Metal leaching and toxicity of denitrifying woodchip bioreactor outflow—Potential reuse application

The denitrifying woodchip bioreactor is designed to remediate nitrate-rich water, including those produced from aquaculture effluents. Reuse of treated bioreactor outflows in recirculating aquaculture would offer considerable water savings and valuable alkalinity recuperation. However, such bioreactors may leach detrimental wood-bound contaminants, preventing outflow reuse. To determine water reuse potential, woodchip media from two hardwood species (white ash, Fraxinus americana; Norway maple, Acer platanoides) were evaluated for 206 d under a range of operating conditions (start-up, steady-state, reducing conditions, and drying-rewetting cycles) for a spectrum of potentially harmful dissolved contaminants. Aerated outflows also were evaluated for acute and chronic toxicity to the biologically sensitive invertebrate Ceriodaphnia dubia. Dissolved metal leaching subsided within the first few weeks of operation, though initial concentrations of copper and zinc were detected at concentrations of concern. Elevated concentrations of tannins-lignin and total ammonia nitrogen were detected throughout the study and were influenced by operational phase. Acute toxicity was not generally detected, though chronic toxicity was observed during drying-rewetting cycles in the maple outflows. The measured toxicity was not correlated with water chemistry, indicating an additive effect of several toxicants. Overall, significant differences in outflow water quality between ash and maple wood species were negligible. Results indicated that bioreactor outflows may be applicable for aquacultural reuse, though reusing outflows immediately following start-up or restarting after a dry period would not be recommended.     

Reproduction in three species of rainbowfish (Melanotaeniidae) from rainforest streams in northern Queensland, Australia

Abstract – The reproductive biology of three species of rainbowfish (Melanotaeniidae) in northeastern Australian rainforest streams was investigated. Two species, Melanotaenia eachamensis and Cairnsichthys rhombosomoides are endemic to the area, whereas the third, M. splendida splendida, is more widespread. The species were all highly fecund, producing many hundreds of eggs between 1.10 and 1.24 mm in diameter. Melanotaenia eachamensis was the most fecund, produced the largest eggs of the three species, and consequently exhibited the greatest maternal investment (as measured by gonadosomatic index). The majority of reproductive effort occurred during the dry season, although reproductively active fish were present year-round for each of the species, but particularly so for M. s. splendida and C. rhombosomoides. No evidence for a role by temperature or photoperiod as environmental cues for reproduction was found, and it was suggested that gonad development was strongly tied to somatic growth. The concentration of reproduction to the dry season ensures that larvae are produced during a period of relatively stable and benign physical conditions. Comparison of temporal changes in gonadosomatic index values suggest that the spawning season of M. eachamensis , which occurs in high-elevation streams, is more restricted and commences about 1 month earlier than either other species. A similar phenology was observed for the M. s. splendida population found at high elevation and highlights the potential for spatial differences in stream productivity to influence life history. ^Note     

河北省天然草地禾本科植物的生活型、生态型及区系分析

对河北省天然草地禾本科植物的生活型、生态型及区系特征进行了分析，结果表明，多年生草本为优势生活型，占78．4％；生态型以中生植物为主，占77．2％，旱生植物占16．0％，湿生植物仅占6．8％；植物区系成分多样，温带分布属最多达42属，占总属数的57．5％，其次为热带分布属，有24属，占32．9％。     

美国白蛾生物学特性的研究

通过对美国白蛾的生活史、生活习性,各龄幼虫的鉴别特征、卵的发育温度、各龄幼虫的耐饥力及蛹重与携卵量关系的观察研究,提出了蛹重与携卵量关系的直线回归模型: Y=-580.07+5704.28x.     

塔里木盆地北缘植被生活型组成的分析

塔里木盆地北缘地区共记录野生植物123种,在其生活型组成中,地面芽植物居首位,达35.6%,次为一年生植物占22.7%,表现本区植被具有温带荒漠的特殊属性。塔里木盆地为我国最干旱的内陆盆地。这一区域的环境及生物群的特点曾引起有关学者的广泛兴趣。上世纪末至本世纪初,普热瓦尔斯基、别夫佐夫、罗布拉夫斯基等曾先后在新疆进行考察,斯文赫定和斯坦因曾对胡杨作过描述,谢彬曾论及胡杨的分布。1957至1958年间,中国科学院新疆综考队对塔里木盆地的环境和植被进行了大量的工作。此后     

水电站虹吸式进水口的控制

在对河北省几座已建虹吸式进水口水电站的虹吸控制方式进行分析对比的基础上,给出了一种采用液气射流泵将虹吸体抽成“低管”正虹吸,用“Y”形管中的水封保持真空,事故时利用“高管”自动补气破坏真空的控制系统,并分析了该系统的特点,给出了设计计算方法及计算公式。     

舍饲安哥拉周岁公羊行为习性观察

对 6只舍饲安哥拉周岁公羊进行连续三天昼夜行为习性观察 ,结果表明 :周岁安哥拉山羊在舍饲情况下每昼夜反刍时间 (min)为 45 7 2 5± 2 4 39,睡眠时间为 2 96 5 0± 41 5 0 ,采食时间为 2 65 0 0± 2 2 31,其他时间为 15 4 2 5± 72 76。反刍与采食的时间比为 1 7∶1,明显大于正常的反刍与采食比 (0 5～ 1)的上限。反刍、睡眠和采食也与其它山羊相差较大。周岁安哥拉山羊的反刍、睡眠多发生在夜间 ,采食活动及其它一些动作如打架、自淫多发生在白天。安哥拉山羊白天排粪、排尿次数多于黑夜 ,昼夜排粪次数差异极显著。安哥拉山羊对牧草及灌木有较强的选择性 ,对饮水的卫生要求极为严格 ,拒饮不干净的水     

更新林相图的计算机辅助方法

常规编制与更新林相图的方法要求昂贵的光学机械纠正仪器、较高的操作技术和成本。文章提出一种利用计算机辅助纠正航空象片更新林相图的方法,可以降低成本,提高成图效率。为了实现这种方法,首先根据航空摄影理论分析,推导出适合编程的航空纠正数字化线性模型和算法。该模型要求在底图和航片上有四对控制点坐标,求算纠正参数。采用数字化仪测定这些坐标,求解参数,然后根据该线性模型对航片上编图要素的数字化坐标进行非共面变换,进而更新林相图。为完成这一过程需要四个程序模块和处理流程。使用这种方法更新林相图既能保证精度要求,又具有操作简单的优点。     

Comparison of kinetic properties of a hydrophilic form of acetylcholinesterase purified from strains susceptible and resistant to carbamate and organophosphorus insecticides of green rice leafhopper (Nephotettix cincticeps Uhler)

A hydrophilic form of acetylcholinesterase (AChE) was purified from N-methyl carbamate susceptible (SA) and highly N-methyl carbamate-resistant (N3D) strains of the green rice leafhopper (GRLH), Nephotettix cincticeps Uhler. Both of purified AChE from SA and N3D strains displayed the highest activities toward acetylthiocholine (ATCh) at pH 8.5. In the SA strain, the optimum concentrations for ATCh, propionylthiocholine (PTCh), and butyrylthiocholine (BTCh) were about 1 × 10⁻³, 2.5 × 10⁻³, and 1 × 10⁻³ M, respectively. However, in the N3D strain, substrate inhibition was not identified for ATCh, PTCh, and BTCh to 1 × 10⁻² M. The K_m value in the SA strain was 51.1, 39.1, and 41.6 μM and that in the N3D strain was 91.8, 88.1, and 85.2 μM for ATCh, PTCh, and BTCh, respectively. The K_m value in the N3D strain indicated about 1.80-, 2.25-, and 2.05-fold lower affinity than that of the SA strain for ATCh, PTCh, and BTCh, respectively. The V_max value in the SA strain was 70.2, 30.5, and 4.6 U/mg protein and that in the N3D strain was 123.0, 27.0, and 14.5 U/mg protein for ATCh, PTCh, and BTCh, respectively. The V_max value in the N3D strain was 1.75- and 3.15-fold higher for ATCh and BTCh than that in the N3D strain. However, it was 1.13-fold lower for PTCh. The increased activity of AChE in the N3D strain is due to the qualitatively modified enzyme with a higher catalytic efficiency. The bimolecular rate constant (k_i) for propoxur was 27.1 × 10⁴ and 0.51 × 10⁴ M⁻¹ min⁻¹ in the SA and N3D strain and that for monocrotophos was 0.031 × 10⁴ and 2.0 × 10⁴ M⁻¹ min⁻¹ in the SA and N3D strain. AChE from the N3D strain was 53-fold less sensitive than SA strain to inhibition by propoxur. In contrast, AChE from the N3D strain was 65-fold more sensitive to inhibition by monocrotophos than AChE from the SA strain. This indicated negatively correlated cross-insensitivity of AChE to propoxur and monocrotophos.