1.
Study on shear behavior of kaolinite contaminated by heavy metal Cu (II).
Zhang, Z, Chen, Y, Fang, J, Guo, F
Environmental science and pollution research international. 2019;(14):13906-13913
Abstract
Numerous studies have shown that the invasion of the chemicals plays an important role on the geomechanical properties of the soil. This article aims to investigate the shear behavior of contaminated soil by laboratory tests and develop an extended shear strength model on the basis of the experimental results. In order to explicitly evaluate the effect of solution concentration on the shear strength behavior of soil, the remolded samples of kaolinite mixed with different concentrations of CuCl2 solutions were prepared to carry out a series of consolidated-undrained triaxial shear strength tests. The results indicate that different CuCl2 solution concentrations have significant influence on the shear strength property of kaolinite. With the increase of CuCl2 solution concentration, the shear strength of soil displays a declining tendency, and the strength properties including cohesion and internal friction angle are also reduced, which indicates the Cu (II) that existed in the soil samples has deteriorated the soil strength strongly. Based on the experimental results, an extended Mohr-Coulomb strength model for contaminated soils has been proposed by introducing osmotic suction as a macro variable parameter. The conclusions in this study can provide reference for pollution prevention of existing and future foundations.
2.
Precipitation overrides warming in mediating soil nitrogen pools in an alpine grassland ecosystem on the Tibetan Plateau.
Lin, L, Zhu, B, Chen, C, Zhang, Z, Wang, QB, He, JS
Scientific reports. 2016;:31438
Abstract
Soils in the alpine grassland store a large amount of nitrogen (N) due to slow decomposition. However, the decomposition could be affected by climate change, which has profound impacts on soil N cycling. We investigated the changes of soil total N and five labile N stocks in the topsoil, the subsoil and the entire soil profile in response to three years of experimental warming and altered precipitation in a Tibetan alpine grassland. We found that warming significantly increased soil nitrate N stock and decreased microbial biomass N (MBN) stock. Increased precipitation reduced nitrate N, dissolved organic N and amino acid N stocks, but increased MBN stock in the topsoil. No change in soil total N was detected under warming and altered precipitation regimes. Redundancy analysis further revealed that soil moisture (26.3%) overrode soil temperature (10.4%) in explaining the variations of soil N stocks across the treatments. Our results suggest that precipitation exerted stronger influence than warming on soil N pools in this mesic and high-elevation grassland ecosystem. This indicates that the projected rise in future precipitation may lead to a significant loss of dissolved soil N pools by stimulating the biogeochemical processes in this alpine grassland.
3.
[Research advances in iron and zinc transfer from soil to plant in intercropping systems].
Xia, HY, Xue, YF, Meng, WW, Yu, LM, Liu, LY, Zhang, Z
Ying yong sheng tai xue bao = The journal of applied ecology. 2015;(4):1263-70
Abstract
Intercropping facilitates the efficient utilization of land, light, water and nutrients. It is, therefore, important to increase the biodiversity of farmland and to develop sustainable ecological agriculture in both theory and practice. Intercropping helps improve the mobilization and uptake of soil iron (Fe) and zinc (Zn) and corresponding nutritional status in the plants, thus achieving grain micronutrient biofortification. In this review, phenomena of the improvement of Fe and Zn nutrition in dicotyledonous plants as affected by intercropping with gramineous plants (e.g. maize/peanut intercropping) were summarized. Moreover, the possible mechanisms in relation to interspecific rhizosphere molecular and physiological processes, as well as the changes in interspecific root morphology and distribution and microorganisms in the rhizosphere were elucidated. The accumulation, transfer and distribution of Fe and Zn in the plants in intercropping systems were also reviewed. The possible affecting factors on nutrients of Fe and Zn were analyzed. Based on the present advances in the mobilization and acquisition of soil Fe and Zn, and their accumulation and distribution in plants as well as the related management and environment influence factors, some new research questions were pointed out. Quantitative analysis, dynamic and systemic researches and field studies on Fe and Zn transfer from soil to plant in intercropping systems should be strengthened in the future.
4.
Linking stoichiometric homeostasis of microorganisms with soil phosphorus dynamics in wetlands subjected to microcosm warming.
Wang, H, Li, H, Zhang, Z, Muehlbauer, JD, He, Q, Xu, X, Yue, C, Jiang, D
PloS one. 2014;(1):e85575
Abstract
Soil biogeochemical processes and the ecological stability of wetland ecosystems under global warming scenarios have gained increasing attention worldwide. Changes in the capacity of microorganisms to maintain stoichiometric homeostasis, or relatively stable internal concentrations of elements, may serve as an indicator of alterations to soil biogeochemical processes and their associated ecological feedbacks. In this study, an outdoor computerized microcosm was set up to simulate a warmed (+5°C) climate scenario, using novel, minute-scale temperature manipulation technology. The principle of stoichiometric homeostasis was adopted to illustrate phosphorus (P) biogeochemical cycling coupled with carbon (C) dynamics within the soil-microorganism complex. We hypothesized that enhancing the flux of P from soil to water under warming scenarios is tightly coupled with a decrease in homeostatic regulation ability in wetland ecosystems. Results indicate that experimental warming impaired the ability of stoichiometric homeostasis (H) to regulate biogeochemical processes, enhancing the ecological role of wetland soil as an ecological source for both P and C. The potential P flux from soil to water ranged from 0.11 to 34.51 mg m(-2) d(-1) in the control and 0.07 to 61.26 mg m(-2) d(-1) in the warmed treatment. The synergistic function of C-P acquisition is an important mechanism underlying C∶P stoichiometric balance for soil microorganisms under warming. For both treatment groups, strongly significant (p<0.001) relationships fitting a negative allometric power model with a fractional exponent were found between n-HC∶P (the specialized homeostatic regulation ability as a ratio of soil highly labile organic carbon to dissolved reactive phosphorus in porewater) and potential P flux. Although many factors may affect soil P dynamics, the n-HC∶P term fundamentally reflects the stoichiometric balance or interactions between the energy landscape (i.e., C) and flow of resources (e.g., N and P), and can be a useful ecological tool for assessing potential P flux in ecosystems.