Heavy metals reshaping the structure and function of phylloplane bacterial community of native plant Tamarix ramosissima from Pb/Cd/Cu/Zn smelting regions.

Heavy metal (HM) is noxious element that cannot be biodegraded, thus accumulating in the environment and posing a serious threat to the ecology. Plant phylloplane harbors diverse microbial communities that profoundly influence ecosystem functioning and host health. With more HM accumulating around smelters, native plants and microbes in various habitats tend to suffer from HM. However, the response of phylloplane bacteria of native plants to HM remains unclear. Thus, this study aimed to explain the response of Tamarix ramosissima, a phylloplane bacterial community to HM as well as the effect of the process on host growth in situ by investigating the potential source of HM and bacterial community shift. Results showed that, in most cases, the contaminated site with high HM level caused more accumulation of HM in phylloplane and leaves. Moreover, HM in the phylloplane was not from the internal transport of the plant but it could be due to the wind action or rains. Bacteria in phylloplane may have come from the soil due to their strong positive correlation with corresponding soil at the genus level. High HM level inhibited the relative abundance of dominant bacteria, increased the diversity and species richness of bacterial community in phylloplane, and induced more special bacteria to maintain higher productivity of the host plant, for which, Cu and Pb were the major contributors. Meanwhile, bacteria in phylloplane showed a universal positive correlation in the co-occurrence network, which showed less stability than that in corresponding soil in the smelting region, and it is helpful to regulate the growth of plants more rapidly. Nearly 25% of KEGG pathways were modulated by high HM level and bacterial function tended to stabilize HM to avoid the potential process of leaf absorption. The study illustrated that HM in phylloplane played an important role in shaping the bacterial community of phylloplane as compared to HM in leaves or phyllosphere, and the resulting increase of diversity and richness of bacterial community and special bacteria further maintained the growth of the host plant suffering from HM stress.

[Research progress and maturity assessment of continuous manufacturing of traditional Chinese medicine].

The pharmaceutical manufacturing model is gradually changing from intermittent manufacturing to continuous manufacturing and intelligent manufacturing. This paper briefly reviewed the supervision and research progress in continuous pharmaceutical manufacturing in China and abroad and described the definition and advantages of continuous pharmaceutical manufacturing. The continuous manufacturing of traditional Chinese medicine(TCM) at the current stage was summarized in the following three terms: the enhancement of the continuity of intermittent manufacturing operations, the integration of continuous equipment to improve physical continuity between units, and the application of advanced process control strategies to improve process continuity. To achieve continuous manufacturing of TCM, the corresponding key technologies, such as material property characterization, process modeling and simulation, process analysis technology, and system integration, were analyzed from the process and equipment, respectively. It was proposed that the continuous manufacturing equipment system should have the characteristics of high speed, high response, and high reliability, "three high(H~3)" for short. Considering the characteristics and current situation of TCM manufacturing, based on the two dimensions of product quality control and production efficiency, a maturity assessment model for continuous manufacturing of TCM, consisting of operation continuity, equipment continuity, process continuity, and quality control continuity, was proposed to provide references for the application of continuous manufacturing technology for TCM. The implementation of continuous manufacturing or the application of key continuous manufacturing technologies in TCM can help to systematically integrate advanced pharmaceutical technology elements and promote the uniformity of TCM quality and the improvement of production efficiency.

Effects of polystyrene, polyethylene, and polypropylene microplastics on the soil-rhizosphere-plant system: Phytotoxicity, enzyme activity, and microbial community.

The widespread presence of soil microplastics (MPs) has become a global environmental problem. MPs of different properties (i.e., types, sizes, and concentrations) are present in the environment, while studies about the impact of MPs having different properties are limited. Thus, this study investigated the effects of three common polymers (polystyrene, polyethylene, and polypropylene) with two concentrations (0.01% and 0.1% w/w) on growth and stress response of lettuce (Lactuca sativa L.), soil enzymes, and rhizosphere microbial community. Lettuce growth was inhibited under MPs treatments. Moreover, the antioxidant system, metabolism composition, and phyllosphere microbiome of lettuce leaves was also perturbed. MPs reduced phytase activity and significantly increased dehydrogenase activity. The diversity and structure of rhizosphere microbial community were disturbed by MPs and more sensitive to polystyrene microplastics (PSMPs) and polypropylene microplastics (PPMPs). In general, the results by partial least squares pathway models (PLS-PMs) showed that the presence of MPs influenced the soil-rhizosphere-plant system, which may have essential implications for assessing the environmental risk of MPs.

Variance of soil bacterial community and metabolic profile in the rhizosphere vs. non-rhizosphere of native plant Rumex acetosa L. from a Sb/As co-contaminated area in China.

Heavy metals (HMs) contamination poses a serious threat to soil health. However, the rhizosphere effect of native pioneer plants on the soil ecosystem remains unclear. Herein, how the rhizosphere (Rumex acetosa L.) influenced the process of HMs threatening soil micro-ecology was investigated by coupling various fractions of HMs, soil microorganisms and soil metabolism. The rhizosphere effect alleviated the HMs' stress by absorbing and reducing HMs' direct bioavailability, and the accumulation of ammonium nitrogen increased in the rhizosphere soil. Meanwhile, severe HMs contamination covered the rhizosphere effect on the richness, diversity, structure and predicted function pathways of soil bacterial community, but the relative abundance of Gemmatimonadota decreased and Verrucomicrobiota increased. The content of total HMs and physicochemical properties played a more important role than rhizosphere effect in shaping soil bacterial community. Furthermore, As was observed to have a more significant impact compared to Sb. Moreover, plant roots improved the stability of bacterial co-occurrence network, and significantly changed the critical genera. The process influenced bacterial life activity and nutrient cycling in soil, and the conclusion was further supported by the significant difference in metabolic profiles. This study illustrated that in Sb/As co-contaminated area, rhizosphere effect significantly changed soil HMs content and fraction, soil properties, and microbial community and metabolic profiles.

Responses of microbial communities and metabolic profiles to the rhizosphere of Tamarix ramosissima in soils contaminated by multiple heavy metals.

Heavy metals (HMs) contamination around smelters poses serious stress to soil microbiome. However, the co-effect of multiple HMs and native vegetation rhizosphere on the soil ecosystem remains unclear. Herein, effects of high HMs level and the rhizosphere (Tamarix ramosissima) on soil bacterial community structure and metabolic profiles in sierozem were analyzed by coupling high-throughput sequencing and soil metabolomics. Plant roots alleviated the threat of HMs by absorbing and stabilizing them in soil. High HMs level decreased the richness and diversity of soil bacterial community and increased numbers of special bacteria. Plant roots changed the contribution of HMs species shaping the bacterial community. Cd and Zn were the main contributors to bacterial distribution in non-rhizosphere soil, however, Pb and Cu became the most important HMs in rhizosphere soil. HMs induced more dominant metal-tolerant bacteria in non-rhizosphere than rhizosphere soil. Meanwhile, critical metabolites varied by rhizosphere in co-occurrence networks. Moreover, the same HMs-tolerant bacteria were regulated by different metabolites, e.g. unclassified family AKYG1722 was promoted by Dodecanoic acid in non-rhizosphere soil, while promoted by Octadecane, 2-methyl- in rhizosphere soil. The study illustrated that high HMs level and rhizosphere affected soil properties and metabolites, by which soil microbial community structure was reshaped.

Combined effects of oxytetracycline and microplastic on wheat seedling growth and associated rhizosphere bacterial communities and soil metabolite profiles.

The widespread application of antibiotics and plastic films in agriculture leads to new characteristics of soil pollution with the coexistence of antibiotics and microplastics. However, their combined effects on wheat seedling growth and associated rhizosphere bacterial communities and soil metabolite profiles remain unclear. Here, in the potted experiment, wheat was treated with individual oxytetracycline (0, 5.0, 50.0, and 150.0 mg kg-1) and the combination of oxytetracycline and polyethylene microplastic (0.2%). Results showed that 150 mg kg-1 oxytetracycline combined with microplastic significantly reduced the biomass and height of the plant. Compared with CK, all the treatments exposed to the combination of oxytetracycline and polyethylene microplastic significantly promoted carotenoid content and peroxidase activity in wheat leaves. Soil dehydrogenase and urease activities were more sensitive to current pollutant exposure than sucrase activity. Oxytetracycline (150 mg kg-1) alone and in combination with polyethylene significantly decreased the abundances of certain genera belonging to plant growth-promoting rhizobacteria (PGPR) in soil, such as Arthrobacter, Gemmatimonas, Massilia, and Sphingomonas. Combined exposure of 150 mg kg-1 oxytetracycline and polyethylene microplastic significantly altered multiple metabolites including organic acids and sugars. Network analysis indicated that co-exposure of 150 mg kg-1 oxytetracycline and microplastic may affect the colonization and succession of PGPR by regulating soil metabolites, thereby indirectly inhibiting wheat seedling growth. The results help to elucidate the potential mechanisms of phytotoxicity of the combination of oxytetracycline and polyethylene microplastic.

Stress response to oxytetracycline and microplastic-polyethylene in wheat (Triticum aestivum L.) during seed germination and seedling growth stages.

Much efforts have been devoted to clarify the phytotoxicity of individual contaminants in plants, such as individual antibiotic and microplastic; however, little is known about the phytotoxicity of their combined exposure. Here, we investigated the effects of individual and combined exposure of wheat (Triticum aestivum L.) (Xiaoyan 22) to oxytetracycline (OTC) and polyethylene (PE) microplastics using physiological and metabolic profilings. During the seed germination stage, OTC induced phytotoxicity, as observed through the changes of root elongation, sprout length, fresh weight and the vitality index, with significant effect at the 50 and 150 mg·L-1 levels; the effect of PE microplastics depended on the OTC level in the combined exposure groups. During seedling cultivation, catalase (CAT) and ascorbate peroxidase (APX), as antioxidant enzyme indices, were sensitive to OTC exposure stress, although OTC was not determined in leaves. Untargeted metabolomics of wheat leaves revealed OTC concentration-, metabolite class- and PE-dependent metabolic responses. Dominant metabolites included carboxylic acids, alcohols, and amines in the control group and all treatment groups. Compared to only OTC treatment, PE reprogrammed carboxylic acid and alcohol profiles in combined exposure groups with obvious separation in PLS-DA. Combined exposure induced fewer metabolites than OTC exposure alone at the 5 and 50 mg·L-1 levels. The shared metabolite numbers were higher in the OTC groups than in the PE-OTC groups. Pathway enrichment analysis showed a drift in metabolic pathways between individual and combined exposure to OTC and PE, which included glyoxylate and dicarboxylate metabolism, amino acid metabolism and isoquinoline alkaloid biosynthesis. Among metabolites, aromatic acids and amino acids were more sensitive to combined exposure than individual exposure. These results contribute to clarifying the underlying mechanisms of phytotoxicity of individual and combined exposure to OTC and PE.

Prochloraz alone or in combination with nano-CuO promotes the conjugative transfer of antibiotic resistance genes between Escherichia coli in pure water.

Conjugative plasmid transfer is a major contributor to the spread of antibiotic resistance genes (ARGs). However, the role of conventional fungicides on conjugative plasmid transfer has been neglected. Based on the condition that the increasing use of the combination of nano- and conventional fungicides will lead to combined contamination, the effects of a conventional fungicide prochloraz alone or in combination with nano-CuO on the conjugation of plasmid RP4 between Escherichia coli in phosphate-buffered saline were investigated in this study. The results demonstrated that 50 µg/L prochloraz alone significantly increased the conjugative transfer by 1.82 folds. The combination of 100 µg/L nano-CuO and prochloraz at 5, 50, and 500 µg/L significantly increased the conjugation by 2.56, 3.61, and 2.13 folds, respectively. The promotion of conjugative transfer of ARGs mediated by fungicides is mainly attributed to (i) the increased cell membrane permeability, (ii) the increased cell adhesion via enhancing the synthesis of polysaccharides in extracellular polymeric substances, and (iii) the up-regulation of the genes relevant to conjugation, oxidative stress, SOS response, outer membrane, polysaccharide export, intercellular adhesion, and ATP synthesis. Our findings provide evidence for the contribution of fungicides to ARGs transfer, which is significant to control the risk of ARGs dissemination.

Genotoxicity of tetracycline as an emerging pollutant on root meristem cells of wheat (Triticum aestivum L.).

Increasing attention has been paid to antibiotic contamination as an increasingly serious environmental issue. Tetracycline has been widely used for decades in human and veterinary medicines, with incremental residues in the environment and adverse influences on living organisms. In the present study, the genetic toxicity of tetracycline was investigated using a bioassay method with wheat (Triticum aestivum L.) root-meristem cells at a concentration range of 0.25-300 mg L(-1) and exposure times of 24, 48, and 72 h. The results indicated that tetracycline at lower concentrations (0.25-1 mg L(-1) ) stimulated cell mitotic division, whereas at 50-300 mg L(-1) concentration caused a concentration-related decrease in mitotic index (MI). The lower tetracycline concentrations induced a slight increase in the frequency of micronucleus (MN), chromosomal aberration (CA), and sister chromatid exchange (SCE) in wheat root tips. However, there were significant increases in these indices at higher concentrations in concentration- and time-dependent manners, including the frequencies of MN (25-200 mg L(-1) ), CA (10-200 mg L(-1) ), and SCE (5-200 mg L(-1) ), respectively. The inducement of MN, CA, and SCE decreased at 250 and 300 mg L(-1) due to acute cell toxicity for all tested times. Comparatively, SCE was the most sensitive, followed by CA, with MN the least sensitive to the genotoxicity of tetracycline in wheat. These results imply that tetracycline may be genotoxic to plant cells, and exposure to tetracycline may pose a genotoxic risk to living organisms. The results also suggest that the wheat bioassay was efficient, simple, and reproducible in monitoring the genotoxicity of tetracycline in the environment.

Physiological and potential genetic toxicity of chlortetracycline as an emerging pollutant in wheat (Triticum aestivum L.).

Increasing attention is now being paid to antibiotic contamination as a serious environmental issue. Chlortetracycline has been widely used for decades as a human and veterinary medicine, which has resulted in environmental residues and damage to living organisms. In the present study, the physiological and potential genetic toxicity of chlortetracycline was investigated using a wheat (Triticum aestivum L.) bioassay at a concentration range of 0.0625 to 300 mg/L and an exposure time of 24, 48, and 72 h. The results indicated that chlortetracycline at the lower concentrations stimulated germination and cell mitotic division and growth, whereas higher concentrations significantly inhibited processes such as bud length (50-300 mg/L), percentage germination (25-300 mg/L), root length (25-300 mg/L), and mitotic index (MI) (25-300 mg/L). The lowest concentration of chlortetracycline slightly augmented the frequency of micronucleus (MN), chomosomal aberration (CA), and sister chomatid exchange (SCE) in the root tips; however, significant (p < 0.05 and 0.01) levels of augmentation were observed at higher concentrations in a concentration-dependent manner, including the frequencies of MN (25-200 mg/L), CA (10-200 mg/L), and SCE (5-200 mg/L), respectively. The inducement of MN, CA, and SCE decreased at 250 and 300 mg/L as a result of acute cell toxicity. In addition, all endpoints showed a time-dependent increase at 0.0625 to 200 mg/L. These results imply that chlortetracycline (>or=5 mg/L) may be genotoxic to plant cells, and exposure to chlortetracycline may pose a potential genotoxic risk to living organisms. Comparatively, SCE was the most sensitive, followed by CA, and MN was the least sensitive to chlortetracycline genotoxicity in wheat. The results also suggest that the wheat bioassay is efficient, simple, and reproducible for monitoring the genotoxicity of chlortetracycline in the environment.

Ecotoxicological effects of polycyclic musks and cadmium on seed germination and seedling growth of wheat (Triticum aestivum).

Single and joint toxic effects of polycyclic musks including 1,3,4,6,7,8-hexahydro-4,6,6,6,7,8,8-hexamethylcyclopenta[g]-2-benzopyran (HHCB) and 7-acetyl-1,1,3,4,4,6-hexamethyl-l,2,3,4-tetrahydronapthalene (AHTN) and cadmium (Cd) on seed germination and seedling growth of wheat (Triticum aestivum) were investigated. The results showed that the toxicity sequence of HHCB toxic to wheat seed germination and seedling growth was similar to that of AHTN, that is, germination rate > shoot elongation > root elongation, while the toxicity of Cd was in the sequence of root elongation > shoot elongation > germination rate, according to the LC50 and EC50 values. It is suggested that polycyclic musks and Cd had different toxicological mechanisms. Root and shoot elongation of wheat might be good bioindicators for the contamination of polycyclic musks and Cd in soil. The mixture of polycyclic musks and Cd had synergistic effects on T. aestivum according to the equi-toxic mixture approach when root elongation was selected as the toxicological endpoint. Thus, the joint toxicity of HHCB and Cd was significantly higher than the single toxicity of HHCB or Cd, which was also confirmed by the EC50 mix value of the mixture (EC50 mix = 0.530 TUmix). The EC(50mix) value of the mixture of AHTN and Cd was 0.614 TUmix, which indicated that the mixture toxicity was strengthened when AHTN coexisted with Cd.

Linkage of antibiotic resistance genes, associated bacteria communities and metabolites in the wheat rhizosphere from chlorpyrifos-contaminated soil.

Rhizosphere is a crucial site for the proliferation of antibiotic resistance genes (ARGs) in agricultural soil. Pesticide contamination is ubiquitous in soil, such as chlorpyrifos as one of the most commonly used pesticides. However, limited knowledge is reported about ARGs profiles changes and the driving mechanism of ARGs prevalence in rhizosphere soil after adding pesticide. In this study, irrespective of chlorpyrifos presence, the abundances of ARGs (tetM, tetO, tetQ, tetW, tetX, sul1 and sul2) and intI1 in rhizosphere soil of wheat were obviously higher than those in bulk soil. 20.0 mg·kg-1 chlorpyrifos significantly increased the abundance of total ARGs and intI1 in bulk soil, respectively, at day 50 and 100, but not in rhizosphere soil. Rhizosphere influence on ARGs was far greater than chlorpyrifos. ARGs and intI1 abundances were higher at day 50 than ones at day 100. C/N ratio and NO3--N content, which were affected by rhizosphere and cultivation time, significantly explained the increased ARGs. Compared to bulk soil, rhizosphere shifted host bacteria of tetracycline resistance genes (TRGs), intI1 at genus level, and host bacteria of sul1, sul2 at phylum level. Rhizosphere simplified the linkage of ARGs, host bacteria and metabolites. Bacterial communities played important roles in the variation of ARGs and intI1, and the difference in the distribution of potential hosts between bulk and rhizosphere soil was related to metabolites abundance and composition. These results provide valuable information for understanding the linkage of ARGs, associated bacteria communities and metabolites in the wheat rhizosphere soil.

Environmentally Relevant-Level CeO2 NP with Ferrous Amendment Alters Soil Bacterial Community Compositions and Metabolite Profiles in Rice-Planted Soils.

The environmental risks and benefits associated with the introduction of CeO2 nanoparticle (NP) in agricultural soil must be carefully assessed. The ferrous ion is rich in rhizosphere soil of rice due to the reduction states underground. The aim of this study was to investigate the effects of environmentally relevant-level CeO2 NP (25 mg·kg-1) in the absence or presence of ferrous (30 mg·kg-1) amendment on soil bacterial communities and soil metabolomics in rice-planted soil over 150 days. Results showed that CeO2 NP exposure changed soil bacterial community compositions and soil metabolomics, and the above changes were further shifted with the ferrous amendment. Several functionally significant bacterial phyla containing Proteobacteria and Bacteroidetes abundances, which were associated with carbon and nitrogen cycling, were promoted after CeO2 NP exposure with ferrous amendment. However, CeO2 NP inhibited plant-growth-promoting rhizobacteria containing genera Bacillus and Arthrobacter irrespective of the presence or absence of ferrous. Among rhizosphere soil enzyme activities, cellulose activity was the most sensitive for CeO2 NP exposure. NP decreased Firmicutes and increased Chloroflexi, Rokubacteria, and Thaumarchaeota abundances at the phylum level, which contributed to reduce soil cellulose activity. Additionally, CeO2 NP positively or negatively affected soil pH, Ce accumulation in root, and rice physiological properties (root-POD, stem-POD). As a result, the above factors were related to the changes of Chloroflexi, Gemmatimonadetes, Rokubacteria, Thaumarchaeota, and Nitrospirae at the phylum level. After adding CeO2 NP with ferrous or not, the main metabolic changes were concentrated on fluctuations in starch and sucrose metabolism, nitrogen metabolism, sulfur metabolism, propanoate metabolism, fatty acid metabolism, and urea cycle. The eight changed metabolites containing glycerol monstearate, boric acid, monopalmitin, palmitic acid, alkane, ethanol, dicarboximide, and stearic acid accounted for the separation of different treatments with CeO2 NP exposure. Activities of soil enzymes (urease, invertase, and cellulose), pH, and soil organic matter affected dominant metabolites containing fatty acids, inorganic acid, and sugar. Network analysis showed that the influence of soil bacterial community on metabolites varied with metabolites and bacteria species. The presence of CeO2 NP mainly promoted fatty acids (hexanoic acid, nonanoic acid) and amino acid (oxoproline) and amine (diethanolamine) concentrations, which could be from the increased Proteobacteria abundance after CeO2 NP exposure. Phylum Proteobacteria had the most genus species containing 13 genera affecting soil metabolite profiles. These results provide valuable information for understanding the impact of environmentally relevant-level CeO2 NP exposure on soil microbial communities and metabolites with or without ferrous, which is needed to understand the ecological risk posed by long-term CeO2 NP exposure in rice-planted soil with rich ferrous.

Citric acid enhances Ce uptake and accumulation in rice seedlings exposed to CeO2 nanoparticles and iron plaque attenuates the enhancement.

To assess the role of citric acid, as a typical low-molecular-weight organic acid from root exudates, on cerium (Ce) uptake, accumulation and translocation in rice seedlings (Oryza sativa L.) exposed to two CeO2 nanoparticles (NPs) (14 nm and 25 nm). A hydroponic experiment was performed under two citric acid levels (0.01 and 0.04 mmol L-1) combined with iron plaque presence. Citric acid significantly enhanced surface-Ce, root-Ce and shoot-Ce accumulation, irrespective of NPs size and iron plaque presence. The increased surface-Ce was associated with the promoted interactive attraction between NPs and root surface, and the enhanced NPs dissolution. Surface-Ce (containing crystalline and amorphous fractions of iron plaque) accumulation increased with the increase of citric acid concentrations. However, the enhancement influence of 0.01 mmol L-1 citric acid on root-Ce, shoot-Ce accumulations, rice-Ce distribution and TFroot-shoot was more remarkable than citric acid (0.04 mmol L-1), which suggested higher food security risk for human health with environment-level citric acid. Iron plaque presence attenuated the enhancement effect of citric acid on rice-Ce accumulation and distribution (containing surface-Ce, root-Ce and shoot-Ce) due to the reduced attractive interaction between NPs and root surface from the effect of Fe2+ being dissolved by iron plaque. Above effect of citric acid and iron plaque was more remarkable in 25 nm NP than 14 nm NP.

Foliar spray of TiO2 nanoparticles prevails over root application in reducing Cd accumulation and mitigating Cd-induced phytotoxicity in maize (Zea mays L.).

Cadmium (Cd) pollution is considered one of the global environmental issues due to its adverse effects on plant and human health. With the rapid development of nanotechnology and the practical application of engineered nanoparticles (ENPs) in agriculture, the mechanisms underlying the interactions between NPs and heavy metal on their uptake, accumulation, and phytotoxicity in crops are still not fully understood. Therefore, the impact of TiO2 NPs (0, 100, 250 mg/L) and Cd (0, 50 µM) co-exposure on hydroponic maize (Zea mays L.) was determined under two exposure modes. Results showed that root co-exposure to TiO2 NPs and 100 mg/L Cd significantly enhanced Cd uptake and produced greater phytotoxicity in maize than foliar exposure to TiO2 NPs. Meanwhile, plant dry weight and chlorophyll content showed a reduction of 45.3% and 50.5%, respectively, when compared with single Cd treatment. In addition, the accumulation of Ti in shoots and roots increased by 1.61 and 4.29 times, respectively when root exposure to 250 mg/L TiO2 NPs. By contrast, foliar exposure of TiO2 NPs could markedly decrease shoot Cd contents from 15.2% to 17.8% and had a stronger influence on alleviating Cd-induced toxicity via increasing superoxide dismutase (SOD) and glutathione S-transferase (GST) activities and upregulating several metabolic pathways, including galactose metabolism and citrate cycle, alanine, aspartate and glutamate metabolism, as well as glycine, serine and threonine metabolism. This study provides a new strategy for the application of TiO2 NPs in crop safety production in Cd contaminated soils.

Depletion of chlortetracycline during composting of aged and spiked manures.

Chlortetracycline (CTC) is one of the most important pharmaceuticals occurring in the environment. An increase of its application as feed supplement for livestock and poultry in the world leads to a substantial CTC contamination of manures, because most of the CTC is excreted to manure. The simulation experiment of aerobic composting was adopted to investigate CTC depletion in aged and spiked manure composting, and to address the extent of CTC depletion during composting. The results showed that the extractable CTC initial concentration was markedly different between the different manures, with 94.71mgkg(-1) in broiler manure and 879.6mgkg(-1) in hog manure. The concentration of extractable CTC decreased rapidly at the initial stage of composting, and subsequently declined slowly during aged and spiked manure composting. At the end of composting, more than 90% of CTC in the manure composting process (42 days) was depleted, except for hog manure composting with a removal of only 27%. The CTC half-lives were 11.0 days in broiler manure, 86.6 days in hog manure, 12.2 days in layer-hen manure (150.3mgkg(-1) CTC), 12.0 days in layer-hen manure (100.0mgkg(-1) CTC) and 4.39 days in layer-hen manure (53.10mgkg(-1) CTC), all according to the first order kinetics. The significance of experimental parameters in CTC depletion was assessed by the Pearson correlation approach. Microbial degradation of CTC was not effective from manure composting. CTC depletion was in good correlation with total organic carbon, total nitrogen, total phosphorus, C/N, N/P and total heavy metals.

Citric acid and glycine reduce the uptake and accumulation of Fe2O3 nanoparticles and oxytetracycline in rice seedlings upon individual and combined exposure.

Uptake of nanoparticles and antibiotics by plants is root exudates-dependent, however, the underlying influence processes and mechanisms from different root exudates are rarely investigated. A hydroponic experiment was conducted to investigate the accumulation of Fe2O3 nanoparticle (NP) and oxytetracycline (OTC) in rice seedlings, in the absence or presence of citric acid or glycine, acting as components of root exudates. Irrespective of individual or combined exposure of Fe2O3 NP and OTC, citric acid and glycine both reduced surface-Fe, surface-OTC, root-OTC, shoot-OTC accumulations with dose-effect relationship. Two exudates increased |ζ| values of NP, which weakened the interactive attraction between NP and root surface and then decreased surface-Fe accumulation. Citric acid and glycine binding with OTC in solution decreased surface-OTC accumulation, and further decreased root-OTC and shoot-OTC accumulations. Combined exposure of two pollutants alleviated the reduction effect of citric acid and glycine on surface-Fe/surface-OTC/root-OTC accumulations due to their high accumulations in combined exposure compared to individual exposure. Although citric acid and glycine promoted TFroot-shoot and TFsurface-root of two pollutants, respectively, they always decreased total rice-Fe and rice-OTC accumulations. Therefore, the presence of root exudates decreased the bioaccumulation of Fe2O3 NP and OTC in rice upon their individual and combined exposure through changing their environmental behaviors in rhizosphere.

Iron plaque reduces cerium uptake and translocation in rice seedlings (Oryza sativa L.) exposed to CeO2 nanoparticles with different sizes.

This study aims to assess the role of iron plaque (IP) on cerium (Ce) uptake and translocation by rice after CeO2 nanoparticles (NPs) exposure over a 4 days period. A hydroponic experiment was performed under two IP levels (low and high) combined with two CeO2 NPs size (14 nm and 25 nm). It was found that CeO2 NPs as the main form was absorbed by rice due to limited NPs dissolution in hydroponic solution. IP significantly reduced surface-Ce, root-Ce and shoot-Ce accumulation, irrespective of CeO2 NPs sizes. The reduced uptake of Ce was more obvious in NP25 than NP14. Ce accumulations decreased with increasing IP amounts. In IP treatments, the interactive attraction between NPs and root surface was weakened through the enhancement of hydrodynamic diameters and the reduction of ζ-potential of CeO2 NPs in solution, as well as the reduction of |ζ| values of rice root, which reduced the Ce bioaccumulation in rice. PCA indicated the negative correlation between surface-Ce (IP-C-Ce and IP-A-Ce) and NPs size, and between shoot-Ce/root-Ce and IP-Fe/tissue-Fe. IP also decreased Ce translocation from root to shoot. A full life study indicated the reduction effect of IP on surface-Ce, root-Ce, shoot-Ce and grain-Ce accumulations. These findings are significant as they imply that the IP formation is a promising approach for preventing Ce accumulation in rice, which would regulate Ce uptake by rice in the following growth stages and decrease the health risk of CeO2 NPs exposure in agricultural environment.

Influence of the root plaque formation with different species on oxytetracycline accumulation in rice (Oryza sativa L.) and its elimination in culture solution.

Hydroponic experiments were conducted to investigate the role of different root plaque formation on oxytetracycline (OTC) uptake/translocation by rice seedlings (Oryza sativa L.) and solution-OTC elimination at two initial OTC concentrations (10 and 30 mg L-1). The results indicated OTC accumulation in rice was always in the order root surface > shoot > inside root whether plaques were formed or not. It demonstrated that Fe-Mn-Mt (montmorillonite) treatment was easier to promote significantly (p < 0.05) OTC accumulation in the underground part (root surface and inside root) and decrease significantly (p < 0.05) OTC translocation from the root to the shoot in rice compared to no plaque treatments (CK), especially for OTC 30 mg L-1 level with the lowest shoot-OTC accumulation in Fe-Mn-Mt treatment. Plaque treatments increased half-life of solution-OTC elimination in the order Fe-Mn-Mt > Fe-Mn > Fe > CK, which was caused mainly by OTC degradation from Fe2+-binding influence in solution, not by the enhancement of OTC accumulation on the root surface and inside root. And solution-OTC elimination increased with decreasing initial OTC concentrations, the drop of Fe2+ and the increment of Fe3+ and pH during the experiment. These findings are useful for reducing OTC accumulation and translocation in rice aboveground parts and eliminating OTC contamination in agricultural environment simultaneously through complicated plaque formation under higher OTC concentration exposure (30 mg L-1) in the future design.

Allantoin-N concentration changes and analysis of the influencing factors on its changes during different manure composting.

Allantoin is one of important nitrogenous compounds in manure. In this study, the simulation experiment of aerobic composting was adopted to explore concentration changes, degradation and relevant influencing factors of allantoin-N during six manure composting. The result showed that the allantoin-N concentration was markedly different among different manures. The various livestock and poultry excreted 1.92-11.14gkg(-1) allantoin-N which accounted for 9.98-32.27% of the total excreted nitrogen. The changing trend of the allantoin-N concentration firstly increased (for 0-14 days), then decreased (for 14-70 days) during different manure composting, and the allantoin-N concentration after composting was lower than the initial allantoin-N concentration in all manure composting. During allantoin degradation for 14-70 days of composting, the half-life of allantoin-N was 57.76 days in broiler manure, 46.21 days in layer-hen manure, 27.73 days in hog manure, 25.67 days in sow manure, 38.51 days in young pig manure and 15.75 days in dairy manure, and the sequence in the half-life was chicken manure>pig manure>dairy manure. Allantoin degradation conformed to first-order kinetics. Through the correlation analysis, hippuric acid, hydrolyzable nitrogen, amino acid-nitrogen, HUN fraction, NO(3)(-)-N and total hydrolyzable nitrogen could be closely related to allantoin-N transforming during composting. Humification could be the main influencing factor for reducing allantoin-N concentration during composting.