Soil microbial communities play an important role in the biodegradation of different petroleum derivates, including hydrocarbons. Also other biological factors such as enzyme and respiration activities and microbial abundance are sensitive to contamination with petroleum derivates. The aim of this study was to evaluate the response of autochthonic microbial community and biological parameters (respiration, dehydrogenase and catalase activities, total microorganisms count) on contamination with car fuels and engine oils. The surface layer (0–20 cm) of Mollic Gleysol was used for the experiment. In laboratory conditions, soil was contaminated with the following petroleum substances: car fuels (petrol, diesel) and car engine oils (new and waste—after 10,000 km). The results demonstrated that, among the investigated hydrocarbon substances, petrol addition seemed to be the most toxic for the microbial activity of the investigated soil. The toxicity of the used hydrocarbon substances to microorganisms might be summarized as follows: diesel > new oil > waste oil > petrol. Species belonging to the genera Micrococcus and Rhodococcus were noted as the major autochthonic bacteria being present in soil contaminated with new automobile oil, whereas species of the genera Bacillus sp. and Paenibacillus sp. were identified in the combination treated with waste oil.

In Mexico, the mangrove is distributed in 764,486 ha, comprising the Atlantic coast from the Laguna Madre in Tamaulipas to Chetumal Bay in the Caribbean and in the Pacific from Ensenada, Baja California to Chiapas. On the coast of Oaxaca, coexist four species: red mangrove (Rhizophora mangle), white mangrove (Laguncularia racemosa) button mangrove (Conocarpus erectus) and black mangrove (Aviccenia germinans). In the Laguna “Salina” Tonameca, grows and develops the white, button, and black mangroves, whose spatial distribution decreases by deforestation, land use change, and increased saline substrate. Salinity of soil and waters, its concentration, and tipogenesis associated with the growth of mangrove trees were determined. Three saline gradients were identified in rainy season (gradient I: 2.18 dS m⁻¹; gradient II: 9.95 dS m⁻¹ and gradient III: 36.14 dS m⁻¹); while in drought season four gradients were detected (gradient I: 1.15 dS m⁻¹; II: 17.83 dS m⁻¹; III: 39.06 dS m⁻¹ and IV: 57.75 dS m⁻¹). The interannual saline variation is due to climatics, hydrologycal, and geomorpholigical conditions of the substrate. The lake salinity is hydrochloric, predominantly NaCl salt, of intense osmotic effect, which largely explains the mangrove halophytism. Moisture diluting brackish water, such that low salt conditions promotes growth and development of mangrove, but at concentrations > 35 g L⁻¹ limits their growth. In drought, hypersaline (>70 g L⁻¹) prevents the establishment and repopulation of this species.

In this study, a novel chemical-free approach for cleaning oil-contaminated sand with self-collapsing air microbubbles (MBs) with diameter less than 50 μm was developed without the use of chemicals, such as surfactants and alkalis. Diesel and rotary-vane pump oil-contaminated fine and medium sands were treated with MBs to study the effect of oil viscosity and sand grain size on oil removal with MBs. About 95 % of diesel removal was achieved for 24 h old 10 % (w/w) diesel-contaminated medium sand in contrast to only 70 % removal from fine sand after 40-min treatment with MBs. While rotary-vane pump oil removal exceeds that of diesel after 40-min treatment with MBs, combination of mechanical stirring with MBs significantly enhanced the oil removal rate, whereby 95 % diesel removal was achieved from fine sand in 30 min in contrast to only 52 % diesel removal with MBs alone. A possible MBs cleaning mechanism for oil-contaminated sand was also proposed. This study provides experimental evidence for the applicability of self-collapsing MBs as a novel chemical-free approach for cleaning oil-contaminated sand.

During SO₂ removal from flue gas by coal slurry scrubbing, coal pyrite sulfur can be simultaneously reduced. But satisfactory coal pyrite conversion cannot be achieved under normal scrubbing conditions. In the present work, aluminum oxide and aluminum sulfate were tested as additives to enhance the leaching of coal pyrite during SO₂ removal in a bubbling reactor. It was found that adding aluminum oxide or aluminum sulfate into the coal slurry could increase the coal pyrite conversion and SO₂ removal efficiency. The leaching process could be described by the reaction-controlled shrinking core model. Based on the facts that both aluminum and ferric irons can exist in aqueous solution in the form of sulfate and hydroxide complex ions, it was deduced that the attraction between the oppositely charged ions might promote the coal pyrite leaching reactions, suppress the formation of passive Fe solid products, and increase the concentration of soluble complexed Fe(III) which also acted as coal pyrite oxidant.

Climate change is expected to affect the groundwater quality by altering recharge, water table elevation, groundwater flow, and land use. In fractured bedrock aquifers, the quality of groundwater is a sensitive issue, particularly in areas affected by geogenic arsenic contamination. Understanding how climate change will affect the geochemistry of naturally occurring arsenic in groundwater is crucial to ensure sustainable use of this resource, particularly as a source of drinking water. This paper presents a review of the potential impacts of climate change on arsenic concentration in bedrock aquifers and identifies issues that remain unresolved. During intense and prolonged low flow, the decline in the water table is expected to increase the oxidation of arsenic-bearing sulfides in the unsaturated zone. In addition, reduced groundwater flow may increase the occurrence of geochemically evolved arsenic-rich groundwater and enhance arsenic mobilization by reductive dissolution and alkali desorption. In contrast, the occurrence of extreme recharge events is expected to further decrease arsenic concentrations because of the greater dilution by oxygenated, low-pH water. In some cases, arsenic mobilization could be indirectly induced by climate change through changes in land use, particularly those causing increased groundwater withdrawals and pollution. The overall impact of climate change on dissolved arsenic will vary greatly according to the bedrock aquifer properties that influence the sensitivity of the groundwater system to climate change. To date, the scarcity of data related to the temporal variability of arsenic in fractured bedrock groundwater is a major obstacle in evaluating the future evolution of the resource quality.

Biomixtures comprise the active part of biopurification systems (BPS) for the removal of pesticide-containing wastewater from agricultural origin. Considering that biomixtures contain an important amount of lignocellulosic substrates, their bioaugmentation with degrading ligninolytic fungi represents a promising way to improve BPS. The fungus Trametes versicolor was employed for the bioaugmentation of rice husk-compost-soil (GCS) biomixtures in order to optimize the removal of the highly toxic insecticide/nematicide carbofuran (CFN). Composition of biomixtures has not been optimized before, and usually, a volumetric composition of 50:25:25 (lignocellulosic substrate:humic component:soil) is employed. Optimization of the biomixture composition was performed with a central composite design, using the volumetric content of rice husk (pre-colonized by the fungus) and the volumetric ratio compost/soil as design variables. Performance of biomixtures was comprehensively assayed considering CFN removal, the production of toxic transformation products (3-hydroxycarbofuran/3-ketocarbofuran), the ability to mineralize [¹⁴C]carbofuran, and the residual toxicity in the matrix. According to the models, the optimal volumetric composition of the GCS biomixture is 30:43:27, which maximizes removal and mineralization rate, and minimizes the accumulation of transformation products. Results support the value of assessing new biomixture formulations according to the target pesticide in order to obtain their optimal performance, before their use in BPS.

Climatic condition, geology, and geochemical processes in an area play a major role on groundwater quality. Impact of these on the fluoride content of groundwater was studied in three regions-part of Nalgonda district in Telangana, Pambar River basin, and Vaniyar River basin in Tamil Nadu, southern India, which experience semi-arid climate and are predominantly made of Precambrian rocks. High concentration of fluoride in groundwater above 4 mg/l was recorded. Human exposure dose for fluoride through groundwater was higher in Nalgonda than the other areas. With evaporation and rainfall being one of the major contributors for high fluoride apart from the weathering of fluoride rich minerals from rocks, the effect of increase in groundwater level on fluoride concentration was studied. This study reveals that groundwater in shallow environment of all three regions shows dilution effect due to rainfall recharge. Suitable managed aquifer recharge (MAR) methods can be adopted to dilute the fluoride rich groundwater in such regions which is explained with two case studies. However, in deep groundwater, increase in fluoride concentration with increase in groundwater level due to leaching of fluoride rich salts from the unsaturated zone was observed. Occurrence of fluoride above 1.5 mg/l was more in areas with deeper groundwater environment. Hence, practicing MAR in these regions will increase the fluoride content in groundwater and so physica or chemical treatment has to be adopted. This study brought out the fact that MAR cannot be practiced in all regions for dilution of ions in groundwater and that it is essential to analyze the fluctuation in groundwater level and the fluoride content before suggesting it as a suitable solution. Also, this study emphasizes that long-term monitoring of these factors is an important criterion for choosing the recharge areas.

Combining bioassays and analytical chemistry screenings is a powerful approach to assess emerging organic micropollutants which are the main contributors to toxic potentials in complex mixtures of water matrices. The aim of this study was to assess the cytotoxic effect of the occurrence of emerging organic micropollutants discharged into river water through industrial wastewater and treated effluents. The cytotoxic effects of surface water, treated effluents, and industrial wastewater were assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Then, organic micropollutants of various chemical groups were identified using a detailed non-target screening based on gas chromatography coupled with a mass spectrometry detector (GC/MS). A significant cytotoxic effect on human intestinal epithelial Caco-2 cells was observed for all the samples. Caco-2 cell viability decreased by 17.99, 33.77, and 24.54 % for surface water, treated wastewater, and industrial water, respectively. The organic chemical compounds responsible for this toxic potential were identified using non-target chemical screening. Statistical correlation between cytotoxicity and the presence of emerging contaminants revealed that the cytotoxic effect was mainly due (r ≥ 0.42) to the occurrence of cyclopentasiloxane, decamethyl and cyclohexasiloxane, dodecamethyl, D-limonene, and ergoline-8-methanol, 8,9-didehydro-6-methyl while cytotoxicity was highly negatively correlated (r ≤ −0.42) to 2-ethylhexyl salicylate, 3-isopropoxy-1,1,1,7,7,7-hexamethyl-3,5,5-tris(trimethyl siloxy)tetrasiloxane, 6-acetyl-1,1,2,4,4,7-hexamethyltetralin, and (3-aminopropyltriethoxysilane. Seventy-six other compounds detected by GC/MS showed no correlation to cytotoxicity.

The content and speciation of heavy metals can fundamentally affect the hydrolysis of sludge. This research study investigates the migration and transformation rule of heavy metals during the hydrolysis process by measuring the content of exchangeables (F1), bound to carbonates (F2), bound to Fe-Mn oxides (F3), bound to organic matter (F4), and residuals (F5) under different periods of time undergoing hydrolysis. The results show that the hydrolysis process generally stabilized Cu, Zn, Mn, Ni, Pb, Cr, and As by transforming the unstable states into structurally stable states. Such transformations and stabilization were primarily caused by the changes in local metal ion environment and bonding structure, oxidation of sulfides, pyrolyzation of organic matter, and evaporation of resulting volatile materials. An X-ray diffractometry (XRD) of the residuals conducted after hydrolysis indicated that hydrolysis did have a significant influence on the transportation and transformation of heavy metals.

The olive oil industry produces a highly complex wastewater, known as olive oil mill wastewater (OOMW), which represents a relevant environmental problem for the Mediterranean region. Several physicochemical, biological and combined treatments have been tested to deal with this industrial externality but none was totally effective in reducing its toxicity for species inhabiting the receiving freshwater systems. Within this framework, nanotechnology appears as a promising research area, offering new approaches for the treatment of wastewaters based on the enhanced physical and chemical properties of nanomaterials (NMs). In this context, this work aimed to investigate the treatability of OOMW through several treatments involving advanced oxidation processes plus the use of two nanomaterials as catalysts (UV/H₂O₂, UV/TiO₂, UV/Fe₂O₃, UV/TiO₂/H₂O₂ and UV/Fe₂O₃/H₂O₂). The concentrations of the catalyst and of the oxidant agent were also investigated. The results obtained showed that photodegradation treatments combining TiO₂ or Fe₂O₃ NMs with H₂O₂ were the most efficient. Regarding the OOMW toxicity to Vibrio fischeri, it was significantly reduced with the following treatments: UV/TiO₂/H₂O₂ and UV/Fe₂O₃/H₂O₂. However, the highest reduction recorded for this parameter was obtained in the treatment with UV/H₂O₂. The use of NMs combined with H₂O₂ showed a great potential for removing phenols from OOMW, which have been pointed out as the major toxic compounds of this wastewater.