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Corrosion of steel in reinforced and prestressed concrete members exposed to a marine tidal zone is a serious durability problem. This study presents a methodology for rationally estimating the safe cover thickness for steel in concrete structures exposed to the tidal zone. The proposed methodology was implemented for the case of six Indian coastal stations using 100-year-long simulations of chloride transport in concrete. Real-time meteorological and tidal height data were used for simulating the model boundary conditions. Using simulated results of chloride threshold depths (CTDs), safe cover thickness to steel was assessed. Estimated safe cover thicknesses to steel across coastal stations differed significantly (25–30 mm), indicating a need for corrosion vulnerability zonation of coastlines. Conventionally used tide models were improved by superimposing with an annual component of astronomical tides, which expanded the range of wet-dry regimes simulated by the tide models. The study also compared the chloride ingress predictions from the modified tide models with those from real tides. The superimposed tide model was found to be a better approximation of real tides than the diurnal tide model. The modified tide models very well simulated chloride ingress around the critical sections in the tidal zone. [ABSTRACT FROM AUTHOR]

A self‐healing anticorrosion protective was developed for steel st‐37 exposed to the marine tidal zone, which is composed of a multi‐layer polymer coating. The coating includes zinc‐rich epoxy primer, self‐healing microencapsulated embedded epoxy, and a top coat consisting of polyurethane incorporated with silica nanoparticles. The size of microcapsules decreased with increasing agitation during encapsulation, which varies from 4 to 43 µm. Good performance was observed for producing the encapsulated particles with a size of up to 5 µm and more than 90% loading of the embedded healing agent, in which a 1680 rpm agitation along with a pH of 3 for the synthesis environment and a 130 min for the synthesis duration is set. The optimal amount of microcapsules and silica nanoparticles was 10 and 1.5 wt%, respectively. Also, the promised self‐healing anticorrosion coating leads the damaged areas to be fully healed in almost 12 h in the face of harsh conditions. In contrast to the non‐self‐healing one, the healing ability of the developed self‐healing coating shows good barrier properties and leads to a lesser loss of interface adhesion. [ABSTRACT FROM AUTHOR]

Single-use plastic litter is the main component of marine litter worldwide. In the present study, the impact of discarded single-use garbage bags is experimentally evaluated on density, diversity, community structure and vertical distribution of the upper intertidal free living nematode community. Our results showed that the presence of garbage bags on intertidal sediment sharply decreased total and vertical nematode densities and diversity indices as well as decreased sediment oxygen redox potential, and altered total and vertical nematode communities. However, covering sediment with garbage bags did not result in complete nematode mortality. At the end of the experiment, epigrowth feeders and facultative predator nematodes disappeared and the community was dominated by deposit feeder genera. Considering that single-use plastic litter is in intertidal ecosystems, any change in the density and biomass of benthic fauna could lead to a decrease in benthic secondary production and food shortage for their predators. [ABSTRACT FROM AUTHOR]

Corrosion behaviour of carbon steel (CS) exposed in the tidal zone of Beibu Gulf was investigated by experimental method. Q235 CS specimens were designed and exposed for 12 months. The corrosion mechanism of CS was characterised by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-Ray diffraction (XRD). Results show that the corrosion performance of CS can be verified by the formula D = atn. The corrosion products are mainly composed of α-FeOOH, γ-FeOOH, β-FeOOH, Fe3O4 and γ-Fe2O3. Significantly, Cl– is an intermediate in the corrosion process and promotes the formation of the characteristic product β-FeOOH. [ABSTRACT FROM AUTHOR]

The splash and spray and tidal zones are generally assumed to be the most severe marine exposure environments with respect to steel reinforcement corrosion in concrete structures. However, it has been observed in several aged marine structures along the Southern African coastlines, that there is usually relatively insignificant reinforcement corrosion damage in the tidal zone, despite very high (above-threshold) chloride contents. To develop a full understanding of the severity of marine exposure conditions with regard to the actual deterioration, it is imperative that other factors that directly affect corrosion, such as oxygen availability at the steel surface (which is influenced by concrete quality, cover thickness and moisture condition), are carefully considered. The laboratory experimental work in the study presented in this paper comprised of different cover depths (10, 20 and 30 mm) and w/b ratios (0.5 and 0.8) and simulated marine tidal, splash and submerged environments. The results show that for any give exposure environment, the relative influence of each of the various factors considered should be considered in conjunction with the other factors; this finding can be generalized to include all relevant factors that can affect corrosion in a given exposure environment including ambient temperature. For example, a cover depth of 30 mm in the tidal zone with a simulated intertidal duration of 6 h effectively resulted in similar corrosion behavior to that in the submerged zone. The paper concludes that engineers should consider these factors when applying standard exposure classes in the design for durability of marine structures.

We have studied soils and the plant cover of tombolos, which are isthmuses between the mainland and small islands on the coasts of the White and Baltic seas. Tombolos are characterized by complicated dynamics of sedimentation, which results in a strong heterogeneity of soils and associated plant cover. Typical gley and surface-gley marsh soils are formed on the Kolezhma plot on the White Sea coast. The vegetation corresponds to marsh meadows of the lower and middle levels and depends on salinity, acidity, and soil texture. Soils on the Gakkovo plot on the Baltic Sea coast are characterized by greater uniformity and, in general, a sandy texture. As compared to the White Sea, the effect of the Baltic Sea on the soil and plant cover is significantly smaller due to its slighter tidal dynamics. [ABSTRACT FROM AUTHOR]

In this paper, the chloride diffusion behaviour of coral aggregate concrete (CAC) exposed to marine submerged, tidal, and salt spray zones was investigated, and the effect of the fly ash (FA) content on the chloride diffusion was explored. The chloride concentration was measured using the potentiometric method, and the Ca(OH)₂ content in the CAC was calculated using the thermogravimetric method. The results show that the chloride concentration in the submerged zone decreases with an increasing erosion depth; meanwhile, in the tidal and salt spray zones, the chloride concentration showed a two-stage distribution pattern. The depth of the convective zone gradually increases with an increasing erosion time, and the depth of the convective zone in the salt spray zone is larger than that in the tidal zone. The chloride diffusion coefficient exhibits a power-function attenuation relationship with erosion time when exposed to different corrosion zones. The attenuation coefficient of the chloride diffusion coefficient increases with an increasing FA content. Moreover, the attenuation coefficient is the highest in the salt spray zone with it being 10.8% to 28.5% higher than that of the tidal zone. In addition, the Ca(OH)₂ content in the tidal zone is not only the lowest, but also gradually decreases with an increasing erosion time.

Mangrove forests are large pools of soil organic carbon (SOC) found across the world, and play a vital role in global carbon (C) cycling. In this study, to investigate the effects of spatial factors on SOC in mangrove forests, soil samples at different depth layers from upper estuary (UE), lower estuary (LE), and tidal inlet (TI) in the Qinglangang mangrove forest in Southern China were collected and the differences in SOC among the layers and geomorphological settings were compared. The mean SOC content showed a pattern of LE (4.63 ± 1.28%) > UE (2.94 ± 0.73%) > TI (1.44 ± 0.33%). SOC content and storage decreased with soil depth in TI, but increased in UE. The total SOC storages (0–80 cm) of sites TU, UE, and LE, were 104.41 ± 16.63, 207.14 ± 44.83, and 228.78 ± 19.37 Mg/ha, respectively. The results suggested that top- and subsoil organic C content and storage were largely dependent on their specific location, which underwent different river-sea interactions and human activities. The SOC of the soil profile varied at different sites, implying that the current C storage of mangrove ecosystems can be accurately estimated by quantifying the C of sediments at sites. [ABSTRACT FROM AUTHOR]

The splash and spray and tidal zones are generally assumed to be the most severe marine exposure environments with respect to steel reinforcement corrosion in concrete structures. However, it has been observed in several aged marine structures along the Southern African coastlines, that there is usually relatively insignificant reinforcement corrosion damage in the tidal zone, despite very high (above-threshold) chloride contents. To develop a full understanding of the severity of marine exposure conditions with regard to the actual deterioration, it is imperative that other factors that directly affect corrosion, such as oxygen availability at the steel surface (which is influenced by concrete quality, cover thickness and moisture condition), are carefully considered. The laboratory experimental work in the study presented in this paper comprised of different cover depths (10, 20 and 30 mm) and w/b ratios (0.5 and 0.8) and simulated marine tidal, splash and submerged environments. The results show that for any give exposure environment, the relative influence of each of the various factors considered should be considered in conjunction with the other factors; this finding can be generalized to include all relevant factors that can affect corrosion in a given exposure environment including ambient temperature. For example, a cover depth of 30 mm in the tidal zone with a simulated intertidal duration of 6 h effectively resulted in similar corrosion behavior to that in the submerged zone. The paper concludes that engineers should consider these factors when applying standard exposure classes in the design for durability of marine structures. [ABSTRACT FROM AUTHOR]

The current study was conducted on N. indica in three stations for the period from December 2017 to November 2018 (Al-Sharsh, Al-Salhiya and Al-Dweab), as samples were collected monthly. Some environmental factors were calculated, such as water temperature. The lowest water temperature was 12 °C during January and the highest temperature was 33 °C during July, both in Al-Salhiya station. The lowest value of salinity was 0.5‰ reached in April and November in Al-Sharsh station, while reached highest value ‰ 39.3 were recorded during July for Al-Dweab station, the light transmittance values ranged between (63-18) cm, recorded during July and November for Al-Salhiya and Al-Sharsh stations, respectively. As for the values of dissolved oxygen, it ranged between (12.1-5.1) mg/liter during August and May in the two stations. Al- Salhiya and Al-Sharsh, respectively. As for the bottom sediments of all the stations, they were alluvial with few and different percentages of sand and clay. The study showed that the studied environmental factors have an impact on the distribution and spread of this species within the horizontal and vertical sections in the tidal zone. The total density and density were measured within the horizontal distribution pattern in each station and the monthly total density ranges were 592-32 individuals/m2. The density of the three species was calculated within the horizontal distribution after dividing the area into three sections for each station. The results of the study indicated that there were significant differences at the level of P

Bioturbation of infauna plays an important role in the biogeochemical processing of sediments. Infaunal animals build burrows and enlarge the sediment-water interface by their activities and so bioturbation is closely related with burrow structure and animal behavior in the sediment. The purpose of this study is to explore the characteristics of Perinereis aibuhitensis burrow structures with the factors of months and animal sizes (0-1g, 1-2g, 2-3g, 3-4g, and >4g), which would also provide useful knowledge of infauna behavioral ecology. The dimension and complexity of the burrows of P. aibuhitensis were measured by dissecting sediments. The results showed that there were three burrow shapes of P. aibuhitensis, i.e., I, Y and U shapes. Overall, the order of abundance of each of the three burrow shapes were I > Y > U. Larger P. aibuhitensis are inclined to build Y- and U-shaped burrows in June and August. There were significant differences in the tunnel diameter, burrow depth and burrow length separately between different polychaete size classes (P< 0.001). In February and August, the burrow depths and burrow lengths of P. aibuhitensis individuals with body weights of 1-2 g and 2-3 g were significantly greater than in other months (P< 0.001). P. aibuhitensis individuals of 1-2 g and 3-4 g body weight had significantly more burrow openings and branches in August than in February (P< 0.001). Within the same month, the burrow HEindex increased with increasing polychaete size, and when the sizes were 1-2 g, 2-3 g and 3-4 g, the complexity in August was higher than that in other months. This study suggests that I-shaped burrow dominants the burrow architecture of P. aibuhitensis. The polychaete with large size has a higher HEindex (burrow complexity) indicating a strong bioturbation ability. Y-shaped burrows are more conducive to the survival of P. aibuhitensis in hot weather. In order to adapt to environmental stresses outside, P. aibuhitensis usually builds deeper burrows.

In general, building materials exposed to the marine environment are more prone to deteriorates than others. There are three main zones of the marine environment named atmospheric zone, tidal zone and submerged zone. This article investigated the effect of different curing conditions named water curing, air curing, seawater curing and wet/dry curing on the compressive strength and microstructure properties of alkali-activated slag (AAS) pastes with and without microsize metakaolin (mK) particles over a period of up to one year. The wet/dry curing was used to simulate the effect of the tidal zone, of which the specimens were submerged in seawater for 18 h followed by 6 h of air drying per day. The slag was partially replaced with mK at ratios fluctuated from 0 to 12% with a step of 2%, by weight. A fixed concentration of sodium silicate was used as an alkaline activator. After initial curing, the specimens were exposed to the aforementioned treatment conditions for 3, 6 and 12 M. The phase composition and microscopic structure of the neat AAS and AAS/mK samples were tested by X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTG) and scanning electron microscopy (SEM). The results showed that the deterioration in the specimens exposed to the simulated tidal zone is more severe than those submerged in seawater. The neat AAS pastes showed better strength and microstructure than those blended with mK. [ABSTRACT FROM AUTHOR]

The marine environment has a significant deterioration effect on building materials. Among the different zones of the marine environment, the tidal zone has the highest deterioration. The current paper is the first attempt to study the effect of different treatment conditions--water curing, air curing, seawater curing, and simulated tidal zone--on the compressive strength and microstructure properties of alkali-activated slag (AAS) pastes without or with different mineral admixtures over different periods. Slag was partially replaced with 5 and 10% of different mineral admixtures--fly ash (FA), silica fume (SF), and quartz powder (Q)--by weight. After initial curing, the specimens were subjected to altered treatment conditions for 3, 6, and 12 months (M). The crystalline phases, microstructure analysis, and energy-dispersive X-ray spectra (EDS) of the selected samples were analyzed. The results indicated that the tidal zone has the highest aggressive deterioration on the specimens, followed by those exposed to seawater attack (submerged in seawater). The specimens cured in water exhibited the highest compressive strength, followed by those cured in air. The specimens containing Q showed the best performance, followed by those containing SF and FA, respectively, while the plain AAS pastes came in last place. [ABSTRACT FROM AUTHOR]

Burrowing Ocypodoidea crabs are an abundant component of many tropical and temperate coastal areas and central to the ecosystem functioning, for instance because they recycle nutrients, are important food for many shorebirds and alter the sediment through their burrowing behaviour. The burrow morphology of these crabs may differ between and within species, often correlated with differences in habitat preferences, crab morphology and life-history traits. Here we studied the burrow morphology and complexity of Macrophthalmus sulcatus and Macrophthalmus depressus, by means of casts (n = 7 and 10, respectively) and burrow excavations (n = 17 and 16, respectively) at the pristine intertidal mudflats of Barr Al Hikman in the Sultanate of Oman. We found that M. sulcatus construct simple burrows that were in all but one case inhabited by a single crab. By contrast, all burrows of M. depressus were complex, with multiple entrances and many (deep-reaching) branches. There was a strong relationship between M. sulcatus carapace width and burrow entrance size, indicating that the simple burrows are adapted to and made by the occupant. There was no relation between M. depressus carapace width and burrow entrance size, and in six burrows more than one crab was encountered, suggesting that the complex burrows are not made by and adapted to a single occupant. The complex burrows were found close to the shore whereas the simple burrows were found at the intermediate tidal zone. We speculate that the striking differences in burrow morphology may be explained by difference in habitat selection of the studied crabs, which most importantly relates to differences in sediment structure and tidal height. Crab morphology and life-history traits of the studied crabs could also account for the observed difference in burrow morphology. [ABSTRACT FROM AUTHOR]

Detailed information on lake bathymetry is essential for both hydrology-related studies and water resource management. Conventionally, lake bathymetry was mapped using high-cost approaches (e.g., ship/boat-based multibeam echosounders or airborne bathymetric lidars). With only satellite remotely sensed data sets, a method for deriving high-resolution bathymetry for dynamic areas was proposed by combining the new Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) lidar data and the Landsat-based Global Surface Water Data Set (GSWD). First, ICESat-2 can provide accurate along-track topographic points after the point cloud processing and bathymetric error correction, and the GSWD can supply water occurrence information within the lake dynamic area between 1984 and 2018. Second, using the derived relationship between the elevation and water occurrence, the bathymetric map of Lake Mead, USA, was produced with the dynamic area exceeding 235 km2, elevation ranging nearly 37 m, and a resolution of 30 m. The local reference data (i.e., the airborne topographic lidar data and ship/boat-based bathymetric data) in six areas around Lake Mead were used for the validations. In general, the produced lake bathymetry achieved an accuracy of approximately 2 m in elevation with R2 of 0.97. The proposed method is promising to obtain global bathymetry for inland water bodies (e.g., the lake and reservoir) and coastal areas (e.g., the tidal zone) where water level fluctuations are strong and the water clarity is sufficient. [ABSTRACT FROM AUTHOR]

The widespread presence of microplastics (MPs) in the ocean has varying degrees of impact on ecosystems and even human health. Coastal tidal zones are crucial in controlling the movement of MPs, which are influenced by waves and tidal forces. Meanwhile, natural nanobubbles (NBs) in the ocean can affect the hydrodynamic properties of the tidal zone. The mobilization of MPs in coastal tidal zones under the effect of NBs has been less studied. In this study, we explored natural NBs' influence on the mobilization of MPs in shorelines subject to seawater infiltration. Using glass beads as a substrate, a coastal porous environment was constructed through column experiments, and the pump-controlled water flow was used to study the transport of MPs subject to seawater movement within the substrate. The infiltration of MPs under continuous and transient conditions, as well as the upward transport induced by flood tide, were considered. The role of salinity in the interactions between NBs, MPs, and substrates was evaluated. Salinity altered the energy barriers between particles, which in turn affected the movement of MPs within the substrate. In addition, hydrophilic MPs were more likely to infiltrate within the substrate and had different movement patterns under continuous and transient flow conditions. The motion of the MPs within the substrate varied with flow rate, and NBs limited the vertical movement of MPs in the tidal zone. It was also observed that NBs adsorbed readily onto substrates, altering the surface properties of substrates, particularly their ability to attach and detach from other substances. [Display omitted] • The motion of the microplastics within the substrate varied with the flow pattern. • Nanobubbles limited the infiltration of microplastics in the tidal zone. • Salinity changed the interaction energy between particles and promoted aggregation. • Hydrophilicity affected the mobilization of microplastics in the substrate. • Nanobubbles attached to the substrates, thus changing their surface properties. [ABSTRACT FROM AUTHOR]

One of several methods used to minimize reinforcement corrosion is the use of service-life prediction models to calculate mixture design and construction variables for the desired service life of a structure. Although several models are available for this purpose, very few incorporate the effect of environmental temperature on chloride diffusion. Moreover, most of the earlier studies were conducted under laboratory conditions and they are not based on actual field data. In the reported study, chloride diffusion in Type V and silica fume cement concretes was evaluated under laboratory and field conditions. Large-size concrete specimens were exposed in the tidal zone of a marine exposure site for 1, 2, 5, and 10 years while the laboratory specimens were exposed to a chloride solution maintained at 22, 35, 50, and 60°C (71.6, 95, 122, and 140°F) for 1 year. The coefficient of chloride diffusion (Da) for Type V cement concrete specimens placed in the field was noted to be much more than that of silica fume cement concrete specimens at all exposure periods. However, the Da for both Type V and silica fume cement concrete specimens decreased by 1.3 to 3 times with increasing period of exposure. The Da for the laboratory concrete specimens increased by 2.2 to 3.8 times as the exposure temperature was increased from 22 to 60°C (71.6 to 140°F). Furthermore, the Da for Type V cement concrete specimens was 2.9 to 5 times more than that of silica fume cement concrete specimens. Empirical models correlating the field and laboratory data were developed. These models could be useful for calculating the Da for field conditions from the laboratory data. [ABSTRACT FROM AUTHOR]

The photosynthetic performance of a Vaucheria sp. community in the Adventfjorden tidal flats near Longyearbyen, Svalbard, the Arctic was evaluated in a series of in situ and ex situ measurements based on variable chlorophyll fluorescence and gasometric approaches. The in situ measurement did not indicate any possible drivers from the selected environmental parameters (temperature, PAR, UVR, emersion period duration) of photosynthetic activity. Two ecotypes, spikes or loose filaments, observed in the field were related to emersion and immersion periods during the tidal cycle. Ex situ long-term monitoring identified PAR as the main controlling factor of photosynthesis. No limitation of photosynthetic activity due to temperatures or light was detected. The detailed ex situ photosynthesis measurements of Vaucheria sp. samples pre-acclimated to different irradiances did not reveal any decrease of photosynthesis in high light. Irradiance affected only the photosynthesis rate, but not the photosynthesis efficiency. The Vaucheria sp. was acclimated to the prevailing low-light conditions but was able to tolerate high-light conditions on sunny days of the late Artic summer. [ABSTRACT FROM AUTHOR]

Intertidal macroalgae suffer different environmental conditions and mat densities during growing period. In the present study, Ulva lactuca Linnaeus were collected from high, intermediate, and low tidal zones at Nan'ao Island, China. These algal photosynthetic pigments and photosynthesis behaviors with different mat densities were measured. The aim is to examine how the physiological responses and acclimation match the representative tidal distribution and algal mat density. The photosynthetic pigment (chlorophyll a and carotenoid) contents and irradiance-saturated maximum photosynthetic rates (Pmax) were greater in low zone–grown U. lactuca compared with the algae grown at high and intermediate zones. Under low algal mat density, the Pmax, apparent photosynthetic efficiency (α), and dark respiration rate (Rd) of U. lactuca grown at low zone were increased, whereas the irradiance saturation points (Ik) were decreased, compared with the algae grown at higher zone. However, the Pmax of high and intermediate zone–grown U. lactuca at high algal mat density were greater than at low density. Moreover, the pH compensation point of low zone–grown thalli (9.98) was lower than the higher zone–grown thalli (more than 10.15); however, the chlorophyll fluorescence parameters (reflect photosynthetic system activity) of the thalli collected from the three different zones were similar. Therefore, we proposed that the effects of varied densities on the photosynthetic rates of these three tidal zone–grown U. lactuca thalli were different, which might be related with different capacity of HCO3− utilization of macroalgae at their zonations. [ABSTRACT FROM AUTHOR]

The round goby, Neogobius melanostomus, is a Ponto-Caspian fish species currently found in many parts of Europe, including the North Sea riverine deltas. The objective of this study was to examine the parasite community of fish caught in the lower Elbe (Süderelbe – tidal zone; Geesthacht – non-tidal) in Germany and compare it with published data from the upper Elbe (Ústí nad Labem) in the Czech Republic. Twelve parasite taxa were recorded in the lower Elbe, six in the Süderelbe and nine near the city of Geesthacht. Süderelbe fish were mainly infected with Angullicola crassus larvae, while gobies from Geesthacht – with glochidia and sporadically occurring Pomporhynchus laevis, and the opposite situation was observed at Ústí nad Labem. It appears that a large tidal weir at Geesthacht significantly contributes to the division of the round goby population, with the Geesthacht parasite community being more similar to that at Ústí nad Labem than the one from the Süderelbe, thus increasing the likelihood that shipping from Hamburg was the introduction vector to Ústí nad Labem. We also recorded Acanthocephalus rhinensis in the Elbe for the first time, and in a new host – the round goby. Thus, round gobies may represent a new vector for the introduction of this parasite along the Elbe. [ABSTRACT FROM AUTHOR]

The model for chloride transport in concrete was established by considering both effects of diffusion and capillary suction. The model was verified by chloride penetration tests under cyclic wetting and drying conditions. The developed model was used to analyze similarities under different environmental conditions for accelerated tests. The results showed that the influence of external chloride concentration on chloride penetration was smaller with a larger depth. When the ambient relative humidity (RH) decreased, the penetration rate increased when RH was larger than 70%. However, the penetration rate decreased when the RH was smaller than 70%. The results also indicated that when the wetting-to-drying time ratio in a cycle increased, the penetration rate increased first and then decreased after a critical ratio. When the cycle period decreased, the penetration rate first increased and then decreased during a small time period. [ABSTRACT FROM AUTHOR]

In the present study, population ecology and relationships between various morphometric characters of the sand-bubbler crab Scopimera crabricauda from the Persian Gulf (Iran) were studied. Crabs were collected monthly by excavating nine quadrats in high-density areas of open burrows at low, mid and high intertidal levels during spring low tides for one year. A total of 534 crabs was collected, of which 70% were males (and 30% females). Mean carapace width and total weight in both sexes showed significant differences. Crabs with a carapace width ranging from 5 to 7 mm were the dominant crabs in the population. The highest numbers of crabs were found in the higher intertidal area. The mean size of crabs decreased towards the sea. The aggregation of small crabs was found towards sea in female crabs. Juveniles were abundantly found from January to March whereas the sub-adults and adults were mostly found from April to January. The carapace length to carapace width relationship differed between males and females, as did the carapace width and carapace length to total weight relationships. Finally, the relationship between carapace width and weight for both sexes showed that the growth of this species is allometric. [ABSTRACT FROM AUTHOR]

Intertidal archaeological deposits occur worldwide, particularly in the temperate latitudes. These deposits can contain archaeological sites that were constructed at the time these were terrestrial landscapes, but subsequently were inundated as a result of rising sea levels. Part of this process can include the development of salt marshes. There is a need, therefore, to identify where archaeological sites lie within the cline of past tidal regimes. This paper presents the results of a survey of UK archaeoentomological data recovered from intertidal deposits which was undertaken in order to identify patterns in archaeoentomological data that might indicate a deposit's position within a saltmarsh. Such an approach has potential to establish ‘indicator groups’ for saltmarsh zones, thereby facilitating archaeological interpretation of intertidal deposits. A statistical ordination of the archaeoentomological dataset has been undertaken to explore the security and strength of proposed archaeoentomological indicator groups for various ecological zones within saltmarsh/intertidal environments and the results are presented here. These indicator groups also are crossed-checked against the known modern ecology of the various beetles included within each grouping, to determine if they make good ‘ecological sense’. The dataset discussed here is specific to Northern Europe, but the approach is applicable worldwide. [ABSTRACT FROM AUTHOR]

[Display omitted] • The coupling effects of Cl− and Mg2+ in marine tidal zone were assessed. • High concentrations (≥0.2 mol/L) Mg2+ is detrimental to the chemically bound chloride ions. • Cementitious materials mixed with GGBS can chemically bound more chloride than those mixed with FA. • Cementitious materials mixed with GGBS can reduce the total pore volume than those mixed with FA. To reveal the deterioration mechanism of cementitious materials serving in the marine tidal environment, this study investigates the microstructures of cementitious materials under the coupling effects of Cl− and Mg2+. This study mainly analyzes the phase composition, pore structure distribution, and micromorphology of the hardened cementitious materials with 30 % fly ash (FA), 30 % ground granulated blast furnace slag (GGBS), or a combination of 15 % FA and 15 % GGBS under different Mg2+ concentrations. The effects of Mg2+ concentration and mineral admixture type on chemically bound chloride ions and their microstructures are investigated. The results show that a large amount of Friedel's salt is formed under the coupling effects of 0.6 mol/l Cl− and 0.1 mol/l Mg2+. A corrosive solution with a high concentration of Mg2+ is not conducive to the forming of Friedel's salt. In a Cl− or Cl−-Mg2+ environment, GGBS can chemically bind more chloride ions than FA. With the increase of Mg2+ concentration, more pores and cracks appear on the sample surface. In a Cl−-Mg2+ corrosive solution, cementitious materials with mineral admixtures are more porous than pure cementitious materials. Cementitious materials hardened with GGBS are more porous than those materials hardened with FA. Thus, GGBS is more conducive to improving the materials' resistance to chloride ions than FA. [ABSTRACT FROM AUTHOR]

Iron cycles is essential for the transition of matter and energy in wetland ecosystems. The tidal hydrology is a critical factor controlling soil iron biogeochemistry in estuarine wetland, but it remains unclear how iron oxides response to tidal hydrologic regime. A field experiment was manipulated in the Yellow River Estuary wetland for 23 months to differentiate change in iron oxides of freshwater marsh soil under different tidal hydrologic regimes. In June 2019, soil cores were collected in the freshwater marsh on the supratidal zone (FPA), and translocated to be cultured in the tidal salt marshes on the intertidal zone (SPA, TC and SS). Over 23 months, tidal hydrologic regime had obviously affected soil properties and iron oxides. Under the tidal regime, there was an increase in soil pH and electric conductivity (EC), and a decrease in soil water content (SWC), total nitrogen (TN), total phosphorus (TP) and total organic carbon (TOC). A total decrease was found in the contents of soil iron (Fe T), iron oxides (Fe p , complexed iron; Fe o , amorphous iron; Fe d , free iron) and their ratios (Fe p /Fe d , Fe o /Fe d and Fe d /Fe T). The duration of tidal hydrology affected the contents of iron oxides and their ratios, i.e., Fe T and Fe d decreased with culture time in all sites while Fe p , Fe o and the ratios increased in the supratidal site. Iron oxides and their ratios were positively correlated to redox potential, organic carbon and nutrients, and negatively correlated to soil pH and salinity. The results indicate that tidal hydrologic regime could decrease the contents of soil iron oxides and their activation when freshwater marsh exposed to tide events. [Display omitted] • A field experiment along a hydrologic gradient was manipulated. • Tidal hydrology had effects on soil properties and contents of iron oxides. • Tidal action decreased the contents of iron oxides and their activation. • Changes in iron oxides under tidal regimes were related to soil properties. [ABSTRACT FROM AUTHOR]

• The MIC of EH40 steel in the simulated tidal zone is investigated. • The corrosion efficiency of P. aeruginosa is enhanced in the simulated tidal zone. • Alternate immersion affects bacterial activity, which affects the corrosion. • More phenazines are secreted by P. aeruginosa under the alternate immersion. • EET-MIC is promoted under the alternate immersion of simulated tidal zone. Corrosion of metals in the tidal zone shortens the service life of facilities considerably and causes extensive economic losses each year. However, the contribution of microbiologically influenced corrosion (MIC) to this progress is usually ignored, and consequently the research on the mechanism of MIC in the tidal zone is highly desirable. In this study, the impact of the typical marine strain Pseudomonas aeruginosa on EH40 steel corrosion in the simulated tidal zone was evaluated. P. aeruginosa accelerated the corrosion of EH40 steel in the simulated tidal zone and its corrosion promotion efficiency rose over time. The environmental stress promoted the metabolism, energy production, and secretion of phenazines of P. aeruginosa , which promoted extracellular electron transfer between bacteria and steel, and accelerated MIC. The study proposes a possible mechanism of MIC in the tidal zone at the molecular biological level, which is of theoretical significance for evaluating the corrosion risks of marine equipment. [Display omitted] [ABSTRACT FROM AUTHOR]

There are three fundamental physical types for repairs by surface treatment on concrete, i.e., coating, penetrant, and sealer. Due to the inconsistency in using the penetrant-based model in a previous study, three limitations occur. To avoid the limitations, this paper proposes a simple pseudo-coating model embedded in a Fick-based time-dependent approach for modeling the performance of surface-coated concrete in the tidal zone subjected to chloride attack. In addition, the time-dependent regression equation is also developed and combined in computation. To validate the approach, the chloride diffusion predicted by the developed approach is compared to that measured in the previous study. From the study, it is found that the nonlinear and linear surface chloride functions are suitable for uncoated and coated concrete, respectively. The sensitivity analysis shows that the chloride content in concrete is most sensitive to the time-dependent parameter in the surface chloride functions. The surface coating can either decrease or increase initial surface chloride, and the deterioration rate of the surface coating depends on coating materials. By considering the change of the surface chloride after surface treatment, two criteria are proposed to assess the lifetime of coating materials, i.e., equivalent amount of surface chloride, and equivalent instantaneous slope of surface chloride. And, the lifetime is calculated and compared to other literatures. The service life extension of concrete structures with different surface coatings is also compared. The benefit of combining the repair by surface coating with the durability design by increasing concrete cover is also shown. [ABSTRACT FROM AUTHOR]

Chloride ingress in concrete is the most deteriorating factor for reinforced concrete structures exposed to marine environment. This phenomenon depassivates reinforcing steel in concrete and causes steel corrosion. To improve the durability and serviceability of concrete structures in harsh environments with high relative humidity, temperature and concentration of chloride ions such as in the Persian Gulf, the addition of silica fume and other pozzolans have been recommended by several investigations. In this paper, the chloride ion diffusivity and mechanical performance of concretes containing silica fume, metakaolin and natural zeolite, and those of concretes with different water-cement ratios (w/c) under in-situ tidal exposure condition were investigated. To achieve this objective, concrete specimens with w/c of 0.35, 0.40, 0.45 and 0.50 were fabricated. In addition, to examine the performance of pozzolans, other specimens with constant water-binder ratio (w/b) of 0.40 containing 5% silica fume, 5% metakaolin and 10% natural zeolite were prepared. All of the specimens were subjected to laboratory and tidal exposure in the field conditions. The results indicate that 10% natural zeolite, 5% metakaolin and 5% silica fume have similar effects on concrete strength and durability in harsh marine environments. In addition, it is concluded that at long time field exposure, chloride diffusion coefficient and surface chloride content of different mixtures reach to relatively similar amounts. [ABSTRACT FROM AUTHOR]

The subject of this paper is the extent to which, during wetting–drying cycles, chloride ions penetrate into fly ash modified concrete. Detailed chloride profiles were recorded which show how the total and water-soluble chloride contents vary with the depth of penetration of these ions into the concrete. In order to study the effect of exposure time, fly ash content, and fly ash composition on such penetration, two different types of fly ash were used as a partial replacement of Portland cement, their proportions amounting to 0%, 20% and 50% by weight of the binder. The results of the investigation showed that the chloride penetration depths were smaller in the case of the fly ash modified concretes than in the case of the unmodified concrete (i.e. concrete which did not contain fly ash), so that thinner layers of concrete cover could in this case be used to protect the steel reinforcement from the effects of corrosion. This indicates the potential beneficial effect of the use of fly ash on the service life of reinforced concrete structures. It is not just the porosity of the fly ash which plays a key role in the case of chloride penetration into concrete, but also the composition of the fly ash, and especially its calcium content. [ABSTRACT FROM AUTHOR]