This study evaluated the seed germination and dry mass accumulation of five plant species (Brassica napus L., Brassica rapa L., Celosia cristata L., Tagetes erecta L., and Calendula officinalis L.) grown in five mine tailings collected from Zacatecas, Mexico. Sampled mines were El Bote, Noria de San Pantaleon, Noria de Angeles, Vetagrande, and El Bordo-El Lampotal, in which Pb (3.9–69.7 mg kg⁻¹), As (0.7–26.2 mg kg⁻¹), Hg (0.05–0.10 mg kg⁻¹), and Au (0.01–0.02 mg kg⁻¹) were detected. The most abundant elements at each mine site were as follows: Pb and Au (3.9 and 0.023 mg kg⁻¹, respectively) for El Bote; As, Pb, and Hg (7.4, 6.1, and 0.10 mg kg⁻¹, respectively) for the Noria de San Pantaleon; Pb, As, and Hg (69.7, 26.2, and 0.08 mg kg⁻¹, respectively) for Noria de Angeles; Pb (20.8 mg kg⁻¹) for Vetagrande; and Pb (5.3 mg kg⁻¹) for El Bordo-El Lampotal. Both Noria de Angeles and Vetagrande mine tailings had high values of sodium, sulfates, and electrical conductivity, chemical properties that impaired seed germination and dry mass accumulation. Regardless the mining tailings, B. napus showed high seed germination (66 %), tolerance, growth, and total dry mass accumulation (0.041 g). Either B. napus or C. cristata has good potential for stabilizing or recovering metals from mine tailings.

A shortage in available water resources for rice production makes the evaluation of rice yield and greenhouse gas emission in response to drought caused by water scarcity vital. Here, we examined three forms of irrigation management (normal amount [NA], 70 % of NA [NA 70 %], and 30 % of NA [NA30%]) and two rice varieties (Oryza sativa L. cv. Hanyou 8 and Oryza sativa L. cv. Huayou 14) to determine their effects on CH₄ emission and rice yield in two rice growing seasons. Hanyou 8 is a variety of water-saving and drought-resistance rice (WDR), while Huayou 14 is a common rice variety with no known adaptation to drought conditions. NA 70 % reduced CH₄ emission by 30.3–53.3 %, and NA 30 % further depressed CH₄ emission by 51.0–76.7 % relative to NA in both seasons. However, NA 70 % and NA 30 % significantly decreased rice yield by 6.3 % (P < 0.05) and 10.1 % (P < 0.01), respectively, for Huayou 14 when compared with NA in the relatively dry season. Conversely, no differences in rice yield among different irrigation managements were observed for Hanyou 8 in both seasons, suggesting that Hanyou 8 is more drought-resistant than Huayou 14 in terms of rice yield. The results suggest that, to meet the water scarcity, the use of rice varieties with water-saving and drought-resistant traits may minimize rice yield loss and mitigate CH₄ emission in the rice-cultivated regions of the world.

Environmental pollution by pentachlorophenol (PCP) is a critical concern worldwide, and microbial bioremediation could constitute an ecologically friendly solution. The main objectives of this study were at first to clarify the factors, affecting the ability and efficiency of PCP biodegradation by the bacterium isolate P6, and secondly to optimize the condition of using P6 for PCP bioremediation. The PCP mineralizing bacterium was isolated from the contaminated forest soil of Tunisia, and it was identified as Citrobacter freundii (C. freundii), by using conventional and molecular characteristics. The HPLC and spectroscopic analysis were used to investigate the PCP degradation and the biomass formation by this isolate P6. The main results showed that P6 was able to degrade or to transform more than 98 % of 640 mg/l PCP afterwards 168 h in mineral salt medium (MSM). As well, the optimal aerobic growth conditions of P6 in MSM include essentially the range of pH (4 ≤ pH ≤ 9) and of temperature (25 °C < temperature < 30 °C). The addition of glucose as extra carbon sources has an effect to enhance the PCP biodegradation. On the other side, this isolate of C. freundii is capable to remove or transform around 95.33 % of PCP added in the sterilized soil suspension supplemented with PCP and adjusted to a final concentration of around 400 mg/l during 2 weeks of incubation at 25 °C. This last result argues in favor of the use of this strain P6 of C. freundii as a microbial tool of remediation of PCP-contaminated site.

Long-term irrigation with recycled water (RW) that contains high salt may pollute groundwater. The HYDRUS-1D model was texted against soil water content and electrical conductivity (ECe) observed in a summer maize and winter wheat rotational field irrigated with ground water (GW) and RW; then, the risk for polluting groundwater in two regions of Beijing was evaluated. The comparisons indicated that the simulated soil water content and ECe values were generally in agreement with the field observations, indicating the reliability of HYDRUS-1D in soils irrigated with GW and RW. The regional prediction results of the proposed simulation model indicated that the average soil ECe at the bottom of vadose zones ranged from 0.400 to 0.896 dS m⁻¹, and the values in the Tongzhou and Daxing Districts irrigated with RW were 1.40 and 1.09 times, respectively, higher than that irrigated with GW over the next 50 years. Five risk indicators represent salt transporting time and values were used. The results of the proposed evaluation model showed that the risk scores ranged from 3.04 to 9.32. In the Tongzhou and Daxing Districts, the risk scores of RW irrigation for polluting groundwater were 1.06 and 1.08 times, respectively, higher than that GW irrigation. The risk scores of GW or RW irrigation for polluting groundwater in the Tongzhou District were 1.75 or 1.72 times, respectively, higher than that in the Daxing District. Considering the small risk difference between GW and RW irrigations, RW can be used in both regions. Due to the different vadose zone structures, the Daxing District is more suitable for RW irrigation. The long-term use of RW for irrigation should consider the salt content of RW and vadose zone structure.

The competitive/simultaneous adsorption of arsenite (As(III)) and arsenate (As(V)) onto ferrihydrite is one of main processes controlling the distribution of arsenic under oxidizing conditions in the natural environment. Adsorption reactions of As(III) and As(V) with ferrihydrite were investigated by employing a combination of batch adsorption experiments and Fourier transform infrared (FTIR) spectroscopy measurements in single and binary systems, i.e., both As species were present at the same time. Isotherm studies showed that the adsorption of As(III) in the binary system was less than that in single system, indicating that As(V) hindered As(III) adsorption. The presence of As(III) had almost no impact on As(V) adsorption at pH 5 in the binary systems. Freundlich model described the equilibrium data well (R ² > 0.94), and the adsorption affinity onto ferrihydrite was in the following order: As(III)-single > As(III)-binary > As(V)-single > As(V)-binary. Kinetic data of As(III) and As(V) from single and binary systems were both well described by pseudo-second-order equation (R ² > 0.98). FTIR showed that after adsorbing of either As species, a new peak occurred at 826 cm⁻¹ due to the formation of Fe-O-As bonds, indicating that competition between As(III) and As(V) could take place on the surface sites as a result of the formation of a similar surface complexes.

In this study, the decolorization of a dye solution via bio-Fenton process with in situ generation of H₂O₂ by enzymatic catalyzed oxidation of glucose was investigated. For this purpose, magnetite was synthesized and was used as the support for glucose oxidase immobilization. The particle size of the magnetite was estimated to be around 42 nm according to the obtained scanning electron microscope images. The magnetite crystal size was obtained approximately 26 nm by X-ray diffraction spectrum. Effective variables on immobilization were investigated. The best immobilization conditions were achieved at pH 6, temperature of 10 °C, glucose oxidase/support ratio of 1800 U/g, and time of 2.5 h. In these conditions, 450 U of glucose oxidase was immobilized per grams of magnetite. The immobilized glucose oxidase was used for the decolorization of acid yellow 12 in batch experiments. Decolorization conditions were optimized by response surface methodology. Four parameters including pH, temperature, glucose, and Fe²⁺ concentrations in five levels were investigated. The optimum conditions were obtained as follows: pH = 4.5, T = 29 °C, initial glucose concentration of 1.5 g/L, and Fe⁺² concentration of 1.4 g/L. Decolorization efficiency after 120 min at optimal conditions in the presence of 0.3 g immobilized enzyme (450 U/g) in 100 cm³ solution was observed to be equal to 62.27 %.

Lead (Pb) has progressively become a widespread contaminant in the environment because of its intensive use and inherent stability. The contamination of Pb in agricultural soils is a major environmental problem. This paper considers the use of weathered coal humic acids for in situ remediation of Pb-contaminated soils. The effectiveness of acid rain on leaching in soil column was investigated. To determine the mobility and availability of Pb, we also investigated the soil pH and available soil Pb content from different depths in addition to the leachate pH and Pb concentrations at different times. Weathered coal has the potential to adjust the soil pH and leachate pH through metal-bridging mechanisms and deprotonation processes. We found that weathered coal humic acid and simulated acid rain significantly decreased the available surface soil Pb concentrations. The decrease in the available Pb concentrations in the surface layers of the soil was related to a significant increase in the available Pb concentrations in the middle layers of the soil. The application of weathered coal humic acid could reduce the Pb concentration of soil leachates. The removal of Pb was efficient, particularly at the 1000-mg-kg⁻¹ Pb pollution level, with a maximum decrease of 85.8 %.

Detecting and separating specific effects of contaminants in a multi-stress field context remain a major challenge in ecotoxicology. In this context, the aim of this study was to assess the usefulness of a non-invasive transcriptomic method, by means of a complementary DNA (cDNA) microarray comprising 1000 candidate genes, on caudal fin clips. Fin gene transcription patterns of European eels (Anguilla anguilla) exposed in the laboratory to cadmium (Cd) or a polychloro-biphenyl (PCBs) mixture but also of wild eels from three sampling sites with differing contamination levels were compared to test whether fin clips may be used to detect and discriminate the exposure to these contaminants. Also, transcriptomic profiles from the liver and caudal fin of eels experimentally exposed to Cd were compared to assess the detection sensitivity of the fin transcriptomic response. A similar number of genes were differentially transcribed in the fin and liver in response to Cd exposure, highlighting the detection sensitivity of fin clips. Moreover, distinct fin transcription profiles were observed in response to Cd or PCB exposure. Finally, the transcription profiles of eels from the most contaminated site clustered with those from laboratory-exposed fish. This study thus highlights the applicability and usefulness of performing gene transcription assays on non-invasive tissue sampling in order to detect the in situ exposure to Cd and PCBs in fish.

The objective of this study was to assess the impact of metal contamination on microbial functional diversity and enzyme activity in forest soils. This study involved the evaluation of the influence of the texture, carbon content and distance to the source of contamination on the change in soil microbial activity, which did not investigate in previous studies. The study area is located in southern Poland near the city of Olkusz around the flotation sedimentation pond of lead and zinc at the Mining and Metallurgical Company “ZGH Bolesław, Inc.”. The central point of the study area was selected as the middle part of the sedimentation pond. The experiment was conducted over a regular 500 × 500-m grid, where 33 sampling points were established. Contents of organic carbon and trace elements (Zn, Pb and Cd), pH and soil texture were investigated. The study included the determination of dehydrogenase and urease activities and microbial functional diversity evaluation based on the community-level physiological profiling approach by Biolog EcoPlate. The greatest reduction in the dehydrogenase and urease activities was observed in light sandy soils with Zn content >220 mg · kg⁻¹ and a Pb content > 100 mg · kg⁻¹. Soils with a higher concentration of fine fraction, despite having the greatest concentrations of metals, were characterized by high rates of Biolog®-derived parameters and a lower reduction of enzyme activity.

We measured the concentrations of dissolved inorganic nitrogen (DIN; nitrate, ammonium, and nitrite) in stream water in a paddy-dominated agricultural basin in a snowfall area from August 2009 to October 2010 to facilitate evaluation of stream water eutrophication from nitrogen during the non-irrigated period. We compared the nitrogen budget in a paddy field between irrigated and non-irrigated periods, from information about nitrogen fertilizer, denitrification, harvested rice, and atmospheric nitrogen deposition. We also estimated stream nitrogen exports from DIN concentrations and stream flow rates. DIN concentrations in stream water were higher during the non-irrigated period (October–March) than during the irrigated period (April–September). Stream flow was also higher during the non-irrigated period (5.9 mm day⁻¹) than during the irrigated period (2.5 mm day⁻¹), which possibly reflects snow melting. Although nitrogen fertilizer was applied during the irrigated period, the amount of nitrogen removed by the rice harvest and denitrification was sufficiently large to reduce nitrogen exports from paddy fields. Atmospheric nitrogen deposition was higher during the non-irrigated period (755 kg N km⁻²) than during the irrigated period (410 kg N km⁻²). DIN exports were also higher in the non-irrigated period (860 kg N km⁻²) than in the irrigated period (120 kg N km⁻²). The higher exports in the non-irrigated period may reflect the lack of nitrogen removal by a rice harvest and denitrification and increased runoff and higher atmospheric nitrogen deposition. Our study highlights the important contribution of the non-irrigated period to nitrogen eutrophication in stream water in this particular environment.