ABSTRACT
The aim of this study was to explore the carbon storage potential of karst forest soils in the Lijiang River Basin, reveal the spatial pattern of soil organic carbon (SOC), investigate the contributions and pathways of each driving factor to the spatial distribution of soil organic carbon, and provide a scientific basis for assessing the carbon cycle function of karst forests in the region. We employed structural equation modeling (SEM) and correlation analysis to investigate the spatial distribution characteristics of forest soil organic carbon in different basin sections (upper, middle, and lower reaches) and soil layers at different depths of the Lijiang River. Additionally, the direct and indirect ratios of each factor were quantified. The results showed that the overall soil layer of karst forest soils in the Lijiang River Basin was shallow, and soil organic carbon was phenoconcentric. The distribution of soil organic carbon content in different watershed sections was upstream > downstream > midstream, and the distribution of readily oxidizable carbon (ROC) and dissolved organic carbon (DOC) was consistent, whereas the distribution of microbial biomass carbon (MBC) was upstream > midstream > downstream. The contribution of various biotic and abiotic factors to the spatial distribution of soil organic carbon in karst forests in the watershed was different, and their contributions were ranked in descending order as:soil physicochemical factors > soil organic carbon active fraction > sample elevation > sample species diversity, with the total effects of 1.148, 0.574, 0.284, and -0.013, respectively. Among them, the sample site elevation had only an indirect effect on soil organic carbon, and the soil organic carbon active fraction had only a direct effect on soil organic carbon. Among the driving factors, total soil nitrogen, soil oxidizable organic carbon, sample site species richness, and soil soluble organic carbon could be used as important predictors of soil organic carbon content in karst forests in the Lijiang River Basin. Therefore, it is necessary to establish an effective eco-environmental protection mechanism covering the whole Lijiang River Basin, to reduce and control the impact of anthropogenic disturbances (especially in the middle urban section of the Lijiang River Basin), and to enhance and protect the species diversity of karst forests in the basin in order to improve soil physicochemical properties, improve and enhance the content of the soil organic carbon active fraction, and enhance the soil organic carbon stocks of karst forests in the Lijiang River Basin through other effective ways, as well as to promote the enhancement of the regional forest carbon sink function.
ABSTRACT
In this work, a simple side-polish plastic optical fiber (POF)-based surface plasmon resonance (SPR) sensor is proposed and demonstrated for simultaneous measurement of refractive index (RI) and liquid level. The effects of side-polish depths on the sensing performance were studied. The experimental results show that the SPR peak wavelength will be changed as the RI changes, and the SPR peak intensity will be changed with the liquid level variation. By monitoring the changes in peak wavelength and intensity, the RI and liquid level can be detected simultaneously. Experimental results show that an RI sensitivity of 2008.58 nm/RIU can be reached at an RI of 1.39. This sensor has the advantages of simple structure and low cost, which has a good prospect in the field of biochemical sensing.
Subject(s)
Refractometry , Surface Plasmon Resonance , Optical Fibers , Plastics , Poland , Surface Plasmon Resonance/methodsABSTRACT
In this paper, counter current salting-out homogenous liquid-liquid extraction was combined with dispersive liquid-liquid microextraction for the determination of environmental estrogens in water samples by high-performance liquid chromatography. In this method, initially, sodium chloride was filled into a syringe and a mixture of water sample and acetonitrile was driven to pass through the syringe. Due to salting-out effect, fine droplets of acetonitrile went up through the remaining mixture and aggregated as a separated layer on the top. Then, the collected organic phase (acetonitrile) was removed with a syringe and mixed with carbon tetrachloride (extraction solvent). In the second step, the mixed organic phase was rapidly injected into 5 mL of distilled water to further enrich the analytes. Good linearity was obtained in the concentration range of 2.0~200 ng/mL for diethylstilbestrol (DES) and 8.0~200 ng/mL for octylphenol (OP), respectively. Limits of detection were 0.09 ng/mL for DES and 0.20 ng/mL for OP, respectively. Relative standard deviations for intra- and inter-day precisions were less than 2.1 and 3.1%, respectively. Finally, the established method was successfully applied to determine DES and OP in river water, well water, bottled water and campus drinking water samples with recoveries in the range from 81.0 to 105.9%.
