The effectiveness of travel restriction measures in alleviating the COVID-19 epidemic: evidence from Shenzhen,China

Environmental Geochemistry and Health - With the expansion of the global novel coronavirus disease (COVID-19) pandemic, unprecedented interventions have been widely implemented in many countries,...     

Rainfall-human-spatial interactions in a salinity-prone agricultural region of the Western Australian wheat-belt

To explore the complexity of temporal and spatial dynamics of an agricultural landscape under various external and internal driven scenarios, SimKat, an agent-based model, has been developed with the simulation computer program CORMAS. This model combines simplified bio-physical processes of land cover, regional dry-land salinity changes, rainfall impact on productivity, farm profitability and the complexity of land-use decisions of individual farmers in a dry-land agricultural catchment (no irrigation). In this model, simulated farmers formulate individual decisions dealing with land-use changes based on the combined performance of their past land cover productivity and market returns. The willingness to adapt to market drivers and the ability to maximize returns vary between farmers. In addition, farmers in the model can demonstrate various attitudes towards dry-land salinity mitigation as a consequence of experiencing and perceiving salinity on their farm, in the neighborhood or across the entire region. Consequently, farmers can adopt land cover strategies aimed at reducing dry-land salinity. Aggregating the simulated individual behavior of farmers combined with historical rainfall and market price records, reproduced similar aggregated trends of land-cover changes, regional salinity change and farm number decline as observed in the last 20 years in the subject region (Katanning, Western Australia). Using the model in an initial exploratory study on the impact of rainfall variability and change highlighted the importance of average rainfall decline and the widespread willingness of farmers to adapt perennial vegetation in their farming systems to combat regional dry-land salinity. Rainfall decline, as one of the observed consequences of climate change in this region, can also lead to prolonged sequences of dry seasons in the future. Adaptation by farmers to sequences of dry and wet seasons, rather than an average trend in rainfall, seems to be critical for farm survival in this region. Intensifying cropping during wet seasons to maximize farm returns can increase vulnerability in subsequent periods of dry seasons, in particular where alternative income from pasture and sheep production has been lost in the adaptation process.     

农药在稻田使用对地下水的风险评估研究进展

农药风险评估可为农药登记和农药的环境安全管理提供重要的科学依据。水稻生产过程中病虫草害严重,农药使用品种多、频次高,田水存留时间长,对地下水污染风险高。开展农药在稻田使用对地下水的风险评估研究具有重要的现实意义。文章详细介绍了欧盟和美国的水稻-地下水风险评估研究进展,包括风险评估程序、暴露评估模型及暴露场景等。总结了我国农药在稻田使用对地下水风险评估的研究现状,并分析了我国研究的不足之处。在此基础上,提出了加强我国农药在稻田使用对地下水风险评估的建议。     

蚕豆根尖微核技术的方法学新论

虽然蚕豆根尖微核技术已是一个成熟规范的检测污染物遗传毒性的方法,但其中仍涉及一些重要的方法学问题值得深入探讨和研究。本文在图示正确观测蚕豆根尖细胞内微核和染色体畸变,如染色体断裂、丢失及染色体桥等的基础上,提出应该对蚕豆根尖分裂相细胞及其染色体畸变进行观测,以便更加准确、细致地反映污染物作用的剂量-效应关系和分子机制。同时还就该方法的其他重要问题提出了自己的观点,供同行们深入探讨和研究,使之不断完善,更好地服务于环境监测和风险评价等领域。     

2,2’,4,4’-四溴联苯醚对大型溞的毒性效应

以实验室培养的大型溞为受试生物,进行了2,2’,4,4’-四溴联苯醚(BDE-47)对大型溞的48h急性毒性实验和21d慢性毒性实验,并研究了暴露在不同质量浓度和处理时间的BDE-47中,大型溞的抗氧化酶系中的超氧化物歧化酶(SOD)和谷胱甘肽硫转移酶(GST)的酶活性变化。结果表明,BDE-47对大型溞的48h的半致死浓度为1.04mg·L-1,属于高毒物质;在BDE-47慢性毒性实验低浓度处理组中,大型溞的体长及繁殖能力受到了抑制,而高浓度处理组中大型溞的体长及繁殖能力上升,其中第一次产仔数和产卵总数是表征BDE-47慢性毒性的最灵敏参数。随着BDE-47浓度的增加,大型溞SOD和GST活性均呈现出低浓度诱导高浓度抑制的现象。SOD和GST均表现出一定的敏感性,但相对SOD,GST对BDE-47暴露更为敏感。     

调水过程中城市内河含氮污染物负荷变化规律研究

针对我国城市内河污染日益严重的问题,以巢湖市老城区环城河为研究对象,拟定调水方案,进行调水试验。依据沿河水文水质情况,布设6个实时水质监测点,并将环城河概化为5个河段。应用测得的水文水质数据对各河段不同时间点的含氮污染物负荷进行估算,初步研究了各河段NH3-N、TN负荷量的变化规律。通过对比上下游各河段含氮污染物负荷去除效果,分析调水效果的影响因素,总结个别河段调水效果不佳的原因,提出4条优化意见。并结合实际情况,选取其中可行性较强的1条对其有效性进行实验验证。     

Effects of paclobutrazol (PP333) on lead and zinc accumulations in Pseudostellaria maximowicziana

Paclobutrazol (PP333) can enhance the resistance capabilities of plants to stress conditions. In this study, PP333 were sprayed on the lead (Pb) and zinc (Zn) accumulator plant Pseudostellaria maximowicziana, which was planted in Pb–Zn contaminated soil, and the effects of PP333 on Pb and Zn accumulation levels in P. maximowicziana were studied. Spraying 10?mg/L PP333 increased, while 20, 30 and 50?mg/L PP333 decreased, the biomass of P. maximowicziana compared with the control. The 10?mg/L PP333 had no significant effects on the photosynthetic pigment contents of P. maximowicziana compared with the control, while the other doses increased the contents. The activities of antioxidant enzymes (superoxide dismutase, peroxidase and catalase) and the Pb and Zn concentrations in P. maximowicziana were increased by PP333 compared with the control. These items had the increase trend with the increase of PP333 concentrations. Only 10 and 20?mg/L PP333 increased the amount of Pb extracted by P. maximowicziana shoots, while all of the doses increased the amount of Zn extracted by P. maximowicziana shoots. Thus, low concentration of PP333 could promote the growth and heavy metal extraction ability of P. maximowicziana shoots, with the 10?mg/L being the best.     

Ecological stoichiometric characteristics of carbon,nitrogen, and phosphorus in three forests in the Lüliang Mountainous Area of Shanxi Province北大核心CSCD

Using a standard plot method, the stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) in leaves, litter, and soil (0-20 cm depth) was investigated for three forest types: Populus davidiana, Larix principis-rupprechtii, and Pinus tabuliformis. The results showed that the stoichiometry of C, N, and P of the same component in the three forests were significantly different. The C and N contents in leaves, litter, and soil in P. davidiana forest were higher than those in L. principis-rupprechtii and P. tabuliformis forests were. However, P in the L. principis-rupprechtii forest was higher than that in the P. davidiana forest and P. tabuliformis forests were. The C, N, and P contents of the components in the three forests were, in order, leaves > litter > soil, and the three nutrient contents were significantly higher in leaves and litter than they were in soil. C:N and C:P in the three forests exhibited a trend of litter > leaves > soil, whereas that for N:P was leaves > soil > litter. There were highly significant positive relationships in N:P between the litter and the soil in the P. davidiana forest. Leaf C:N and litter C:P in the L. principis-rupprechtii forest were significantly negatively correlated, whereas N:P in the leaves and soil was positively correlated. There was a significant positive correlation in N:P between the leaves and the soil in the P. tabuliformis forest. In conclusion, the N contents in leaves and soil exhibited a significant positive correlation, whereas there was no significant correlation between C, N, and P in litter or soil. Environmental factors had a large influence on the stoichiometry of C, N, and P in soil. In particular, latitude and altitude had the most significant effects on C, N, P, C:N, and C:P and were significantly p ositively correlated. T hese results provide a scientific basis for f urther studies on nutrient utilization a nd t he cyclic characteristics of different forests in this area. © 2018 Science Press. All rights reserved.     

Bacterial community structure of Tricholoma matsutake stipe soil by high-throughput sequencing北大核心CSCD

In order to understand the interaction between microorganisms in soil attached to the stipes of Tricholoma matsutake, we utilized high-throughput sequencing technology using an Illumina HiSeq 2500 System (San Diego, CA, USA) to explore the bacterial community structure in such soils and analyzed the effects of microorganisms on the formation and growth of T. matsutake. A total of 6 730 sequences were obtained from the samples, and these sequences were clustered into 928 operational taxonomic units (OTUs) at a 97% similarity level. In addition, these OTUs were grouped into 22 bacterial phyla (including 62 classes, 90 orders, 162 families, and 275 genera) and 2 archaeal phyla (including 4 classes, 6 orders, 7 families, and 8 genera). Proteobacteria was the dominant phylum present in all the samples, and these bacteria were significantly more abundant in soils attached to stipe of T. matsutake than they were in the control samples. Similarly, Beta-proteobacteria were the dominant class, and bacteria in this class were less abundant than they were in the control samples. Moreover, the genus Burkholderia within the Proteobacteria was more abundant in the control samples than in the T. matsutake soil samples. Generally, Proteobacteria, especially the genus Burkholderia, played an important role in the growth of T. matsutake, whereas other bacteria, such as Unknown-Ellin 60, would probably inhibit the growth of T. matsutake. This study showed that bacteria might be involved in the growth of T. matsutake and the formation of its fruiting bodies, but they had no positive relationship with bacterial abundance, which may provide theoretical guidance for the cultivation of T. matsutake. © 2018 Science Press. All rights reserved.