砖红壤上花生作物铅临界含量的研究

利用盆栽试验，研究在砖红壤上添加不同浓度的铅对花生作物的生长和残留的影响，从农产品卫生质量和作物效应两方面出发，提出花生作物的铅参考临界含量．     

Numerical study of wave–current–vegetation interaction in coastal waters

Research on interactions among wave, current, and vegetation has received increasing attention. An explicit depth-averaged hydrodynamic model coupled with a wave spectral model (CMS-wave) was proposed in this study in order to simulate the wave and wave-induced current in coastal waters. The hydrodynamic model was based on the finite volume method while the intercell flux was computed by employing the Harten–Lax–van Leer approximate Riemann solver to investigate the dry-to-wet interface, and the drag force of vegetation was modeled as the sink terms in the momentum equations. The CMS-wave model was used to investigate the non-breaking and the breaking random waves propagation in vegetation fields. Afterwards, an empirical wave energy dissipation term with plant effect was derived to represent the resistance induced by aquatic vegetation in the wave-action balance equation. The established model was calibrated and validated with both the experimental and field data. The results showed that the wave height decreased significantly along the wave propagation direction in the presence of vegetations. The sensitivity analysis for the plant density, the wave height, and the water depth were performed by comparing the numerical results for the wave height attenuation. In addition, wave and wave-induced current through a finite patch of vegetation in the surf zone were investigated as well. The strong radiation stress gradient could be produced due to the variation of the energy dissipation by vegetation effect in the nearshore zone, which impacted the direction and amplitude of the longshore current. The calculated results showed that the coupling model had good performance in predicting wave propagation and the current over vegetated water regions.     

Research on transesterification parameters for producing plant sterols with supercritical methanol

The supercritical fluid method, regarded as a type of individual production process in the course of preparing plant sterols, has become a promising technology, which possesses advantages of high conversion rate without any pretreatment and need of a catalyst. This study examined the reaction process of the deodorizer distillate (DOD), which mainly included the direct transesterification of DOD to convert into free sterols. The effects of the ratio of methanol to DOD, reaction temperature and time on transesterification were studied. Furthermore, the interactions between different factors were also assessed using the response surface methodology. The optimal conditions obtained were as follows: reaction temperature 553 K, reaction time 80 min, and CH₃OH: DOD = 25:1 (mass ratio). Under these conditions, 36.42% sterol concentration was obtained, which is significantly higher in comparison with the initial sterols’ concentration in raw material (22.45%).     

Effects of two different intercropping systems on arbuscular mycorrhizal fungal colonization and polychlorinated biphenyl (PCB) dissipation北大核心CSCD

Polychlorinated biphenyls (PCBs) are typical organic contaminants in the environment. It is indicated that plants and soil microorganisms have a positive synergistic effect on the remediation of PCB-contaminated soil. To investigate the effect of intercropping on arbuscular mycorrhizal (AM) fungal colonization and PCB remediation, a pot-cultivation experiment with two intercropping treatments, corn (Zea mays L.) / ryegrass (Lolium perenne L.) and corn/alfalfa (Medicago sativa L.), and a corn monoculture was conducted in a greenhouse. All treatments were inoculated with Funneliformis mosseae M47V. Plant biomass, root mycorrhizal colonization rate, concentration of PCBs and their homologs in soil, 16S rDNA gene abundance, and community composition measured by Terminal Restriction Fragment Length Polymorphism (T-RFLP) were determined after harvesting the plants. Intercropping significantly increased the root mycorrhizal colonization rate and plant biomass of corn (P < 0.05), as well as the available N content of the soil. A significant difference of the bacterial community composition was found among different treatments (P < 0.05). Compared with corn monoculture, corn/alfalfa intercropping significantly increased soil bacteria abundance (P < 0.05). The dissipation rates of total PCBs, as well as that of penta-chloro biphenyls were significantly increased in the intercropping treatments, when compared to the corn monoculture treatment. Moreover, corn/ryegrass intercropping has a significantly positive effect on the dissipation of tri-chloro biphenyls. Non-metric multidimensional scaling (NMDS) analysis indicated that the PCBs homologues composition were significantly correlated with the relative abundance of 128 bp and 148 bp T-RFs. Corn intercropping with ryegrass or alfalfa has a positive effect on root mycorrhizal colonization rate and plant biomass of corn. Inoculation of AM fungi in intercropping treatments significantly improved the efficiency of PCB remediation by promoting bacterial abundance and shifting the bacterial community composition. In conclusion, intercropping combined with AM fungi have positive synergistic effects on the remediation of PCB-contaminated soils. © 2018 Science Press. All rights reserved.     

Community structure and biotic integrity of aquatic plants along the North Canal in Beijing北大核心CSCD

Aquatic plants along the North Canal in Beijing were studied to identify the community structure of aquatic plants and vegetation index of biotic integrity (VIBI), and to provide scientific basis for the management and protection of urban rivers. Aquatic plants from 49 sampling sites along the North Canal were investigated during June 2015. Based on the field data, distributing range analysis, discriminatory power analysis, and correlation analysis were used stepwise to select core metrics from candidate metrics to establish the VIBI assessment system. The VIBI value of each sampling site was calculated as the average of the scaled values of all core metrics. Thirty-six aquatic plant species, including 14 hygrophytes, 13 emergent species, 6 submergent species, 2 floating-leaved species, and 1 floating species were collected. Species diversity was low in the North Canal, and no aquatic plants were recorded in 28 sampling sites, of which 9 sampling sites were dried up. Five sites were in excellent condition (VIBI > 0.60), 5 were good (0.60 > VIBI > 0.38), 7 were fair (0.38 > VIBI > 0.23), and 4 were poor (VIBI < 0.23). Based on the distribution of VIBI, Shahe River and Wenyu River upstream, and Fenghe River located in suburbs had a higher VIBI. Downstream tributaries, such as Qinghe River, Bahe River, and Liangshui River, had a lower VIBI. Correlation analysis showed that habitat quality, habitat complexity, and vegetation diversity along riparian zones were the important factors affecting VIBI along the North Canal, Beijing. Aquatic plants along the North Canal showed low species diversity owing to human disturbance. VIBI along tributaries with limited disturbance from human activities was higher; however, VIBI along tributaries disturbed by frequent human activities was lower. © 2018 Science Press. All rights reserved.     

Tolerance of the black soldier fly,Hermetia illucens (Diptera: Stratiomyidae) to pH value,pungency, and NaCl in foodstuffs北大核心CSCD

The black soldier fly (BSF), Hermetia illucens, has been considered impressive as a saprophagous insect, for its high ability to convert organic waste to insect protein and oil. Hence, it has been regarded by the municipal administration that BSF might be used as a medium to deal with food waste. However, food waste in China has been characterized as having a high salt content, oily, and very spicy, which usually renders them unsuitable for animal feeding. In order to assess the technological reliability for BSF conversion of food waste, the tolerance of BSF for pH values, pungency, and NaCl in food were investigated in this case. Results indicated that strong acidity (pH = 3) was not good for the development of BSF, demonstrating less body weight and eclosion failure. In contrast, strong basicity (pH = 11) seemed to be beneficial for larval development with high biomass, and there is no difference in pupation, eclosion, larval biomass, and livability for BSF for pH values between 5 and 11. With regards to salinity, liner correlations were observed; the salinity strength increased along with the extension of the larval phase, but body weight, pupation rate, emerging rate, and livability were still consistent under 6% density of salinity. Influence of pungency on BSF larvae has not yet been found. In conclusion, BSF showed a high tolerance to pH value, pungency, and salinity in foodstuffs. Hence, it is expected that food waste from common environments might have a lesser possibility to cause negative effects on BSF development, which could be good news for BSF conversion technology. As for the process design, the conclusion suggested that food waste optimum for BSF is expected to be alkaline and low-salt, which would be helpful to improve the efficiency and harvest. © 2018 Science Press. All rights reserved.     

75％戊唑·嘧菌酯可溶性粉剂对3种昆虫的急性毒性与初级风险评估

为明确75％戊唑·嘧菌酯可溶性粉剂对意大利蜜蜂、玉米螟赤眼蜂和家蚕的急性毒性和初级风险.采用国标《化学农药环境安全评价试验准则》(GB/T 31270—2014)中的4种方法,包括饲喂法(蜜蜂经口)、点滴法(蜜蜂接触)、药膜法(赤眼蜂)和浸叶法(家蚕),分别测定了该农药对上述3种非靶标昆虫的急性毒性,并根据国标《农药登记环境风险评估指南》(NY/T 2882—2016)把这些结果用于该药的初级风险评估.结果表明,75％戊唑·嘧菌酯可溶性粉剂对意大利蜜蜂的急性接触毒性48 h半致死剂量(48 h-LD50)为>105μg·蜂-1,急性经口毒性48 h-LD50为65.9μg·蜂-1,对蜜蜂的风险可接受(风险商(RQ)=0.135≤1).对玉米螟赤眼蜂的急性毒性24 h半致死用量(24 h-LR50)为2.81×10-6 mg·cm-2,对玉米螟赤眼蜂的农田内和农田外喷雾场景风险均不可接受(危害商HQin=1199>5,HQoff=24.2>5).对家蚕的急性毒性96 h半致死浓度(96 h-LC50)为596 mg·L-1,对家蚕的喷雾场景下的最外围桑树风险不可接受(RQ=7.47>1),次外围桑树风险可接受(RQ=0.457≤1).对不可接受的风险,宜采取风险减轻措施,如喷雾施药期间禁止释放赤眼蜂,避免在桑园周围喷雾法施药等,以达到保护非靶标环境生物的目的.