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[Objective] Black rock series contain high amounts of cadmium (Cd) and selenium (Se). During weathering and soil formation on the rocks, the chemical form transformation and release of Cd and Se from the rocks can have an impact on the surrounding ecological environment. [Methods] In this study, a black rock series distribution area of Hetang formation of the Lower Cambrian was selected in northwest Zhejiang. By collecting horizonal soil samples from soil profiles along different parts of the terrain (hill upslope, hill middle slope, hill downslope, inter hill valley bottom and valley terrace), the quantity and chemical form transformation patterns of Cd and Se during the process of weathering soil formation and weathering material migration of the black rock series were discussed. [Results] The results showed that total Cd and total Se in the soil decreased from parent rock to soil. The loss of Cd and Se in the weathered matter of black rock series increased with the increasing of transportation distance along the hilly slope, and the loss of Cd and Se in the process of evolution from slope deposit to diluvium was greater than that from residual to slope deposit. The Cd and Se lost from the weathered materials could affect the contents of Cd and Se in the topsoil derived from the alluvial of the downstream river in the way of water diffusion, but the degree of influence decreased with the increasing of distance. With the increasing of the transportation distance of weathered materials and the evolution of soil, the transformation of carbonate bound Cd and residual Cd to water-soluble Cd, exchangeable Cd, organic matter bound Cd and oxide bound Cd occurred. The residual Se gradually activated and transformed into exchangeable Se, organic matter bound Se and oxide bound Se. The results also showed that soil water-soluble Cd, exchangeable Cd (Se) and organic matter bound Cd (Se) showed an increasing trend toward the surface. The organic enrichment and topsoil enrichment of Se were more obvious than those of Cd. [Conclusion] The results indicated that the weathering of black rock series could not only directly affect the contents of soil Cd and Se in their distribution area through residue, but also affect the contents of soil Cd and Se in the surrounding areas through water diffusion.

With the development of all-optical networks, all-optical devices have become a research hotspot in recent years. Two-dimensional materials, represented by graphene and black phosphorus, have attracted great interest in the scientific community due to their excellent optical, electrical, magnetic, and mechanical properties. Bridging the gap between fiber optics and nanotechnology, microfibers can interact with light and matter at the micro or even nanoscale. By combining two-dimensional materials with microfibers, composite waveguides can be formed. They have the advantages of high nonlinear effect, all-fiber structure, and high damage threshold, etc. The composite waveguide can be directly applied to optical fiber communication systems, and plays an important role in the field of all-optical signal processing with a huge application prospect. In this review, the properties of typical 2D materials are first introduced. Next, the preparation methods of the relevant equipments are introduced and compared. Then, the all-optical signal processing technology based on 2D material-integrated microfiber composite waveguide is reviewed. The latest developments of all-optical modulators, all-optical wavelength converters, all-optical logic gates and all-optical thresholding devices are presented. Finally, the challenges and opportunities for the future development of 2D materials-integrated microfiber optoelectronic devices are summarized.

Graphdiyne has an inborn band gap energy, where the minimal band gap is about from 0.46 to 1.22 eV, which shows great potential in ultrafast laser generation. In this work, we fabricate a graphdiyne-decorated microfiber and demonstrate its saturable absorption characteristics experimentally. This device is used as a saturable absorber to generate the conventional soliton and noise-like pulse in an erbium-doped mode-locked fiber laser. The conventional soliton with a spectral bandwidth of 2.45 nm can switch into noise-like pulse with 37.14 nm bandwidth by adjusting the pump power and the polarization controller. For the noise-like pulse, the mode-locked state has excellent stability with 2.17 nJ maximum pulse energy and 283 fs coherent peak duration. This work indicates that graphdiyne could be a remarkable nonlinear photonic device to explore the dynamics of various mode-locked pulses.

We integrally demonstrate 2 μm mode-locked pulses performances in all-fiber net anomalous dispersion cavity. Stable mode-locking operations with the center wavelength around 1950-1980 nm can be achieved by using the nonlinear polarization rotation structure and properly designing the dispersion management component. Conventional soliton is firstly obtained with a total anomalous dispersion cavity. Due to the contribution of commercial ultra-high numerical aperture fibers, net dispersion is reduced to -0.077 ps2. So that stretched pulse with 19.4 nm optical bandwidth is obtained and the de-chirped pulse-width can reach 312 fs using extra-cavity compression. Under pump power greater than 890 mW, stretched pulse can evolve into noise-like pulse with 41.3 nm bandwidth. The envelope and peak of such broadband pulse can be compressed with up to 2.2 ps and 145 fs, respectively. The single pulse energy of largely chirped stretched and noise-like pulse can reach 1.785 nJ and 1.53 nJ, respectively. Furthermore, extra-cavity compression can also contribute to a significant increase of peak power.

A field experiment with five lime rates (0, 3.75, 7.50, 11.25, and 15.00 Mg ha-1) was maintained on a red soil (Ultisol) for 15 years to determine changes of soil acidity and effect on crop yields. The soil acidity decreased while exchangeable Ca in plough layer (0-20 cm) increased with lime rate and time. The decreased subsoil (20-60 cm) acidity started to occur four years after liming, and the extent of decreased soil acidity increased with lime rate and time. The increased ranges of exchangeable Mg2+ in subsoil were greater than that of exchangeable Ca2+, suggesting that downward movement of Mg2+ into the subsoil was faster than that of Ca2+. Lime application significantly increased the yields of crops studied. During the period of experiment, the maximum yield increased 4.67 times for barley, 2.24 times for mungbean, 57.3% for wheat, 53.4% for sesame, 52.8% for broad bean, 44.1% for potato, 35.1% for rapeseed, 32.1% for cotton, 28.4% for corn, 18.5% for watermelon, 11.0% for cowpea and 8.8 % for soybean. Liming at the highest rate was in favor to the decline in subsoil acidity and yield increase, especially for the later period of the experiment. Residual effects of reducing soil acidity by liming for the treatments of 0.5 L, 1.0 L, 1.5 L, and 2.0 L could last for 5, 7, 12, and 14 years, respectively, and the effects of lime application on the yields could last for more than 15 years. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate a passively mode-locking thulium-doped fiber laser based on the combination of the nonlinear polarization rotation (NPR) and the semiconductor saturable absorber mirror (SESAM). In contrast to SESAM mode-locking merely, the fiber lasers based on NPR working together with SESAM have more advantages. By using two mode-locking mechanisms, the nonlinear effect can be enhanced tremendously; then, the threshold of high-order harmonic mode-locking (HML) pulse trains can be decreased, and the pulses width can be compressed. The shapes of the pulses can also be reshaped better, and the HML pulse trains stability can be improved. The high repetition rate of 1.78 GHz is obtained by both NPR and SESAM in the experiment. Because of the variation of the gain-and-loss distribution in the cavity, the output wavelength of mode-locking fiber laser can be tuned from 1839 to 1890 nm, and the multiwavelength HML is also observed in the experiment.