Humic substances (HS) is widely used in agriculture and soil improvement as an important component of soil organic matter. Based on summarizing the effect and mechanism of HS on heavy metals in soil, the potential of phytoremediation of heavy metal pollution in soil was analyzed by literature investigation:(1) Macromolecule humin (HM) and humic acid (HA) could passivate heavy metal ions and reduce the toxicity of heavy metals to crops. However, smaller molecular-weight fulvic acid (FA) could promote the migration of heavy metals from the underground part to the upper part of the plant. (2) In addition to the physical and chemical properties of soil, the binding of HS with metal ions was mainly influenced by the ionic strength, molecular weight and the quantity of active functional groups and the pH of HS. (3) There are two methods of adding HS: foliar spraying and soil addition. Foliar spraying can inhibit the transport of heavy metals into plants and protect the photosynthetic system from heavy metals. Adding low concentration of HS in soil can promote the transport of heavy metals, but high concentration will have a negative effect on plants. (4) According to the ecotoxicological effects of the interaction of HS and heavy metals, the leaching effects of soil column and the growth development of plants, the secondary environmental risk caused by HS could be evaluated. Therefore, HS can be used as an environmental friendly phytoremediation enhancer to expand the application of phytoremediation in heavy metal contaminated soils.

It is crucial to improve our understanding of regional carbon cycling and climate change mitigation by quantifying the contribution of afforestation to regional carbon sequestration. Based on forest resource planning and design data as well as afforestation information from Xingshan County, Hubei, this study applied a regional-scale forest carbon budget model (CBM-CFS3) to simulate and evaluate the impact of afforestation on the carbon stocks and carbon sequestration rates of forest ecosystems in this region from 2009 to 2030 in both afforestation and non-afforestation scenarios. Results show that the average carbon stock and annual carbon sequestration rate of forest ecosystems in this region would be 16 540.55 Gg and 208.04 Gg·a^-1 under afforestation, respectively, representing values that are 472.85 Gg (2.94%) and 16.01 Gg·a^-1 (8.34%) higher than those under BS scenario, respectively. The proportion of carbon stocks in biomass and dead organic matter accounted for 19.11% and 80.89%, respectively; therefore, these two carbon pools contributed 94.15% and 5.85% to the carbon sequestration rate in afforested areas, respectively. Afforestation increased the average carbon stocks of both Pinus massoniana forests and deciduous broad-leaved forests by 237.23 and 235.63 Gg, respectively. This enhanced the carbon sequestration rates of these two forest ecosystems by 6.44 and 9.57 Gg·a^-1, respectively. Afforestation improved forest carbon stocks and carbon sequestration rates by changing the forest age structures in this region. Clearly, planting more deciduous broad-leaved forests and improving forest management will enhance the forest carbon sequestration capability and promote sustainable development of forest resources.

Resulting from natural processes or induced by human activities, desertification is an important global ecological and environmental challenge. China has recently initiated a series of ecological restoration programs at national and regional scales. However, regular monitoring and assessment of related ecosystem services in the ecological engineering areas can also provide fundamental references for the implementations of desertification control measures. This study estimated the dynamic changes of sand-fixing service in Xilin Gol League, which is located in Inner Mongolia Autonomous Region, in the north-western part of an extensive sandstorm source control project region, and represents 44% of the total project area. The RWEQ model was applied, and the influences of rainfall and vegetation coverage on sand-fixing capacity were analyzed. The results indicate that the average annual amount of sand-fixing service reached 1.456 billion tons of sand during the period of 2000-2015, with an average sand-fixing capacity of 74.78 t·hm^-2. These values annually increased by 7.1% and 6.3%, respectively. In addition, the sand-fixing service in Xilin Gol League showed a gradually decreasing trend from southeast to northwest and northeast, mainly due to the lower wind erosion risk in the northeastern part. Compared with 2000, approximately 32.63% of the Xilin Gol League area presented an improvement in the sand-fixing service in 2015, also, the degradation area and unchanged area of sand-fixing service occupied 15.55% and 51.82%, respectively. Furthermore, the change of sand-fixing service significantly correlated with vegetation coverage and rainfall in Xilin Gol League. The results reveal that the integrated influences of climate change, ecological engineering and human activities on sand-fixing service should receive more attention, and additional effective control measures on wind erosion in the weak improvement regions should be adopted.

Developing rural tourism is one of the most important grips for realizing the rural revitalization strategy. In order to understand the spatial distribution characteristics of agritainment resorts in central Chongqing, and to optimize its spatial development pattern, 564 agritainment points of interest (POI) captured from Baidu map were taken as the research objects. The the distribution characteristics of agritainment resorts in central Chongqing were analysed from distribution type, equilibrium of spatial distribution and spatial pattern, by means of GIS spatial analysis technology and mathematical statistics analysis methods. The results show that the distribution type of agritainment resorts in central Chongqing is cohesive; the regional distribution is not balanced and is uneven; the spatial pattern is "multi-center cluster distribution" type, and there forms a "U-shaped" agritainment core density circle, which basically forms a strip-like spatial pattern with concentrated and contiguous pieces. The Beibei and Nanan Districts are high-density gathering centers. The main influencing factors of its spatial distribution are topography, vegetation cover, traffic conditions, tourism resources, tourist market and economic density.

Spatial prediction of soil heavy metals is of great significance for utilization of regional soil resources, environment protection and pollution prevention. Jintan District in Changzhou City, Jiangsu Province was chosen as study area. Spatial variation model (BP-K), source-sink model (BP-S) and comprehensive model (BP-SK) were applied to simulate and predict the spatial distribution of heavy metals, including Cd, Pb, Cr, Cu and Zn. The results of the Models' performance were evaluated by coefficient of determination, root-mean-square deviation, mean absolute error and so on. Furthermore, the prediction results from the best performance model were selected to calculate heavy metal spatial distribution in each sub-region. The results show that:(1) The coefficient of determination of BP-SK model was higher than that of BP-S and BP-K for Cd, Cr, Cu and Zn. Only for Pb, the coefficients of determination of BP-S and BP-K were higher than that of the BP-SK model. BP-SK can strengthen local characteristics and uncover more information. (2) The comprehensive model performed better than original single model. The root-mean-square deviation of Cd, Pb, Cr, Cu and Zn were improved by 15.15%, 20.71%, 19.19%, 1.75% and 9.24%, respectively. (3) In prediction results, the high-value areas for Cd, Pb, Cr, Cu, and Zn were located in the central and northeastern parts, and the low-value areas were located in west hilly and mountainous areas. The BP-SK model has a better performance in areas with severe human influence, while the BP-K model has better applicability in hilly area where natural factors have a greater impact.

The promotion and application of organic fertilizer is of great significance to the improvement of the quality of cultivated land and to the achievement of the transformation of agricultural green development. Based on the survey data of 1 086 farmers in Hubei Province, Logit model, mediation model and moderation model were employed to explore the influence mechanism of policy incentive and value identification on farmers' adoption of organic fertilizer. Results show that:(1)Farmers' adoption of organic fertilizer is influenced by policy propaganda, government subsidies, policy regulation, environmental crisis awareness and ecological environment improvement. (2)Environmental crisis awareness, ecological environment improvement and agricultural civilization inheritance intermediate the relationship between policy propaganda and farmers' adoption of organic fertilizer; ecological environment improvement moderates the influence of policy regulation on the adoption behavior. (3)Government subsidy enhances the positive relationship between environmental crisis awareness and the adoption of organic manure. Therefore, it is necessary to properly subsidy for farmers to make green agricultural production, to strengthen the education of farmers, and to change the traditional technology promotion mode, thus arousing farmers' initiative in adopting green production technologies.

The contribution factors of increasingly pesticide consumption can be divided into cropping area, pesticide application dosage and cropping structure adjustment. The contribution rates of the three factors to the total growth of pesticide consumption in both national and regional levels have been measured and calculated, respectively. The relationship between pesticide consumption and cropping structure adjustment from 2006 to 2016 have been analyzed. In respect of the cropping structure in China in recent years, there have been an increasing on the proportion of crops with high pesticide application dosage and a decreasing on the proportion of crops with medium and low pesticide application dosage, and vegetables topped the proportion growth of high-dosage crops with 1.38% increase rate. The southwestern region of China achieved the most considerable adjustments in agricultural cropping structure with an 8.54% growth of proportion of high-dosage crops. From the decomposition results of driving factors of pesticide consumption growth, the average contribution rate of cropping structure adjustment reached 50.10%, and stood out as the most crucial factor propelling the pesticide consumption growth in some years. Besides, the southwestern, central and southeastern regions of China all underwent high-level substitution of crops with medium and low pesticide application dosage by high-dosage ones, and cropping structure adjustment played an essential role in elevating pesticide consumption in the three regions. Hence, the cropping structure adjustment is of strategic importance in the control and reduction of pesticide consumption:employ reasonable economic means to guide the agricultural cropping structure's transformation into "pesticide-saving" type; strengthen regionalization of pesticide consumption control, and focus on the adjustment of agriculture cropping structure in high-intensity pesticide consumption areas; intensify efforts of policy supports in pesticide reduction and substitution technologies and improve the technology adoption rate of farmers households; enhance the construction of pesticide consumption control system to ensure the green development of agriculture.

The establishment of protected areas system is an important measure to protect natural resources, ecological environment and biodiversity. Several geographic mathematical methods such as nearest neighbor index, central index of geography, kernel density estimation, and geo-detector were applied to study the spatial distribution characteristics and major influencing factors of four main protected areas including the nature reserves, forest parks, wetland parks, and state-owned forest farms in Zunyi City, Guizhou Province. The results show that:(1) The four types of protected areas in Zunyi City have obvious spatial aggregation, forming three high-density aggregation areas, showing the distribution characteristics of "northwest-southeast dense, southwest-northeast sparse". (2) The establishment of protected areas in Zunyi is not keeping up with the pace of the regional development, 64.29% of the regions belong to the "lagging" and "passive" types, forming a concentration area and a contiguous area. (3) The explanatory power of an individual influencing factor is not stable. Wetland area, per capita GDP and forest area are the main influencing factors of the spatial distribution of the studied protected areas; the explanatory power of any two combined influencing factors is significantly strengthened.

Xingshan County of Hubei Province is situated in the Three Gorges Reservoir Area. In order to know well macro-ascomycetous species in this county and improve the understanding of the biodiversity of the Three Gorges Reservoir Area, a series of survey of macro-ascomycetous and collecting of specimens were carried out in the duration from October of 2016 to August of 2018. The specimens were identified based on morphological and molecular systematic methods. A total of 96 species belonging to 4 classes, 5 orders, 20 families, and 48 genera were confirmed. Among them, forty species were recorded for the first time in Hubei Province, such as Ascocoryne cylichnium, Bisporella citrina, Chlorociboria poutoensis and so on. The most dominant genus was Peziza, including 9 species accounting for 9.38% of the total species, and the most dominant family was Pyronemataceae, including 17 species accounting for 17.71% of the total species. Most of the species were widely distributed in the areas with 800-1 600 m above sea level and mainly grown in the evergreen and deciduous broad-leaved mixed forest. Lachnum abnorme was found as the widely distributed species. There were 41 species of geophilous fungi, 40 species of lignicolous fungi, 10 species of entomogenous fungi, 2 species of fungicolous fungi and 3 species of geophilous or lignicolous fungi. A phylogenetic tree based on the LSU rDNA sequence was constructed, showing the relationship among major macro-ascomycetes species in Xingshan County.

Soil meso- and micro-fauna across 8 plant communities in Dajinshan Island were investigated in the seasons of autumn (October), winter (December) in 2017, and spring (March), summer (June) in 2018. Totally, 8 506 soil animals were captured that belong to 5 phyla, 14 classes, and 23 groups. Among these animals, Nematoda, Acari, and Collembola were the dominant groups which accounting for 66.06%, 17.95%, and 11.15%, respectively. The others (4.84%) were belonging to rare groups. The annual average density and group number of soil meso- and micro-fauna in evergreen broad-leaved forest in autumn were higher than those in deciduous broad-leaved forest, and significantly different in group number (P<0.05); Density of soil meso- and micro-fauna in summer was significantly higher than in other seasons that both in the two forests (P<0.05); Group number of soil meso- and micro-fauna in evergreen broad-leaved forest in autumn was significantly higher than that in spring and winter (P<0.05), and the number of deciduous broad-leaved forest in autumn was significantly higher than that in other seasons (P<0.05). The density of soil meso- and micro-fauna in both two forests was higher in the surface layer, and in 0-5 cm soil layer in evergreen broad-leaved forest and 0-20 cm in deciduous broad-leaved forest that accounted for the fauna density of 68.68% and 66.94%, respectively. Shannon-Wiener and Margalef richness indexes in evergreen broad-leaved forest were higher than in deciduous broad-leaved forest, and they were higher in autumn than those in other seasons (P<0.05); Shannon-Wiener index in deciduous broad-leaved forest in autumn was significantly higher than in other season (P<0.05). Pearson's correlation show that the density of soil total, Nematoda, Acari and Collembola animals were positively correlated with soil organic matter, and negatively corrected with soil pH.

Transgenic maize with insect-resistant gene cry1Ab/cry2Aj and herbicide-tolerant gene G10evo-spsps was planted during the whole growth period. In order to investigate the effect of planting insect-resistant and herbicide-tolerant transgenic maize on rhizospheric microbial communities, quantitative PCR and high-throughput sequencing technologies were employed to analyze the community abundance and composition of bacteria and fungi in maize rhizosphere soils at the jointing and mature stages. The isogenic non-transgenic maize was chosen as the control. Results show that planting transgenic maize had no significant impact on the rhizospheric soil physicochemical properties, fluorescein diacetate hydrolase activity, microbial community abundance and microbial community diversity. At the phylum level, planting transgenic maize significantly increased the relative abundance of rhizospheric Actinobacteria at the jointing and mature stages; at the genus level, planting transgenic maize significantly decreased the relative abundance of rhizospheric Candidatus_Nitrososphaera at the jointing and mature stages. Planting transgenic maize had no impact on fungal taxa at the phylum level, but significantly affected the relative abundance of Fusarium, Staphylotrichum and Lophiostoma at the genus level. In addition, growth stage significantly affected rhizospheric soil dissolved organic carbon and total nitrogen contents; rhizospheric bacterial (rather than fungal community composition and diversity) also affected by growth stage. The findings could provide basic data and theoretical support for the management and control of natural ecological risk of genetically modified crop industrialization.

Gene flow is one of the important environmental risks of transgenic crops. China is one of the most important country with cultivated soybeans and wild soybeans. Furthermore, the distribution area of cultivated soybean and that of wild soybean highly overlap in China. Therefore, strict evaluation and researches on gene flow from transgenic soybean to cultivated soybeans and wild soybeans must be conducted before the commercial cultivation of transgenic soybeans in China. In Yitong County, Jilin Province, transgenic EPSPS+PAT soybean S4003.14, developed by local organization, was studied on its gene flow to 5 cultivated soybeans and 5 wild soybeans. The results show that the flowering overlaps of S4003.14 and the 5 non-transgenic soybeans were 17-27 days, and that of S4003.14 and 5 wild soybean lines were 19-23 days. Under the intercropping condition, as the results of gene flow, the outcrossing rates of transgenic EPSPS+PAT soybean S4003.14 to the 5 non-transgenic soybeans and to the 5 wild soybeans were 0.16%-0.93% and 0.06%-0.19%, respectively. The fertility of the hybrid offsprings was normal. No gene flow was detected when the distance between S4003.14 soybean and non-transgenic cultivated soybeans was more than 1 m.

In order to investigate the influence of grass covering on the soil quality of an apple orchard and explore the soil factors that limiting the apple yield in Jixian County of Shanxi Province, three grass-covering methods (planted grass RC, natural grass ZC and clear farming QG) were selected to study the physical, chemical and enzymatic activities of the orchard soils. Soil fertility quality was assessed by canonical correspondence analysis, principal component analysis, total data set (TDS), minimum data set (MDS) and gray correlation degree (GRA). The results show that:(1) the soil water content and soil pH of the field covered with natural grass significantly increased; (2) soil organic matter, total nitrogen, total phosphorus and total potassium concentration of the field covered with artificial grass significantly increased; (3) catalase activity was highest under natural grass, polyphenol oxidase and urease activities were the largest under planted grass, and sucrase was the largest under clear farming. (4) there are six indicators (soil bulk density, soil water content, organic matter, available potassium, total phosphorus, urease) in the MDS for soil quality assessment in the study area. The results of soil quality evaluation show that grass covering significantly improved soil quality, and the effect of planted grass cultivation was better than natural grass cultivation. Similar conclusion was found by using the method of GRA. The limiting factors of soil fertility in Jixian County are soil water content, organic matter, and sucrase activity. Organic matter and sucrase activity are the main limiting factors for yield. Increasing organic matter content and soil enzyme activity are the main ways for improving soil fertility in orchard soils.

The water use, biological characteristics, concentration of sulfur dioxide (SO₂) and meteorological data were acquired by the sap flow measurements and environmental monitoring techniques. Based on the coupling relationship between water vapor and trace gas through two-dimensional exchange of pores, the canopy stomatal conductance for SO₂ (G_SO2), canopy SO₂ uptake flux (F_SO2), and accumulated stomatal SO₂ flux (F_SO2,st) of four dominant tree species (Pinus manssoniana, Castanopsis chinensis, Schima superba, and Machilus chinensis) in a natural mixed conifer-broadleaf forest at Dinghushan, south China were determined. The results show that, on a daily scale, the time at which the maximum concentration of SO₂ appeared was partly overlapped the time when the maximum G_SO2 occurred, and the maximum absorption of the four dominant tree species occurred at around noon time. On a seasonal scale, the average concentration of SO₂ in the dry season (from October to March) was 10.11 nL·L^-1, which was higher than that in the wet season (from April to September), 5.41 nL·L^-1. The G_SO2 of the four species was significantly higher in the wet season than that in the dry season (P<0.001), while the F_SO2 in the wet season was higher than that in the dry season (P<0.001). Furthermore, the F_SO2,st of C. chinensis and M. chinensis were 2.16 and 2.50 mmol·m^-2, which were higher than 1.70 and of 1.91 mmol·m^-2 for P. massoniana and S. superba, respectively. The SO₂ stomatal absorption behavior of the four dominant tree species was mainly affected by factors such as vapor pressure deficit (VPD), photosynthetically active radiation (PAR) and SO₂ concentration. This research provides the basic data for the reasonable evaluation of SO₂ absorption flux in mixed coniferous-broadleaf forests in the Pearl River Delta region, and provides a basis for risk prevention for environmental assessment.

Wetlands constructed beside Dianchi Lake play important roles in reducing non-point source pollution and maintaining the ecological diversity. In this study, high-throughput sequencing technology was used to reveal the bacterial community structures in the sediments grown with three representative emergent plants, Acorus calamus, Phragmites communis and Canna indica in Dounan Wetland beside Dianchi Lake. The results show that the bacteria occupying relatively high abundance at the phylum level were Proteobacteria, Chloroflexi, Actinobacteria and Acidobacteria. At the genus level, the dominant bacteria were the unknown genus belonging to Anaerolineaceae and Pseudomonas. The richness and diversity of the bacterial communities in sediment with Acorus calamus were the largest. The bacterial richness in sediment with Phragmites communis was higher than that with Canna indica, but the diversity was lower. The bacterial community structure in sediments from different sampling points with the same macrophyte was similar, but was greatly different in those with different macrophytes, indicating that plant species had a significant effect on sediment bacterial community characteristics. The contents of available phosphorus and organic matter had a greater effect on α and β diversities of the sediment bacterial communities compared with nitrate and ammonium contents.

Cr⁶⁺ can usually cause lipid peroxidation stress in organisms due to its strong oxidative capacity. In this study, the reproductive toxicity of Cr⁶⁺ exposure on female Polymesoda erosa was investigated. Five concentration groups of Cr⁶⁺ were set as 0, 0.25, 1, 4 and 8 mg·L^-1 and the exposure time of each concentration group was set as 0, 5, 10 and 15 d. The results indicate that the exposure to Cr⁶⁺ could cause oxidative stress on the ovaries of Polymesoda erosa and change the expression of er (estrogen receptor gene) and vtg (vitellogenin gene). Compared with control group, the high concentration of Cr⁶⁺ treatment groups could significantly reduce the gonadosomatic index (GSI) of Polymesoda erosa (P<0.05). Moreover, the GSI varied significantly with the increase of Cr⁶⁺ concentration as time goes by. The expression of vtg and er in high concentration treatment group was significantly lower than that in low concentration treatment group as well as control group (P<0.05). In addition, it was found that the activities of CAT, GST and MDA content in ovaries would get back to normal level (P>0.05) after exposing to low concentration of Cr⁶⁺. On the other hand, high concentration of Cr⁶⁺ exposure would eventually inhibit the activities of both enzymes (P<0.05) and increase the content of MDA significantly. The results manifest that Cr⁶⁺ has tissue damage and metabolic disturbance effects on the ovaries of Polymesoda erosa and high concentration of Cr⁶⁺ would cause obvious toxic effects on the reproduction of Polymesoda erosa.

Non-target analysis of surface water, soil and sediment samples from the Yangtze and Wujiang rivers at Fuling City was conducted with ultra-high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry combined with Compound Discoverer (v. 3.0) software. Accurate screening and pollution-level assessment of 14 organic pollutants in the region were conducted through a quantitative analysis of environmental pollutants with high detection frequency and exposure risk. The water samples were extracted by solid phase extraction (HLB column) while the soil and sediment samples were ultrasonically extracted with acetonitrile. The treated samples were separated by a Hypersil Gold C18 column (50 mm×2.1 mm×1.9 μm) and eluted with 0.1% aqueous formic acid solution and acetonitrile. The detection and analysis were performed separately with electrospray ionization, and in Full MS/ddMS2 + Discovery monitoring mode, positive ion mode and negative ion mode. In total, 137 organic pollutants were identified in the samples after full-scan non-targeted screening. The pollutants could be divided into pesticides, pharmaceutical and personal care products, and plastic additives. Of these, 14 pollutants with high concentration and detection frequency were chosen for quantitative analysis in various environmental media. The water samples contained 12 types of pollutants with concentrations ranging from non-detectable to 286 ng·L^-1. The soil and sediment samples contained eight pollutant types, ranging from non-detectable to 30.9 ng·g^-1. Six pollutants were present in all water, soil and sediment samples. This study demonstrates a rapid and efficient high-throughput technology to determine unknown environmental pollutants. The results of this research are significantly helpful for rapid screening of highly exposed organic pollutants in the environment.