ABSTRACT
The Hmong is one of the oldest ethnic groups in south-western China, and sound plays an important role in their culture. According to the general classification of landscape science, the rural soundscape of Hmong villages is divided into three types: a point soundscape dominated by a single sound source, a line soundscape with a typical Hmong rural village alley space as the sound field interface, and an area soundscape with the Bronze-drum Square, the only open public space of Hmong nationality, as the field. Combined with a sound collection and field test during field investigation, we obtained the characteristics of various rural soundscapes and evaluated the acoustic environment. The results showed that the "point" soundscape of medium- and low-frequency powder shotgun and wooden drum sounds in the unclosed Hmong villages exceed the transmission distance and sound durability. The "line" soundscape utilizes the turning point and envelope of different spaces to increase the acoustic reflection surface and create reverberation, increasing the propagation time and distance of the sound, and emphasizing the directivity of the sound through a long and narrow space. The "surface" soundscape includes the richest medium- and high-frequency-based human voice and music sounds and medium- and low-frequency musical instrument sounds, among others. The values of T30, EDT, and C80 in the sound field, all changed significantly because of the lack of acoustic reflection from the ceiling, through the top opening. Finally, the study reveals the cultural association between rural soundscape and space, which is reflected in the Hmong's "defensive" function and "group" culture. Thus, the Bronze-drum Square sound field does not meet the requirements of the current specification of cultural interpretation, and it is in the participatory Hmong performance mode, centered on drum club group structure.
ABSTRACT
Chromium (Cr)-bearing electroplating sludge is a hazardous solid waste and has a detrimental effect on human health and the environment. In this study, an alkali-activated slag binders, namely, formed by the reaction of blast furnace slag (BFS) with alkali, was applied to the stabilization/solidification (S/S) of electroplating sludge. The effects of liquid-solid ratio, water glass modulus ratio (molar ratio of SiO2 to Na2O), water glass dosage, and electroplating sludge amount on the compressive strength and Cr leachability of binders were analyzed. The related mechanism of the S/S of electroplating sludge was discussed on the basis of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive spectrometry (SEM-EDS). Results showed that the compressive strength of the alkali-activated slag binder first increased and then remained stable with the increase in liquid-solid ratio, water glass modulus ratio, and water glass dosage. By contrast, the leaching concentrations of Cr(VI) and total Cr decreased with the increase in liquid-solid ratio, water glass modulus ratio, water glass dosage, and curing time. In addition, XRD, FTIR, and SEM-EDS revealed that the hydration products of the binders were mainly low-crystallinity and dense calcium silicate hydrate gels, and Cr(VI) had been effectively immobilized in the structure. The reduction in Cr(VI) by the reductive components in the BFS boosted the stabilization of Cr-bearing electroplating sludge. Overall, the BFS binders containing electroplating sludge had relatively high compressive strengths and low Cr(VI) leaching concentrations. The physical encapsulation, chemical bonding, and absorption contributed the Cr immobilization during the S/S process of electroplating sludge.
