A new sediment P release risk index (SPRRI) for “in-situ” phosphorus (P) release risk in lake sediment, is developed based on diffusive gradients in thin films (DGT) technique, DGT induced flux in sediments (DIFS) model and sediment properties. SPRRI includes three sub-indexes, which contain (1) the labile P pool size, (2) resupply constant (r) and desorption rate (Dspt rate) for P transfer and (3) the molar ratio between iron (Fe) in sequential extraction for sediment P by bicarbonate-dithionite (BD) and aluminum (Al) by NaOH (at 25 °C), i.e. BD(Fe)/Al[NaOH25] in sediment solid. The first sub-index considers P release from (i) sediment with NH₄Cl-P+BD-P pool, i.e. the loosely sorbed P (NH₄Cl-P) plus iron associated P (BD-P), or (ii) sediment with NH₄Cl-P pool, respectively. The second and third sub-indexes reflect kinetic P desorption and resupply ability of solid phase, and the effect of P sequestration by Al hydroxide on P release, in turn. The inner relationship between SPRRI and sub-indexes, and their effects on P release risk are elucidated. SPRRI can be used to evaluate sediment P reactivity by five release risk ranks. For Lake Dianchi (China), P transfer dynamics, labile P pool, resupply ability and Al-P in sediment, and “external P-loading” control and affect P release risk in different regions, which is reflected by the spatial distribution map for SPRRI. The present SPRRI can be applied for lakes with (1) pH range varying from moderate acidity to weak alkalinity in waterbody and (2) NH₄Cl-P or NH₄Cl-P+BD-P pool in sediment solid.

The binding of metal ions with humic acid (HA) plays an important role in the aggregation of HA and the migration of metal ions in the environments. The effects of common cations (Na⁺, Mg²⁺, Ca²⁺ and Al³⁺) and heavy metal ions (Ag⁺, Cd²⁺, Cu²⁺, Cr³⁺ and Eu³⁺) on the aggregation of HA were investigated systematically by aggregation kinetics, spectroscopic techniques and molecular dynamic (MD) simulations. The critical coagulation concentration (CCC) of mono-, di- and trivalent cations could be predicted by the Schulze-Hardy rule. The aggregation of HA in the presence of Na⁺ and Ag⁺ was mainly due to the reduction of repulsive force and the hydrogen bonds between HA molecules. While the complexation of di- and trivalent cations with carboxylic/phenolic groups, or the cation-π interactions enhanced the intra- or inter-molecular bridges in HA and then contributed greatly to the aggregation of HA. Heavy metal ions could easily pass through the electric double-layer of HA compared with common cations. MD simulations further signified the strong aggregation ability of HA molecules in solutions containing high valence metal ions. These findings are important for understanding not only how the influence of metal ions on the aggregation of HA, but also the conditions which ions more efficient for aggregation.

Metals are released from biochar (BC) in either the free or dissolved organic carbon (DOC)-combined form. The complexation of metals with DOC influences their toxicity and bioavailability in the environment. The endogenous release of metal species with heterogeneous DOC from BC is very complex; this process has been neglected and remains unaddressed in the literature to date. In this study, the yield and chemical properties of labile DOC from BC were characterized, and the release of endogenous metal/metalloid elements (K, Mg, Mn, Fe, Al, Cu, and Si) and their species from BC with various pyrolysis temperatures and particle sizes were systematically investigated under various solution chemistries. The results showed that pyrolysis temperature of BC significantly influenced the yield and composition of DOC and DOC-metal/metalloid complexes, while particle size had lower impact. The yield of BC-derived DOC significantly decreased and the components gradually changed from low-molecular weight and low-aromaticity hydrophilic humic acid-like substances to complex high-molecular weight and high-aromaticity hydrophobic substances as pyrolysis temperature increased from 200 to 700 °C. The release of total dissolved metals decreased with increasing pyrolysis temperature, while the highest total dissolved Si was released from BC with the moderate pyrolysis temperature (500 °C). The metal elements were mainly released in the DOC-combined form, while the released Si was mainly in the free form in the neutral water environment. The release of DOC increased while that of dissolved metals decreased with increasing solution pH. The release of total dissolved metals/metalloids increased but the ratio of the DOC-combined metals/metalloids decreased with increasing solution ionic strength. These results provide new insight into the understanding of endogenous metal/metalloid release from BC in the natural environment.

Agricultural soil is one of the main sink for both heavy metals and nanomaterials (NMs). Whether NMs can impact heavy metals uptake or bioaccumulation in plants is unknown. Here, cucumber plants were cultivated in a multi-heavy metals contaminated soil amended with four types of NMs (SiO2, TiO2, ZnS and MoS2) separately for four weeks. Physiological and biochemical parameters were determined to investigate the impact of NMs on plant growth. Inductively coupled plasma mass spectrometry was employed to determine the metal content in plants. Results showed that none of the tested NMs impacted plants biomass, but all the NMs showed different degrees of reduction in heavy metals bioaccumulation in plant roots, stems and leaves. However, four NMs showed different degrees of reduction in macro and micro nutrients uptake. MoS2 decreased the bioaccumulation of heavy metals (As, Cd, Cr, Cu, Ni, Al, Ti and Pb) for 36.4–60.6% and nutrients (Mg, Fe, K, Si and Mn) for 40.1%–50.1% in roots. Exposure to MoS2 NMs also significantly increased 23.4% of Si in leaves, 205.6% and 83.9% of Mo in roots and stems, respectively. In general, the results of this study showed promising potential for NMs to reduce uptake of heavy metals in crop plants, especially MoS2 NMs. However, the negative impacts of perturbing nutrients uptake should be paid attention as well.

Aluminum dialkyl phosphinates (ADPs) are a promising class of chemicals offering superior flame retardance. However, knowledge on their behavior in vivo is scarce. Hydrolysis has been suggested as one of the major routes of environmental degradation of ADPs. Herein, aluminum methylcyclohexyl phosphinic (AMHP), a kind of ADPs with industrial production in China, and its hydrolysate methyl cyclohexyl phosphinic acid (MHPA) were continuously exposed to Sprague Dawley (SD) rats for 28 days in this study. The same ratio of MHPA in organs to serum and the same daily excretion of MHPA were observed for AMHP exposure group and MHPA exposure group, suggesting the hydrolysis of AMHP in vivo. The hydrolysis of AMHP to MHPA was further confirmed by in vitro simulated human gastric intestinal juice. Therefore, both AMHP and MHPA distributed in liver, kidney and even brain in the form of MHPA. More than 80% of AMHP and MHPA could be excreted by feces and urine. Feces are the main route of excretion of AMHP and MHPA. The denseness of the inflammatory cell in the hepatic portal area and biochemical indexes showed the obvious dose-effect relationship. However, the toxicity of AMHP and MHPA was quite low even with exposure level up to 100 mg/kg dw/day. The low cumulative ability and mild toxicity indicated AMHP as a promising substitute for brominated flame retardant.

The reactivity characteristics of humic acid (HA) with aluminium coagulants at different pH values was investigated. It revealed that the linear complexation reaction occurred between aluminum and humic acid at pH < 7, and the reaction rate increased as the pH increased from 2 to 6. While at pH = 7, most of the dosed aluminum existed in the form of free aluminum and remained unreacted in the presence of HA until the concentration reached to trigger Al(OH)₃₍ₛ₎ formation. Differentiating the change of functional groups of HA by ¹H nuclear magnetic resonance spectroscopy and X-ray photoelectron spectra analysis, it elucidated that there was a selective complexation between HA and Al with lower Al dosage at pH 5, which was probably due to coordination of the activated functional groups onto aluminium. While almost all components were removed proportionally by sweep adsorption without selectivity at pH 7, as well as that with higher Al dosage at pH 5. This study provided a promising pathway to analyse the mechanism of the interaction between HA and metal coagulants in future.

Aluminum (Al) phytotoxicity is a major limitation in the production of crops in the soils with pH ≤ 5. Boron (B) is indispensable nutrient for the development of higher plants and B role has been reported in the alleviation Al toxicity. Trifoliate orange rootstock was grown in two B and two Al concentrations. The results of the present study showed that Al toxicity adversely inhibited root elongation and exhibited higher oxidative stress in terms of H2O2 and O2− under B-deficiency. Additionally, the X-ray diffraction (XRD) analysis confirmed the increase of the cellulose crystallinity in the cell wall (CW). Al-induced remarkable variations in the CW components were prominent in terms of alkali-soluble pectin, 2-keto-3-deoxyoctonic acid (KDO) and the degree of methyl-esterification (DME) of pectin. Interesting, B supply reduced the pectin (alkali-soluble) under Al toxicity. Moreover, the results of FTIR (Fourier transform infrared spectroscopy) and 13C-NMR (13C nuclear magnetic resonance) spectra revealed the decrease of carboxyl groups and cellulose by B application during Al exposure. Furthermore, B supply tended to decrease the Al uptake, CW thickness and callose formation. The study concluded that B could mitigate Al phytotoxicity by shielding potential Al binding sites and by reducing Al induced alterations in the CW cellulose and pectin components.

Ants accumulate heavy metals and respond to pollution with modification in species composition, community structure, altered behaviour and immunity. However, the levels of heavy metals in ants’ nests and explicit individual-level responses towards heavy metals have not been revealed. We found that red wood ants Formica lugubris accumulate high and correlated values of such heavy metals as Al, Cd, Co, Cu, Fe, Ni, Pb and Zn both in ants and nest material near cobalt smelter in Finland. Relative differences in metal concentrations were higher in nests than in ants. The highest values were obtained for elements such as Co (36.6), Zn (14.9), Cd (9.7), Pb (8.5), Cu (7.4), Ni (6.4), As (4.7), Cr (2.9) and Fe (2.4) in nest material, and Co (32.7), Cd (6.3), Pb (6), Fe (2.8), Ni (2.9) and Zn (2.1) in ants. In industrial and reference areas, ants have no differences in size, but differed in dry and residual body mass. In polluted areas, F. lugubris had less melanised heads, but not thoraxes. The sensitivity of cuticular colouration in red wood ants subjected to heavy metal pollution might be related to metal-binding properties of melanins. The overall results are useful for the improvement of biomonitoring techniques using ants as indicators of industrial contamination and for further discovery of novel ecotoxicological biomarkers.

Bogota registers frequent episodes of poor air quality from high PM₁₀ concentrations. It is one of the main Latin American megacities, located at 2600 m in the tropical Andes, but there is insufficient data on PM₁₀ source contribution. A characterization of the chemical composition and the source apportionment of PM₁₀ at an urban background site in Bogota was carried out in this study. Daily samples were collected from June 2015 to May 2016 (a total of 311 samples). Organic carbon (OC), elemental carbon (EC), water soluble compounds (SO₄²⁻, Cl⁻, NO₃⁻, NH₄⁺), major elements (Al, Fe, Mg, Ca, Na, K, P) and trace metals (V, Cd, Pb, Sr, Ba, among others) were analyzed. The results were interpreted in terms of their variability during the rainy season (RS) and the dry season (DS). The data obtained revealed that the carbonaceous fraction (∼51%) and mineral dust (23%) were the main PM₁₀ components, followed by others (15%), Secondary Inorganic Compounds (SIC) (11%) and sea salt (0.4%). The average concentrations of soil, SIC and OC were higher during RS than DS. However, peak values were observed during the DS due to photochemical activity and forest fires. Although trace metals represented <1% of PM₁₀, high concentrations of toxic elements such as Pb and Sb on RS, and Cu on DS, were obtained. By using a PMF model, six factors were identified (∼96% PM₁₀) including fugitive dust, road dust, metal processing, secondary PM, vehicles exhaust and industrial emissions. Traffic (exhaust emissions + road dust) was the major PM₁₀ source, accounting for ∼50% of the PM₁₀. The results provided novel data about PM₁₀ chemical composition, its sources and its seasonal variability during the year, which can help the local government to define control strategies for the main emission sources during the most critical periods.

Simultaneous aggregation and retention of nanoparticles can occur during their transport in porous media. In this work, the concurrent aggregation and transport of GO in saturated porous media were investigated under the conditions of different combinations of temperature, cation type (valence), and electrolyte concentration. Increasing temperature (6–24 °C) at a relatively high electrolyte concentration (i.e., 50 mM for Na⁺, 1 mM for Ca²⁺, 1.75 mM for Mg²⁺, and 0.03 and 0.05 mM for Al³⁺) resulted in enhanced GO retention in the porous media. For instance, when the temperature increased from 6 to 24 °C, GO recovery rate decreased from 31.08% to 6.53% for 0.03 mM Al³⁺ and from 27.11% to 0 for 0.05 mM Al³⁺. At the same temperature, increasing cation valence and electrolyte concentration also promoted GO retention. Although GO aggregation occurred in the electrolytes during the transport, the deposition mechanisms of GO retention in the media depended on cation type (valence). For 50 mM Na⁺, surface deposition via secondary minima was the dominant GO retention mechanism. For multivalent cation electrolytes, GO aggregation was rapid and thus other mechanisms such as physical straining and sedimentation also played important roles in controlling GO retention in the media. After passing through the columns, the GO particles in the effluents showed better stability with lower initial aggregation rates. This was probably because less stable GO particles with lower surface charge densities in the porewater were filtered by the porous media, resulting in more stable GO particle with higher surface charge densities in the effluents. An advection–dispersion-reaction model was applied to simulate GO breakthrough curves and the simulations matched all the experimental data well.