Eco-environment range in the source regions of the Yangtze and Yellow rivers

Based on geographical and hydrological extents delimited, four principles are identified, as the bases for delineating the ranges of the source regions of the Yangtze and Yellow rivers in the paper. According to the comprehensive analysis of topographical characteristics, climate conditions, vegetation distribution and hydrological features, the source region ranges for eco-environmental study are defined. The eastern boundary point is Dari hydrological station in the upper reach of the Yellow River. The watershed above Dari hydrological station is the source region of the Yellow River which drains an area of 4.49×10 4 km 2 . Natural environment is characterized by the major topographical types of plateau lakes and marshland, gentle landforms, alpine cold semi-arid climate, and steppe and meadow vegetation in the source region of the Yellow River. The eastern boundary point is the convergent site of the Nieqiaqu and the Tongtian River in the upstream of the Yangtze River. The watershed above the convergent site is the source region of the Yangtze River, with a watershed area of 12.24×10 4 km 2 . Hills and alpine plain topography, gentle terrain, alpine cold arid and semi-arid climate, and alpine cold grassland and meadow are natural conditions in the source region of the Yangtze River.

The Impacts of Permafrost Change on NPP and Implications:A Case of the Source Regions of Yangtze and Yellow Rivers

This paper studies the relationship between net primary productivity (NPP) and annual average air temperature (GT) at 0cm above ground in permafrost regions by using revised Chikugo NPP model,cubic spline interpolating functions,and non-linear regression methods.The source regions of the Yangtze and Yellow Rivers were selected as the research areas.Results illustrate that:(1) There is significant non-linear relationship between NPP and GT in various typical years;(2) The maximum value of NPP is 6.17,5.87,7.73,and 5.41 DM·t·hm-2 ·a-1 respectively,and the corresponding GT is 7.1,10.0,21.2,and 8.9 o C respectively in 1980,1990,2000 and 2007;(3) In 1980,the sensitivity of NPP to GT is higher than in 1990,2000 and 2007.This tendency shows that the NPP presents change from fluctuation to an adaptation process over time;(4) During 1980～2007,the accumulated NPP was reduced to 8.05,and the corresponding carrying capacity of theoretical livestock reduced by 11%;(5) The shape of the demonstration region of ecological compensation system,livelihood support system,and science appraisal system in the source regions of Yangtze and Yellow Rivers are an important research for increasing the adaptation capacity and balancing protection and development.

Adaptation Management of Mountain Tourism Service: The Case of the Source Regions of the Yangtze and Yellow River

Mountain areas are often rich in ecological diversity and recreational opportunities. Mountain tourism is thought to be an effective and important means for maintaining and expanding rural economies and, thus, improving the living conditions of rural societies. As mountain tourism service research is a professional field with several disciplines involved, a multi-disciplinary management pIatform is needed and it facilitates participation in sustainable mountain development by diverse stakeholders. With the source regions of the Yangtze and the Yellow River as a case study, this paper presents a conceptual framework for an adaptation management of mountain tourism services according to technical, policy, social and economic dimensions. The framework is based on a vulnerability assessment of mountain ecosystems, and can serve as a reference for the development of tourism service in other mountain areas.

Role of permafrost in resilience of social-ecological system and its spatio-temporal dynamics in the source regions of Yangtze and Yellow Rivers

Permafrost is one of the key components of terrestrial ecosystem in cold regions. In the context of climate change, few studies have investigated resilience of social ecological system(SER) from the perspective of permafrost that restricts the hydrothermal condition of alpine grassland ecosystem. In this paper, based on the structural dynamics, we developed the numerical model for the SER in the permafrost regions of the source of Yangtze and Yellow Rivers, analyzed the spatial-temporal characteristics and sensitivity of the SER, and estimated the effect of permafrost change on the SER. The results indicate that: 1) the SER has an increasing trend, especially after 1997, which is the joint effect of precipitation, temperature, NPP and ecological conservation projects; 2) the SER shows the spatial feature of high in southeast and low in northwest,which is consistent with the variation trends of high southeast and low northwest for the precipitation, temperature and NPP, and low southeast and high northwest for the altitude; 3) the high sensitive regions of SER to the permafrost change have gradually transited from the island distribution to zonal and planar distribution since 1980, moreover, the sensitive degree has gradually reduced; relatively, the sensitivity has high value in the north and south, and low value in the south and east; 4) the thickness of permafrost active layer shows a highly negative correlation with the SER. The contribution rate of permafrost change to the SER is-4.3%, that is, once the thickness of permafrost active layer increases 1 unit, the SER would decrease 0.04 units.

Changes in stress within grassland ecosystems in the three counties of the source regions of the Yangtze and Yellow Rivers

Based on a database of more than 40 years of second production process and energy flow records for Maduo,Qumalai and Yushu counties,a dynamic model of the stress within grassland ecosys-tems was established using a nonlinear regression method for this source regions of the Yangtze and Yel-low Rivers.The results show that dynamic curves of stress within grassland ecosystems in the three coun-ties were in the shape of an inverted 'U' during the period 1965-2007.It also revealed that the variation in actual amount of livestock inventories reflected the general trends of the stress within the grassland eco-systems in the source regions,although there were many other factors for the increase or reduction in grassland ecosystem stress.

Impacts of climate change on glacial water resources and hydrological cycles in the Yangtze River source region,the Qinghai-Tibetan Plateau,China:A Progress Report

The Yangtze River Source Region has an area of 137,704 km2.Its mean annual runoff of 12.52 billion m3,which was recorded by the Chumda Hydrological Station in 1961–2000,accounts for only 0.13 percent of the Yangtze River's total annual streamflow.The extensive rivers,lakes,wetlands,glaciers,snow fields,and permafrost of the Yangtze River Source Region,as well as the region's vast alpine grasslands,play a critical role in storing and regulating the flow of water not only in the upper Yangtze River watershed of Qinghai,Sichuan,the Tibet Autonomous Region (TAR) (Tibet) and Yunnan,but also throughout the entire lower Yangtze River basin.Climate change has been the dominant factor in recent fluctuation in the volume of the Yangtze River Source Region's glacier resources.The Chumda Hydrological Station on the lower Tongtian River has registered a mean annual glacial meltwater of 1.13 billion m3 for the period 1961–2000,makes up 9 percent of the total annual runoff.Glacial meltwater makes up a significant percentage of streamflow in the Yangtze River Source Region,the major rivers of the upper Yangtze River Source Region:the Togto,Dam Chu,Garchu,and Bi Chu (Bu Chu) rivers all originate at large glaciers along the Tanggula Range.Glaciers in the Yangtze River Source Region are typical continental-type glaciers with most glacial meltwater flow occurring June–August;the close correlation between June–August river flows and temperature illustrates the important role of glacial meltwater in feeding rivers.Glaciers in the source region have undergone a long period of rapid ablation beginning in 1993.Examination of flow and temperature data for the 1961–2000 period shows that the annual melting period for glacial ice,snow,and frozen ground in the Yangtze River Source Region now begins earlier because of increasing spring temperatures,resulting in the reduction of summer flood season peak runoffs;meanwhile,increased rates of glacier ablation have resulted in more uneven annual distribution of runoff in the source region.The annual glacial meltwater runoff in the Yangtze River Source Region is projected to increase by 28.5 percent by 2050 over its 1970 value with the projected temperature increase of 2℃ and a precipitation increase of 29 mm.As a critical source of surface water for agriculture on the eastern Qinghai-Tibet Plateau and beyond,the mass retreat of glaciers in the Yangtze River Source Region will have enormous negative impacts on farming and livestock-raising ac-tivities in upper Yangtze River watershed,as well as on the viability of present ecosystems and even socioeconomic development in the upper Yangtze River Basin.

Vegetation Index Reconstruction and Linkage with Drought for the Source Region of the Yangtze River Based on Tree-ring Data

Variations in vegetation are closely related to climate change, but understanding of their characteristics and causes remains limited. As a typical semi-humid and semi-arid cold plateau region, it is important to understand the knowledge of long term Normalized Difference Vegetation Index(NDVI) variations and find the potential causes in the source region of the Yangtze River. Based on four tree-ring width chronologies, the regional mean NDVI for July and August spanning the period 1665–2013 was reconstructed using a regression model, and it explained 43.9% of the total variance during the period 1981–2013. In decadal, the reconstructed NDVI showed eight growth stages(1754–1764, 1766–1783, 1794–1811, 1828–1838, 1843–1855, 1862–1873, 1897–1909, and 1932–1945)and four degradation stages(1679–1698, 1726–1753, 1910–1923, and 1988–2000). And based on wavelet analysis, significant cycles of2–3 yr and 3–8 yr were identified. In additional, there was a significant positive correlation between the NDVI and the Palmer Drought Severity Index(PDSI) during the past 349 yr, and they were mainly in phase. However, according to the results of correlation analysis between different grades of drought/wet and NDVI, there was significant asymmetry in extreme drought years and extreme wet years. In extreme drought years, NDVI was positively correlated with PDSI, and in extreme wet years they were negatively correlated.

Geochemistry and geological significance of the Upper Paleozoic and Mesozoic source rocks in the Lower Yangtze region

The Lower Yangtze region is one of the important marine sedimentation areas of oil and gas distribution in southern China,for its favorable source rocks,reservoirs and covers.However,the intense tectonic movements and complex hydrocarbon generation process made it highly impossible to form large-sized oil and gas reservoirs.So it was divided to different hydrocarbon-bearing preservation units in oil-gas exploration.Recent study shows that the Permian and Lower Triassic source rocks in the Lower Yangtze region are complicated in lithology.The hydrocarbon generation potential of limestone there is low while argillaceous source rocks are overall of high abundance with excellent organic types,now in the process of hydrocarbon generation,so differences in high maturity influence the evaluation of organic matter abundance and type.Biomarker characteristics indicate a reductive environment.n-alkanes are marked by a single peak,with no odd-even predominance.The composition and distribution of the carbon numbers of n-alkanes,and the high abundance of long-chain tricyclic terpanes are indicative of marine sedi-mentation.The high contents of pregnane,homopregnane,rearranged hopane suggest that the source rocks are of high maturity.There is a good linear correlation between methylphenanthrene index and vitrinite reflectance.The correlation of oil-source rocks indicated that the oil of Well HT-3 may come from the Permian Longtan Formation in the Huangqiao area,the oil of Wells Rong-2 and Juping-1 came from the Lower Triassic Qinglong Formation in the Jurong area.The exploration here is promising in those different source rocks which all have great potential in hy-drocarbon generating,and oil and gas were produced in the late stage of hydrocarbon generation.

Variation and relationship between soil moisture and environmental factors in the source region of the Yangtze River from 2005 to 2016

This study analyzed soil moisture,soil erosion,and vegetation in the source region of the Yangtze River from 2005 to 2016.We found that soil moisture showed an increasing trend from 2005 to 2009 but decreased from 2009 to 2016.The surface soil moisture was severely affected by seasonal changes in the source region of the Yangtze River,especially in the soil from 0 to 40 cm.However,seasonal variation of soil moisture deeper than 40 cm was different from that in the upper layer.Soil moisture below 40 cm wasn't affected by the seasonal variation.Soil moisture from 0 to 50 cm and the average thickness of wind deposition showed a positive correlation in the study area from 2005 to 2016.For environmental protection in the source region of the Yangtze River,wind deposition played a role in water retention.Similarly,a positive correlation also existed between the average thickness of wind erosion and soil moisture.Deep-soil moisture was the key factor for vegetation structure on the Qinghai?Tibet Plateau.The results are also helpful for further understanding the variation of soil moisture on the Tibetan Plateau and providing a scientific basis for effectively protecting and controlling the ecological environment in the future.

Studies on eco-environmental change in source regions of the Yangtze and Yellow Rivers of China:present and future

The source regions of the Yangtze and Yellow Rivers are important in the field of eco-environmental change research in China because of its distinct alpine ecosystem and cryosphere environment. At present, there are three different concepts on the extent of source areas of the Yangtze and Yellow Rivers: hydrological, geographical, and eco-environmental. Over the past decades, annual average air temperature has warmed significantly;moreover, the temperature rise rate increases notably with increase of time of the data series. Annual precipitation has no obvious increase or decrease trend, and the climate has become warm and dry in the source regions. As a result, the cryosphere in the regions has shrunk significantly since 1960 s. A warm and dry climate and changing cryosphere together induced a substantial declination of alpine wetlands, marked decrease in river runoff, significant degradation of alpine grassland, and a reduction of engineering stability.The ecological environment, however, has a tendency for restoration in the regions because the climate has become gradually warm and wet since 2000. Thus, studies on eco-environmental change is transforming from a single element to multidisciplinary integration. Climate change-cryopshere change-physical and socioeconomic impacts/risk-adaptation constitute a chain of multidisciplinary integration research.

Arsenic distribution and source in groundwater of Yangtze River Delta economic region, China

This thesis focuses Arsenic(As) distribution and occurrence in groundwater of Yangtze River Delta economic region, East China. 2019 groundwater samples were collected to analyze 26 chemical compositions, including As. The Principal Component Analysis(PCA) was used to find out As source in groundwater. The results show that average As concentration in groundwater of this study is 9.33 μg/l, and maximum As concentration is up to 510 μg/l. The variation coefficient is 314.34%. High arsenic phreatic water(>10 μg/l) distributes along the Yangtze River and its estuary. Weak hydrodynamic conditions, wide p H value variation range and deteriorating environment are dominating factors, especially in Yangtze River Delta. The PCA suggests that arsenic in phreatic water is mainly of natural origin. Part of arsenic may directly originate from sediment organics and be related to organics decomposition.

Sinian hydrocarbon accumulation conditions and exploration potential at the northwest margin of the Yangtze region, China

Based on outcrop, drilling, logging and seismic data, the reservoir forming conditions, reservoir forming model and exploration potential of the ultra-deep Sinian Dengying Formation at the northwest margin of Yangtze craton region were examined.(1) This area is in craton rifting stage from Sinian to Early Cambrian, characterized by syn-sedimentary faults and rapid subsidence, significant sedimentary differences, and development of Dengying Formation platform margins on both sides of the rift.(2) The Sinian–Cambrian in this area has two sets of high-quality source rocks, Doushantuo Formation and Maidiping-Qiongzhusi Formation;of which, the latter has a thickness of 150–600 m and hydrocarbon generation intensity of(100-200)×10;m;/km;.(3) The mounds and shoals in the platform margin of Sinian Dengying Formation controlled by faults are thick and distributed in rows and zones;they are reformed by contemporaneous–quasi-contemporaneous and supergene karstification jointly, forming pore-type reservoirs with a thickness of 200-400 m.(4) The two sets of source rocks enter oil generation windows from Permian to Early Triassic, and the oil migrates a short distance to the lithologic traps of mounds and shoals to form a huge scale paleo-oil reservoir group;from Late Triassic to Jurassic, the oil in the paleo-oil reservoirs is cracked into gas, laying the foundation of present natural gas reservoirs.(5) The mound-shoal body at the platform margin of Dengying Formation and the two sets of high-quality source rocks combine into several types of favorable source-reservoir combinations, which, with the advantage of near-source and high-efficiency reservoir formation, and can form large lithologic gas reservoirs. The Mianyang-Jiange area is a potential large gas field with trillion cubic meters of reserves. According to seismic prediction, the Laoguanmiao structure in this area has the Deng-2 Member mound-shoal reservoir of about 1300 km^(2), making it a ultra-deep target worthy of exploration in the near future.

Response of vegetation phenology to climate factors in the source region of the Yangtze and Yellow Rivers

Exploring the impact of climate factors on vegetation phenology is crucial to understanding climate–vegetation interactions as well as carbon and water cycles in ecosystems in the context of climate change.In this article,we extracted the vegetation phenology data from 2002 to 2021 based on the dynamic threshold method in the source region of the Yangtze and Yellow Rivers.Trend and correlation analyses were used to investigate the relationship between vegetation phenology and temperature,precipitation and their spatial evolution characteristics.The results showed that:(i)From 2002 to 2021,the multi-year average start of growing season(SOS),end of growing season(EOS)and length of growing season(LOS)for plants were concentrated in May,October and 4–6 months,with a trend of 4.9 days(earlier),1.5 days(later),6.3 days/10 a(longer),respectively.(ii)For every 100 m increase in elevation,SOS,EOS and LOS were correspondingly delayed by 1.8 days,advanced by 0.8 days and shortened by 2.6 days,respectively.(iii)The impacts of temperature and precipitation on vegetation phenology varied at different stages of vegetation growth.Influencing factors of spring phenology experienced a shift from temperature to precipitation,while autumn phenology experienced precipitation followed by temperature.(iv)The climate factors in the previous period significantly affected the vegetation phenology in the study area and the spatial variability was obvious.Specifically,the temperature in April significantly affected the spring phenology and precipitation in August widely affected the autumn phenology.

Spatio-temporal changes of NDVI and its relation with climatic variables in the source regions of the Yangtze and Yellow rivers

The source regions of the Yangtze and Yellow rivers are important water conservation areas of China. In recent years, ecological deterioration trend of the source regions caused by global climate change and unreasonable resource development increased gradually. In this paper, the spatial distribution and dynamic change of vegetation cover in the source regions of the Yangtze and Yellow rivers are analyzed in recent 10 years based on 1-km resolution multi-temporal SPOTVGT-DN data from 1998 to 2007. Meanwhile, the cor- relation relationships between air temperature, precipitation, shallow ground temperature and NDVI, which is 3x3 pixel at the center of Wudaoliang, Tuotuohe, Qumalai, Maduo, and Dari meteorological stations were analyzed. The results show that the NDVI values in these two source regions are increasing in recent 10 years. Spatial distribution of NDVI which was consistent with hydrothermal condition decreased from southeast to northwest of the source regions. NDVI with a value over 0.54 was mainly distributed in the southeastern source region of the Yellow River, and most NDVI values in the northwestern source region of the Yangtze River were less than 0.22. Spatial changing trend of NDVI has great difference and most parts in the source regions of the Yangtze and Yellow rivers witnessed indistinct change. The regions with marked increasing trend were mainly distributed on the south side of the Tongtian River, some part of Keqianqu, Tongtian, Chumaer, and Tuotuo rivers in the source region of the Yangtze River and Xingsuhai, and southern Dari county in the source region of the Yellow River. The regions with very marked increasing tendency were mainly distributed on the south side of Tongtian Rriver and sporadically distributed in hinterland of the source re- gion of the Yangtze River. The north side of Tangula Range in the source region of the Yangtze River and Dari and Maduo counties in the source region of the Yellow River were areas in which NDVI changed with marked decreasing tendency. The NDVI change was positively correlated with average temperature, precipitation and shallow ground temperature. Shallow ground temperature had the greatest effect on NDVI change, and the second greatest factor influencing NDVI was average temperature. The correlation between NDVI and shallow ground temperature in the source regions of the Yangtze and Yellow rivers increased significantly with the depth of soil layer.

Glacier retreat and its effect on stream flow in the source region of the Yangtze River

There is growing concern over the effects of climate change on glacier melt and hydrology. In this article, we used two natural small-scale basins, Tuotuo River and Buqu River in the source region of the Yangtze River, China, to show the impacts of glacier melt on stream flow. Changes in the extent of glaciers and ice volume in 1970, 1992 and 2009 are evaluated using remote sensing images. Changes to the glacier surface area over the same time interval are estimated through the delineation of glacier outlines and positions using Landsat TM/ETM＋ imagery. By 2009, the glacier surface area had decreased by 20.83% and 34.81% of the 1970 values in Tuotuo River and Baqu River basins respectively. The total meltwater supply in each basin is estimated to be 2.56×10^9 m^3/yr and 1.24×10^9 m^3/yr respectively. Mass balance calculations show that glaciers in the study area suffered a constant mass loss of snow and ice, accumulatively approximately -24 m over the past 40 years. The annual and summer stream flow tended to increase in Tuotuo River basin from 1970 to 2009 while a negative trend of change was shown in Buqu River basin during 1970-1986. Glaciers became shorter, narrower and thinner under the effect of atmospheric warming. Streamflow increase has been recorded at Tuotuo River station in response to increased glacier and permafrost melt. However, streamflow decrease has been recorded at Yanshiping station on Buqu River, where glacier melt has lagged behind atmospheric warming. These results show a close but variable linkage among climate change, glacier melting and water resources in the source region of the Yangtze River.

Fluvial diversity in relation to valley setting in the source region of the Yangtze and Yellow Rivers

The spatial distribution of valley setting （laterally-unconfined, partly-confined, or confined） and fluvial morphology in the source region of the Yangtze and Yellow Rivers is contrasted and analyzed. The source region of the Yangtze River is divided into 3 broad sections （I, II and III） based on valley setting and channel gradient, with the upstream and downstream sections being characterized by confined （some reaches partly-confined） valleys while the middle section is characterized with wide and shallow, laterally-unconfined valleys. Gorges are prominent in sections I and III, while braided channel patterns dominate section II. By contrast, the source region of the Yellow River is divided into 5 broad sections （sections I-V） based on valley characteristics and channel gradient. Sections I, II and IV are alluvial reaches with mainly laterally-unconfined （some short reaches partly-confined） valleys. Sections III and V are mainly confined or partly-confined. Greater morphological diversity is evident in the source region of the Yellow River relative to the upper Yangtze River. This includes braided, anabranching, anastomosing, meandering and straight alluvial patterns, with gorges in confined reaches. The macro-relief （elevation, gradient, aspect, valley alignment and confinement） of the region, linked directly to tectonic movement of the Qinghai-Tibet Plateau, tied to climatic, hydrologic and biotic considerations, are primary controls upon the patterns of river diversity in the region.

Recent temperature increase recorded in an ice core in the source region of Yangtze River

Interests on climate change in the source region of Yangtze River have been raised since it is a region with the greatest warming over the Tibetan Plateau (TP). A 70-year history of precipitation δ^(18)O has been recovered using an ice core record retrieved in a plat portion of the firn area in the Guoqu Glacier (33°34′37.8″N, 91°10′35.3″E, 5720 m a.s.l.), Mt. Geladaindong (the source region of Yangtze River), in November, 2005. By using a significant positive relationship between ice core δ^(18)O record and summer air temperature (July to September) from the nearby meteorological stations, a history of summer air temperature has been reconstructed for the last 70 years. Summer temperature was relatively low in 1940s and high in 1950s to the middle of 1960s. The lowest temperature occurred in the middle of 1970s. Temperature was low in 1980s and dramatically increased since 1990s, keeping the trend to the begin-ning of the 21st century. The warming rate recorded in the ice core with 0.5℃/10 a since 1970s is much higher that that in the central TP and the Northern Hemisphere (NH), and it becomes 1.1℃/10 a since 1990s which is also higher than these from the central TP and the NH, reflecting an accelerated warm-ing and a more sensitive response to global warming in the high elevation region.

利用InSAR技术估计长江源冰川2000—2020年物质平衡

本文以获取近20年长江源冰川物质平衡,揭示冰川物质平衡影响因素及冰川物质流失对河流径流量影响为目标开展研究。利用InSAR技术和双站TerraSAR-X/TanDEM-X影像生成两期覆盖长江源全域冰川的DEM,分别和SRTM DEM差分,去除高程差系统误差后获取长江源地区冰川2000—2012年和2000—2020年间的高分辨率冰川厚度变化,再结合冰川密度将厚度变化转为冰川物质平衡。估计结果与区域内冰川实地物质平衡监测结果仅相差0.03 m w.e.a^(-1),表明精度较高。结果显示长江源地区冰川在2000—2012年间的物质平衡为(-0.30±0.02)m w.e.a^(-1),在2000—2020年间为(-0.45±0.04)m w.e.a^(-1),2012—2020年间冰川消融相比2000—2012年间明显加速。推测夏季气温升高和夏季降水减少是冰川加速消融的主要原因。另外,长江源地区冰川消融速度存在从东南向西北递减的趋势,分析认为这一现象与西部地区温度更低,升温更慢,冰川海拔更高,积累区面积比例更高,冰面坡度更陡有关。2000—2020年间,沱沱河流域冰川物质损失量仅占沱沱河径流量的4.4%,而沱沱河与当曲流域的冰川物质损失量之和仅占通天河径流量的2.5%,表明当前冰川物质损失对长江上游径流量的影响较小。

长江中下游粮食主产区耕地面源污染时空分异特征

为揭示长江中下游粮食主产区耕地面源污染时空规律,利用长江中下游粮食主产区58个市(州、区)统计数据,采用空间分析模型、重心模型、冷热点分析等方法分析了2009—2019年长江中下游粮食主产区耕地面源污染时空分异特征。结果表明:长江中下游流域整体以及赣湘鄂皖4省2009—2019年耕地面源污染总量和强度总体均呈现出“先升后降”的变化趋势,其中湖北省的耕地面源污染强度与总量均位于前列。2009—2019年耕地面源污染强度总体表现为“西高东低”的空间分布特征,其中江西省整体上一直保持为低污染强度,湖北省则为高污染强度聚集区。长江中下游粮食主产区耕地面源污染强度重心变化呈现出“区间震荡”的规律,且长江中下游粮食主产区耕地面源污染强度重心迁移呈现明显的阶段特征。2009—2019年长江中下游粮食主产区耕地面源污染强度呈现出明显的空间聚集态势,总体表现为“东冷西热”的空间分布格局。因此,长江流域中游段特别是湖北省和湖南省是未来进一步推进耕地面源污染防治的重点区域,要统筹好国家粮食安全和耕地生态安全双重目标。

长三角地区饮用水水源地典型重金属污染状况及环境风险评估

随着城镇化和工业化的快速发展,长江三角洲地区饮用水水源水质安全引起了社会普遍关注。其中,重金属污染是该地区饮用水安全和水生态健康的重要隐患。因此,选取长三角地区107个县级以上集中式生活饮用水水源地为研究对象,分析该地区2017—2022年6种重金属(铜、锌、铅、砷、汞、镉)的总体污染状况和时空分布特征,并开展人体健康风险和生态风险评估。结果表明:长三角地区水源地水质总体良好,6种重金属污染程度总体较低。砷、铜、锌在河流型水源地中的浓度水平均高于湖库型水源地,而镉、汞、铅在湖库型水源地则相对更高,水源地重金属浓度水平受季节变化影响不大。砷、汞的生态风险较低,锌、铅、镉处于中低风险水平,铜主要处于中风险水平,但是每年均有部分水源地出现高风险。铜、锌、铅、汞、镉不会对人体产生非致癌健康风险,但是砷可能产生潜在的非致癌风险。砷、铅的致癌风险指数为10^(-6)~10^(-4),可能具有潜在致癌风险。镉与污水排放有一定的相关性,砷的来源可能主要与自然地质等因素有关。综上,长三角地区饮用水水源地重金属污染环境风险管理的主要对象是铜、砷、铅。