Despite many studies of the N₂O emission, there is a lack of knowledge on the role of subsoil for N₂O emission, particularly in sandy soils. To obtain insight into the entrapment, diffusion, convection and ebullition of N₂O in the soil, the N₂O concentration in the soil atmosphere was measured over a period of 1 year in 4 lysimeters (agricultural soil monoliths of 1 m2 x 2 m) at 30, 50, 80, 155, and 190 cm depth with altogether 86 gas probes. Additionally the N₂O emission into the atmosphere was measured in 20 closed chambers at the soil surface. Concurrently the soil temperature and soil water content were recorded in order to quantify their effects on the fate of N₂O in the soil. Results of the continuous measurements between January and December 2006 were: N₂O concentrations were highest in the deeper soil; maximum concentration was found at a depth of 80 cm, where the water content was high and the gas transport reduced. The highest N₂O concentration was recorded after 'special events' like snowmelt, heavy rain, fertilization, and grubbing. The combination of fertilization and heavy rain led to an increase of up to 2,700 ppb in the subsoil.

The mobility of mercury (Hg) deposited on soils controls the concentration and toxicity of Hg within soils and in nearby streams and lakes, but has rarely been quantified under field conditions. We studied the in situ partitioning of Hg in the organic top layer (mor) of podsols at two boreal forest sites differing in Hg deposition and climatic regime (S. and N. Sweden, with pollution declining to the north). Soil solution leaching from the mor layer was repeatedly sampled using zero-tension lysimeters over 2 years, partly in parallel with tension lysimeters. Concentrations of Hg and dissolved organic carbon (DOC) were higher while pH was lower at the southern site (means ± SD: Hg = 44 ± 15 ng L-¹, DOC = 63.0 ± 31.3 mg L-¹, pH = 4.05 ± 0.53) than at the northern site (Hg = 22 ± 6 ng L-¹, DOC = 41.8 ± 12.1 mg L-¹, pH = 4.28 ± 0.43). There was a positive correlation over time between dissolved Hg and DOC at both sites, even though the DOC concentration peaked during autumn at both sites, while the Hg concentration remained more constant. This correlation is consistent with the expected strong association of Hg with organic matter and supports the use of Hg/C ratios in assessments of Hg mobility. In the solid phase of the overlying Of layer, both Hg concentrations and Hg/C ratios were higher at the southern site (means ± SD: 0.34 ± 0.06 μg g-¹ dw and 0.76 ± 0.14 μg g-¹ C, respectively) than at the northern site (0.31 ± 0.05 μg g-¹ dw and 0.70 ± 0.12 μg g-¹ C, respectively). However, concentrations in the solid phase differed less than might be expected from the difference in current atmospheric input, suggesting that the fraction of natural Hg is still substantial. At both sites, Hg/C ratios in the upper half of the mor layer were only about two thirds of those in the lower half, suggesting that the recent decrease in anthropogenic Hg deposition onto the soil is offset by a natural downward enrichment of Hg due to soil decomposition or other processes. Most interestingly, comparison with soil leachate showed that the average Hg/C ratios in the dissolved phase of the mor layers at both sites did not differ from the average Hg/C ratios in the overlying solid organic matter. These results indicate a simple mobilisation with negligible fractionation, despite differences in Hg deposition patterns, soil chemistry and climatic regimes. Such a straight-forward linkage between Hg and organic matter greatly facilitates the parameterisation of watershed models for assessing the biogeochemical fate, toxic effect and critical level of atmospheric Hg input to forest soils.

Lentic wetlands are usually regarded as the most important natural freshwater sources of methane (CH₄) and nitrous oxide (N₂O) to the atmosphere, and very few studies have quantified the importance of lowland streams in trace gas emissions. In this study, we estimated fluxes of CH₄ and N₂O in three macrophyte-rich, lowland agricultural streams in New Zealand, to place their trace gas emissions in context with other sources and investigate the value of minimising their emissions from agricultural land. All three streams were net sources of both gases, with emission of CH₄ ranging from <1 to 500 μmol m-² h-¹ and of N₂O ranging from <1 to 100 μmol m-² h-¹ during mid-summer. For CH₄, both turbulent diffusion across the surface and ebullition of sediment gas bubbles were important transport processes, with ebullition accounting for 20-60% of the emissions at different sites. The emissions were similar on a per area basis to other major global sources of CH₄ and N₂O. Although small on a catchment scale compared to emissions from intensively grazed pastures, they were significant relative to low-intensity pastures and other agricultural land uses. Because hydraulic variables (viz. depth, velocity and slope) strongly influence turbulent diffusion, complete denitrification can best proceed to N₂ as the dominant end-product (rather than N₂O) in riparian wetlands, rather than in open stream channels where N₂O fluxes are sometimes very large.

Source apportionment analysis was used to identify the factors contributing to atmospheric pollution at a monitoring location in the Southeast of Spain, a well documented area with an arid climate and high insolation favouring two sources of particulate matter: secondary transformation in the atmosphere and resuspension of crustal dry soils to the air. These conditions are further complicated by numerous industrial facilities in the area of the historical city of Cartagena. This paper describes the air quality of an area which includes a zinc metallurgical industry, a petrochemical factory, an oil power station, a shipyard and natural phenomena including African dust transport and resuspension of regional and/or local crustal materials. Major and trace element concentrations in PM10 and PM2.5 were determined at two monitoring stations in Cartagena (one PM10 sampler located at a traffic hotspot and the PM2.5 sampler at a suburban station), during 2004 and 2005. Results showed that in the PM10 fraction, the zinc metallurgical activity was linked to high levels of Cd, Zn and Pb; shipyard emission was associated with high levels of Cr and Ni; and high Ni and V levels were associated with the secondary aerosol indicating the contribution from oil combustion (oil-fired power station or petrochemical facilities). In the PM2.5 size fraction, the zinc source is defined by Zn and Pb; V, Ni and As appear with the oil combustion emissions. In contrast to PM10, shipyard activity is not consistently defined. Consistent sources found in both size fractions include crustal materials and traffic emissions.

The geochemical characteristics of rills draining pyrite-chalcopyrite tailings impoundments and of bordering streams were investigated at the ophiolite-hosted Libiola and Vigonzano abandoned massive sulphide mines, northern Apennines Italy. Water samples were analysed for major and trace chemical composition, hydrogen and oxygen isotope composition, and sulphur isotope composition of aqueous sulphate. Sulphur isotope composition was determined also for some samples of ore sulphides. At Libiola, the newly acquired chemical results on waters corroborate those from previous investigations, thus providing additional support to existing geochemical models in terms of metal distribution, solid phases precipitation, reaction path modelling and mixing reaction paths, and environmental problems. At Vigonzano, the chemical characteristics of waters are similar to those at Libiola. In both localities, solution-secondary phase equilibria estimated using an updated thermodynamic dataset account for mineralogy in the field, including poorly crystalline phases like jurbanite and hydrowoodwardite. The hydrogen and oxygen isotope composition of waters at Libiola and Vigonzano agrees with their meteoric origin. Acid to neutral mine waters do not show any significant isotope shift with respect to the initial water, in spite of the oxidation of even large amounts of pyrite/chalcopyrite ore. The sulphur isotope composition of aqueous sulphate in mine rills at Libiola (δ ³⁴S = 5.6 to 8.5[per thousand]; mean 6.5[per thousand]) matches that of massive sulphide ore (δ ³⁴S = -0.5 to 6.7[per thousand]; mean 5.8[per thousand]), in keeping with the supergenic origin of the sulphate and related isotope effects in the sulphide oxidation process. Sulphate in mine waters at Vigonzano displays lower δ ³⁴S values in the range 0.6 to 1.5[per thousand]. The δ ³⁴S signature of massive ore specimens is within the range reported for most volcanic-hosted massive sulphide deposits, including Cyprus-type deposits.

Agrichemical spills and discharges to soil can cause point-source contamination of surface and ground waters. When high contaminant concentrations inhibit natural attenuation in soils, chemical treatments can be used to promote degradation and allow application of treated soils to agricultural lands. This approach was used to remediate soil containing >650 mg atrazine, >170 mg metolachlor and >18,000 mg nitrate kg⁻¹. Results indicated a decrease in metolachlor concentration to <1 mg kg⁻¹ within 95 days of chemical treatment with zerovalent iron (Fe⁰, 5% w/w) and aluminum sulfate (Al₂(SO₄)₃, 2% w/w) but after one year >150 mg atrazine and >7000 mg nitrate kg⁻¹ remained. Laboratory experiments confirmed that subsequent additions of sucrose (table sugar) to the chemically pretreated soil promoted further reductions in atrazine and nitrate concentrations. Field-scale results showed that adding 5% (w/w) sucrose to windrowed and pretreated soil significantly reduced atrazine (<38 mg kg⁻¹) and nitrate (<2,100 mg kg⁻¹) concentrations and allowed for land application of the treated soil. These results provide evidence that zerovalent iron in combination with Al₂(SO₄)₃ and sucrose can be used for on-site, field-scale treatment of pesticide- and nitrate-contaminated soil.

In 1997, total petroleum hydrocarbon (TPH) remediation started at a former Air Force Base, which operated from 1940 to 1991. TPH had been released to soil and groundwater at the site by military activities. The TPH was 70% jet fuel and the affected area covered 28 ha. Remediation involved a combination of technologies, including removal of volatile organic compounds using soil vapor extraction and air sparging, free product vacuum recovery and aerobic biodegradation of organics with oxygen supplied by the air sparging system, along with nutrient addition. The primary remedial method was found to be biodegradation, which has removed 93% of the contaminants from the site to date. A significant aspect of the remedial action was performance monitoring, including documentation of remediation efficiency. The goal of the research was to assess the relative accuracy of methods commonly used for monitoring in situ TPH remediation. Two such methods were selected for the research: monitoring change in soil TPH concentration (specified as non-polar extractable substances) and monitoring respiration activity in soil with a subsequent stoichiometric mass balance to estimate the mass of TPH destroyed. The study demonstrated that both of the methods provided comparable results regarding the effectiveness of in situ TPH remediation, despite the fact that their methodologies are very different.

The distribution of nonylphenol ethoxylates (NPEOn) and their derivatives of nonylphenol (NP) and nonylphenoxy ethoxy acetic acids (NPEnC) in the sediments of a relatively closed freshwater reservoir was investigated using sediment layers sliced from undisturbed sediment cores collected with a gravity core sampler at three sampling sites (St. 1, St. 2 and St. 3) along the water flow direction. The relationships between the bound content of these compounds and the sediment organic matter as well as the likely transformation pathways were evaluated. The total content of NPEOn (n = 1-15) fell in 84.6-336.5, 59.9-135.5 and 77.0-623.4 μg/kg-dry for all sliced layers at St.1, St.2 and St.3, respectively, with the content of individual NPEOn species showing a general decreasing trend with the attached molar number of the ethoxy (EO) chain. Compared to each detected NPEOn species, the bound content of NP was much higher, falling in 73.2-248.4, 79.9-358.2 and 25.5-1,988.4 μg/kg-dry at St. 1, St. 2 and St. 3, respectively. A general increasing trend of the NP content along the water flow direction of the reservoir was revealed. NPEnC (n = 1-10) varied in 1.93-4.12, 2.85-9.84 and 1.05-19.1 μg/kg-dry for sediment at the respective site of St. 1, St. 2 and St. 3, with the averaged values at these sites (2.91, 4.71 and 6.72 μg/kg-dry) showing an increasing trend from the upstream to the downstream. For NPEnC, a parametric trend of increases in the content of NPE₁C, NPE₂C and NPE₃C with the bound sediment organic matter (9.06-11.8%) seemed to be existent. Furthermore, the computed magnitudes of NPEO₁-₂/NPEO₁-₁₅, NP/NPEO₁-₁₅ and NPEC₁-₁₀/NPEO₁-₁₅ suggested that non-oxidative hydrolytic transformation was probably prevailing within the sedimented mud phase of the reservoir, with the oxidative hydrolytic transformation pathway being less involved.

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.