Aquatic organisms might be exposed episodically or continuously to chemicals for long-term periods throughout their life span. Pesticides are one example of widely used chemicals and thus represent a potential hazard to aquatic organisms. In addition, these chemicals may be present simultaneously in the environment or as pulses, being difficult to predict accurately how their joint effects will take place. Therefore, the aim of the present study was to investigate how Daphnia magna (clone k6) exposed throughout generations to a model pesticide (the fungicide carbendazim) would react upon an exposure to another chemical compound (triclosan) and to a mixture of both chemicals (carbendazim and triclosan). Responses of daphnids continuously exposed to carbendazim and kept in clean medium will be compared using immobilization tests and the comet assay (DNA integrity). The results showed that triclosan presented similar toxicity to daphnids exposed for 12 generations (F12) to carbendazim (similar 48-h-LC₅₀ values for immobilization data), when compared with daphnids kept in clean medium. However, at subcellular level, daphnids previously exposed to carbendazim for 12 generations (F12) showed different responses than those from clean medium, presenting a higher toxicity; a general higher percentage of DNA damage was observed, after exposure to a range of concentrations of triclosan and to the binary combination of triclosan + carbendazim. The patterns of toxicity observed for the binary mixture triclosan + carbendazim were generally similar for daphnids in clean medium and daphnids exposed to carbendazim, with a dose level deviation with antagonism observed at low doses of the chemical mixture for the immobilization data and a dose ratio deviation with synergism mainly caused by triclosan for DNA damage. With this study, we contributed to the knowledge on long-term induced effects of carbendazim exposure, while looking at the organismal sensitivity to another chemical (triclosan) and to a mixture of carbendazim and triclosan using lethality as an endpoint at the individual level and DNA damage as a subcellular endpoint.

Due to the dramatically increasing production of excess sludge during biological wastewater treatment, the development of an economical, efficient, and environmentally friendly sludge dewatering method is highly required. Herein, Bdellovibrio-and-like organisms (BALOs), a group of predatory bacteria were applied for waste sludge dewaterability enhancement and biomass reduction and the potential biolysis mechanisms were elaborated. Generally, the satisfying biolysis performance was obtained for the sludge with the moderate total solid (TS) content (1.5–2.5%). Within 24-h sludge biolysis with our isolated and enriched BALOs, the sludge specific resistance to filtration value as the dewaterbility index reached the maximal reduction rate of 65.3 ± 6.4%. Meanwhile, the concentrations of released soluble nitrogen and phosphorous significantly increased by 57.4 ± 3.3 and 56.7 ± 6.1%, respectively. Moreover, the contents of tightly bound extracellular polymeric substances (EPS) dramatically decreased after sludge biolysis while the loosely bound EPS contents increased, which implied the disruptions of sludge flocs structure for sludge dewaterability improvement. High-throughput sequencing results revealed the remarkable shift of sludge’s microbial community structure after biolysis treatment. The relative abundances of the dominant genera Ferruginibacter, Pseudomonas, and Thermomonas related to denitrification or flocs structure stabilization dramatically decreased. The noticeable increasing populations of Comamonas and Hyphomicrobium in abundances suggested the potential re-growth of the surviving microbial cells in response to BALO invasions. Overall, BALO predation could disintegrate the waste sludge structure, promote the cell lysis and the intracellular substances release, and cause the variations of microbial community compositions to efficiently improve the sludge dewaterability.

The use of engineered nanomaterials (ENMs) increases concerns relating to their fate, behavior, and toxicity due to their increased exposure to the environment. These ENMs end up in wastewater treatment plants (WWTPs), and the bacteria in these systems are sensitive to compounds such as heavy metals, which reduces the functionality of the WWTP. In this work, the fate and behavior of Bi₂O₃-BiVO₄ in a WWTP using the OECD 303A guideline was studied. The Bi₂O₃-BiVO₄ NPs were synthesized through a hydrothermal and impregnation method. X-ray diffraction showed monoclinic phases of both Bi₂O₃ and BiVO₄ NPs. The effect of Bi₂O₃-BiVO₄ NPs was monitored using chemical oxygen demand (COD) and 5-day biological oxygen demand (BOD₅). The COD and BOD₅ for the sludge retention time where the NPs were added was > 70%. This showed that the NPs had no effect on the functionality of the treatment processes as it was further affirmed by the TPC measurements. Inductively coupled plasma–optical emission spectroscopy (ICP-OES) showed that the fate of the NPs was through the activated sludge than the effluent, whereby 90% of Bi and V were absorbed in the activated sludge and 10% in the effluent. The results indicate that the NPs have the potential to permeate through the environment segments through the wastewater sludge compared to the effluent. XRD analysis of the test sludge showed that the crystal phases of the heterojunction remained unchanged, and this could ascertain that the treatment conditions did not transform the NPs into toxic forms.

Cadmium (Cd) phytoextraction efficiency basically depends on Cd accumulation in their tissues. Thus, our aim in this study was to select biochemical, morpho-physiological, nutritional, and productive responses associated to Cd accumulation in the roots, stems and sheaths, and leaf blades of Panicum maximum cv. Massai (Massai grass), using the random forests analysis. Massai grass was exposed to combinations of three sulfur (S) concentrations (0.1, 1.9, and 3.7 mmol L⁻¹) and two Cd concentrations (0.0 and 0.1 mmol L⁻¹) in nutrient solutions. The dry biomass production of Massai grass exposed to Cd decreased by around 50% in relation to control. However, there were no visual symptoms of Cd toxicity in the shoot of this plant, even with Cd concentrations in their shoot exceeding 100 mg kg⁻¹ DW. The lowest dry biomass production of the plants exposed to Cd combined with the absence of visual symptoms of Cd toxicity indicates us that Massai grass is a bioindicator plant that can greatly cope with the Cd-induced stress, but in a little bit different way from other plants. Antioxidant enzymes apparently are not essential for Massai grass cope with Cd-induced stress, differently of other mechanisms (e.g., higher synthesis of thiol compounds and amino acids involved on reactive oxygen species (ROS) scavenging and Cd chelation). Probably, the plant responses that most explained Cd accumulation in Massai grass can be used to identify grasses with high capacity to accumulate Cd in phytoremediation programs with this group of plants.

The present study aims to assess the impact of a gold mine located in the southeastern part of Burkina Faso on local soil quality. This information is needed in order to determine any health hazards and potential remediation strategies as the mining site is expected to be turned over to the local community after the closure of the mine. For the purpose, total minor and trace elements analysis as well as a sequential extraction were performed and results were interpreted using different methodologies: enrichment factor (EF), geoaccumulation index (Igeo) computed using two separate background samples, and comparison to selected national standard. The soil analysis revealed a moderate to significant soil EF and Igeo with hotspots located closer to the ore processing plant and on the east side of the site, with a maximum arsenic concentration of 286.55 ± 12.50 mg/kg. Sequential extraction revealed, however, that less than 2% of the arsenic is found in the exchangeable part. Cobalt and zinc are more distributed in the different fractions than arsenic. Geogenic and anthropogenic contributions were revealed by the study. Graphical Abstract .

Plitvice Lakes National Park presents one of the most beautiful karst complexes in the world. Its waters are supersaturated with dissolved calcium carbonate (calcite) which is released and deposited in the form of tiny crystals as a result of water splashing at tufa barriers. Sulphates, present in the particulate matter (PM), can be deposited on the surface of the calcite. In the air, sulphate particles are formed by the oxidation of SO₂ in a series of chemical reactions as reported by Li et al. (Atmospheric Chemistry and Physics 6:2453–2464, 2006). Fast oxidation of SO₂ in nature can also take place on the surface of the calcite in the presence of ozone and is significantly enhanced by high humidity as reported by Li et al. (Atmospheric Chemistry and Physics 6:2453–2464, 2006) and Massey (Science of the Total Environment 227(2–3), 109–121, 1999). The resulting sulphates can destroy the surface of the calcite and indirectly influence the composition and quality of water. Hourly concentrations of ozone, PM₁₀ and PM₂.₅ at the monitoring station Plitvice Lakes in the period from 2012 to 2014 are presented. After assessing the observed values of both PM and ozone, presently there are no significant danger for Plitvice Lakes. However, this can change in the future so continuous monitoring will be necessary in the future.

One hundred and fifty years of mineral extraction throughout the mountainous Ruby Creek watershed, Washington has left a legacy of historical hard rock mines and placer claims and their wastes. We conducted a watershed-scale chemical analysis of these gold-bearing tributaries, accounting for seasonal variability in streamflow, to identify spatial and temporal changes in stream chemistry and attribute them to natural processes or mining activities. We used hierarchical cluster analysis (HCA) to group chemically similar water samples based on concentrations of 23 metals, pH, and conductivity and compared the chemistry of HCA-generated clusters of water samples using pairwise comparisons to find chemical patterns. Total concentrations of As, Ba, Ca, Mg, Na, Sb, and Se, dissolved concentrations of Fe, and conductivity increased as streamflow progressed from snowmelt-influenced to baseflow. High total concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, V, and Zn during spring snowmelt and after rains were attributable to acid mine drainage at historical hard rock mines and prospect sites. Smaller-scale placer mining, by way of suction dredging and motorized gold panning, was associated with high concentrations of Al, Ba, Cd, Co, Fe, Mg, Mn, Mo, and Zn downstream. Stream biota may be adversely affected by exposure to Pb, which exceeded USEPA’s Aquatic Life Criteria, and exposure to particulate metals suspended in the water column.

Every year, the leather tanning industry produces substantial quantities of residues such as chrome-tanned leather shavings (CTLS), which contain considerable amounts of Cr(III) salts. The residues have no particular value and under natural conditions can transform into toxic Cr(VI) wastes. The objective of the present work is to evaluate the transformation of these residues into carbon adsorbents at low temperatures (< 600 °C), using ZnCl₂ as an activating agent. The pyrolysis temperature and residence times were studied. The materials were characterized and qualified by Acid Black 210 (AB) adsorption. The results indicated that low amounts of chromium oxides (less than 2% of Cr), in the form of 50–200 nm particles, remained after the synthesis procedure. The deposited chromium oxides were present in (II), (III), and (IV) oxidation states. The low preparation temperatures employed prevented further chromium oxidation to Cr(VI). Maximum surface areas of 439 m²/g were obtained. The materials efficiently removed AB (maximum experimental adsorption capacity of 44.4 mg/g) by means of electrostatic interaction caused by the positively charged distribution of the carbons. The adsorption capacity was not affected by temperature, but pH had a mixed effect due to the combination of a shift in surface charge distribution and dye speciation. The results demonstrated that it is possible to obtain a value-added product, i.e., carbons modified with chromium nanoparticles for dye removal, from a hazardous residue of the tanning industry.

The adsorption properties and mechanisms of methylene blue (MB) onto novel biochars produced by the fallen leaves of Magnolia grandiflora Linn (MGL), at different pyrolysis temperatures (450 °C, 500 °C, 550 °C) were explored. Results of the adsorption experiments revealed that the fallen leaf-biochar of MGL (MGLB) pyrolyzed at 450 °C (MGLB450) had the highest adsorption capacity of MB (114.15 mg g⁻¹) and MGLB pyrolyzed at 500 °C (MGLB500) was lowest (88.13 mg g⁻¹). The characterization results showed that the BET surface area (41.784 m² g⁻¹) and total pore volume (0.043 cm³ g⁻¹) of MGLB450 were low, but the contents of oxygen-containing functional groups were highest. Oxygen-containing functional group might have a greater impact on the adsorption of MB than its physical characteristics. The adsorption capacity increased with reaction temperature, indicating that the MG adsorption onto biochars was endothermic. The higher initial concentrations of MB and pH were beneficial to adsorption. The adsorption kinetics showed that the adsorption followed pseudo-second-order kinetics model. The obtained equilibrium data were fitted better by Langmuir model rather than Freundlich model.

To explore the possibility of using flue gas desulfurization gypsum (FGDG) for inhibiting phosphorus (P) loss due to agricultural runoff, a 3-year study was performed in the farmlands of Chongming Dongtan between 2012 and 2015. Five different quantities of FGDG were used to treat the soil, and the effects of different treatments on the characteristics of soil P and crop growth were investigated. The results showed that 2 years after application of FGDG, the soil density at a depth of 0–10 cm decreased by 4.35–7.97%, the porosity increased by 1.77–11.0%, and the topsoil permeability increased by 0.87–3.81 times. Although the use of FGDG did not change the total P concentration in the soil, it decreased the concentration of sodium bicarbonate extractable P in the soil. Compared to the control, the average extractable P concentration at depths of 0–10 cm, 10–20 cm, and 20–30 cm decreased by 22.0–46.1%, 26.9–40.5%, and 22.8–34.8%, respectively. The inorganic P in the soil increased as the amount of FGDG increased, and the increase was mainly as Ca–P in the forms Ca₂–P and Ca₁₀–P. The decrease in bicarbonate extractable P and increase in inorganic P in the soil did not affect the growth of the crops, and the biomass and output of the crops increased compared to the control. Therefore, FGDG can enhance soil P immobilization, thus reducing soluble P runoff from farm fields, and improving water quality in receiving lakes and rivers while maintaining P nutrition to the crops.