The aim of this study was to explore how atmospherically derived soil pollution is affected by environmental processes at two typical boreal catchment landscape type settings: wetlands and forested areas. Measurements of hydrophobic organic compounds (HOCs) in forest soil and peat from an oligotrophic mire at various depths were performed at a remote boreal catchment in northern Sweden. HOCs in peat were evenly distributed throughout the body of the mire while levels of HOCs in the forest soil increased with increased amount of organic matter. Evaluation of HOC composition by principal component analysis (PCA) showed distinct differences between surface soils and deeper soil and peat samples. This was attributed to vertical transport, degradation and/or shifting sources over time. The calculated net vertical transport differed between surface layers (0.3%) and deeper soils (8.0%), suggesting that vertical transport conditions and processes differ in the deeper layers compared to the surface layers.

In the Athabasca oil sands region of northern Alberta, mining companies are evaluating reclamation using constructed wetlands for integration of tailings. From May to July 2008, reproductive performance of 40 breeding pairs of tree swallows (Tachycineta bicolor), plus growth and survival of nestlings, was measured on three reclaimed wetlands on two oil sands leases. A subset of nestlings was examined for i) feather corticosterone levels, ii) delayed-type hypersensitivity response, and iii) innate immune function. Nestlings on one of two wetlands created with oil sands process affected material (OSPM) were heavier and had greater wing-lengths, and mounted a stronger delayed-type hypersensitivity response compared those on the reference wetland. Corticosterone was significantly higher in male nestlings on one of two OSPM-containing wetland compared to the reference wetland. Body condition of 12-day-old female nestlings was inversely related to feather corticosterone. Under ideal weather conditions, reclaimed wetlands can support healthy populations of aerially-insectivorous birds. Under ideal weather conditions, tree swallow nestlings on reclaimed OSPM-affected wetlands are in good body condition and mount strong cell-mediated immune responses.

Federal agencies of several nations have or are currently developing guidelines for critical forest soil acid loads. These guidelines are used to establish regulations designed to maintain atmospheric acid inputs below levels shown to damage forests and streams. Traditionally, when the critical soil acid load exceeds the amount of acid that the ecosystem can absorb, it is believed to potentially impair forest health. The excess over the critical soil acid load is termed the exceedance, and the larger the exceedance, the greater the risk of ecosystem damage. This definition of critical soil acid load applies to exposure of the soil to a single, long-term pollutant (i.e., acidic deposition). However, ecosystems can be simultaneously under multiple ecosystem stresses and a single critical soil acid load level may not accurately reflect ecosystem health risk when subjected to multiple, episodic environmental stress. For example, the Appalachian Mountains of western North Carolina receive some of the highest rates of acidic deposition in the eastern United States, but these levels are considered to be below the critical acid load (CAL) that would cause forest damage. However, the area experienced a moderate three-year drought from 1999 to 2002, and in 2001 red spruce (Picea rubens Sarg.) trees in the area began to die in large numbers. The initial survey indicated that the affected trees were killed by the southern pine beetle (Dendroctonus frontalis Zimm.). This insect is not normally successful at colonizing these tree species because the trees produce large amounts of oleoresin that exclude the boring beetles. Subsequent investigations revealed that long-term acid deposition may have altered red spruce forest structure and function. There is some evidence that elevated acid deposition (particularly nitrogen) reduced tree water uptake potential, oleoresin production, and caused the trees to become more susceptible to insect colonization during the drought period. While the ecosystem was not in exceedance of the CAL, long-term nitrogen deposition pre-disposed the forest to other ecological stress. In combination, insects, drought, and nitrogen ultimately combined to cause the observed forest mortality. If any one of these factors were not present, the trees would likely not have died. This paper presents a conceptual framework of the ecosystem consequences of these interactions as well as limited plot level data to support this concept. Future assessments of the use of CAL studies need to account for multiple stress impacts to better understand ecosystem response.

Anthropogenic trace element emissions have declined. However, top soils all over the world remain enriched in trace elements. We investigated Pb and Cd migration in forest soils of a remote monitoring site in the Austrian limestone Alps between 1992 and 2004. Large spatial variability masked temporal changes in the mineral soil of Lithic Leptosols (Skeltic), whereas a significant reduction of Pb concentrations in their forest floors occurred. Reductions of concentrations in the less heterogeneous Cambisols (Chromic) were significant. In contrast, virtually no migration of Pb and Cd were found in Stagnosols due to their impeded drainage. Very low element concentrations (<1 μg l−1) in field-collected soil solutions using tension lysimeters (0.2 μm nylon filters) imply that migration largely occurred by preferential flow as particulate-bound species during intensive rainfall events. Our results indicate that the extent of Pb and Cd migration in soils is largely influenced by soil type. Comparison between soil solid phase and soil solution concentrations imply that trace element migration largely occurred by preferential flow as particulate-bound species.

Mt. Gongga area in southwest China was impacted by Hg emissions from industrial activities and coal combustion, and annual means of atmospheric TGM and PHg concentrations at a regional background station were 3.98 ng m-3 and 30.7 pg m-3, respectively. This work presents a mass balance study of Hg in an upland forest in this area. Atmospheric deposition was highly elevated in the study area, with the annual mean THg deposition flux of 92.5 μg m-2 yr-1. Total deposition was dominated by dry deposition (71.8%), and wet deposition accounted for the remaining 28.2%. Forest was a large pool of atmospheric Hg, and nearly 76% of the atmospheric input was stored in forest soil. Volatilization and stream outflow were identified as the two major pathways for THg losses from the forest, which yielded mean output fluxes of 14.0 and 8.6 μg m-2 yr-1, respectively.

Levels and chemical forms of heavy metals in forest, paddy, and upland field soils from the Red River Delta, Vietnam were examined. Forest soils contained high Cr and Cu levels that were higher in subsurface than in surface layers. Levels of Cu, Pb, and Zn that exceeded the limits allowed for Vietnamese agricultural soils were found in the surface layer of a paddy field near the wastewater channel of a copper casting village. High amounts of Zn accumulated in the surface soil of paddy fields close to a fertilizer factory and an industrial zone. In these cases, larger proportions of Cu, Pb, and Zn were found in the exchangeable and acid-soluble fractions compared to the low-metal soils. We conclude that no serious, large-scale heavy metal pollution exists in the Red River Delta. However, there are point pollutions caused by industrial activities and natural sources.

The increasing number of degraded soil areas caused by open cast mining activities has brought about a critical damage to the environment. The mine spoil must be ameliorated with anthropogenic interferences which consist of revegetating soils after organic matter amendment and provision of microbial diversity, to guarantee basic conditions for a sustainable soil biological activity. Five woody species, Acacia mangium Willd., Inga edulis Mart., Mimosa caesalpiniaefolia Benth, Parkia multijuga Benth., and Schinus terebinthifolia Schlecht. & Cham were cultivated under greenhouse conditions to evaluate the potential of plant establishment on cassiterite mining waste, considering the contribution of mycorrhizal fungi inoculation, organic compost, and thermophosphate amendment. The shoot height, dry weight, and nitrogen and phosphorus shoot contents were determined. Three species of nodulating legumes, A. mangium, M. caesalpiniaefolia, and S. terebinthifolia showed a great positive response to organic compost, termophosphate, and mycorrhizal inoculation, increasing the plant height and the shoot dry weight. Plants inoculated with arbuscular mycorrhizal fungi and fertilized with organic compost also increased their nitrogen and phosphorus shoot contents. The addition of organic compost and mycorrhizal fungi were essential for plant development and the reforestation of mining areas should be initiated with mycotrophic and nodulating legumes.

A pot experiment was conducted to study the effects of high concentrations of available Cu and Pb in soil originated from the vicinity of a copper foundry in Poland (Cu, 2,585–3,725 mg kg−1 d.wt.; Pb, 1,459–1,812 mg kg−1 d.wt.) on the growth and chemical constituents of Betula pendula seedlings. Control plants grew in unpolluted forest soil. Dry matter accumulation in the plants during the growing season and root/leaf mineral content were determined. Colonization of birch roots by ectomycorrhizal (ECM) fungi also was evaluated, as was soil dehydrogenase activity for influence of the metals on soil microorganisms. The heavy metals negatively affected seedling growth, ECM colonization, and soil dehydrogenase activity. A reverse relationship was found between ECM abundance and heavy metal concentrations in birch leaves, indicating the potential of mycorrhizas to protect the aboveground part of young silver birch seedlings from elevated environmental levels of Cu and Pb.

We investigated concentrations of dissolved organic carbon (DOC) in throughfall and soil solutions at 5, 15 and 40-cm depth in 16 Norway spruce and two Scots pine plots throughout Norway between 1996 and 2006. Average DOC concentrations ranged from 2.3 to 23.1 mg/l and from 1.1 to 53.5 mg/l in throughfall water and soil solutions, respectively. Concentrations of DOC in throughfall and soil waters varied seasonally at most plots with peaks in the growing season. By contrast to recently reported positive long-term trends in DOC concentrations in surface waters between 1986 and 2003, soil water data from 1996 to 2006 showed largely negative trends in DOC concentrations and no significant trends in throughfall. However, regression analysis for individual sites, particularly at 5- and 15-cm soil depths, showed that DOC concentrations in soil water were significantly and negatively related to non-marine sulphate (SO₄) and chloride (Cl⁻). The lack of a long-term increase in DOC in soil water in the period May 1996-December 2006 may be due to the relatively small changes in the deposition of SO₄ and Cl⁻ in this period.

After elevated concentrations of perfluorooctanoate (PFO) were found in river and groundwater in the vicinity of a fluoropolymer manufacturing facility, numerous soils at adjacent sites were sampled in 2007. Within a 5-km northeast-oriented sector around a probable point source, 20 forest sites were investigated and compared to deposition and groundwater data. PFO concentrations up to 600 µg/kg were detected in the soils, and PFO concentrations typically decreased toward deeper soil depths. In mixed or deciduous forests, maximum concentrations of PFO occurred in the topsoil, pointing to the favorable decomposition and incorporation of deciduous litter. PFO concentrations of the organic layer over the 20 sampling sites were interpolated using ordinary kriging. Highest PFO content in the organic layer was located about 500 m away from the point source in the regional wind direction, decreasing asymptotically outwards. Long-term monitoring data pointed to an accumulation of PFO over time in the organic layer. The data suggest that PFO might be released in the course of litter decomposition and transported toward deeper soil regions only gradually. The soils' PFO concentrations reflect the deposition data. The transport link toward groundwater is currently established in lysimeter studies.