Silver nanoparticles (AgNPs) have significantly increased in production and use for anti-microbial propose. This agent, after used, is released into sewerage system resulting in possibility to inactivate non-targeted microorganisms in wastewater treatment plants. In this study, the inhibitory effect of AgNPs on ammonia oxidation was investigated using respirometric assay. The initial concentrations of AgNPs and ammonia ranged 0.25–10.00 and 14–280 mg/L, respectively. Half saturation constant (K ₛ) for ammonia oxidation was found to be 15.9 mg N/L. Under the presence of AgNPs, the maximum oxygen uptake rate and K ₛ declined. The effect of AgNPs was proved to follow an uncompetitive-like inhibition kinetic type with the inhibition coefficients (K ᵢ) of 5.5 mg/L. Increasing AgNPs from 0.25 to 10.00 mg/L inhibited 4 to 50 % of ammonia-oxidizing activities at the initial ammonia concentrations from 14 to 280 mg/L. Based on transmission electron microscopic observation, AgNPs could damage the microbial cells. All findings indicated that AgNPs substantially reduced ammonia-oxidizing microorganisms and their activities. Thus, special attention should be made to manage discharge of AgNPs into the environment.

Simulated magnetic contamination of plants during early ontogenetic stages was studied in arranged laboratory conditions using magnetic nanoparticles based on compound metal oxides. Aqueous suspensions of magnetic colloidal nanoparticles of Fe3O4, CoFe2O4, and ZnFe2O4, were administrated to freshly germinated sunflower seeds in the same array of dilutions (v/v): 20–40–60–80–100 μl/l, the results of their genetic impact in the root tip cells being qualitatively and quantitatively analyzed. Cytogenetic tests carried out by optical microscopy means provided data on the types of abnormal cell divisions as well as on the mitosis rate and total percentage of chromosomal aberrations. Considerable diminished mitosis rate was evidenced in all situations, while remarkably enhanced number of chromosomal aberrations was also evidenced for all three cases with higher nanotoxicity revealed in the case of ZnFe2O4 and CoFe2O4. Chromosome fragments, interchromatidian bridges and micronuclei appeared in most analyzed samples with no noticeable difference for one type of magnetic nanoparticles or other.

The adsorption of methylene blue cationic dye by water hyacinth root was studied in a batch system. The experimental data isotherms were analyzed using the Langmuir and Freundlich equations. The monolayer adsorption capacity for methylene blue dye was found as 0.187 kg kg−1. Three kinetic models (the pseudo-first order, the pseudo-second order, and the unified approach) were used to calculate the adsorption rate constants. The kinetic data along with equilibrium constants (maximum monolayer capacity and Langmuir constant) fitted well with unified approach model for different initial concentrations, and the rate constants were determined. Laboratory column experiments were conducted to evaluate the performance of water hyacinth root for methylene blue sorption under dynamic flow conditions. Breakthrough curves were plotted for the methylene blue adsorption on the adsorbent using continuous flow column operation by varying the bed height (0.06–0.12 m) and the feed concentrations (0.1–0.2 kg m−3). Different column design parameters, such as depth of exchange zone, adsorption rate, and adsorption capacity, were calculated. At the end, an attempt has also been made to model the data generated from column studies using the empirical relationship based on Bohart–Adams model.

Agricultural runoff containing nitrogen fertilizer is a major contributor to eutrophication in aquatic systems. One method of decreasing amounts of nitrogen entering rivers or lakes is the transport of runoff through vegetated drainage ditches. Vegetated drainage ditches can enhance the mitigation of nutrients from runoff; however, the efficiency of nitrogen removal can vary between plant species. The efficiency of three aquatic macrophytes, cutgrass (Leersia oryzoides), cattail (Typha latifolia), and bur-reed (Sparganium americanum), to mitigate dissolved and total nitrogen from water was investigated. Replicate mesocosms of each plant species were exposed to flowing water enriched with ammonium and nitrate for 6 h, allowed to remain stagnant for 42 h, and then flushed with non-enriched water for an additional 6 h to simulate a second storm event. After termination of the final simulated runoff, all vegetated treatments lowered total nitrogen loads exiting mesocosms by greater than 50%, significantly more than unvegetated controls, which only decreased concentrations by 26.9% (p ≤ 0.0023). L. oryzoides and T. latifolia were more efficient at lowering dissolved nitrogen, decreasing ammonium by 42 ± 9% and 59 ± 4% and nitrate by 67 ± 6% and 64 ± 7%, respectively. All treatments decreased ammonium and nitrate concentrations within mesocosms by more than 86% after 1 week. However, T. latifolia and L. oryzoides absorbed nitrogen more rapidly, lowering concentrations by greater than 98% within 48 h. By determining the nitrogen mitigation efficiency of different vegetative species, plant communities in agricultural drainage ditches can be managed to significantly increase their remediation potential.

Constanta harbor has been contaminated for decades with petroleum and petroleum products, which contain different toxic organic solvents. A novel solvent-tolerant bacterium, Vibrio alginolyticus IBBCₜ₂ was isolated from a seawater sample (Constanta harbor). Alkanes (i.e., n-hexane, n-decane, cyclohexane) with logarithm of partition coefficient in n-octanol and water (log P OW ) > 3.35, were less toxic for V. alginolyticus strain IBBCₜ₂, compared with aromatics (i.e., toluene, m-xylene, ethylbenzene) with log P OW < 3.17. The high organic solvent resistance of V. alginolyticus IBBCₜ₂ could be due to the presence of some catabolic (alkB, alkB/alkB1, todC1, xylM, C23DO) and transporter (HAE1, acrAB) genes. The adaptation mechanisms, underlying cyclohexane, n-hexane, n-decane, toluene, m-xylene, and ethylbenzene resistance in V. alginolyticus IBBCₜ₂ showed a complex response of cells 60 min after solvent shock (i.e., modifications of the cell viability, changes in the membrane’s lipid and protein profile, modifications of the genomic fingerprinting). Exposure of V. alginolyticus IBBCₜ₂ cells to salt stress decreases the organic solvents tolerance of this bacterium.

The soil dynamics of hexavalent Cr, a particularly mobile and toxic metal, is of a great environmental concern, and its availability to plants depends on various soil properties including soil organic matter. Thus, in a pot experiment, we added 50 mg Cr(VI) kg⁻¹ soil and studied Cr(VI) soil extractability and availability to spinach, where we applied both natural (zeolite), synthetic adsorptive materials (goethite and zeolite/goethite) and organic matter with farmyard manure. We found that, compared to the unamended control plants, dry matter weight in the Cr(VI)-added soil was greatly decreased to 17 % of the control, and height was decreased to 34 % of the control, an indication of Cr toxicity. Also, exchangeable Cr(VI) levels in soil decreased back to the unamended control even in the first soil sampling time. This was much faster than the exchangeable Cr(VI) levels in the mineral-added soil, where Cr(VI) levels were decreased to the levels of the unamended control in the third sampling time. The positive effect of organic matter was also indicated in the Cr quantity soil-to-plant transfer coefficient (in grams of Cr in plant per kilogram of Cr added in soil), a phyto-extraction index, which was significantly higher in the manure-amended (1.111 g kg⁻¹) than in the mineral-added treatments (0.568 g kg⁻¹). Our findings show that organic matter eliminates the toxicity of added Cr(VI) faster than the mineral phases do and enhances the ability of spinach to extract from soil greater quantities of Cr(VI) compared to mineral-added soils.

The behavior of estrone (E1) and 17β-estradiol (E2) in relatively closed water environment was studied by continuous flow experiment using sediments from a freshwater reservoir. For this, four sediment columns (two oxic ones and two anoxic ones) were employed, which were structured by packing 30 cm of undisturbed sediment and 60 cm of overlying water collected from two sites within a reservoir. A mass balance model that considered the influent flux, the effluent flux, mass transfer, sorption, and biodegradation was proposed to describe the behavior of E2 and E1 in the columns. The results indicated that the water–sediment partition coefficient of E1 [Formula: see text] was higher than E2 [Formula: see text]. The degradation rate of E1 (k E1) was smaller than E2 (k E2). Under both oxic and anoxic conditions, E1 was formed from E2. Furthermore, to clarify the impact of the model parameters such as the hydraulic retention time (HRT), K d, and k on the behavior of E2 and E1, variance analysis was performed based on the results of model simulations. The results showed that the concentrations of E2 and E1 in the column effluent were controlled most significantly by the sorption capacity of the natural estrogens onto sediment particles, with the determined contributory ratios changing in the order of sorption > HRT > degradation.

Studies concerning competitive sorption of anions on oxidic materials eligible to be used as soil amendments are crucial for a better understanding of the adsorbent’s effectiveness and ion mobility/availability in the environment. This study evaluated mono-/multi-element adsorption of phosphate and arsenate on aluminum (AMB) and iron mining by-products (IMB; used for comparison) and measured the effect of pH and thermal pretreatments on P and As adsorption on AMB and IMB. We also evaluated whether the desorption of As previously adsorbed on AMB and IMB increases with the addition of increasing doses of P. For adsorption, each adsorbent was reacted at selected pHs with solutions containing As and P individually or in combination. Non-competitive desorption was performed with 30 mmol L⁻¹ NaCl. Arsenate displacement was evaluated by reaction of the adsorbents containing previously adsorbed As with P-containing solutions. The competition between P and As decreased the adsorption of these anions by 2.7 and 23.2 %, respectively. Increasing pH decreased adsorption of both As and P, whereas the thermal pretreatment increased P adsorption by 40 % and As adsorption by 15 %. Phosphate in solution increased As desorption, with each millimoles per kilogram of adsorbed P desorbing as much as 2.3 ± 1.1 mmol kg⁻¹ of As.

The objectives of this study were to characterize and map the spatial distribution of As, Cd, Cu, Pb, and Zn in topsoil at Rayong Province, a rapidly developing city, and to evaluate the associated health risks. A total of 130 soil samples were collected by a stratified random sampling technique. The soil samples were digested by HNO₃, HCl and H₂O₂, and heavy metals were determined by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Descriptive statistics and geostatistics were used to analyze the data, and the kriging method was used for data interpolation. The results show that the mean values of most heavy metals in the soil, except for As, were lower than Thailand's soil quality standard for habitat and agriculture purposes and the worldwide background level. Highly significant correlations were found for As/Cd, As/Cu, As/Pb, As/Zn, Cd/Cu, Cd/Pb, Cd/Zn, Cu/Pb, Cu/Zn, and Pb/Zn. In addition, most heavy metals showed significantly positive correlations with the reference element (Fe). Spherical, Gaussian and exponential models were selected for the semivariogram analysis of the heavy metals in the Rayong soil. As, Cd, Cu, and Pb were fitted with the spherical model, and Zn was fitted with the exponential model. The total hazard index (HIs) from the heavy metals in the Rayong soil found in both children and adults were in the order of As > Pb > Cu > Cd > Zn. The hazard index of As in the children was higher than 1. The major health risk areas are mainly located in the eastern part of the study area where the land is used for agriculture and in the southwestern areas where industrial activities take place.

This work aims to identify and characterize heavy metal contamination in a fluvial system from Cartagena–La Unión mining district (SE Spain). In order to assess the dynamics of transport and the accumulation of heavy metals, sediments, surface water and vegetation, samples along “El Avenque” stream were collected. The former direct dumps of wastes and the presence of tailing ponds adjacent to the watercourse have contributed to the total contamination of the stream. Total Cd (103 mg kg−1), Cu (259 mg kg−1), Pb (26,786 mg kg−1) and Zn (9,312 mg kg−1) in sediments were above the limits of European legislation, being highest where tailing ponds are located. Bioavailable metals were high (3.55 mg Cd kg−1, 6.45 mg Cu kg−1, 4,200 mg Pb kg−1 and 343 mg Zn kg−1) and followed the same trend than total contents. Metals in water were higher in sampling points close to ponds, exceeding World Health Organization guidelines for water quality. There is a direct effect of solubilisation of sediment metals in water with high contents of SO 4 2− , product of the oxidation of original sulphides. The mobility of metals varied significantly with shifts in pH. Downstream, available and soluble metals concentrations decreased mainly due to precipitation by increments in pH. As a general pattern, no metal was bioaccumulated by any tested plant. Thus, native vegetation has adopted physiological mechanisms not to accumulate metals. This information allows the understanding of the effect of mining activities on stream contamination, enforcing the immediate intervention to reduce risks related to metals’ mobility.