Adsorption of oxytetracycline on subalpine meadow soil from Zoige Plateau, China: Effects of the coexisting Cu2.

Subalpine meadow soil with high moisture and humus content is a unique soil type in the Zoige Plateau. Oxytetracycline and copper are common soil contaminants which interact to form compound pollution. Oxytetracycline's adsorption on natural subalpine meadow soil and its components (humin and the soil without iron and manganese oxides) was studied in the laboratory with and without the presence of Cu2+. The effects of temperature, pH and Cu2+ concentration were documented in batch experiments, allowing deduction of the main sorption mechanisms. The adsorption process had two phases: one rapid, taking place in the first 6 h, and another slower, reaching equilibrium at around 36 h. The adsorption kinetics were pseudo-second-order, and the adsorption isotherm conformed to the Langmuir model at 25 °C. Higher concentrations oxytetracycline increased the adsorption, but higher temperature did not. The presence of Cu2+ had no effect on the equilibrium time, but the amount and rate adsorbed were much greater with Cu2+ concentration increased (except for the soil without iron and manganese oxides). The amounts adsorbed with/without Cu2+ were in the order the humin from subalpine meadow soil (7621 and 7186 µg/g) > the subalpine meadow soil (7298 and 6925 µg/g) > the soil without iron and manganese oxides (7092 and 6862 µg/g), but the difference among those adsorbents was slight. It indicates that humin is a particularly important adsorbent in the subalpine meadow soil. The amount of oxytetracycline adsorbed was greatest at pH 5-9. In addition, Surface complexation through metal bridging was the most important sorption mechanism. Cu2+ and oxytetracycline formed positively-charged complex that was adsorbed and then formed a ternary complex "adsorbent-Cu(II)-oxytetracycline", in which Cu2+ acted as a bridge. These findings provide a good scientific basis for soil remediation, and for assessing environmental health risks.

Skermanella pratensis sp. nov., isolated from meadow soil, and emended description of the genus Skermanella.

A novel Gram-stain-negative, light pink-coloured, short rod-shaped, designated strain W17T, was isolated from a meadow soil sample collected from Xinjiang, PR China. The 16S rRNA gene sequence analysis indicated that strain W17T was related most closely to Skermanella rosea M1T (98.72 %) and Skermanella mucosa 8-14-6T (98.44 %). However, strain W17T showed a low level of DNA-DNA relatedness to S. rosea M1T (32.4±2.6 %) and S. mucosa 8-14-6T (33.5±0.1 %). The genome size of the novel strain was 5.87 Mb and the genomic DNA G+C content was 67.27 mol%. The only respiratory quinone of strain W17T was Q-10. Diphosphatidylglycerol, phosphatidylglycerol. phosphatidylethanolamine and phosphatidylcholine were the major polar lipids. The predominant cellular fatty acids were C18 : 1ω6c and/or C18 : 1ω7c (48.53 %), C16 : 0 (20.88 %) and C18 : 0 (14.92 %). The phylogenetic, phenotypic and chemotaxonomic data showed that strain W17T represents a novel species of the genus Skermanella, for which the name Skermanella pratensis sp. nov. is proposed. The type strain is W17T (=GDMCC 1.1392T=KCTC 62434T).

Ornithinimicrobium pratense sp. nov., isolated from meadow soil.

A novel Gram-stain-positive, yellow, short-rod-shaped or coccoid bacterial strain, W204T, was isolated from a soil sample collected from Jiadengyu national forest park in China and characterized using a polyphasic approach. The cell-wall peptidoglycan contained ornithine as the diagnostic diamino acid. 16S rRNA gene sequence analysis indicated that strain W204T was closely related to Ornithinimicrobium flavum CPCC 203535T (97.4 %, similarity), Serinicoccus profundi CGMCC 4.5582T (96.9 %), Serinicoccus sediminis GP-T3-3T (96.8 %), Serinicoccus hydrothermalis JLT9T (96.7 %), Ornithinimicrobium cerasi CPCC 203383T (96.6 %) and Ornithinimicrobium kibberense K22-20T (96.6 %). However, the digital DNA-DNA genome hybridization value between strain W204T and the closest related strain O. flavum CPCC 203535T was 21.90 %. Complete genome analyses revealed that the size of the genome was 3.54 Mb and the genomic DNA G+C content was 70.79 mol%. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, an unidentified glycolipid, an unidentified phospholipid and an unidentified lipid. The major menaquinone was MK-8(H4). The predominant cellular fatty acids were iso-C15 : 0, anteiso-C15 : 0 and C16 : 0. The phenotypic, chemotaxonomic and phylogenetic data suggested that strain W204T should be classified as representative of a novel species of the genus Ornithinimicrobium, for which the name Ornithinimicrobium pratense sp. nov. is proposed. The type strain is W204T (=GDMCC 1.1391T=KCTC 49237T).

Unraveling the Impact of Long-Term Rice Monoculture Practice on Soil Fertility in a Rice-Planting Meadow Soil: A Perspective from Microbial Biomass and Carbon Metabolic Rate.

Global agricultural intensification leads to a decline in soil quality; however, the extent to which long-term rice cultivation adversely impacts soil, based on chemical and microbial perspectives, remains unclear. The present study was conducted on a seed multiplication farm in Wuchang, Heilongjiang Province, China, to quantify changes in the nutrient properties and microbial profiles of meadow soil in cultivated (rhizosphere and bulk soil) and uncultivated paddy plots from spring to winter. A non-parametric method was used to compare carbon metabolism characteristics among the three groups of soil samples. Principal component analysis was used to distinguish soil chemical properties and carbon source utilization profiles among the soil samples across different seasons. Under rice cultivation, pH, organic matter, total nitrogen, and alkali-hydrolyzed nitrogen concentrations were generally higher in rhizosphere soils than in bulk or uncultivated soils. However, microbial biomass in cultivated soils was consistently lower than in uncultivated soils. There was a discernible difference in carbon substrate preference between summer and other seasons in the three sample groups. In conclusion, agricultural activities in rice cultivation could reshape soil microbial communities in the long term. Notably, specific cultivation activity may induce distinct soil microbial responses, which are more sensitive than chemical responses.

Evaluation of soil and water conservation function in the Wugong mountain meadow based on the comprehensive index method.

Wugong Mountain meadow landscape is well-known both at home and abroad because of its ornamental value. Our study aimed to comprehensively evaluate the function of soil and water conservation at different altitudes of Wugong Mountain meadow soil. The hydro-physical characteristics, including the soil bulk density, porosity, water content, water holding capacity, and permeability of meadow soil at 1600 m-1900 m altitudes, were analyzed. The results showed that the mountain meadow soil's hydro-physiological characteristics and water conservation function significantly differed with altitude. However, the trend of each index did not follow the same law with altitude change. There was a decrease in bulk density of the soil from 1700 m to 1900 m, but a significant increase in porosity and water-holding capacity. Despite the higher porosity and water holding capacity found at 1600 m than at 1700 m and 1800 m, a similar bulk density was found at 1600 m as 1700 m. In addition, the bulk density in the 0-20 cm layer was lower than that in the 20-40 cm layer, while the porosity and water-holding capacity were higher. A higher sequence of soil water conservation capacity was found in soil layers 0-20 cm depth at 1900, 1600, 1800, and 1700 m; in soil layers 20-40 cm depth, it was at 1900, 1800, 1700, and 1600 m. The study found that the sequence of the comprehensive performance of soil water conservation function was at 1900, 1600, 1800, and 1700 m altitudes in the Wugong mountain meadow area. Our comprehensive study of soil water conservation capacity provides a theoretical basis for the rational use of mountain meadow resources in subtropical regions.

[Effects of soil moisture on priming effect of soil organic carbon in meadow in Wuyi Mountain, China.] / 水分对武夷山草甸土壤有机碳激发效应的影响.

Moisture is an important factor affecting the priming effect of soil organic carbon (SOC). However, empirical evidence for its effect in mountain meadows soil is lacking. We conducted a 126-day laboratory incubation experiment with the high altitude (2130 m) mountain meadow soil in Wuyi Mountain, by adding 13C-labelled glucose combined with controlling soil moisture (30% and 60% of field water capacity, FWC). The CO2 concentration and 13C-CO2 abundance were measured regularly to examine the differences of SOC mineralization and priming effects under different water conditions and the driving factors. Our results showed that SOC mineralization rate increased with increasing soil water content. The priming effect of meadow soil with different soil moisture showed a decreasing trend with the increases of incubation time. The priming effect in soils with low FWC soil was significantly greater than that with high FWC. At the end of incubation, the cumulative priming effect of low FWC soil was 61.4% higher than that of high FWC soil. Compared with low FWC soil, high FWC soil released more CO2 from glucose, and the ratio of cumulative primed carbon to glucose mineralization under low FWC was significantly higher than that under high FWC soil, indicating that soil microorganisms under the high FWC condition might preferentially mineralize more glucose than SOC and consequently lower priming effect. Therefore, the priming effect under high FWC was smaller than that under low FWC. There was a significant positive relationship between priming effect and microbial biomass carbon, microbial biomass carbon/microbial biomass nitrogen, and NH4+-N, indicating that soil microbial biomass and composition could be changed under low FWC condition. The improved microbial "nitrogen-mining" would increase priming effect. Consequently, the decline of soil moisture of mountain meadow induced by global climate change may increase the priming effect of carbon, with consequences on carbon loss.

Galena weathering in simulated alkaline soil: Lead transformation and environmental implications.

Alkaline soils are widely distributed around the world. During the mining and transportation processes galena may be exposed to the alkaline soils. Weathering of galena may lead to the formation of different lead phases having higher bio-accessibility than galena, and thereby increasing the mobility and toxicity of lead. In this study, electrochemical techniques and Raman spectroscopic measurements were used for the evaluation of the interfacial processes that are involved in the galena weathering under the conditions of simulated saline soil and meadow soil solutions. The results showed that the release of Pb2+ and S0 took place during initial stage of the oxidation. Thereafter, further transformation to anglesite would take place, even leading to the transformation to ß-PbO and α-PbO at higher temperatures. Galena weathering prone to saline soil than that in meadow soil, and has a faster weathering rate in the saline soil at same ambient temperature. Higher temperatures was found to promote the weathering of galena, and the rate constant for the release of Pb (II) was approximate 10-9 to 10-8 mol∙m-2∙s-1, while surface reaction was found to control the weathering kinetics. Based on the surface characterization and evaluation of the thermodynamic and kinetic parameters, the weathering mechanism of galena in the alkaline soil and its environmental implications was suggested.

Effects of elevation and slope aspect on the distribution of the soil organic carbon associated with Al and Fe mineral phases in alpine shrub-meadow soil.

Mountain ecosystems store a large amount of soil organic carbon (SOC) sensitive to global climate change. The SOC associated with Al and Fe minerals is important for SOC retention because of the ubiquitous nature and highly reactive surface properties of these minerals. Topography is also known to impact the distribution and transformation of SOC by creating different microclimates. However, the effect of topography on the distribution of organo-mineral associations has seldom been reported. This study uses a selective dissolution method to quantify the soil carbon (C) fractions associated with Al and Fe minerals in alpine shrub-meadow soil. Na-pyrophosphate (PP), HCl-hydroxylamine (HH) and dithionite-HCl (DH) were used to quantify organo-metal complexes, SOC associated with short-range order (SRO) phases and crystalline phases, respectively. Results suggest that the Al and Fe mineral-associated C accounted for a small proportion of SOC (less than 30%) in each extraction. A higher concentration coupled with a lower percentage of SOC was found in the A horizon compared to the B horizon. A significant correlation was observed between Fe and C in PP and HH extractions, whereas Al was significantly correlated with C in DH extractions. Elevation and slope aspect strongly influenced soil biotic and abiotic parameters, as well as organo-mineral associations. The C fractions extracted by PP and HH were significantly higher in the NE slope aspect than the SW slope aspect. These fractions were positively correlated with soil water content and negatively correlated with soil pH. The C fractions extracted using DH decreased with increasing elevation and were positively correlated with DH extractable Al. Our results highlight the role of topography on the distribution of organo-mineral associations, which should be considered during the assessment of SOC stability in alpine soils.

[Effect of long-term straw mulching and no-tillage on physical properties of meadow soil in cold region.] / é•¿æœŸå è€•ç§¸ç§†è¦†ç›–å¯¹å¯’åœ°è‰ç”¸åœŸåœŸå£¤ç‰©ç†æ€§è´¨çš„å½±å“.

The effects of different straw returning technology and farming system on soil physical properties is not clear in Heilongjiang Province, which is located in middle temperature zone with large amount of straw. Here, the effects of straw mulching on soil physical properties in meadow soil under no tillage conditions were studied in field experiments for eight consecutive years (2010-2017). The no straw covering (0%), 30% coverage (30%), 60% coverage (60%) and 100% coverage (100%) were disposed in the experiment. The results showed that straw mulching under no tillage significantly increased soil bulk density by 0.10-0.20 g·cm-3, which increased with the increases of coverage amount. Straw mulching increased soil solid fraction by 2.5%-7.8%. Soil temperature decreased with the increases of coverage amount, and this trend was more apparent on the surface of soil. The temperature reduction in 0-5 cm soil layer was 1.87-2.90 ℃. Soil water content significantly increased with the increases of straw mulching, with an enhancement of 6.4%-10.2%. Straw mulch decreased the total porosity and diameter of >0.05 mm aeration pores, increased the effective pore size of 0.05-0.002 mm, with the magnitude of such effects being positively dependent on coverage amount. There was no significant effect of straw mulching on inactive porosity of soil. Long-term straw mulching increased soil compaction and soil moisture, reduced soil temperature and total soil porosity, and increased soil available porosity in 0-5 cm soil layer.