Metals are significant environmental pollutants, and their toxicity is a problem for all living organisms. Indeed, aquatic plants are particularly sensitive to the excess of metal ions. Several researches report that aquatic plants exposed to metal-induced toxicity showed similar responses (e.g. inhibition of growth and induction of oxidative stress). Meanwhile, many studies were involved to counter these toxicities. This paper provides a brief review of the role of the exogenous supply of some compounds in the alleviation or reduction of toxicity in aquatic plants generated by metals. Particular attention is given to the role of polyamine, proline, nitric oxide, glutathione and phytochelatin.

Metal cations could enhance the sorption of tetracyclines but sometimes the effects are negligible. It is still not clear how these metals produce different effects. In this study, the sorption of chlortetracycline (CTC), tetracycline (TC), and oxytetracycline (OTC) was performed in the presence of Cd (II) to reveal the unknown mechanisms with two river sediments. It is found that Cd (II) could enhance the sorption of TCs on sediment SS, while it is negligible on sediment SY. For different tetracyclines, the enhancement effect by Cd (II) was more significant for CTC, while it is inferior for OTC and TC. Sorption isotherms of Cd (II) under strong and weak background electrolyte and pH decrease of sorption solutions indicate specific sorption is major on SY and cation exchange is significant on SS. Consequently, specific sorption is unfavorable for the enhanced sorption of TCs in the presence of Cd (II) because it is not favorable for the sorption of Cd-TCs by complexation and cation exchange. By the theoretical calculations, it is found that the significant enhancement of CTC is due to the higher electron affinity of Cd-CTC complex than the others to the surface groups. In conclusion, TCs sorption will not be affected by Cd (II) on sediments or soils with strong specific sorption characters of Cd (II).

Biosurfactants have been considered as promising candidates for oil spill cleanup as they are generally more biodegradable, less toxic, and better in enhancing biodegradation than chemical surfactants. This study targeted the marine microbial biosurfactants to examine their enhanced production methods and application for the removal of crude oil from soil. The biosurfactants generated by Bacillus subtilis, which was isolated from the Atlantic Ocean, were investigated in this study. The economic production medium using different carbon (n-hexadecane, diesel oil, glycerol, glucose, starch, and sucrose) and nitrogen sources (NaNO₃, (NH₄)₂SO₄, and yeast extract) was studied. The best performance of biosurfactant production was achieved when using glycerol as carbon source and sodium nitrate and yeast extract as nitrogen sources in the substrate. The production rate was enhanced five times compared with that of the original screening recipe. The fermentative production of the generated biosurfactants could reduce the surface tension of water to 27 mN/m and with strong surface activity (∼36.4 mN/m) even after dilution for 10 times. The critical micellar concentration (CMC) of the product was 507 mg/L. A thin layer chromatography (TLC) analysis indicated that the purified product was a mixture of lipopeptide and glycolipid. The microbially produced biosurfactants were further examined as a soil-washing agent to enhance crude oil removal in a soil column system. The removal rates of 58 and 65 % were achieved using the biosurfactant solution with concentrations of 4 and 8 g/L, respectively. The results demonstrated the potential of marine microbial biosurfactants in cleaning crude oil-contaminated soil.

This study aims at investigating heavy metal mobility and bioavailability in sediments from the Mexicana and Jaralito streams, Northern Mexico. A chemical partition analysis (sequential extraction) was performed to determine geochemical phases in which metals are found. Geoaccumulation index (Igeo) and enrichment factor values were obtained from analytical results and geochemical baseline data. Sediments showed high concentrations (mg/kg) of Cd (below detection limit, BDL-3.50), Cr (3–41), Cu (238–1090), Fe (41267–61033), Mn (678–1143), Ni (18–35), Pb (51–124), and Zn (116–356). Metal concentrations in geochemical phases exhibited the following order: residual > interchangeable > Fe/Mn oxide > carbonate >organic matter/sulfide. Both streams presented high degree of enrichment for Cu, Fe, Mn, Ni, Pb, and Zn, indicating anthropic origin of these metals. Metal mobilities in Jaralito and the Mexicana were Fe > Cu > Mn > Pb > Zn > Ni > Cr and Fe > Cu > Mn > Zn > Ni > Pb > Cr > Cd, respectively. Jaralito and the Mexicana sediments exhibit a mostly gravel-sandy texture with higher metal contents than in fine fractions. Sediment Geoaccumulation index values suggest that Jaralito features moderate to strong contamination by Ni, Pb, and Cu, whereas the Mexicana features strong contamination by Cd, Cu, Pb, and moderate contamination by Ni, Pb, and Zn. The quality criteria comparisons (LEL and SEL) indicate these areas are contaminated by metals and represent a substantial environmental risk because of high metal mobility and availability. Future studies on water chemistry and biota are needed to fully assess pollution impact in the Jaralito and Mexicana streams. The probability of adverse biological effects from high metal levels in those streams confirms the urgency of implementing effective environmental management practices.

The operation of modern vehicles requires the introduction of package of fuel additives to ensure the required level of operating characteristics, some of which cannot be achieved by current oil refining methods. The use of additives allows flexibility of impact on the properties of the fuel at minimal cost, increasing the efficiency and environmental safety of vehicles. Among the wide assortment of additives available on the world market, many are surfactants. It has been shown that the introduction of some surfactants into gasoline concurrently reduces losses from gasoline evaporation, improves the mixture formation during injection of gasoline into the engine and improves detergent and anticorrosive properties. The surfactant gasoline additive that provides significant improvement in the quality of gasoline used and environmental and operating characteristics of vehicles has been developed and thoroughly investigated. The results of studies confirming the efficiency of the gasoline additive application are herein presented.

Heavy metal extraction from soils is one of the functions of plants which is widely studied and applied worldwide. However, little is known to what extent medicinal plants can accumulate these metals and cause problems to human health. This study aimed to evaluate the accumulation of heavy metal/loid in plant tissues, nutritional imbalance, and the effect of heavy metal concentrations in soil on the medicinal plants. The experiment was conducted in a factorial scheme with three contaminated soil samples and a soil sample from an uncontaminated field and three medicinal species: Cynara scolymus, Ocimum basilicum, and Rosmarinus officinalis. The heavy metal content in the biomass increased with increasing soil samples concentration. Biomass production, nutritional imbalance by nutrients did not show consistent results according to soil contamination criteria and are not good indicators of heavy metals presence in plant tissues, since they did not allow predicting the presence of metal in the plants, due to the different behavior of elements and plant species. There was a high concentration of Cd, Cr, Pb, and As and micronutrients Fe, Zn, and Cu in the plant tissues, above the limits recommended by the World Health Organization. Therefore, as the components of C. scolymus, O. basilicum, and R. officinaliss are used to prepare teas, condiments, or consumed raw, coupled with the ability of such species to concentrate toxic metals, the continued use of these plant products containing these metals can pose a potential health concern.

The ability of water hyacinth (WH) and pondweed (PW) to accumulate mercury from water in gold mine tailing area was studied. Experiments were carried out in the field conditions without using a model system. An approach for mercury fractionation according to its association with various types of biomolecules (water soluble compounds, oxygen-containing ligands such as polycarboxylic acids and cell wall components) was suggested. It is based on sequential extraction of mercury to recover different compounds according to the binding strength. In all cases for WH and PW, the most portion of mercury is bound to the cell wall (63–67 and 54–64 %, for WH and PW, respectively) that works as a physiological barriers and protects the plants from negative impact of mercury ions. An approach based on the ability of plants to extract elements from tailings drainage waters that are characterized by milder conditions in comparison with strongly acidic waste material was suggested. The highest BCF values (66,500 and 32,700 for WH and PW, respectively) were obtained for plants grown in natural stream. At low levels of mercury in water (C Hgwₐₜₑᵣ = 0.01–0.05 ppb) typical for tailing solutions, translocation of the element from roots to shoots decreases as concentration of mercury in WH increases. PW is preferable to use in practice for tailings remediation from mercury contamination since it does not require cultivation in a greenhouse and shows BCF values comparable with WH.

Chitosan-montmorillonite composite was extensively used for the removal of heavy metals from wastewater. In wastewater, copper (Cu²⁺) usually coexist with the organic ligands, which had unknown effect on Cu²⁺ adsorption by the composite materials. In order to understand further on that, the adsorption of copper by the composite materials must be studied. In the present study, montmorillonite was coated with chitosan, and X-ray diffraction (XRD) patterns of the composite proved the intercalation of chitosan in the montmorillonite. Fourier transform infrared (FTIR) spectra of the composite identified the presence of amino group on the composite, and that of the composite saturated with metals identified the interaction between the amino groups and metals. Langmuir adsorption isotherm indicated that the composite had more capacity to adsorb Cu²⁺ from wastewater than montmorillonite. The adsorption capacity of Cu²⁺ by montmorillonite and chitosan-montmorillonite composite was studied, respectively, as a function of pH and in the presence of acetate. Compared to the montmorillonite at low ligand concentration (0.08 mmol/L) or low pH (<4.0), the coexisting acetate increased more Cu²⁺ adsorption by the composite. The acetate ligand presented less depression on the adsorption by the composite than that by montmorillonite at high ligand concentration (4 mmol/L) or high pH (>4.5). Therefore, the composite is more suitable for removing Cu²⁺ than montmorillonite in acid aqueous medium.

In this study, a cost-effective and easily prepared adsorbent for fluoride removal was synthetized by loading activated aluminum and lanthanum onto hydrothermal palygorskite (HP) (denoted as La-Al-TAP). And the La-Al-TAP was characterized by scanning electron microscope (SEM), x-ray diffraction analysis (XRD), and x-ray photoelectron spectroscopy (XPS). As a result, the optimal condition for La-Al-TAP preparation was proposed as follows: 0.004 mol/L La(III) and 0.125 mol/L Al(OH)₃ colloid was loaded onto the acidulated HP (AP) with volume ratio of AP/La(III)/Al(OH)₃ = 1:6:1, and then La-Al-AP was calcined at 300 °C for 2 h. Results proved that the La-Al-HP adsorbent had a significantly larger surface (95.58 m²/g) than that of raw HP (34.31 m²/g). The amorphous structure provided a favorable site for fluoride adsorption, subsequently improving the adsorption capacity of HP. The results all indicated the formation of oxide La-Al-O composite at the surface of adsorbent. The adsorption of fluoride by adsorbent La-Al-TAP was well fitted to the Langmuir isotherm and the maximum adsorption capacity was up to 1.04 mg/g. It was also found that the adsorbent could be regenerated for such six times with good security performance. In conclusion, the newly prepared La-Al-TAP adsorbent in this study has potential as an excellent adsorbent for fluoride removal in groundwater remediation works.