Long-term changes in crustacean zooplankton and water quality in a shallow, eutrophic Chinese lake densely stocked with fish

From surveys made in 1962-1963, 1973-1974, 1979-1996 at two Stations in Lake Donghu, a shallow eutrophic water body near Wuhan, P. R. China, the authors, derive long-term changes in species composition, standing crop and body-size of planktonic crustaceans. The species number decreased from the 1960s to the 1990s. The cladocerans dropped from 46 (1960s) to 26 (1980s) to 13 (1990s); the copepods decreased from 14 (1960s) to 10 (1980s) to 7 (1990s). From the mid-1980s on, the dominant crustaceans also changed: Daphnia hyalina and D. carinata ssp. were replaced by Moina micrura and Diaphanosoma brachyurum at Stations 1 and 2, respectively; Cyclops vicinus replaced Mesocyclops leuckarti. Densities and biomass of Cladocera decreased markedly after 1987. Annual average densities and biomass of cladocerans were statistically differences between 1962-1986 and 1987-1996 (P < 0.01). Annual average densities of Daphnia (Station 1 + Station 2) were negatively correlated with fish yield. Since the 1980s, annual average body length of Cladocera and Calanoida decreased, while annual average body length of Cyclopoida increased. In the same years, average body length of copepods was lower during May-October than during January-April and November-December. A 12-yr data analysis showed annual average concentration of chlorophyll-a (Chl-a) to be negatively correlated with annual average density of Daphnia, whilst lake transparency was positively correlated with annual average densities of Daphnia. The results imply that, since Daphnia feeds efficiently on phytoplankton, it could decrease concentration of Chl-a, and enhance water transparency.

Effects of silver carp density on zooplankton and water quality: Implications for eutrophic lakes in China

We examined the responses of zooplankton community, water transparency, chlorophyll a and nutrients to manipulation of density of silver carp (Hypophthyalmichthys molitrix) in an one-way factorial experiment using enclosures placed in Donghu (East Lake, 30 degrees 33' N, 114 degrees 23' E), located in Wuhan, P. R. China. Enclosures (18.75 m(3)) were treated with four silver carp densities, 0, 81, 225, 485 g/m(2). Total zooplankton abundance (excluding nauplii and rotifers except for Asplanchna sp.) and the mean size of dominant cladoceran species were significantly greater in enclosures with 0 and 81 fish densities than those in enclosures with 225 and 485 fish densities. Water transparency also improved significantly when silver carp densities were 0 or 81 g/m(2). We did not find significant effects of silver carp density on chlorophyll a, total phosphorus, or total nitrogen concentrations. We conclude that by reducing planktivorous fish to below the current density (190 g/m(2)), the zooplankton community can be shifted from the dominance of small-bodied Moina sp. to dominance of large-bodied Daphnia sp. Further, the water clarity can be increased.

Abatement of waste gases and water during the processes of semiconductor fabrication

The purpose of this article is to examine the methods and equipment for abating waste gases and water produced during the manufacture of semiconductor materials and devices. Three separating methods and equipment are used to control three different groups of electronic wastes. The first group includes arsine and phosphine emitted during the processes of semiconductor materials manufacture. The abatement procedure for this group of pollutants consists of adding iodates, cupric and manganese salts to a multiple shower tower (MST) structure. The second group includes pollutants containing arsenic, phosphorus, HF, HCl, NO2, and SO3 emitted during the manufacture of semiconductor materials and devices. The abatement procedure involves mixing oxidants and bases in an oval column with a separator in the middle. The third group consists of the ions of As, P and heavy metals contained in the waste water. The abatement procedure includes adding CaCO3 and ferric salts in a flocculation-sedimentation compact device equipment. Test results showed that all waste gases and water after the abatement procedures presented in this article passed the discharge standards set by the State Environmental Protection Administration of China.

Electron diffraction and photoemission studies of clean and water-covered Si(5,5,12) and Si(112) surfaces

The structure of silicon surfaces in the orientation range (113)-(5,5,12)-(337)-(112) has been investigated using high resolution LEED and photoemission both on a spherical and on flat samples. We find that Si(5,5,12) [5.3 degrees from (113) and 0.7 degrees from (937)] is the only stable orientation between (113) and (111) and confirm the result of Baski et al. [Science 269, 1556 (1995)] that it has a 2 x 1 superstructure with a very large unit cell of 7.68 x 53.5 Angstrom(2). Adsorption measurements of water on Si(5,5,12) yield a mobile precursor kinetics with two kinds of regions saturating at 0.25 and 0.15 ML which are related to adsorption on different sites. Using these results, a modified structure model is proposed. Surfaces between (113) and (5,5,12) separate into facets of these two orientations; between (5,5,12) and (112), they separate into (5,5,12) and (111) facets. (337) facets in this range may be considered as defective (5,5,12) facets.

requirement analysis of information and knowledge management in postmodern perspective on curriculum

National Basic Research Program of China; Chinese Academy of Sciences; Information Society Technologies; Institute of Computing Technology, Chinese Academy of Sciences; Zhuhai National Hi-tech Industrial Development Zone

Fabrication of Novel Superhydrophobic Surfaces and Water Droplet Bouncing Behavior - Part 1: Stable ZnO-PDMS Superhydrophobic Surface with Low Hysteresis Constructed Using ZnO Nanoparticles

A superhydrophobic surface has many advantages in micro/nanomechanical applications, such as low adhesion, low friction and high restitution coefficient, etc. In this paper, we introduce a novel and simple route to fabricate superhydrophobic surfaces using ZnO nanocrystals. First, tetrapod-like ZnO nanocrystals were prepared via a one-step, direct chemical vapor deposition (CVD) approach. The nanostructured ZnO material was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) and the surface functionalized by aminopropyltriethoxysilane (APS) was found to be hydrophobic. Then the superhydrophobic surface was constructed by depositing uniformly ZnO hydrophobic nanoparticles (HNPs) on the Poly(dimethylsiloxane) (PDMS) film substrate. Water wettability study revealed a contact angle of 155.4 +/- 2 degrees for the superhydrophobic surface while about 110 degrees for pure smooth PDMS films. The hysteresis was quite low, only 3.1 +/- 0.3 degrees. Microscopic observations showed that the surface was covered by micro- and nano-scale ZnO particles. Compared to other approaches, this method is rather convenient and can be used to obtain a large area superhydrophobic surface. The high contact angle and low hysteresis could be attributed to the micro/nano structures of ZnO material; besides, the superhydrophobic property of the as-constructed ZnO-PDMS surface could be maintained for at least 6 months. (C) Koninklijke Brill NV, Leiden, 2010