Heavy metal pollution of soils and vegetables in the midstream and downstream of the Xiangjiang River, Hunan Province

A total of 219 agricultural soil and 48 vegetable samples were collected from the midstream and downstream of the Xiangjiang River（the Hengyang-Changsha section）in Hunan Province.The accumulation characteristics,spatial distribution and potential risk of heavy metals in the agricultural soils and vegetables were depicted.There are higher accumulations of heavy metals such as As,Cd,Cu,Ni,Pb and Zn in agricultural soils,and the contents of Cd（2.44 mg kg^-1 ）,Pb（65.00 mg kg^-1 ）and Zn（144.13 mg kg^-1 ）are 7.97,3.69 and 1.63 times the corresponding background contents in soils of Hunan Province,respectively. 13.2%of As,68.5%of Cd,2.7%of Cu,2.7%of Ni,8.7%of Pb and 15.1%of Zn in soil samples from the investigated sites exceeded the maximum allowable heavy metal contents in the China Environmental Quality Standard for Soils（GB15618-1995,Grade Ⅱ）.The pollution characteristics of multi-metals in soils are mainly due to Cd.The contents of As,Cd,Cu,Pb and Zn in vegetable soils are significantly higher than the contents in paddy soils.95.8%, 68.8%,10.4%and 95.8%of vegetable samples exceeded the Maximum Levels of Contaminants in Foods（GB2762-2005）for As,Cd,Ni and Pb concentrations,respectively.There are significantly positive correlations between the concentrations of Cd,Pb and Zn in vegetables and the concentrations in the corresponding vegetable soils（p〈0.01）.It is very necessary to focus on the potential risk of heavy metals for food safety and human health in agricultural soils and vegetables in the midstream and downstream of the Xiangjiang River,Hunan Province of China.

Spatial distribution and environmental characterization of sediment-associated metals from middle-downstream of Xiangjiang River,southern China

The contamination and environmental risk assessment of the toxic elements in sediments from the middle-downstream (Zhuzhou-Changsha section) of the Xiangjiang River in Hunan Province of China were studied. The results show that As, Cd, Pb and Zn are major contaminants in sediments, and average concentrations of these elements significantly exceed both the Control Standards for Pollutants in Sludge of China (GB4284-84) for agricultural use in acidic soils and the effect range median (ERM) values. The average concentrations of As, Cd and Pb in the river water slightly exceed the limit of Surface Water Environment Quality Standard (GB3838-2002). The concentrations of As and Cr in depth profiles extensively change, but slight changes are observed in Pb and Zn. Cd and Zn in most sediment samples can easily enter the food-chain and bring possible ecotoxicological risk to organisms living in sediments according to the risk assessment code.

Surface water quality and potential health risk assessments in Changsha-Zhuzhou-Xiangtan section of Xiangjiang River, China

The Changsha-Xiangtan-Zhuzhou City Group is a heavy industrial district and accepted as the serious pollution area in the Xiangjiang River basin.In this study,7 metals(Pb,Hg,Cd,As,Zn,Cu and Se)and the river water quality parameters including pH,dissolved oxygen(DO),Escherichia coli(E.coli),potassium permanganate index(CODMn),dichromate oxidizability(CODCr),five-day biochemical oxygen demand(BOD5),ammonia nitrogen(NH4+-N),total nitrogen(TN),total phosphorus(TP)and fluoride(F)in 18 sampling sites of the Changsha-Xiangtan-Zhuzhou section are monthly monitored in 2016,which is the year to step into the second stage of the“Xiangjiang River Heavy Metal Pollution Control Implementation Plan”.It is found that E.coli,TN and TP are the main pollutants in the Changsha-Zhuzhou-Xiangtan section,and the pollution of heavy metal is not serious but As with potential risk to local people especially children should be concerned.In addition,Xiangtan city is mainly featured with heavy metal pollution,while Zhuzhou and Changsha city are both featured with other pollutants from municipal domestic sewage.

Analysis and prediction of reference evapotranspiration with climate change in Xiangjiang River Basin, China

Reference evapotranspiration （ETo） is often used to estimate actual evapotranspiration in water balance studies. In this study, the present and future spatial distributions and temporal trends of ETo in the Xiangjiang River Basin （XJRB） in China were analyzed. ETo during the period from 1961 to 2010 was calculated with historical meteorological data using the FAO Penman-Monteith （FAO P-M） method, while ETo during the period from 2011 to 2100 was downscaled from the Coupled Model Intercomparison Project Phase 5 （CMIP5） outputs under two emission scenarios, representative concentration pathway 4.5 and representative concentration pathway 8.5 （RCP45 and RCP85）, using the statistical downscaling model （SDSM）. The spatial distribution and temporal trend of ETo were interpreted with the inverse distance weighted （IDW） method and Mann-Kendall test method, respectively. Results show that： （1） the mean annual ETo of the XJRB is 1 006.3 mm during the period from 1961 to 2010, and the lowest and highest values are found in the northeast and northwest parts due to the high latitude and spatial distribution of climatic factors, respectively; （2） the SDSM performs well in simulating the present ETo and can be used to predict the future ETo in the XJRB; and （3） CMIP5 predicts upward trends in annual ETo under the RCP45 and RCP85 scenarios during the period from 2011 to 2100. Compared with the reference period （1961-1990）, ETo increases by 9.8%, 12.6%, and 15.6% under the RCP45 scenario and 10.2%, 19.1%, and 27.3% under the RCP85 scenario during the periods from 2011 to 2040, from 2041 to 2070, and from 2071 to 2100, respectively. The predicted increasing ETo under the RCP85 scenario is greater than that under the RCP45 scenario during the period from 2011 to 2100.

Spatial matching and flow in supply and demand of water provision services: A case study in Xiangjiang River Basin

Global climate change and increased human consumption have aggravated the uneven spatiotemporal distribution of watershed water resources, affecting the water provision supply and demand state. However, this problem has often been ignored. The present study used the Xiangjiang River basin(XRB) as the study area, and the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST) model, demand quantification model,supply–demand ratio, and water flow formula were applied to explore the spatial heterogeneity, flow, and equilibrium between water supply and demand. The results demonstrated significant spatial heterogeneity in the upstream, midstream, and downstream regions.The areas of water shortage were mainly located the downstream of the Changsha–Zhuzhou–Xiangtan urban agglomeration, and the Hengyang basin was the most scarcity area. Affected by terrain gradients and human needs, water flow varied from-16.33 × 10^(8) m^(3) to 13.69 × 10^(8) m^(3)from the upstream to the downstream area, which provided a possibility to reduce spatial heterogeneity. In the future, measures such as strengthening water resource system control,sponge city construction, and dynamic monitoring technology should be taken to balance the supply and demand of water in different river sections of the basin. This study can provide references for regulating water resources allocation in different reaches of the basin.

Assessment of heavy metals in sediment cores from Xiangjiang River,Chang-Zhu-Tan region,Hunan Province,China

Samples were collected from two core sediments(C1 and C2) of Xiangjiang River,Chang-Zhu-Tan region,Hunan Province,China.The heavy metal contents are relatively higher,especially for the surface or near the surface layers.The calculated anthropogenic factor values indicate that all the heavy metals except for Cr in the core samples are enriched,especially for Cd,with the maximum enriching coefficients of 119.44,and 84.67 in C1 and C2,respectively.The correlation of heavy metals with sulphur indicates that they are precipitated as metal sulphides.Correlation matrix shows significant association between heavy metals and mud.Factor analysis identifies that signified anthropogenic activities affect the region of Xiangjiang River.

The Prediction Model of Heavy Metal Pollution in the Xiangjiang River Based on Matlab

[Objective] The study aimed to establish a model to predict heavy metal pollution in the Xiangjiang River （from Zhuzhou to Changsha） on the basis of Matlab. [ Methodl According to the data of heavy metal content in the Xiangjiang River （from Zhuzhou to Changsha）, we estab- lished a non-linear regression model based on Matlab to forecast the content of C,d, Pb, Cu, Zn, As and Cr in the Xiangjiang River. E Result] Verifi- cation showed that the prediction models had a high precision, and the spatial variation of the predicted heavy metal content was basically consistent with the actual conditions, which indicated that these models could forecast the spatial variation of heavy metal content in the Xiangjiang River （ from Zhuzhou to Changsha） well. [ Conclusion] The research could provide theoretical bases for controlling the heavy metal pollution in the Xiangjiang River.

An Evaluation of Artificial Fish Nest for Assessment Enhancement Effects of Fishery Resources of in Xiangjiang River

Artificial fish nests are set in Lukou section and Hengyang section of Xiangjiang River from March 20 to May 10, 2019. The structure of artificial fish nest is bamboo frame, with the size of 2.5 m × 5.0 m × 4 and a unit frame area of 60 m2. A total of 58,201 eggs were collected by 24 monitoring times, of which 30,441 were from Lukou and 27,760 from Hengyang. 3831 fish eggs identify 8 fish species using morphological or molecular biological methods. The results showed that the number of eggs peaked from the 8th day to the 24th day after the nest entered the water, and then decreased rapidly. There was significant negative correlation between egg number in per m2 fish nest and days of fish nest (P < 0.01). The economic benefits of artificial fish nests were RMB 11.81 million. The artificial fish nest can not only increase the population of fish, but also has significant economic benefits.

THE RESEARCH ON THE DISTRIBUTION AND FORMS OF HEAVY METALS IN THE XIANGJIANG RIVER SEDIMENTS

In this paper, the contents and various forms of Cd, Cu, Zn and Pb in the sediments of the Xiangjiang River have been investigated. The presentation of this paper focuses on the various forms and characteristics of the heavy metals in the column sediments at Xiawan Port of Zhuzhou, which has been severely polluted by a metallurgical plant.The forms of the heavy metals discussed in this paper are: The concentration of the exchangeable forms of Cd, Cu, Zn and Pb, in the forms of carbonates and Fe/ Mn oxide in water, the combination of Cu with organic matter and form, and the proportion of the residue form at each section have been studied.

Estimation of future water resources of Xiangjiang River Basin with VIC model under multiple climate scenarios

Variation trends of water resources in the Xiangjiang River Basin over the coming decades have been investigated using the variable infiltration capacity(VIC) model and 14 general circulation models'(GCMs') projections under the representative concentration pathway(RCP4.5) scenario. Results show that the Xiangjiang River Basin will probably experience temperature rises during the period from 2021 to2050, with precipitation decrease in the 2020 s and increase in the 2030 s. The VIC model performs well for monthly discharge simulations with better performance for hydrometric stations on the main stream of the Xiangjiang River than for tributary catchments. The simulated annual discharges are significantly correlated to the recorded annual discharges for all the eight selected target stations. The Xiangjiang River Basin may experience water shortages induced by climate change. Annual water resources of the Xiangjiang River Basin over the period from 2021 to 2050 are projected to decrease by 2.76% on average within the range from-7.81% to 7.40%. It is essential to consider the potential impact of climate change on water resources in future planning for sustainable utilization of water resources.

The Impacts of Regional Rainfall and Upstream Effect on Runoff of Xiangjiang River of Guizhou

Based on monthly runoff data of Xiangjiang River of Guizhou from June 2013 to June 2015 and monthly runoff data of Yachi River of Guizhou from April 2014 to May 2015,using REOF and multiple linear regression analysis,the effects of regional rainfall and monthly runoff of upstream river on monthly runoff of Xiangjiang River were studied. Seasonal temporal-spatial change of monthly runoff of Xiangjiang River and Yachi River mainly had two kinds of modalites. The first modality was artificial influence mode,which was absolutely main component of seasonal change of monthly runoff in Xiangjiang River and Yachi River,and peak appeared during August-October. Here,component of Yachi River was far larger than that of Xiangjiang River,and artificial control ability of monthly runoff in Xiangjiang River was far larger than Yachi River. The second modality was natural influence mode,and peak appeared in July. Xiangjiang River and Yachi River had similar natural influence component,and the component was only tiny part of seasonal change of monthly runoff in Xiangjiang River and Yachi River. Water gathering change of Xiangjiang River headstream showed by monthly runoff of Yachi River and the first mode of regional rainfall were main influence factors of monthly runoff of Xiangjiang River. Monthly runoff of Xiangjiang River,monthly runoff of Yachi River and the first mode of regional rainfall all had the same-phase seasonal change.

Characteristics of the phytoplankton community and bioaccumulation of heavy metals during algal blooms in Xiangjiang River (Hunan,China)

The frequency of algal blooms has increased in the mid and downstream reaches of the Xiangjiang River （Hunan, China）, one of the most heavily polluted rivers in China. We identified the bloom-forming species in a bloom that occurred mid-late September 2010. In addition, we determined the extent of metal bioaccumulation in the algae and measured the toxicity of the algae using a mouse bioassay. Water samples were collected at upstream （Yongzhou）, midstream （Hengyang）, and downstream （Zhuzhou, Xiangtan, and Changsha） sites. The dominant species was Aulacoseira granulata, formerly known as Melosira granulata. The heaviest bloom occurred at Xiangtan and Changsha, where the number ofA. granulata peaked at 1.3×10^5 filaments L-1 and chlorophyll a at 0.04 mg L-1. Concentrations of A1, Fe, and Mn were 4.4×10^3, 768.4, and 138.7 mg kg-1 dry weight in the phytoplankton. The bioaccumulation factor was 4.0×10^5, 7.7×10^5, and 3.2×10^3, respectively. The heavy metal Pb had the greatest tendency to bioaccumulate among the highly toxic heavy metals, with a concentration of 19.2 mg kg-1 dry weight and bioaccumulation factor of 9.6×10^3. The mouse bioassay suggested the bloom was toxic. The LD50 was 384 mg kg-1 and all surviving mice lost weight during the first 72 h after exposure. Our results demonstrate that blooms ofA. granulata in rivers contaminated with heavy metals pose a threat to freshwater ecosystems and human health. Thus, measures should be taken to control eutrophication and heavy metal pollution in such rivers.

Research on the ecological compensation standard of the basin pollution control project based on evolutionary game theory and by taking Xiangjiang River as a case

Ecological compensation is a new resource and environment management model.As one of the main areas for implementing ecological compensation policies,basin ecological compensation has become an important measure for encouraging basin pollution control projects and improving the quality of regional economic development.By applying the basic game analysis of evolutionary game theory and building an evolutionary game model with a“reward-punishment”mechanism,this paper compares the interest-related decision-making behaviors of the upstream and downstream stakeholders of basin ecological compensation.By using data on the water quality of Xiangjiang River Basin,this paper calculates the rewards and penalties in different intervals by building a parametric regression mathematical model and employing the local linear regression method.Results show that a decline in water quality should be fined RMB 925500 yuan,an improvement in water quality should be awarded RMB 1227800 yuan,and a deteriorating water quality should be severely fined RMB 5087600 yuan.

基于景观生态风险评价的湘江流域生态安全格局构建

[目的]进行湘江流域景观生态风险评价,构建生态安全格局,为该地区的区域生态保护修复工作的开展提供参考。[方法]从自然环境、人类社会以及景观格局三个层面选取11个指标构建湘江流域景观生态风险评价指标体系,运用空间主成分分析法对湘江流域景观生态风险进行综合评价,基于评价结果构建综合生态阻力面。结合InVEST模型、形态学空间格局分析与景观连通性分析识别生态源地,采用电路理论识别生态廊道、生态夹点及障碍点区域,构建湘江流域生态安全格局。[结果](1)人类社会对湘江流域景观生态风险影响最大。高景观生态风险在城市群及各地级市形成多个高值中心向外延伸,低景观生态风险区主要分布在东南部以及南部林地。(2)共提取出32个生态源地,面积20415.89 km^(2),占流域总面积的22%。识别出生态廊道64条,总长度共1888.25 km,确定筛选出50处生态夹点和41处生态障碍点,分别占流域总面积的0.8%和0.6%。(3)划分出生态保护区、生态改善区、生态修复区、生态关键区,并制定不同的生态保护与优化措施。[结论]合理构建生态安全格局是生态经济可持续发展的重要保障。基于湘江流域景观生态风险分析,对生态源地、生态廊道以及关键节点部分采取相对应的措施和方针进行生态修复与保护维护生态安全。

基于四维度模型的湖南省湘江流域洪涝灾害风险评估

当前极端气候事件频发,降水频次与强度剧增,致使区域洪涝风险提高。为了降低区域洪涝风险,从致灾因子危险性、孕灾环境敏感性、承灾体脆弱性和防灾减灾能力四维度分析洪涝灾害风险的形成机理,基于11项指标,综合运用ArcGIS地理信息软件与熵权法等数理统计方法客观赋权,对湖南省湘江流域的洪涝风险进行综合性评估,最终制作出区县尺度的洪涝风险分布图。结果表明:湘江流域中西部致灾因子危险性低,中游地区孕灾环境敏感性高;环长株潭地区与衡阳市的承灾体脆弱性较高,但前者凭借良好的经济基础,其防灾减灾能力相对较强;湘江流域洪涝风险分布从东北向西南呈增强趋势,高洪涝风险区位于长沙市、益阳市、衡阳市及永州市南部,不同地区洪涝风险的主导因子不同。研究结果较好地反映了多因子作用下地区洪涝风险的差异,可为区域防洪减灾提供支撑。

湘江流域化工园区土壤与地下水重金属污染特征及相关性分析

目前针对化工园区的土壤重金属污染研究较多,但对其地下水重金属污染研究较少,特别是将土壤与地下水重金属污染相关联的研究更是寥寥无几。本论文针对湖南省湘江流域化工园区土壤与地下水中铅、铊、镉、汞、砷5种重金属污染特征,运用单因子指数法和内梅罗综合污染指数法进行评价分析,对地下水污染因子进行评价与相关性分析,找到化工园区土壤与地下水重金属污染相关性。因此,以某一区域为代表将土壤与地下水重金属污染进行相关性分析,可为化工园区的土壤与地下水重金属污染的监管与防治提供重要指导作用。

湘赣流域旅游产业效率的时空演化与比较——基于“十二五”和“十三五”时期的数据

旅游效率是衡量旅游业高质量发展的重要指标之一。通过建立五个要素层、六个指标的投入体系和两个要素层、四个指标的产出体系,运用DEA-MI模型,探讨赣江流域和湘江流域在“十二五”和“十三五”时期旅游业的时空变化,可以为流域旅游效率的发展提供参考。在时序演进上,两江流域旅游效率呈“M”型走向趋势;“十二五”时期赣江流域依靠优势资源取胜,“十三五”时期湘江流域依靠“头部文化”转败为胜;其中技术水平的发展速度是影响旅游业发展的主导因素。在空间分布上,两江流域标准差椭圆始终呈现“东北—西南”方向;赣江流域的空间格局变动主要体现在“十三五”时期,湘江流域则主要集中在“十二五”时期;长、潭、永包围圈的发展模式是湘江流域旅游业成功的关键。

湘江流域制造业企业时空演化特征及影响因素

湘江流域作为国家重要先进制造业高地的核心区域和国家流域环境污染综合治理的重点试验区,如何促进其制造业绿色高质量可持续发展是值得探讨的重要议题。本文运用空间统计分析和地理探测器等方法探析了湘江流域1978—2021年制造业企业时空演化特征及影响因素,结果表明:(1)流域制造业企业总量和增量均呈增长趋势,具有明显的阶段性特征;结构则由污染型为主转型为以清洁型为主,但污染型企业仍占一定比重。(2)传统机械制造业逐步向高附加值、低污染的装备制造业演进,产业升级态势明显,但流域制造业结构整体仍以重化工业为主,并呈下游“重”于中上游的区段差异特征。(3)流域制造业企业集聚度提升,集聚程度沿江自下游向上游递减,空间分布态势由以长株潭三市中心城区为核心,衡阳市为次级增长极的“一核一极”格局演进为以长株潭三市中心城区为核心,以核心边缘“宁乡—湘乡—醴陵—浏阳—湘阴”连接带为环带,以邵阳、衡阳为次级增长极的“一核一带两极”格局。(4)基于“污染—要素”密集程度划分的6大类型制造业企业多以下游长株潭都市圈为核心,呈资本和技术密集型往核心集聚、劳动和污染密集型往环带和中上游扩散集聚的趋势。(5)政策扶持和创新能力对湘江流域制造业企业快速增长阶段布局影响较强,生产成本、自然条件和城市功能次之,社会经济因素影响较弱。但受产业特性影响,不同因子对不同类型制造业的影响程度存在明显差异。

湘江流域县域城镇化水平时空演变特征及驱动力

县域是城乡融合发展和乡村振兴的重要载体,县域城镇化的有序发展和优化布局,对于推进城乡要素平等交换、产业结构优化调整、资源与市场优化配置具有重要战略意义。运用熵值法综合评价湘江流域2005—2020年城镇化水平,分析其城镇化时空演变特征和演变规律,并基于驱动力因子分析,深入探究湘江流域县域城镇化的动力机制。结果表明:①从时序变化来看,湘江流域县域城镇化发展水平总体呈上升趋势,各县差距不断缩小;②从空间变化来看,直至2020年湘江流域县域城镇化空间布局呈现出“南北双核”的特征;③从时空分异来看,湘江流域城镇化的发展水平呈现明显的中心—外围结构,分布重心朝东北方向移动,并且近年来其空间分布呈集聚态势;④从空间关联来看,湘江流域县域整体在空间分布上呈显著正相关,且关联性较强,局部地区的空间集聚程度呈现上升的趋势,中上游地区的集聚程度明显高于下游地区;⑤从驱动力角度分析,城镇人口和社会消费品零售总额对湘江流域县域城镇化发展驱动作用最强。

湘江流域农村居民点时空演变特征及影响因素研究

[目的]探究多因素驱动下湘江流域农村居民点空间格局的形成过程,为农村土地资源配置优化研究提供理论依据,并为村庄规划与建设提供科学指导。[方法]借助景观格局指数、核密度分析、空间自相关分析以及时空地理加权回归模型探究湘江流域2000—2020年农村居民点时空演变特征及影响因素。[结果](1)湘江流域农村居民点主要集中在长株潭和衡永郴周边地区,其余区域分布较少,主要呈现“平原密集,山地稀疏”的特征。(2)湘江流域农村居民点用地增长明显,其破碎化速度有所减缓,形状规则程度有所提升,且呈现出显著的集聚趋势。(3)农村居民点的数量与面积在空间上的集聚特征较为相似,高—高集聚类型与低—低集聚类型的空间分布位置相对稳定,但低—低集聚类型逐渐缩减。平均形状指数的空间集聚特征表现为高—低集聚范围不断扩大,集聚特征明显增强,而低—低集聚特征有所减弱。(4)各因素对不同地区农村居民点的影响程度差异逐渐缩小,而农作物播种面积始终是影响农村居民点分布的主导因素。[结论]在多重因素的共同影响下,湘江流域农村居民点用地布局与结构形态不断优化,人居环境得到明显改善,建议发展非农经济的同时重视农业发展以及农村建设。