Caohai Wetland Research Articles

Contamination features and ecological risks of heavy metals in the farmland along shoreline of Caohai plateau wetland, China

Spatial distribution characteristics of heavy metal (Cd, Pb, Cr, Cu, Zn, and Hg) contents and their ecological risks in the farmland along the shoreline of the Caohai wetland were investigated. Incubation experiments were also conducted to characterize the emission of heavy metals across soil-water interface if the farmland was reclaimed to wetland. The results showed that spatial distribution characteristics of these heavy metal contents were significantly different. Concentrations of Cd, Zn, and Hg were higher than the corresponding geochemical background levels. Ecological risk assessment suggested that the farmland along the shoreline of Caohai wetland were characterized by non-pollution or slight pollution of Pb, Cr, and Cu, moderate pollution of Cd, slight to moderate pollution of Hg, and slight pollution of Zn. Emission rates of Cd, Zn, and Hg across soil/sediment-water interface first increased, then decreased and finally reached equilibrium after the farmland soil was submersed. The contribution-rates of Cd, Zn, and Hg transferring from sediment to overlying water were calculated to be 12.7%, 14.8%, and 10.4%, respectively. We conclude that environmental issues caused by heavy metals, especially by Cd, Zn, and Hg, in the farmland along the shoreline of the Caohai wetland should be paid great attention.

Foraging habitat selection of overwintering Black-necked Cranes in the farming area surrounding the Caohai Wetland, Guizhou Province, China

BackgroundUnderstanding how overwintering birds choose foraging habitats is very important for conservation management. The overwintering Black-necked Crane (Grus nigricollis) feeds on crop remains in farmlands; thus, reasonable conservation management of this type of farmland that surrounds wetlands is critical for the overwintering populations of the Black-necked Crane; however, it is not clear how the Black-necked Crane chooses the foraging land in the farmland.MethodsA thorough field positioning survey of all foraging sites in farmland areas around the Caohai Wetland and a sampling analysis of habitat selection by the Black-necked Crane were conducted during the winters from 2016‒2017 and 2017‒2018.ResultsMultiple factors contributed to the selection of foraging habitat in farmlands, i.e., food factors (crop remains and tillage methods) > human disturbance factors (distance to road and settlement) > topography factors (slope aspect), listed according to the strength of influence. Additionally, Black-necked Cranes tend to choose farmland sites where there was no machine tillage, the crop remains were > 500 g/m2, the distance to residences ranged from 100 to 500 m, the distance to roads ranged from 50 to 100 m, and the slopes exhibited western or eastern aspects. As the winters progressed, the volume of the edible crop remains declined, and the influences of the other main factors also changed, i.e., the factors of human disturbance (distance to road and settlement) became less important, while the effect of the food factor (crop remains) was strengthened. Thus, the foraging sites near the road became more important.ConclusionThe farming area surrounding the Caohai Wetland is very important for the overwintering Black-necked Crane. Food factors and human disturbance factors are the main factors that influence the choice of feeding ground.

Mercury bioaccumulation in zooplankton and its relationship with eutrophication in the waters in the karst region of Guizhou Province, Southwest China.

Zooplankton play an important role in the transfer of mercury (Hg) from the lower to upper trophic positions in the food chain. In this study, total mercury (THg) and methylmercury (MeHg) levels were measured in three size fractions of zooplankton collected from three reservoirs (Hongfeng, Baihua, and Aha Reservoir) and one wetland in karst areas to understand mercury accumulation in zooplankton from alkaline environments. The results showed that the alkaline waters had lower zooplankton MeHg levels (0.1 to 66.8ngg-1) than most of the acidic waters reported. However, the zooplankton THg levels (6.3 to 494.9ngg-1) were comparable. The macro-zooplankton (> 500μm) had significantly higher THg and MeHg levels than meso-zooplankton (116 to 500μm) in the three reservoirs at all seasons, which showed biomagnification of mercury in the food chain. The correlation between Hg in water and zooplankton and Hg in zooplankton of different sizes indicated that THg bioaccumulation in zooplankton was related to the THg levels in water; however, MeHg bioaccumulation in zooplankton was controlled by many other factors, such as their feeding and living habits. In the three reservoirs, the THg and MeHg concentrations in zooplankton decreased with increasing eutrophication. However, compared with the three reservoirs, Caohai Wetland, with large amounts of aquatic plants, had a much lower trophic level and higher MeHg content in water but much lower zooplankton MeHg levels and bioaccumulation factors (BAFs). The large amounts of plant residue might dilute mercury in the food chain, revealing that high primary production could result in lower Hg bioaccumulation, rather than only being influenced by nutrient levels.

Contents and distribution characteristics of nitrogen forms in sediments of Guizhou Lake Caohai under different water level levels

利用分级浸取分离法，分析贵州草海湿地沉积物总氮（TN）与可转化态氮（TF-N）含量及分布特征，试图揭示水位抬升对草海湿地沉积物氮潜在释放风险的影响.结果表明，草海湿地沉积物TN含量在1.94~14.07 g/kg之间，均值为7.76 g/kg；TF-N含量较高，在1.70~7.59 g/kg之间，占TN的68.7%；不同形态氮含量依次为有机态及硫化物结合态氮（OSF-N） > 离子交换态氮（IEF-N） > 铁锰氧化态氮（IMOF-N） > 弱酸可浸取态氮（WAEF-N）；不同水位梯度下各形态氮含量变化规律不同，OSF-N、IMOF-N含量沿着水位升高呈逐渐增加趋势，IEF-N含量呈先增加后降低的趋势，WAEF-N含量变化不大；TN和总非可转化态氮（NTF-N）与有机质（SOM）含量之间呈显著正相关，可能具有相似的来源.总之，草海沉积物TF-N含量及比例较高，潜在释放风险较大，而水位抬升抑制氮的转化，促进沉积物氮积累，增加释放风险.该研究揭示了不同水位梯度下沉积物氮形态分布特征，丰富了水文条件对氮迁移转化影响的理解，为湿地生态补水工程的管理决策提供了科学依据.;Lake Caohai situated in Guizhou Province is a plateau lake. The contents and distribution characteristics of total nitrogen (TN) and transferable nitrogen (TF-N) in sediments of Lake Caohai wetland were analyzed by using the method of fractional leaching and separation, and the effect of water level uplift on the potential nitrogen release risk of sediments was revealed. The results showed that the TN content in sediments ranged from 1.94 to 14.07 g/kg, with an average of 7.76 g/kg. The content of TF-N was relatively higher (between 1.70 and 7.59 g/kg), accounting for 68.7% of TN. Nitrogen content of transformable nitrogen in different forms was organic matter-sulfide form nitrogen (OSF-N) > ion-extractable form nitrogen (IEF-N) > iron-manganese oxides form nitrogen (IMOF-N) > weak acid extractable form nitrogen (WAEF-N). Under different water level, the changeable regulation of transformable nitrogen content of each form was different. OSF-N and IMOF-N increased gradually along the water level, while IEF-N first increased and then decreased. WAEF-N did not change much. There was a significant positive correlation between TN and non-transferable nitrogen (NTF-N) and soil organic matter (SOM), which may have similar sources. Shortly, Lake Caohai sediments have higher levels of transformable nitrogen and higher risk of potential release, while elevated water levels increase the risk of nitrogen release. The study reveals the nitrogen distribution characteristics of sediments under different water level, enriches the understanding of the impact of hydrological conditions on the migration and transformation of nitrogen, and provides a scientific basis for management decision of wetland ecological replenishment projects.

Mercury Distribution of Benthonic Animals and Response to Mercury in Sediments in Caohai Wetland, Guizhou Province

Caohai wetland is a National Nature Reserve. Benthic animals were collected from the deep-water area in the middle of Caohai Lake and the shallow-water area in the surrounding marshes, and mercury and methyl mercury distributions in the benthic animals were analyzed and discussed. The risk of mercury pollution was evaluated. The concentrations of total mercury and methyl mercury in the benthonic animals were in the range of 0.51-46.55 ng·g-1 with an average of 7.82 ng·g-1 and 0.04-27.71 ng·g-1 with an average of 4.31 ng·g-1, respectively. This was lower than reports from other natural reserves. By contrast, the total mercury and methyl mercury in the benthic animals in summer were higher than in other seasons, which was consistent with the characteristics of methyl mercury distribution in sediments but opposite to the spatial distribution characteristics of total mercury in sediments. The methyl mercury contents in Cipangopaludina cathayensis were positively correlated with the content of methyl mercury in the sediments (r=0.52, P<0.05). The results showed methylation and the bioavailability of mercury in sediments from the shallow-water area were obviously higher than those from the deep-water area in the middle of Caohai Lake. The difference in organic matter content of the sediment or the wet-dry alternation (flooding-receding-flooding) in the surrounding shallow marshes was suspected to be associated with the obvious difference. The high enrichment coefficient of total mercury and methyl mercury in benthic animals were sufficient to raise the risk of mercury contamination in the aquatic food chain in the wetland.

Tracing the origin and geochemical processes of dissolved sulphate in a karst-dominated wetland catchment using stable isotope indicators

Sulphur plays a critical role in the biogeochemistry of wetlands. SO42− is the sulphur form that is most commonly assimilated by plants, and it is the medium of sulphur transformation in wetland ecosystems. The Caohai wetland is an important ecosystem on the Yunnan–Guizhou Plateau, SW China, and karst water is the most important water source in this wetland. In this study, the compositions of multiple isotopes (δ34SSO4 and δ18OSO4) were measured in groundwater, river water and wetland water in the Caohai catchment to elucidate the solute sources and behaviours of sulphate. The results suggest that SO42− in groundwater is mainly derived from sulphide oxidation. Groundwater contributes a significant amount of sulphate to river water, and it is the main sulphate source of wetland water during the high-flow season. In contrast, rain water is the main sulphate source of wetland water during the low-flow season due to the reduction in groundwater recharge. These data indicate that groundwater is not only an important water source in the karst-dominated wetland catchment but also provides pathways by which sulphate is transported to the wetland. In addition, due to the effects of dissimilatory sulphate reduction in the wetland, the sulphate isotope composition in wetland water was higher than those in the groundwater and inflowing rivers, which indicates that biogeochemical processes in wetland ecosystems influence the sulphate content and composition in karst water.

Assessment of the distribution, bioavailability and ecological risks of heavy metals in the lake water and surface sediments of the Caohai plateau wetland, China.

In this study, selected heavy metals (Hg, As, Cd, Pb, Cr, Cu and Zn) in the lake water and sediments from the Caohai wetland, which is a valuable state reserve for migrant birds in China, were investigated to assess the spatial distribution, sources, bioavailability and ecological risks. The results suggested that most of the higher concentrations were found in the eastern region of the lakeshore. The concentration factor (CF) revealed that Hg, Cd and Zn were present from moderate risk levels to considerable risk levels in this study; thus, based on the high pollution load index (PLI) values, the Caohai wetland can be considered polluted. According to the associated effects-range classification, Cd may present substantial environmental hazards. An investigation of the chemical speciation suggested that Cd and Zn were unstable across most of the sites, which implied a higher risk of quick desorption and release. Principal component analysis (PCA) indicated that the heavy metal contamination originated from both natural and anthropogenic sources.

中国西南部云贵高原一个湿地系统氧氢同位素的季节性变化:地下水流入通量定量评价

The Caohai Wetland serves as an important ecosystem on the Yunnan–Guizhou Plateau and as a nationally important nature reserve for migratory birds in China. In this study, surface water, groundwater and wetland water were collected for the measurement of environmental isotopes to reveal the seasonal variability of oxygen and hydrogen isotopes (δ18O, δD), sources of water, and groundwater inflow fluxes. Results showed that surface water and groundwater are of meteoric origin. The isotopes in samples of wetland water were well mixed vertically in seasons of both high-flow (September) and low-flow (April); however, marked seasonal and spatial variations were observed. During the high-flow season, the isotopic composition in surface wetland water varied from −97.13 to −41.73‰ for δD and from −13.17 to −4.70‰ for δ18O. The composition of stable isotopes in the eastern region of this wetland was lower than in the western region. These may have been influenced by uneven evaporation caused by the distribution of aquatic vegetation. During the low-flow season, δD and δ18O in the more open water with dead aquatic vegetation ranged from −37.11 to −11.77‰, and from −4.25 to −0.08‰, respectively. This may result from high evaporation rates in this season with the lowest atmospheric humidity. Groundwater fluxes were calculated by mass transfer and isotope mass balance approaches, suggesting that the water sources of the Caohai Wetland were mainly from groundwater in the high-flow season, while the groundwater has a smaller contribution to wetland water during the low-flow season.

Sources, Spatial Distribution, and Seasonal Variation of Major Ions in the Caohai Wetland Catchment, Southwest China

The Caohai Wetland, Guizhou Province, China, is a nationally important nature reserve. In this study, we examined the major ion composition of the inflows to, and the water in, the Caohai Wetland. The main sources of major ions in the wetland water were the groundwater and river water inflows, the chemical compositions of which were controlled by the local geology, aquifer water–rock interactions, and human activities. The inflowing waters were the Ca–HCO3 type. The wetland water was classified as the Mg-HCO3, Mg-SO4, Ca-HCO3, and Ca-SO4 types during the high-flow season, and as the Ca-HCO3 type in the low-flow season. The physical and chemical properties of the wetland water varied widely from west to east. Concentrations of K+, Ca+, Mg2+, Cl−, and HCO3 − in the wetland water were higher in the low-flow season than in the high-flow season; K+, Na+, Cl−, and Mg2+ concentrations were higher in the wetland than in the inflowing waters in both seasons, and HCO3 − concentrations were lower in the wetland than in the inflowing waters. The chemical composition of the wetland water was mainly controlled by biogeochemical processes and evaporation in the high-flow season, and by evaporation in the low-flow season.

Emergent Vegetation Coverage and Human Activities Influence Oviposition Microhabitat Selection by Invasive Bullfrogs (Lithobates catesbeianus) in Southwestern China

Abstract Oviposition site selection is critical to increase offspring fitness for aquatic-breeding anurans, which generally lack posthatching parental care. Understanding factors that influence oviposition microhabitat choice would be helpful for managing and controlling invasive amphibians, such as the American Bullfrog (Lithobates catesbeianus), implicated in the decline of anuran populations across its invasive range. Factors that influence bullfrog oviposition microhabitat selection, however, remain mostly unknown. On the basis of field surveys from 2008 to 2013, we investigated 46 oviposition sites used by bullfrogs and 46 adjacent random unused sites and evaluated eight characteristics that could potentially influence oviposition site selection by bullfrogs in Caohai wetland, southwestern China, a global biodiversity conservation hot spot. We used model averaging of generalized linear mixed-effects models, using Akaike information criterion, hierarchical partitioning, and an ordination principal com...

Vertical distribution characteristics of soil organic carbon content in Caohai wetland ecosystem of Guizhou plateau, China

We selected four kinds of land use types from Caohai wetlands of Guizhou plateau (a total number of 32 soil profiles) to study the distribution characteristics of organic carbon content in soil. With different ways of land use, the organic carbon content of soil profiles and organic carbon density show the tendency of decreasing firstly and then increasing from top to bottom. With the increase of depth, the vertical difference becomes smaller first and then starts increasing. Land reclamation reduces the soil organic carbon content and density, changing its distribution structure in topsoil. The average content of organic carbon in Caohai wetlands are as follows: lake bed silt > marsh wetland > farmland > woodland, the average organic carbon content of lake bed silt, marsh wetland, farmland and woodland are 16.40, 2.94, 1.81 and 1.08 %, respectively. Land reclamation reduces the organic carbon content of soil, therefore the conversion of cultivated lands to wetlands and the increase of forest coverage will help to fix the organic carbon in soil and increase its reserves.

贵州草海湿地生态系统服务价值评估

PDF HTML阅读 XML下载 导出引用 引用提醒 贵州草海湿地生态系统服务价值评估 DOI: 10.5846/stxb201403250550 作者: 作者单位: 首都师范大学,首都师范大学,中国科学院生态环境研究中心,首都师范大学,首都师范大学,首都师范大学 作者简介: 通讯作者: 中图分类号: 基金项目: 林业公益性行业科研专项资助项目(201204201);北京市教委科研基地建设类项目资助 Evaluation of the ecosystem services in Caohai Wetland, Guizhou Province Author: Affiliation: Capital Normal University,Capital Normal University,Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences,Capital Normal University,Capital Normal University,Capital Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:贵州草海是中国三大高原淡水湖泊之一,其湿地生态系统能给人类提供产品和服务,为社会可持续发展提供基础,由于其价值没有被量化,人们对其重要性缺乏直观认识,导致了湿地的不合理开发及利用。根据草海湿地的特征,运用市场价值法、影子工程法、问卷调查法等定量评估了2010年草海湿地生态系统最终服务价值,包括供给服务、调节服务和文化服务。结果表明,草海湿地生态系统服务总价值为4.39×108元,其中供给服务价值为0.74×108元,调节服务价值为1.14×108元,文化服务价值为2.51×108元;所计算的10项服务按其价值大小排序为:休闲娱乐 > 生物多样性与景观资源保护 > 水资源供给 > 调蓄洪水 > 气候调节 > 补给地下水 > 大气组分调节 > 原材料生产 > 水质净化 > 食物生产;单位面积服务价值为16.40×104元/hm2,是2010年贵州省威宁县单位面积GDP产值的16.91倍。从研究结果来看,草海湿地生态系统服务价值较大,为草海湿地的管理及保护提供了一定参考依据。 Abstract:Wetlands are the kidneys of the Earth. Wetland ecosystems are vital in regulating the Earth's environmental balance. Caohai is one of the three Plateau Freshwater Lakes in China, located in the Yunnan-Guizhou Plateau within the Yangtze River watershed area, having an important role in the downstream water balance. The Caohai Wetland ecosystem provides people not only with essential ecosystem goods, such as raw materials and freshwater resources, but also has the potential to provide many services that are critical for regional sustainable development. However, the lack of information on the ecological economic value of Caohai Wetland hinders cooperation among different stakeholders. Furthermore, inappropriate development and pollution are threatening the functioning and the resultant benefits provided by these wetland systems. The economic valuation of Caohai Wetland ecosystems can help to clarify the tradeoffs among ecosystem services and social goods and services towards wise wetland management. In this paper, we divided the wetland ecosystem services into 3 main categories, provisioning services, regulating services, and cultural services, based on the underlying ecological mechanisms and beneficiary analyses. The 3 categories were further subdivided into 10 subcategories, food production, raw material production, water provisioning service, flood mitigation service, groundwater recharge service, water purification service, climate regulation service, gas regulation service, recreational service, and biodiversity and landscape conservation service. We evaluated the economic value of these 10 subcategories of wetland ecosystem services based on the year 2010 using different methodologies, such as the market value method, shadow engineering method, travel expense method, and contingent valuation method. According to the results of this valuation, the total economic value of the 10 subcategories of ecosystem services provided by Caohai Wetland was 4.39×108 Yuan RMB, of which provisioning services, regulating services, and cultural services contributed 0.74×108 Yuan RMB, 1.14×108 Yuan RMB, and 2.51×108 Yuan RMB, respectively. The major contributing services among all these wetland ecosystem services were recreational service, biodiversity and landscape conservation service, water provisioning service, and flood mitigation service. The total value of these four services was 3.78×108 Yuan RMB, which accounted for 86.05% of the total value, with recreational service value accounting for 29.93%, the biodiversity and landscape conservation service value accounting for 27.20%, the water provisioning service value accounting for 15.53%, and the flood mitigation service value accounting for 13.39%. The recreational value topped the others in the economic valuation, followed in order by biodiversity and landscape conservation value, water provisioning value, flood mitigation value, climate regulation value, groundwater recharge value, gas regulation value, raw material production value, water purification value, and food production value. The area of Caohai Wetland covers only 0.43% of Weining County, but the economic value of this wetland was 16.40×104 Yuan RMB per hectare, which is 16.91 times higher than the annual gross domestic product (GDP) per hectare of the county. Hence, it is inappropriate to transform Caohai Wetland into farmlands. The results of this study reflect the importance of Caohai Wetland in supporting the regional economy. Therefore, it is now important to raise public and government awareness to protect the wetlands for their continuous flow of sustainable services. Decision makers can incorporate the economic value of wetland ecosystem services to create ecological compensation mechanisms while dealing with the contradictions among different stakeholders. 参考文献 相似文献 引证文献

Heavy metals in an impacted wetland system: A typical case from southwestern China

Historical zinc smelting in Hezhang, southwestern China, has resulted in significant heavy metal contamination of the surrounding ecosystems. The Caohai wetland system, which is an important national nature reserve close to the Hezhang zinc smelting area, was investigated in the present study. Results showed that sediments from the Caohai wetland system have been seriously contaminated by Cd, Pb and Zn with the highest concentrations in the surface sediments being up to 71, 160 and 1200 μg g − 1 , respectively. The heavy metals in the sediments were strongly associated with the organic/sulphide and residual fractions. A more oxidized condition induced by aquatic plants tended to cause the Cd, Pb and Zn bound to the Fe–Mn oxide fraction to become more dominant. Pb isotopic compositions in the sediments indicated that the inventories of Pb in the Caohai wetland sediments were mainly derived from the historical zinc smelting in the Hezhang area, although other anthropogenic sources, such as the gasoline Pb, also made a substantial contribution to the Pb in the sediments. Heavy metal contamination in aquatic plants was also studied and the results indicated that heavy metals accumulated by plants may pose a potential threat to the higher trophic-level organisms, including humans.