Zhang Manping

Comparative studies on nitrogen budgets of closed shrimp polyculture systems

April to October, 1997 comparative studies on the nitrogen budgets of closed shrimp polyculture systems showed that, in all the studied polyculture systems, nitrogen from feeds and fertilizers were the main input items, which comprised 70.7%–83.9% of the total input nitrogen 3.2%–7.4% of which was provided by nitrogen fixation. It was in monoculture enclosures (Y-4, Y-11 and Y-12) that the percentage reached the maximum value. The output nitrogen in harvested products comprised 10.8%–24.6% of total input nitrogen, and the highest percentage, 24.6%, was found in shrimp-fish-tagelus polyculture systems. In shrimp monoculture and shrimp-fish polyculture systems, they were 19.1% and 21.9% respectively. The nitrogen utilization efficiency was different and varied from 12.2% was found in shrimp-tagelus polyculture systems. The lowest, 12.2%, was found in shrimp monoculture systems. All the nitrogen utilization efficiencies in shrimp-fish systems or shrimp-scallop systems seemed to be higher than that of the monoculture system, but they showed little statistical difference. The main outputs of nitrogen were found in sediment mud, and comprised 48.2%–60.8% of the total, input, the lowest percentage was found in shrimp-fish-tagelus polyculture systems, and the highest percentage in shrimp-scallop systems. During the experiment, nitrogen lost through denitrification and ammonia volatilization comprised 1.9%–6. 2%, averaged 2.8%, of the total input, and the loss through seepage comprised 5.9%–8.9% of the total. The estimated nitrogen attached to the enclosure wall comprised 3.7%–13.3% of the total, and was highest in shrimp monoculture systems. Compared with the classic shrimp farming industry, the closed shrimp polyculture systems may improve the nitrogen utilization efficiency, and hence reduce the environmental impacts on coastal waters. The nitrogen discharging rates for all the studied polyculture systems ranged from 3.0% to 6. 0% of total input nitrogen.

Characterization of Dust and Non-dust Aerosols with SEM/EDX

Total suspended particulate (TSP) samples were collected at three sites along the coast of Qingdao, China, before and during a major dust storm in March, 2002. For comparison, PM10 (particulate matter with aerodynamic diameters less than 10 μm) samples were collected at one of the three sites. The morphological observation and compositional analysis of bulk and individual particles were performed by using scanning electron microscopy equipped with an energy dispersive X-ray system (SEM/EDX) for the TSP and PM10 samples. The results showed that the particles of different kinds of morphology had different elemental compositions, but the particles of similar morphology did not always have the same elemental composition for non-dust samples. The morphology and composition of non-dust particles were different at different sites. The fractal and spherical particles existed mainly in the coarse fraction for non-dust samples, while in the fine mode (<10 μm) there were floccules formed by fine particles flocking together and containing crustal elements. Compared with the non-dust particles, the dust particles were more homogeneous in terms of morphology, particle size and composition. Particles with irregular shapes and well-distributed sizes dominated in the dust samples, containing crustal elements such as Mg, Al, Si, Ca, Fe,etc. The high sulfur content indicated that homogeneous and heterogeneous reactions took place on the surfaces of the dust particles in the specific environment of Qingdao.

An electrochemical monitor for studying the kinetics of solid-liquid surface adsorption in seawater☆

Abstract This paper proposes a new device in which a single-sweep oscillographic polarograph can be used for the in-situ monitoring of the concentration of metal ions in stirred suspension systems. Usually, polarography is used in static solutions to avoid the effects of vibration. The device works as follows: in the standing time the device is opened to the stirred system and the concentration is homogeneous inside and outside the device. The device is closed before potential scanning of the dropping mercury electrode, so that the solution within it remains static and the polarographic measurement can be carried out. The influence of oxygen is minimized by use of the second-order derivative mode in the polarographic determination. This technique has the advantages of simplicity, speed and reproducibility.

Heavy metal complexation capacity of the South China Sea water

The seawater complexation capacity for heavy metals (copper, lead and cadmium) in the South China Sea was determined by anodic voltammetry and the conditional stability constants of these complexes were calculated. The data showed that the complexation capacity of the South China Sea water was greater than that of seawater in the Huanghe Estuary and the coast water of Qingdao. The sequence of complexation capacity is C (CuL)>C(PbL)>C(CdL), and the conditional stability constants were in an opposite sequence: K(CuL)<K(PbL)<K(CdL).The types, and shapes of the complexation capacity profiles for Cu, Cd and Pb were similar to those obtained by Buckley (1986) for the Atlantic Ocean water. Complexation capacity is maximum at the surface layer, decreasing with depth, reaching minimum at 750m, but increasing again near the sea bottom.

Pelagic nitrogen cycling in Jiaozhou Bay, a model study I: The conceptual model

A zero-dimensional box model (PNCMjzb) with six state variables (ammonium, nitrate, dissolved organic nitrogen, phytoplankton, zooplankton and detritus) was developed to study nitrogen cycling in the Jiaozhou Bay pelagic ecosystem. The dominant processes within these compartments are considered with nitrogen as flow currency. Phytoplankton and zooplankton are treated as separate state variables, assuming that the species composition was dominated by two or three species the dynamic constants of which are similar and that they represent the entire plankton community. The microbial loop has not been integrated explicitly in the model. The turnover of bacteria is included implicitly in processes such as detritus decomposition, DON remineralization, pelagic nitrification and denitrification. The model is driven by two forcing variables, viz. water temperature and light intensity. Historical data from the 1980s and 1990s were compiled and used for model calibration. In this paper (part I), the consideration of every main compartment in the model is interpreted in detail. And the applied equations and parameters are presented. The main results from the simulations together with discussion about phytoplankton dynamics and primary production in Jiaozhou Bay are presented in the next paper (part II).

Study on the dimethylsulfide and dimethylsulfoni-opropionate in algae by laboratory batch cultures

The effects of selected environmental variables on the production of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) by laboratory batch cultures of microalgae were studied. The variations of DMS and DMSP output with algae growth and variations in nutrients and salinity are reported.

Simple simulation of the annual variation of the specific photosynthesis rate in Jiaozhou Bay

A simple diagnostic simulation of the annual cycling of the surface specific photosynthesis rate (SPR) in Jiaozhou Bay is described in this paper. Light intensity, temperature and nutrients (nitrate+ammonia, phosphate) were considered as main factors controlling photosynthesis of phytoplankton and were introduced into the model by different function equations. The simulated variation of specific photosynthesis rate coincided with the measured data. Analysis of the effect of every factor on photosynthesis indicated that the variation of photosynthesis rate was controlled by all these three factors, while temperature showed good correlation with SPR as measurement showed. This diagnostic simulation yielded the values of some parameter relating with the photosynthesis in Jiaozhou Bay.

Numerical modelling for offshore platform cathodic protection-local system

This paper discusses numerical methods for modelling cathodic protection (CP) using Boundary Element Methods(BEM) for CP design analysis in comparision with the traditional mtthods and presents several mathematical models (for CP design in 3-D infinite area) solvable by using BEM with microcomputer.

Study on the relationship between speciation of heavy metals and their ecotoxicity

Heavy metal is a main pollutant in the marine ecosystem, so study on the effect of heavy metal on phytoplankton is important. Algae (Chaetoceros sp.,Dunaliella sp.,Dicrateria zhanjiangenis Hu. var. sp.) were laboratory cultured to observe the effect of heavy metals on their growth. The effect of different metal ion concentration, the detoxication effect of complexation agents and the growth of algae in different media and different nutrition levels were studied to evaluate the effect of metal speciation. It is proved that trace amount of heavy metals can stimulate the growth of algae cells but that high concentration is lethal. The sequence of toxicity is Cd2+>Zn2+>Pb2+. In ordinary nutrition conditions, the detoxication sequence of complexation agents toChaetoceros sp. is EDTA >sodium salicylate>sodium oxalate >sodium citrate>sulfanilic acid>O-phenanthroline. This is in good conformity with the stability constant sequence of these agents with copper and good evidence that toxicity of metal ion is related to its activity and not to its total concentration.