基于Mogi-Coulomb强度准则的井壁稳定性力学分析新方法*

传统井壁坍塌失稳分析模型是基于M-C破坏准则而建立的,该方法忽略了中间主应力对岩石强度的影响,常使得预测的钻井液密度过于保守。为此,引入考虑中间主应力的Mg-C破坏准则建立任意井眼的井壁稳定性评价新模型,通过数值模拟法分析了不同地应力状态下的井斜角和方位角对井壁稳定性的影响。研究结果表明: Mg-C准则克服了M-C准则忽略中间主应力低估岩石强度的影响,其计算结果略低于M-C准则的计算结果,有助于提高钻速,降低钻井成本;正断层地应力状态时,沿最小水平主应力方向钻进时,井壁稳定性最好;走滑断层地应力状态时,沿最大与最小水平主应力之间的某一临界角钻进时井壁最稳定;逆断层地应力状态时,沿最大水平主应力方向钻进时井壁最稳定;该模型有助于指导现场钻井井眼轨迹的优化设计及安全施工。     

Siting and Routing Assessment for Solid Waste Management Under Uncertainty Using the Grey Mini-Max Regret Criterion

Solid waste management (SWM) is at the forefront of environmental concerns in the Lower Rio Grande Valley (LRGV), South Texas. The complexity in SWM drives area decision makers to look for innovative and forward-looking solutions to address various waste management options. In decision analysis, it is not uncommon for decision makers to go by an option that may minimize the maximum regret when some determinant factors are vague, ambiguous, or unclear. This article presents an innovative optimization model using the grey mini-max regret (GMMR) integer programming algorithm to outline an optimal regional coordination of solid waste routing and possible landfill/incinerator construction under an uncertain environment. The LRGV is an ideal location to apply the GMMR model for SWM planning because of its constant urban expansion, dwindling landfill space, and insufficient data availability signifying the planning uncertainty combined with vagueness in decision-making. The results give local decision makers hedged sets of options that consider various forms of systematic and event-based uncertainty. By extending the dimension of decision-making, this may lead to identifying a variety of beneficial solutions with efficient waste routing and facility siting for the time frame of 2005 through 2010 in LRGV. The results show the ability of the GMMR model to open insightful scenario planning that can handle situational and data-driven uncertainty in a way that was previously unavailable. Research findings also indicate that the large capital investment of incineration facilities makes such an option less competitive among municipal options for landfills. It is evident that the investment from a municipal standpoint is out of the question, but possible public–private partnerships may alleviate this obstacle.     

电袋复合除尘器气流分布技术及评判标准研究

从电袋复合除尘器的基本原理出发,提出对其进行气流组织的三个关键点,并从理论上对影响电袋复合除尘器性能的烟气冲刷速度、逆重力向速度分量（CANE速度）、静电区除尘效率、静电区气流均匀性系数、净气室及出口烟道的设计等方面进行了研究。     

An evaluation of the toxicity and bioaccumulation of cisplatin in the marine environment using the macroalga, Ulva lactuca

The cytotoxic drug, cisplatin (cis-PtCl₂(NH₃)₂), has been added to cultures of the marine macroalga, Ulva lactuca, under various experimental conditions. Both accumulation and internalisation over a 48 h period was greater when cisplatin was added to coastal sea water (salinity = 33) from a distilled water solution than when added to either sea water or estuarine water (salinity = 16.5) from a saline solution. This effect is attributed to the greater abundance of the more reactive monoaqua complex (cis-PtCl(OH₂)(NH₃)₂⁺) in the distilled water solution and kinetic constraints on its conversion back to cis-PtCl₂(NH₃)₂ in sea water. Despite its mode of action at the cellular level, cisplatin added up to concentrations of 150 nM did not incur a measurable reduction in the efficiency of photochemical energy conversion under any of experimental conditions tested.     

Differential accumulation of mercury and other trace metals in the food web components of a reservoir impacted by a chlor-alkali plant (Flix, Ebro River, Spain): Implications for biomonitoring

Comparative studies of biomonitors of trace metal contamination are relatively scarce. We took advantage of a point source pollution in a reservoir (Flix, Spain) to compare trace metal (Hg, Pb, Cd, Se, As, Zn, Cu, Cr) bioaccumulation patterns among 16 food web components. Our results indicate that most organisms are suitable for Hg biomonitoring, whereas other metals are better monitored by only some of them. Biofilms and zebra mussel were the organisms with larger and more diverse biomonitoring capacity. However, we show that using groups of biomonitors increase the scope and strengths of the conclusions and specific goals can be better addressed. We conclude providing an overview of the strengths and weaknesses of the main organisms considered for biomonitoring trace metals in rivers and reservoirs.     

The effect of nitrate concentration on sulfide-driven autotrophic denitrification in marine sediment

Copepods have been widely used to evaluate toxicity of metals present in marine environments. However, a technical difficulty is to understand the possible routes of metal uptake and to identify in which tissues or organs metals are being accumulated. Traditional techniques are hard to be employed once each organ has to be analyzed separately. Autoradiography is an alternative technique to circumvent this limitation, since metal distribution in tissues can be visualized and quantified, even in small organisms like copepods. In the present study, accumulation and distribution of ⁶⁴Cu in the copepod Calanus hyperboreus was studied using autoradiography. Copepods were exposed for 2 h to copper (2.3 mg L⁻¹; 1.08 MBq ⁶⁴Cu mg⁻¹ Cu) and then allowed to depurate for 2 h in clean seawater. Total ⁶⁴Cu was determined by gamma-spectrometry after a metal exposure and a depuration period. ⁶⁴Cu distribution was determined based on images generated by autoradiography. Metal accumulation was observed on all external surfaces of the copepods, being accumulated mostly on the ventral region, followed by dorsal, urossoma and internal regions. After depuration, radioactivity levels had a decrease in the sum of external body surface. Our results show that copper uptake by C. hyperboreus is fast and that a non-negligible proportion of the accumulated metal can reach internal tissues, which may lead to detrimental physiological effects. Moreover, whole-body autoradiography was demonstrated to be an efficient technique to study copper accumulation and body distribution in a very small organism such as the copepod C. hyperboreus.     

Accumulation of platinum group elements by the marine gastropod Littorina littorea

The accumulation and trophic transfer of the platinum group elements (PGE): Rh, Pd and Pt; have been studied in short-term (5 day) exposures conducted in aquaria containing the marine macroalga, Ulva lactuca, and/or the grazing mollusc, Littorina littorea. Metals added to sea water (to concentrations of 20 μg L⁻¹) were taken up by U. lactuca in the order Rh, Pt > Pd and by L. littorea in the order Pd ≥ Pt ≥ Rh, with greatest metal accumulation in the latter generally occurring in the visceral complex and kidney. When fed contaminated alga, accumulation of Rh and Pd by L. littorea, relative to total available metal, increased by an order of magnitude, while accumulation of Pt was not readily detected. We conclude that the diet is the most important vector for accumulation of Rh and Pd, while accumulation of Pt appears to proceed mainly from the aqueous phase.     

The effects of biochars from rice residue on the formation of iron plaque and the accumulation of Cd, Zn, Pb, As in rice (Oryza sativa L.) seedlings

A historically multi-metal contaminated soil was amended with biochars produced from different parts of rice plants (straw, husk and bran) to investigate how biochar can influence the mobility of Cd, Zn, Pb and As in rice seedlings (Oryza sativa L.). Rice shoot concentrations of Cd, Zn and Pb decreased by up to 98%, 83% and 72%, respectively, due to biochar amendment, though that of As increased by up to 327%. Biochar amendments significantly decreased pore water concentrations (C_pw) of Cd and Zn and increased that of As. For Pb it depended on the amendment. Porewater pH, dissolved organic carbon, dissolved phosphorus, silicon in pore water and iron plaque formation on root surfaces all increased significantly after the amendments. The proportions of Cd and Pb in iron plaque increased by factors 1.8-5.7 and 1.4-2.8, respectively; no increase was observed for As and Zn. Straw-char application significantly and noticeably decreased the plant transfer coefficients of Cd and Pb. This study, the first to investigate changes in metal mobility and iron plaque formation in rice plants due to amending a historically contaminated soil with biochar, indicates that biochar has a potential to decrease Cd, Zn and Pb accumulations in rice shoot but increase that of As. The main cause is likely biochar decreasing the C_pw of Cd and Zn, increasing the C_pw of As, and increasing the iron plaque blocking capacity for Cd and Pb.     

论“三级三循环”耕地保护利益补偿模式的构建

我国耕地保护应更多侧重对耕地保护实施主体的内在激励,因此建立耕地保护利益补偿机制是实现我国切实保护耕地的关键环节。结合近期有关耕地保护利益补偿模式的研究成果,本文从耕地保护的外部性没有得到相应的经济体现、耕地保护政策损益补偿机制不健全、现行耕地保护的委托—代理机制具有较高的效率损失风险、耕地保护的区域差异性在经济上未得到有效体现、耕地资源价值核算不完善和由于比较利益的存在使得农户保护耕地的积极性不高等六大方面系统分析了我国现行耕地保护制度缺陷,提出了建立"三级三循环"耕地保护利益补偿模式的新思路。在此基础上,对"三级三循环"耕地保护利益补偿资金的筹集和使用、补偿主体、补偿标准、补偿方式等进行了详细论述。最后,从建立"三级"耕地保护基金管理委员会、对城镇居民开征耕地保护税、建立受偿农户耕地保护补偿账户体系以及加强对各级耕地保护基金管理委员会的监督管理等方面提出了政策建议。本文的分析结果对于推进我国耕地保护经济补偿,实现切实保护耕地目的具有一定的理论参考价值。     

Characterization of cadmium (Cd) distribution and accumulation in Tagetes erecta L. seedlings: Effect of split-root and of remove-xylem/phloem

Tagetes erecta has a high potential for cadmium (Cd) phytoremediation. Through several hydroponic experiments, characteristics of ¹⁰⁸Cd distribution and accumulation were investigated in T. erecta with split -roots or removed xylem/phloem. The results showed that ¹⁰⁸Cd transport from roots to aboveground tissues showed the homolateral transport phenomenon in split-root seedlings. ¹⁰⁸Cd content of leaves on the +¹⁰⁸Cd side and the −¹⁰⁸Cd side was not significantly different, which implied that there was horizontal transport of ¹⁰⁸Cd from the +¹⁰⁸Cd side to the −¹⁰⁸Cd side in cut-root seedlings. Like ¹⁰⁸Cd transport, the transport of ⁷⁰Zn was homolateral. Reduction of water consumption in the removed xylem treatment significantly decreased ¹⁰⁸Cd accumulation; whereas, the removed phloem treatment had no significant effect on water consumption, but did decrease ¹⁰⁸Cd accumulation in leaves of the seedlings. The removal of phloem significantly reduced distal leaf ¹⁰⁸Cd content, which was significantly lower than that in the basal leaves in both the split-root and unsplit-root seedlings. Overall, the results presented in this study revealed that the root to aboveground cadmium translocation via phloem is as an important and common physiological process as xylem determination of the cadmium accumulation in stems and leaves of marigold seedlings.