坡地赤红壤物理退化及其机理研究──Ⅲ.土壤物理退化机理分析

主要通过相关统计和综合分析，探讨坡地赤红壤物理退化的内部和外部环境的影响因素．指出养分贫瘠化，尤其是贫有机质化是坡地赤红壤物理性状退化的主要内部原因，植被破坏则是坡地赤红壤物理性状退化的外部因素、而人类活动的影响对坡地赤红壤的物理退化有重要作用。     

丹阳市宅基地使用权流转意愿的影响因素及相互作用

通过丹阳市4个村320户农户实地问卷调查，分析了丹阳市宅基地使用权流转意愿的影响因素，由Logistic回归分析模型，给出了影响因素的驱动力、贡献率的数学表达。结果表明：文化程度、宅基地个数、家庭总收入等影响因素对流转意愿呈正相关；户主年龄、家庭人口数量等影响因素对流转意愿呈负相关。同一农户的影响因素在不同阶段对流转意愿度的贡献率不同，家庭收入和户主年龄是影响宅基地流转的主要因素，他们对宅基地流转分别起着推力和阻力作用，在相互作用过程中，两者之间彼此消长。实地抽样结果分析表明，丹阳农村户主文化程度若为初中且年龄在35岁时，家庭收入能达到34 000元的话，宅基地使用权流转意愿度超过50%。以后每年家庭收入能有一定增速的话，农户流转意愿度将持续保持在50%以上。     

Examining the joint toxicity of chlorpyrifos and atrazine in the aquatic species: Lepomis macrochirus, Pimephales promelas and Chironomus tentans

The joint toxicity of chlorpyrifos and atrazine was compared to that of chlorpyrifos alone to discern any greater than additive response using both acute toxicity testing and whole-body residue analysis. In addition, acetylcholinesterase (AChE) inhibition and biotransformation were investigated to evaluate the toxic mode of action of chlorpyrifos in the presence of atrazine. The joint toxicity of atrazine and chlorpyrifos exhibited no significant difference in Lepomis macrochirus compared to chlorpyrifos alone; while studies performed with Pimephales promelas and Chironomus tentans, did show significant differences. AChE activity and biotransformation showed no significant differences between the joint toxicity of atrazine and chlorpyrifos and that of chlorpyrifos alone. From the data collected, the combination of atrazine and chlorpyrifos pose little additional risk than that of chlorpyrifos alone to the tested fish species.     

常见金属硫化物电化学反应环境效应及其影响因素分析

金属硫化物矿物作为重要的金属矿产资源之一,在自然界广泛分布并易氧化(电化学反应)引起重金属离子和酸性矿山废水污染的环境效应。本文以黄铁矿和黄铜矿为例全面分析了金属硫化物矿物环境效应产生机制,以及影响金属硫化物矿物电化学反应的各种因素,指出了当前研究存在的不足。这对金属硫化物矿区环境污染的源头控制与修复具有重要的指导意义。     

重庆三叠系碳酸盐岩热储热水水文地球化学特征

地下热水的水文地球化学特征研究有利于地下热水的开发,对重庆三叠系碳酸盐岩热储热水的研究可以更好地实现重庆地下热水的可持续开发。通过2009年1月和2009年7月对重庆市三叠系碳酸盐岩热储热水进行野外监测、取样和室内分析,发现重庆三叠系碳酸盐岩热储热水水化学性质相近,pH呈中性,水温30℃~50℃,电导率为1 320 μs/cm~3 250 μs/cm,水化学类型为SO₄-Ca(Mg)型,是典型的碳酸盐岩热储中-低温地下热水。温泉水的主要阳离子为Ca²⁺和Mg²⁺,阴离子为SO₄^2-和HCO₃^-,除青木关温泉外,SO₄^2-和Ca²⁺、Mg²⁺随时空变化较小,体现了碳酸盐岩中石膏与地下热水的水-岩作用对地下热水水文地球化学特征的控制。热水中的方解石和白云石都处于饱和与不饱和的临界状态,没有明显钙华沉积的现象;Na-K-Mg-Ca图解显示各个季节地下热水的物质来源基本一致,均没有达到水岩平衡状态。     

营养物质对铜绿微囊藻生长和藻际细菌的影响

菌-藻"体系在水生态平衡中发挥重要作用,为探明蓝藻水华时期的菌藻关系,研究了原位营养刺激后藻际微生物对铜绿微囊藻生长的影响.结果表明,LB培养基可抑制铜绿微囊藻生长,抑藻率为86.49%;而乙酸钠、葡萄糖和柠檬酸钠可促进藻细胞生长,增长率均在50%以上.对LB培养基和蛋白胨刺激后的藻际细菌进行溶藻菌的筛选,共分离出6株具有强效抑藻作用的菌株,其中Bacillus sp.A1抑藻率高达97.55%.16S rRNA高通量测序表明,向铜绿微囊藻中投加营养物质均可改变藻际细菌群落结构并增加物种丰富度,添加LB培养基和蛋白胨可促使藻际细菌群落数量剧增.生理生化响应表明,藻细胞受LB培养基和蛋白胨胁迫后,活性氧（ROS）水平和丙二醛（MDA）含量激增,细胞氧化损伤严重;超氧化物歧化酶（SOD）、过氧化氢酶（CAT）活性先急剧上升后下降,抗氧化酶系统受损.扫描电镜显示,LB培养基可使藻细胞逐渐萎缩,最终破碎;而藻际细菌显著增多.因此,在蓝藻水华暴发的水体进行适当的外部营养刺激可在一定程度上实现溶藻菌原位抑藻.     

不同密度螺-草结构对养殖尾水净化效果的比较研究

为减少水产养殖污染物排放，以苦草为对照组，构建环棱螺螺 草生态系统净化池塘养殖尾水，比较不同密度螺 草结构对养殖尾水的净化效果，同时探讨螺草互作对水质的影响。结果表明不同密度螺 草组合对养殖尾水均有较好的净化效果，以中密度组（螺密度50 ind/m3）的去除效果最优，25 d对Chl a、CODMn、TN、TP、NH4+ N、NO3- N和浊度的去除率分别达到98%、39.7%、44.2%、86.9%、58.2%、82.3%和91%，其中以17~25 d的营养物质去除率最高，水质由原来的Ⅳ类、Ⅴ类水提升为Ⅲ类水；环棱螺 苦草互作对水体的净化效果与苦草对照组差异不显著，表明其互利关系不明显；环棱螺 苦草组合对CODMn和TN的去除效果不是很理想，可能是由于实验中以黄土为底泥，其中的异养微生物较少引起的     

Perceived Effects of Setting Attributes on Visitor Experiences in Wilderness: Variation with Situational Context and Visitor Characteristics

Understanding how setting attributes influence the nature of the visitor experience is crucial to effective recreation management. Highly influential attributes are useful indicators to monitor within a planning framework, such as Limits of Acceptable Change. This study sought to identify the setting attributes perceived to have the most profound effect on the ability to have “a real wilderness experience” and to assess the degree to which attribute importance varied with situational context and visitor characteristics. To this end, exiting hikers were surveyed at moderate and very high use trailheads in Alpine Lakes Wilderness, WA (USA), and Three Sisters Wilderness, OR (USA). They were asked about the degree to which encountering varying levels of different setting attributes would add to or detract from their experience. Attributes with the largest range of effect on experience, based on evaluations of different levels, were considered most important. The most influential attributes were litter and several types of campsite interaction—people walking through camp and number of other groups camping close by. The perceived importance of setting attributes did not vary much between wilderness locations with substantially different use levels, suggesting that conclusions are robust and generalizable across wilderness areas. There also was little difference in the perceptions of day and overnight visitors. In contrast, we found substantial variation in the perceived importance of setting attributes with variation in wilderness experience, knowledge, attachment, and motivation. Our results validate the emphasis of many wilderness management plans on indicators of social interaction, such as number of encounters.     

System Dynamics to Sustainable Water Resources Management in the Eastern Snake Plain Aquifer Under Water Supply Uncertainty1

Abstract: Water supply uncertainty continues to threaten the reliability of regional water resources in the western United States. Climate variability and water dispute potentials induce water managers to develop proactive adaptive management strategies to mitigate future hydroclimate impacts. The Eastern Snake Plain Aquifer in the state of Idaho is also facing these challenges in the sense that population growth and economic development strongly depend on reliable water resources from underground storage. Drought and subsequent water conflict often drive scientific research and political agendas because water resources availability and aquifer management for a sustainable rural economy are of great interest. In this study, a system dynamics approach is applied to address dynamically complex problems with management of the aquifer and associated surface‐water and groundwater interactions. Recharge and discharge dynamics within the aquifer system are coded in an environmental modeling framework to identify long‐term behavior of aquifer responses to uncertain future hydrological variability. The research shows that the system dynamics approach is a promising modeling tool to develop sustainable water resources planning and management in a collaborative decision‐making framework and also to provide useful insights and alternative opportunities for operational management, policy support, and participatory strategic planning to mitigate future hydroclimate impacts in human dimensions.     

Poisoned plusiines: toxicity of milkweed latex and cardenolides to some generalist caterpillars

Summary. Larvae of Trichoplusia ni Hübner (Lepidoptera: Noctuidae) that ingested latex from Asclepias curassavica L. (Asclepiadaceae) often regurgitated and convulsed with spasms before becoming immobile and unresponsive. Some larvae required over a day to recover sufficiently to feed. Latices from four other plant species in three families were all deterrent, but none caused detectable poisoning. The toxicity of A. curassavica latex was evidently due to cardenolides because pure cardenolides had similar effects when ingested by T. ni. Other species of noctuid caterpillars (Rachiplusia ou Guenée, Anagrapha falcifera Kirby, and Autographa precationis Guenée) sometimes also suffered spasms and temporary immobility when fed A. curassavica latex. A more distantly related noctuid, Spodoptera ornithogalli, was deterred by the latex, but showed no overt physiological responses at the dosage tested. T. ni larvae failed to develop on intact leaves of A. curassavica, on leaves with latex canals deactivated by midrib severance, and on excised leaves. Similarly, larvae reared on excised A. syriaca L. leaves to the final instar died when transferred to A. curassavica leaves with either intact or severed midribs. The final instar larvae sometimes suffered from spasms and immobility even when confined on leaves with depressurized canal systems. Evidently, cardenolides stored outside the latex system suffice to poison larvae. We conclude that cardenolides in A. curassavica have potent physiological effects on some generalist caterpillars and that the presence of these compounds both inside and outside laticifers effectively protects the plant. Received 30 June 1999; accepted 18 October 1999