河西走廊绿洲边缘降水对土壤水分特征的影响

【目的】探究干旱地区间断性和不可预知特征的降水对土壤水分特征的影响,为荒漠绿洲过渡区的生态建设和恢复提供理论依据。【方法】通过对河西走廊绿洲边缘的沙质荒漠和砾质荒漠土壤水分的长期观测,结合当地气象数据,分析降水对土壤水分特征的影响。【结果】研究区域沙质和砾质荒漠的土壤水分处于中等变异程度,沙质荒漠土壤含水量的最大值为6.61%、砾质荒漠土壤含水量的最大值为11.81%,与降水量的最大值均出现在7月,土壤水分同降水量存在正相关关系。荒漠绿洲区土壤水分在垂直空间上随着土层深度的增加,土壤水分变异系数减小,土壤水分变化由活跃逐渐趋于稳定。但降水沙质荒漠和砾质荒漠区土壤水分的影响存在显著差异,沙质荒漠土壤以自上而下的活塞式下渗为主,降水以逐层向下的方式入渗,下层土壤接受降水补给时具有滞后性。而砾质土壤各层对降水的反应迅速,能够通过大孔隙快速补给下层土壤,水分迅速入渗至深层土壤中。【结论】河西走廊绿洲边缘的土壤水分受土壤类型的影响,降水对其影响有差异,根据不同的土壤水分变化特征,科学开展生态建设和恢复,对绿洲边缘生态系统的可持续发展有重要意义。

中国纺织服装行业绿色标准比较分析

为系统解析中国纺织服装行业的绿色标准,对现行的相关绿色标准进行了统计归类、绿色评价指标梳理和绿色指标限值比对,结果表明:现行的纺织服装行业绿色标准包括3种限制类标准(取水定额、水污染物排放限额、能耗限额)和5种鼓励类标准(节水型企业评价、绿色工厂评价、绿色生态类产品评价、绿色园区评价和绿色供应链评价);前四类标准的评价指标只针对某一方面绿色性能设定要求,后四类标准则为取水量、能耗、污染物排放等多维度指标综合评价;在单位产品取水量限额、单位产品废水排放量限额方面,取水定额标准和水污染物排放限额标准要求最低;在单位产品能耗限额方面,能耗限额标准、绿色工厂评价标准、绿色生态类产品评价标准对于同类产品的限额值差距较小。

兰州市常见园林阔叶树种滞尘能力测定

粉尘污染空气,影响城市居民生产生活。本文以26种兰州市园林常见阔叶树为对象,采用差重法测定叶片滞尘能力。结果表明,不同树种叶片滞尘能力差异巨大,紫叶李、紫薇、榆叶梅、毛泡桐滞尘能力优良,叶滞尘系数>0.9 g/m^2;贴梗海棠、绦柳、华北珍珠梅、金叶女贞滞尘能力低下,叶滞尘系数<0.3 g/m^2;紫叶李叶片滞尘能力高达金叶女贞的6.7倍。

Sedum alfredii H:A new Zn hyperaccumulating plant first found in China

Field survey and greenhouse experiments were carried out to identify and characterize zinc (Zn) uptake and accumulation by a new Zn hyperaccumulating plant species (Sedum alfredii Hance) native to China. Zinc concentration in the shoots of Sedum alfredii Hance grown on an ancient mined area ranged from 4134 to 5000 mg/kg, with a mean of 4515 mg/kg. It suggests that Sedum alfredii could not only grow on heavily Pb/Zn contaminated soils, but also could accumulate extraordinarily high concentration of Zn. Under nutrient solution culture conditions, Sedum alfredii Hance grew healthy at Zn supplying levels from 0.006 to 240 mg · L-1. Zinc concentration in the shoots increased with external Zn levels increasing. The Zn concentration and accumulation in the shoots reached the highest at Zn supply level of SO mg/L, with 19.67 g/kg and 19.83 nig/plant, respectively. All the results showed that Sedum alfredii Hance is a new Zn hyperaccumulating plant. This provides a new plant material to explore mechanism of

Molecular dynamics simulation of the test of single-walled carbon nanotubes under tensile loading

Molecular dynamics (MD) simulations were performed to do the test of sin-gle-walled carbon nanotubes (SWCNT) under tensile loading with the use of Bren-ner potential to describe the interactions of atoms in SWCNTs. The Young’s modulus and tensile strength for SWCNTs were calculated and the values found are 4.2 TPa and 1.40―1.77 TPa, respectively. During the simulation, it was found that if the SWCNTs are unloaded prior to the maximum stress, the stress-strain curve for unloading process overlaps with the loading one, showing that the SWCNT’s de-formation up to its fracture point is completely elastic. The MD simulation also demonstrates the fracture process for several types of SWCNT and the breaking mechanisms for SWCNTs were analyzed based on the energy and structure be-havior.