Characteristics of groundwater flow field after land creation engineering in the hilly and gully area of the Loess Plateau

In order to study the degree of influence and control mechanism to groundwater flow field caused by land creation engineering in the hilly and gully area of the Loess Plateau, based on the geological and engineering conditions of the first stage project of Yan’an new district in China, numerical simulation of groundwater flow is carried out by the Feflow and GIS technologies. From the simulation, punning measure relatively reduces infiltration recharge and artificial gravel drain increases groundwater seepage. The basic characteristics of groundwater flow field is controlled by the old and new topographies in the whole study area, and artificial gravel drain plays an auxiliary role in accelerating groundwater drawdown upstream and promotes groundwater rise downstream. According to differences of groundwater level and declining percentages of hydraulic gradient in the main and secondary gullies, dewatering of artificial gravel drain in the secondary gully is more effective than that in the main gully, which will yet play an important role in the future. The study results will make contributions to understand groundwater response to land creation engineering and will be beneficial to take necessary measures to prevent collapse of loess and failure of building foundation in the hilly and gully area of the Loess Plateau.     

Responses of meiofauna and nematode communities to crude oil contamination in a laboratory microcosm experiment

We examined the effects of crude oil contamination on community assemblages of meiofauna and nematodes after exposure to total petroleum hydrocarbons in the laboratory. We administered a seawater solution that had been contaminated with total petroleum hydrocarbons to seven treatment groups at different concentrations, while the control group received uncontaminated filtered seawater. The average density of total meiofauna in the experimental microcosms diluted with 0.5%, 1%, 2%, and 4% contaminated seawater was higher than the density in the control. The average density of total meiofauna in the 8%, 15%, and 20% microcosms was lower than the density in the control. The density of nematodes was similar to that of the total meiofauna. Cluster analysis divided the microcosms into group 1 (control, 0.5%, 1%, 2%, and 4% microcosms) and group 2 (8%, 15%, and 20% microcosms). However, SIMPROF analysis showed no significant difference between the two groups (p > 0.05). Bolbolaimus spp. (37.1%) were dominant among the nematodes. Cluster analysis showed similar results for nematode and meiofaunal communities. The total meiofaunal density, nematode density, and number of Bolbolaimus spp. individuals were significantly negatively associated with the concentration of total petroleum hydrocarbons (Spearman correlation coefficients, p < 0.05). Within the nematodes, epistrate feeders (group 2A: 46%) were the most abundant trophic group. Among the treatment groups, the abundance of group 2A increased in low-concentration microcosms and decreased in high-concentration microcosms. Thus, our findings provide information on the effects of oil pollution on meiofauna in the intertidal zones of sandy beaches.     

Long-term variations in macrobenthic community diversity (species number) in the Chokchon macrotidal flat,Incheon, Korea

We performed a time-series analysis of environmental variables and biological parameters to understand temporal variations in the macrobenthic community in the Chokchon macrotidal flats, Incheon, Korea. Bimonthly sampling of macrobenthos and sediments was conducted from May 1989 through November 2001. A decomposition method composed of seasonality, trends and cyclical variation was employed in this study. We focused on trends of the selected variables and assumed that those with positive or negative trends caused changes in biological parameters. Most variables showed strong seasonality (≥ 95% of the total variance). Significant positive trends (p < 0.0001) were observed in sea water temperature and sediment ignition loss. Macrobenthic biomass and species number also showed significant positive trends (p < 0.0001). Biomass indicated that the study area underwent eutrophication since the mid 1990s. A notable increase in species number occurred throughout the study period. The flattened temperature trend after 1994 and intensified eutrophication after the mid 1990s indicated that the species increase in the former period was in response to increasing temperature, while that in the latter period was caused by eutrophication. Although our study suggested an increasing trend in diversity, it is important to check for unexpected changes and establish monitoring programs to provide early warnings, especially in lower latitudes.     

Ultimate Bending Capacity of Strain Hardening Steel Pipes

Based on Hencky’s total strain theory of plasticity, ultimate bending capacity of steel pipes can be determined analytically assuming an elastic-linear strain hardening material, the simplified analytical solution is proposed as well. Good agreement is observed when ultimate bending capacities obtained from analytical solutions are compared with experimental results from full-size tests of steel pipes. Parametric study conducted as part of this paper indicates that the strain hardening effect has significant influence on the ultimate bending capacity of steel pipes. It is shown that pipe considering strain hardening yields higher bending capacity than that of pipe assumed as elastic-perfectly plastic material. Thus, the ignorance of strain hardening effect, as commonly assumed in current codes, may underestimate the ultimate bending capacity of steel pipes. The solutions proposed in this paper are applicable in the design of offshore/onshore steel pipes, supports of offshore platforms and other tubular structural steel members.     

Seasonal variation and principle of cyanobacterial biomass and forms in the water source area of Chaohu City,China

We investigated seasonal variations in cyanobacterial biomass and the forms of its dominant population(M. aeruginosa) and their correlation with environmental factors in the water source area of Chaohu City,China from December 2011 to October 2012. The results show that species belonging to the phylum Cyanophyta occupied the maximum proportion of phytoplankton biomass,and that the dominant population in the water source area of Chaohu City was M. aeruginosa. The variation in cyanobacterial biomass from March to August 2012 was well fitted to the logistic growth model. The growth rate of cyanobacteria was the highest in June,and the biomass of cyanobacteria reached a maximum in August. From February to March 2012,the main form of M.aeruginosa was the single-cell form; M.aeruginosa colonies began to appear from April,and blooms appeared on the water surface in May. The maximum diameter of the colonies was recorded in July,and then gradually decreased from August. The diameter range of M. aeruginosa colonies was 18.37–237.77 μm,and most of the colonies were distributed in the range 20–200 μm,comprising 95.5% of the total number of samples. Temperature and photosynthetically active radiation may be the most important factors that influenced the annual variation in M. aeruginosa biomass and forms. The suitable temperature for cyanobacterial growth was in the range of 15–30°C. In natural water bodies,photosynthetically active radiation had a significant positive influence on the colonial diameter of M.aeruginosa(P0.01).     

Complete nuclear ribosomal DNA sequence amplification and molecular analyses of <Emphasis Type="Italic">Bangia</Emphasis> (Bangiales,Rhodophyta) from China

Filamentous Bangia, which are distributed extensively throughout the world, have simple and similar morphological characteristics. Scientists can classify these organisms using molecular markers in combination with morphology. We successfully sequenced the complete nuclear ribosomal DNA, approximately 13 kb in length, from a marine Bangia population. We further analyzed the small subunit ribosomal DNA gene (nrSSU) and the internal transcribed spacer (ITS) sequence regions along with nine other marine, and two freshwater Bangia samples from China. Pairwise distances of the nrSSU and 5.8S ribosomal DNA gene sequences show the marine samples grouping together with low divergences (00.003; 0–0.006, respectively) from each other, but high divergences (0.123–0.126; 0.198, respectively) from freshwater samples. An exception is the marine sample collected from Weihai, which shows high divergence from both other marine samples (0.063–0.065; 0.129, respectively) and the freshwater samples (0.097; 0.120, respectively). A maximum likelihood phylogenetic tree based on a combined SSU-ITS dataset with maximum likelihood method shows the samples divided into three clades, with the two marine sample clades containing Bangia spp. from North America, Europe, Asia, and Australia; and one freshwater clade, containing Bangia atropurpurea from North America and China.