[Distribution and Environmental Significance of Rare Earth Elements in Typical Protected Vegetable Soil, Northern China]

The concentrations of rare earth elements (REEs) in protected vegetable soils in Wuqing district of Tianjin City, Jinzhong district of Shanxi Province, Shenyang district of Liaoning Province, and Wulanchabu district of Inner Mongolia Autonomous Region in northern China were measured to analyze the change characteristics of soil REEs in the process of protected vegetable cultivation. Additionally, we sought to use the REEs parameters to trace the feasibility of characterizing the interference of human activities on the soil ecological environment. The results showed that the total content of REEs (REE) in the topsoil of protected vegetable fields ranged from 146.52 to 158.76 mg·kg^-1, with an average of 152.34 mg·kg^-1 in Shenyang; 92.16 to 137.69 mg·kg^-1, with an average of 115.03 mg·kg^-1in Wuqing; 91.38 to 118.84 mg·kg^-1, with an average of 108.03 mg·kg^-1 in Wulanchabu; and 97.62 to 111.27 mg·kg^-1, with an average of 102.43 mg·kg^-1in Jinzhong. The REEs distribution patterns in the soils of the four areas, standardized with chondrite, characterized by a right tilt, showed that light rare earth elements were obviously enriched in the soil, demonstrated by the ratios of LREE/HREE and (La/Yb) _N, which were greater than 6 and 7, respectively. The values of (La/Sm)_N in the soils were higher than 3, suggesting that there was an obvious fractionation between light rare earth elements, whereas the values of (Gd/Yb)_N were between 1-2, and there was a weak fractionation between heavy rare earth elements. The values of δEu in the soils were between 0.56 and 0.61, showing that Eu had a negative abnormality. The values of δCe were between 0.89 and 1.11, showing that Ce had no abnormality or weak positive abnormality. The higher LREE/HREE and (La/Yb)_N in protected vegetable soil than that in open-air vegetable soil indicated the increasing differentiation degree between light and heavy rare earth elements in protected vegetable soil. The lower (La/Sm)_N in protected vegetable soils indicated the reduction in the differentiation among light rare earth elements in soil. Higher δCe values and lower δEu values suggested that Ce and Eu were relatively enriched and depleted, respectively, during vegetable planting. The REE, LREE, (La/Sm)_N, and δEu in protective soil decreased with the number of cultivation years, whereas the (Gd/Yb)_N and δCe increased, but the HREE values did not change significantly. There was a significant correlation between δCe, δEu, (La/Yb)_N, (Gd/Yb_)N, and soil bulk density, soil moisture content, and soil organic matter in Tianjin protected vegetable soils, showing preliminarily that rare earth elements can be used as tracer elements to characterize the interference intensity of human activities on soil.

[Space-time Characteristics and Environmental Significance of Stable Isotopes in Precipitation at an Arid Inland River Basin]

This study was based on one complete hydrological year sampling of precipitation and meteorological data of the Shiyang River Basin in the Wuwei Station (1531 m a.s.l.), Minqin Station (1389 m a.s.l.), and Xidahe Station(2897 m a.s.l.) from July 2013 to July 2014. This paper aims to analyze temporal and spatial variation of stable isotopes in local precipitation, and discuss the impact of environmental factors during precipitation. The stable isotope evolution correlation with temperature, humidity, precipitation, vapor pressure, and average relative humidity is analyzed. The results show that:①During the study period, the stable isotope of precipitation showed significant seasonal changes, lower in the winter and spring, higher in the summer and autumn;②The monthly average D-excess of Wuwei Station is lower than that of Xidahe Station. In addition to the possibility of different water vapor sources, the high-altitude mountain areas are more affected by local recirculating water vapor, and the secondary evaporation under the clouds in low-altitude plain areas is stronger;③The stable isotope of precipitation in the basin shows a significant temperature effect, and the precipitation effect is reflected on the weather scale, which may be affected by leaching or monsoon circulation;④The δ¹⁸O value of precipitation is negatively correlated with the average relative humidity. It may be that the secondary evaporation under the cloud is weakened by the increase of precipitation and humidity.

UV radiation-induced enterobacterial responses, other processes that influence UV tolerance and likely environmental significance

The ability of enterobacteria to become UV-tolerant is important because such tolerance may enable organisms to resist irradiation in the environment, in water treatment, in shell-fish, in stages of food processing, and at locations in the domestic, commercial and hospital environment The mechanism for regulation of tolerance induction and SOS response induction has been studied for many years, and is well understood, except for the early stages of induction. Such early stages, namely sensing of the stimulus (UV irradiation) and the way in which such sensing leads to signal production, have until now been poorly understood. The claim has been made that DNA is the sensor and that either damage to DNA or production of SS regions in DNA (following interaction of UV with DNA) triggers the signal that sets in train RecA activation and other stages of tolerance induction. This claimed induction mechanism is a "classical" one in the sense that it involves intracellular sensing (by DNA) of the stressing stimulus (UV), and production of an intracellular signalling molecule. It is not, however, firmly established as the mechanism for initiation of UV tolerance induction and SOS response induction. The results reviewed here give firm evidence for a different and unique mechanism for sensing of UV and production of the signal. These results establish without doubt that, for UV tolerance induction, the UV sensor is an extracellular protein, which is a UV tolerance-specific extracellular sensing component (ESC). This component is formed by unstressed cells and on interacting with the stimulus (UV) in the medium, is converted to the tolerance induction signalling molecule, which is a UV tolerance-specific extracellular induction component (EIC). It is this extracellular signal which interacts with the sensitive organisms and triggers tolerance induction. This pair of extracellular components (ECs) may offer the only means of switching-on such tolerance induction; certainly they offer the only known way for early warning to be given of impending UV challenge. Thus, the EIC can diffuse from a region of UV stress to a stress-free region and there warn organisms of impending stress and prepare them to resist it. As indicated here, UV irradiation not only induces UV tolerance, but also switches-on acid tolerance, alkali tolerance and thermotolerance responses. The fact that all three responses involve ESC/EIC pairs strongly supports the view that functioning of such EC pairs form the major, if not the only, means for UV tolerance induction. The UV tolerance-specific ESC can detect other stresses and becomes activated, leading to cross-tolerance responses. Of particular interest, this ESC acts as a biological thermometer, detecting increases in temperature, such increases leading to gradually increasing formation of the EIC and, accordingly, gradual increases in UV tolerance. This UV tolerance-specific ESC can also detect other stresses e.g. acting as a pH sensor. In all cases, on activation, the EIC formed (from this specific ESC) only induces UV tolerance. It is proposed that the interaction of EICs with stress-sensitive organisms should be examined, and it is suggested that such EICs may, directly or indirectly, interact with and activate the same stress response regulators as are used to detect internal stressors and which, on activation, also trigger the switching-on of stress responses. For example, EICs either a in a protonated or oxidised state (formed by activation of ESCs by H+ or H2O2) or b produced by irradiation, may lead to protonation or oxidation or other forms of activation of the appropriate regulator (e.g. Fur or OxyR or RecA etc), leading to response induction.