In order to determine the spatial variation and main influencing factors of groundwater drinking water quality, a total of 202 sampling sites were studied across all the groundwater drinking water sources in five districts of Tianjin. Water samples were collected at each sampling site during the low water period and high water period in 2018, and water quality parameters were analyzed. Single factor assessment, principal component analysis, and water quality index valuation were used to identify the spatial variation and assess the water quality. The results of different evaluation methods for groundwater drinking water quality were slightly different. There were some differences among the regions in Tianjin. Overall, the water quality of rural groundwater drinking water sources in the Ninghe District and Jizhou District was better than that in Wuqing District, Beichen District, and Jinghai District. There were nine main indicators of groundwater quality in Tianjin, namely fluoride, pH, sodium, bacterial count, chroma, chlorine, oxygen consumption, nitrate nitrogen, and sulfate, and most were affected by geological factors. The results of the water quality index valuation could better reflect the actual situation of rural groundwater drinking water quality. The influence of geological factors on groundwater was inevitable. Combined with the current management of township-level drinking water sources and the characteristics of water quality, the safety of drinking water should be improved through the installation of water purification facilities.

Humic substances(HS) are one of the most stable forms of organic matter with <i>in vitro</i> biological activity. This study reviews the chemical composition, structural characteristics, and physiological activity of HS and discusses the internal mechanism of the physiological activity based on the relationship between these aspects. The chemical composition of HS is uncertain, and the supramolecular structure model of HS is currently generally accepted. HS promotes the absorption and utilization of mineral elements by promoting the formation of root hairs and lateral root development, activating plasma membrane H<sup>+</sup>-ATPase to generate favorable electrochemical gradients and chelating mineral elements with acidic functional groups. With hormone-like activity, HS IAA secreted by plant rhizosphere growthpromoting bacteria(PGPR) or HS autologous component can activate plasma membrane H<sup>+</sup>-ATPase. HS can also increase endogenous plant hormone levels and promote plant growth and development. HS activates plasma membrane H<sup>+</sup>-ATPase by mediating messenger NO to eliminate reactive oxygen species(ROS) generated from HS-affected cells. HS mediates root development and morphological structure by regulating intracellular ROS homeostasis through NO and antioxidant enzymes. This study additionally focuses on the correlation between HS physiological activity and its chemical composition; the role of active sites such as —COOH and —OH, the electron transfers of quinone groups, and HS hydrophilic-hydrophobic balance are closely related to HS physiological activities. Future HS research should focus on analyzing HS molecular structures, clarifying the "common structural element" with physiological activity of the cross-feedback mechanism between HS-induced intracellular signal transduction pathways, and revealing the regulation mechanism of HS on gene expression related to material and energy metabolism in cells, aiming to provide a theoretical basis for the in-depth study of HS physiological activity mechanism and agricultural applications.

The scientific management of ecosystems is key to the sustainable development of ecosystems. Owing to their limitations, traditional management methods can no longer solve the complex problems encountered in ecosystem management. An emerging management method, namely adaptive management, has received wide attention from scholars. The quantitative characteristics of domestic and foreign studies on ecosystem adaptive management from 2010 to 2020 were examined by literature analysis and comparative analysis. The connotation development, type, and application conditions of adaptive management were classified. The main research direction of ecosystem adaptive management was summarized. The existing problems of current ecosystem adaptive management research were identified, and corresponding countermeasures and suggestions were proposed. The specific conclusions can be summarized as follows:The research direction of ecosystem adaptive management and the development trend of the number of documents are almost the same in China and abroad, but there is a large gap in the quantity of literature. The connotation of adaptive management has continually improved, but the application of ecosystem adaptive management still has limitations. Therefore, it is urgent to reach a unified understanding of the connotation and expand the application scope to take full advantage of adaptive management, promote sustainable ecosystem development, and achieve the best ecological, economic, and social benefits.

The purpose of this study was to isolate a skatole-degrading bacterium, and provide a high efficiency microorganism for the degradation of odor chemicals released from composting manure. A liquid culturing method was used to enrich skatole-degrading bacteria, and a pure culture was isolated using plate-streaking. The degrading ability of the candidate bacteria was pre-determined by smell assessment and chemotactic responses to skatole serving as the sole nutrition. The efficacy of strain Rp3 to degrade skatole at different concentrations was analyzed by high performance liquid chromatography(HPLC), and was identified based on the morphological and physiological characteristics, in combination with 16S rRNA gene sequence analysis. A skatole-degrading bacterium, Rp3, was isolated from soil under sheep manure compost collected from Shanxi Province. This strain showed chemotactic response to skatole. HPLC analysis indicated that the degradation time extended with the increase of skatole concentration. Strain Rp3 could completely degrade skatole at a concentration of 50 mg·L<sup>-1</sup> after co-culturing with skatole at 28℃ for 24 h, while the degrading time extended to 48 h with an efficacy of 98.4%, when the concentration was raised to 100 mg·L<sup>-1</sup>. The optimum pH for Rp3 growth was pH 7~8, and Rp3 exhibited good tolerance to salt stress, demonstrated by normal growth in a solution of 0~10% NaCl. Strain Rp3 was identified as <i>Rhodococcus pyridinivorans</i>, based on its morphological characteristics, the results of Biolog identification system and 16S rRNA gene sequence analysis. Strain Rp3 was identified as <i>Rhodococcus pyridinivorans</i>, and was shown to be a highly effective strain in degrading skatole, an odor chemical in compost.

In order to understand the characteristics of heavy metals in the soil around the Xikuangshan mining area(XKS) and their distribution in dominant plants, field investigations were conducted to analyze the quantities, sources, ecological and health risks, enrichment coefficients, and transfer factors of heavy metals in the dominant plants at 16 sampling points in the XKS. The results showed that the average concentrations of Sb, Cd, and Hg exceeded the corresponding background values of Hunan by 100%. The source analysis suggested that Sb, Hg, Zn, Cd, Pb, and As were mainly contributed by human activities. However, the sources of heavy metal pollution were not completely consistent, and there was combined pollution. The potential ecological hazard factor analysis showed that Sb, Cd, and Hg were the main single ecological hazard factors, and 62.50% of the samples possessed a very high comprehensive ecological risk index. The heavy metal health risk assessment results showed that the main pathway of human exposure was oral ingestion, and children were more susceptible to heavy metal pollution. Sb and As were the major non-carcinogenic and carcinogenic contributors, respectively. The enrichment coefficients and transfer coefficients of As and Sb in <i>Boehmeria nivea</i> were greater than 1, and their retention rates in heavily polluted areas were lower than those in the other six dominant plant species. Generally, there were severe ecological risks and health risks in the XKS. <i>Boehmeria nivea</i> has a strong potential for remediation of heavy metals and can be used as a remediation plant for heavy metal pollution in the XKS.

The study of soil bacterial community structure and functional groups in rice terraces can provide a theoretical basis for the sustainable management of terraces. Nineteen soil samples were collected at different altitudes in Longji rice terraces. Bacterial community structure was analyzed using 16S rRNA high-throughput sequencing, and its functional group was predicted using FAPROTAX functional prediction software. The results showed that the dominant phyla were Proteobacteria and Chloroflexi with 37.40%~63.28% and 11.30%~40.78% abundance, respectively. The dominant genera were <i>Sphingomonas</i> and <i>Rhodanobacter</i> with 7.13%~20.87% and 2.34%~21.53% abundance, respectively. Clustering heatmap of dominance operational taxonomic units(OTUs) showed that the environmental factors significantly related to bacterial abundance were pH, carbon-nitrogen ratio(C/N), alkali-hydrolyzed nitrogen(AN), and altitude. A total of 51 functional groups were predicted based on all the OTUs. Denitrification, sulfur respiration, and hydrocarbon degradation functional groups were significantly related to pH, C/N, AN, and altitude. The above results indicated that soil pH, C/N, AN, and altitude significantly affected soil bacterial community structure and functional groups in Longji rice terraces.

The effects of water-based waste drilling mud on soil physical properties and crop growth were studied. An indoor pot experiment was used to add 2%, 4%, 8%, and 12%(dry matter basis) water-based waste drilling mud into both sandy and loam loess. To alleviate the increase in soil pH caused by the addition of water-based drilling waste mud, the pot experiments were supplemented with a gypsum treatment. The experiment was divided into a control group, the mud group, and the mud+gypsum group. A crop of sugar beet was planted. Results showed that the application of different amounts of waste mud to the two types of soil did not lead to salinization in the absence of gypsum, and that the clay content increased while plant evapotranspiration decreased. Adding gypsum decreased soil pH but increased soil salt content significantly and prevented crop growth. In terms of the latter, pots containing soil with the 8% waste mud content saw the best sugar beet growth in both types of soils. After 40 days, the height of the sugar beet plants increased by 41.59%, their leaf area increased 2.43 times, their biomass increased 3.54 times, and their leaf SPAD value increased by 58.18% in sandy loess. In loam loess, the plant height, leaf area, biomass, and SPAD of the leaves increased by 1.75%, 32.03%, 14.59%, and 27.65% respectively. A certain amount of waste mud has a positive effect on the soil physical properties, and thus the growth of crops. The results indicate that water-based drilling waste from the oil and gas industry could be used on-site to improve coarse soils and decrease the cost of waste drilling mud.

In order to explore the problem of increased landscape fragmentation in semi-arid ecologically fragile areas during the urbanization process, based on the two periods of land use data from Guanghe County, Gansu Province from 2011 to 2018, this study integrated the moving window method, transect method, and gray correlation method to analyze the dynamic changes and driving mechanisms of landscape fragmentation in semi-arid ecologically fragile areas. The results suggested that the cultivated land was the landscape matrix of Guanghe County from 2011 to 2018, and the structural changes in landscape use types were clearer. Based on the transect method, the best research scale was determined to be 900 m, which was conducted at the township scale. The transect analysis found that the clustering effect of villages and towns led to a trend of landscape fragmentation. The closer the townships, the greater the degree of regional change, whereas the hills and mountains that were farther away had less changes. From the perspective of spatial distribution pattern changes, the overall landscape fragmentation showed an increasing trend. The sharply changing areas were concentrated in the towns and villages along the Guangtong River valley and the road, and showed a belt-like extension in space. The main driving forces for the fragmentation of the landscape in Guanghe County were the combined effects of policies and socioeconomic factors. Through the gray correlation analysis, it was found that five indicators, namely the regional gross product, population, gross per capita GDP, gross industrial output value, and transportation industry, were the main driving factors leading to the deterioration of the landscape. The influence of climate factors was lower than that of social economy factors. The research results can provide a reasonable basis for ecological environmental protection and sustainable development in semi-arid ecologically fragile areas.

With the rapid development of the livestock and poultry breeding industry in Huizhou, Guangdong Province, improper utilization of livestock and poultry fecal sewage may pollute cultivated land and even affect the drinking water source in the Dongjiang basin through surface runoff. In order to assess the carrying loads and risks of livestock and poultry fecal sewage in the cultivated land of Huizhou, this study collected the latest statistical yearbook data of livestock and poultry breeding in Huizhou and the second national survey of pollution sources. According to these data, the production and emissions of livestock and poultry fecal sewage and major pollutants(COD, NH<sub>3</sub>-N, TN, and TP) in 2018 were calculated using the method of the production and discharge coefficient. The cultivated land carrying loads and environmental risks of livestock and poultry fecal sewage, TN, and TP were then estimated and assessed based on the actual cultivated land area of each district(county). The results showed that in 2018, the quantity of poultry fecal sewage produced by livestock and poultry breeding in Huizhou was 1.51×10<sup>6</sup> t with emissions reaching 4.44×10<sup>5</sup> t, and the contribution proportion and its order for each livestock and poultry animal was pig(50.3%) > broiler(17.2%) > beef(14.3%) > layer(13.4%) > cow(4.8%). Moreover, the production and emissions of major pollutants totaled 2.61×10<sup>8</sup> kg and 7.66×10<sup>7</sup> kg, respectively. Among all the districts(counties), Boluo had the largest emission of fecal sewage because of its large scale livestock and poultry breeding, which accounted for 42.9%. The cultivated land carrying loads of livestock and poultry fecal sewage, TN, and TP in Huizhou were 7.69 t×hm<sup>-2</sup>, 65.38 kg×hm<sup>-2</sup>, and 15.63 kg×hm<sup>-2</sup>, respectively. The alarm grading levels for poultry fecal sewage and TN were level Ⅰ, whereas that for TP was level Ⅱ, and the threats caused by them to the surrounding environment were small. Thus, the resource utilization of livestock and poultry waste needs to be strengthened continuously through balance planning for planting and breeding.

Daily maximum temperature data during the rice heading-flowering stage(July-August) were obtained from the meteorological station for the period between 2000-2018, and the high-temperature temporal characteristics in Nanchong City were extracted using an accumulative anomaly method. The multi-year cumulative damage index of rice from heat injury was calculated in 17 stations within or around the Nanchong City, and the spatial characteristics of extremely high temperatures in Nanchong City were obtained using the ANUSPLIN interpolation software. The grade of each high-temperature disaster that occurred in rice areas of Nanchong City was eventually identified by combining the rice planting range, population distribution, and high-temperature disaster analysis model. The results showed that the year 2006 exhibited the highest intensity of extremely high temperature occurrences, which was followed by 2017; further, the number of days with extremely high temperatures was clearly higher than that observed in a year on average. The year 2010 represented the turning point of temperature change in Nanchong City; this is because the average daily maximum temperature between 2010 and 2018 was significantly higher than in the period between 2000-2010. It could be expected that the frequency and intensity of extremely high temperature occurrences would continue to increase in the near future. Peng'an and Yingshan were the two counties that were most frequently affected by extremely high temperatures, which were followed by the Gaoping District, Nanbu County, and Xichong County. The areas with high risk of heat damage were mostly distributed in the Gaoping and Yingshan counties; the areas with intermediate risk were widely distributed in all the counties, while low-risk areas were mainly distributed in the hilly regions situated toward the northwest of Nanbu, north of Langzhong, and northeast of Yingshan. Identifying high-temperature disaster areas can provide scientific references to the government for achieving a more organized agricultural sector and transforming urban areas.