Root versus canopy uptake of heavy metals by birch in an industrially polluted area: contrasting behaviour of nickel and copper

We investigated root versus canopy uptake of nickel and copper by mountain birch, Betula pubescens subsp. czerepanovi, close to a nickel-copper smelter on the Kola Peninsula, northwest Russia. To distinguish between aerial contamination of leaf surfaces by dust particles and root-derived contamination of leaves by soluble metals, we transplanted seedlings from a control site to clean and metal-contaminated soils and exposed these seedlings both in clean and polluted sites. Patterns of leaf surface contamination and root uptake were similar for nickel and copper; however, nickel but not copper was effectively translocated from roots to shoots and leaves. The majority (80-95%) of nickel and copper found in birch foliage in the heavily contaminated site was due to deposition of dust particles on leaf surfaces; 32-40% of foliar nickel and 9-19% of foliar copper were in water soluble forms. Washing of fresh leaves removed only a minor part of surface contaminants; boiling of unwashed leaves in distilled water for 15 min removed >90% of soluble nickel and copper.     

Heavy metals in birch leaves around a nickel-copper smelter at Monchegorsk, northwestern Russia

Concentrations of metals in birch leaves were measured around the Severonikel smelter at Monchegorsk, Kola Peninsula, northwestern Russia, between 1991 and 1994. Concentrations of Ni, Cu and Fe near the smelter were 6-12 times higher than the recent regional background concentrations, while concentrations of Mn and Zn were 5-10 and 1.5-2 times lower, respectively. The regional background concentrations of Ni and Cu have increased 3-5 times during the last 20 years. Foliage concentrations of micronutrients (Zn and Mn) showed less annual variation than Ni and Cu. Contamination changed more sharply along the northeastern gradient than along the southern one. Subalpine birch forests were significantly less affected by Ni and Cu than lowland forests, but the lower concentration of Mn indicated a greater impact of SO(2) in mountainous regions. Although birch accumulated relatively less pollutants than conifers, birch resistance to pollution makes it a possible indicator in environmental studies since it survives even within the wastelands where conifers have vanished.     

Impact of a smelter closedown on metal contents of wheat cultivated in the neighbourhood

BACKGROUND: The contamination of soils by heavy metals engenders important environmental and sanitary problems in Northern France where a smelter has been located for more than one hundred of years. It has been one of the most important Pb production sites in Europe until its closedown in March 2003. Ore smelting process generated considerable atmospheric emissions of dust. Despite an active environmental strategy, these emissions were still significant in 2002 with up to 17 tonnes of Pb, 32 tonnes of Zn and 1 tonne of Cd. Over the years, the generated deposits have led to an important contamination of the surrounding soils. Previous studies have shown pollutant transfers to plants, which can induce a risk for human and animal health. The objective of this study was to evaluate the consequences of the smelter closedown on the Cd and Pb contents of wheat (grain and straw) cultivated in the area. METHODS: Paired topsoil and vegetable samples were taken at harvest time at various distances to the smelter. The sample sites were chosen in order to represent a large range of soil metal contamination. Sampling was realised on several wheat harvests between 1997 and 2003. 25 samples were collected before the smelter closedown and 15 after. All ears of about 1 m long of two rows were manually picked and threshed in the lab. Similarly, straw was harvested at the same time. Total metal contents in soil and wheat samples were quantified. RESULTS: A negative correlation between metal concentrations in soil and the distance to the smelter was shown. The wheat grain and straw showed significant Cd and Pb contents. The straw had higher metal contents than the grain. During the smelter activity, the grain contents were up to 0.8 mg kg(-1) DM of Cd and 8 mg kg(-1) DM of Pb. For the straw, maximum contents were 5 mg kg(-1) DM of Cd and 114 mg kg(-1) DM of Pb. After the smelter closedown, we observed a very large decrease of Pb in the grain (82%) and in the straw (91%). A smaller decrease was observed for Cd in grain. Despite this improvement, 80% of the studied samples remained non-acceptable for human consumption, according to the European legislation values, due to a high Cd content. DISCUSSION: Results highlighted a difference in metal accumulation in the plant organs as well as a difference in metal uptake. The approach pointed out the importance of atmospheric fallout in the wheat contamination pathways for Pb. The smelter closedown has lead to a decrease of the Pb content in wheat. It is interesting to relate this finding with the lead blood levels in children living close to the smelter. CONCLUSIONS: Those results have confirmed the importance of dust fallout in the plant contamination pathways. Before the closedown, Pb measured in the plant was principally originating from the smelter dust emissions. It raised the question of the sanitary risks for humans and animals living in the surrounding a of the smelter. RECOMMENDATIONS AND PERSPECTIVES: In the literature, very few articles take the dust deposit as contamination pathways for crops into consideration. However, in highly contaminated sites, this pathway can be very important. Thus, it would be worthy studying the uptake of metal contaminants by plants through the foliar system.     

White birch (Betula papyrifera Marshall) foliar litter decomposition in relation to trace metal atmospheric inputs at metal-contaminated and uncontaminated sites near Sudbury, Ontario and Rouyn-Noranda, Quebec, Canada

Decomposition of white birch (Betula papyrifera Marshall) foliar litter was examined at metal-contaminated and uncontaminated sites established along gradients of soil Cu, Ni, Pb and Zn concentrations near Sudbury, Ontario and Rouyn-Noranda, Quebec. Over an 18-month study period, a significantly lower rate of litter mass loss was observed at the Sudbury contaminated site (S1) than at the uncontaminated site (S2). This result was not duplicated at corresponding sites (RN1, RN2) in Rouyn-Noranda, despite similar levels of soil metal contaminants and atmospheric inputs. Concentrations of metals in litter increased at all sites with time. However, the greatest litter Cu and Ni concentrations were observed at S1 (188 and 192 microg/g, respectively), a result of substantial net gains of these elements from atmospheric inputs. On a per hectare basis, Cu accumulation in litter at S1 approached recommended application rates of Cu as copper sulphate for control of fungal diseases in agricultural operations, indicating that the current rate of Cu smelter emissions in Sudbury may cause the observed impairment of decomposition.     

Density patterns of gall mites (Acarina:Eriophyidae) in a polluted area

Trends in the densities of six species of gall mites on European aspen (Populus tremula) and on two birch species (Betula pubescens and B. pendula) were compared in an air pollution gradient from the Harjavalta copper-nickel smelter, SW Finland. The densities of gall mites on both birch species decreased towards the smelter and were negatively correlated with the levels of copper and nickel in the birch leaves. In contrast, the densities of aspen mites correlated neither with distance from the pollution source nor with the content of heavy metals in aspen leaves. Both birch and aspen trees tended to produce smaller leaves near the smelter, but a significant correlation between gall mite densities and site-specific leaf areas was only found for one species of mite.     

Clonal differences in copper and zinc tolerance of birch in metal-supplemented soils

Metal tolerance of a range of birch clones (Betula pendula and Betula pubescens) originating from metal-contaminated sites in England, Wales, Belgium and Finland were tested in soils supplemented with several concentrations of copper (Cu) or zinc (Zn) (500, 2000, 5000 mg kg-1 dry wt. soil of CuSO(4).5H2O or ZnSO(4).7H2O) for 4 months and with sub-toxic metal supplements (500 mg CuSO4, 2000 mg ZnSO4) for 6 months. When grown at high concentrations of metals, severe toxicity symptoms (growth inhibition, chlorosis, necrosis) and clear evidence for differences in tolerance to this toxicity were found in a subset of the clones. When all clones were grown at a much lower, sub-toxic level of metal, again significant differences could be found between some of the clones. Clones derived from the same population varied greatly in their tolerance. However, the overall pattern of metal specificity varied in agreement with the type of soil contamination at the site of origin. The growth of the clones from Harjavalta Cu/nickel smelter area was 19% better in Cu than in Zn-supplemented soil, on average. The growth of clones from Maatheide Zn smelter are was 19% poorer in Cu- than in Zn-supplemented soil. Sensitive clones accumulated more Cu and Zn to the above-ground parts. Some birch clones were able to survive at about 20-fold higher than typical total background Cu or Zn concentrations, whereas most clones were able to grow without serious toxic symptoms at about 10-fold concentrations.     

Variations in chemical composition of birch foliage under air pollution stress and their consequences for Eriocrania miners

The relationships between chemical composition of birch foliage, individual performance and population density of both solitary and gregarious species of Eriocrania leafminers (Lepidoptera: Eriocraniidae) were studied in the vicinity of the Harjavalta copper-nickel smelter, southwestern Finland. The contents of heavy metals (Cu, Ni, Fe and Zn) in birch foliage exponentially decreased with the distance from the factory whereas the content of manganese showed the opposite trend. Performance parameters of Eriocrania miners were correlated neither with the distance from the pollution source nor with the foliar content of heavy metals. However, larval masses of both solitary and gregarious species were highest at the zone of moderate pollution. The levels of total nitrogen and total carbon and the carbon: nitrogen ratio in birch leaves showed no clear patterns in relation to distance from the factory. Feeding efficiency of solitary larvae increased with higher foliar nitrogen content but decreased when the carbon: nitrogen ratio was high. Survival of solitary Eriocrania species was negatively correlated with total leaf carbon content. However, the population density of solitary miners showed a negative correlation with total foliar nitrogen and a positive correlation with the carbon:nitrogen ratio. Performance of the gregarious E. haworthi was not correlated with the chemical composition of birch leaves, whereas population density was highest close to the factory complex and correlated positively with the levels of copper and nickel in birch leaves. Consequently, pollution-induced changes in measured host plant chemicals were unlikely to affect population densities of Eriocrania miners via altered larval performance.     

Budburst phenology of white birch in industrially polluted areas

Effects of environmental contamination on plant seasonal development have only rarely been properly documented. Monitoring of leaf growth in mountain birch, Betula pubescens subsp. czerepanovii, around a nickel-copper smelter at Monchegorsk hinted advanced budburst phenology in most polluted sites. However, under laboratory conditions budburst of birch twigs cut in late winter from trees naturally growing around three point polluters (nickel-copper smelter at Monchegorsk, aluminium factory at Kandalaksha, and iron pellet plant at Kostomuksha) showed no relationship with distance from the emission source. In a greenhouse experiment, budburst phenology of mountain birch seedlings grown in unpolluted soil did not depend on seedling origin (from heavily polluted vs. clean sites), whereas seedlings in metal-contaminated soil demonstrated delayed budburst. These results allow to attribute advanced budburst phenology of white birch in severely polluted sites to modified microclimate, rather than to pollution impact on plant physiology or genetics.     

Accumulation of Cu and Ni in successive stages of Lymantria dispar L. (Lymantriidae, Lepidoptera) near ore smelters at Sudbury, Ontario, Canada

The accumulation of Cu and Ni in successive life stages of the gypsy moth (Lymantria dispar), feces, and foliage near an ore smelter at Sudbury, Ontario and a control site was investigated. Higher concentrations of Cu and Ni were found in all larval stages collected at Sudbury than in those from the control site indicating that elevated levels of these metals in the Sudbury environment is an important factor influencing body burdens. These differences were associated with higher metal concentrations in the foliage of host trees from this site. However, differences between sites became less significant for pupae and adult stages. At the Sudbury site, concentrations of Cu (microg g(-1) dry wt) decreased in successive instars and then increased in tissues of pupae and adults. In contrast, Cu content (microg/individual) increased during larval development and then decreased in pupae and adults. The pattern of Ni concentration and content in larvae from the Sudbury site was similar to that of Cu. Patterns of Cu and Ni concentration and content throughout the life stages are explained by changes in weight resulting in a dilution effect in early stages, and a concentrating effect in later stages. Differences in Cu and Ni concentration and content between Sudbury and control populations became less significant following the pupal stage suggesting metal elimination with the exuviae and meconium. This study also illustrates the importance of sampling all stages in an insect's development when measuring accumulation of metals. Fecal and foliar concentrations of Cu and Ni from Sudbury were not significantly different suggesting that metal assimilation is low. Even though gypsy moths from Sudbury contain elevated levels of Cu and Ni, metal burdens in their tissues do not represent a significant route through the food chain. However, the conversion of foliage with high metal content to feces implies that other ecosystem consequences should be investigated.     

Metal contamination in the lichen Alectoria sarmentosa near the copper smelter of Murdochville, Québec

Lichens were used to evaluate the metal pollution in a forest ecosystem around the smelter of Murdochville, Canada. As reached values 5.8 times higher in the smelter vicinity than in the 'background' sites. This enrichment was 2 times higher for 3 metals (Cu, Cd and Pb). The highest As, Ba, Cd, Cu, and Pb concentrations in lichens were 4, 112, 1, 23, 50 and 952mg/kg respectively. Contamination declined exponentially with increasing distance from the smelter and was related to elevation and slope exposition to the smelter flux. (206)Pb/(207)Pb and (206)Pb/(204)Pb ratios were low close to the smelter (1.16 and 18), but increased with distance to constant values (1.19 and 18.7) and showed an inverse correlation with lead concentrations. Forest contamination was detectable up to 30km from the smelter.     

Reproduction of mountain birch along a strong pollution gradient near Monchegorsk, Northwestern Russia

We explored effects of severe pollution on sexual reproduction of mountain birch, Betula pubescens subsp. czerepanovii, by counting catkins on sample branches and weighing both somatic and generative structures of both short and long shoots from birches growing at 21 sites around large nickel-copper smelter at Monchegorsk, Northwestern Russia. Proportion of reproducing trees, production of catkins, shoot and catkin weight, as well as the relative difference in weight of somatic structures of generative and vegetative shoots, were generally independent of pollution load; in 2003 birches growing in industrial barrens produced more catkins than birches growing in unpolluted forests. Thus, we found no support for the hypothesis that reproductive allocation should decrease with decrease in environmental capacity. Absence of adverse effects might indicate that long-lasting pollution impact already eliminated the most sensitive individuals from the affected birch populations.     

Interactions between precipitation and Scots pine canopies along a heavy-metal pollution gradient

Bulk precipitation and stand throughfall were collected during 1992-96 at distances of 0.5, 4 and 8 km from the Harjavalta Cu-Ni smelter, southwestern Finland. The amounts of heavy metals (Cu, Ni, Zn, Fe) and mineral nutrients in bulk precipitation and throughfall were highest at 0.5 km. Although the canopy coverage was low at 0.5 km, the amounts of heavy metals intercepted by the canopy were extremely high. The proportion of foliar leaching relative to the wash-off of dry deposition from the needle surfaces decreased on moving towards the smelter for all elements, except for K. The high rate of K leaching from the needle tissues close to the smelter demonstrated that the K throughfall flux has been greatly altered by the heavy pollution load.     

Understorey vegetation along a heavy-metal pollution gradient in SW Finland

Understorey vegetation of Scots pine forests was studied along a 8-km transect running SE from a Cu-Ni smelter at Harjavalta, SW Finland. Long-term accumulation of heavy metals and sulphur in the forest ecosystem has drastically changed plant communities. Vegetation was almost absent up to a distance of 0.5 km from the smelter. The total coverage and the number of plant species increased with increasing distance from the smelter. Ordination by global non-metric multidimensional scaling (GNMDS) indicated that the floristic composition was differentiated in response to the pollution level. The main compositional gradient of GNMDS was correlated with the heavy metal concentrations in the organic soil layer and with the size of the overstorey trees. Vascular plants were more pollution-resistant than ground lichens, whereas mosses were the most sensitive plant group. In addition to heavy metals, nutrient imbalances and the considerably reduced water-holding capacity of the surface soil also restrict plant recolonisation on the degraded sites.     

Tidal salt marsh sediment in California, USA. Part 2: occurrence and anthropogenic input of trace metals

Surface sediment samples (0–5 cm) from 5 tidal salt marshes along the coast in California, USA were analyzed to investigate the occurrence and anthropogenic input of trace metals. Among study areas, Stege Marsh located in the central San Francisco Bay was the most contaminated marsh. Concentrations of metals in Stege Marsh sediments were higher than San Francisco Bay ambient levels. Zinc (55.3–744 μg g⁻¹) was the most abundant trace metal and was followed by lead (26.6–273 μg g⁻¹). Aluminum normalized enrichment factors revealed that lead was the most anthropogenically impacted metal in all marshes. Enrichment factors of lead in Stege Marsh ranged from 8 to 49 (median = 16). Sediments from reference marshes also had high enrichment factors (2–8) for lead, indicating that lead contamination is ubiquitous, possibly due to continuous input from atmospherically transported lead that was previously used as a gasoline additive. Copper, silver, and zinc in Stege Marsh were also enriched by anthropogenic input. Though nickel concentrations in Stege Marsh and reference marshes exceeded sediment quality guidelines, enrichment factors indicated nickel from anthropogenic input was negligible. Presence of nickel-rich source rock such as serpentinite in the San Francisco Bay watershed can explain high levels of nickel in this area. Coefficients of variation were significantly different between anthropogenically impacted and non-impacted metals and might be used as a less conservative indicator for anthropogenic input of metals when enrichment factors are not available.     

Compartmentation of metals in foliage of Populus tremula grown on soils with mixed contamination. I. From the tree crown to leaf cell level

In order to achieve efficient phytoextraction of heavy metals using trees, the metal allocation to aboveground tissues needs to be characterised. In his study, the distribution of heavy metals, macro- and micronutrients and the metal micro-localisation as a function of the leaf position and heavy metal treatment were analysed in poplars grown on soil with mixed metal contamination. Zinc was the most abundant contaminant in both soil and foliage and, together with cadmium, was preferentially accumulated in older foliage whereas excess copper and lead were not translocated. Changes in other element concentrations indicated an acceleration in aging as a consequence of the metal treatment. Excess zinc was irregularly accumulated inside leaf tissues, tended to saturate the veins and was more frequently stored in cell symplast than apoplast. Storage compartments including metabolically safe and sensitive subcellular sites resulted in sizable metal accumulation as well as stress reactions.     

Concentrations of two organic contaminants in precipitation, soils and plants in the Essex region of Southern Ontario

Recent research has indicated that the atmosphere is an important pathway by which pollutants enter terrestrial and aquatic ecosystems. We report here concentrations of PCBs and octachlorostyrene (OCS) in precipitation, soils and plants in Essex County, Ontario. The average PCB concentration in urban precipitation (23 ng litre(-1)) was lower than that previously reported for urban areas in the Great Lakes basin. Differences between sites and with varying wind directions were not significant. OCS concentrations in precipitation averaged 1.6 ng litre(-1). Concentrations of PCBs in soils were 2-3 orders of magnitude greater than in precipitation. Concentrations of these pollutants in city soils and plant roots were consistently higher than those from suburban and rural sites. Ratios of urban to suburban concentrations in soils and precipitation were approximately 5:1 for PCBs. However, concentrations of OCS were similar in urban and suburban samples of precipitation, soils and plant tissues. These comparisons suggest an urban source for PCBs, but not OCS. Concentrations of all contaminants in plant leaves, unlike those in precipitation, roots and soils, were relatively similar in urban and suburban areas. That similarity suggests that direct foliar uptake is not an important pathway for pollutant uptake in plants.     

Application of 16S rDNA-PCR amplification and DGGE fingerprinting for detection of shift in microbial community diversity in Cu-, Zn-, and Cd-contaminated paddy soils

Seven soils were sampled from farmland at different distances (0.01-5 km) from a copper and zinc smelter. The total contents of heavy metals in these soils ranged from 46 to 4895 mg Cu kg-1, 96 to 1133 mg Zn kg-1, and 6.9 to 28.8 mg Cd kg-1, respectively. The available fractions were highly correlated with total contents of the metals. In order to assess the impact of combined contamination of heavy metals on soil bacterial communities, denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplicons of 16S rDNA sequence of bacteria in soil was used. Bacterial community structure was affected to some extent by heavy metals. The number of DGGE bands in soils increased with increasing distance from the copper and zinc smelter. Clustering analysis of the DGGE profiles showed that bacteria in the seven soils belonged to three clusters. Bacterial communities in three soils sampled at 0.01-0.60 km from the smelter belonged to one cluster, and those in three soils sampled at 0.8-1.2 km from the smelter belong to another cluster. Bacterial community in soil farthest from the smelter belonged to a single cluster. This study demonstrated that heavy metal contamination decreased both biomass and diversity of bacterial community in the soil.     

Effects of heavy metal exposure on the condition and health of nestlings of the great tit (Parus major), a small songbird species

In this study we examined the possible effects of heavy metal exposure on the condition and health of great tit nestlings (Parus major) at four study sites along a pollution gradient near a large non-ferrous smelter in Belgium during three consecutive breeding seasons. Our results showed that nestlings were indeed exposed to large amounts of heavy metals. Excrements contained significantly higher concentrations of several heavy metals (silver, arsenic, cadmium, mercury, lead) near the pollution source than at study sites farther away. When taking into account the number of young in the nest at the time of sampling, nestling body mass and condition were significantly reduced at the most polluted site. Nestlings at the two most polluted sites fledged significantly later than at the least polluted site. We also observed growth abnormalities of the legs near the pollution source. Tarsus length, wing length and haematocrit values did not differ significantly among study sites.     

Transfer of cadmium, lead, and zinc from industrially contaminated soil to crop plants: a field study

The documeneed adverse health effects of soil Cd and Pb have led to public concern over soil contamination with metals. A 4-year field experiment was conducted to study the transfer of Cd, Pb, and Zn from soil contaminated by smelter flue-dust to crop plants grown in a rotation. The soil was amended with Pb?Zn smelter flue-dust (2-66.8 kg per 10 m(2) plot) to simulate the long-term effect that the smelting of non-ferrous metal ore has on arable soils. The treated soil became strongly contaminated with metals (Cd 3.2-106 mg/kg, Pb 146-3452 mg/kg, Zn 465-11 375 mg/kg). Concentrations of Cd, Pb, and Zn in barley grain, barley straw meadow bluegrass, red clover, and potatoes were generally low. The highest metal concentrations were found in potato tubers (intact), meadow bluegrass, and barley straw. The observed reduction in crop yield was probably the result of possible nutrient imbalances rather than of metal (Zn, Cu) phytotoxicities. Zn and Cd uptake by the plants can be described by the saturation (plateau) model (y = ax(b), b < 1). The relationship between Pb in the soil and plants was linear with an extremely low slope (0.0001-0.0003). No excessive dietary intake of Cd is expected when Cd concentrations in barley grain and potato tubers grown on the contaminated soil are not higher than 0.6 and 1.0 mg/kg, respectively. Based on the risk analysis and taking into account the saturation model of the soil-plant metal relationship, it was concluded that, under the conditions of this experiment (neutral soil pH), soil with Cd concentrations of up to 30 mg/kg is still safe for production of these crop plants.     

Heavy metals in urban soils of East St. Louis, IL, Part I: Total concentration of heavy metals in soils

The city of East St. Louis, IL, has a history of abundant industrial activities including smelters of ferrous and non-ferrous metals, a coal-fired power plant, companies that produce organic and inorganic chemicals, and petroleum refineries. A protocol for soil analysis was developed to produce sufficient information on the extent of heavy metal contamination in East St. Louis soils. Soil cores representing every borough of East St. Louis were analyzed for heavy metals--As, Cd, Cu, Cr, Hg, Ni, Pb, Sb, Sn, and Zn. The topsoil contained heavy metal concentrations as high as 12.5 ppm Cd, 14,400 ppm Cu, ppm quantities of Hg, 1860 ppm Pb, 40 ppm Sb, 1130 ppm Sn, and 10,360 ppm Zn. Concentrations of Sb, Cu, and Cd were well correlated with Zn concentrations, suggesting a similar primary industrial source. In a sandy loam soil from a vacated rail depot near the bank of the Mississippi River, the metals were evenly distributed down to a 38-cm depth. The clay soils within a half-mile downwind of the Zn smelter and Cu products company contained elevated Cd (81 ppm), Cu (340 ppm), Pb (700 ppm), and Zn (6000 ppm) and displayed a systematic drop in concentration of these metals with depth. This study demonstrates the often high concentration of heavy metals heterogeneously distributed in the soil and provides baseline data for continuing studies of heavy metal soil leachability.