Irrigation model of bleached Kraft mill wastewater through volcanic soil as a pollutants attenuation process

An irrigation process through volcanic soil columns was evaluated for bleached Kraft mill effluent pollutants retention. The system was designed to remove color and phenolic compounds and a simple kinetic model for determining the global mass transfer coefficient and the adsorption rate constant was used. The results clearly indicate that the global mass transfer coefficient values (K(c)a) and the adsorption rate constants are higher for the irrigation processes onto acidified soil. This means that the pretreatment of washing the volcanic soil with an acid solution has a positive effect on the adsorption rate for both pollutant groups. The enhanced adsorption capacity is partially explained by the activation of the metal oxides present in the soil matrix during the acid washing process. Increasing the flow rate from 1.5 to 2.5 ml/min yielded higher (K(c)a) values and adsorption rate constants for both pollutant groups. For instance, regarding color adsorption onto acidified soil, there is an increment of 43% in the (K(c)a) value for the experiment with a flow rate of 2.5 ml/min. Increasing the porosity of the column from 0.55 to 0.59, yielded a decrease in the (K(c)a) values for color and phenolic compounds adsorption processes. Onto natural soil for example, these decreases reached 21% and 24%, respectively. Therefore, the (K(c)a) value is dependent on both the liquid-phase velocity (external resistance) and the soil fraction in the column (internal resistance); making forced convection and diffusion to be the main transport mechanisms involved in the adsorption process. Analyzing the adsorption rate constants (K(c)a)/m, phenolic compounds and color adsorption rates onto acidified soil of 2.25 x 10(-6) and 2.62 x 10(-6) l/mg min were achieved for experiment 1. These adsorption rates are comparable with other adsorption systems and adsorbent materials.     

Levels and distribution of organochlorine pesticides, polychlorinated biphenyls and polybrominated diphenyl ethers in sediments and biota from the Danube Delta, Romania

Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs), such as dichlorodiphenyltrichloroethane (DDT) and analogues, hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB), were measured in sediments and biota (invertebrates, 11 fish species and cormorant tissues) collected in 2001 from the Danube Delta, the biggest European wetland. DDTs were the predominant pollutants in all samples. A high variability in the concentrations of pollutants within the same species was observed and this was related to sampling location, age, length and sex. DDTs were also the main organohalogenated contaminants in cormorant muscle and liver, followed by PCBs, HCHs, HCB and PBDEs. The present levels of DDTs in cormorant tissues are lower than levels measured in cormorant eggs sampled from the Danube Delta in 1982 and 1997, respectively. The variance of delta15N for herbivores was much greater than for carnivores, while carp and bream showed higher delta15N signatures than expected, probably due to a higher dietary proportion of benthos, typically more delta15N enriched relative to pelagic biota.     

PCDDs, PCDFs, and coplanar PCBs in wild terrestrial mammals from Japan: congener specific accumulation and hepatic sequestration

The present study determined the contamination levels and congener-specific accumulation features of dioxins and related compounds (DRCs) in wild terrestrial mammals such as large Japanese field mice (LJFM), lesser Japanese moles (LJMs), and raccoon dogs (RDs) collected from Kanto region in Japan during 2001. The toxic equivalent quantity (TEQ) levels in the carcasses or adipose tissues were in the order of RDs > or = LJMs > LJFM. Comparison of DRC congener profiles in the three species and principal component analysis (PCA) demonstrated a higher contribution of OCDD, T4CB77, and P5CB118 in LJMs. Analysis of liver-adipose distribution of DRC congeners in RDs showed that livers contained significantly higher TEQs than adipose tissues, indicating that liver is a depository organ and critical for determining the toxicokinetics of DRCs. As for most T4, P5, H6CDD/DFs and for P5CB126, H6CB169 and mono-ortho PCB congeners, their liver/adipose concentration ratios in RDs revealed a tendency to increase with hepatic TEQ levels, suggesting TEQ-dependent hepatic sequestration.     

Nitrogen balance and groundwater nitrate contamination: comparison among three intensive cropping systems on the North China Plain

The annual nitrogen (N) budget and groundwater nitrate-N concentrations were studied in the field in three major intensive cropping systems in Shandong province, north China. In the greenhouse vegetable systems the annual N inputs from fertilizers, manures and irrigation water were 1358, 1881 and 402 kg N ha(-1) on average, representing 2.5, 37.5 and 83.8 times the corresponding values in wheat (Triticum aestivum L.)-maize (Zea mays L.) rotations and 2.1, 10.4 and 68.2 times the values in apple (Malus pumila Mill.) orchards. The N surplus values were 349, 3327 and 746 kg N ha(-1), with residual soil nitrate-N after harvest amounting to 221-275, 1173 and 613 kg N ha(-1) in the top 90 cm of the soil profile and 213-242, 1032 and 976 kg N ha(-1) at 90-180 cm depth in wheat-maize, greenhouse vegetable and orchard systems, respectively. Nitrate leaching was evident in all three cropping systems and the groundwater in shallow wells (<15 m depth) was heavily contaminated in the greenhouse vegetable production area, where total N inputs were much higher than crop requirements and the excessive fertilizer N inputs were only about 40% of total N inputs.     

Joint analysis of process and operator performance in chemical process operational safety

Independent studies of case histories by the Health and Safety Commission in the UK and by a Honeywell led industrial consortium world-wide showed that human errors represent the major cause of failure in process plant operation. In contrast to this discovery the majority of previous studies on computer aided systems for fault detection and diagnosis has focused on the process side. This paper presents a methodology, which can involve human factors into the development of systems for automatic identification and diagnosis of abnormal operations and develops methods and techniques that can be used to simultaneously capture, characterise and assess the performance of operators as well as of the process. A joint process–operator simulation platform is developed which is used as a test-bed for carrying out the study. The process part is a simulator, which simulates in high fidelity the dynamic behaviour of the process that is subject to the influence of various disturbances and operators’ interventions. The operator module is developed as a real-time expert system, which emulates operator’s behaviour in interpretation of received signals, and planning and execution of decisions. The interaction between the two modules is managed through an interaction module, which handles the real-time exchange of data using Dynamic Data Exchange. The interaction module also contains the toolkits for analysing the dynamic behaviour of the joint process–operator system. The method and system are illustrated using a simulated case study.     

Study of the dynamics of estuarine and coastal waters using remote sensing: the Tinto-Odiel estuary, SW Spain

This paper deals with the application of satellite images to characterize some aspects of the circulation dynamics of the Tinto-Odiel estuary using turbidity patterns as ‘natural tracers’. 15 images (Landsat TM and Spot HRV) were processed to provide synoptic, instantaneous views of the circulation patterns under different environmental conditions. In addition, a comparison was made between results of oceanographic field work, using biplanes and fluorescent tracers, and satellite image turbidity patterns used as ‘ground truth’ data for specific hydroclimatic situations. This approach allowed (1) the identification and mapping of dynamic processes of interest during a theoretical tidal cycle, (2) the elaboration of additional information on the ‘flow schemes’ at the mouth of the estuary with improved spatial and temporal resolution, and (3) the supply of basic data to improve the knowledge of exchange processes between estuarine and coastal waters. The results of this study are considered to be useful for the management of the estuarine system.     

Feeding and respiration rates of a planktonic copepod (<Emphasis Type="Italic">Calanus sinicus</Emphasis>) oversummering in Yellow Sea Cold Bottom Waters

The distribution, feeding and oxygen consumption of Calanus sinicus were studied in August 2001 on a transect across Yellow Sea Cold Bottom Waters (YSCBW) and two additional transects nearby. The distribution of C. sinicus adults and copepodites stage CV appeared to be well correlated with water temperature. They tended to concentrate in the YSCBW (>10,000 ind. m^–2) to avoid high surface temperature. Gut pigment contents varied from 0.44 to 2.53 ng chlorophyll a equivalents (chl a equiv.) ind.^–1 for adults, and from 0.24 to 2.24 ng chl a equiv. ind.^–1 for CV copepodites. We found no relationship between gut pigment contents and the ambient chl a concentrations. Although the gut evacuation rate constants are consistent with those measured for other copepods, their low gut pigment contents meant an estimated daily herbivorous ingestion of <3% of body carbon in the YSCBW and <10% outside the YSCBW. However, based on estimates of clearance rates, C. sinicus feeds actively whether in the YSCBW or not, so the low ingestion rates probably reflect shortage of food. Oxygen consumption rates of C. sinicus ranged from 0.21 to 0.84 l O₂ ind.^–1 h^–1, with high rates often associated with high temperature. From the oxygen consumption rates, daily loss of body carbon was estimated to be 4.0–13.7%, which exceeds our estimates of their carbon ingestion rates. C. sinicus was probably not in diapause, either within or outside the YSCBW, but this cold-water layer provides C. sinicus with a refuge to live through the hot, low-food summer.Communicated by T. Ikeda, Hakodate