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Table of Content

Volume 36 Issue 2
25 February 2020
Table of Contents
2020, 36(2):  0-0. 
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Mechanisms of Plant Tolerance to Heavy Metals Mediated by Gibberellic Acid
ZHANG Chun-yu, WANG Hai-juan, WANG Hong-bin
2020, 36(2):  137-144.  doi:10.19741/j.issn.1673-4831.2019.0689
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Heavy metals are toxic to most plants and severely interfere with their physiological metabolism. Some adaptive mechanisms, including improved antioxidant response, enhanced photosynthesis rate, adjusted metabolism rate and metal compartmentalization, have been evolved to alleviate the stress of heavy metals. As a classical hormone for regulating the growth and development of plants, gibberellic acid (GA) can enhance the plant tolerance to and uptake of heavy metals. This review summarizes the mechanisms of plant tolerance to heavy metals mediated by gibberellic acid, with an emphasis on plant biomass improvement, antioxidation, remediation of photosynthetic system, metal compartmentalization and signal communication. The future prospects, including the biosynthesis, decomposition as well as regulated roles of GA under heavy metal stress, the in-depth mechanisms of enhanced plant tolerance by GA, and the effects of GA application on phytoremediaiton efficiency, are also proposed.
Analysis of Water Resources Utilization Efficiency and Its Affecting Factors in Grain Production: An Empirical Research Based on China's Inter-Provincial Panel Data
CHANG Ming, CHEN Si-bo, MA Bing-ran, LIU Ying
2020, 36(2):  145-151.  doi:10.19741/j.issn.1673-4831.2019.0366
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Super-efficient SBM model was performed to explore the temporal and spatial characteristics of the comprehensive efficiency, the pure technical efficiency and the scale efficiency of water resources utilization in grain production from 2008 to 2017 in China. Tobit model was applied to examine the impact of natural environment and irrigation strategies on water resources utilization efficiency. The results show that there was still much room for improvement in the water resources utilization efficiency in China. The comprehensive efficiency and pure technical efficiency showed an inverted "U" trend, whereas the scale efficiency showed an increasing trend before 2011, and then maintained stable. The scale efficiency was higher over the coastal areas compared to the inland areas. The low technical efficiency contributed to the low comprehensive efficiency in the main grain-producing areas including the northern coastal region, northeast China and the middle reaches of the Yangtze river, while the low comprehensive efficiency over the middle reaches of the Yellow River and the southwest was mainly due to the low scale efficiency. Both effective irrigation and grain breeding techniques made positive contribution to the three efficiencies, while negative contribution was due to the rural water source construction. Further, the disaster degree also showed a negative impact on the comprehensive efficiency and the scale efficiency. Finally, proposals for improving water resources utilization efficiency are suggested based on our analysis.
The Influence of Ecological Farming on Farmers' Income: An Example of Rice Growers in Jiangxi Province
XIE Xian-xin, CHEN Mei-qiu
2020, 36(2):  152-160.  doi:10.19741/j.issn.1673-4831.2019.0417
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Ecological farming is important for improving the effectiveness of farmland protection and ensuring the quality and safety of crops. A micro-survey data was obtained by interviewing 1 488 rice growers in 47 counties (districts) of 11 prefecture-level cities in Jiangxi Province. The OLS regression model and Heckman regression model were used to measure the overall impact of ecological farming on farmers' income. Furthermore, the quantile regression model was introduced to deeply analyze the income effect of ecological farming on farmers at different income levels. The research results show that:(1) Adopting ecological farming helps farm households to increase production return per capita farmland, while it will have different effects due to different income levels of farmers. (2) Ecological farming has a positive impact on production return per capita farmland for very low/low income farmers, a negative impact on middle and above middle income farmers, and only has a significant impact on the production return per capita farmland of high income farmers. (3) Two control variables, including livelihood differentiation and proportion of farmland income, have a significant impact on production return per capita farmland. The paper puts forward some policy suggestions, such as increasing support for low-income farmers' ecological farming policies, actively guiding the non-agricultural employment of middle and high-income farmers, and practically strengthening the moderate scale operation of farmland.
Spatial and Temporal Evolution Characteristics and Simulation Prediction of Ecological and Economic Coordination Degree in Huizhou Based on a CA-Markov Model
LI Long, WU Da-fang, LIU Yan-yan, GONG Jian-zhou, LIU Yi-hua, ZHENG Jin-yu
2020, 36(2):  161-170.  doi:10.19741/j.issn.1673-4831.2019.0668
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Land change science focuses on the relationship between the ecological environment and the economy, which is beneficial for sustainable development. Based on remote sensing images of Huizhou City from 2000 to 2015, a CA-Markov model was used to predict land use cover change in 2025. For this,1 km×1 km land use data were employed and the ESV values and GDP were calculated as the ecology and economy. An EEHC model was used to couple the economy and the ecological environment and prospective spatio-temporal evolution was explored. To reveal coupled coordination and spatial variation characteristics of these factors in rapid urbanized region, Getis-ord Gi* was used to analyze the coordination degree of spatio-temporal variation. The results show that:(1) Compared with other periods, the predicted land use pattern of Huizhou in 2025 has a higher land use efficiency. Although the landscape fragmentation in this region is prominent, it has been effectively alleviated compared with the earlier period. (2) In the past 20 years, EEHC had changed significantly, and the unbalanced area was larger than the concerted area. The spatial distribution was unbalanced, and the phenomenon of polarization is more serious than before. In addition, the level of ecological and economic coordination is generally not high, while the developed areas has been changing from uncoordinated to coordinated gradually expanding. The area distributed around the developed areas gradually expanded. (3) The EEHC spatial distribution pattern evolved from a single cold point aggregation in 2000 to a common distribution of two cold and hot spots in 2025, and the hot spots gradually migrated to the cold spots. The concerted developmental level of the economy and ecology in rapidly urbanized regions was low, and the situation was more serious. However, it had a good tendency, and the problem of spatial varied imbalance was more pronounced. In the developed areas while developing the economy, the intensity of ecological restoration and protection should also be increased, which is beneficial for the sustainable development of the economy and ecological synergy. This study provides a theoretical basis for future researches to promote the coordinated development of land security, ecological environment, and economic development. The results are of great significance for the sustainable development of natural, economic, and social systems, which are important for the sustainable development of cities.
Analysis of Soil pH, Organic Matter, Nitrogen and Phosphate Characteristics Under Different Land Use Types in Taige Canal Valley
ZHU Yong-qing, CUI Yun-xia, LI Wei-di, XU Lu, XIA Meng-ru, CAO Wei-qi
2020, 36(2):  171-178.  doi:10.19741/j.issn.1673-4831.2019.0721
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In this work, 120 soil samples were collected from the Taige Canal valley, and the number of samples for paddy field, irrigated field, orchard land, forestland and wasteland were 45, 18, 25, 22 and 10, respectively. In order to enhance the soil farmland fertilizer management and non-point source pollution control, contents and spatial distribution characteristics of pH, soil organic matter (SOM), total nitrogen (TN) and total phosphorus (TP) under different land use types were analyzed by using mathematical statistics and ArcGIS technology. Results indicate that:(1) All the studied soils were acidic with an average pH of 5.36. The TN and SOM were abundant while TP was relatively deficient, which corresponded to the level two, level two and level five, respectively, according to the nutrient classification standards of the second national soil survey. In addition, the differences in soil pH, TN and SOM contents under different land use types were highly significant (P<0.01). The pH values were in the following sequence:wasteland > paddy field > forest land > irrigated land > orchard land; and TN content gave the following sequence:paddy field > irrigated land > orchard land > forest land > wasteland; whereas SOM content decreased in the following sequence of paddy field > orchard land > irrigated land > forest land > wasteland. These differences were probably due to the differences in type and application dosage of chemical fertilizers, planting system, vegetation coverage, and farming management. However, no significant differences were found in soil TP contents among the five land use types, which might be attributed to the single fertilization, soil phosphorus leaching and loss. (2) Spearman correlation analysis among soil nutrients show that TN had a negative correlation with pH value (P<0.05), but exhibited a significant positive correlation with SOM and TP. (3) Under different land types, the soil pH exhibited small variation to medium variation. TN and SOM showed moderate variation. TP for all the land types had high variation except for wasteland. The acidic soils were distributed widely and regularly in the Taige Canal valley. The high levels of TN and SOM were mainly concentrated in the middle and lower reaches of Taige Canal, while the high content areas of TP were concentrated in the south side of the middle and lower reaches.
Study on Spatial Heterogeneity of Alkali-Hydrolyzable Nitrogen in Paddy Fields at the County Scale
HUANG Shi-hui, FANG Bin, LI Xin, HE Sha-sha
2020, 36(2):  179-185.  doi:10.19741/j.issn.1673-4831.2019.0412
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A good understanding of the spatial variability of nitrogen in soil is important for the best management of soil nutrients. For this study, Yangzhong City in Jiangsu Province, China, was chosen as the study area. The data were taken from the soil of 99 plow layer samples collected from paddy fields in Yangzhong. The spatial variation characteristics of alkali-hydrolyzable nitrogen (AN) and what affected that variation at a county scale were studied using geostatistics analysis methods and buffer analysis. The results show that:(1) The average content of soil AN in the study area was 114.30 mg·kg-1, which was at a rich level. (2) Semivariance analysis showed that the soil AN was moderately spatially auto-correlated. (3) Spatial interpolation results showed that the spatial distribution of soil AN in Yangzhong was generally in convex patches; high in the middle and low at sides of the areas. The high-value areas were located mainly in the middle three towns of the study area, and local extreme-value areas appeared near polluted industrial areas and breeding bases. (4) Analysis of the affecting factors indicated that urbanization, soil texture, industrial distribution, and farmer management had a great effect on the spatial distribution of soil AN in the study area. The soil was prone to accumulate alkali-hydrolyzable nitrogen within 1 km of the breeding cooperatives, and the industrial enterprises had significant effects on soil alkaline nitrogen in a range of 600 m (P<0.05).
Study on the Characteristics and Physical Causes of Groundwater Fluoride and Iodide Over the Yellow River Alluvial Plain in the Southwest of Shandong Province
XU Xiong, XIAO Pei-ping, SUN Yan-ting, LI Min, DONG Ying-shang, GAO Shang-zan, LIU Wen-xin
2020, 36(2):  186-192.  doi:10.19741/j.issn.1673-4831.2019.0274
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208 groundwater samples were collected within Heze, the key representative region in the Yellow River alluvial plain over the southwest of Shandong Province, to investigate the compound concentration, geographical distribution and physical causes of groundwater fluoride and iodide. Results of the analyses show that the fluoride concentrations for all the deep groundwater samples exceed the threshold limit of class Ⅲ (1.0 mg·L-1) of "Standard for Groundwater Quality" (GB/T 14848-2017), and 60.3% of the shallow groundwater samples exceed the threshold limit of fluoride concentration. Moreover, 61.8% and 56.3% of the deep and shallow groundwater samples, respectively, exceed the recommended standard value of iodide concentration (≤ 0.15 mg·L-1) derived from World Health Organization. In addition, well depth plays a significant role on the fluoride and iodide concentrations. In shallow well, fluoride concentration increased with the increase of water depth, while the severe over-standard rate of iodide concentration declined with the increase of water depth, and the water samples that were seriously exceeding the standard value mainly concentrated within 30 m of water depth. In deep well, the water samples with the fluoride and iodide concentrations seriously exceeding the standard value were principally concentrated below 400 m of water depth.
Characteristics and Ecological Risk Assessment of Heavy Metal Pollution of Triassic osmotic Paddy Soil in the Southwest of Guizhou Province
HUANG An-lin, FU Guo-hua, QIN Song, FAN Cheng-wu, LIU Gui-hua
2020, 36(2):  193-201.  doi:10.19741/j.issn.1673-4831.2019.0453
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To investigate the pollution status and spatial distribution of heavy metals in paddy soil of the southwest Guizhou Province, the arable layer of paddy soil samples were collected and the concentrations of Cd, Hg, As, Pb, Cr and soil pH were measured and analyzed by multivariate statistical techniques. The variety of spatial distribution for 5 heavy metals were studied using geographic information system (GIS). Single factor pollution index, Nemero comprehensive pollution index and potential ecological risk index were applied to evaluate the heavy metal contamination degree. The results show that the mean concentrations of heavy metals in the surface of paddy soil were in the order of w(Cr)(201.68 mg·kg-1) > w(Pb)(38.25 mg·kg-1) > w(As)(30.70 mg·kg-1) > w(Cd)(0.68 mg·kg-1) > w(Hg)(0.22 mg ·kg-1). The contents of Cd and As in some soil samples were higher than risk screening values for soil contamination of agricultural land in the Soil Environmental Quality Standard (GB 15618-2018), whereas the Hg, Pb and Cr contents were lower than the screening values. Anthropogenic influence caused an enrichment of Cd and As in paddy soils. The accumulation of Cd, Hg, As and Cr in soil was mostly affected by gold smelting, coal combustion and agricultural strategies, and the main sources of Pb were exhaust emission. Current study confirm that heavy metal pollution and industrial activities in smelters posed a serious threat to environmental quality. According to the single-factor pollution index, the pollution degree was in the order of Cd > As > Cr > Hg > Pb, and the Nmeiro comprehensive pollution index showed 39.64% points in the study area exceed 1. As for the ecological risk assessment, the risk index (RI) value of the 5 kinds of heavy metals was 63.78, which was lower than the lowest value of RI (150), and indicated the degree of ecological risk belonged to slight scale.
Assessment of Ecological Environment Status in the Longxi-Hongkou National Nature Reserve Based on Remote Sensing Ecological Index
LIU Li-bing, XIONG Kang-ning, REN Xiao-dong
2020, 36(2):  202-210.  doi:10.19741/j.issn.1673-4831.2019.0853
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The giant panda nature reserve play a momentous role in maintaining the biodiversity of its surrounding areas. A catastrophic earthquake happened in Wenchuan in the year of 2008 caused a severe ecological degradation in many panda's habitats nearby. Based on four phases of the Landsat images from 1998 to 2017 in Longxi-Hongkou National Nature Reserve, the study integrated principal component analysis method and four indicators including normalized vegetation index (NDVI), normalized difference built-up and soil index (NDSI), and land surface temperature (LST) to build a remote sensing ecological index (RSEI) and form a comprehensive evaluation model to synthetically assess the ecological environment status in the study area. The results show that the RSEI values of Longxi-Hongkou National Nature Reserve in 1998, 2007, 2008 and 2017 were 0.748 1, 0.752 1, 0.411 0 and 0.599 1, respectively. It indicates that the ecological environment in the study area got better first then deteriorated and improved at last during the period of 20 years, but the overall trend was in a degraded state. It is noteworthy that the ecological environment changed significantly before and after the earthquake, especially the ecological environment in the hilly and subalpine areas with an elevation of 1 400-2 600 m showed an obvious deterioration trend, mainly because the vegetation distruction caused by the earthquake, which has resulted in the reduction of water area and the formation of bare land. Green degree and wetness have positive effects on the key factors affecting the ecological environment, while dryness and heat have negative effects on the ecological environment.
Land Type Information Extraction and Landscape Pattern Dynamic Analysis of Laoshan Scenic Area
SUN Min, ZHOU Chun-guo, ZOU Chang-xin, ZHANG Zheng-nan, LIU Dong
2020, 36(2):  211-219.  doi:10.19741/j.issn.1673-4831.2019.0426
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The Laoshan scenic area is an ecological barrier and biodiversity conservation area in Nanjing City. The dominant ecosystem in Laoshan is forest, its ecological position is extremely important. This study aims to analyze the dynamic changes of the landscape pattern in the scenic area for the past 17 years. Local land use information based on Landsat images from 2001, 2005, 2009, 2013 and 2017 was extracted, using the technical method of object-oriented fuzzy classification, C5.0 decision tree classification, pixel-based maximum likelihood, artificial neural network and support vector machine. In addition, Fragstats 4.2 software was used to extract multiple landscape pattern indexes, for the comparison of dynamic landscape pattern from 2001 to 2017. Results show that the object-oriented fuzzy classification method had the highest overall accuracy (91.79%) and Kappa coefficient was 0.83. With the continuous construction and reform, the degree of landscape fragmentation in Laoshan scenic area has deepened. From 2001 to 2017, the number of patches (NP) showed an increasing trend, and reached 653 in 2017, with the patch density of 5.928 1 blocks·km-2. In 2017, contagion index (CONTAG) increased compared with that of 2001, reaching 59.41%, and the connectivity of dominant patch types has improved. The Shannon's diversity index (SHDI) value fluctuated in a narrow range, reaching a maximum of 0.725 5 in 2009. With the development of construction to a mature state, the overall development process slowly enters into an orderly state, and scenic area in Laoshan has gradually developed towards harmony and stability.
Above- and Below-Ground Biomass Carbon Allocation Pattern in Temperate Desert Steppe of Inner Mongolia, China
HU Fei-long, YAN Yan, YU Dan-dan, LU Xiao-qiang, LIU Li, LIU Zhi-min
2020, 36(2):  220-226.  doi:10.19741/j.issn.1673-4831.2019.0542
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The estimation of grassland biomass carbon is often based on large-scale spatial sampling, ignoring the community composition and spatial difference of grassland, which may affect the accuracy of assessment results. The object of this research is to reveal the above- and below-ground biomass carbon allocation pattern on community level based on the aboveground biomass (AGB) and belowground biomass (BGB). The results indicate that:(1) The temperate desert steppe contributed 120.44 Tg (1 Tg=1012 g) biomass within an area of 35.18×106 hm2. 15.67 and 104.78 Tg were stored in AGB and BGB, respectively. (2) The average biomass carbon density was 406.75 g·m-2. Nitraria tangutorum community had the highest belowground biomass carbon (BGC)[(921.58±354.29) g·m-2], while there were no significant differences in aboveground biomass carbon (AGC) (P>0.05) among communities. (3) The root:shoot ratio in temperate steppe was 4.79, while in temperate desert steppe was 6.69. (4) Distribution of BGC was divided into two types:"exponential function type" and "quadratic function type". Communities of Allium polyrhizum, Reaumuria songarica, Sarcozygium xanthoxylon, Stipa tianschanica, Stipa glareosa, Artemisia frigida, Caragana intermedia and Caragana microphylla were "exponential function type" (BGC were mainly distributed in 0-10 cm depth; the fitting curve is exponential function). Communities of Nitraria tangutorum and Haloxylon ammodendron were "quadratic function type" (BGC were mainly distributed in the depth of 0-10 and 20-40 cm; the fitting curve is quadratic function). Evaluation of grassland biomass carbon storage by different grassland communities is meaningful for understanding carbon storage dynamics and providing a theory to support natural grassland management and research in northern China.
Effects of Cyanobacterial Blooms on Nitrous Oxide Emission From Taihu Lake
CHEN Jing, LI Xing, WANG Yi-ping, CHEN Xiao-feng, YANG Liu-yan
2020, 36(2):  227-233.  doi:10.19741/j.issn.1673-4831.2019.0291
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During a cyanobacterial bloom, surface water nitrous oxide (N2O) concentrations were measured at 12 sites in Taihu Lake, including Meiliang Bay and the open area. It was found that N2O concentration at the sampling sites of Lake Taihu were significantly different. The mean N2O concentration at the estuary area was averagely around 26.8 μmol·m-3, which was much higher than those at the other sites (<11 μmol·m-3), among which the northeast area of Meiliang Bay and the open area were averagely only 4.0 μmol·m-3. N2O concentrations in the surface water were correlated with chlorophyll a (Chl-a) concentrations (P<0.05), indicating that cyanobacterial blooms might promote the production of N2O in Lake Taihu. To test the hypothesis, a microcosm simulation experiment was conducted in laboratory. With sufficient nitrate, N2O release from the treatment with a small amount of cyanobacteria added (about 80 μg·L-1 Chl-a) was significantly higher than that from the control group without cyanobacteria added (about 30 μg·L-1 Chl-a, P<0.001). However, the N2O releases decreased significantly (P<0.001) when Chl-a concentrations increased further. This suggests that when nitrogen is abundant, a certain concentration of cyanobacteria can promote N2O release, but higher concentrations might inhibit it. In an acetylene inhibition experiment, the N2O production rate increased markedly with increasing Chl-a, even with high cyanobacteria concentrations. This indicates that high cyanobacteria concentrations in microcosms did not inhibit N2O production, but rather accelerated the reduction process of N2O to N2.
Effects of Disturbance Modes on Lacustrine Nutrients and Algal Biomass: An Experiment Study
ZHAO Jia-min, TIAN Wei, YANG Gui-jun, ZHANG Hong-liang, TANG Xiang-ming
2020, 36(2):  234-241.  doi:10.19741/j.issn.1673-4831.2019.0498
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To understand the effect of disturbance modes on lacustrine nutrients and cyanobacterial blooms, an indoor simulative mixing experiment was conducted in July 2018 for 19 days. Results show that TN, TP and TDP concentrations decreased in the control group, intermittent disturbance group and continuous disturbance group. The concentrations of TN in the intermittent disturbance group showed the sharpest decline, and concentrations of TN differed significantly (P<0.05) among the three treatments. During the period of the experiment, the highest, medium and lowest mean values of TDP concentration were observed in the intermittent disturbance group, the control group and the continuous disturbance group, respectively. There were significant differences in TDP concentration between the intermittent disturbance and continuous disturbance groups (P<0.05). At the end of the experiment, the concentrations of Chl-a in the control group, intermittent disturbance group and continuous disturbance group were 251.8, 136.2 and 327.6 μg·L-1, respectively. Concentrations of Chl-a differed significantly (P<0.05) among the three treatments. These results indicate that intermittent disturbance was conducive to nitrogen removal from lakes. Continuous disturbance at appropriate intensities may significantly increase Chl-a concentrations, thus benefitting algal accumulation and cyanobacterial blooms.
Polluting Characteristics and Ecological Risk Assessment of Heavy Metals in Cultivated Land Around a Mining Area in Northern Hebei Province
SUN De-yao, XUE Zhong-cai, HAN Xing, ZHAO Ying-fan, SUN WEI-yue, ZHANG Ke
2020, 36(2):  242-249.  doi:10.19741/j.issn.1673-4831.2019.0396
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To investigate the polluting characteristics and to assess ecological risk of heavy metals in cultivated land around a mining area in northern Hebei Province, the concentrations of Hg, As, Cd, Pb, Cu, Zn, Ni and Cr in the 25 top soil (0-20 cm) samples were determined and the spatial distribution of the heavy metals in the cultivated land was analyzed based on geostatistical analysis. The potential ecological risks were assessed by the single factor (Pi), Nemerow index method (PN), and potential ecological risk index (IR) and the main sources of heavy metals were discussed according to the multivariate statistical analysis. The results show that the average concentrations of all heavy metals except As in the soil exceeded the background values of soil, meanwhile the Hg, Pb, Zn and Ni concentrations did not exceed the national agricultural land soil pollution risk screening value, and met the national pollution risk screening standards,meanwhile the over standard rates of Cd, Cu and Cr contents were 33%, 46% and 8%, respectively. The higher concentrations of Zn, Hg, Cd, Pb, Cu and As were mainly concentrated in north and south-central parts of the research area, and the higher concentrations of Cr and Ni were mainly concentrated in north and central parts. The single factor assessment results indicate that the degree of heavy mental pollution was in the order of Cd > Pb > Cu > Hg > Cr > Ni > Zn > As and it had some potential ecological risks in the cultivated land, according to the Nemero comprehensive pollution index and potential ecological risk index. Cd and Hg in the soil were the main sources of pollution. The sources of As, Hg, Cd, Zn, Pb and Cu were mainly affected by anthropogenic pollution factors, whereas Cr and Ni were mainly affected by soil parent material and geological activities.
Isolation of Norfloxacin Resistant Bacteria and Analysis of Its Antibiotic Resistance Genes From the Wastewater Treatment System of a Livestock Farm
ZHAO Han-bin, CHEN Xin, WU Guang-zhe, ZHOU Chun-chun, LIU Li-li
2020, 36(2):  250-256.  doi:10.19741/j.issn.1673-4831.2019.0343
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The accumulation and diffusion of antibiotic resistant bacteria and resistance genes in wastewater treatment systems of livestock farm poses potential hazards to ecological environment and human health. Therefore, it is necessary to investigate the types of resistant bacteria, resistance genes and genetic characteristics in the livestock wastewater treatment systems. In this study, a norfloxacin-resistant strain TY-1 was isolated from the sludge, which was collected from the secondary sedimentation tank of a meat goose farm in Jiangsu Province. The strain TY-1 was identified as Sphingomonas sp., according to the results of morphological, physiological and biochemical characteristics, and 16S rRNA gene sequence analysis. Based on the whole genome annotation of Sphingomonas sp., it was found that strain TY-1 had multiple antibiotic resistance genes (ARGs), including ABC transporter, MFS transporter and cytochrome P450 dehydrogenase. According to the results of gene cluster analysis, these ARGs were ubiquitous in genus of Sphingomonas. This study can provide a useful reference for the ecological risk assessment of pathogenic microorganisms containing antibiotic resistance genes in the wastewater treatment systems of livestock farm.
Degradation of Benzonitrile and Benzoic Acid by Actinomycetes Streptomyces canus CGMCC 13662
GUO Ling, FANG Wen-wan, GE Feng, DAI Yi-jun
2020, 36(2):  257-264.  doi:10.19741/j.issn.1673-4831.2018.0854
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The nitrile-degrading actinomycetes Streptomyces canus CGMCC 13662 was used to study the degradation of benzonitrile and benzoic acid. Growing S. canus cells degraded 0.5 g·L-1 benzonitrile completely within 120 h, with the final metabolite being benzamide; the resting cells could completely degrade benzonitrile within 24 h and benzamide and benzoic acid were no longer present by the end of the assay. The actinomycetes simultaneously degraded catechol and protocatechuic acid, indicating that the metabolic pathway of benzoic acid was via the catechol and protocatechuic acid pathway. The amount of benzoic acid produced by CoCl2-induced actinomycetes after 8 h of benzonitrile metabolism was 6-fold lower than the control without cobalt, which indicated that benzonitrile degraded via the NHase/amidase and nitrilase pathways and CoCl2 could regulate the benzonitrile metabolic flux between them. The degradation rate of benzonitrile decreased under acidic conditions, while benzamide degradation was sensitive to the pH of the resting cell solutions and the maximum benzamide degradation was at pH 7.5. Malate was the optimal co-substrate for benzonitrile degradation, leading to a decrease in the half-life of benzonitrile degradation from 5.40 to 3.80 h compared with degradation without the co-substrate. Glucose and sucrose had no effect on benzonitrile degradation as co-substrates, while they inhibited the further degradation of benzamide. This study provides a theoretical basis for eliminating residues of benzonitrile and intermediate metabolic pollutants in the environment and exploring the metabolic mechanism of benzonitrile.
Effect of Activation Temperature on the Properties and Adsorption Performance of Eucalyptus robusta Based Activated Carbon
LIU Zheng, WEI Meng-qin, DU Yue-ying, FENG Qing-ge, ZHANG Xiao-juan, SUN Xiang, MA Da-chao
2020, 36(2):  265-271.  doi:10.19741/j.issn.1673-4831.2019.0442
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Activated carbons were prepared from fast-growing Eucalyptus robusta bark by potassium pyrophosphate activation. The effects of different dosage ratio (activating agent/raw material), activation temperature, heating rate and activation time were investigated by response surface method. The physicochemical properties of activated carbon in various carbonization temperature preparation were characterized by X-ray diffraction (XRD), surface area and pore size analyzer. Fourier transform infrared spectroscopy (FT-IR), laser-Raman spectrum(LRS) and the adsorption performance of fast-growing Eucalyptus robusta bark activated carbon on iodine and tetracycline hydrochloride were analyzed. It was found that the optimal process conditions were obtained by the quadratic polynomial model as the followings:The dosage ratios was 0.9. The temperature was 710℃. The heating rate was 30℃·min-1. The activation time was 30 min. The specific surface area of the obtained activated carbon was 611.373 m2·g-1. The pore volume was 0.537 9 cm3·g-1. The average pore diameter was 3.52 nm. The adsorption value of activated carbon for iodine was 1 225 mg·g-1. The adsorption of tetracycline hydrochloride by fast-growing Eucalyptus robusta bark activated carbon was controlled by pore size distribution and surface chemistry and the adsorption behavior was consistent with the Langmuir model.