The potential leaching of pollutants present in harbor sediments has to be evaluated in order to choose the best practices for managing them. Little is known about the speciation and mobility of heavy metals in these specific solid materials. The objective of this paper is to determine and model the leachability of copper, lead, and zinc present in harbor sediments in order to obtain essential new data. The mobility of inorganic contaminants in a polluted harbor sediment collected in France was investigated as a function of physicochemical conditions. The investigation relied mainly on the use of leaching tests performed in combination with mineralogical analysis and thermodynamic modeling using PHREEQC. The modeling phase was dedicated to both confirm the hypothesis formulated to explain the experimental results and improve the determination of the main physico-chemical parameters governing mobility. The experimental results and modeling showed that the release of copper, lead, and zinc is very low with deionized water which is due to the stability of the associated solid phases (organic matter, carbonate minerals, and/or iron sulfides) at natural slightly basic conditions. However, increased mobilization is observed under pH values below 6.0 and above 10.0. This methodology helped to consistently obtain the geochemical parameters governing the mobility of the contaminants studied.

Effect of nitric oxide donor (sodium nitroprusside, SNP, 500 μM) or hydrogen peroxide scavenger (dithiothreitol, DTT, 500 μM) on cadmium (Cd) or copper (Cu) uptake (150 μM solutions) and toxicity using Scenedesmus quadricauda was studied. Combined treatments (Cd or Cu + DTT or SNP) usually ameliorated metal-induced toxicity at the level of pigments, proteins, and mineral nutrients in comparison with respective metal alone. Viability tests (MTT and TTC) showed the lowest values preferentially in Cu treatments, indicating higher toxicity in comparison with Cd. Cd showed low impact on amino acids while strong Cu-induced depletion was mitigated by DTT and SNP. Amount of ROS and NO showed the most pronounced responses in SNP variants being rather reciprocal than parallel and regulated ascorbate peroxidase activity. Blot gel analyses of hsp70 protein did not reveal extensive changes after given exposure period. Phenols were elevated by DTT alone while all Cu treatments revealed depletion. Total Cu content decreased while total Cd content increased in metal + SNP or metal + DTT. Subsequent experiment using lower Cd, SNP or DTT doses (10 and 100 μM) revealed concentration-dependent impact on Cd uptake. Overall, DTT was found to be more suitable for the amelioration of metal-induced toxicity.

The ubiquitous protozoa Toxoplasma gondii is now the subject of renewed interest, due to the spread of oocysts via water causing waterborne outbreaks of toxoplasmosis in different parts of the world. This overview discusses the different methods for detection of Toxoplasma in drinking and environmental water. It includes a combination of conventional and molecular tools for effective oocyst recovery and detection in water sources as well as factors hindering the detection of this parasite and shedding light on a promising new molecular assay for the diagnosis of Toxoplasma in environmental samples. Hopefully, this attempt will facilitate future approaches for better recovery, concentration, and detection of Toxoplasma oocysts in environmental waters.

Photocatalytic degradation of dissolved organic carbon (DOC) by utilizing Fe(III)-doped TiO2 at the visible radiation range is hereby reported. The photocatalyst was immobilized on sintered glass frits with the coating done by wet method, calcinated at 500 °C and then applied in a photodegradation reactor. The addition of a transition metal dopant, Fe(III), initiated the red shift which was confirmed by UV-Vis spectroscopy, and the photocatalyst was activated by visible radiation. X-ray diffraction patterns showed that Fe(III) doping had an effect on the crystallinity of the photocatalysts. Mixtures of DOC and associated coloured solutions were degraded in first-order kinetics, showing that the degradation process was not dependent on intermediates or other species in solution. A reactor with a catalyst coating area of 12.57 cm(2) was able to degrade 0.623 mg of the dissolved material per minute. Exposure of the reactor to hostile acidic conditions and repeated use did not compromise its efficiency. It was observed that the reactor regenerates itself in the presence of visible light, and therefore, it can be re-used for more than 100 runs before the performance dropped to <95 %. The results obtained indicate that the photocatalyst reactor has a great potential of application for use in tandem with biosorbent cartridges to complement water purification methods for domestic consumption.

The potential of the microbial communities present in the intertidal zone of an unimpacted beach (a beach that did not suffer any significant oil spill) to degrade hydrocarbons was investigated. For that, laboratory-based microcosms (50-ml flasks) were set up with sandy beach sediment spiked with crude oil and incubated with local seawater for 15 days in the dark. Three bioremediation treatments were tested (biostimulation (BS), autochthonous bioaugmentation (AB), and combined treatment of biostimulation + bioaugmentation (BS + AB)) and the results were compared with natural attenuation (NA). Visual inspection showed clearly an oil solubility increase (confirmed by a higher hydrocarbons concentration in supernatant solutions) for all tested treatments when compared to NA. Significant degradation of the oil, shown by different profiles of petroleum hydrocarbons, was also observed for the different treatments particularly for BS + AB. Therefore, the microbial community of this unimpacted beach sediment could respond to an oil spill, degrading hydrocarbons. But to increase the natural attenuation pace, obtained results indicated that BS + AB is an appropriate approach for the bioremediation of beaches recently impacted by an oil spill. The autochthonous microbial cultures can be obtained “before” or “after” the contamination of the target site, being inoculated into the site right after it contamination.

Wastewater treatment is an important source of nitrous oxide (N₂O), which is a strong greenhouse gas and dominate ozone-depleting substance. The purpose of this study was to evaluate the effect of carbon source on N₂O emission from anoxic/oxic biological nitrogen removal process. The mechanisms of N₂O emission were also studied. Long-term experiments were operated to evaluate the effect of three different carbon sources (i.e., glucose, sodium acetate, and soluble starch) on N₂O emission characteristics. And batch experiments, in the presence or absence of specific inhibitors, were carried out to identify the sources of N₂O emission. The ammonia-oxidizing bacteria (AOB) and denitrifiers community compositions under different circumstances were also analyzed based on which the underlying mechanisms of N₂O emission were elucidated. The conversion ratios of N₂O in reactors with glucose, sodium acetate, and soluble starch were 5.3 %, 8.8 %, and 2.8 %, respectively. The primary process responsible for N₂O emission was nitrifier denitrification by Nitrosomonas-like AOB, while denitrification by heterotrophic denitrifiers acted as the sink. Reactor with sodium acetate showed the highest N₂O emission, together with the highest nitrogen and phosphate removal ratios. Carbon source has a significant impact on N₂O emission quantity and relatively minor effect on its production mechanism.

Although the long incubation time of biochemical oxygen demand (BOD₇) measurements has been addressed by the use of microbial biosensors, the resulting sensor-BOD values gained from the measurements with specific industrial wastewaters still underestimates the BOD value of such samples. This research aims to provide fast and more accurate BOD measurements in the dairy wastewater samples. Unlike municipal wastewater, wastewater from the dairy industry contains many substrates that are not easily accessible to a majority of microorganisms. Therefore, a bacterial culture, Microbacterium phyllosphaerae, isolated from dairy wastewater was used to construct a semi-specific microbial biosensor. A universal microbial biosensor based on Pseudomonas fluorescens, which has a wide substrate spectrum but is nonspecific to dairy wastewater, was used as a comparison. BOD biosensors were calibrated with OECD synthetic wastewater, and experiments with different synthetic and actual wastewater samples were carried out. Results show that the semi-specific M. phyllosphaerae-based microbial biosensor is more sensitive towards wastewaters that contain milk derivates and butter whey than the P. fluorescens-based biosensor. Although the M. phyllosphaerae biosensor underestimates the BOD₇ value of actual dairy wastewaters by 25–32 %, this bacterial culture is more suitable for BOD monitoring in dairy wastewater than P. fluorescens, which underestimated the same samples by 46–61 %.

Since data on mercury (Hg) levels in Caucasians and African Americans (AAs) of both genders are lacking, this study aims to present toenail Hg distributions and explore the potential determinants using data from the Coronary Artery Risk Development in Young Adults Trace Element Study. Data from 4,344 Americans, aged 20–32 in 1987, recruited from Oakland, Chicago, Minneapolis, and Birmingham were used to measure toenail Hg levels by instrumental neutron-activation method. The Hg distribution was described with selected percentiles and geometric means. Multivariable linear regression (MLR) was used to examine potential determinants of Hg levels within ethnicity–gender subgroups. The geometric mean of toenail Hg was 0.212 (95 % CI = 0.207–0.218) μg/g. Hg levels varied geographically with Oakland the highest [0.381 (0.367–0.395) μg/g] and Minneapolis the lowest [0.140 (0.134–0.147) μg/g]. MLR analyses showed that male gender and AA ethnicity were negatively associated with toenail Hg levels, and that age, living in Oakland city, education level, alcohol consumption, and total fish intake were positively associated with toenail Hg concentrations within each ethnicity–gender subgroup. Current smokers were found to have higher Hg only in AA men. This study suggested age, gender, ethnicity, study center, alcohol, education level, and fish consumption consistently predict toenail Hg levels. As fish consumption was the key determinant, avoiding certain types of fish that have relatively high Hg levels may be crucial in reducing Hg intake.

Soybean stover-derived biochar was used to immobilize lead (Pb) in military firing range soil at a mass application rate of 0 to 20 wt.% and a curing period of 7 days. The toxicity characteristic leaching procedure (TCLP) was performed to evaluate the effectiveness of the treatment. The mechanism responsible for Pb immobilization in military firing range soil was evaluated by scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) and x-ray absorption fine structure (XAFS) spectroscopy analyses. The treatment results showed that TCLP Pb leachability decreased with increasing biochar content. A reduction of over 90 % in Pb leachability was achieved upon treatment with 20 wt.% soybean stover-derived biochar. SEM-EDX, elemental dot mapping and XAFS results in conjunction with TCLP leachability revealed that effective Pb immobilization was probably associated with the pozzolanic reaction products, chloropyromorphite and Pb-phosphate. The results of this study demonstrated that soybean stover-derived biochar was effective in immobilizing Pb in contaminated firing range soil.

Sulfonylurea herbicides are extensively widespread for the protection of a variety of crops and vegetables because of their low application rates, high selectivity and low persistency in the environment; unfortunately, their low persistence does not always correspond to a lower toxicity, since new species potentially more toxic and stable than the precursor herbicides can form, owing to natural degradation processes. Here, the photodegradation of amidosulfuron in aqueous solutions was studied by high-performance liquid chromatography with diode array detection and tandem mass spectrometry to identify the degradation products in order to outline the environmental fate of the molecules generating from the simulation of one of the natural processes that can occur, i.e., photoinduced degradation. The photodegradation process results in a first order kinetic reaction with a t₁/₂value of 276 h (11.5 days) and a kinetic constant of 0.0027 h⁻¹, and three possible degradation products were identified. The results obtained are then compared to those obtained in previous works carried out in comparable experimental conditions about nicosulfuron and tribenuron-methyl, two sulfonylurea herbicides belonging to different classes, and to literature data: hypotheses on the existence of preferential degradation pathways are then drawn, in consequence of the molecular structure of the sulfonylurea pesticide. In particular, the use of organic solvents to obtain complete solubilization of the sample plays a fundamental role and deeply influences the degradation processes that, therefore, not always fully adhere to the actual natural photodegradation pathways. Moreover, considerations about toxicity were driven since the complete mineralisation of the sample is not reached: even when the parent pesticides are totally degraded, they are, however, transformed into other organic compounds showing, if subject to ecotoxicological tests, at least the same toxicity of the precursor herbicides. The evidence here presented suggests that, at least for the class of sulfonylurea pesticides, their professed low persistence actually does not produce any real advantage.