heavy metals, metal deposition, metal toxicity, soil pollution
List of original publications
1.1. Copper and nickel pollution in terrestrial ecosystems
1.2. Plant responses to excess soil Cu and Ni
1.3. Phytoavailability of soil Cu and Ni
1.4. Ecological characteristics of Scots pine
1.5. Element cycles at the ecosystem level
1.6. Aims of the study
2. Material and methods
2.1. Study area
2.2. Emissions from the smelters
2.3. Bulk precipitation and stand throughfall
2.5. Needle sampling in the pine stands along the study gradient
2.6. Experimental approaches
2.6.1. Soil sampling along the gradient at Harjavalta
2.6.2. Artificial exposure treatment
2.6.3. Experimental conditions, harvesting and soil sampling at the end of the experiments
2.6.4. Chemical analysis of the greenhouse experiments
2.6.5. Calculations and statistical treatment of the greenhouse experiments
2.6.6. Pine seedling experiment in the field
2.7. Peat sampling
3. Results and discussion
3.1. Recent and past metal deposition at the study area
3.1.1. Bulk precipitation and stand throughfall
3.1.2. The extent of past metal deposition
3.2. Performance of Scots pine in a smelter-polluted environment at different phases of its life-cycle
3.2.1. History of the forests under study
3.2.2. Current growth rate of the study stands
3.2.3. Comparison with the experimental seedling cultures
3.2.4. Seed crop and seedling establishment
3.3. Availability of soil Cu and Ni to Scots pine
3.3.1. Soil and soil solution Cu and Ni concentrations as indicators of their availability
3.3.2. Cu and Ni concentrations as diagnostic criteria of toxicity
3.4. Biogeochemical cycling of elements in the studied forest ecosystems
3.4.1. Consequences of a long-term Cu and Ni exposure on element cycling
3.4.2. Canopy filtration of dry deposition as a source of element fluxes in the ecosystems
3.4.3. Foliar leaching of K
3.4.4. Nutrient retranslocation in pine foliage
3.4.5. Element losses via percolation water
3.4.6. Nutrient disturbances
List of Original Publications:
Nieminen, T.M., Derome, J. and Helmisaari, H.-S. 1999.
Interactions between precipitation and Scots pine canopies along a heavy-metal pollution gradient.
Environmental Pollution 106: 129â€”137.
Nieminen, T. M., Ukonmaanaho, L. and Shotyk, W. 2002.
Enrichment of Cu, Ni, Zn, Pb and As in an ombrotrophic peat bog near a Cu-Ni smelter in Southwest Finland.
The Science of the Total Environment 292: 81â€”89.
Nieminen, T. M. 2004.
Effects of soil copper and nickel on survival and growth of Scots pine.
Journal of Environmental Monitoring 6: 888â€”896.
Nieminen, T. M. and Saarsalmi, A. 2002.
Contents of Cu, Ni and Zn in smelterpolluted soil-plant systems.
Geochemistry: Exploration, Environment, Analysis 2: 167â€”174.
Nieminen, T. and Helmisaari H.-S. 1996.
Nutrient retranslocation in the foliage of Pinus sylvestris L. growing along a heavy metal pollution gradient.
Tree Physiology 16: 825â€”831.
Nieminen, T. M., Derome, J. and Saarsalmi, A. 2004.
The applicability of needle chemistry for diagnosing heavy metal toxicity to trees.
Water, Air, and Soil Pollution 157: 269â€”279.
The aim of my thesis was to evaluate the lifelong response of Scots pine to a chronic Cu and Ni exposure in the vicinity of a smelter complex, as well as to study the fate of the pollutants in the studied forest ecosystems. Four study sites were established in pure Scots pine stands growing along an esker at distances 0.5, 2, 4 and 8 km southeast from the main stack of the smelters. In addition, the response of Scots pine to soil Cu and Ni was also studied by performing simulation experiments in a greenhouse.
The rate of Cu and Ni deposition on the forests was estimated by monitoring the current Cu and Ni concentrations in bulk precipitation and stand throughfall, and by estimating the past pollution loads on the basis of the amounts of Cu and Ni accumulated in the surface peat of an adjacent ombrotrophic bog. The measured Cu and Ni deposition at the forest site nearest to the smelters did not appear to be a reliable estimate of current metal input into the ecosystem, because of the high level of internal metal cycling via soil dust. The elevated Cu and Ni concentrations in the surface peat sediments of the ombrotrophic bog were interpreted as signs of a higher level of Cu and Ni deposition in the past compared to current deposition in the immediate vicinity of the smelters. In addition, the vertical distribution pattern of Cu suggests that the input of Cu to the peat via atmospheric deposition is retained in the top-most peat layers, whereas Ni showed a more even vertical distribution pattern reflecting downward migration. Nickel appeared to be more mobile than Cu also in the polluted forest soils, but this was not reflected as relatively higher Ni uptake by pine roots. The uptake of both Cu and Ni corresponded to their soil contents in the smelter-polluted forest soil, although the uptake rate of inorganic Ni from an artificial quartz sand substrate was, in some cases, higher than that of Cu.
The performance of experimental pine seedlings cultivated in smelter-polluted soil was similar to that of the mature pine stands growing along the study gradient. The variation in the biomass of the seedlings appeared to be related both to the toxicity of Cu and Ni and to the differences in the nutrient status of the experimental soils. However, smelter-induced pollution may affect pines also indirectly through changes in soil nutrient status, which are difficult to distinguish from the natural variation in fertility. The autumnal nutrient retranslocation from senescing needles to overwintering tree compartments was less efficient at the most polluted site compared to that at further distances from the smelters. According to the results of the artificial exposure experiment the lethal threshold for Cu concentration in pine roots would be approx. 1000 mg kg-1, while the corresponding value for Ni would be 100 mg kg-1, thus indicating a higher toxicity of Ni. The corresponding thresholds for pine stem concentrations were 70 mg Cu kg-1 and 8 mg Ni kg-1. The needle concentrations did not appear to be reliable indicators of Cu and/or Ni toxicity. This was especially true in the field, where the surface contamination of needles by metal-containing particles in the heavily polluted environment further complicated the interpretation of the measured Cu and Ni concentrations. The chloroform washing did not remove all of the metal-containing material attached to the needle surfaces.