Mercury contamination in water has been an issue to the environment and human health. In this article, mercury in marine and oceanic waters has been reviewed. In the aquatic environment, mercury occurs in many forms, which depend on the oxidation-reduction conditions. These forms have been briefly described in this article. Mercury concentrations in marine waters in the different parts of the world have been presented. In the relevant literature, two models describing the fate and behavior of mercury in saltwater reservoirs have been presented, a conceptual model which treats all the oceans as one ocean and the “ocean margin” model, providing that the ocean margins manifested themselves as the convergence of continents and oceans, covering such geological features, such as estuaries, inland seas, and the continental shelf. These two conceptual models have been summarized in the text. The mercury content in benthic sediments usually reflects is level in the water reservoir, particularly in reservoirs situated in contaminated areas (mines, metallurgical plants, chemically protected crops). The concentrations of mercury and its compounds determined in the sediments in surface waters in the different parts of the world have been presented. Due to the fact that the pollution caused by mercury is a serious threat for the marine environment, the short paragraph about mercury bioaccumulation in aquatic organisms has been included. The cited data demonstrated a large scatter of mercury contents both between the fish species and the water areas. Mathematical models, valuable tools which provide information about the possible responses of ecosystems, developed to simulate mercury emissions, both at a small scale, for local water reservoirs, and at a global scale, as well as to model mercury bioaccumulation in the chain web of aquatic systems have been described.

Textile dyes and antibiotics are two main classes of environmental pollutants which could be found in soil and water. Those persistent pollutants can have a negative influence on plant growth and development and affect the level of secondary metabolites. In the present work, we studied the effect of textile dyes and antibiotics on total leaf flavonoid contents in wheat (Triticum aestivum L.). Contaminant solutions were applied daily using concentrations of 0.5 mg L⁻¹ (lower) and 1.5 mg L⁻¹ (higher dose) for either 1 or 2 weeks. We observed that exposure to the higher concentration of textile dyes resulted in a reduction in flavonoid content while antibiotics enhanced flavonoid contents at lower doses of exposure and reduced at higher doses of exposure. These results suggest that diffuse chronic pollution by artificial organic contaminants can importantly alter antioxidative capacity of plants.

In the present paper we suggest a novel calibration method of the model for hydrodynamic and contaminant transport using the example of a sewage disposal site set up uninsulated in a sandy environment. With the hydrodynamic model we applied time-dependent model calculations in order to fit the individual hydrodynamic parameters. For the calibration of the transport model, sodium was chosen, which has a negligible retardation factor. We demonstrated that this approach is suitable for creating a model that provides calculated results comparable to the actually measured, experimental ones. The created model proved to be appropriate for use in the estimation of the maximal spatial extension of the contamination, which—in the case of the investigated sewage disposal site—was found to be 0.1 km² in the near-surface (1–3 m deep) layers, whereas it was three times higher at a depth of 40–60 m.

Inorganic arsenic occurs mainly in As(III) and As(V) states in water environment, but arsenite is more toxic and difficult to remove than arsenate by usual adsorption processes. To achieve the in situ oxidation of As(III) and simultaneous removal of both As(III) and As(V) in water, a novel-layered double hydroxide (Mg–Fe–S₂O₈–LDH) with the intercalation of persulfate has been designed and synthesized by a calcination-reconstruction method. The arsenic adsorption performances and removal mechanism with the Mg–Fe–S₂O₈–LDH material were studied. The experimental result showed that, since the strong oxidation ability of the exchangeable persulfate ions from the LDH, the As(III) species in water were almost completely oxidized to the As(V) state and simultaneously adsorbed onto the Mg–Fe–S₂O₈–LDH. It was found that the maximum adsorption capacity for As(III) and As(V) in single-pollutant system was 75.00 and 75.63 mg·g⁻¹, respectively. When the adsorbent dosage was 0.5 g·L⁻¹ for a mixed As(III) and As(V) solution, the batch experiment showed that the residual arsenic concentration can be reduced from 1 mg·L⁻¹ to lower than the limit value of drinking water standard recommended by WHO. It indicated that the synthesized Mg–Fe–S₂O₈–LDH is a potential attractive adsorbent for simultaneous removal of As(III) and As(V) in water.

Acid mine drainage (AMD) is a persisting environmental problem and a grievous nuisance in the mining sector. In this study, iron (Fe(II)) removal was tested in AMD samples collected from the Enugu Okpara abandoned coal mine (Nigeria), having iron concentrations of ∼1300 mg/l. Digestion, toxicity characteristic leaching procedure (TCLP), and batch adsorption tests using coal bottom ash (BA), bentonite clay (BC), and coal fly ash (FA) were performed. Apart from elucidating the effects of adsorbent dose and initial Fe(II) concentrations on the maximum adsorption capacity (q ₑ) of the adsorbents, the experimental data were also fitted to well-known adsorption isotherms and kinetic models. The results from batch tests showed that the optimum adsorbent dosages for BA, BC, and FA were found to be 3, 4, and 4 g per 100 ml, respectively. Among the different adsorption isotherm models tested, the Temkin model fitted the experimental data well for Fe(II) removal. Results from kinetic analysis showed that the Fe(II) removal efficiency increased with an increase in the contact time and then remained almost constant after 30 min for the three tested adsorbents.

Sorption equilibria of copper(II) ions onto palygorskite and sepiolite clay minerals were studied as a function of temperature. The experimental data were fitted to the Langmuir, Freundlich, Temkin, and R-D models to obtain the isothermal constants. van’t Hoff, Gibbs, Clausius–Clapeyron, and modified Arrhenius equations were also employed to evaluate the thermodynamic parameters involved in Cu sorption. The results showed that fibrous clay minerals exhibit enhanced Cu(II) sorption capacities at higher temperatures. Enthalpy changes (ΔH°) were found to be positive, confirming that the process of Cu(II) sorption on both palygorskite and sepiolite was endothermic. Positive values were also obtained for the entropy changes (ΔS°), which suggests increased randomness at the solid-solution interface during the sorption of Cu(II) ions on both fibrous clay minerals investigated. The free energy changes (ΔG°) were negative for all the different temperatures and initial Cu(II) concentrations tested, indicating that sorption on the minerals is spontaneous and favorable. It was, therefore, concluded that sorption of Cu(II) ions on fibrous clay minerals is entropically driven. The values of isosteric heat of sorption (∆H ₓ) decreased with increasing sorption density, which shows that the clay surface is heterogeneous in terms of the active sites available for Cu(II) retention. The values of activation energy (E ₐ) and sticking probability (S *) generally lied within the ranges associated with physisorption for palygorskite and chemisorptions for sepiolite. In conclusion, the thermodynamic parameters investigated revealed the higher tendency and capacity of sepiolite, compared to palygorskite, for the feasible, spontaneous, and endothermic retention of Cu(II). However, the intensity of Cu(II) interactions with the fibrous clay minerals was found to depend to a large extent on the temperature and the initial Cu loading of the systems.

High serum concentrations of polychlorinated biphenyls (PCBs) have been reported previously among residents of Anniston, Alabama, where a PCB production facility was located in the past. As the second of two cross-sectional studies of these Anniston residents, the Anniston Community Health Survey: Follow-Up and Dioxin Analyses (ACHS-II) will yield repeated measurements to be used to evaluate changes over time in ortho-PCB concentrations and selected health indicators in study participants. Dioxins, non-ortho PCBs, other chemicals, heavy metals, and a variety of additional clinical tests not previously measured in the original ACHS cohort will be examined in ACHS-II. The follow-up study also incorporates a questionnaire with extended sections on diet and occupational history for a more comprehensive assessment of possible exposure sources. Data collection for ACHS-II from 359 eligible participants took place in 2014, 7 to 9 years after ACHS.

Radionuclides were determined in streams and rivers receiving mine drainage from old uranium mines at the center of Portugal. Results showed enhanced radioactivity levels in some areas impacted by uranium mining and milling wastes, but levels were lower than several years ago due to current water treatment of mine drainage. In some areas, such as at the village of Cunha Baixa, water from wells was contaminated by acid mine drainage, and it is not suitable anymore for human consumption and irrigation of horticulture plots. In the present, villages and towns near those old uranium mines have tap water from public networks supplied from artificial lakes built in major rivers of the region. This tap water showed compliance with the recommended limits of total alpha and total beta radioactivity, and it is suitable for human consumption. Radiation exposure of the population was therefore controlled, but current water supply is much more costly than it was with local water sources.

Heavy metal pollution in urban soil has become a serious environmental issue in China since the last three decades. Attention has been given to the investigation of soil contamination; however, there is little information available on the variation of heavy metal pollution in soils. To resolve this problem and provide references on similar regions, 18 topsoil (0∼20 cm) samples were collected from identical sites of districts that with different functions in Kaifeng City in 1994 and 2012. Total contents of As, Cd, Hg, and Pb were determined by standard methods. The variation of heavy metal pollution was evaluated by using geoaccumulation index and pollution load index. Results show a descending trend in heavy metal pollution of soil in Kaifeng City that demonstrated over the last 20 years, though there are still some contaminations in 2012. The highest concentration of soil metal was observed in industrial district, followed by the cultural and educational district, administrative business district, and entertaining district in turn. Concentrations of Pb in all soils and As in most soils were higher in 2012 than that in 1994, which mainly due to the rapid increase of motor vehicles and domestic garbage. Meanwhile, the concentrations of Hg and Cd in most soils were lower in 2012 than that in 1994, as the relocation and shutdown of industry and the wide development of environmental facilities. Land use and land cover change in urban areas can effect on soil metal pollution. When farmland transforms into urban land, the concentrations of soil metals would be increased, and also, the soil pollution will increase severely.

The application of hydroxyapatite (HAP) can transform lead into pyromorphite in the soil. However, it is not clear how the physicochemical properties of soil enhance or reduce the formation of pyromorphite. This study determined that the presence of ferrihydrite or soil moisture condition was a more important factor to enhance the formation of pyromorphite. We also evaluated lead sorption characteristics and stability in soil with HAP in the presence of ferrihydrite. The difference in the maximum lead removal capacity of soil with and without 5 wt% ferrihydrite corresponded to 10.4% of the difference in lead removal between soils with and without HAP. In artificially contaminated soil with a 50% water-holding capacity, the ratio of lead that formed into pyromorphite was compatible between soils with and without ferrihydrite at 22% and 28% of added lead, respectively. In a percolation test, almost all of the added lead was transformed into pyromorphite, despite the presence of ferrihydrite. In both water and a 0.1-M citric acid extraction, the differences in lead extracted from the contaminated soil with HAP with or without ferrihydrite were very small compared with water-soluble lead in soil without HAP. This study indicated that in soil with 5 wt% ferrihydrite, lead was removed and converted into pyromorphite by HAP with a little disturbance by ferrihydrite, and the immobilized lead would be stable. In addition, this study suggested that the soil moisture condition was a more important factor for the formation of pyromorphite than the presence of ferrihydrite.