Zhuo Muning

Bio: Zhuo Muning is an academic researcher. The author has contributed to research in topics: Surface runoff & Erosion. The author has an hindex of 7, co-authored 17 publications receiving 768 citations.

Effects of rainfall intensity and slope gradient on erosion characteristics of the red soil slope

Abstract: Soil erosion is one of the most serious driving forces of ecosystem degradation in the world that strongly affected by rainfall intensity and slope gradient. Therefore, a laboratory simulated rainfall study, with three slope gradients (5°, 15°, and 25°) subjected to seven rainfall intensities (30, 60, 90, 120, 180, 210, and 270 mm/h), was conducted to determine the effect of rainfall intensity and slope gradient on runoff generation, rate, sediment yielding, erosion rate, and runoff hydraulics characteristics of the red soil slope. The results indicated that runoff generation of red soil slopes was influenced by both the slope angle and rainfall intensity, runoff rate showed a steady condition after an initial trend of an unsteadily increased with increasing rainfall duration, while it did not increase with the increasing slope gradients, especially under the high rainfall intensity. Under the influence of high rainfall intensities, sediment yielding of the red soil slope was controlled by detachment limitation and then by transport limitation under low rainfall intensity. Under low and moderate rainfall intensities, erosion rate increased with slope angle due to the factors related to slope angle can enhance soil detachment or limit the protective effect of surface layer. Furthermore, runoff hydraulic characteristics of the red soil slope indicating that overland flows on all slopes were considered as laminar, tranquil, and supercritical, and the Reynolds numbers were significantly correlated with rainfall intensity. Results from this study can expand the understanding of the relationship among slope gradient, rainfall intensity, and erosion characteristics in the red soil region.

Coupling effects of erosion and surface roughness on colluvial deposits under continuous rainfall

Abstract: The colluvial deposits, resulting from the collapsing gully erosion, provide a large amount of sediment for subsequent water erosion in southeastern China. Previous studies have shown the apparent effects of rainfall, runoff and slope gradient on erosion of colluvial deposits, but paid little attention to the effect of soil surface roughness. The objective of this study was to investigate the relationship between surface roughness and erosion processes under continuous rainfall conditions. For this purpose, we repeated an indoor rainfall experiment 20 times on a colluvial deposit slope of 30°. The rainfall intensity was 3.33 mm min−1 and the rainfall lasted 60 min. We measured the sediment yield for each rainfall experiment and the related hydrodynamic parameters, including the flow velocity, Froude number, Reynolds number, Runoff power and Darcy-Weisbach resistance coefficient. We found that the gradual enrichment of coarse particles and gravel on the surface of the colluvial deposits led to an exponential decrease in sediment yield. The water erosion consists of three processes: (1) The emergence of the falling-sill, followed by the formation and rapid expansion of the rill; (2) The frequent expansion of the rill; and (3) The random landslide of the rill wall. The flow velocity, Froude number (Fr), Reynolds number (Re) and runoff power (ω) all showed a power decrease in contrast to a power increase of Darcy-Weisbach resistance coefficient (f) due to the influence of the roughness of colluvial deposits. The roughness and flow velocity can be used as good indicators for characterizing the water erosion intensity of the colluvial deposits. The findings will facilitate further research into the effect of roughness on the water erosion of colluvial deposits.

Effects of soil properties, topography and landform on the understory biomass of a pine forest in a subtropical hilly region

Abstract: Soil conservation will remain an essential subject for forest in slope land. However, the interactions between soil, vegetation and complex topography are not fully understood. To address this concern, field studies were performed in a typical small watershed in the subtropical hilly red soil region of China. This site covers an area of approximately 3.2 ha, and the mean slope steepness of the land is 15°. Soil properties (including available and total N, P, K, soil organic carbon (SOC), CEC, soil texture), understory vegetation biomass and diversity index on different slopes (different slope steepness, slope aspects, and slope positions) were measured. Meanwhile, interrelationships between understory vegetation biomass and soil properties, slope steepness and altitude were evaluated via redundancy analysis. The study results showed that the soil nutrients and SOC contents were greater in the down-slope and north and west slopes. And the soil properties displayed high spatial heterogeneity and had semi-variance structure, which were mainly derived from random factors. Due to obvious erosion characteristics and the negative correlations between soil properties and slope positions, we suspected that soil erosion was the primary random factor. In addition, the mean total understory vegetation biomass in the pine forest was 283.58 g m−2 (ranging from 66.60 to 573.79), and higher vegetation biomass was found in down-slope and north and west slopes. Further analyses indicated that topography (slope steepness and altitude) and soil properties combined contributed to 58.7% of the variations in the understory biomass, and they individually had a contribution of 17.3% and 41.4%, respectively. Moreover, altitude (height of slope positions) alone explained 15.9% of the variation of the vegetation biomass. This study indicated that soil properties, which were highly affected by slope aspect and slope position, were the most important factor in influencing understory vegetation biomass in subtropical pine forest. Slope position also had a tremendous direct influence on soil vegetation. Controlling understory soil erosion is essential for conservation of pine forest land in subtropical China.

Molecular Firefighting—How Modern Phosphorus Chemistry Can Help Solve the Challenge of Flame Retardancy

Abstract: The ubiquity of polymeric materials in daily life comes with an increased fire risk, and sustained research into efficient flame retardants is key to ensuring the safety of the populace and material goods from accidental fires. Phosphorus, a versatile and effective element for use in flame retardants, has the potential to supersede the halogenated variants that are still widely used today: current formulations employ a variety of modes of action and methods of implementation, as additives or as reactants, to solve the task of developing flame-retarding polymeric materials. Phosphorus-based flame retardants can act in both the gas and condensed phase during a fire. This Review investigates how current phosphorus chemistry helps in reducing the flammability of polymers, and addresses the future of sustainable, efficient, and safe phosphorus-based flame-retardants from renewable sources.