Leaching Rate of Polychlorinated Biphenyls (PCBs) from Marine Paint Chips

Polychlorinated biphenyls (PCBs) were added to certain marine vessel bottom paints as a plasticizer to improve the adhesion and durability of the paint. The most common PCB formulation used to amend such paints was Aroclor 1254. Fugitive Aroclor-containing paint chips generated from vessel maintenance and repair operations represent a potential source of PCB contamination to sediments. Limited published studies indicate that Aroclor-containing paint is largely inert and exhibits low PCB leaching into water; however, the rate and degree of leaching of PCBs from paint chips have not been directly studied. This laboratory-based study evaluated the rate and extent of leaching of PCBs from paint chips into freshwater. The results of this investigation demonstrate that the rate of PCB dissolution from paint chips decreased rapidly and exponentially over time. Based on this study, it is estimated that the rate of leaching of PCBs from paint chips would cease after approximately 3 years of exposure to water. When all leachable PCBs were exhausted, it is estimated that less than 1% of the mass of PCBs in the paint chips was amenable to dissolution. The results of this experiment suggest that Aroclor-containing paint chips found in sediments are likely short-term sources of dissolved-phase PCB to pore or surface waters and that the majority of the PCBs in paint chips remain in the paint matrix and unavailable for partitioning into water. Graphic Abstract

Reducing bubble generation and sweepdown effect on a research vessel with a moonpool

Some research vessels set moonpools for sonars installation. The moonpool provides a relatively good working environment for sonar in a harsh marine environment. At the same time, other acoustic detection equipment are installed along the ship bottom behind the moonpool. Due to the exist of the sonar with a variable cross-section, the number of bubbles generated in the moonpool increases. The bubbles generated in the moonpool expel and flow along the vessel bottom to the stern, which leads to the sweepdown effect. The performance of the sonar and other acoustic detection equipment degrades by the bubbles around. However, the research on reducing bubble generation in the moonpool and sweepdown effects is rare. So in present paper the reduction effects of damping devices such as the flange and choke deck on the bubble generation in the moonpool are investigated experimentally. Then, in order to reduce the sweepdown effects of bubbles on the ship bottom, three other damping devices which are double flaps, diversion channel and wedge are investigated. It can be seen that through reducing the area of bubble leakage in the moonpool the distribution position of bubbles can be effectively restricted and the width and thickness of the bubbles reduce.

Comparative Analysis of Severe Accident at WWER-1000 NPP with MELCOR 1.8.5 and 2.1 Code Versions

An overview of the main improvements in updated version 2.1 of MELCOR computer code related to more representative mathematical modeling of complex thermohydraulic severe accident processes of core degradation, transfer of molten fragments to the bottom of the reactor, heating and failure of the bottom of the reactor pressure vessel is presented. The elements of WWER-1000 NPP computer model for the MELCOR 1.8.5 (control volumes, thermal structures and structures of the reactor core) that are reproduced for a reactor with the primary side, the secondary side and the containment are described. The changes implemented in WWER-1000 NPP model for MELCOR 1.8.5 to convert it to MELCOR 2.1 version that are mainly related to more detailed modeling of the reactor core and reactor pressure vessel bottom are provided. The paper presents the results of comparative analysis of severe accident scenario of total station blackout at WWER-1000 NPP with MELCOR 1.8.5 and 2.1. The comparison demonstrates good agreement between the main parameters’ results (pressure and temperature in hydraulic elements of the primary, secondary sides and the containment, temperature of core elements, the mass of the generated non-condensed gases and their concentration in the containment) obtained with these code versions for severe accident in-vessel phase. The identified differences in the time of core structures degradation and reactor vessel bottom failure are insignificantly affected by the behavior of the parameters in the primary side and the containment in the in-vessel phase of the severe accident and are related to more detailed modelling of the reactor core and bottom part of the reactor in MELCOR 2.1.

Ceramic Complex of the Neolithic Camp Ekidin 24

The camp Ekidin 24 is located in the southern part of the Turgai Depression (Northern Kazakhstan, Kostanay region). The monument was explored by the Turgai archeological expedition in the 1989 field season. The present research featured the ceramic complex of camp Ekidin 24. The research objective was to study technological aspects in the manufacture of ceramic vessels of the Ekidin potters. An important aspect of the work is the generalization of all currently known camp data. The ceramic collection of the Ekidin 24 camp consists of 48 fragments, including 6 fragments of the upper parts of vessels with a grooved neck, one fragment of a vessel bottom, and 38 fragments of vessel walls. All fragments of ceramics from the Ekidin 24 camp were subjected to a technical and technological analysis. The study employed petrographic analysis and binocular microscopy. The initial raw material of the Ekidin potters was iron clay (iron hydroxides, such as hematite and magnetite), or hydromica. A formula of molding mass was revealed: clay + organic (wool) + chamotte. The Ekidin 24 camp is the reference monument of the Mahanjar culture of the Turgai Depression. The age of Mahanjar finds is determined primarily on the analogies with early Neolithic monuments of the Central Asian interfluves as late 7,000 – 5,000 B.C. The obtained radiocarbon dates indicate 6,000 B.C. Mahanjar-like Ceramics are still represented by single fragments outside the Turgai Depression and, as a rule, are not recognized by researchers as Mahanjar. We can confidently say that the Mahanjar culture is not an isolated phenomenon, and the identification of new Mahanjar sites in different regions of the steppe and forest-steppe Eurasia is only a matter of time.

Suppositional measures for harmful microalga Pseudo-nitzschia calliantha control in aquaculture farms

Growth of potentially toxic diatom microalga Pseudo-nitzschia calliantha is investigated in laboratory culture under different conditions of cultivation. In the conditions without stirring, the highest abundance of algae was moderate (16131 cells/ml) and observed after 3 days of exposition; many chains of 5-8 cells were formed. Further exposition showed cyclic dynamics of the culture, the chains of 5-12 cells were numerous, chloroplasts looked healthy, their color was olive-green. After stirring, a short lag-phase preceded to the phase of active cells dividing with exponential growth of their number to the peaks of 59828-70566 cells/ml, chains of 2-8 cells were formed but rapidly settled to the vessel bottom, chloroplasts were discrete and bleached that indicated dying of the culture. P. calliantha is potentially toxic species, so the sites with active water circulation or constrained water mixing are recommended for aquaculture farming that protects the environments from its phycotoxins accumulation.

The Influence of a Rotating Magnetic Field on the Sample with Magnetizable Materials near the Vessel Bottom

The rotation and translational motion of the samples with a magnetizable material alonga bottom of a vessel in a uniform applied rotating magnetic field are examined experimentally. Weconsider a magnetic fluid (MF) drop and a body with a magnetizable polymer (MP). The phenomenaof the change of the direction of the translation motion at some field frequency is observed only forthe MF drop.