Understanding Salinity-Driven Modulation of Microbial Interactions: Rhizosphere versus Edaphic Microbiome Dynamics.

Soil salinization poses a global threat to terrestrial ecosystems. Soil microorganisms, crucial for maintaining ecosystem services, are sensitive to changes in soil structure and properties, particularly salinity. In this study, contrasting dynamics within the rhizosphere and bulk soil were focused on exploring the effects of heightened salinity on soil microbial communities, evaluating the influences shaping their composition in saline environments. This study observed a general decrease in bacterial alpha diversity with increasing salinity, along with shifts in community structure in terms of taxa relative abundance. The size and stability of bacterial co-occurrence networks declined under salt stress, indicating functional and resilience losses. An increased proportion of heterogeneous selection in bacterial community assembly suggested salinity's critical role in shaping bacterial communities. Stochasticity dominated fungal community assembly, suggesting their relatively lower sensitivity to soil salinity. However, bipartite network analysis revealed that fungi played a more significant role than bacteria in intensified microbial interactions in the rhizosphere under salinity stress compared to the bulk soil. Therefore, microbial cross-domain interactions might play a key role in bacterial resilience under salt stress in the rhizosphere.

[Pollution Characteristics and Risk Assessment of PAHs in the Soil of Wild Forsythia Suspensa in Shanxi].

Shanxi is one of the main producing areas of Forsythia suspensa in China. In order to explore the safety of the soil in the areas where Forsythia suspensa grows,70 surface (0-25 cm) soil samples were collected from the main growing areas of F. suspensa in the eastsouth of Shanxi Province in July 2017. The concentration and composition characteristics of 16 polycyclic aromatic hydrocarbons (PAHs) in the sample soils were analyzed using chemical extraction and gas chromatography-mass spectrometry (GC-MS). The diagnostic ratio method was used to determine the source of PAHs in the areas. The potential ecological risk was assessed by using the method of calculating the equivalent carcinogenic concentration of benzo[a]pyrene. The results showed that the average concentration of total PAHs (Σ16PAHs) in all of the soil samples was 1.85 µg·g-1, which was dominated by three ring number PAHs, accounting for 76.7% of the total PAHs. The detection rates of phenanthrene (Phe) and anthracene (Ant) were both 100% of all the sample sites. The soil PAHs in the wild F. suspensa growing areas mainly originated from coal, biomass burning, and motor vehicle exhaust emissions, which resulted from air transport and sedimentation pathways. In all of the sample sites, the concentration of Σ16PAHs the limit standard level (0.2 µg·g-1) of Maliszewska-Kordybach for agricultural soil pollution and exceeded the soil heavy pollution level limit value (1.0 µg·g-1) in 41.4% of the sample sites. The concentration of BaP was above the risk control standard for soil contamination of agricultural land (0.55 µg·g-1) in 10% of all the soil samples. A total of 11.4% of the sample soil ΣBaPeq16PAHs and ΣBaPeq8BPAHs exceeded the agricultural soil screening value (0.55 µg·g-1). These results indicate that the contamination of PAHs was at a detectable level in the soil of wild F. suspensa growing in Shanxi, and thus their potential ecological risks should not be ignored. It is necessary to enhance the research regarding these areas to ensure the safe production of medicinal plants.

Toxicity evaluation of polycyclic aromatic hydrocarbons (PAHs) in soils of coal chemical industry areas, North China.

Objectives of this study were to investigate the concentrations, distributions, toxicities, and risk assessment of 16 polycyclic aromatic hydrocarbons in surface soils surrounding a coal chemical industrial zone in the southeast of Shanxi province, China. A total of 52 topsoil samples were collected from different land-use areas: cereal agriculture, roadsides, and parkland. Results show that the total PAHs (∑16PAHs) ranged from 3.87 × 103 to 116 × 103 µg kg-1 and that the total carcinogenicity PAHs (∑BPAHs) ranged from 3.11 × 103 to 94.2 × 103 µg kg-1, with the highest concentration of ∑16PAHs noted in the RS samples, followed by PS and AS. The entire risk quotient of all PAH maximum permissible concentrations (RQ∑PAHMPCi) was greater than 1.0, and the minimum concentration entire risk quotient (RQ∑PAHNCi) of 84.3% of all samples was higher than 800. The value of the total toxicity equivalent concentration of PAH (PAHBapeq) for areas surrounding the coal chemical industrial zone was higher than the value of the standard level, and the incremental lifetime cancer risk (ILCR) far exceeds the U.S. EPA's risk standard. The toxic properties of PAHs indicated that the soils in the survey areas have a high risk to human health and the environment.

[Evaluation of the Potential Agricultural Risks of Polycyclic Aromatic Hydrocarbon Contaminated Soil by Planting Lactuca sativa L.]

In order to evaluate the potential agricultural risks of soil contaminated by polycyclic aromatic hydrocarbons (PAHs), Lactuca sativa L. was used as a model leaf vegetable plant to investigate the enrichment characteristics of PAHs in the different tissues of Lactuca sativa L, such as its underground parts (GS) and aboveground parts (YS), which were studied through an experiment involving potted cultivation in PAHs contaminated soil that was taken from the agricultural soil around a coking enterprise area. The concentrations of the different PAHs in the soil and plant tissues were analyzed using ultrasonic oscillation extraction and high-performance liquid chromatography-mass spectrometry (GC-MS) analysis methods. The results show that the enrichment of the total PAHs (Σ16PAHs) in the YS is higher than that in the GS. The components enriched in the YS mainly consist of 3-5 ring PAHs, and those in the GS consist of 4-6ring PAHs. The coefficients of the different PAHs enriched in the YS were higher than those of the GS. The enrichment coefficient of anthracene (Ant) was the largest and that of fluoranthene (Fla) was the smallest in the YS, while the enrichment coefficient of benzene[a]pyre (Bap) was the largest and that of Fla was the smallest in the GS. The transfer coefficients of the different PAHs from the GS to the YS were greater than the rate from the initial soil (SS) to the GS; the value is less than 1 from the SS to GS. The correlations and goodness of fit were analyzed for the concentrations of PAHs in the SS, GS and YS. The Σ16PAHs in the SS showed positive correlations with the Σ16PAHs in the YS and in GS. The goodness of fit of the correlation of the PAHs in YS to those in the SS was the largest (R2=1.0), while the goodness-of-fit for the correlation between the GS and SS was lower (R2=0.71). The benzo[a]pyrene equivalent concentration values (Σ16PAHsBapeq) of YS and GS were 11.8 and 12.7 times the maximum value of Bap level allowed in food. The study indicates that contaminated farmland soil would present a high health risk when it was used to grow the plant.

Distributions and Sources of Polycyclic Aromatic Hydrocarbons (PAHs) in Soils around a Chemical Plant in Shanxi, China.

Background: Yearly the Shanxi coal chemical industry extracts many coal resources, producing at the same time many polycyclic aromatic hydrocarbons (PAHs) that are emitted as by-products of coal incomplete combustion. Methods: Sixty-six soil samples collected from 0 to 100 cm vertical sections of three different agricultural (AS), roadside (RS) and park (PS) functional soils around a chemical plant in Shanxi, China were analyzed for the presence of the 16 priority control PAHs. Results: The total concentrations (∑16PAHs) varied in a range of 35.4-116 mg/kg, 5.93-66.5 mg/kg and 3.87-76.0 mg/kg for the RS, PS and AS surface soil, respectively, and 5-ring PAHs were found to be dominant (44.4-49.0%), followed by 4-ring PAHs (15.9-24.5%). Moreover, the average value of ∑16PAHs decreased with the depth, 7.87 mg/kg (0-25 cm), 4.29 mg/kg (25-50 cm), 3.00 mg/kg (50-75 cm), 2.64 mg/kg (75-100 cm) respectively, in PS and AS soil vertical sections. Conclusions: The PAH levels in the studied soils were the serious contamination level (over 1.00 mg/kg) according to the Soils Quality Guidelines. The carcinogenic PAHs (ΣBPAHsBapeq) were approximately 14.8 times higher than the standard guideline level (0.60 mg/kg) and 90.3% of PAHs were produced by coal/wood/grass combustion processes.

Distribution, sources, and potential risk of polycyclic aromatic hydrocarbons in soils from an industrial district in Shanxi, China.

Concentration, composition profile, orientation distribution, sources, and potential risks of 16 polycyclic aromatic hydrocarbons (PAHs) were analyzed in 76 surface (0-25 cm) soil samples collected from the Changzhi industrial district in July 2014 using a gas chromatography mass spectrometer (GC-MS QP2010 Ultra) system. The composition patterns of the PAHs were dominated by the presence of four-ring PAHs (average 42.9%), followed by three-ring (average 25.9%), five-ring PAHs (average 25.6%), two-ring PAHs (average 5.03%), and lastly, six-ring PAHs (average 0.641%). Source apportionment of the soil PAHs was also performed by the diagnostic ratios, principal component analysis (PCA), and coefficient of divergence (CD) analysis indicated signatures of PAHs sources (including incineration, coal/wood combustion, and vehicular exhaust emission). The total concentration of 16 PAHs (∑16PAHs) found in the roadsides soils (RS) ranged from 2197 to 25,041 µg kg-1, with an arithmetic mean value of 12,245 µg kg-1; followed by the village soils (VS), which ranged from 2059 to 21,240 µg kg-1, with a mean of 8976 µg kg-1; and lastly, the agricultural soils (AS), which ranged from 794 to 16,858 µg kg-1, with a mean of 3456 µg kg-1. According to the numerical effect-based soils quality guidelines of Maliszewska-Kordybach, the levels of PAHs in the sampled industrial areas range from high to heavy contamination. The values of total benzo[a]pyrene toxicity equivalent values (∑Bapeq16PAHs) in the sample areas ranged from 0.087 to 3611 µg kg-1 with an average of 969 µg kg-1. According to the soil quality guidelines of Canada, values found in the highest range (100 µg kg-1), which are equal to those of ∑Bapeq16PAHs found in the industrial area samples, will exert adverse biological effects. The results of this research could potentially be useful for local governments to control toxicity exposure, promote actions to alleviate PAHs contamination, and to manage human health at both work and industrial areas.

Bioremediation of petroleum hydrocarbon contaminated soil by Rhodobacter sphaeroides biofertilizer and plants.

Bio-augmentation is a promising technique for remediation of polluted soils. This study aimed to evaluate the bio-augmentation effect of Rhodobacter sphaeroides biofertilizer (RBF) on the bioremediation of total petroleum hydrocarbons (TPH) contaminated soil. A greenhouse pot experiment was conducted over a period of 120 days, three methods for enhancing bio-augmentation were tested on TPH contaminated soils, including single addition RBF, planting, and combining of RBF and three crop species, such as wheat (W), cabbage (C) and spinach (S), respectively. The results demonstrated that the best removal of TPH from contaminated soil in the RBF bio-augmentation rhizosphere soils was found to be 46.2%, 65.4%, 67.5% for W+RBF, C+RBF, S+RBF rhizosphere soils respectively. RBF supply impacted on the microbial community diversity (phospholipid fatty acids, PLFA) and the activity of soil enzymes, such as dehydrogenase (DH), alkaline phosphatase (AP) and urease (UR). There were significant difference among the soil only containing crude oil (CK), W, C and S rhizosphere soils and RBF bio-augmentation soils. Moreover, the changes were significantly distinct depended on crops species. It was concluded that the RBF is a valuable material for improving effect of remediation of TPH polluted soils.

[Running Condition and Bacterial Community Associated with the Partial Nitritation System].

In partial nitritation process, the sludge concentration was higher than 4000 mg x L(-1), DO was less than 0.2 mg x L(-1), the temperature of 15-29 degrees C, the reactor HRT of 4.6 h, and the circulation ratio was 75%, not only the microbial biomass reached the highest value but also the ratio of nitrite to ammonium of the effluent could be controlled at approximate 1.0 by adjusting the dissolved oxygen concentration. A quantitative PCR and the 16S rRNA genes clone library results demonstrated that ammonia-oxidizing bacteria were the dominant among nitrite-oxidizing bacteria at low dissolve oxygen concentration, that the bacteria promoted the running of the partial nitritation. Compared with conventional nitrification systems, in partial nitritation process, Nitrobacter and Nitrospira could not be detected among the system, and abundance of Planctomycetes was higher in partial nitritation process than that of conventional nitrification systems. Phylogenetic analysis of bacterial amoA gene sequences suggested that ammonia-oxidizing bacteria of the partial nitritation system was dominated by Nitrosomonas sequences, so partial nitritation is to be feasible technically and economically.

Polycyclic aromatic hydrocarbons in the dagang oilfield (china): distribution, sources, and risk assessment.

The levels of 16 polycyclic aromatic hydrocarbons (PAHs) were investigated in 27 upper layer (0-25 cm) soil samples collected from the Dagang Oilfield (China) in April 2013 to estimate their distribution, possible sources, and potential risks posed. The total concentrations of PAHs (∑PAHs) varied between 103.6 µg·kg(-1) and 5872 µg·kg(-1), with a mean concentration of 919.8 µg·kg(-1); increased concentrations were noted along a gradient from arable desert soil (mean 343.5 µg·kg(-1)), to oil well areas (mean of 627.3 µg·kg(-1)), to urban and residential zones (mean of 1856 µg·kg(-1)). Diagnostic ratios showed diverse source of PAHs, including petroleum, liquid fossil fuels, and biomass combustion sources. Combustion sources were most significant for PAHs in arable desert soils and residential zones, while petroleum sources were a significant source of PAHs in oilfield areas. Based ontheir carcinogenity, PAHs were classified as carcinogenic (B) or not classified/non-carcinogenic (NB). The total concentrations of carcinogenic PAHs (∑BPAHs) varied from 13.3 µg·kg(-1) to 4397 µg·kg(-1) across all samples, with a mean concentration of 594.4 µg·kg(-1). The results suggest that oilfield soil is subject to a certain level of ecological environment risk.

[Influence of Mirabilis jalapa Linn. Growth on the Microbial Community and Petroleum Hydrocarbon Degradation in Petroleum Contaminated Saline-alkali Soil].

In order to explore the effect of Mirabilis jalapa Linn. growth on the structure characteristics of the microbial community and the degradation of petroleum hydrocarbon (TPH) in the petroleum-contaminated saline-alkali soil, Microbial biomass and species in the rhizosphere soils of Mirabilis jalapa Linn. in the contaminated saline soil were studied with the technology of phospholipid fatty acids (PLFAs) analysis. The results showed that comparing to CK soils without Mirabilis jalapa Linn., the ratio of PLFAs species varied were 71. 4%, 69. 2% and 33. 3% in the spring, summer and autumn season, respectively. In addition, there was distinct difference of the biomasses of the microbial community between the CK and rhizosphere soils and among the difference seasons of growth of Mirabilis jalapa Linn.. Compare to CK soil, the degradation rates of total petroleum hydrocarbon (TPH) was increased by 47. 6%, 28. 3%, and 18. 9% in spring, summer, and autumn rhizosphere soils, respectively. Correlation analysis was used to determine the correlation between TPH degradation and the soil microbial community. 77. 8% of the total soil microbial PLFAs species showed positive correlation to the TPH degradation (the correlation coefficient r > 0), among which, 55. 6% of PLFAs species showed high positive correlation(the correlation coefficient was r≥0. 8). In addition, the relative content of SAT and MONO had high correlation with TPH degradation in the CK sample soils, the corelation coefficient were 0. 92 and 0. 60 respectively; However, the percent of positive correlation was 42. 1% in the rhizosphere soils with 21. 1% of them had high positive correlation. The relative content of TBSAT, MONO and CYCLO had moderate or low correlation in rhizosphere soils, and the correlation coefficient were 0. 56, 0. 50, and 0. 07 respectively. Our study showed that the growth of mirabilis Mirabilis jalapa Linn. had a higher influence on the species and biomass of microbial community in the rhizosphere soils, and the results will provide a basis theory for the research of phytoremediation petroleum contaminated saline soil.

[Comparison between transgenic insect-resistant cotton expressing Cry1Ac protein and its parental variety in rhizospheric fungal diversity].

The dynamics of rhizospheric fungal diversity and biomass at different sampling stages associated with two transgenic insectresistant cottons expressing Cry1Ac protein and their control varieties were studied under greenhouse conditions, followed by PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative real-time polymerase chain reaction (Q-PCR), in order to evaluate the ecological security of planting transgenic cotton expressing Cry1Ac protein. The results indicated that the fungal superior bands in rhizosphere of transgenic Bt cotton were similar with that of control cotton at four sampling stages, the more obvious difference in the blurred bands among transgenic Bt cotton, JM20 and SHIYUAN321 was detected. The rhizospheric fungal biomass of transgenic Bt cotton SGK321 was significantly lower than that of its parental control cotton at seedling stage, while the slight decrease in fungal biomass of transgenic Bt cotton XP188 was detected at boll forming stage, the ill-defined decrease, even growing tendency in two transgenic Bt cottons was detected at other stages. However, the difference of rhizospheric fungal community compositions and biomass was not only existed between transgenic cotton and its control, but also between SHIYUAN321 and JM20, and the same phenomenon was also detected between transgenic Bt cotton SGK321 and XP188. Hence, Bt protein is not the only incentive resulting in the difference in fungal community composition and diversity, the decrease in biomass between transgenic cotton and untransgenic cotton, different cotton varieties has an effect on them.