Co-application of titanium nanoparticles and melatonin effectively lowered chromium toxicity in lemon balm (Melissa officinalis L.) through modifying biochemical characteristics.

Chromium (Cr) toxicity can negatively affect plant growth and development, impacting agricultural productivity and posing risks to human health. Metallic nanoparticles (MNPs) such as titanium dioxide (TiO2) and natural growth regulators such as melatonin (MT) become a promising technology to manage heavy metal-contaminated soils and promote safe food production. The present work was conducted to find the effect of foliar application of TiO2 NPs (15 mg L-1) and MT (100 µM) on growth, biochemical attributes, and Cr accumulation in plant tissues of Melissa officinalis L. under Cr toxicity (50 and 100 mg Cr kg-1 soil). The results showed that Cr toxicity led to decreased plant performance, where 100 mg Cr kg-1 soil led to notable decreases in shoot weight (28%), root weight (27%), essential oil (EO) yield (34%), chlorophyll (Chl) a + b (33%), while increased malondialdehyde (MDA, 30%), superoxide dismutase (SOD) activity (51%), and catalase (CAT) activity (122%). The use of TiO2 NPs and MT, particularly their co-application, remarkably reduced Cr toxicity by enhancing plant weight, Chl content, and lowered MDA and antioxidant activity. Total phenolic content (TPC), total flavonoid content (TFC), EO percentage, and rosmarinic acid in plants treated with Cr at 50 mg Cr kg-1 soil and co-application of TiO2 NPs and MT were relatively higher than in other treatments. Under 100 mg Cr kg-1 soil, the synergic effect of TiO2 NPs and MT-enhanced rosmarinic acid content (22%) but lowered Cr accumulation in roots (51%) and shoots (72%). Heat map analysis showed that CAT, SOD, MDA, and EO yield had the maximum variability under Cr, TiO2 NPs, and MT. Exogenous TiO2 NPs and MT can be recommended to modulate Cr toxicity in lemon balm under soil Cr toxicity.

ZnO nanoparticles mediated by Azadirachta indica as nano fertilizer: Improvement in physiological and biochemical indices of Zea mays grown in Cr-contaminated soil.

The current investigation aimed at evaluating the impact of Azadirachta indica-mediated zinc oxide nanoparticles (Ai-ZnONPs) on the growth and biochemical characteristics of maize (sweet glutinous 3000) under exposure to 50 mg kg-1Ai-ZnONPs with Cr (VI) concentrations of 50 and 100 mg kg-1. The results indicate that plants exposed to Cr (VI) only experienced a decline in growth parameters. Conversely, the inclusion of Ai-ZnONPs caused a noteworthy increase in physiological traits. Specifically, shoot and root fresh weight increased by 28.02% and 16.51%, and 63.11% and 97.91%, respectively, when compared to Cr-50 and 100 treatments. Additionally, the SPAD chlorophyll of the shoot increased by 91.08% and 15.38% compared to Cr-50 and 100 treatments, respectively. Moreover, the antioxidant enzyme traits of plant shoot and root, such as superoxide dismutase (SOD 7.44% and 2.70%, and 4.45% and 3.53%), catalase (CAT 1.18% and 3.20%, and 5.03% and 5.78%), and peroxidase (POD 0.31% and 5.55%, and 4.72% and 3.61%), exhibited significant increases in Cr 50 and 100 treatments, respectively. The addition of Ai-ZnONPs to the soil also enhanced soil nutrient status and reduced Cr (VI) concentrations by 40.69% and 19.82% compared to Cr-50 and 100 treated soils. These findings suggest that Ai-ZnONPs can trigger the activation of biochemical pathways that enable biomass accumulation in meristematic cells. Further investigations are required to elucidate the mechanisms involved in growth promotion.

Development of a Sensitive SERS Method for Label-Free Detection of Hexavalent Chromium in Tea Using Carbimazole Redox Reaction.

Tea plants absorb chromium-contaminated soil and water and accumulate in tea leaves. Hexavalent chromium (Cr6+) is a very toxic heavy metal; excessive intake of tea containing Cr6+ can cause serious harm to human health. A reliable and sensitive surface-enhanced Raman spectroscopy (SERS) method was developed using Au@Ag nanoparticles as an enhanced substrate for the determination of Cr6+ in tea. The Au@AgNPs coated with carbimazole showed a highly selective reaction to Cr6+ in tea samples through a redox reaction between Cr6+ and carbimazole. The Cr6+ in the contaminated tea sample reacted with methimazole-the hydrolysate of carbimazole-to form disulfide, which led to the decrease in the Raman intensity of the peak at 595 cm-1. The logarithm of the concentration of Cr6+ has a linear relationship with the Raman intensity at the characteristic peak and showed a limit of detection of 0.945 mg/kg for the tea sample. The carbimazole functionalized Au@AgNPs showed high selectivity in analyzing Cr6+ in tea samples, even in the presence of other metal ions. The SERS detection technique established in this study also showed comparable results with the standard ICP-MS method, indicating the applicability of the established technique in practical applications.

Effects of abiotic mineral transformation of FeS on the dynamic immobilization of Cr(VI) in oxic aquatic environments.

Iron sulfide (FeS) can reductively convert soluble Cr(VI) into insoluble Cr(III) under anoxic conditions. However, the fate and transformation of FeS and the stability of immobilized Cr under various oxic environmental conditions are poorly understood. The results show that FeS transforms into pyrrhotite and pyrite intermediates principally and finally lepidocrocite and elemental sulfur, accordingly accounting for 66.1% and 33.9%. Temperature, fulvic acid as natural organic matter and coexisted ions of nitrate, bicarbonate, and calcium affect the evolution of FeS insignificantly. Transformation of FeS involves surface-mediated oxidation of FeS solids, and minor proton-promoted dissolution and oxidation, accompanying synergistic oxidation of Fe(II) and S(-II). Cr(VI) removal performances of oxygenated FeS with increasing duration showed a rise-fall trend. Reduction dominates Cr(VI) uptake first and finally, sorption prevails with the gradual FeS oxygenation. Cr(VI) removal correlates linearly with Cr(VI) reduction, and the reduced Cr species can be predicted based on the known Cr(VI) removal performance. As the FeS oxygenation time increases, newly generated pyrite improves Cr(VI) reduction and removal, and then a decreasing ability to reduce Cr(VI) causes a drop in Cr(VI) removal. These findings provide new insight into the oxidative transformation of FeS in oxic aquatic environments and its impact on Cr(VI) levels.

Perception and legacy of soil chromium and lead contamination in an operational small-scale coal mining community.

Operational small-scale coal mining (OSCM) is one of the most significant sources of chromium (Cr) and lead (Pb) pollution in Bangladesh. Attempts to minimize or lessen the use of Cr and Pb in OSCM have shown unsatisfactory results, mainly because they need to address the sociotechnical complexity of pollution concerns in OSCM. This research adopts a multidisciplinary, sociotechnical approach to addressing Cr and Pb problems, coupling soil sampling for Cr and Pb with questionnaires of miners' and inhabitants' perceptions of pollution and its distribution. The study was undertaken in the Barapukuria coal basin in northwest Bangladesh. Except for mining areas (average of 49.80 ± 27.25 mg/kg), Cr levels in soils exceeded the world average in the periphery (73.34 ± 24.39 mg/kg, ~ 1.2 times) and residential areas (88.85 ± 35.87 mg/kg, 1.5 times the world standard of 59.5 mg/kg). Pb levels in soils exceeded national and global averages in mining (53.56 ± 37.62 mg/kg, ~ 1.9 times), periphery (35.05 ± 21.77 mg/kg, ~ 1.3 times), and residential areas (32.14 ± 26.59 mg/kg, ~ 1.2 times) when compared to Bangladesh and global standards of 20 and 27 mg/kg. Pb levels were highest in mining areas, while Cr concentrations were highest in residential areas. The questionnaire findings indicated that miners and inhabitants did not correctly assume that the highest levels of Cr and Pb pollution would be found in these areas. Among all respondents, 54% are unaware of the health impacts of prolonged Cr and Pb exposure. They face respiratory problems (38.6%), skin diseases (32.7%), and other health issues. A large number of people (66.6%) agreed with the fact that Cr and Pb contamination has an impact on drinking water. Cr and Pb pollution has caused 40% crop loss and a 36% decrease in productivity in the agricultural sector. However, respondents underestimated the level of Cr pollution in mining areas, and most assumed that only individuals working directly with mines were impacted by the Cr and Pb content. Participants also rated the reduction of Cr and Pb contamination as of low importance. There is less awareness of Cr and Pb pollution among miners and inhabitants. Sincere efforts to reduce Cr and Pb pollution will likely be met with extra attention and hostility.

Response of microbial community structure to chromium contamination in Panax ginseng-growing soil.

Chromium (Cr) contamination in soil poses a serious security risk for the development of medicine and food with ginseng as the raw material. Microbiome are critical players in the functioning and service of soil ecosystems, but their feedback to Cr-contaminated ginseng growth is still poorly understood. To study this hypothesis, we evaluated the effects of microbiome and different Cr exposure on the soil microbial community using Illumina HiSeq high-throughput sequencing. Our results indicated that 2467 OTUs and 1785 OTUs were obtained in 16S and ITS1 based on 97% sequence similarity, respectively. Bacterial and fungal diversity were affected significantly in Cr-contaminated soil. Besides, Cr contamination significantly changed the composition of the soil bacterial and fungal communities, and some biomarkers were identified in the different classification level of the different Cr-contaminated treatments using LEfSe. Finally, a heatmap of Spearman's rank correlation coefficients and canonical discriminant analysis (CDA) indicated that Chloroflexi, Gemmatimonadetes, Acidobacteria, Verrucomicobia, and Parcubacteria in phylum level and Acidimicrobiia, Gemmatimonadetes, and Deltaproteobacteria in class level were positively correlated with AK, AP, and NO3--N (p < 0.05 or p < 0.01), but negatively correlated with total Cr and available Cr (p < 0.05 or p < 0.01). Similarly, in the fungal community, Tubaria, Mortierellaceae, and Rhizophagus in the phylum level and Glomeromycetes, Agaricomycetes, and Exobasidiomycetes in the class level were positively correlated with AK, AP, and NO3--N (p < 0.05 or p < 0.01), but negatively correlated with total Cr and available Cr (p < 0.05 or p < 0.01). Our findings provide new insight into the effects of Cr contamination on the microbial communities in ginseng-growing soil.

Chromium contamination in paddy soil-rice systems and associated human health risks in Pakistan.

Chromium (Cr) contamination in paddy soil-rice systems threatens human health through the food chain. This study used a new dataset of 500 paddy soil and plant tissue samples collected in the rice-growing regions of Sindh and Punjab Provinces of Pakistan. Overall, 97.4% of grain samples exceeded the Cr threshold values of 1.0 mg kg-1, determined by the China National Food Standard (CNFS). The Cr in paddy soil, 62.6% samples exceeding the China natural background threshold value (90 mg kg-1) for Cr concentration in paddy soil, and lower than the (pH-dependant > 7.5 threshold value for Cr 350 mg kg-1) as determined by China Environmental Quality Standards (EQSs) for paddy soil (GB15618-2018). Geographically weighted regression (GWR) modelling showed spatially nonstationary correlations, confirming the heterogeneous relationship between dependent (rice grain Cr) and independent paddy soil (pH, SOM, and paddy soil Cr) and plant tissue variables (shoot Cr and root Cr) throughout the study area. The GWR model was then used to determine the critical threshold (CT) for the measured Cr concentrations in the paddy soil system. Overall, 38.4% of paddy soil samples exceeding CT values confirm that the paddy soil Cr risk prevails in the study area. Furthermore, the GWR model was applied to assess the loading capacity (LC), the difference between the CT, and the actual concentration of Cr in paddy soil. Loading capacity identified potential paddy soil Cr pollution risk to rice grain and assessed the risk areas. Overall LC% of samples paddy soil Cr risk areas grade: low-risk grade I (34.6%); moderate-risk grade II (15.8%); high-risk grade III (11.2%); and very high-risk grade IV (38.4%) have been assessed in the study area. The human health index, total hazard quotient (THQ ≪ 1), indicates no potential health risk originating from Cr exposure to the population. However, the excess Cr level in paddy soil and rice grain is still a concern. The current study's results are also valuable for the national decision-making process regarding Cr contamination in the paddy soil-rice system.

Source identification of chromium in the sediments of the Xiaoqing River and Laizhou Bay: A chromium stable isotope perspective.

Hexavalent chromium, Cr(VI), is a heavy metal contaminant and the reduction of Cr(VI) is accompanied by large isotopic fractionation. In this study, the sources of Cr were explored using the Cr isotopic composition of sediments from the Xiaoqing River, a heavily polluted river located in the Shandong Province of China, which flows into Laizhou Bay. The results show that δ53Cr values of the sediments are the highest upstream near the pollution source, and gradually decrease along the river toward the range for igneous reservoirs observed near the estuary. Based on the calculation of authigenic Cr isotopic composition (δ53Crauth) using the detrital index and leaching experiments, we suggest that the authigenic Cr in the sample near the pollution source with the highest δ53Crauth value mainly comes from the reduction of Cr(VI) discharged by anthropogenic activity, and authigenic Cr in other samples in the midstream with δ53Crauth values slightly higher than the range of igneous reservoirs may come from natural oxidative Cr weathering products. By introducing a Rayleigh model, we calculate that at least 31%-55% of Cr(VI) in the river water had been reduced to Cr(III) near the pollution source. Due to the self-purification ability of the river, Cr(VI) was reduced; thus, there is no record of high δ53Crauth values in the downstream of the Xiaoqing River and Laizhou Bay, indicating no obvious Cr pollution in these locations. The limited variation of δ53Cr values for samples from a sediment core in Laizhou Bay is also indicative of no obvious Cr pollution in the history. The Cr isotopic compositions of the river sediments are useful for the identification of Cr sources and can be used to advise environmental remediation on Cr pollution.

Biofilm-Templated Heteroatom-Doped Carbon-Palladium Nanocomposite Catalyst for Hexavalent Chromium Reduction.

In this study, we report an interdisciplinary and novel strategy toward biofilm engineering for the development of a biofilm-templated heteroatom-doped catalytic system through bioreduction and biofilm matrix-facilitated immobilization of the in situ-formed catalytic nanoparticles followed by controlled pyrolysis. We showed that (i) even under room temperature and bulk aerobic conditions, Shewanella oneidensis MR-1 biofilms reduced Pd(II) to form Pd(0) nanocrystals (∼10 to 20 nm) that were immobilized in the biofilm matrix and in cellular membranes, (ii) the MR-1 biofilms with the immobilized Pd(0) nanocrystals exhibited nanocatalytic activity, (iii) exposure to Pd(II) greatly increased the rate of cell detachment from the biofilm and posed a risk of biofilm dispersal, (iv) controlled pyrolysis (carbonization) of the biofilm led to the formation of a stable heteroatom-doped carbon-palladium (C-Pd) nanocomposite catalyst, and (v) the biofilm-templated C-Pd nanocomposite catalyst exhibited a high Cr(VI) reduction activity and maintained a high reduction rate over multiple catalytic cycles. Considering that bacteria are capable of synthesizing a wide range of metal and metalloid nanoparticles, the biofilm-templated approach for the fabrication of the catalytic C-Pd nanocomposite we have demonstrated here should prove to be widely applicable for the production of different nanocomposites that are of importance to various environmental applications.

The applicability of compost, zeolite and calcium oxide in assisted remediation of acidic soil contaminated with Cr(III) and Cr(VI).

The effect of soil amendments, i.e., compost, zeolite, and calcium oxide, on the chemical properties of soil contaminated with Cr(III) and Cr(VI) and the uptake of selected heavy metals by spring barley (Hordeum vulgare L.) and maize (Zea mays L.) was determined in a pot experiment. The content of all investigated heavy metals in the tested plants varied significantly in response to the tested soil amendments and increasing concentrations of Cr(III) and Cr(VI). Compost, zeolite, and calcium oxide contributed to an increase in the average yield of the aerial parts of maize plants only in treatments contaminated with Cr(III). The concentrations of Cr, Zn, and Ni in the aerial parts of spring barley and maize were higher in treatments contaminated with Cr(III) than in treatments contaminated with Cr(VI). Calcium oxide induced a significant increase in soil pH relative to the control treatment. In treatments without soil amendments, the average Cr content of soil was higher in pots contaminated with Cr(VI). The concentrations of Zn and Cu in non-amended treatments were negatively correlated with increasing doses of Cr(III) and Cr(VI). Calcium oxide decreased the average content of Cr, Cu, and Ni in all experimental variants. Compost increased the average content of Zn in treatments contaminated with Cr(III) and Cr(IV) relative to non-amended soil.

[Adsorption and Photocatalytic Removal of Chromium on High-index TiO2 Facet].

Chromium (Cr) contamination caused by industrial manufacturing poses a severe challenge in the environment. Titanium dioxide (TiO2) has potential application in Cr removal due to its adsorption and photocatalytic performance. High-index TiO2 with exposed {201} facet was synthesized using the solvothermal method and characterized by SEM, TEM, XRD, and XPS. The adsorption of Cr(Ⅲ/Ⅵ) and photocatalytic reduction of Cr(Ⅵ) on TiO2{201} was examined for the removal from water. The synthesized TiO2{201} was constructed by a dandelion-like hierarchical structure. The adsorption isotherms of Cr(Ⅲ) and Cr(Ⅵ) on TiO2{201} conformed to the Langmuir model, with maximum adsorption capacities of 22.7 mg·g-1 and 13.2 mg·g-1, respectively. The best fitted results from the Freundlich model show that the adsorption of Cr(Ⅲ) and Cr(Ⅵ) on TiO2{201} were favorable with the parameter of 1/n less than 0.5. The results of photocatalytic reduction show that TiO2{201} can reduce Cr(Ⅵ) to Cr(Ⅲ) under UV irradiation, and Cr(Ⅲ) was further precipitated on the surface of TiO2 in the form of Cr(OH)3 and Cr2O3, which was evidenced by XPS characterization. To explore the mechanism of photocatalytic reduction of Cr(Ⅵ), the effect of scavengers for photogenerated holes (EDTA-2Na) and electrons (KBrO3) on Cr(Ⅵ) reduction was studied, and the results suggested that photogenerated electrons were the main reductant.

Remediation of hexavalent chromium in contaminated soil by Fe(II)-Al layered double hydroxide.

In this study, high-efficiency and low-cost Fe(II) and Al(III) layered double hydroxide (Fe-Al-LDH) was synthesized and used for the remediation of Cr(VI) contaminated soil. The Fe-Al-LDH characteristics were analyzed with different techniques. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses revealed its highly crystalline structure with sheet morphology, and a Brunauer-Emmett-Teller (BET) surface area of 46.85 m2/g. In addition, the remediation tests indicated that adding 1 g/L of Fe-Al-LDH to a solution of Cr(VI)-contaminated soil, at a soil to solution ratio of 1 g: 5 mL, completely immobilized the pre-adsorbed Cr(VI) in the soil (2079.84 mg/kg). Additionally, the Fe-Al-LDH could be used in a wide range of pH conditions and no Cr(VI) was detected in the leaching solution. Based on the characterization of X-Ray Diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and X-ray photoelectron spectroscopy (XPS) analysis, it is proposed that adsorption and reduction may be involved in the mechanism of Cr(VI) immobilization by Fe-Al-LDH. At the beginning of the reaction, Cr(VI) entered the layer structure of the LDH or was adsorbed on the surface of the LDH. Then, Fe(II) was involved in reducing the Cr(VI) to Cr(III) and was oxidized to Fe(III). Part of the Cr(VI) and Cr(III) were co-precipitated with Fe(III) and Al (III) during the formation of iron oxide or hydroxide.

Microbial interactions with chromium: basic biological processes and applications in environmental biotechnology.

Chromium (Cr) is a highly toxic metal for microorganisms as well as plants and animal cells. Due to its widespread industrial use, Cr has become a serious pollutant in diverse environmental settings. The hexavalent form of the metal, Cr(VI), is considered a more toxic species than the relatively innocuous and less mobile Cr(III) form. The study of the interactions between microorganisms and Cr has been helpful to unravel the mechanisms allowing organisms to survive in the presence of high concentrations of Cr(VI) and to detoxify and remove the oxyanion. Various mechanisms of interactions with Cr have been identified in diverse species of bacteria and fungi, including biosorption, bioaccumulation, reduction of Cr(VI) to Cr(III), and chromate efflux. Some of these systems have been proposed as potential biotechnological tools for the bioremediation of Cr pollution using bioreactors or by in situ treatments. In this review, the interactions of microorganisms with Cr are summarised, emphasising the importance of new research avenues using advanced methodologies, including proteomic, transcriptomic, and metabolomic analyses, as well as the use of techniques based on X-ray absorption spectroscopy and electron paramagnetic resonance spectroscopy.

Elemental distribution of metals in urban river sediments near an industrial effluent source.

To study the compositional trends associated with the spatial and layer wise distribution of heavy metals as well as the sediment response towards the untreated chemical wastes, we have analyzed river (Buriganga, Bangladesh) sediments by instrumental neutron activation analysis (INAA) and energy dispersive X-ray fluorescence (EDXRF). In nine sediment samples 27 elements were determined where Na, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Zn, As, Rb, Cs, La, Ce, Sm, Dy, Hf, Th and U were determined by INAA and Cu, Sr, Ba, Hg and Pb were determined by EDXRF. Pollution level and the origin of pollutants were evaluated by the aid of geo-accumulation index (Igeo), enrichment factor (EF), pollution load index (PLI) and the inter-element correlation analysis. Major elements are somehow buffered even though the pollution level is severe while the trace metals seem to be highly responsive. Among the heavy metals, Cr is the dominant pollutant, though the pollution level varies systematically with the sampling depth and the distance from the contamination source. Positive linear correlation between Cr and Zn (0.94) ensures the similar anthropogenic source(s) for these two metals, but the sediments of this study respond differently depending upon their geochemical behavior. Rare earth elements (here La, Ce, Sm and Dy), Th and U seem to have crustal origin and the Th/U ratio varies from 2.58 to 4.96.

Evaluation of the chromium contamination at Ribeirão dos Bagres, Franca (SP), Brazil, by the ²¹°Pb method.

This paper presents a chronological study focusing the use of ²¹°Pb in four sediment cores collected at Ribeirão dos Bagres in the region of Franca, São Paulo State, Brazil. When evaluating the sedimentation rate by using the ²¹°Pb method, it was possible to monitor historical changes occurring in the concentrations of chromium present in the sediments. In order to do so, several specific parameters were determined in sediments, as chromium concentration, major oxides, organic matter, grain size, and chemical and physical-chemical parameters of waters. The sediments possessed a Cr concentration range of 0.83-26.25mg/kg that is below the world's average of shales. The sedimentation rates obtained from the ²¹°Pb analysis were between 0.07 and 0.77 g cm⁻²year⁻¹, while the linear sedimentation rate was from 0.6 to 3.2 cm/year. The adoption of the CIC (Constant Initial Concentration) ²¹°Pb model allowed characterize older sediments, aged 177 years, and younger sediments, aged 4 years. The organic matter in the sediments was more abundant in the first few centimeters of practically all profiles, and the analysis of oxides showed that silica is the major constituent of the sediments, in which there is predominance of sand and silt. In addition, the analysis of the physical and chemical parameters of waters indicated that they are suitable for navigation and natural harmony landscape.

Assessment of Tri- and Hexavalent Chromium Phytotoxicity on Oats (Avena sativa L.) Biomass and Content of Nitrogen Compounds.

The purpose of this study was to determine the effect of soil contamination with tri- and hexavalent chromium and soil application of compost, zeolite, and CaO on the mass of oats and content of nitrogen compounds in different organs of oats. The oats mass and content of nitrogen compounds in the crop depended on the type and dose of chromium and alleviating substances incorporated to soil. In the series without neutralizing substances, Cr(VI), unlike Cr(III), had a negative effect on the growth and development of oats. The highest doses of Cr(VI) and Cr(III) stimulated the accumulation of total nitrogen but depressed the content of N-NO3- in most of organs of oats. Among the substances added to soil in order to alleviate the negative impact of Cr (VI) on the mass of plants, compost had a particularly beneficial effect on the growth and development of oats. The application of compost, zeolite, and CaO to soil had a stronger effect on the content of nitrogen compounds in grain and straw than in roots. Soil enrichment with either of the above substances usually raised the content of nitrogen compounds in oats grain and straw, but decreased it in roots.

Efecto de la asociación alga-bacteria Bostrychia calliptera (Rhodomelaceae) en el porcentaje de remoción de cromo en laboratorio / The effect of chromium removal by Algae-bacteria Bostrychia calliptera (Rhodomelaceae) consortia under laboratory conditions

Water pollution is one of the most important environmental problems worldwide. Recently, biotechnology studies have oriented efforts to study algae-bacterium consortia with the aim to understand the mechanisms to find a possible solution in environmental sciences. This study determined the percentage of chromium removal by the alga-bacterium association exposed to a set of different chromium concentrations under controlled in vitro conditions. Wild plants of Bostrychia calliptera associated with bacterial populations were collected from Dagua River, Pacific coast of Colombia, and were monitored in the laboratory. The trial was conducted with synthetic seawater in bioreactors at two chromium levels: 5 and 10mg/L, and four different experimental treatments: i) algae-bacteria (AB), ii) algae with antibiotic (AA), iii) algal surface sediment, Natural Bacterial Consortium (CBN), and iv) the control without algae or bacteria. The experimental design followed a model of two factors (chromium concentration x combination types) with repeated measures using one factor. The microbial population behavior and the chromium concentration percentage were monitored by using atomic absorption spectroscopy (AAS). According to the data, Algae-bacteria (AB) treatment was the most efficient combination at 10mg/L (87%), whereas the bacterial consortia (CBN) was the most efficient at 5mg/L (62.85%). The results showed significant differences of chromium uptake between algae-bacteria (AB) and natural bacterial consortia (CBN), meaning the importance of those treatments in the chromium removal from coastal waters.

Para determinar el porcentaje de remoción de cromo en la asociación alga-bacteria, se tomaron ejemplares del alga Bostrychia calliptera de pneumatóforos de Avicennia germinans y Rizophora mangle, en la desembocadura del Río Dagua, Pacífico colombiano. El ensayo se realizó in vitro en agua marina sintética a dos concentraciones de cromo 5 y 10mg/L, empleando biorreactores con cuatro tratamientos; i) material Alga-Bacteria (AB), ii) material algal con antibiótico Alga-antibiótico (AA), iii) consorcio bacteriano natural (CBN) y iv) control sin presencia de B. calliptera ni bacteria. Se monitoreó el comportamiento de poblaciones bacterianas y el porcentaje de disminución de cromo mediante AAS (Espectroscopía de absorción atómica). Se obtuvo diferencias significativas entre los tratamientos Alga-bacteria (AB) y el consorcio bacteriano natural (CBN), siendo Alga-bacteria más eficiente a 10mg/L (87%). El consorcio bacteriano natural CBN obtuvo mayor porcentaje de remoción a bajas concentraciones de cromo a 5ppm (62.85%). Los resultados mostraron una interacción positiva entre las bacterias asociadas (CBN) a la superficie del alga roja B. calliptera en su proceso acumulativo de cromo.