Impact of wetting-drying cycles and acidic conditions on the soil aggregate stability of yellow‒brown soil

Soil aggregate is the basic structural unit of soil,which is the foundation for supporting ecosystem functions,while its composition and stability is significantly affected by the external environment.This study was conducted to explore the effect of external environment(wetting-drying cycles and acidic conditions)on the soil aggregate distribution and stability and identify the key soil physicochemical factors that affect the soil aggregate stability.The yellow‒brown soil from the Three Gorges Reservoir area(TGRA)was used,and 8 wetting-drying conditions(0,1,2,3,4,5,10 and 15 cycles)were simulated under 4 acidic conditions(pH=3,4,5 and 7).The particle size distribution and soil aggregate stability were determined by wet sieving method,the contribution of environmental factors(acid condition,wetting-drying cycle and their combined action)to the soil aggregate stability was clarified and the key soil physicochemical factors that affect the soil aggregate stability under wetting-drying cycles and acidic conditions were determined by using the Pearson’s correlation analysis,Partial least squares path modeling(PLS‒PM)and multiple linear regression analysis.The results indicate that wetting-drying cycles and acidic conditions have significant effects on the stability of soil aggregates,the soil aggregate stability gradually decreases with increasing number of wetting-drying cycles and it obviously decreases with the increase of acidity.Moreover,the combination of wetting-drying cycles and acidic conditions aggravate the reduction in the soil aggregate stability.The wetting-drying cycles,acidic conditions and their combined effect imposes significant impact on the soil aggregate stability,and the wetting-drying cycles exert the greatest influence.The soil aggregate stability is significantly correlated with the pH,Ca^(2+),Mg^(2+),maximum disintegration index(MDI)and soil bulk density(SBD).The PLS‒PM and multiple linear regression analysis further reveal that the soil aggregate stability is primarily influenced by SBD,Ca^(2+),and MDI.These results offer a scientific basis for understanding the soil aggregate breakdown mechanism and are helpful for clarifying the coupled effect of wetting-drying cycles and acid rain on terrestrial ecosystems in the TGRA.

Phosphonate-Decorated Covalent Organic Frameworks for Actinide Extraction: A Breakthrough Under Highly Acidic Conditions

Although solid-phase extraction is a useful approach for metal ion separation from aqueous solutions,existing sorbents suffer from low extraction effici-encies and/or instability when in contact with strong acidic media.We report here the first study on rational design and fabrication of phosphonate-decorated covalent organic frameworks,COF-IHEP1 and COF-IHEP2,for efficient and selective extraction of of uranium(VI)[U(VI)]and plutonium(IV)[Pu(IV)]from highly acidic solutions.

Corrosion damage behaviors of rubber O-rings under simulated acid fracturing conditions

To explore the damage behavior of O-ring in acid environment,a high-temperature and high-pressure(HTHP)autoclave was used to simulate the service environment of O-ring,and then 168h corrosion test of hydrogenated nitrile butadiene rubber(HNBR)and fluororubber(FM)O-rings were carried out.The corrosion damage behaviors of two kinds of rubber O-rings in the acidizing fluid were studied through determining their tensile strength,elongation at break,hardness,permanent compressive deformation,tensile fracture morphology and sealing property.The results showed that the crosssectional area and the compression permanent deformation increased,the tensile strength and hardness decreased when the HNBR and FM O-rings under the free state were subjected to acid corrosion.The elongation at break of HNBR decreased,and that of FM rubber increased greatly.Similar with free state,the HNBR and FM O-rings under sealed state also presented the same variation trend.The decrease in the reliability of the O-rings under the sealed state was less significant than that in the free state.In the test,tensile fractures were mostly brittle fractures,HNBR and FM O-rings had obvious corrosion damages such as deformation and swelling.The results could provide a technical basis for the selection of sealing materials,tool optimization design,and construction work in oil and gas fields.

Review:Do Horses Receive Optimum Amounts of Glutamine in Their Diets?

In some species of growing mammals glutamine is an essential amino acid that,if inadequate in the diet,is needed for normal growth and development.It is thus sometimes considered to be a conditionally essential amino acid in some species.A review of studies that have measured L-glutamine concentrations([glutamine])in horses demonstrates that plasma[glutamine]has routinely been reported to be much lower(~330μmol/L)than in other mammals(>600μmol/L).Plasma[glutamine]represents the balance between intestinal transport into the blood after hepatic first pass,tissue synthesis and cellular extraction.The hypothesis is proposed that sustained low plasma[glutamine]represents a chronic state of sub-optimal glutamine intake and glutamine synthesis that does not meet the requirements for optimum health.While this may be without serious consequence in feral and sedentary horses,there is evidence that provision of supplemental dietary glutamine ameliorates a number of health consequences,particularly in horses with elevated metabolic demands.The present review provides evidence that glutamine is very important(and perhaps essential)for intestinal epithelial cells in mammals including horses,that horses with low plasma[glutamine]represents a sub-optimal state of well-being,and that horses supplemented with glutamine exhibit physiological and health benefits.

Biomass,nutrient uptake and fatty acid composition of Chlamydomonas sp.ICE-L in response to different nitrogen sources

Nitrogen removal from media by microalgae provides the potential benefit of producing lipids for biodiesel and biomass. However, research is limited on algal growth and biomass under different nitrogen sources and provides little insight in terms of biofuel production. We studied the influences of nitrogen sources on cell growth and lipid accumulation of Chlamydomonas sp. ICE-L, one of a promising oil rich micro algal species. Chlamydomonas sp.ICE-L grown in NH_4 Cl medium had maximum growth rate. While the highest dry biomass of 0.28 g/L was obtained in media containing NH_4NO_3, the highest lipid content of 0.21 g/g was achieved under nitrogendeficiency condition with a dry biomass of 0.24 g/L. In terms of total polyunsaturated fatty acids（PUFAs）production, NH_4NO_3 and NH_4 Cl media performed better than nitrogen-deficiency and KNO_3 media.Furthermore, NH_4NO_3 and NH_4 Cl media elucidated better results on C18：3 and C20：5 productions while KNO_3and-N conditions were better in C16：0, C18：1 and C18：2, comparatively.

Improvement of sludge dewaterability with modified cinder via affecting EPS

The relationship between the improvement of sludge dewaterability and variation of organic matters has been studied in the process of sludge pre-conditioning with modified cinder, especially for extracellular polymeric substances （EPS） in the sludge. During the conditioning process, the decreases of total organic carbon （TOC） and soluble chemical oxygen demand （SCOD） were obviously in the supernatant especially for the acid modified cinder （ACMC）, which could be attributed to the processes of adsorption and sweeping. The reduction of polysaccharide and protein in supernatant indicated that ACMC might adsorb EPS so that the tightly bound EPS （TB-EPS） decreased in sludge. In the case of ACMC addition with 24 g·L^-1, SRF of the sludge decreased from 7.85 × 10^12 m·kg^-1 to 2.06× 10^12 m·kg^-1, and the filter cake moisture decreased from 85% to 60%. The reconstruction of ＂floc mass＂ was confirmed as the main sludge conditioning mechanism. ACMC promoted the dewatering performance through the charge neutralization and adsorption bridging with the negative EPS, and provided firm and dense structure for sludge floc as skeleton builder. The passages for water quick transmitting were built to avoid collapsing during the high-pressure process.