摘要：
Uncertainty analysis of evapotranspiration models is essential in hydrological modeling, particularly given the limited use of process-based models and ensemble algorithms for evapotranspiration estimation. In this study, the performance and uncertainty in two simplified process-based models (BTA and BTA-theta), and three classical ensemble algorithms (adaptive boosting, random forest, and extreme gradient boosting) in estimating evapotranspiration are assessed across various ecosystems. The results show that: (a) the BTA-theta model outperforms the BTA model across all ecosystems, and the integrated algorithms perform better than the two process-based models. (b) In the two process-based models, parameter k is insensitive to the outcomes, while parameters b, k1, and theta 1 are highly sensitive. (c) The primary source of uncertainty in the ensemble algorithms is parameterization, the structure of the BTA model, and the input data of the BTA-theta model. The findings provide valuable insights for increasing the evapotranspiration estimation accuracy and reliability. This study helps to improve the accuracy and reliability of evapotranspiration estimation in terrestrial ecosystems.
摘要：
菜地土壤重金属污染不仅影响蔬菜质量还对人体产生潜在的健康风险。本文以衡阳市三大工业园区周边菜地土壤为研究对象，通过分析Cu、Zn、Pb、Mn和Hg五种重金属的含量特征，并利用地累积指数、潜在生态风险指数和人体健康风险指数法对其污染现状及潜在风险进行评价。结果表明：（1）以土壤环境质量农用地土壤污染风险管控值为标准，衡阳市三大工业园区周边菜地土壤中重金属Cu、Pb、Zn含量超过风险管控值的点位为68%、66%、10%，其中在Cu和Pb超标点位中白沙洲工业园区周边菜地分别占76.5%和50%,Mn和Hg尚未超标。（2）通过地累积指数评价，白沙洲工业园区周围菜地土壤中Zn呈偏中度污染，Hg、Cu轻度污染；松木工业园区周围菜地土壤中Zn呈偏中度污染，Pb、Hg轻度污染；衡钢产业区周围菜地土壤中Cu、Zn、Hg存在轻度污染。（3）潜在生态风险指数（RI）显示三大工业园区菜地土壤5种重金属RI贡献大小依次为：RI （松木工业园区）＞ RI （衡钢产业区）＞ RI （白沙洲工业园区），这三个工业园区的菜地土壤属于轻微生态危害。（4）研究区土壤中5种重金属目前均不会对成人和儿童造成非致癌风险。衡阳市三大工业园区周边菜地虽部分已受到了一定的污染，但其致癌风险可以忽略。
通讯机构：
[Shunqing Zhong] C;College of Geography and Tourism, Hengyang Normal University, 421002 Hengyang, China<&wdkj&>Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden
摘要：
A geographically constrained chronosequence of peatlands divided into three age classes (young, intermediate and old) was used to explore the role of biogeochemical influences, including electron donors and acceptors as well as chemical speciation of inorganic mercury (Hg(II)), on net formation of methylmercury (MeHg) as approximated by the fraction of MeHg to total mercury (THg) in the peat soil. We hypothesized that removing vascular plants would reduce availability of electron donors and thus net MeHg formation. However, we found no effect of the vascular plant removal. The sum of the potential electron donors (acetate, lactate, propionate and oxalate), the electron donation proxy organic C/Organic N, and the potential electron acceptors (Fe(III), Mn and sulfate) in porewater all showed significant correlations with the net MeHg formation proxies in peat soil (MeHg concentration and %MeHg of THg). Thus differences in both electron donor and acceptor availability may be contributing to the pattern of net MeHg formation along the chronosequence. In contrast, Hg(II) concentrations in peat porewater showed small differences along the gradient. A chemical speciation model successfully predicted the solubility of Hg and MeHg in the porewater. The modeling pointed to an enhanced concentration of Hg-polysulfide species in the younger peatlands as a potential factor behind increased Hg(II) solubility and methylation in the more nutrient-rich peatlands. This work contributes to the understanding of Hg and MeHg cycling in peatlands which can help guide mitigation measures to reduce aquatic MeHg biomagnification in peatland dominated landscapes. (C) 2021 The Authors. Published by Elsevier Ltd.
摘要：
Peatlands are abundant elements of boreal landscapes where inorganic mercury (IHg) can be transformed into bioaccumulating and highly toxic methylmercury (MeHg). We studied fifteen peatlands divided into three age lasses (young, intermediate and old) along a geographically constrained chronosequence to determine the role of biogeochemical factors and nutrient availability in controlling the formation of MeHg. In the 10 cm soil layer just below the average annual growing season water table, concentrations of MeHg and %MeHg (of total Hg) were higher in younger, more mesotrophic peatlands than in older, more oligotrophic peatlands. In contrast, total mercury (THg) concentrations were higher in the older peatlands. Partial least squares (PLS) analysis indicates that the net MeHg production was positively correlated to trophic demands of vegetation and an increased availability of potential electron acceptors and donors for Hg methylating microorganisms. An important question for further studies will be to elucidate why there is less THg in the younger peatlands compared to the older peatlands, even though the age of the superficial peat itself is similar for all sites. We hypothesize that ecosystem features which enhance microbial processes involved in Hg methylation also promote Hg reduction that makes previously deposited Hg more available for evasion back to the atmosphere. (C) 2020 Elsevier B.V. All rights reserved.
