels between bare and planted pots was observed. Copper solubility in the contaminated soil was lower in the presence of plants; in the clean soil no differences were observed between the bare and planted pots. In the planted pots, copper activities in solution in both clean and contaminated soils were two orders of magnitude lower than in the bare pots. Copper activities in the non-planted contaminated soil reached potentially toxic levels ([Cu]+/-10(-5) to 10(-6) M) in contrast to the lower levels in the planted pots ([Cu]+/-10(-7) to 10(-10) M). Data and model results show that plant growth improves pH, DOC and calcium in solution to such an extent that both the total dissolved copper concentration and the free metal activity in soils can be reduced. This stresses the potential beneficial role of plants for the immobilization and detoxification of metals in contaminated soils.     

A revised estimate of copper emissions from road transport in UNECE-Europe and its impact on predicted copper concentrations

Comparisons of measured and model-predicted atmospheric copper concentrations show a severe underestimation of the observed concentrations by the models. This underestimation may be (partly) due to underestimated emissions of copper to air. Since the phase out of asbestos brake lining material, the composition of brake lining material has changed and may contain up to ∼15% copper. This makes brake wear from vehicles potentially an important source of atmospheric (particulate) copper concentrations. In this paper, we reassess the copper emissions due to exhaust emissions and brake wear from road transport. Overall, our reassessments result in an estimate of total copper emission to air in UNECE-Europe of 4.0–5.5 ktonnes yr⁻¹, which is substantially higher than the previous estimate of 2.8 ktonnes yr⁻¹. Copper concentrations over Europe are calculated with the LOTOS-EUROS model using the revised emission data as model input. The results show that the revised emission estimates are a major step towards gap closure of predicted versus observed copper concentrations in ambient air. Brake wear emissions may be responsible for 50–75% of the total copper emissions to air for most of Western Europe. The hypothesis that road transport is an important source of copper emissions is tested and confirmed by (1) reviewing available literature data of chemically speciated PM data from road tunnel studies and (2) the gradient observed in copper concentrations from ambient PM monitoring going from rural sites to street stations. The literature review and observational data suggest that the majority of the emitted PM10 brake wear particles is in the PM2.5–10 size range. The results of this study indicate that modification of brake lining composition is an important mitigation option to reduce copper exposure of the population in Western Europe.     

Effects of copper chloride on formation of polychlorinated dibenzo-p-dioxins in model waste incineration

Combustion experiments in a laboratory-scale fluidized-bed reactor were conducted to elucidate the effects of copper chloride as a catalyst on polychlorinated dibenzo-p-dioxins (PCDDs) formation in municipal waste incineration. We used model wastes with and without copper chloride (CuCl₂ · 2H₂O), both of which contained polyvinyl chloride as a chlorine source. Combustion temperature was set to 900 °C, and the amount of air supplied was twice the stoichiometric ratio. The experimental setup was carefully planned to suppress the influences of experimental conditions except the waste composition. Results of these experiments showed that copper chloride in the waste increased the amount of PCDDs formed and made the homologue profile to shift towards the highly chlorinated species. Copper chloride contributes to the PCDDs formation by promoting chlorination, whereby the reaction is important in that organic matter is chlorinated directly by copper compounds. Copper chloride did not exert a great influence on the isomer distribution patterns of PCDDs, while there appeared a significant difference in the case of PCDFs. This points out the difference of the major formation mechanisms between PCDDs and PCDFs. PCDDs are less formed by the catalytic reactions from carbon/polycyclic aromatic hydrocarbons than PCDFs in our experimental conditions.     

Geochemical fractions of copper in soil chronosequences of selected European floodplains

The influence of soil formation on copper sorption is documented based on chronosequences of soils from three river floodplains in Europe (Danube, Ebro and Elbe). Sequential extraction was used to fractionate copper in original and spiked soils in order to study the long-term and short-term behaviour of copper retention. Copper partitioning among defined geochemical fractions was mainly determined by soil pH and the contents of carbonates, organic matter and Fe-/Mn-oxides and hydroxides. Copper extracted with NH(2)OH.HCl correlated well with the contents of crystalline Fe-oxides and hydroxides, demonstrating increasing retention capacity with progressing soil development. Copper retained in original soils was found in more strongly bound fractions, whereas sorption of freshly added copper was primarily influenced by the presence of carbonates. Beyond the effect of progressing soil formation, variations in organic carbon contents due to different land use history affected the copper retention capacity of the investigated soils.     

Effects of copper chloride on formation of polychlorinated dibenzofurans in model waste incineration in a laboratory-scale fluidized-bed reactor

Combustion experiments in a laboratory-scale fluidized-bed reactor have been performed to clarify the effects of copper chloride as a catalyst on polychlorinated dibenzofurans (PCDFs) formation in municipal waste incineration. We used model wastes with and without copper chloride (CuCl2 x 2H2O) as a catalyst, both of which contained polyvinyl chloride (PVC) as a chlorine source. Combustion temperature was set to 900 degrees C, and the amount of air supplied was twice as much as the theoretical amount. The experimental setup had been carefully planned to ensure avoidance of the influences of previous experiments. Results of these present experiments revealed that copper chloride in the waste increased the amount of PCDFs formed and made the homologue profile shifted towards the highly chlorinated species. Copper chloride contributes to PCDFs formation by promoting chlorination via catalytic reactions, whereby the reaction could be important in that organic matters are chlorinated directly by chlorinated compounds related to Deacon reaction such as copper chloride. It was elucidated that characteristic isomer distribution patterns appeared in case the waste contained copper chloride. It is probable in our experiment with copper chloride that PCDFs are mainly formed via catalytic reactions of copper compounds and carbon.     

Effects of copper chloride on formation of polychlorinated dibenzo-p-dioxins in model waste incineration

Combustion experiments in a laboratory-scale fluidized-bed reactor were conducted to elucidate the effects of copper chloride as a catalyst on polychlorinated dibenzo-p-dioxins (PCDDs) formation in municipal waste incineration. We used model wastes with and without copper chloride (CuCl₂ · 2H₂O), both of which contained polyvinyl chloride as a chlorine source. Combustion temperature was set to 900 °C, and the amount of air supplied was twice the stoichiometric ratio. The experimental setup was carefully planned to suppress the influences of experimental conditions except the waste composition. Results of these experiments showed that copper chloride in the waste increased the amount of PCDDs formed and made the homologue profile to shift towards the highly chlorinated species. Copper chloride contributes to the PCDDs formation by promoting chlorination, whereby the reaction is important in that organic matter is chlorinated directly by copper compounds. Copper chloride did not exert a great influence on the isomer distribution patterns of PCDDs, while there appeared a significant difference in the case of PCDFs. This points out the difference of the major formation mechanisms between PCDDs and PCDFs. PCDDs are less formed by the catalytic reactions from carbon/polycyclic aromatic hydrocarbons than PCDFs in our experimental conditions.     

Structural and functional responses of a freshwater plankton community to acute copper stress

An in-situ experiment was performed to quantify the impacts of copper sulfate on plankton structure and carbon dynamics. Plankton were exposed to 140 microg litre(-1) copper in quadruplicate mesocosms. Community structure was monitored for 14 days by microscopical counts and compared with untreated controls. Carbon dynamics were assessed by tracer studies using (14)C bicarbonate and (14)C glucose, to follow the fate of carbon in the algal- and bacterial-based pathways, respectively. Copper reduced the dry-weight biomass of zooplankton, ciliates, flagellates, and autotrophic phytoplankton. Bacterial biomass was increased by an order of magnitude relative to the controls. The bacterial response was most likely due to reduced grazing pressure and/or nutrient release from dying plankton. Copper reduced the effectiveness of the food web in transporting carbon to the surviving zooplankton. Bacterial-based pathways were more greatly affected than algal-based pathways, because zooplankton in the copper treatment were macro-grazers (cyclopoids), which cannot utilize bacteria.     

Relationship between copper speciation in sediments and bioaccumulation by marine bivalves of Taiwan

This paper evaluates the relationships between copper species in sediments and accumulation by the purple clam (Hiatula diphos) and venus clam (Gomphina aeguilatera) collected from the field and culture (aquaculture) ponds in the polluted coastal area of Lukang, Taiwan. Sediment was sampled along with the molluscs, including oysters (Crassostrea gigas), purple clams (Hiatula diphos), rock-shells (Thais clavigera), venus clams (Gomphina aeguilatera), and hard clams (Meretrix lusoria), from two unique environments of Lukang during the period from August 1993 to July 1994. The data indicate that the total copper concentrations in sediments from culture ponds (185 microg g(-1)) was higher than those of the field (44.0 microg g(-1)). Copper species in sediments were analyzed by a sequential leaching technique. Results show that concentrations of various copper species in the sediments are in the range of 1.14 +/- 0.59 to 13.2 +/- 22.4 microg g(-1) and 0.36 +/- 0.24 to 133 +/- 36.7 microg g(-1) for the two environments, respectively. Also the exchangeable copper in sediment from culture ponds was 15 times higher than that from the field. In addition, the sum of exchangeable and copper carbonates had the highest percentages of copper in both the pond sediment (86.6 %) and the field sediment (50.7 %). Maximum copper concentrations (309 +/- 35.1 microg g(-1)) in oysters were much higher than those in the other benthic organisms by about 4-127 times. Similarly, the data also showed that copper concentrations in Thais clavigera were 12-32 times higher than those in other benthic organisms. Copper concentrations in various benthic organisms differed significantly (p < 0.05) from that in Thais clavigera. This capacity makes Thais clavigera a potential candidate for monitoring copper in marine sediments. In terms of copper species, the best correlation was generally obtained between copper carbonates in sediments and copper concentrations in Hiatula diphos (r = 0.886*). A strong multiple regression correlation (p < 0.05, r2 = 0.7894) also indicates that the copper carbonates may dominate as the available form of copper to Hiatula diphos from various environments in the Lukang coastal area under natural physicochemical conditions.     

Effect of copper on soil functional stability measured by relative soil stability index (RSSI) based on two enzyme activities

Copper can affect essential processes in soils, often for long periods. Enzyme activity is considered a sensitive indicator to evaluate soil health and the potential toxic impact of a soil contaminant. Nevertheless, there is heterogeneity in the responses from enzyme activity assays because of the influence of pH and other physicochemical parameters on both enzyme activity and metal speciation. This leads to complications when comparing soils and limits the validity of the results. To overcome these problems, this paper evaluates resistance and recovery, quantified by using a relative soil stability index (RSSI), of the beta-glucosidase and protease activities towards an additional heat disturbance (17 h at 60 degrees C) in soils where soil organic matter, pH and Cu content were modified in a factorial setup. Chemical analyses (dissolved Cu, pCu(2+), dissolved organic carbon, pH) were performed both before the heat-perturbation and after the enzyme activity monitoring period. Results show that soil pH did not interfere with the RSSI scores of both enzymes. beta-glucosidase RSSI scores were scarcely affected by copper, making it inappropriate for evaluating copper-induced stress to soils. Protease activity shows stimulations of up to 2.5 times the activity of the unperturbed control in uncontaminated samples only. Thus, the protease RSSI score seems a good indicator for soil health relative to copper contamination given that all samples were affected by the presence of copper and high correlations were observed between RSSI scores and the different copper forms.     

Runoff rates,chemical speciation and bioavailability of copper released from naturally patinated copper

The release of copper, induced by atmospheric corrosion, from naturally patinated copper of varying age (0 and 30 years) has been investigated together with its potential ecotoxic effect. Results were generated in an interdisciplinary research effort in which corrosion science and ecotoxicology aspects were combined. The aim of the investigation was to elucidate the situation when copper-containing rainwater leaves a roof in terms of runoff rate, chemical speciation, bioavailability and ecotoxicity effects. Data have been collected during a three-year field exposure conducted in the urban environment of Stockholm, Sweden. The potential environmental effects have been evaluated using a combination of a copper specific biosensor test with the bacterium Alcaligenes eutrophus and the conventional 72-h growth inhibition test with the green alga Raphidocelis subcapitata. The results show annual runoff rates between 1.0 and 1.5 g/m2 year for naturally patinated copper of varying age. The runoff rate increased slightly with patina age, which mainly is attributed to the enhanced first flush effect observed on thicker patina layers. The total copper concentration in investigated runoff samplings ranged from 0.9 to 9.7 mg/l. Both computer modeling and experimental studies revealed that the majority (60-100%) of released copper was present as the free hydrated cupric ion, Cu(H2O)6(2+), the most bioavailable copper species. However, other copper species in the runoff water, such as, e.g. Cu(OH)+ and Cu2(OH)2(2+), were also bioavailable. The copper-containing runoff water, sampled directly after release from the roof, caused significant reduction in growth rate of the green alga. It should be emphasized that the results describe the runoff situation immediately after release from the copper roof and not the real environmental ecotoxicity. Therefore the data should only be used as an initial assessment of the potential environmental effect of copper runoff from building applications. Future risk assessments should also consider dilution effects of copper, changes in its chemical speciation and bioavailability during environmental entry, and type and sensitivity of the receiving ecosystem.     

Variation of zinc and copper in metallothionein-like protein in killifish (Oryzias latipes) exposed to cadmium

Killifish (Oryzias latipes) were exposed for 0, 24, 48 and 168 hours to cadmium solution. The hepatic cytoplasm was fractionated by using Sephadex G-75 and the content of zinc, copper and cadmium in the fractions was measured. Cadmium content in the metallothionein fraction increased with increase of exposure time. Zinc content in the metallothionein fraction was reduced at early exposure time and increased after prolonged exposure. Copper content in the metallothionein fraction was unchanged. It is shown that zinc bound to thionein in the liver is partially replaced by cadmium and that at least two isomers of metallothionein occur in this fish.     

Changes of copper speciation in maize rhizosphere soil

Chemical forms of copper in the rhizosphere and bulk soil of maize were investigated using rhizobox cultivation and sequential extraction techniques. The copper accumulations were also determined. The results demonstrated that there were continuous changes in copper fractionation within the maize rhizosphere. Initially, the amount of exchangeable copper increased before dropping below the initial level after 40 days or so. Carbonate associated copper followed a similar trend of change, but with a slower pace than the exchangeable copper. The increase in carbonate associated copper only become evident after 30 days, with the net loss occurring after 60 days. There were also initial increases in oxide bound copper as well as decreases in the organic matter associated copper, both followed by a turnover after 40-50 days. The accumulation of copper in the maize plant was found to be biomass dependent. The amount of accumulated copper absorbed in the plant material exceeded the initial quantity of the exchangeable copper in the soil, revealing a transformation from less bioavailable to more bioavailable fractions. During cultivation, decreases in redox potential and increases in pH, dissolved organic carbon (DOC), and microbial activity in the maize rhizosphere were observed. The change in copper speciation may result from root-induced changes in DOC, redox potential, and microbial activity in the rhizosphere.     

Seasonal and spatial patterns of metals at a restored copper mine site II. Copper in riparian soils and Bromus carinatus shoots

Soil and plants were sampled throughout winter and spring near a perennial stream traversing a restored mine site in a winter-rainy climate. Within 1m of an acidic reach of the stream, soil had pH 3-5 and 50-100 microg/g "bioavailable" copper (extractable with 0.01 M CaCl2). Soil 2-3 m from the stream had pH 5-8 and lower (less than 3 microg/g) bioavailable copper. "Oxide-bound" copper (extractable with 2N HCl) was 50-100 microg/g at most locations. Copper concentrations in the shoots of field-collected Bromus carinatus declined from 20 microg/g in winter to 2 microg/g in spring at all sampling sites. A similar temporal pattern was found in plants grown under controlled conditions. Thus B. carinatus has a developmental program for control of shoot copper concentration, causing a seasonally-varying pattern of copper phytoaccumulation over a large range of copper availability in the soil.     

悬浮电解法回收废旧电子印刷线路板中的铜

以废旧电子印刷线路板中的金属铜为处理对象,采用悬浮电解法制取纯铜粉。选择了4个影响铜粉的纯度、脱落率和电流效率的因素,每个因素3个水平进行正交实验。实验结果表明,硫酸铜的浓度、氯离子的浓度和电流密度对铜粉的纯度、脱落率和电流效率有较大的影响。通过对正交实验结果的分析得出最优的电解条件,在此电解条件下可得到铜粉的纯度99.8%、脱落率99.6%和电流效率99.7%。     

Accumulation and egestion of dietary copper and cadmium by the grasshopper Locusta migratoria R & F (Orthoptera: Acrididae)

Copper and cadmium budgets were studied for a model insect herbivore/host plant system comprising the oligophagous leaf-chewing grasshopper (Locusta migratoria) feeding on Zea mays (Gramineae). Fifth instar larvae were fed, for between 5 and 20 days, on maize foliage contaminated with either copper, cadmium or on control foliage containing no excess metal. Male and female locusts fed on copper-treated maize retained 45 and 42% of ingested copper respectively, figures not significantly different from the 41 and 33% retained on untreated maize. Remaining copper was egested with the faeces. Locusts fed on copper-treated maize showed an increase of 27% in body copper burden compared with those on the control diet: the increase was independent of time on the diet. Female locusts retained 33% and males 21% of ingested cadmium. Faecal cadmium levels were elevated, and accumulation in both sexes was proportional to time on the Cd-enriched diet. For both copper and cadmium, some ingested metal probably passed directly through the locust gut, bound to undigested food material. Results suggest that grasshoppers may effectively regulate excess dietary copper, but are unable efficiently to regulate cadmium.     

Assessing copper thresholds for phytotoxicity and potential dietary toxicity in selected vegetable crops

Copper pollution in soils is widespread, and its accumulation in crop products could pose a risk on human health. In this paper, bioavailability of added copper (Cu) and critical Cu concentrations in a vegetable garden soil was evaluated for Chinese cabbage (Brassica chinensis L.), pakchoi (Brassica chinensis L.), and celery (Apiumg graveolens L. var. dulce DC) based on human dietary toxicity. The availability of added Cu in the soil decreased with incubation time, and had minimal change after 10-12 weeks. After incubated for 12 weeks, about 60% of added Cu was not extractable by DTPA. The same crops were also grown in sand culture to determine their responses to solution Cu. Shoot growth was significantly inhibited at Cu concentrations above 10 mg kg(-1) in the solution or above 150 mg kg(-1) (DTPA-Cu) in the soil. The sensitivity of the crops to Cu toxicity differed among the three vegetable crops. Copper concentration in shoots and edible parts varied with Cu supply levels and type of the vegetables. Negative correlations (r=-0.90-0.99**) were noted between Cu concentration in shoots and fresh matter yields, but Cu concentrations in the edible parts were positively correlated with available and total Cu in the soil (r=0.91-0.99**). The critical tissue Cu concentrations at 10% shoot DM reduction were 19.4, 5.5, 30.9 mg kg(-1) for Chinese cabbage, pakchoi, and celery, respectively. Based on the threshold of human dietary toxicity for Cu (10 mg kg(-1)), the critical concentrations of total and available Cu in the soil were 430 and 269 mg kg(-1) for pakchoi, 608 and 313 mg kg(-1) for celery, and 835 and 339 mg kg(-1) for Chinese cabbage, respectively.     

Environmental impact of two successive chemical treatments in a small shallow eutrophied lake: Part II. Case of copper sulfate

The appearance of cyanobacteria ( > 10 colony per ml) was not prevented after alum treatment. In order to prevent cyanobacteria efflorescences in a small shallow polymictic lake (Courtille, France), copper sulfate was applied. Treatment level was 63 microg 1(-1) as Cu2+ from CUSO4, 5 H2O. Cyanobacteria were kept under control during the summer. Microcystis sp. completely disappeared, which allowed swimming in the lake throughout the tourist season. Microcystis only reappeared 2 months after the treatment. Copper content in the water column only returned to its background level 2 months after copper addition. This high residence time of copper in the water might have been caused by complexation and adsorption of copper on natural organic matter, whose level was high in the ecosystem studied. A mechanism of transfer of 'truly' dissolved copper towards particulate copper has been underlined and explains the disappearance of this fraction of copper in the water column.     

Linking plant tissue concentrations and soil copper pools in urban contaminated soils

Copper tissue concentrations of radish (Raphanus sativa cv. Cherry Belle), lettuce (Lactuca sativa cv. Buttercrunch) and ryegrass (Lolium perenne cv. Barmultra) grown in a greenhouse in urban contaminated soils are compared to total, soluble and free ion copper pools. The tissue concentrations of copper vary between 8.1 and 82.6 mg Cu kg(-1) dry tissue and the total soil copper content varies between 32 and 640 mg Cu kg(-1) dry soil. The linear regressions with cupric ion activity and total soil copper are both significant (p < 0.01), but cupric ion activity yields a higher level of statistical significance in every case. The results support the hypothesis that free metal in the soil solution is a better indicator of plant metal bioavailability than either total or soluble metal.     

Toxicity of copper on rice growth and accumulation of copper in rice grain in copper contaminated soil

Pot soil experiments showed that copper (Cu) is highly toxic to rice. Rice grain yields decreased exponentially and significantly with the increase of soil Cu levels. Rice grain yield was reduced about 10% by soil Cu level of 100 mg kg(-1), about 50% by soil Cu level of 300-500 mg kg(-1) and about 90% by soil Cu concentration of 1,000 mg kg(-1). Root was more sensitive to soil Cu toxicity than other parts of rice plant at relatively lower soil Cu levels (less than 300-500 mg kg(-1)), but the growth of whole rice plant was severely inhibited at high soil Cu levels (300-500 mg kg(-1) or above). Cu concentrations in rice grain increased with soil Cu levels below 150-200 mg kg(-1), but decreased with soil Cu levels above 150-200 mg kg(-1), with peak Cu concentration at soil Cu level of 150-20 mg kg(-1). Cu was not distributed evenly in different parts of rice grain. Cu concentration in cortex (embryo) was more than 2-fold that in chaff and polished rice. More than 60% of the Cu in grain was accumulated in polished rice, about 24% in cortex (embryo), and about 12% in chaff. So, about 1/3 of the Cu in rice grain was eliminated after grain processing (chaff, cortex and embryo was removed).     

Effect of copper on growth of an aquatic macrophyte,Elodea canadensis

Elodea canadensis has been proposed as a potential biomonitor due to its wide distribution and apparent ability to accumulate pollutants in aquatic ecosystems. We investigated the effects of copper sulfate on growth in E. canadensis to determine its effectiveness as a biomonitor of copper pollution in aquatic systems and whether growth is a suitable index of sub-lethal stress. Copper sulfate significantly slowed or stopped growth at all concentrations (low: 1 ppm, medium: 5 ppm, high: 10 ppm of copper sulfate) used. Final plant drymass was significantly lower in medium and high copper treatments compared with controls. E. canadensis appears to be very sensitive to copper levels, and may be useful as a biomonitor of copper levels in aquatic systems. However, its utility as a bioaccumulator may be limited, because we observed senescence of most leaves in all copper-treated plants following 4 weeks of treatment.