Nitrated hydrochar reduce the Cd accumulation in rice and shift the microbial community in Cd contaminated soil

Study on the changes in the microbiome before and after seed embryo after-ripening of Fritillaria cirrhosa

Introduction

Microorganisms play an important role in the embryonic development of plant seeds; however, there are no existing reports on the microbial communities associated with Fritillaria cirrhosa before and after embryo after-ripening.

Methods

In this study, the microbial communities of Fritillaria cirrhosa seeds before and after after-ripening were analyzed using the Illumina MiSeq platform, targeting the V4-V5 region of the bacterial 16S rRNA gene and the ITS1 and ITS2 regions of fungal ribosomal RNA.

Results

The results showed that bacterial communities were more susceptible to environmental stress and exhibited greater fluctuations compared to fungal communities, as reflected in higher diversity and significant changes in the relative abundance of dominant genera and species. After embryo after-ripening, the dominant fungal genera were Botrytis (SBAR, 29.35%), Tetracladium (SBAR, 15.86%), Ilyonectria (SBAR, 15.35%), and Mrakia (SBAR, 13.14%), while the dominant bacterial genera were Pseudomonas (SBAR, 26.69%) and Stenotrophomonas (SBAR, 16.30%).Prediction results suggested that the bacterial communities with sharply increased relative abundance after embryo after-ripening may interact with seeds through various pathways, including carbohydrate metabolism, absorption and utilization of nitrogen (N), sulfur (S), phosphorus (P), and iron (Fe), as well as secretion of antibiotics, vitamins, cytokinins, and amino acids. Functional validation revealed that most culturable fungi with sharply increased relative abundance had cellulase-degrading abilities, while most of the bacterial isolates were capable of absorbing and utilizing C, N, S, P, and Fe elements. Microbial co-occurrence network analysis indicated that the microbiome after embryo after-ripening formed an unstable, expansive, and rapidly changing network.

Discussion

In summary, this study revealed the overall dynamics of the microbiome in Fritillaria cirrhosa seeds after embryo after-ripening and identified key microbial taxa exhibiting sharp shifts in relative abundance. This work provides a foundational understanding of the microbial succession associated with seed embryo after-ripening in Fritillaria cirrhosa, which may support seed after-ripening and germination, and enhance seed stress resistance.

Assessing soil cadmium quality standards for different land use types: A global synthesis

The contamination of cadmium (Cd) in soil has become an increasingly serious issue worldwide, presenting significant risks to human health, crop safety, and ecosystems. Despite its importance, there is a lack of standardized soil threshold values for use in regulating exposure to Cd-contaminated surface soil. By synthesizing soil environmental standards for Cd from 61 countries and 75 regions, this study analyzed and categorized these standards by land use types. The distribution of Cd quality standards among various countries was determined, based on available data primarily from the United States, Canada, Europe, Australia, and China. The established soil Cd quality standards were also determined for different land types, including lands for agricultural, residential, industrial, construction, commercial uses, and parks/green spaces. Using the ecological environment criteria - species sensitivity distribution (ECC-SSD) model, Cd levels were analyzed across different land use types, and it was determined that a log-logistic distribution was the best fitted model. Our findings indicated that soil Cd quality standards ranged from 0.11 to 5.20 mg/kg for agricultural land, 1.25 to 171.51 mg/kg for residential land, and 2.58 to 1845.26 mg/kg for industrial land, all within the 5-95 % percentile range. The 5 % hazard concentration (HC5) value was recommended as the latest national quality standards for each land type. This comprehensive assessment of global soil Cd quality standards provides valuable insight for decision-makers tasked with effectively managing and mitigating Cd pollution in soil.

In-situ remediation of cadmium contamination in paddy fields: from rhizosphere soil to rice kernel

Cadmium (Cd) has become an important heavy metal pollutant because of its strong migration and high toxicity. The industrial production process aggravated the Cd pollution in rice fields. Human exposure to Cd through rice can cause kidney damage, emphysema, and various cardiovascular and metabolic diseases, posing a grave threat to health. As modern technology develops, the Cd accumulation model in rice and in-situ remediation of Cd pollution in cornfields have been extensively studied and applied, so it is necessary to sort out and summarize them systematically. Therefore, this paper reviewed the primary in-situ methods for addressing heavy metal contamination in rice paddies, including chemical remediation (inorganic-organic fertilizer remediation, nanomaterials, and composite remediation), biological remediation (phytoremediation and microbial remediation), and crop management remediation technologies. The factors that affect Cd transformation in soil and Cd migration in crops, the advantages and disadvantages of remediation techniques, remediation mechanisms, and the long-term stability of remediation were discussed. The shortcomings and future research directions of in situ remediation strategies for heavily polluted paddy fields and genetic improvement strategies for low-cadmium rice varieties were critically proposed. To sum up, this review aims to enhance understanding and serve as a reference for the appropriate selection and advancement of remediation technologies for rice fields contaminated with heavy metals.

Effect of wood and peanut shell hydrochars on the desiccation cracking characteristics of clayey soils

Soil cracking can significantly alter the water and nutrient migration pathways in the soil, influencing plant growth and development. While biochar usage has effectively addressed soil cracking, the feasibility of using less energy-intensive hydrochars in desiccating soils remains unexplored. This study investigates the impact of wood and peanut shell hydrochars on the desiccation cracking characteristics of clayey soil. A series of controlled environmental laboratory incubations with regular imaging was conducted to determine crack development's dynamic in unamended and hydrochar-amended soils. The results reveal that the addition of wood hydrochar at 2% and 4% dosage reduced the crack intensity factor (CIF) by 22% and 43%, respectively, compared to the unamended control soil. Similarly, the inclusion of peanut shell hydrochar at 2% and 4% lowered the CIF by 22% and 51%, respectively. The presence of hydrophilic groups on the surface of hydrochars, such as O-H, CH, and C-O-C, enhanced the water retention capacity, as confirmed by Fourier-transform infrared analysis. The CIF decrease is attributed to mitigated water evaporation rates, enabled by enhanced water retention within the hydrochar pore spaces. These findings are supported by scanning electron microscopy analyses of the hydrochar morphology. Despite CIF reduction with hydrochar incorporation, the crack length density (CLD) increased across all hydrochar-amended series. In contrast to unamended soil which exhibited pronounced widening of large cracks and extensive inter-pore voids, the incorporation of hydrochar resulted in higher CLD due to the formation of finer interconnecting crack meshes. Consequently, the unamended control soil suffered greater water loss due to heightened evaporation rates. This study sheds new light on the potential of hydrochars in addressing desiccation-induced soil cracking and its implications for water conservation.

Combined application of arbuscular mycorrhizal fungi and selenium fertilizer increased wheat biomass under cadmium stress and shapes rhizosphere soil microbial communities

BACKGROUND

Selenium (Se) fertilizer and arbuscular mycorrhizal fungi (AMF) are known to modulate cadmium (Cd) toxicity in plants. However, the effects of their co-application on wheat growth and soil microbial communities in Cd-contaminated soil are unclear.

RESULTS

A pot experiment inoculation with two types of AMF and the application of Se fertilizer under Cd stress in wheat showed that inoculation AMF alone or combined with Se fertilizer significantly increased wheat biomass. Se and AMF alone or in combination significantly reduced available Cd concentration in wheat and soil, especially in the Se combined with Ri treatment. High throughput sequencing of soil samples indicated that Se and AMF application had stronger influence on bacterial community compared to fungal community and the bacterial network seemed to have more complex interconnections than the fungal network, and finally shaped the formation of specific microflora to affect Cd availability.

CONCLUSION

These results indicate that the application of Se and AMF, particularly in combination, could successfully decrease soil Cd availability and relieve the harm of Cd in wheat by modifying rhizosphere soil microbial communities.

Assessment of human exposure to cadmium and its nephrotoxicity in the Chinese population

BACKGROUND

Cadmium (Cd) is a toxic heavy metal that widely detected in environment and accumulated in kidney, posing a great threat to human health. However, there is a lack of systematic investigation of exposure profile and association of Cd exposure with renal function in the Chinese population.

METHODS

Related articles were searched from PubMed, Web of Science, China National Knowledge Internet, and Wanfang to construct an aggregate exposure pathway (AEP) framework for Cd and to explore the correlation between Cd and renal function using random effects models.

RESULTS

A total of 220 articles were included in this study, among which 215 investigated human exposure and 12 investigated the association of Cd with renal outcomes. The AEP framework showed that 96.5 % and 62.5 % of total Cd intake were attributed to dietary intake in nonsmokers and smokers, respectively. And 35.2 % originated from cigarette smoke inhalation in smokers. In human body, Cd was detected in blood, urine, placenta, etc. Although the concentrations of Cd in blood and urine from subjects living in polluted areas showed a sharp downward trend since the early 21st century, higher concentration of Cd in the environment and human body in polluted areas was found. Kidney was the target organ. The level of blood Cd was positively associated with urinary β2-microglobulin [β2-MG, r (95 % CI) = 0.12 (0.05, 0.19)], albumin [0.13 (0.06, 0.20)], and retinol-binding protein [RBP, 0.14 (0.03, 0.24)]. Elevated urinary Cd was correlated with increases in β2-MG [0.22 (0.15, 0.29)], albumin [0.23 (0.16, 0.29)], N-acetyl-β-d-glucosaminidase [NAG, 0.33 (0.22, 0.44)], and RBP [0.22 (0.14, 0.30)].

CONCLUSIONS

Foods and cigarette smoke were two major ways for Cd intake, and Cd induced renal injury in the Chinese population. This study enhanced the understanding of human exposure and nephrotoxicity of Cd, and emphasized the need for controlling Cd level in polluted areas.

Alleviating the adverse effects of Cd-Pb contamination through the application of silicon fertilizer: Enhancing soil microbial diversity and mitigating heavy metal contamination

The use of silicon fertilizer (SF) as a means of remediating cadmium (Cd) and lead (Pb) pollution has proven to be beneficial. However, the mechanism via which SF enhances soil quality and crop productivity under Cd- and Pb-contaminated soil (S) remains unclear. This study investigated the impacts of chemical fertilizer, mineral SF (MSF), and organic SF (OSF) on microbial community structure, activity of nutrient acquisition enzymes, and growth of tobacco in the presence of S condition. SF significantly reduced the contents of Cd and Pb in soil under S condition by 6.92-42.43% and increased plant height and leaf area by 15.27-81.77%. Moreover, the use of SF was observed to increase the efficiency of soil carbon and phosphorus cycling under S condition by 6.88-23.08%. Concurrently, SF was found to play a crucial role in facilitating the establishment of a complex, efficient, and interdependent molecular ecological network among soil microorganisms. In this context, Actinobacteriota, Bacteroidota, Ascomycota, and Basidiomycota were observed to be integral components of this network. SF was found to have a substantial positive impact on the metabolic functions and organismal systems of soil microorganisms. Moreover, the combined utilization of the Mantel test and partial least squares path model provided empirical evidence supporting the assertion that the administration of SF had a positive impact on both soil nutrient acquisition enzyme activity and tobacco growth, which was attributed to the enhancement of soil microbial diversity resulting from the application of SF. Furthermore, compared with MSF, OSF has advantages in reducing soil Pb and Cd content, promoting tobacco agronomic traits, increasing the number of key microbial communities, and maintaining the structural stability of microbial networks. The aforementioned findings, therefore, suggest that the OSF played a pivotal role in alleviating the adverse impacts of S, thereby demonstrating its efficacy in this particular process.