Mineral phosphorus (P) fertilizers contain contaminants that are potentially hazardous to humans and the environment. Frequent mineral P fertilizer applications can cause heavy metals to accumulate and reach undesirable concentrations in agricultural soils. There is particular concern about Cadmium (Cd) and Uranium (U) accumulation because these metals are toxic and can endanger soil fertility, leach into groundwater, and be taken up by crops. We determined total Cd and U concentrations in more than 400 topsoil and subsoil samples obtained from 216 agricultural sites across Switzerland. We also investigated temporal changes in Cd and U concentrations since 1985 in soil at six selected Swiss national soil monitoring network sites. The mean U concentrations were 16% higher in arable topsoil than in grassland topsoil. The Cd concentrations in arable and grassland soils did not differ, which we attribute to soil management practices and Cd sources other than mineral P fertilizers masking Cd inputs from mineral P fertilizers. The mean Cd and U concentrations were 58% and 9% higher, respectively, in arable topsoil than in arable subsoil, indicating that significant Cd and U inputs to arable soils occurred in the past. Geochemical mass balances confirmed this, indicating an accumulation of 52% for Cd and 6% for U. Only minor temporal changes were found in the Cd concentrations in topsoil from the six soil-monitoring sites, but U concentrations in topsoil from three sites had significantly increased since 1985. Sewage sludge and atmospheric deposition were previously important sources of Cd to agricultural soils, but today mineral P fertilizers are the dominant sources of Cd and U. Future Cd and U inputs to agricultural soils may be reduced by using optimized management practices, establishing U threshold values for mineral P fertilizers and soils, effectively enforcing threshold values, and developing and using clean recycled P fertilizers.

Predicting the transfer of contaminants in soils is often hampered by lacking validation of mathematical models. Here, we applied Hydrus-2D software to three agricultural soils for simulating the 1900–2005 changes of zinc and lead concentration profiles derived from industrial atmospheric deposition, to validate the tested models with plausible assumptions on past metal inputs to reach the 2005 situation. The models were set with data from previous studies on the geochemical background, estimated temporal metal deposition, and the 2005 metal distributions. Different hypotheses of chemical reactions of metals with the soil solution were examined: 100% equilibrium or partial equilibrium, parameterized following kinetic chemical extractions. Finally, a two-site model with kinetic constant values adjusted at 1% of EDTA extraction parameters satisfactory predicted changes in metal concentration profiles for two arable soils. For a grassland soil however, this model showed limited applicability by ignoring the role of earthworm activity in metal incorporation.

Detailed soil screening data from the Czech Republic as a typical Central European country are presented here. Determination of a wide selection of organic and inorganic pollutants as well as an assessment of specific soil parameters allowed us to study the soil contamination in relation to the land use and soil properties. While HCHs and HCB were found at highest levels in arable soils, the higher concentrations of PCDDs/Fs, PCBs, PAHs and DDTs were observed in high altitude forest soils. Concentrations of these compounds strongly correlated with the soil organic carbon content. Several possible reasons have been suggested for the observed higher concentrations in mountain forest soils but the impact of each of these influencing factors remains to be identified. An inventory of the soil contamination is needed as a first step in our effort to estimate an extent to which the secondary sources contribute to the enhanced atmospheric levels of POPs. Due to its large retention capacity for hydrophobic compounds, carbon-rich mountain soil showed higher concentrations for several persistent organic pollutants.

The physico-chemical absorption characteristics of ammonium-N for 10 soils from 5 profiles in York, UK, show its high potential mobility in N deposition-impacted, unfertilized, permanent grassland soils. Substantial proportions of ammonium-N inputs were retained in the solution phase, indicating that ammonium translocation plays an important role in the N cycling in, and losses from, such soils. This conclusion was further supported by measuring the ammonium-N leaching from intact plant/soil microcosms. The ammonium-N absorption characteristics apparently varied with soil pH, depth and soil texture. It was concluded for the most acid soils especially that ammonium-N leached from litter horizons could be seriously limiting the capacity of underlying soils to retain ammonium. Contrary to common opinion, more attention therefore needs to be paid to ammonium leaching and its potential role in biogeochemical N cycling in semi-natural soil systems subject to atmospheric pollution. mmonium mobility is more important than previously thought in N-impacted, unfertilized grasslands.

Legacy perfluoroalkyl and poly-fluoroalkyl substances (PFASs) are gradually phased out because of their persistence, bioaccumulation, toxicity, long-distance transport and ubiquity in the environment. Alternatively, emerging PFASs are manufactured and released into the environment. It is accepted that PFASs can impact microbiota, although it is still unclear whether emerging PFASs are toxic towards soil microbiota. However, it could be assumed that OBS could impact soil microorganisms because it had similar chemical properties (toxicity and persistence) as legacy PFASs. The present study aimed to explore the influences of an emerging PFAS, namely sodium p-perfluorous nonenoxybenzene sulfonate (OBS), on archaeal, bacterial, and ammonia-oxidizing archaea (AOA) and bacteria (AOB) communities and ammonia oxidation. Grassland soil was amended with OBS at different dosages (0, 1, 10 and 100 mg/kg). After OBS amendment, tolerant microorganisms (e.g., archaea and AOA) were promoted, while susceptive microorganisms (e.g., bacteria and AOB) were inhibited. OBS amendment greatly changed microbial structure. Potential nitrifying activity was inhibited by OBS in a dose-dependent manner during the whole incubation. Furthermore, AOB might play a more important role in ammonia oxidation than AOA. Overall, OBS influenced ammonia oxidation by regulating the activity, abundance and structure of ammonia-oxidizing microorganisms, and could also exert influences on total bacterial and archaeal populations.

Soils, especially permafrost in the Arctic and the Tibetan Plateau, are one of the largest reservoirs of mercury (Hg) in the global environment. The Hg concentration in the grassland soils over the Tibetan Plateau and its driving factors have been less studied. This study analyzes soil total mercury (STHg) concentrations and its vertical distribution in grassland soil samples collected from the Tibetan Plateau. We adopt a nested-grid high-resolution GEOS-Chem model to simulate atmospheric Hg deposition. The relationship between STHg and soil organic carbon (SOC), as well as atmospheric deposition, are explored. Our results show that the STHg concentrations in the Tibetan Plateau are 19.8 ± 12.2 ng/g. The concentrations are higher in the south and lower in the north in the Tibetan Plateau, consistent with the previous results. Our model shows that the average deposition flux of Hg is 3.3 μg m⁻² yr⁻¹, with 57% contributed by dry deposition of elemental mercury (Hg⁰), followed by dry (19%) and wet (24%) deposition of divalent mercury. We calculate the Hg to carbon ratio (RHg:C) as 5.6 ± 6.5 μg Hg/g C, and the estimated STHg is 86.6 ± 101.2 Gg in alpine grasslands in the Tibetan Plateau. We find a positive relationship between STHg and SOC in the Tibetan Plateau (r² = 0.36) and a similar positive relationship between STHg and atmospheric total Hg deposition (r² = 0.24). A multiple linear regression involving both variables better model the observed STHg (r² = 0.42). We conclude that SOC and atmospheric deposition influence STHg simultaneously in this region. The data provides information to quantify the size of the soil Hg pool in the Tibetan Plateau further, which has important implications for the Hg cycles in the permafrost regions as well as on the global scale.

Cigarette butts (CBs) are the most common litter item on Earth but no long-term studies evaluate their fate and ecological effects. Here, the role of nitrogen (N) availability and microbiome composition on CBs decomposition were investigated by a 5-years experiment carried out without soil, in park grassland and sand dune. During decomposition, CBs chemical changes was assessed by both ¹³C CPMAS NMR and LC-MS, physical structure by scanning electron microscope and ecotoxicity by Aliivibrio fischeri and Raphidocelis subcapitata. Microbiota was investigated by high-throughput sequencing of bacterial and eukaryotic rRNA gene markers. CBs followed a three-step decomposition process: at the early stage (∼30 days) CBs lost ∼15.2% of their mass. During the subsequent two years CBs decomposed very slowly, taking thereafter different trajectories depending on N availability and microbiome composition. Without soil CBs showed minor chemical and morphological changes. Over grassland soil a consistent N transfer occurs that, after de-acetylation, promote CBs transformation into an amorphous material rich in aliphatic compounds. In sand dune we found a rich fungal microbiota able to decompose CBs, even before the occurrence of de-acetylation. CBs ecotoxicity was highest immediately after smoking. However, for R. subcapitata toxicity remained high after two and five years of decomposition.

Dust emissions from copper smelters processing arsenic-bearing ores represent a risk to soil environments due to the high levels of As and other inorganic contaminants. Using an in situ experiment in four different forest and grassland soils (pH 3.2–8.0) we studied the transformation of As-rich (>50 wt% As) copper smelter dust over 24 months. Double polyamide bags with 1 g of flue dust were buried at different depths in soil pits and in 6-month intervals; then those bags, surrounding soil columns, and soil pore waters were collected and analysed. Dust dissolution was relatively fast during the first 6 months (5-34%), and mass losses attained 52% after 24 months. The key driving forces affecting dust dissolution were not only pH, but also the water percolation/retention in individual soils. Primary arsenolite (As2O3) dissolution was responsible for high As release from the dust (to 72%) and substantial increase of As in the soil (to a 56 × increase; to 1500 mg kg−1). Despite high arsenolite solubility, this phase persisted in the dust after 2 years of exposure. Mineralogical investigation indicated that mimetite [Pb5(AsO4)3(Cl,OH)], unidentified complex Ca-Pb-Fe-Zn arsenates, and Fe oxyhydroxides partly controlled the mobility of As and other metal(loid)s. Compared to As, other less abundant contaminants (Bi, Cu, Pb, Sb, Zn) were released into the soil to a lesser extent (8-40% of total). The relatively high mobility of As in the soil can be seen from decreases of bulk As concentrations after spring snowmelt, high water-extractable fractions with up to ∼50% of As(III) in extracts, and high As concentrations in soil pore waters. Results indicate that efficient controls of emissions from copper smelters and flue dust disposal sites are needed to prevent extensive contamination of nearby soils by persistent As.

In this study water balance components as well as nitrogen and dissolved organic carbon leaching were quantified by means of large weighable grassland lysimeters at three sites (860, 770 and 600 m a.s.l.) for both intensive and extensive management. Our results show that at E600, the site with highest air temperature (8.6 °C) and lowest precipitation (981.9 mm), evapotranspiration losses were 100.7 mm higher as at the site (E860) with lowest mean annual air temperature (6.5 °C) and highest precipitation (1359.3 mm). Seepage water formation was substantially lower at E600 (−440.9 mm) as compared to E860. Compared to climate, impacts of management on water balance components were negligible. However, intensive management significantly increased total nitrogen leaching rates across sites as compared to extensive management from 2.6 kg N ha−1 year−1 (range: 0.5–6.0 kg N ha−1 year−1) to 4.8 kg N ha−1 year−1 (range: 0.9–12.9 kg N ha−1 year−1). N leaching losses were dominated by nitrate (64.7%) and less by ammonium (14.6%) and DON (20.7%). The low rates of N leaching (0.8–6.9% of total applied N) suggest a highly efficient nitrogen uptake by plants as measured by plant total N content at harvest. Moreover, plant uptake was often exceeding slurry application rates, suggesting further supply of N due to soil organic matter decomposition. The low risk of nitrate losses via leaching and surface runoff of cut grassland on non-sandy soils with vigorous grass growth may call for a careful site and region specific re-evaluation of fixed limits of N fertilization rates as defined by e.g. the German Fertilizer Ordinance following requirements set by the European Water Framework and Nitrates Directive.

The deposition of high levels of reactive nitrogen (N) and sulphur (S), or the legacy of that deposition, remain among the world's most important environmental problems. Although regional impacts of acid deposition in aquatic ecosystems have been well documented, quantitative evidence of wide-scale impacts on terrestrial ecosystems is not common. In this study we analysed surface and subsoil chemistry of 68 acid grassland sites across the UK along a gradient of acid deposition, and statistically related the concentrations of exchangeable soil metals (1 M KCl extraction) to a range of potential drivers. The deposition of N, S or acid deposition was the primary correlate for 8 of 13 exchangeable metals measured in the topsoil and 5 of 14 exchangeable metals in the subsoil. In particular, exchangeable aluminium and lead both show increased levels above a soil pH threshold of about 4.5, strongly related to the deposition flux of acid compounds. S and N deposition contribute to regional-scale soil acidification and metal mobilisation.