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Table of Content

Volume 37 Issue 3
25 March 2021
Analysis of Prevention and Control Strategies for Invasive Alien Species in China
HU Ya-ping, ZHOU Xu, SHU Qiu-xiang, GE Xiao-min, CHEN Shui-fei, DING Hui
2021, 37(3):  273-278.  doi:10.19741/j.issn.1673-4831.2020.0089
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The issue caused by invasive alien species is a major threat to ecological security, biosafety and food security in China. A series of measures has been undertaken nationally, including laws and regulations, institutional mechanisms, control and clearance. However, several weaknesses in the prevention and control of invasive alien species have not yet been resolved, and the effectiveness of controls remains inadequate. Here, the invasive status of alien species, as well as different stakeholders and their relationship involved in invasive alien species prevention and control were analyzed. The progress and problems of the invasive alien species prevention and control systems in China were also investigated. In addition, approaches for establishing effective prevention and control have been proposed, including the development of an appropriate guiding ideology, definition of the objectives of prevention and control, establishment of a sound legal framework, improvement of systems and mechanisms for prevention and control, and implementation of comprehensive management.
Progress of Agricultural Non-point Source Pollution in Erhai Lake Basin: A Review
DUAN Si-xi, YANG Ze, LI Yan-lan, HE Bo, SHI Jian-chun, SONG Wei-zhi
2021, 37(3):  279-286.  doi:10.19741/j.issn.1673-4831.2020.0506
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The control of agricultural non-point source pollution is an unavoidable issue that must be faced in order to protect the water quality of Erhai Lake basin. The characteristics of agricultural non-point source pollution of different agricultural industries, administrative areas, farmland, river entering lake as well as an estuarine wetland in Erhai Lake basin were comprehensively analyzed based on systematic investigation. The positive effects of irrigation, drainage ditches as well as lakeside buffer zones on the agricultural non-point source pollution control in Erhai Lake basin were summarized. The main causes of agricultural non-point source pollution load in Erhai Lake basin were unreasonable fertilization and rotation pattern in garlic fields, production of large livestock such as cows, pigs and beef cattle along with the frequent change of land use. It can not only reduce the load of agricultural non-point source pollution, but also ensure the high quality and suitable yield of crops by reducing the amount of chemical fertilizer, using organic fertilizer instead of chemical fertilizer, adopting rice-Vicia fava crop rotation pattern as well as Vicia fava-garlic intercropping mode within the area. To comprehensively prevent and control agricultural non-point source pollution in Erhai Lake basin, future research should aim to investigate the impacts of rural production, the ecosystem in the lake and the breeding industry on agricultural non-point source pollution.
Comprehensive Evaluation Method and Empirical Study of Biodiversity Maintenance Function at Regional Scale
LIU Ming-hua, CHEN Yan-mei, ZOU Chang-xin, DING Jiang-hui, Lü Tian-tian, ZHANG Yang
2021, 37(3):  287-294.  doi:10.19741/j.issn.1673-4831.2020.0392
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Biodiversity is the foundation of regional sustainable development. Accurate evaluation of the spatial pattern of regional biodiversity maintenance functions is of great significance for reflecting the status, changes, and threats of regional ecosystems, as well as selecting corresponding protection strategies. Based on the regional biomass, topography, climate and land cover, a comprehensive assessment model of biodiversity maintenance functions was constructed and applied in Beijing-Tianjin-Hebei region. The results show that: (1) The model can reflect the spatial pattern of biodiversity maintenance functions in Beijing-Tianjin-Hebei region. The high-value areas were mainly concentrated in the Yanshan and Taihang mountains, while the low-value areas were mainly concentrated in the Bashang Plateau and Plain areas. The evaluation results are in line with the actual conditions of the study area. (2) There is a significant correlation between the simulation results and the investigated biodiversity of the counties as well as species diversity in natural reserves. Among the various indicators of biodiversity for counties, the correlation between species-specific and the evaluation results was the highest (r=0.699, P<0.001), followed by ecosystem type diversity (r=0.680, P<0.001), richness of rare and endangered species (r=0.571, P<0.001), richness of wild vascular plants (r=0.544, P<0.001), alien species invasion (r=-0.437, P<0.001), and richness of wild higher animals (r=0.404, P<0.001); The logarithmic correlation between species diversity in natural reserves and evaluation results is the most significant (r=0.540, P<0.001). About 70% of natural reserves were distributed in the area with extremely important or highly important biodiversity maintenance functions. The evaluation method is applicable for reflecting the function of biodiversity maintenance from the regional scale and the grid level, and for providing scientific basis for the construction of regional nature reserves and ecological restoration.
Impact of Human Activities on Yancheng Coastline and Coastal Wetlands
GUO Zi-ru, WANG Gang, WU Yu-qin, CHEN Hao, LI Yu-feng, LIU Hong-yu
2021, 37(3):  295-304.  doi:10.19741/j.issn.1673-4831.2020.0318
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Using RS (remote sensing), GIS (geographic information system) and field survey comprehensively, this study analyzed the coastline and wetland changes in Yancheng during 1987-2018. The results show that the impact of human activities on the coastal wetlands was significant. Due to human reclamation, the natural coastline had been reduced by 30.23% and the artificial coastline increased to 43.92%. The natural wetland in coastal areas are reduced by 106 751.6 hm2. In addition, the reclamation areas are mainly located in the eroded shore and the transition shore between siltation and erosion. After reclamation, the silting and eroding regulation were changed in the whole shore. The siltation accelerated at the silting shore. The erosion accelerated in the transition shore between siltation and erosion. This led to the alternate point of siltation and erosion moved southward Port construction was another important human activity, which had a serious impact on coastline characteristics and wetland area. Sheyang Port is located in the transition shore between siltation and erosion and Dafeng Port is located in the eroded shore. The natural coastline was shortened, and the proportions of artificial coastline accounted for 25.45% and 47.53% in Sheyang Port and Dafeng Port respectively. After the construction of Sheyang Port, the rate of wetland loss was 18.4 hm2·a-1, which was lower than before the construction. The wetland reduction rate of Dafeng Port was 335.3 hm2·a-1, which was nearly 5 times of that before the construction of Dafeng Port. Due to the specific pattern of siltation promotion by port construction, the spatial pattern of siltation on both sides of the port had changed periodically. It had evolved from "double arch" to "arch/S-shape" and then to "arch/slope".
Temporal and Spatial Characteristics of Soil Erosion Risk in Weihe River Basin and Its Geographical Exploration
JIA Lei, YAO Shun-bo, DENG Yuan-jie, LI Yuan-yuan, HOU Meng-yang, GONG Zhi-wen
2021, 37(3):  305-314.  doi:10.19741/j.issn.1673-4831.2020.0266
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Based on GIS and RS technology, the spatial and temporal differentiation characteristics of soil erosion risk in the Weihe River basin from 2000 to 2015 were examined by using the RUSLE model. Influencing factors of soil erosion in the river basin were investigated by using the geographical detector. Results from this study indicate that: (1) the soil erosion modulus of the Weihe River basin shown a decreased trend from 2000 to 2015; average soil erosion moduli for the four periods were 50.724, 42.270, 39.716 and 35.944 t·hm-2·a-1 in 2000, 2005, 2010 and 2015, respectively, and with the total erosion declined by 1.959×108 t. The soil erosion intensity in the majority of areas was transformed to a low level; (2) areas with a large soil erosion intensity were mainly distributed in the Loess Plateau of Longdong and the Loess Hilly area of Longzhong; areas with smaller erosion intensity were mainly distributed in the Guanzhong Plain and the Valley Plain; (3) vegetation cover, afforestation area and rainfall were the main factors affecting the spatial distribution of soil erosion risk in the basin, and the interaction of different factors enhanced the explanatory power of soil erosion risk; and (4) areas with a vegetation cover less than 0.3, rainfall between 481.27-547.75 mm, elevation between 3 282-3 874 m and slope between 20° and 25° are high-risk areas of soil erosion in the basin.
Characteristics and Potential Source Regions of Aerosol Number Concentration under Different Environment in Mountainous Areas of Fujian in Early Summer
DUAN Qing, YU Yong-cheng, WANG Xin, LIN Wen
2021, 37(3):  315-322.  doi:10.19741/j.issn.1673-4831.2020.0251
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With the development of economy globalization, rapid urbanization has led to serious effects on ecological environment, which has become a global research hotspot. To analyze aerosol number concentration under different background in mountainous areas of Fujian and the impact of urbanization, particle samples were collected in Gutian (county) of Ningde, Yushan of Nanping (clean region) and Qixingping of Fuzhou (city suburb) during June 2017 by fine dust measuring device Fidas Frog. Consequently, the results show that there were different characteristics of particle number concentrations at different observation points during the observation period: The size of particles in Gutian was mainly less than 400 nm, and the average particle number concentration was 434.37 cm-3; The average particle number concentration of Yushan as a clean region was the lowest, and the number concentration of accumulation mode (0.18-1.00 μm) particles were equivalent to coarse mode's (>1.00-20.00 μm). The average particle particle number concentration of Qixingping was the highest, and the dominant size of the particle number concentration at Qixingping was located at less than 500 nm; The particle number concentration of Gutian and Yushan were bimodal distribution, and the number concentration spectrum of Qixingping showed a single peak distribution. Through the backward trajectory clustering and the analysis of potential source weight of aerosol number concentration, it is concluded that the south area of the observation point in Gutian is the potential strong source area which is greatly affected by human activities in Gutian County; Potential source regions were located in the southwest of both Yushan and Qixingping; and the accumulation mode aerosols of Qixingping were mainly from coastal cities such as Xiamen, Quanzhou, Putian and Fuzhou.
Study on Ecological Compensation Amount and Its Spatial Pattern of Wetlands Restoration in Yancheng Rare Birds National Nature Reserve
YANG Jia-ling, ZONG Ying, LI Yu-feng, ZHOU Yi, LIU Hong-yu
2021, 37(3):  323-331.  doi:10.19741/j.issn.1673-4831.2020.0311
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In this study, the buffer zone and experimental areas of Yancheng Rare Birds National Nature Reserve was taken as the study area for the evaluation of the ecological compensation amount and the spatial distribution characteristics of returning farmlands and aquaculture ponds to wetlands (RFW and RAW) on the basis of 3S technology, market economic survey and ecological compensation adjustment coefficient. The results show that the amount of ecological compensation per unit area of RFW and RAW were 7 400-13 200 Yuan·hm-2·a-1 and 0.066 8-1.127 4 million Yuan·hm-2·a-1, respectively, with the average amount of 10 900 and 358 100 Yuan·hm-2·a-1, respectively. Among all aquaculture pond types, the amounts of compensation per unit area of shrimp, fish, crab and crab fry ponds were relatively higher than other types, with the average amount of 1.076 7 million, 0.535 7 million and 0.445 5 million Yuan·hm-2·a-1, respectively. The amount of ecological compensation per unit area of portunid (Portunus trituberculatus) and ridgetail white prawn (Exopalaemon carinicauda) ponds area in the second experimental area in the south was the lowest, with only 66 800 Yuan·hm-2·a-1. The total amount of ecological compensation was 0.04×108-87.87×108 Yuan·a-1 in the study area, of which the buffer area in the south was the highest and the central experimental area was the lowest. The total amount of ecological compensation had obvious grade difference in spatial scale, and the spatial correlation Moran' I between the whole study area and the functional areas was prominent.
Spatial-temporal Evolution Characteristics and Influencing Factors of Agricultural Resources and Environment Efficiency in the Yellow River Basin
GUO Xiao-jia, ZHOU Rong, LI Jing-zhong, LU Cheng-peng
2021, 37(3):  332-340.  doi:10.19741/j.issn.1673-4831.2020.0407
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It is of great significance to explore the efficiency of agricultural resources and environment to promote ecological protection and high-quality development of the Yellow River Basin. In this paper, by using the super-efficient SBM model and spatial measurement model, a comprehensive agricultural resource and environment efficiency evaluation index system was constructed to analyze the spatial and temporal differentiation characteristics, evolution process and influencing factors of agricultural resource efficiency in 9 provinces of the Yellow River Basin from 1990 to 2017. The result showed that: (1) During the study period, the overall agricultural resource and environment efficiency in the 9 provinces was generally low and showed an upward but slow fluctuation trend, in which Shandong and Sichuan provinces were in the leading position. (2) The spatial distribution of agricultural resources and environment efficiency in the Yellow River Basin generally showed a pattern of lower reaches > upper reaches > middle reaches. In terms of the spatial pattern evolution, the spatial differentiation characteristics were relatively obvious, showing a "dual core" pattern with Shandong and Sichuan as the cores. In terms of the upper, middle and lower reaches of the Yellow River, it presented a "central-peripheral" pattern. (3) From the analysis of influencing factors, the level of agricultural economic development, the level of agricultural production technology, and the structure of planting industry played significant roles in promoting the efficiency of agricultural resources and environment. However, some other factors including financial support policies, the level of industrialization, environmental regulations and the rate of agricultural disasters had certain hindering effect. Finally, suggestions were put forward, such as strengthen the agricultural science and technology support, enhance the agricultural ecological environment protection, and accelerate the agricultural infrastructure construction, etc.
Bird Population Dynamics during the Breeding Season in Inner Mongolia Tumuji National Nature Reserve
LIU Gang, GONG Ming-hao, LIU Wei, LI Hao, ZHANG Jian-feng, YUE Wei, WEI Xiu-hong, QIAN Ying, XIE Yong-gang, ZHANG Ju, JIAO De-yu, YI Jian-feng, ZHOU Jing-ying
2021, 37(3):  341-347.  doi:10.19741/j.issn.1673-4831.2019.0965
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Birds are important indicative organisms of habitat changes. Through continuous monitoring and analysis of birds in a given area, we can objectively understand the trend of bird species diversity. Inner Mongolia Tumuji National Nature Reserve is well known for conserving the iconic endangered species, such as great bustard (Otis tarda dybowskii)and red-crowned crane (Grus japonensis), as well as the important bird breeding area, stopover site and wintering ground in China. Due to long-term farmland reclamation and overgrazing, the grassland and wetland in this reserve had been degraded, and bird habitats had been suffered from fragmentation, which had influences on the bird population dynamics. However, the inter-annual and monthly variability of bird population dynamics is not yet clear. The aim of this study is to analyze the temporal and spatial changes of bird diversity in Tumuji Nature Reserve, and determine the dynamics of bird populations. By combining line transect and point count surveys, the birds were field monitored and surveyed during the breeding season for five consecutive years on May and June from 2015. Based on the monitoring data, the population dynamics, bird diversity and bird evenness index were analyzed in Tumuji nature reserve for the past 5 years (2015-2019). A total of 99 species of birds were detected belonging to 15 orders and 33 families, of which Anseriformes and Charadriiformes are the dominant species, and the population size of great bustard showed a spatial and temporal change. There were significant spatial differences in the number of bird species and population size. The average bird community diversity was 2.39±0.39 across all surveying sites, with wetland being higher than that in grassland, and farmland-dominated habitat diversity the lowest. The average evenness index was 0.33±0.05, and birds distribution varied among geographical sites. Conservation practice should be directed to the breeding season, and surveying intensity should focus on determining the key protection area, and ensure that the bird breeding is free from human interference. Meanwhile, it will facilitate the protection and monitoring of biodiversity, and provide scientific support for evaluating the effectiveness of protected area management and optimizing protection policies.
Exploring the Diversity of Breeding Birds in Main Urban Green Areas of Lhasa
WEI Cong, LIU Shan-si, LIU Wei, YANG Le, YI Jian-feng
2021, 37(3):  348-352.  doi:10.19741/j.issn.1673-4831.2019.0851
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The study aims to explore the diversity of breeding birds in the main urban green areas of Lhasa. The investigated composition of the bird community was collected by direct counting method from seven observation points of five urban green areas/ parks (Longwangtan Park, Potala Palace Square, Norbulingka Park, New Campus and Old Campus of Tibet University) in May and June from 2016 to 2019. 46 species (belonging to 10 orders and 24 families) were recorded. For the bird fauna, there are 39, 6 and 1 species that belong to the Palaearctic, Oriental and Cosmopolitan species respectively. For the resident type, there are 31,14 and 1 that belong to resident, summer visitor and passage migrant birds, respectively. Considering habitat and spatial distribution the bird diversity index in forest and lake areas are relatively high. The fluctuant results indicate that urbanization may have had certain impact on the diversity of bird population in urban green area of Lhasa.
Effects of Different Amount of Biochar Application and Earthworm Inoculation on Soil N2O and CO2 Emissions
LIU Jiao, NA Li-ping, ZHANG Lin, CHEN Yun-feng, SUN Fu-lai, WU Yu-peng
2021, 37(3):  353-359.  doi:10.19741/j.issn.1673-4831.2020.0470
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To investigate the interactive effects of different amount of biochar application and earthworm inoculation on soil N2O and CO2 emissions, a 50-day incubation experiment was conducted in the present study. Six treatments were arranged for the experiment: soil without earthworm and biochar (S), soil with earthworm inoculation (SE), soil with low amount of biochar addition (SL), soil with low amount of biochar addition and earthworm inoculation (SLE), soil with high amount of biochar addition (SH) and soil with high amount of biochar addition and earthworm inoculation (SHE). Results show that biochar addition led to a significant decrease of earthworm's biomass. Compared with the initial stage of incubation, earthworm's biomass decreased by 18% in SE, 26% in SLE, and 37% in SHE treatment. At the end of incubation, cumulative soil N2O emissions for SE, SLE and SHE treatments were 589.8, 538.0 and 258.3 μg·kg-1, respectively, which were significantly higher than the counterpart value of non-earthworm treatments (the cumulative N2O emission was 57.1, 34.5 and 23.4 μg·kg-1 for S, SL and SH treatments, respectively). Biochar addition depressed the earthworm induced N2O emission. In general, more the biochar was added, more the obvious effect was detected. At the end of incubation, the cumulative soil CO2 emissions were 686.1, 682.2 and 420.7 mg·kg-1 for SE, SLE and SHE treatments, respectively, which were significantly higher than the counterpart value of non-earthworm treatments (the cumulative CO2 emission were 346.9, 268.7 and 165.9 mg·kg-1 for S, SL and SH treatments, respectively). Biochar addition depressed the earthworm induced CO2 emission, but the significant difference only was observed between the high amount of biochar application and the non-biochar application treatment. Analysis of between-subjects effects show that earthworm, biochar and the interaction effect between them had significant effects on N2O and CO2 cumulative emission. Biochar application increased soil pH, but decreased soil inorganic N content. Overall, high amount of biochar application led to a higher soil pH, a lower soil inorganic N content and a negative effect on earthworms' activities, which contributed to the decreased N2O and CO2 emissions with earthworm presence.
Effect of Rice Straw Returning to Field on Ammonia Volatilization in Paddy Fields under the Integrated Rice-crayfish System
SI Guo-han, PENG Cheng-lin, YUAN Jia-fu, XIA Xian-ge, CHENG Jian-ping, XU Xiang-yu, JIA Ping-an, XIE Yuan-yuan, ZHOU Jian-xiong
2021, 37(3):  360-368.  doi:10.19741/j.issn.1673-4831.2020.0137
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The integrated rice-crayfish system is an emerging complex ecological system of planting and breeding in the middle and lower reaches of the Yangtze River in China. Based on the field experiment, the aeration methods were used to study the effects of winter flooded fallow + no straw returning (W), winter flooded fallow + straw returning (WS) and winter flooded fallow + straw returning +crayfish farming (WSC) on ammonia volatilization loss in paddy fields. The aim of this study is to provide data support for the evaluation of nitrogen loss in the integrated rice-crayfish system. The results show that the ammonia volatilization in the rice growth stage accounted for 5.84%-6.49% of the nitrogen application rate in the current season, which mainly occurred during the rice base fertilizer stage and tillering fertilizer stage, and the ammonia volatilization loss in tillering fertilizer stage accounted for the highest proportion of tillering fertilizer. Compared with the W treatment, the WS treatment increased the ammonia volatilization flux and ammonia volatilization loss during the base fertilizer stage, but the ammonia volatilization loss during the tillering and earing stages had a decreasing trend. In the case of breeding Procambarus clarkii on the basis of the WS treatment, the ammonia volatilization loss in the base fertilizer stage decreased by 15.01%, but the ammonia volatilization loss in the earing stage increased by 29.09%, and the differences reached to significant levels (P<0.05), but the total ammonia volatilization loss was not much significant different between the W and WS treatments. Ammonia volatilization flux had a very significant positive correlation with NH4+-N concentration and pH of the field surface water (P<0.01). In conclusion, although straw return to the field under the integrated rice-crayfish system did not reduce the total ammonia volatilization, the characteristics of ammonia volatilization in different fertilization stages were changed, which provided data support for optimizing fertilization mode under the integrated rice-crayfish system and reducing ammonia volatilization in the paddy fields.
Applying EEM Coupled with 2D-COS to Character Structural Composition of DOM and Its Spatial Variations in an Urban River
CUI Bing, GAO Hong-jie, ZHENG Zhao-pei, YU Hui-bin
2021, 37(3):  369-377.  doi:10.19741/j.issn.1673-4831.2020.0568
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Three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy combined with parallel factor analysis (PARAFAC) and two-dimensional correlation spectroscopy (2D-COS) was applied to characterize structural composition and changes of the dissolved organic matter (DOM) in the urban river in Shenyang City. Water samples were collected from Puhe River, where the sampling sites 1# to 3# were located in the clean region, the sampling sites 4# to 6# in the industrial region, and the sampling sites 7# to 9# in the residential area. The EEMs of DOM were measured, from which fluorescence index (FI), autochthonous index (BIX) and humification index (HIX) were deduced. Based on the analysis of FI, BIX and HIX, DOM was mainly autotrophic source, while DOM in the industrial and the residential regions were also affected by terrestrial sources, and the degree of humification was relatively weak. Using PARAFAC, the six fluorescent components were extracted, i. e. fulvic-like (C1 and C2), humic-like (C3), tryptophan-like (C4 and C6) and phenolic substances (C5), of which fulvic-like (37.91%-43.82%) and tryptophan-like (23.64%-33.60%) were the main components. Based on 2D-COS, the variation order of fulvic-like and tryptophan-like in the industrial region was tryptophan-like → fulvic-like, so was the residential region. However the change order in the clean region was opposite to the industrial and residential regions, indicating that the variations of the tryptophan-like in the former were larger than those in the latter. This indirectly verified that there was a large amount of domestic sewage and industrial wastewater entering into the river from the industrial and the residential region. Based on the principal component analysis (PCA), C1-C5 were the main potential factors affecting DOM (55.15%). The scores of the sampling sites were the highest in the industrial region, followed by the residential region and the clean region. It showes that the river sections in the industrial and the residential regions were deeply affected by human activities, while the river sections in the clean region were less affected by human activities.
Effect of pH on Nitrogen Forms and Ammonia Nitrogen Release Flux in the Bottom Muddy of Plateau Rural Ditches
GONG Yun-hui, LIU Yun-gen, WANG Yan, YANG Si-lin, LIU Peng, ZHANG Jin-long
2021, 37(3):  378-386.  doi:10.19741/j.issn.1673-4831.2020.0553
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Nitrogen release from ditch sediments in mountainous rural areas induces pollution to water environment of rural ditches, which is affected by changes in overlying water pH values. In this study, indoor simulation experiments with and without sterilization of the sediments and with pH values of the overlying water as 5.5, 7.5, 9.5, and 11.5 were conducted to analyze nitrogen transformation in sediments and ammonia nitrogen release flux at sediment-water interface in typical plateau mountainous rural ditches in the upper reaches of Dianchi Lake. The results show that: (1) Sediment nitrogen content of various forms is in the order of strong oxidant leaching nitrogen (SOEF-N) > ion exchange nitrogen (IEF-N) > weak acid leaching nitrogen (WAEF-N) > strong alkali leaching Nitrogen (SAEF-N). The IEF-N, SAEF-N and SOEF-N contents were decreased while WAEF-N content was increased with the increasing of pH. There is no significant difference between sterilization and non-sterilization of the sediments on nitrogen transformation in rural ditches at the same pH value. (2) The ammonia nitrogen concentration and release flux in the overlying water at acidic (pH=5.5) and strong alkali (pH=11.5) conditions were significantly higher than those at pH=7.5 and 9.5. The ammonia nitrogen release flux in acid and strong alkali conditions without sterilization was 8- and 6-times of that at pH=7.5, while it is 2 times of that at pH=7.5 with sterilization. (3) RDA shows that pH value was positively correlated with IEF-N while negatively correlated with SAEF-N, SOEF-N and WAEF-N under acidic conditions. There is no correlation between pH value and IEF-N, SOEF-N, SAEF-N at pH=7.5, while positively correlated with TN, WAEF-N (pH≥9.5) and negatively correlated with SAEF-N, SOEF-N, IEF-N at alkaline conditions. Besides, DO and Eh are positively correlated with TN and IEF-N. This indicates that the nitrogen release capacity of the sadiments is the strongest in the plateau and mountainous rural ditches under acidic and strong alkaline conditions, while the weakest under pH=7.5. However, under acidic and strong alkali conditions, microorganisms could increase ammonia nitrogen concentration and the flux in overlying water, which was decreased at pH=7.5 and 9.5. The results of the study can provide scientific bases for the improvement of the ecological environment management of rural ditches.
Acute Toxicity of Cu2+/Cd2+ to Maize as Related to Chemical Forms of the Metals on Whole Plant Roots
DONG Ge, XU Ren-kou
2021, 37(3):  387-393.  doi:10.19741/j.issn.1673-4831.2020.0226
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A solution culture experiment combined with measurements of root elongation, adsorption-desorption, and streaming potential, were used to evaluate the toxicity of Cu2+ and Cd2+ to maize roots as related with the chemical forms of the metals adsorbed on root surfaces. The alleviative effects of coexisting cations and organic acids on Cu2+/Cd2+ toxicity to maize as well as the related mechanisms were also investigated. The results show that the toxicity of Cu2+ to maize roots was greater than that of Cd2+ at the same concentration. This was attributed to the fact that more Cu2+ was adsorbed on the root surface as exchangeable, complexed and precipitated forms compared with Cd2+. When the concentration of Cu2+ and Cd2+ was 1 μmol·L-1, the relative root elongation rates of maize were reduced by 52.40% and 96.23%, respectively, compared with those of the control. When the metal concentration was 40 μmol·L-1, the amounts of exchangeable, complexed and precipitated Cu2+ on the root surface were 1.22, 4.36 and 2.45 times that of Cd2+, respectively. At pH 4.5, coexisting cations of Ca2+, Mg2+, K+ or NH4+ reduced the amount of heavy metals adsorbed on the root surface through competition for adsorption sites and thereby alleviating the toxicity of Cu2+ and Cd2+. Additionally, the alleviative effects of the divalent cations of Ca2+ and Mg2+ were greater than those of the monovalent cations of K+ and NH4+. Furthermore, citric acid, oxalic acid, tartaric acid, and malic acid alleviated Cu2+ and Cd2+ toxicity to maize by forming stable complexes with the cations and reducing the amount of the metals adsorbed onto the roots. The alleviating effects of the organic acids on Cu2+ and Cd2+ toxicity followed the order: oxalic acid > citrate > tartaric acid ≈ malic acid, which was consistent with the complexation ability of these organic acids. Therefore, the toxicity of heavy metals to plant roots can be effectively alleviated by reducing the adsorption quantity of their exchangeable and complexed forms on root surfaces.
Remediation of Heavy Metal Contaminated Soil by Biodegradable Chelating Agents of IDS and GLDA Washing and Their Washing Kinetics Characteristics
CHEN Chun-le, YANG Ting, ZOU Xian-mei, TIAN Tian
2021, 37(3):  394-401.  doi:10.19741/j.issn.1673-4831.2020.0439
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Batch experiments were carried out, to study the washing kinetics characteristics of heavy metals (Cd, Pb and Zn) from a contaminated soil with biodegradable chelating agents of imminodisuccinic acid (IDS) and Dl-2-(2-carboxymethyl) nitrilotriacetic acid (GLDA). The effects of washing time, concentrations and pH value of IDS and GLDA on the heavy metals removal efficiencies were also investigated. Afterwards, fractions of heavy metals in soil before and after washing were determined using the sequential extraction procedure of the optimized European Community Bureau of Reference (BCR). Results show that the removal efficiencies of Cd, Pb and Zn increased with the increasing of washing time (ranging from 5 to 720 min). Both Elovich equation and double-constant equation were suitable for describing the washing kinetic process, which suggested that the desorption of Cd, Pb and Zn from soil as a function of IDS and GLDA was regarded as the heterogeneous diffusion process. The removal efficiencies of Cd, Pb and Zn increased with the increasing of IDS and GLDA concentrations (ranging from 0 to 20 mmol·L-1), however which increased first and then decreased with the increase of the pH of IDS and GLDA solution (ranging from 3 to 10). The removal efficiencies of Cd and Pb with GLDA were greater than that of IDS, while the removal efficiencies of Zn with IDS were better than that of GLDA. Under the optimal washing conditions (10 mmol·L-1 IDS and GLDA with pH = 5 for 240 and 360 min, respectively), the removal efficiencies of Cd, Pb and Zn by IDS and GLDA were 21.88% and 66.12%, 17.47% and 22.96%, and 9.21% and 8.11%, respectively. BCR results demonstrate that the acid soluble and reducible fractions of heavy metals with high activity in soil can be effectively removed by using IDS and GLDA, respectively. Soil environmental risk induced by heavy metals could be reduced after washing with IDS and GLDA.
Spatial-temporal Evolution of Habitat Quality in the Dali Bai Autonomous Prefecture Based on the InVEST Model
GAO Qing-yan, PAN Yu-jun, LIU Hua
2021, 37(3):  402-408.  doi:10.19741/j.issn.1673-4831.2020.0654
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Mountains are important components of China's territorial space, especially due to climate change, which is impacted in both scale and degree by human activity. Mountain ecosystems are affected by both natural and human disturbances and their effects are magnified by climate change. It is important to focus on the health of mountain ecosystems due to changes in land use. Changes in the quality of mountain habitats can also reveal the fragility of mountain ecosystems and preferably provide a scientific basis for ecological restoration. In this study, GIS software was used in conjunction with the InVEST model to analyze land-use data based on 30 m resolution calculated for the period 1980-2018 to assess changes in the quality of the habitat in the Dali Bai Autonomous Prefecture. The results of the analysis show that the quality of Dali Bai Autonomous Prefecture's habitat was above 0.700 and was generally improving. However, the habitat of about 20% of the study area was of a poor or relatively poor quality; 3.298% of the area's habitat had deteriorated from relatively poor grade quality to poor grade quality; and 3.752% of the area’s habitat had deteriorated from excellent or good quality to poor or very poor grade quality. The spatial change in habitat quality was remarkble. The region that had improved was mainly distributed in the marginal mountainous areas of the prefecture, while the areas that had deteriorated were mainly distributed in the plain areas, the gentle slops along the river, and around the town of the plain areas. Measures such as promoting "Grain for Green Projects", tourism, and highland special fluit plantations, etc. would be useful for the optimization of the quality of habitats of the Daili Bai Autonomous Prefecture. Furthermore, urban development at gentle mountain slops has led to the deterioration of the quality of habitates in the study area. So that, attention should be paid to those issues to prevent a further decline in habitat quality. It is equally important to promote both the relocation of towns to higher sites and the restoration of the land space.