Processing network models of energy/environment systems

Processing networks are a variant of the standard linear programming network model which are especially useful for optimizing industrial energy/environment systems. Modelling advantages include an intuitive diagrammatic representation and the ability to incorporate all forms of energy and pollutants in a single integrated linear network model. Added advantages include increased speed of solution and algorithms supporting formulation. The paper explores their use in modelling the energy and pollution control systems in large industrial plants. The pollution control options in an ethylene production plant are analyzed as an example. PROFLOW, a computer tool for the formulation, analysis, and solution of processing network models, is introduced.

Density-dependent effects on seston dynamics and rates of filtering and biodeposition of the suspension-cultured scallop Chlamys farreri in a eutrophic bay (northern China): An experimental study in semi-in situ flow-through systems

Effects of stocking density on seston dynamics and filtering and biodeposition by the suspension-cultured Zhikong scallop Chlamys farreri Jones et Preston in a eutrophic bay (Sishili Bay, northern China), were determined in a 3-month semi-field experiment with continuous flow-through seawater from the bay. Results showed that the presence of the scallops could strongly decrease seston and chlorophyll a concentrations in the water column. Moreover, in a limited water column, increasing scallop density could cause seston depletion due to scallop's filtering and biodeposition process, and impair scallop growth. Both filtration rate and biodeposition rate of C. farreri showed significant negative correlation with their density and positive relationship with seston concentration. Calculation predicts that the daily removal of suspended matter from water column by the scallops in Sishili Bay ecosystem can be as high as 45% of the total suspended matter; and the daily production of biodeposits by the scallops in early summer in farming zone may amount to 7.78 g m(-2), with daily C, N and P biodeposition rates of 3.06 x 10(-1), 3.86 x 10(-2) and 9.80 x 10(-3) g m(-2), respectively. The filtering and biodeposition by suspension-cultured scallops could substantially enhance the deposition of total suspended particulate material, suppress accumulation of particulate organic matter in water column, and increase the flux of C, N and P to benthos, strongly enhancing pelagic-benthic coupling. It was suggested that the filtering-biodeposition process by intensively suspension-cultured bivalve filter-feeders could exert strong top-down control on phytoplankton biomass and other suspended particulate material in coastal ecosystems. This study also indicated that commercially suspension-cultured bivalves may simultaneously and potentially aid in mitigating eutrophication pressures on coastal ecosystems subject to anthropogenic N and P loadings, serving as a eutrophic-environment bioremediator. The ecological services (e.g. filtering capacity, top-down control, and benthic-pelagic coupling) functioned by extractive bivalve aquaculture should be emphasized in coastal ecosystems. (c) 2005 Elsevier B.V. All rights reserved.

Cross-shelf circulation in the Yellow and East China Seas indicated by MODIS satellite observations

Ocean color and sea surface temperature data from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra satellite are used to study the cross-shelf circulation and transport of suspended sediments in the Yellow and the East China Seas. The ocean color images show a significant turbid water plume extending in the southeast direction from the Subei coasts of China to the shelf edge south of Cheju during fall-winter, suggesting significant cross-shelf currents in the Yellow Sea/East China Sea in winter. The currents transport suspended sediments from the area of the old Huanghe mouth into the Okinawa Trough. Part of the turbid plume joins the Yellow Sea Warm Current to enter the Yellow Sea trough in winter. The satellite images suggest that the time scales of cross-shelf transport and surface-to-subsurface descending of the suspended sediments are a few weeks. The turbid plume grows in fall, reaches its maximum expansion and intensity in winter-spring, and subsides in late spring. In summer, the plume becomes coastally trapped. Substantial interannual variations of the intensity and coverage of the turbid plume are indicated by the observations. In comparison, the Changjiang Diluted Water in summer only transports a small amount of the Changjiang suspended sediment to the outer shelf south of Cheju, which does not enter the Yellow Sea owing to the weak intrusion of the Yellow Sea Warm Current in summer. The dynamics of the cross-shelf circulation in the Yellow Sea in winter are hypothesized to be associated with (1) the convergence of the Yellow Sea Coastal Current and the Taiwan Warm Current off the Changjiang mouth and (2) the time-dependent forcing of the northerly wind bursts that drives the intrusion of the Yellow Sea Warm Current. (C) 2007 Elsevier B.V. All rights reserved.

Geochemical characteristics of nitrogen in the southern Yellow Sea surface sediments

Roles and distributions of various forms of nitrogen in biogeochemical cycling in the southern Yellow Sea surface sediments were investigated. The southern Yellow Sea could be divided into three regions (I, II and III) according to the proportion of fine-grained sediment in > 65%, 35-65% and < 35%, respectively. The ratios of different forms of nitrogen contents between each two of the three regions indicated that the nitrogen contents increased with the proportion of fine-grained sediment increasing. The quanta of exchangeable forms of nitrogen were similar in the three regions, while their releasing time increased from regions I to III, indicating that the cycle of nitrogen in fine-grained sediments was shorter than that in coarse-grained sediments. Nitrogen burial fluxes were also similar in these regions, while the burial efficiency increased from regions I to III. The highest burial efficiency was 30.21% in region III, indicating that more than 70% of nitrogen in the southern Yellow Sea surface sediments could be released to take part in biogeochemical recycling. When all the four forms of exchangeable nitrogen (nitrogen in ion exchangeable form (IEF-N), nitrogen in weak acid extractable form (WAEF-N), nitrogen in strong alkali extractable form (SAEF-N) and nitrogen in strong oxidant extractable form (SOEF-N)) were released to take part in recycling, their potential contributions were 80% (SOEF-N), 11% (IEF-N), 6% (SAEF-N), 3% (WAEF-N) respectively, which showed that SOEF-N was the predominant one, and its contribution to biogeochemical cycling was the highest. (c) 2004 Elsevier B.V. All rights reserved.

Dissolved oxygen and O-2 flux across the water-air interface of the Changjiang Estuary in May 2003

The field observation of this study was carried out in the Changjiang Estuary from May 19 to 26,2003, just a few days before the Three Gorges Dam began to store water. A total of 29 stations, including 2 anchor stations, were distributed through almost the whole salinity gradient Based on the data gained from these stations, the biogeochemical characteristics of dissolved oxygen (DO) were examined. Spatial distribution of DO concentrations showed the pattern that it increased in a downriver direction. DO concentration generally varied within a narrow range of 733-8.10 mg l(-1) in the freshwater region and the west part of the mixed water region, and after that it increased rapidly. In vertical direction, the differences in DO concentrations between surface and 2 m above the bottom were big at the stations with water depths exceeding 20 m; DO concentration up to 14.88 mg l(-1) was recorded at the sea surface, while at 2 m above the bottom its concentration was only about 4 mg l(-1). The fluctuation in DO concentrations was small during a period of 48 h in the mixed water region and 2 m above the bottom of the seawater region; while it was large during the same period in the seawater region for surface and 5 m below the surface layer, and a maximum variation from 8.77 to 12.66 mg l(-1) in 4 h was recorded. Oxygen fluxes also showed a marked spatio-temporal variation. As a whole, the freshwater region and mixed water region were an oxygen sink while the seawater region was a source. Relationships between dissolved oxygen and some biogeochemical parameters which could markedly influence its spatio-temporal distribution were discussed in this paper. (C) 2008 Elsevier B.V. All rights reserved.

Impact of tidal front on the distribution of bacterioplankton in the southern Yellow Sea, China

Three surveys were carried out in anchovy spawning periods in southern Yellow Sea in May and June 2001, and June 2002. Chlorophyll a (Chl-a) concentration, bacterioplankton abundance, biomass and their variations along the zone of tidal fronts were investigated. The results showed that (1) high Synechococcus abundance distributed more often in frontal area and middle-surface layer of a stratified zone; and (2) the maximal abundance of bacteria occurred in stratified and mixed zone. 2006 Elsevier B.V. All rights reserved.

Autumn net copepod abundance and assemblages in relation to water masses on the continental shelf of the Yellow Sea and East China Sea

Copepod species diversity, abundance and assemblages in relation to water masses over the continental shelf of the Yellow Sea (YS) and East China Sea (ECS) were studied extensively based on the net plankton samples in autumn 2000. Multivariate analysis based on copepod assemblage resulted in recognition of five groups (Groups 1-5) corresponding to the water masses. Groups 1 and 2 delineated from inshore stations with low salinity YS Surface Water, and offshore stations with YS Cold Water in the YS. Group 3 located in the joint area of YS and ECS mainly with Mixed Water. Groups 4 and 5 in the ECS delineated two assemblages mainly from inshore and shallow stations with ECS Mixed Water in the southeastern ECS, and offshore stations along the ECS shelf edge controlled by saline Kuroshio Water. Salinity and temperature were more important in characterizing copepod assemblage of the continental shelf than chlorophyll a. (c) 2005 Elsevier B.V. All rights reserved.