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1.
Environ Pollut ; 358: 124537, 2024 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-39002746

RESUMO

Microbially induced carbonate precipitation (MICP) is a promising technique for remediating heavy metal-contaminated soils. However, the effectiveness of MICP in immobilizing Cd in alkaline calcareous soils, especially when applied in agricultural soils, remains unclear. Biochar and magnesium oxide are two environmentally friendly passivating materials, and there are few reports on the combined application of MICP with passivating materials for remediating heavy metal-contaminated soils. Additionally, the number of treatments with MICP cement and the concentration of calcium chloride during the MICP process can both affect the effectiveness of heavy metal immobilization by MICP. Therefore, we conducted MICP and MICP-biochar-magnesium oxide treatments on agricultural soils collected from Baiyin, Gansu Province (pH = 8.62), and analyzed the effects of the number of treatments with cement and the concentration of calcium chloride on the immobilization of Cd by MICP and combined treatments. The results showed that early-stage MICP could immobilize exchangeable cadmium and increase the residual cadmium content, especially with high-concentration calcium chloride MICP treatment. However, in the later stage, soil nitrification and exchange processes led to the dissolution of carbonate-bound cadmium and cadmium activation. The fixing effect of MICP influence whether the MICP-MgO-biochar is superior to the MgO-biochar. Four treatments with cement were more effective than single treatment in MICP-biochar-magnesium oxide treatment, and the MICP-biochar-magnesium oxide treatment with four treatments was the most effective, with passivation rates of 40.7% and 46.6% for exchangeable cadmium and bioavailable cadmium, respectively. However, attention should be paid to the increase in soil salinity. The main mechanism of MICP-magnesium oxide-biochar treatment in immobilizing cadmium was the formation of Cd(OH)2, followed by the formation of cadmium carbonate.

2.
Sci Total Environ ; 917: 170594, 2024 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-38309366

RESUMO

Heavy metal composite pollution is widespread in the surrounding environment of tailings ponds in arid and semi-arid regions, leading to the abandonment of substantial agricultural land. This study investigates the speciation distribution and plant accumulation characteristics of heavy metals in abandoned farmland with different durations of natural aging. The aim is to comprehend the local heavy metal behavior pattern in the soil-plant system and offer insights for environmental remediation. Our findings reveal that Cd stands out as the primary heavy metal pollutant in this area. The mobility ranking of heavy metals is Cd > Pb > Zn > Cu, with Cd and Pb mobility decreasing along the basin. Notably, active Pb exhibits a higher affinity for soil binding compared to other metals. The predominant plant species in the region are primarily small shrubs, herbaceous plants, and semi-shrubs that demonstrate tolerance to drought and salt. Most plant samples showed elevated levels of Cd, Pb, and Zn, surpassing the maximum tolerance levels for dietary minerals in livestock. This elevated metal content poses potential threats to the health of local livestock and wildlife, yet it is also considered a potential for phytoremediation. Selected dominant plant species from the current study include Kalidium foliatum & gracile which shows potential as a Cd accumulator and indicator. Neotrinia splendens and Reaumuria songarica demonstrate potential as Cd excluders, with the latter exhibiting higher tolerance to Cd (62.9 mg/kg). Additionally, our observations indicate that different plant parts exhibit distinct responses to heavy metals, and Zn synergistically influences the aerial part accumulation of Cd. This study holds significant importance in understanding the complex behavior patterns of multi-metal pollutants in the natural environment. The identification of native plants with remediation potential is valuable for phytoremediation of environment pollution in mining area.


Assuntos
Poluentes Ambientais , Metais Pesados , Poluentes do Solo , Solo , Cádmio , Fazendas , Chumbo , Poluentes do Solo/análise , Metais Pesados/análise , Plantas , China , Monitoramento Ambiental
3.
Sci Total Environ ; 870: 162012, 2023 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-36737027

RESUMO

The contrasting chemical behaviors of two toxic elements, arsenic (As) and cadmium (Cd) in co-contamination calcareous soil and its absorption by crops have not been thoroughly explored, especially in the implementation of the measure of prohibiting the use of wastewater to irrigate farmland. We propose that the present environmental characteristics of ecologically fragile areas and appropriate restoration measures are critical determinant of soil remediation. In this study, the typical field farmland irrigated by industrial and domestic wastewater in the Chinese Loess Plateau for >50 years was selected. The results showed that after the sewage irrigation was stopped, the mean contents of Cd (7.09 mg/kg) and As (13.47 mg/kg) in the soil were still rising, which might be a potential input source. The average values of soil risk indices such as the potential ecological risk (PERI = 2394), pollution load index (PLI > 4 for 60 % of studied samples), and degree of contamination (Dc = 86.6) showed severe soil pollution in the study area. The decrease of soil pH, the loss of soil texture and calcium carbonate were found to be the reasons for the high chemical activity of Cd. The bioconcentration factors (< 0.2) and translocation factor (> 1.0) of Cd indicate that corn is an excluder plant and an ideal phytoremediation method. Thus, 20 % of studied samples were higher than maximum permitted levels of Cd in grain, indicating potential related health hazards. On the contrary, As was mainly adsorbed in calcareous soil, and its bioavailability was lower compared with Cd. The difference between DTPA extraction and sequential extraction may be due to the transformation of chemical forms, resulting in unstable fractions increased the bioavailability of toxic elements. Overall, the findings provide new insights for solutions to manage and repair farmlands under the post-wastewater irrigation period.


Assuntos
Arsênio , Metais Pesados , Poluentes do Solo , Cádmio/análise , Solo/química , Zea mays , Águas Residuárias , Poluentes do Solo/análise , Produtos Agrícolas , China , Biodegradação Ambiental , Metais Pesados/análise , Monitoramento Ambiental
4.
Sci Total Environ ; 859(Pt 1): 160171, 2023 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-36379339

RESUMO

It is not known what the buffering capacity of soils and arsenic (As) enrichment by crops is for calcareous agricultural soils after the end of long-term effluent irrigation. In this study, changes in soil physicochemical properties and factors of influencing As uptake by wheat were investigated in agricultural soils where sewage irrigation had been ceased for nearly 20 years. The results showed that the content of CaCO3 and pH in soil increased compared to the period before the cessation of sewage irrigation, but remained below the soil background value. Furthermore, CaCO3 is by far the main buffering substance in agricultural soils and indirectly contributes to the increase in pH. The As concentration in the soil was 36.4 ± 34.8 mg/kg, which was 0.56-10.28 times and 0.28-5.18 times higher than the soil background and risk screening values, respectively, but showed a decreasing trend. pH and Fe dissolution were the main reasons for the lower As concentration in the soil. Total As in soil was a better predictor of As in wheat, and soil electrical conductivity (EC) and soil organic matter (SOM) promoted As uptake by wheat. The competitive uptake of As by dissolved Si was an important reason for the mismatch between As concentrations in soil and wheat. This study highlighted the key issues of As transport transformation in soil-wheat systems after cessation of effluent irrigation, using agricultural soils, and provided a reference for soil risk management in agricultural soils in mining areas.


Assuntos
Arsênio , Poluentes do Solo , Solo/química , Triticum/química , Poluentes do Solo/análise , Irrigação Agrícola , Esgotos
5.
Ecotoxicol Environ Saf ; 245: 114126, 2022 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-36183429

RESUMO

The bio-remediation of As-polluted farmlands in the arid area is seldomly reported. This study aimed at understanding the impact of DOM, Fe-oxides, and FeOB biogeochemical processes on As remediation. The approaches used included: FeOB strain Pseudomonas flavescens LZU-3; Batch-experiment. Our results showed that all FeOB tested effectively immobilized As (>95%) during microbial mineralization; DOM play an important role in the reduction of Fe(III)(hydr)oxides and As(V); Less-crystallized ferrihydrite transform to more-crystallized goethite and secondary minerals; Under the reaction of FeOB and DOM, the As-Fe-OM ternary compound were formed, containing N, S, C and O functional group; The addition of OM can clearly reduce soil Eh, promoting dissolution of As in bound to iron oxides, co-precipitation of the amorphous iron oxide in Fe(III)-OM-FeOB, closely related to As in bound to insoluble organics and sulfides and mineral residues, which plays an important role in controlling the mobilization of As. This study provides controlling of As transportation and transformation in the As-DOM-Bio-Fe ternary system as As-remediation technology in the arid soil.


Assuntos
Compostos Férricos , Ferro , Bactérias/metabolismo , Compostos Férricos/química , Ferro/química , Minerais/química , Oxirredução , Óxidos/metabolismo , Solo/química , Sulfetos/metabolismo
6.
PeerJ ; 9: e12538, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34917423

RESUMO

BACKGROUND: The benefits of probiotics being used in animals are well-documented via evidenced growth performance improvement and positive modulations of gut microbiota (GM). Thus, a combination of effective microorganisms (EM) has been frequently used in animal production, including broilers. However, there are only very limited reports of EM on the growth performance and the modulation in GM of partridge shank broiler chicks. METHODS: We attempted to evaluate the effects of a basal diet with the addition of an EM mixture on the growth performance and gut microbiome of the chicks. A total of 100 ten-day-old female partridge shank broiler chicks were randomly divided into two groups of 50 chicks each, of which, one group fed with EM supplementation in the basal diet (designated as EM-treated group), the other group just fed with a basal diet (referred as to non-EM treated group or control group). The body weight, daily feed intake, daily gain, feed conversion ratio and other growth parameters were observed and compared between EM-treated and non-EM-treated chicks, and the gut microbiota was profiled by 16S rRNA-based next generation sequencing (NGS). RESULTS: EM-treated chicks showed significantly increased performances in body weight (BW), average daily gain (ADG) and reduced feed conversion ratio (FCR). Histological observation indicated that dietary supplementation of EM significantly increased the villus heights (VH) and the ratio of villus height to crypt depth (VH/CD), while decreased the CD of jejunum, ilea, and ceca. The results of 16S rRNA-based gut microbiota analyses showed that Firmicutes accounted for the most of the relative abundance (63.24%∼92.63%), followed by Proteobacteria (0.62%∼23.94%), Bacteroidetes (0.80%∼7.85%), Actinobacteria (0.06%∼13.69%) and others in both EM-treated and non-EM-treated broiler chicks. The addition of EM could not alter the alpha diversity of gut microbiota. Compared with the non-EM-treated chicks, the abundances of bad bacteria in the phyla of Firmicutes, Euryarchaeota, and Ruminococcus were dramatically decreased in that of EM-treated chicks, while the abundances of good bacteria in the phyla of Actinobacteria and WPS-2 were significantly increased. CONCLUSIONS: The supplementation of EM in feed could improve the growth performance and positively influence the morphological characteristics of the intestine, and ameliorate the community and structure of the intestinal microbiota of partridge shank broiler chicks.

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