To protect forest cultures against browsing, chemical repellents can be used. With their applications, however, a problem arises with disruption of biological and chemical equilibria in the environment (e.g., soil-plant system). The aim of this study were to assess possible interactions of repellents, denatonium benzoate (DB), and capsaicin (Cps), with the soil matrix, especially the impact of their addition on the mobility of individual micronutrients and macronutrients, such as calcium, copper, iron, magnesium, manganese, phosphorus, sulfur, and zinc, and to verify the hypothesis that the presence of repellent compounds does not affect the plant-available nutrient concentrations in soil. Batch laboratory soil sorption experiment and the “diffusive gradient in thin films” (DGT) technique were applied to evaluate the elements’ mobility in the soils. Sorption experiment using Chernozem and Fluvisol showed decreased mobile forms of Cu and S with the additions of both repellents and conversely increased mobile forms of Ca and Mn for DB, in both soil types. With increasing Cps rates, the mobile forms of Fe in Chernozem decreased and Mn in Fluvisol increased. The DGT experiment confirmed increased mobile/available Mn in both soils for both repellents and Fe in Fluvisol in the case of capsaicin. Soil application of both, DB and Cps, suggested to be able to influence the elements’ mobility, particularly, Mn mobility in soil significantly increased after repellent application. Their possible behavior in rhizosphere soil/soil solution should be investigated in further research.

Thallium is a non-essential, toxic element that concerns mining areas and their acid drainage effluents. Minerals containing thallium can be eroded, and Tl can be leached into soil, thus being spread into the environment and adsorbed by plants and living organisms, entering the food chain, and inducing serious toxicity problems. In this study, the Tl cycle was observed and analyzed on basil, mint, and strawberry cultivated in a greenhouse and irrigated with Tl-contaminated water. The Tl content in both bulk and rhizosphere soils as well as thallium present in different plant organs were analyzed during the experiment, with the aim of revealing both physiological symptoms and metabolic disorders linked to the Tl toxicity. The mechanism of plants to exclude, uptake, translocate, and tolerate Tl varied among the different species, and both the bioconcentration factor (BCF) and the translocation index (TI) were calculated to highlight a different response to Tl toxicity of strawberry, mint, and basil. Basil is the less tolerant species, while mint and strawberry showed different self-defense mechanism against Tl adsorption and translocation.

Changes in soil exchangeable cations relative to soil acidification are less studied particularly under long-term cash crop plantation. This study investigated soil acidification in an Ali-Periudic Argosols after 10-year (2002–2012) long-term continuous tobacco plantation. Soils were respectively sampled at 1933 and 2143 sites in 2002 and 2012 (also 647 tobacco plants), from seven tobacco plantation counties in the Chongqing Municipal City, southwest China. After 10-year continuous tobacco plantation, a substantial acidification was evidenced by an average decrease of 0.20 soil pH unit with a substantial increase of soil sites toward the acidic status, especially those pH ranging from 4.5 to 5.5, whereas 1.93 kmol H⁺ production ha⁻¹ year⁻¹ was mostly derived from nitrogen (N) fertilizer input and plant N uptake output. After 1 decade, an average decrease of 27.6 % total exchangeable base cations or of 0.20 pH unit occurred in all seven tobacco plantation counties. Meanwhile, for one unit pH decrease, 40.3 and 28.3 mmol base cations kg⁻¹ soil were consumed in 2002 and 2012, respectively. Furthermore, the aboveground tobacco biomass harvest removed 339.23 kg base cations ha⁻¹ year⁻¹ from soil, which was 7.57 times higher than the anions removal, leading to a 12.52 kmol H⁺ production ha⁻¹ year⁻¹ as the main reason inducing soil acidification. Overall, our results showed that long-term tobacco plantation not only stimulated soil acidification but also decreased soil acid-buffering capacity, resulting in negative effects on sustainable soil uses. On the other hand, our results addressed the importance of a continuous monitoring of soil pH changes in tobacco plantation sites, which would enhance our understanding of soil fertility of health in this region.

Research and routine analysis laboratories produce sizeable amounts of residues as a result of experiments and by-products of chemical reactions. An example of that is soil analysis, in which a sulfochromic solution is used for the determination of organic matter content. This solution contains sodium dichromate and sulfuric acid, reagents that oxidize the soil’s organic fractions and contribute to the presence of chromium in laboratory residues discharged into the environment. In an attempt to find solutions to environmental problems, the aim of the present study was to quantitatively and qualitatively characterize chromium-contaminated residues generated during soil analysis. Therefore, management methods were proposed in order to recover chromium in its trivalent form (Cr³⁺) by precipitation. The use of biochemical oxygen demand, chemical oxygen demand, nitrogen, phosphorus, and metals to characterize the samples revealed the presence of 16.76 g L⁻¹ of total chromium, with 4.19 g L⁻¹ of Cr(VI). By means of ozonation, 68 % of the chromium was converted to liquid form and, after being reduced with bisulfite, it was turned into chromium sulfate (III). The remainder, 32 %, was kept with the other metals present in the solid form (sludge).

The effectiveness of gemini-modified palygorskite (PGS) as the novel remediation material in polycyclic aromatic hydrocarbons (PAHs)-contaminated water remediation was revealed and examined. The sorption behavior of gemini surfactants at the PGS/aqueous interface was addressed using a developed two-step adsorption and partition model (TAPM). The characterizations of gemini-modified PGS were investigated using infrared spectroscopy, cationic exchange capacity, and surface area analysis. The effects of pH, ionic strength, humic acid, and temperature on sorption of phenanthrene (PHE) to untreated and modified PGS were systematically studied. Analysis of the equilibrium data indicated that the sorption isotherms of gemini fitted TAPM well. The modification of PGS with gemini surfactants provided a favorable partition medium for PHE and enhanced PHE retention in solid particles. The solution parameters played significant effects on PHE sorption to the modified PGS. The sorption isotherms of PHE on PGS at different temperatures well fitted the Freundlich equation. Thermodynamic calculations confirmed that the sorption process of PHE on modified PGS was spontaneous and exothermic from 293 to 303 K. It is revealed that the modification with gemini surfactants probably offered some unique surface characteristics to the clay mineral as a new type of remediation material. This can provide a reference to the potential application of PGS in PAH-contaminated water remediation process.

Poderosa Mine is an abandoned pyrite mine, located in the Iberian Pyrite Belt which pours its acid mine drainage (AMD) waters into the Odiel river (South-West Spain). This work focuses on establishing possible reasons for interdependence between the potential redox and pH, with the load of metals and sulfates, as well as a set of variables that define the physical chemistry of the water—conductivity, temperature, TDS, and dissolved oxygen—transported by a channel from Poderosa mine affected by acid mine drainage, through the use of techniques of artificial intelligence: fuzzy logic and data mining. The sampling campaign was carried out in May of 2012. There were a total of 16 sites, the first inside the tunnel and the last at the mouth of the river Odiel, with a distance of approximately 10 m between each pair of measuring stations. While the tools of classical statistics, which are widely used in this context, prove useful for defining proximity ratios between variables based on Pearson’s correlations, in addition to making it easier to handle large volumes of data and producing easier-to-understand graphs, the use of fuzzy logic tools and data mining results in better definition of the variations produced by external stimuli on the set of variables. This tool is adaptable and can be extrapolated to any system polluted by acid mine drainage using simple, intuitive reasoning.

A biogeochemical investigation was carried out on Origanum majorana grown on limestone substrate in Greece. Possible health risks from consumption of dried herbs and infusions were assessed. Macronutrients and essential and toxic metals were determined in the leaves of O. majorana plants and in their soil substrates. Toxic metals were measured in the herbal infusions. Macroelements were found generally in low concentrations for normally developing plants, except for Ca. The ratios N/P and N/K were found lower than the optimum range for normal growth, while the values of K/(Ca + Mg) ratio prevent the development of grass tetany. Manganese and arsenic were enriched in distinct samples. O. majorana plants can be used as indicators for soil environmental assessment. They can also be applied in phytoremediation methods in metal-polluted soils. Hazard indices were far below 1. Carcinogenic risks were found to be within the acceptable range. No health risk is anticipated by the consumption of the specific plants investigated in the present study.

In order to enhance the oxidation and adsorption capacity of catalyst, two kinds of activated carbon (AC) are mechanically mixed with V₂O₅-WO₃/TiO₂ catalyst respectively. In this study, the mixtures (M-1: catalyst mixing with AC based on lignite; M-2: the one on coconut shell) are investigated to destroy high concentration (9.8 ng I-TEQ Nm⁻³) PCDD/Fs at low temperature (160 °C). Adding AC into the catalyst obviously increases removal efficiency (RE) and destruction efficiency (DE). However, M-2 presents higher RE value and lower DE value compared with M-1 at the same conditions as the stronger adsorption capacity of AC based on coconut shell. For the M-2 mixture, RE values are decreasing while DE values show an opposite trend with the ratios of catalyst to AC increasing. Oxygen plays a positive role on the destruction of PCDD/Fs by accelerating the conversion of V⁴⁺Oₓ and V⁵⁺Oₓ. Adjusting oxygen content from 0 to 20 % could increase the DE value from 27.4 to 82.2 % for the M-1 and from 15.8 to 68.9 % for the M-2. In the presence of ozone, a dark brown flock will be generated when the ratio of AC and catalyst is 4:1 due to the reaction between AC and ozone, which results in the lower RE and DE values. The RE and DE values reach the maximum of 96.3 %, 90.6 % in this paper, respectively, when the ratio of AC and catalyst is 1:1 with ozone. Finally, the regenerating of mixture is investigated. Most of dioxin residues in the mixture are desorbed and oxidized by catalysis at 200 °C in the presence of oxygen.

The study of fluvial bed sediments is essential for deciphering the impact of anthropogenic activities on water quality and drainage basin integrity. In this study, a systematic sampling design was employed to characterize the spatial variation of lead (Pb) concentrations in bed sediment of urban streams in the Palolo drainage basin, southeastern Oahu, Hawaii. Potentially bioavailable Pb was assessed with a dilute 0.5 N HCl extraction of the <63 μm grain-size fraction from the upper bed sediment layer of 169 samples from Palolo, Pukele, and Waiomao streams. Contamination of bed sediments was associated with the direct transport of legacy Pb from the leaded gasoline era to stream channels via a dense network of storm drains linked to road surfaces throughout the basin. The Palolo Stream had the highest median Pb concentration (134 mg/kg), and the greatest road and storm drain densities, the greatest population, and the most vehicle numbers. Lower median Pb concentrations were associated with the less impacted Pukele Stream (24 mg/kg), and Waiomao Stream (7 mg/kg). The median Pb enrichment ratio values followed the sequence of Palolo (68) > Pukele (19) > Waiomao (8). Comparisons to sediment quality guidelines and potential toxicity estimates using a logistic regression model (LRM) indicated a significant potential risk of Palolo Stream bed sediments to bottom-dwelling organisms.

Nitrogen pollution in ground and surface water significantly affects the environment and its organisms, thereby leading to an increasingly serious environmental problem. Such pollution is difficult to degrade because of the lack of carbon sources. Therefore, an electrochemical and biological coupling process (EBCP) was developed with a composite catalytic biological carrier (CCBC) and applied in a pilot-scale cylindrical reactor to treat wastewater with a carbon-to-nitrogen (C/N) ratio of 2. The startup process, coupling principle, and dynamic feature of the EBCP were examined along with the effects of hydraulic retention time (HRT), dissolved oxygen (DO), and initial pH on nitrogen removal. A stable coupling system was obtained after 51 days when plenty of biofilms were cultivated on the CCBC without inoculation sludge. Autotrophic denitrification, with [Fe²⁺] and [H] produced by iron–carbon galvanic cells in CCBC as electron donors, was confirmed by equity calculation of CODCᵣ and nitrogen removal. Nitrogen removal efficiency was significantly influenced by HRT, DO, and initial pH with optimal values of 3.5 h, 3.5 ± 0.1 mg L⁻¹, and 7.5 ± 0.1, respectively. The ammonia, nitrate, and total nitrogen (TN) removal efficiencies of 90.1 to 95.3 %, 90.5 to 99.0 %, and 90.3 to 96.5 % were maintained with corresponding initial concentrations of 40 ± 2 mg L⁻¹ (NH₃–N load of 0.27 ± 0.01 kg NH₃–N m⁻³ d⁻¹), 20 ± 1 mg L⁻¹, and 60 ± 2 mg L⁻¹ (TN load of 0.41 ± 0.02 kg TN m⁻³ d⁻¹). Based on the Eckenfelder model, the kinetics equation of the nitrogen transformation along the reactor was N ₑ = N ₀ exp (−0.04368 h/L¹.⁸⁴³⁸). Hence, EBCP is a viable method for advanced low C/N ratio wastewater treatment.