[Research Progress and Prospect of Herbicide Residue Characteristics in Black Soil Region of China].

Food security is the top priority of a country. As an important granary in China, the northeast black land is a "ballast" to ensure national food security. However, the long-term and high-intensity application of herbicides in black land farmland has led to the accumulation and migration of herbicides in the soil, which affects soil quality, crop yield, and quality and hinders sustainable agricultural development in the black soil. To solve the problem of herbicide residues in black land farmland, it is necessary to control the application of herbicides from the source, as well as to elucidate the current situation, spatial and temporal evolution, and driving factors of herbicide residues, in order to achieve scientific prevention and control and precise policy implementation. The main contents of this study were as follows:1systematically summarize the application status and problems of herbicides in the farmland of black soil in China, suggesting that there are currently problems such as irregular application and insufficient product innovation of herbicides in the farmland of black soil; 2 comprehensively analyze the current status of herbicide residues, identify the deficiencies in recent studies on herbicide residue characteristics, spatial distribution, and pollution diagnosis in the farmland of black soil, and clarify the gaps in the research on the residue characteristics of herbicides in the farmland of black soil; and 3 propose the research prospect and key orientation for the herbicide residue diagnosis and risk management in the farmland of the black soil region of China. The results of this study can provide science and technology support for guaranteeing soil health, food security, and ecosystem security of black land farmland in China.

[Meta-analysis of the Effects of Metal Mining on Soil Heavy Metal Concentrations in Southwest China].

Metal mining is one of the main contributors of soil heavy metals. Previous studies examining the impact of metal mining on surrounding soil have mainly focused on one or a few metal mining areas. However, such studies cannot effectively inform the management of heavy metal pollution in soil at an inter-provincial scale. As part of this study, literature was collected on soil heavy metals (i.e., As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) affected by metal mining in regions of Southwest China (i.e., Yunnan Province, Sichuan Province, Guizhou Province, Chongqing Municipality, and Tibet Autonomous Region); Next, the impact of metal mining on the soil concentrations of these metals was quantified through meta-analysis, and the relationships between the selected factors (i.e., different sub-regions, metal minerals, and land-use types) and soil heavy metal concentrations were explored. Finally, the literature data was tested for publication bias. The results showed that metal mining in Southwest China has significantly increased the concentrations of heavy metals in topsoil. The different metals were ranked according to their weight effect sizes (ES+) in the following order Cd > Pb > Hg > Zn > As > Cu > Ni > Cr. Metal mining in both Sichuan and Yunnan led to higher effect sizes of soil Cd (ES+Sichuan=4.16, ES+Yunnan=3.20) and Pb (ES+Sichuan=3.47, ES+Yunnan=2.54) than those of the other heavy metals, while metal mining in Guizhou led to a higher effect size of soil Hg (ES+=2.80). The effect size of metal mining on soil heavy metals was higher in cultivated soil (ES+=1.42) than in forested soil (ES+=0.50). The mining of lead-zinc and tin significantly increased the concentrations of soil Cd, Pb, and Zn, and the mining of copper significantly increased the concentrations of soil Cu, Cd, and Pb. Of the investigated soil heavy metals in Southwest China, Pb and Zn showed slight potential publication biases (P<0.05). The above results can provide more effective information for the environmental protection of soil in metal mining areas of Southwest China.

[Quantitative prediction of soil salinity content with visible-near infrared hyper-spectra in northeast China].

Studying the spectral property of salinized soil is an important work, for it is the base of monitoring soil salinization by remote sense. To investigate the spectral property of salinized soil and the relationship between the soil salinity and the hyperspectral data, the field soil samples were collected in the region of Northeast China and then reflectance spectra were measured. The partial least squares regression (PLSR) model was established based on the statistical analysis of the soil salinity content and the reflectance of hyperspectra. The feasibility of soil salinity prediction by hyperspectra was decided by analyzed calibration model and independent validation. Models accuracy was also analyzed, which was established in the conditions of different treatment methods and different re-sampling intervals. The results showed that it was feasible to predict soil salinity content based on measured reflectance spectrum. The results also revealed that it was necessary to smooth measured hyperspectra for spectral prediction accuracy to be improved significantly after smoothing. The best model was established based on smoothed and log(l/x) transformed hyperspectra with high determination coefficients (R2) of 0.6677 and RPD = 1.61, which showed that this math transformation could eliminate noise effectively and so as to improve the prediction accuracy. The largest re-sampling interval is 8 nm that could meet the accuracy of the soil salinity prediction. Therefore, it provided scientific reference of monitoring soil salinization by remote sensing from satellite platform.

[Estimates and affecting factors of soil organic carbon storages in Yunnan-Guizhou-Guangxi Region of China].

Soil organic carbon (SOC) plays a key role in the terrestrial eco-systems. However, there is a large variation in SOC estimates at regional and global scales. In order to improve the accuracy of SOC estimates, the SOC storage in Yunnan-Guizhou-Guangxi Region of China (include Yunnan Province, Guizhou Province and Guangxi Zhuang Municipality) was estimated using 798 soil profiles and 1:500 000 digitized soil map, and the dominant affecting factors on SOC density were also discussed employing stepwise regression and path analysis. Results showed that the SOC storages estimated in the 0-20 cm and 0-100 cm layers are 4.39 Pg and 10.91 Pg, respectively; and the corresponding SOC density are 56.2 Mg x hm(-2) and 139.8 Mg x hm(-2), respectively. The mean SOC density of Yunnan-Guizhou-Guangxi Region is higher than that of China. The environmental factors (including altitude, longitude, latitude, annual mean precipitation and annual mean temperature), soil parent materials and land use could explain 37.9% and 30.7% of the variability of SOC density to the upper 20 cm and 100 cm, respectively. The environmental factors are the dominant affecting factors of SOC density. The effect of temperature is more important than that of precipitation, and the temperature and precipitation mainly vary with altitude and latitude, respectively. Except for temperature and precipitation, there are also other factors varying with altitude, longitude and latitude significantly affect SOC density. And the effects of other factors are more important than that of precipitation.