Regional air pollution in northeast Asia is an emerging environmental problem requiring long-term impact assessment of acidic deposition. In this study, the gridded distribution of nitrogen uptake led by both growing forests and harvested biomass for eight tree species: Japanese Larch, Red pine, Korean pine, Oak tree, Chestnut, Other Conifers, Other broad leaved trees, and Mixed forest was identified to estimate critical loads for nitrogen over South Korea. The gridded spatial distribution of averaged nitrogen uptake was mapped by 0.125° Latitude x 0.125° Longitude resolution. The results showed that net uptake of nitrogen led by both growth and harvested biomass was totaled at 438 molc ha-¹ year-¹ among which harvested biomass contribution was estimated to be 25 molc ha-¹ year-¹, yielding a very small fraction of total nitrogen uptake presumably due to the younger stages of forest in South Korea.

An intensive survey of mercury speciation was performed at a site on the Upper St. Lawrence River near Cornwall, Ontario, Canada with a history mercury contamination in sediments. Surface sediments were collected every 1.50 h. Total mercury (Hgtotal), methylmercury (MeHg), organic carbon, inorganic and organic sulphur were determined in the solid fraction. Dissolved Hgtotal, MeHg and dissolved organic carbon (DOC) were measured in pore waters. Concentrations of Hgtotal in the upper layers (first 5 cm) were high, ranging from 1.42 to 25.8 nmol g-¹ in solids and from 125 to 449 pM in pore waters. MeHg levels were also high, ranging from 4.34 to 34.1 pmol g-¹ in solids and from 40 to 96 pM in pore waters. This amounts to up to 1.4% of Hgtotal present as MeHg in solids and 64% in pore waters. A daily pattern for Hgtotal was observed in the solid fraction. The MeHg distribution in solids and pore waters was not correlated with Hgtotal or DOC, suggesting that the concentrations of MeHg are probably more influenced by the relative rates of methylation/demethylation reactions in the sediment-water interface. Acid volatile sulphide levels and DOC were inversely correlated with organic sulphur (Sorg) levels suggesting that both parameters are involved in the rapid production of Sorg. A positive correlation was also observed between Hgtotal and Sorg in solids (R = 0.87, p < 0.01) illustrating the importance of organic sulphur in the retention and distribution of Hg in the solid fraction of the sediments. The results suggest that variations of Hgtotal concentrations in Upper St. Lawrence River surface sediments were strongly influenced by the formation/deposition/retention of organic sulphur compounds in the sediment-water interface.

Mercury and organic carbon concentrations vary dynamically in streamwater at the Sleepers River Research Watershed in Vermont, USA. Total mercury (THg) concentrations ranged from 0.53 to 93.8 ng/L during a 3-year period of study. The highest mercury (Hg) concentrations occurred slightly before peak flows and were associated with the highest organic carbon (OC) concentrations. Dissolved Hg (DHg) was the dominant form in the upland catchments; particulate Hg (PHg) dominated in the lowland catchments. The concentration of hydrophobic acid (HPOA), the major component of dissolved organic carbon (DOC), explained 41-98% of the variability of DHg concentration while DOC flux explained 68-85% of the variability in DHg flux, indicating both quality and quantity of the DOC substantially influenced the transport and fate of DHg. Particulate organic carbon (POC) concentrations explained 50% of the PHg variability, indicating that POC is an important transport mechanism for PHg. Despite available sources of DHg and wetlands in the upland catchments, dissolved methylmercury (DmeHg) concentrations in streamwaters were below detection limit (0.04 ng/L). PHg and particulate methylmercury (PmeHg) had a strong positive correlation (r ² = 0.84, p < 0.0001), suggesting a common source; likely in-stream or near-stream POC eroded or re-suspended during spring snowmelt and summer storms. Ratios of PmeHg to THg were low and fairly constant despite an apparent higher methylmercury (meHg) production potential in the summer. Methylmercury production in soils and stream sediments was below detection during snowmelt in April and highest in stream sediments (compared to forest and wetland soils) sampled in July. Using the watershed approach, the correlation of the percent of wetland cover to TmeHg concentrations in streamwater indicates that poorly drained wetland soils are a source of meHg and the relatively high concentrations found in stream surface sediments in July indicate these zones are a meHg sink.

Particulate matter measurements (PM₁₀, PM₂.₅) using a beta radiation attenuation monitor were performed at the Akrotiri research station (May 2003-March 2006) on the island of Crete (Greece). The mean PM₁₀ concentration during the measuring period (05/02/03-03/09/04) was equal to 35.0 ± 17.7 μg/m³ whereas the mean PM₂.₅ concentration (03/10/04-04/02/06) was equal to 25.4 ± 16.5 μg/m³. The aerosol concentration at the Akrotiri station shows a large variability during the year. Mean concentrations of particulate matter undergo a seasonal change characterised by higher concentrations during summer [PM₁₀, 38.7 ± 10.8 μg/m³ (2003); PM₂.₅, 27.9 ± 8.7 μg/m³ (2004) and 27.8 ± 9.7 μg/m³ (2005)] and lower concentrations during winter [PM₁₀, 28.7 ± 22.5 μg/m³ (2003/2004); PM₂.₅, 21.0 ± 13.0 μg/m³ (2004/2005) and 21.4 ± 21.9 μg/m³ (2005/2006)]. Comparative measurements of the PM₁₀ concentration between the beta radiation attenuation monitor, a standardized low volume gravimetric reference sampler and a low volume sequential particulate sampler showed that PM₁₀ concentrations measured by the beta radiation attenuation monitor were higher than values given by the gravimetric samplers (mean ratio 1.17 ± 0.11 and 1.21 ± 0.08, respectively). Statistical and back trajectory analysis showed that elevated PM concentrations (PM₁₀, 93.8 ± 49.1 μg/m³; PM₂.₅: 102.9 ± 59.9 μg/m³) are associated to desert dust events. In addition regional transport contributes significantly to the aerosol concentration levels whereas low aerosol concentrations were observed during storm episodes.

A conceptual model of solute transport with bioremediation processes using sawdust as a matrix to improve the efficiency of bioremediation in porous media is presented. The transport part of the model solves the advection dispersion differential equations and the reaction part describes the heterotrophic metabolisms of several groups of bacteria. The bacterial growth is formulated using the double Monod kinetic equation. The model depicts the utilization of oxygen, nitrate, manganese, iron oxides and sulfate as electron acceptors for oxidation of organic carbon in porous media. Exchange between the different phases (mobile pore water phase, bio phase and matrix phase) is also considered in this model. Model parameters were adopted from literature on bioremediation processes. Feasibility and applicability of parameters were assessed by conducting a laboratory soil-sawdust columns experiments and comparing the simulated results with the experimental data. The results indicate that sawdust could be employed as low-cost materials to enhance the bioremediation processes in porous media. While the availability of organic carbon is one of the most important factors that affect bacterial activity in porous media, this study demonstrates that using sawdust as a carbon source can improve the bacterial activity and increase the column permeability.

It is hypothesized that episodic introductions of road salt severely disrupt the soil nitrogen cycle at a range of spatial and temporal scales. A field-scale study has confirmed impacts on the nitrogen cycle in soil, soil solution and river samples. There is evidence that ammonium-N retention on cation exchange sites has been reduced by the presence of sodium ions, and that ammonium-N has been flushed from the exchange sites. Increases in soil pH have been caused in naturally acidic uplands. These have enhanced mineralization of organic-N, especially nitrification, leading to a reduction in the mineralizable-N pool of roadside soils. There is evidence to support the hypothesis that organic matter content has been lowered over decades either through desorption or dispersal processes. Multiple drivers are identified that contribute to the disruption of nitrogen cycling processes, but their relative importance is difficult to quantify unequivocally. The influence of road salt on soil and soil solution declines with distance from the highway, but impacts on water chemistry in a local stream are still strongly evident at some distance from the road.

The concentrations of Pb, Cd, Cr, Mn and Fe were evaluated in leaves, stem and root of the Scirpus americanus and Typha latifolia aquatic macrophytes, which were collected from Tanque Tenorio, an artificial lagoon highly polluted by municipal and industrial wastewater. Some S. americanus and T. latifolia plants were collected from four different sites within Tanque Tenorio. The sites were chosen regarding their proximity with the main channel discharging wastewater into the lagoon. The results showed that S. americanus and T. latifolia have the ability to extract Pb, Cd, Cr, Mn and Fe from their water surroundings; on the whole, the roots presented higher concentrations of heavy metals than the stem and the leaves. The highest accumulation of heavy metals was observed in plants growing at the site near the channel entering the lagoon. S. americanus accumulated more Pb, Cr, Mn and Fe than T. latifolia; Cd concentrations were comparably the same in both species. This study provides information in relation to aquatic plants growing in polluted waters, which accumulate heavy metals. These findings are of interest pertaining to the removal processes for treating aquatic systems with heavy metal content.

In this study, heavy metal content (Cr, Cu, Mn, Ni, Zn) was determined in sediments and different organs of Rumex obtusifolius L. and Polygonum lapathifolium L. (Polygonaceae), Urtica dioica L. (Urticaceae) and Xanthium strumarium L. (Asteraceae) species. These species grow ubiquitously and vigorously on the periodic flooding areas of Nilüfer stream which have been polluted by different local industrial activities. Below and above-ground parts of plant samples and their sediments were analyzed by ICP-MS for their elemental contents. In general, the variations in the heavy metal content in sediments are reflected in heavy metal status of plant organs. However, this variation depends on plant species and heavy metals. R. obtusifolius, U. dioica and X. strumarium species have elevated levels of Cr, Cu, Ni, and Zn whereas Mn was observed only in P. lapathifolium. The contribution of different organs to the accumulation capacity of the total phytomass is specific to species.

Otoliths of black bream (Acanthopagrus butcheri) collected from the Swan River Estuary were analysed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) to measure concentrations of 14 trace metals. Trace metal concentrations in the otoliths may be related to the environmental exposure history of fish to contamination. The following metal isotopes were investigated: aluminium (²⁷Al), calcium (⁴⁴Ca), manganese (⁵⁵Mn), iron (⁵⁷Fe), copper (⁶⁵Cu), zinc (⁶⁶Zn), strontium (⁸⁸Sr), cadmium (¹¹¹Cd), tin (¹²⁰Sn), barium (¹³⁸Ba), mercury (²⁰²Hg), lead (²⁰⁸Pb) and the metalloids arsenic (⁷⁵As, ⁷⁷As) and selenium (⁸²Se). Significant differences in otolith trace metal composition were found between sampling sites. Lead and ⁵⁷Fe were consistently lower in downstream fish relative to upstream fish, while ⁸⁸Sr varied with the salinity gradient in the urban estuary. Lead and ⁵⁷Fe followed similar patterns within the otoliths, and appeared to provide the best discriminatory power for relating otolith metal concentration to the environmental history of the fish.

The selectivity and uptake capacity of horticultural peat available in Romania was evaluated with respect to the removal of Cd(II), Cr(VI) and Pb(II) ions from aqueous solution. The kinetics, sorption capacities, selectivity and pH dependence of sorption were determined. The influence of metal concentration in solution is discussed in the terms of Langmuir and Freundlich isotherm and constants. Sorption capacities increased with increasing metal concentration in solution. For solutions containing 300 mg/l of metal, the observed uptake capacities were 20 mg Cd(II)/g peat, 15 mg Cr(VI)/g peat and 30 mg Pb(II)/g peat. The study proved that horticultural peat is a suitable material for the removal of the studied heavy metal ions from aqueous solutions, achieving removal efficiencies higher than 90%, and could be considered as a potential material for treating effluent polluted with Cd(II), Cr(VI) and Pb(II) ions.