Heavy Metal Pollution Gradient Research Articles

Diversity and structure of Chironomidae (Diptera) communities along a gradient of heavy metal contamination in a subarctic watercourse

Community structure of chironomid larvae was investigated along a gradient of heavy metal pollution in the subarctic lakes of the Pasvik watercourse, bordering Northern Norway and Russia. Sixty taxa were present in the four investigated lakes. Species richness was lower in Lake Kuetsjarvi, nearest the main source of pollution, relative to the more distant lakes, and Simpson's diversity index was similarly highest in the less polluted site with higher maximum depth. The number of orthoclad chironomid species was considerably higher at the least contaminated sites, whereas the relative abundance of Orthocladiinae was highest at the most polluted site. Chironomid density increased with increasing distance from the main source of heavy metal pollution, especially in the subfamilies Tanypodinae and Chironominae, and total chironomid biomass was significantly higher at the least polluted site. Canonical correspondence analysis revealed spatial patterns consistent with species-specific tolerance to the heavy metal concentrations. Protanypus morio, Monodiamesa bathyphila, Chironomus spp., Polypedilum scalaenum gr. and Sergentia coracina seemed to be tolerant to heavy metal contamination, occurring most commonly at the most polluted sites. In contrast, Heterotrissocladius subpilosus, Psectrocladius semicirculatus/sp. , Chironomus anthracinus, Pagastiella orophila, Cladotanytarsus iucundus, and Tanytarsus spp. appeared to be more sensitive taxa, being common at the least polluted sites, but rare or absent at the two sites close to the pollution sources. Densities of Procladius ( Holotanypus) spp., Tanytarsus spp. and Chironomus anthracinus were negatively correlated with heavy metal concentrations and these taxa appeared to be the best indicators of heavy metal contamination.

Trends in detoxification enzymes and heavy metal accumulation in ground beetles (Coleoptera: Carabidae) inhabiting a gradient of pollution

Non-specfic carboxylesterase and glutathione S-transferase activity was measured in the ground beetle, Pterosthicus oblongopunctatus (Coleoptera: Carabidae), from five sites along a gradient of heavy metal pollution. A previous study determined that beetles from the two most polluted sites (site codes OLK2 and OLK3) were more susceptible to additional stressors compared with beetles from the reference site (Stone et al., Environ. Pollut. 113, 239–244 2001), suggesting the possibility of physiological impairment. Metal body burdens in ground beetles from five sites along the gradient ranged from 79 to 201 μg/g Zn, 0.174 to 8.66 μg/g Pb and 1.14 to 10.8 μg/g Cd, whereas Cu seemed to be efficiently regulated regardless of metal levels in the soil. Beetle mid- and hindguts were homogenized and the soluble fraction containing glutathione S-transferase (GST) and carboxylesterase (CaE) was assayed using kinetic analyses. Significantly higher levels of GST were found only in female beetles from the most polluted sites (OLK2 and OLK3; P=0.049, P<0.001, respectively) compared with the reference site (OLK7). In addition, OLK3 females had significantly higher levels of CaE compared with the reference beetles ( P=0.01). Male beetles did not differ in enzyme activity along the metal gradient. Overall, obvious trends in detoxification enzymes were not detected in ground beetles in association with metal body burdens.

Time to death response in carabid beetles exposed to multiple stressors along a gradient of heavy metal pollution

We investigated the responses of invertebrates inhabiting polluted environments to multiple stressors. Carabid beetles ( Pterostichus oblongopunctatus F.) were subjected to food deprivation and insecticide treatment (dimethoate) to resolve trends associated with a gradient of heavy metal pollution. Metal concentrations along the gradient of five sites ranged from approximately 150 to 10,500 mg/kg Zn, 136 to 2600 mg/kg Pb, and 0.84 to 81.9 mg/kg Cd. There was no difference in body mass along the pollution gradient. However, the beetles originating from the most contaminated sites were significantly less tolerant to food deprivation than beetles from the reference site. Median survival time was 120 h for the two most polluted sites, compared with 168 h at the reference site. Beetles from the two most polluted sites were also significantly more susceptible to dimethoate at 0.1 μg active ingredient/beetle. Median survival times were 12 and 123 h for beetles from the two most polluted sites and 359 h for the reference site. Carabid beetles exposed to chronic pollution, therefore, exhibit elevated susceptibility to additional stressors.

Decomposition of coniferous forest litter along a heavy metal pollution gradient, south-west Finland

The decomposition of Scots pine ( Pinus sylvestris) fine root and needle litter was examined along a heavy metal pollution gradient in the vicinity of Harjavalta Metals Smelter complex at Harjavalta, south-west Finland. The study area was found to exhibit a defined gradient of copper and nickel soil contamination along a 8 km long transect starting at 0.5 km from the point emission source with the highest levels found at this site. The background site is located 200 km from the point source. The majority of the heavy metals are confined to the soil organic layer. Litter decomposition and litter quality were compared between litter types after 12, 18, and 30 months incubation at each of four sites. The analyses clearly showed differences in accumulated mass loss, C:N ratio, and nutrient composition that were related to the site of incubation. Needle and fine root litter that was incubated at 0.5 km had a lower accumulated mass loss, 28.1 and 40.9%, respectively, over time when compared to litter incubated at the background site (37.9 and 50.9%, respectively). Concentrations of exchangeable cations in the litter incubated at 0.5 km were considerably less. The heavy metal contamination may provide an explanation for the amount of mass lost and the litter quality through impacts on the soil microbiota.

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.

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.

Effects of vitality fertilization on the resin flow and vigour of Scots pine in Finland

The vitality and defence of Scots pine were measured in order to study how different fertilizer combinations affect these traits, and to determine whether an increase in growth leads to reduced defence as predicted by the theories based on the assumption of the existence of a trade-off between growth and carbon-based defence compounds. Stem diameter growth and vigour index were measured as indicators of vitality and stem resin flow and the concentration of phloem phenolics were used as indicators of defence level. Fertilizer treatments containing nitrogen had a growth-promoting effect and the vigour index was higher in the nitrogen-fertilized treatments than in the control and non-nitrogenous fertilizer treatments. Four of the ten experimental sites were situated along a heavy metal pollution gradient at 0.5, 2.5, 4 and 8 km distance from the emission source. The vigour index in the severely polluted site closest to the emission source was considerably lower than that in the other three sites along the gradient, but even there nitrogen gave a clear growth response. In spite of the large within- and between-tree variation in resin flow, the average resin exudation differed little between the experimental sites. In most sites the resin flow was highest in the control treatment. A weak negative correlation was found between resin flow and vigour index. In the pollution gradient the mean resin flow was lowest at the most polluted site and increased along the gradient up to 4 km from the emission source. The phenolic concentration of the phloem was not affected by fertilization in any of the experiments apart from the severely polluted one. Indications of a weak negative linear correlation between vigour index and phloem phenolics were found. There was no significant correlation between the phenolic concentration and the amount of resin flow in any of the different sites. Except for the liming treatment in the polluted experiments, we did not detect any response to non-nitrogenous fertilizer treatments.

Molecular characterization of Metallothionein-cDNA of Sparus aurata used for detecting heavy metal pollution along the Mediterranean coast of Israel

Members of the fish family Sparidae are abundant in various continental shelf habitats along the Mediterranean, including relatively clean and polluted areas. The levels of metallothionein (MT)-mRNA in their liver is suggested here as a bioindicator parameter for the detection of heavy metals in Mediterranean marine habitats. A complete MT-cDNA was cloned from the liver of metal-induced Sparus aurata and used to evaluate the MT-mRNA levels in the livers of the abundant coastal sparid species, Lithognathus mormyrus, both after laboratory induction by cadmium and in fish sampled along a pollution gradient at Haifa Bay, the Mediterranean coast of Israel. It is concluded that the MT-mRNA in L. mormyrus liver is a good bioindicator of heavy metal pollution in the marine environment, because of the following: it is heavy metal-inducible; its level is turned off rather rapidly after the elimination of the inducing agents; and it is shown to be correlated to a heavy metal pollution gradient in a natural marine habitat.

Growth and mortality of nestling great tits (Parus major) and pied flycatchers (Ficedula hypoleuca) in a heavy metal pollution gradient.

We studied nestling growth, growth abnormalities, mortality and breeding success of two hole-nesting passerines, the great tit (Parus major) and the pied fly-catcher (Ficedula hypoleuca), at 14 study sites around a copper smelter complex in Harjavalta, south-west Finland in 1991-1993. The main pollutants in the area are heavy metals and sulphuric oxides. Exposure of birds to heavy metals was shown by measuring their faecal concentrations. Copper, nickel and lead contents of nestling faeces were high near the factory and decreased with distance away from the pollution source. F. hypoleuca nestlings suffered high mortality very close to the factory complex, but did relatively well at all other sites. Breeding success of P. major was below background levels up to 3-4 km from the pollution source and nestlings grew poorly close to the factory. Growth abnormalities of legs and wings in F. hypoleuca nestlings were significantly more common near the factory than farther away. In contrast, F. hypoleuca nestlings grew equally well at all distances. The poor breeding success of F. hypoleuca close to the factory complex is probably related to the high amount of heavy metals in its diet, and low availability of calcium-rich food items may enhance this effect. We suggest that the poor breeding success of P. major is related to habitat changes that have taken place around the factory. The different responses of these two bird species are probably due to their different diet. Our results show convincingly that species-specific differences in response should be carefully considered when planning schemes for air pollution monitoring.

Nutrient retranslocation in the foliage of Pinus sylvestris L. growing along a heavy metal pollution gradient.

Retranslocation of N, P, K, Ca, Mg, Mn, Fe, Zn, Cu and Ni within the foliage of Scots pine (Pinus sylvestris L.) was studied during autumnal needle senescence along a heavy-metal pollution gradient in western Finland. The stands were located at distances of 0.5 (Har 0.5), 4 (Har 4) and 8 km (Har 8) to the southeast of a copper-nickel smelter at Harjavalta. A background study stand was located at Hämeenkangas (Häm), 60 km northeast of the smelter. During needle senescence, the mobile nutrients N, P and K decreased by 67-88% and needle dry mass decreased by 31-43%. Retranslocation of P and K was less efficient in the stand nearest the smelter (Har 0.5) than in the other stands. During needle senescence at stand Har 0.5, heavy metal content either decreased slightly (Zn, Ni) or increased (Fe, Cu), whereas in the background study stand, retranslocation efficiency of Cu was 75%. Net throughfall (the amount of a nutrient in throughfall minus the amount in open precipitation) was higher in stand Har 0.5 than in stand Har 8 for all of the elements measured, except N and P which were intercepted by the canopy. In stand Har 8, deposition of S, Cu and Ni was intercepted by the canopy, and net throughfall of Fe and Zn was very low. In contrast, S and heavy metal contents of net throughfall in stand Har 0.5 were greater than the decrease in these elements in the needles indicating that accumulation on needle surfaces and subsequent wash-off accounted for a major part of the fluxes. Furthermore, the Cu content in net throughfall during the senescence period was higher than the original Cu content of the needles in July, providing additional evidence that much of the needle Cu content was comprised of dry deposits of Cu on the needle surface.

Breeding Performance of Tengmalm's Owl in a Heavy Metal Pollution Gradient

Breeding performance and liver accumulation of metals in Tengmalm's owl and liver accumulation in its prey species (small mammals) were studied in a heavy metal pollution gradient from a smelter in northern Sweden. Owls breeding in nest boxes were studied in 1981-82 and 1984-85 and represented the situation during two different vole population cycles. In general, breeding performance decreased with decreasing distance to the smelter. This applied to breeding population density (% nest boxes with ≥ 1 egg), clutch size (except in 1985), breeding success, and to embryo/nestling survival. Heavy metal contamination of the owls' prey by arsenic, cadmium, lead, and mercury increased towards the smelter. Despite this, Tengmalm's owl nestlings did not show a corresponding increase in metal accumulation in their liver tissue, except for arsenic. According to snap-trapping data, the supply of voles (owls' staple food) in late spring was less near the smelter than in the control area in 2 out of 3 years. Although the study was performed in very pronounced heavy metal polluted environments, direct metal toxicity effects upon the breeding performance of the owls seemed unlikely. Instead, a reduced food supply is likely to have caused a reduction in the breeding performance of the owls. Heavy metal and sulphur dioxide pollution could have been important factors limiting the small mammal populations in the heavily contaminated study area.

Vitality fertilization of Scots pine stands growing along a gradient of heavy metal pollution: short-term effects on microbial biomass and respiration rate of the humus layer.

In 1992 forest vitality fertilization experiments were established on a heavy metal deposition gradient with four treatments in three replications at distances of 0.5, 4 and 8 km from a Cu-Ni smelter in order to estimate their impact on the disturbed forest ecosystem. The increase in Cu concentration in the humus (F/H) layer of the Calluna site type Scots pine (Pinus sylvestris) stands from ca. 300 to 8000 mg kg(-1) d.m. (dry matter) along the 8 km long transect towards the smelter resulted in declining soil microbial biomass and soil respiration activity. Three independent measurements of microbial biomass: C(mic)-FE (fumigation extraction), C(mic)-SIR (substrate induced respiration), and ATP have been used together with an indicator of fungal biomass (ergosterol) and microbial activity (soil respiration). Within this Cu pollution range, all the measured microbial biomass levels declined to 10%-28% of the control plot values and activity assessed by respiration was lowered to 16%. Liming has increased the C(mic)-SIR and respiration rate. Treatments with test fertilizer, made from grounded apatite, did not result in different microbial biomass and respiration rate values compared to the respective controls along the whole gradient. Nitrogen + lime treatments resulted in similar changes to lime alone. No changes, as compared to the respective control, could be detected with nitrogen fertilization at the less polluted end of the gradient.

Decomposer animal communities in forest soil along heavy metal pollution gradient.

Responses of soil decomposer animals to heavy metal contamination and to concomitant changes in organic matter quality and quantity and in soil microbial biomasses have been studied along a pollution gradient from a Cu-Ni smelter. Samples have been taken separately for nematodes, enchytraeids and microarthropods 0.5, 2 and 8 km from the smelter. Special attention has been paid to the changes in the collembolan fauna. The sampling sites have been located in homogeneous Scots pine ( Pinus sylvestris) forests with podsolic soil profiles. In addition, an experiment has been carried out in which intact soil cores have been transferred in mesh baskets between the sites 2 and 8 km from the smelter (control samples have been transferred within the sites). Although most soil animals seemed to be quite resistant to direct and indirect effects of heavy metals, results indicate that certain soil animals like enchytraeids can be useful and easy to monitor when the effects of heavy metals on soil decomposition systems are assessed.

Copper in Scots pine forests around a heavy-metal smelter in south-western Finland

Distribution and fluxes of copper within Pinus sylvestris stands were studied during 1992–1994 along a heavy-metal pollution gradient in south-western Finland. The stands are situated at distances of 0.5, 4 and 8 km from a copper-nickel smelter that started operating in 1945 at Harjavalta. According to the results, copper concentrations in the soil, in the understorey vegetation and in the trees increased steeply towards the smelter. Almost 50 years' accumulation of heavy metals in the soil has caused direct toxic effects to soil microbes, thus decreasing decomposition and nutrient mineralisation. During the past few years, sulphur and heavy metal emissions from the copper and nickel smelter have been radically decreased. However, the heavy metals which have been accumulating in the soil for decades continue to affect the vegetation for a long time through soil processes. Consequently, long-term accumulation in the soil has to be taken into account when determining the critical loads of forest ecosystems for heavy metals.

Changes in fruitbody production of mycorrhizal and litter decomposing macromycetes in heavy metal polluted coniferous forests in North Sweden

Basidiomycete fruitbodies growing in coniferous forests along a complex heavy metal pollution gradient in north Sweden were identified and counted over a 4 yr period. The dominant metals in the humus layer were As, Cd, Cu, Pb, and Zn. Pb occurred at the highest levels in a range of 80 to 8500 μg g−1 dry wt. Both the number of fruitbodies and the number of fruiting species decreased strongly with increasing pollution level. A few species appeared to sustain the metal loads. Many of these were ectomycorrhizal fungi. The relationship between fruitbody frequencies and plant species composition were also studied statistically although no obvious relations were found. Metal content of the fruitbodies of six species were also analyzed and their bioaccumulation calculated. Amanita muscaria accumulated Cd efficiently.