A non-parametric indicator Kriging method for generating coastal sediment type map

Coastal sediment type map has been widely used in marine economic and engineering activities, but the traditional mapping methods had some limitations due to their intrinsic assumption or subjectivity. In this paper, a non-parametric indicator Kriging method has been proposed for generating coastal sediment map. The method can effectively avoid mapping subjectivity, has no special requirements for the sample data to meet second-order stationary or normal distribution, and can also provide useful information on the quantitative evaluation of mapping uncertainty. The application of the method in the southern sea area of Lianyungang showed that much more convincing mapping results could be obtained compared with the traditional methods such as IDW, Kriging and Voronoi diagram under the same condition, so the proposed method was applicable with great utilization value.

Loss on Ignition-Based Indices for Evaluating Organic Matter Characteristics of Littoral Sediments

Understanding organic matter characteristics （e.g., amount and state） of sediments is necessary for evaluating both the sediment and water environments; however, methods that have been proposed to investigate these characteristics are relatively expensive. This study attempted to evaluate the organic matter characteristics of littoral sediments by employing solely the loss on ignition （LOI） method, which is the most economical and accessible method in developing countries. Different types of sediments were first oven dried at 100 ~C and then continuously burned at 200, 300, 400, 500, and 600 ~C for 4 h at each temperature. The mass LOI at each temperature was calculated and compared with the 100 ℃oven-dried weight. Our results suggested that the mass LOI across the temperature range of 200-300 ℃（LOI200-300）：mass LOI at 600 ℃ （LOI600） ratio （LOI200-300/LOI600） could represent different types of sediments as well as the organic matter：organic C ratio. Compared with the sediments unaffected by wastewater, the sediments that were more influenced by the inflow of domestic wastewater had a higher LOI200-300/LOI600. Interestingly, LOI200-300/LOI600 could also represent changes in the organic matter characteristics as a function of organic matter decomposition in sediments. In conclusion, the organic matter characteristics of littoral sediments could be evaluated using solely the LOI method, particularly with LOI200 - 300/LOI600.

Three-Dimensional Modeling of Shallow Shear-Wave Velocities for Las Vegas, Nevada, Using Sediment Type

A three-dimensional model of near-surface shear-wave velocity in the deep alluvial basin underlying the metropolitan area of Las Vegas, Nevada （USA）, is being developed for earthquake site response projections. The velocity dataset, which includes 230 measurements, is interpolated across the model using depth-dependent correlations of velocity with sediment type. The sediment-type database contains more than 1 400 well and borehole logs. Sediment sequences reported in logs are assigned to one of four units. A characteristic shear-wave velocity profile is developed for each unit by analyzing closely spaced pairs of velocity profiles and well or borehole logs. The resulting velocity model exhibits reasonable values and patterns, although it does not explicitly honor the measured shear-wave velocity profiles. Site response investigations that applied a preliminary version of the velocity model support a two-zone ground-shaking hazard model for the valley. Areas in which clay predominates in the upper 30 m are predicted to have stronger ground motions than the rest of the basin.

Temporal variation of resource allocation between sexual and asexual structures in response to nutrient and water stress in a floating-leaved plant

Aims Adaptive plasticity of biomass allocation to different environmental stressors enables plants to maintain functional relationships among reproductive structures.In freshwater systems,water depth and nutrient content of sediments can have a major effect on biomass allocation in aquatic macrophytes.However,the relative importance of these two stressors is unknown as it is the temporal variation of biomass allocation to the stressors during the growing period.This information may be critical for understanding the tolerance of a plant to environmental conditions.Methods Here,we used four levels of environmental stressors generated by deep and shallow water and high or low sediment nutrient content in a factorial experiment to investigate the biomass allocation responses of a floating macrophyte,Trapella sinensis,during the growing period.Important Findings The results showed that the lower sediment nutrient content inhibited biomass increase,whereas the lower water depth increased the sexual reproduction of the plants.The lower sediment content also led to a delay in flowering and compensated trade-offs among sexual reproduction and elongation and clonal reproduction during the growing period.These results indicated that water depth affected the ratio of biomass allocation,whereas the sediment nutrient content affected biomass accumulation when the plants faced these two environmental factors simultaneously.The temporal changes in allocation under lower sediment nutrient content underscored the importance of collecting data at different stages of growth when trying to interpret resource allocation,especially in resource-limited environments.