Here we evaluate the performance and limitations of two frequently used model-types to predict trace element solubility in soils: regression based “partition-relations” and thermodynamically based “multisurface models”, for a large set of elements. For this purpose partition-relations were derived for As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, Se, V, Zn. The multi-surface model included aqueous speciation, mineral equilibria, sorption to organic matter, Fe/Al-(hydr)oxides and clay. Both approaches were evaluated by their application to independent data for a wide variety of conditions. We conclude that Freundlich-based partition-relations are robust predictors for most cations and can be used for independent soils, but within the environmental conditions of the data used for their derivation. The multisurface model is shown to be able to successfully predict solution concentrations over a wide range of conditions. Predicted trends for oxy-anions agree well for both approaches but with larger (random) deviations than for cations.

As the eutrophication of lakes becomes an increasingly widespread phenomenon, cyanobacterial blooms are occurring in many countries. Although some research has been reported, there is currently no good method for bloom removal. We propose here a new two-step integrated approach to resolve this problem. The first step is the inactivation of the cyanobacteria via the addition of H₂O₂. We found 60 mg/L was the lowest effective dose for a cyanobacterial concentration corresponding to 100 μg/L chlorophyll-a. The second step is the flocculation and sedimentation of the inactivated cyanobacteria. We found the addition of lake sediment clay (2 g/L) plus polymeric ferric sulfate (20 mg/L) effectively deposited them on the lake bottom. Since algaecides and flocculants had been used separately in previous reports, we innovatively combined these two types of reagents to remove blooms from the lake surface and to improve the dissolved oxygen content of lake sediments.

Polycyclic Aromatic Hydrocarbons (PAHs) transported by surface runoff result in nonpoint source pollution and jeopardize aquatic ecosystems. The transport mechanism of PAHs during rainfall-runoff events has been rarely studied regarding pervious areas. An experimental system was setup to simulate the runoff pollution process on PAHs-contaminated soil. The enrichment behavior of soil-bound PAHs was investigated. The results show that soil organic matters (SOM), rather than clay particles, seem to be the main carrier of PAHs. The enrichment is highly conditioned on runoff and erosion processes, and its magnitude varies among PAH compounds. It is not feasible to build a simple and universal relationship between enrichment ratio and sediment discharge following the traditional enrichment theory. To estimate the flux of PAHs from pervious areas, soil erosion process has to be clearly understood, and both organic carbon content and composition of SOM should be factored into the calculation.

The objective of the study reported in this paper was to assess the quality of harvested rainwater on the basis of the roofing materials used and the presence of lichens/mosses on the roofing surface. Four pilot structures with different roofing materials (i.e., wooden shingle tiles, concrete tiles, clay tiles [Gi-Wa] and galvanized steel) were installed in a field. The galvanized steel was found to be the most suitable for rainwater harvesting applications, with their resulting physical and chemical water quality parameters meeting the Korean guidelines for drinking water quality (e.g., pH (5.8–8.5), TSS <500 mg/L, NO₃ ⁻ < 10 mg/L, SO₄ ²⁻ < 200 mg/L, Al < 0.2 mg/L, Cu < 1 mg/L, Fe < 0.3 mg/L, Pb < 0.05 mg/L, Zn < 1 mg/L, and E. coli (No detection)). In the galvanized steel case, the relatively high water quality was probably due to ultraviolet light and the high temperature effectively disinfecting the harvested rainwater. It was also found that the presence of lichens and mosses may adversely affect the physical, chemical and microbiological quality of rainwater.

Knowledge of the partitioning and sources of mercury are important to understanding the human impact on mercury levels in Lake Superior wildlife. Fluvial fluxes of total mercury (HgT) and methylmercury (MeHg) were compared to discharge and partitioning trends in 20 sub-basins having contrasting land uses and geological substrates. The annual tributary yield was correlated with watershed characteristics and scaled up to estimate the basin-wide loading. Tributaries with clay sediments and agricultural land use had the largest daily yields with maxima observed near the peak in water discharge. Roughly 42% of HgT and 57% of MeHg was delivered in the colloidal phase. Tributary inputs, which are confined to near-shore zones of the lake, may be more important to the food-web than atmospheric sources. The annual basin-wide loading from tributaries was estimated to be 277 kg yr⁻¹ HgT and 3.4 kg yr⁻¹ MeHg (5.5 and 0.07 mg km⁻² d⁻¹, respectively).

The extreme 2010–2011 wet season resulted in highly elevated Burdekin River discharge into the Great Barrier Reef lagoon for a period of 200days, resulting in a large flood plume extending >50km offshore and >100km north during peak conditions. Export of suspended sediment was dominated by clay and fine silt fractions and most sediment initially settled within ∼10km of the river mouth. Biologically-mediated flocculation of these particles enhanced deposition in the initial low salinity zone. Fine silt and clay particles and nutrients remaining in suspension, were carried as far as 100km northward from the mouth, binding with planktonic and transparent exopolymer particulate matter to form large floc aggregates (muddy marine snow). These aggregates, due to their sticky nature, likely pose a risk to benthic organisms e.g. coral and seagrass through smothering, and also by contributing to increased turbidity during wind-induced resuspension events.

Conventional clay capping for post-closure management of landfill commonly cracks and deteriorates over time. As a consequence, water ingress into waste increases as a function of time, potentially causing a range of environmental issues. An alternative approach is known as phytocapping, which utilizes select plant species to control cap stability and moisture percolation. In this study, growth of Arundo donax L. (giant reed), Brassica juncea (L.) Czern. (Indian mustard), and Helianthus annuus L. (sunflower) on a landfill site was studied with different biosolid amendment rates (0, 25, and 50 Mg ha−1). Cultivation of the landfill cap and amendment with biosolids significantly improved the characteristics of the soil. Growth of each plant species increased due to biosolid addition. Giant reed produced the largest biomass in the 50 Mg ha−1 biosolid amendment rate (38 Mg ha−1 dry weight). The high pH and clay content of landfill cap soil, and the low metal concentrations of the biosolid resulted in low heavy metal (copper, zinc, cadmium, and lead) accumulation in leaves of most treatments. The improvement in growth and limited uptake of metal contaminants to plant shoots indicated that biosolid application to landfill clay caps improves the application of phytocapping of old landfill sites.

The validity of the soil quality standard for copper (Cu) established by the Spanish legislation (Spanish Royal Decree 9/2005) is evaluated in representative agricultural Mediterranean soils under an accumulator crop (Lactuca sativa L. var. Romaine cv. Long Green), considering both the effect of the metal on crop growth (biomass production) and its accumulation in the edible part of the plant. For saline soils, such a soil quality standard seems not to be valid taking into account both of the aspects evaluated. For non-saline soils, the soil quality standard also seems not to be valid since, considering the metal accumulation in the edible part of the plant, the soil quality standard should be above such standard; but considering the productivity function of soil (biomass production), the standard should be much below, meaning that this function is being greatly affected by the presence of high concentrations of Cu. The soil quality standard for each soil considered should correspond to a value between its respective EC50 and EC10 values (effective concentrations of added Cu causing 50% and 10% inhibition on the biomass production), depending on the politicians and/or farmers' compromise with yield production and, therefore, with soil productivity. These threshold values were greater for the soil having more organic matter and clay content, showing that Cu toxicity also depends on these properties. Further research in other agricultural areas of the region would improve the basis for proposing adequate soil quality standards as highlighted by the European Thematic Strategy for Soil Protection.

The high hydrophobicity of polycyclic aromatic hydrocarbons (PAHs) is the main limiting factor for the remediation of soils and aquifers. Surfactants are amphiphilic substances which encourage the transfer of hydrophobic compounds from the solid to the liquid phase. While the interaction between organic matter and surfactants has been widely studied, there is a lack of knowledge concerning the relationship between surfactant efficiency and the granulometry of soil and/or geologic material. In this paper, three non-ionic surfactants (Tween 80, Gold Crew, and BS-400) were used to study the desorption of pyrene, chosen as a representative PAH, in soils with different grain size proportions (1%, 5%, 10%, and 20% of clay and silt) and no organic matter (<0.1%). The best quantity of surfactant to apply is closely related to the proportion of fine materials. Tween 80 gave better maximum desorption than Gold Crew and BS-400 (89%, 40%, and 36%, respectively). As an important proportion of aquifers show fine material above 1%, the effective critical micellar concentration obtained when applying surfactants to this type of geologic materials has to be higher than 150 mg L−1 for Tween 80, and higher than 65 mg L−1, and 100 mg L−1 for Golf Crew and BS 400, respectively. Furthermore, results indicate that carrying out simple laboratory tests before the use of surfactants on a field scale is necessary to improve the efficiency and minimize the financial and environmental impact of its application.

Explosive compounds, including known toxicants 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), are loaded to soils during military training. Their fate in soils is ultimately controlled by soil mineralogical and biogeochemical processes. We detonated pure mineral phases with Composition B, a mixture of TNT and RDX, and investigated the fate of detonation residues in aqueous slurries constructed from the detonated minerals. The pure minerals included Ottawa sand (quartz and calcite), microcline feldspar, phlogopite mica, muscovite mica, vermiculite clay, beidellite (a representative of the smectite clay group), and nontronite clay. Energy-dispersive X-ray spectrometry, X-ray diffraction, and gas adsorption surface area measurements were made of the pristine and detonated minerals. Batch slurries of detonated minerals and deionized water were sampled for 141 days and TNT, RDX, and TNT transformation products were measured from the aqueous samples and from the mineral substrates at day 141. Detonated samples generally exhibited lower gas adsorption surface areas than pristine ones, likely from residue coating, shock-induced compaction, sintering, and/or partial fusion. TNT and RDX exhibited analyte loss in almost all batch solutions over time but loss was greater in vermiculite, beidellite, and phlogopite than in muscovite and quartz. This suggests common phyllosilicate mineral substrates could be used on military training ranges to minimize off-site migration of explosive residues. We present a conceptual model to represent the physical and chemical processes that occurred in our aqueous batches over time.