菲律宾蛤仔稚贝摄食、呼吸和排泄率的研究

本文利用实验生态学的方法研究了不同温度对菲律宾蛤仔稚贝的呼吸、排泄的影响以及在25℃下菲律宾蛤仔稚贝对4种单细胞藻类的滤食率．实验结果表明，温度对菲律宾蛤仔稚贝耗氧率、排氨率有显著影响，菲律宾蛤仔稚贝在12-32℃范围内，排氨率随温度的升高呈峰值变化，在26℃排氨率达到最大值然后开始下降，耗氧率随温度的升高而增大，耗氧率（OR）和温度（t）的回归方程为：OR=0．0155e^0.696t，R^2=0．9291．O：N也随着温度的升高而升高，菲律宾蛤仔稚贝呼吸Q10平均3．8，排泄Q10平均是1．88．菲律宾蛤仔稚贝在单位时问内（g／h）对4种藻类的滤食率高低依次为扁藻〉小球藻〉金藻〉角毛藻，差异极显著（P〈0．01）。     

Lognormality in the observed size distribution of oil and gas pools as a consequence of sampling bias

Economic filtration has been offered as an explanation of the observed lognormality in the size distribution of discovered oil and gas deposits. The result leads to the conclusion that one cannot impute the shape of the underlying parent distribution from the observed discoveries size distribution. The fact that the largest pools tend to be discovered early in the exploration history of an area of interest suggests the existence of an inherent sampling bias in the discovery process. The bias is influenced by the levels of geologic knowledge and technological sophistication. Furthermore, the existence of the bias leads to lognormality in the observed discoveries size distribution of oil and gas pools. A discovery process model explicitly incorporating the notion of sampling bias was applied to a series of Weibull parent frequency size distributions. The selected parent distributions are of a class suggested in the literature as more reflective of nature's size distribution and have empirical support. The distribution of discoveries resulting from the application of the model to the chosen parent size distributions were tested for lognormality using a chi-squared test. Lognormality was found to be an acceptable model of the discoveries size distribution over a wide range of resource exhaustion measures. When combined with the notion of economic filtration, sampling bias leads to the conclusion that one should not expect the lognormal distribution to accurately represent the underlying parent size distribution of oil and gas deposits.     

无纺土工织物保土应用中的概率设计准则

保土准则是土工织物反滤准则的重要组成部分,但目前的设计准则保土有余,透水不足。介绍了无纺土工织物的两种孔洞分布曲线,计算了土颗粒透过织物的概率。在理论分析的基础上,提出了一种概率保土准则。该准则对土体中的骨架颗粒和小颗粒透过织物的概率分别加以限制,既能保持土体稳定,又能防止淤堵。     

Shallow groundwater dynamics and its driving forces in extremely arid areas: a case study of the lower Heihe River in northwestern China

Shallow groundwater is an important source of water for the maintenance and restoration of ecosystems in arid environments, which necessitates a deeper understanding of its complex spatial and temporal dynamics driven by hydrological processes. This study explores the dominant hydrological processes that control the shallow groundwater dynamics in the Gobi Desert‐riparian‐oasis system of the lower Heihe River, a typical arid inland river basin located in northwestern China. The groundwater level and temperature were monitored in 14 shallow wells at 30‐min intervals during the 2010–2012 period. After combining this information with meteorological and hydrological data, a comprehensive analysis was conducted to understand the dynamic behaviour of the shallow groundwater system and to determine the dominant factors that control the groundwater flow processes. The results of the study indicate notably large temporal and spatial variations in both the groundwater level and temperature. Noticeable fluctuations in the groundwater level (0.5–1 m) and temperature (4–8 °C) were observed in the riparian zone, evidencing a clear river influence. In comparison, the groundwater fluctuations in the Gobi Desert were more stable (the annual variations of the water table were less than 0.5 m, and the water temperature varied by no more than 2 °C). Strong variations in the groundwater table (1.5–5.0 m/year) and temperature (1.5–6.5 °C), mainly caused by surface flood irrigation and groundwater pumping, were observed in the oasis area. The investigated sites were categorized into three types that reflect the dominant hydrological processes: (1) the riparian zone, dominated by riverbank filtration and groundwater evapotranspiration; (2) the Gobi Desert area, controlled by groundwater evaporation and lateral recharge; and (3) the oasis area, dominated by groundwater evapotranspiration as well as surface–groundwater interactions caused by human activities. Copyright © 2012 John Wiley & Sons, Ltd.     

ICP-MS测定甘肃某农场大气颗粒物中的铬、铜、砷、镉、铅含量

空气滤膜吸附采集甘肃某农场大气粉尘样品,采用盐酸—硝酸—氢氟酸—高氯酸溶解,电感耦合等离子体质谱法（ICP-MS）同时测定溶液中铬、铜、砷、镉、铅等重金属元素含量,分析农田环境大气颗粒中的重金属元素对农作物的影响,同时验证不同仪器工作参数对测定结果的影响。实验表明：在选定的实验条件下,分析元素的检出限低,准确性和精密度...     

天然河床渗滤取水工艺的原理与特点研究——以浠水南城水厂为例

渗滤取水净水机理主要是利用砂砾石层表面的泥膜及砂砾石层本身过滤作用、吸附作用,微生物的降解作用达到去除水中的悬浮物质、降低水的浊度、除菌的效果。以湖北浠水南城水厂渗滤取水工程为例,通过对渗滤工程特点和水质监测数据的研究,分析天然河床渗滤水水质及水源水水质的差异,以及渗滤水水质的可靠度。     

Purification and characterization of acetylcholinesterase from brain tissues of Oreochromis aurea and its application in environmental pesticide monitoring

Acetylcholinesterase (AChE) plays an important role in enzyme-based detection of pesticides in the environment. In this paper, AChE from the Triton X-100 extract of brain tissues of Oreochromis aurea was purified by (NH₄)₂SO₄ fractional precipitation, Sephadex G-100 gel filtration, and DEAE-cellulose ion exchange chromatography. Certain biochemical characterizations of the purified enzyme and inhibition of pesticides on the enzyme were also studied. The specific activity of this purified enzyme was 20.628 U/mg protein, fold of purification was 139, and recovery was 22.1%. The optimal temperature of this enzyme was between 35–40 °C, and optimal pH was between 7.5–8.0. The Michaelis constant (K_m) for acetylthiocholine iodide was 0.183 mmol/L. The enzyme activity was inhibited by excess substrate, and optimal substrate concentration was 6 mmol/L. Four pesticides (dichlorvos, phoxim, triazophos, and methomyl) exhibited strong inhibitions on this enzyme with IC₅₀ less than 5 μg/mL. This study suggests that Oreochromis aurea (tilapia) could be a good enzyme source for pesticide monitoring in water environments.     

地下水曝气-砂滤处理产生的废弃石英砂中铁砷含量与形态分布

高铁高砷地下水严重威胁饮水质量,曝气-砂滤法因处理效果好且成本低在农村地区得到广泛应用。砂滤过程石英砂表面富集铁和砷后需定期更换,然而废弃石英砂堆置具有砷释放风险。本文以江汉平原某水厂砂滤池废弃石英砂为研究对象,采用激光剥蚀-等离子体质谱(LA-ICP-MS)、拉曼光谱(Raman)、X射线衍射(XRD)和分步化学提取等手段,研究了砂样中的Fe和As含量及形态分布。结果表明,砂粒表面形成了一层厚度为20100 μm的高铁砷薄层,薄层内部Fe和As含量显著高于两侧,Fe和As分布高度相关(R²=0.985)。砂样表面铁矿物以无定型/弱结晶型为主,同时检出赤铁矿和臭葱石等矿物。砂样中Fe和As总含量分别为20.1 mg/g和53.4 μg/g。砂样表面铁主要以易溶解态、碳酸盐结合态和易还原态为主,As主要吸附在铁矿物上。研究区降雨充沛,当废弃石英砂遭遇雨水冲刷或淹没时,可能导致铁砷薄层中As解吸或随Fe矿物还原溶解而释放。     

单井水文地质参数简化计算及意义

单井抽水试验是水文地质勘探中广泛实施的手段,其导水系数 K M 或渗透系数 K 值通常是从抽水结果的涌水量 Q 和井中水位降数据计算求得.但单井中水量的水位降深,多受井结构完善程度的制约,难以反映出井点处含水层真实的水位降.另外,在基岩含水层试验中,常以抽水井揭露所谓含水层的岩性岩层厚度作为含水层厚,这又给 K 值的确定带来一定的偏差.就日常工作中在对抽水成果整理方面所遇的一些问题提出见解,以共讨论     

Dividing the algal soup: is there niche separation between native bivalves (Echyridella menziesii) and non-native Daphnia pulex in New Zealand?

ABSTRACT

New Zealand's native freshwater mussels (kākahi, kāeo) are considered to be in decline, yet the mechanisms driving this are unclear. The widespread establishment of highly efficient filter-feeding, non-native Daphnia in New Zealand lakes may have led to competition for algae with kākahi. We conducted a controlled laboratory experiment to determine whether differences exist in algal resources utilised by kākahi and North American Daphnia pulex. Echyridella menziesii (adults and juveniles) and D. pulex were exposed to mixed algal samples for three hours to determine whether similar algal resources were removed by the grazers. Relative to controls, both adult and juvenile E. menziesii removed a broad range of algal taxa including diatoms, green algae and filamentous species, ranging in size from 33.6 to 348.0?μm. High densities of D. pulex were unable to cause depletion of these same algae species. Our results suggest niche overlap is limited between the two grazers; E. menziesii utilises larger particles than D. pulex.