Atmospheric Deposition Data Research Articles

Forecasting and Hindcasting PFAS Concentrations in Groundwater Discharging to Streams near a PFAS Production Facility.

Per- and polyfluoroalkyl substances (PFAS) are known to be highly persistent in groundwater, making it vital to develop new approaches to important practical questions such as the time scale for future persistence of PFAS in contaminated groundwater. In the approach presented here, groundwater from beneath streambeds was analyzed for PFAS and age-dated using SF6 and 3H/3He. The results were coupled with groundwater flux measurements in a convolution approach to estimate past and future PFAS concentrations in groundwater discharge to the streams. At our test site near the Cape Fear River (CFR) of North Carolina, PFAS were detected in groundwater up to 43 years old, suggesting that some PFAS entered groundwater immediately or shortly after fluorochemical production began at the nearby Fayetteville Works. Results are consistent with little to no retardation in groundwater for perfluoroethers such as hexafluoropropylene oxide-dimer acid (HFPO-DA) and perfluoro-2-methoxypropanoic acid (PMPA), the two most abundant PFAS, with mean concentrations of 229 and 498 ng/L, respectively. Future PFAS concentrations in groundwater discharge to streams were estimated to remain above current MCL or health advisory levels through at least 2050 or 2060 (using 3H/3He and SF6, respectively). Recent atmospheric deposition data suggest lower but non-negligible amounts of PFAS may continue to enter groundwater, likely further extending PFAS persistence in groundwater and the adjacent CFR. This approach shows promise for giving an overall perspective on persistence of PFAS in groundwater discharge from a broad contaminated area.

CAMELS-Chem: augmenting CAMELS (Catchment Attributes and Meteorology for Large-sample Studies) with atmospheric and stream water chemistry data

Abstract. Large sample datasets are transforming the catchment sciences, but there are few off-the-shelf stream water chemistry datasets with complementary atmospheric deposition, streamflow, meteorology, and catchment physiographic attributes. The existing CAMELS (Catchment Attributes and Meteorology for Large-sample Studies) dataset includes data on topography, climate, streamflow, land cover, soil, and geology across the continental US. With CAMELS-Chem, we pair these existing attribute data for 516 catchments with atmospheric deposition data from the National Atmospheric Deposition Program and water chemistry and instantaneous discharge data from the US Geological Survey over the period from 1980 through 2018 in a relational database and corresponding dataset. The data include 18 common stream water chemistry constituents: Al, Ca, Cl, dissolved organic carbon, total organic carbon, HCO3, K, Mg, Na, total dissolved N, total organic N, NO3, dissolved oxygen, pH (field and lab), Si, SO4, and water temperature. Annual deposition loads and concentrations include hydrogen, NH4, NO3, total inorganic N, Cl, SO4, Ca, K, Mg, and Na. We demonstrate that CAMELS-Chem water chemistry data are sampled effectively across climates, seasons, and discharges for trend analysis and highlight the coincident sampling of stream constituents for process-based understanding. To motivate their use by the larger scientific community across a variety of disciplines, we show examples of how these publicly available datasets can be applied to trend detection and attribution, biogeochemical process understanding, and new hypothesis generation via data-driven techniques.

Estimation of Groundwater Recharge in Makutupora Basin Located in a Semi-arid Region in Central Tanzania using Soil Moisture Balance (SMB) and Chloride Mass Balance (CMB) Techniques

ABSTRACT The objective of this study is to assess the groundwater recharge in the Makutupora basin, Central Tanzania using the soil moisture balance (SMB) and chloride mass balance (CMB) methods. The SMB method considered the estimation of both evapotranspiration in CROPWAT 8.0 software and surface runoff by the curve number (CN) method. The CN of the basin was determined based on hydrological soil group (HSG), antecedent moisture condition (AMC) and land use type using Arc GIS 10.2. Distributed land-use maps, slope and soil texture maps, daily climatological data (e.g., precipitation, temperature, wind speed, etc.), chloride concentration in rainfall and groundwater are the basic data used in this study. Input data were prepared in the form of digital maps using GIS and remote sensing tools and finally excel models were created to compute recharge using a set of given conditions. The results indicate that the average chloride concentration measured in the groundwater samples of the study area is 282.88 mg/L; much higher than the average concentration in rainwater samples which is 3.47mg/L while the average potential evapotranspiration is 2280 mm/year with an average rainfall of 680mm/year. Runoff computed using the CN method is ranging from 7.6-246mm/year or 0.68-22%. The final recharge from SMB is ranging from 0.025-117.86mm/year or 0.006-10% of annual rainfall equivalent to an average annual volume of 41.58Mm3 while recharge from CMB ranges from 2.57-44.6mm/year or 0.38-6.56% of annual rainfall equivalent to an average annual volume of 23.85Mm3. The results show that CMB underestimated the recharge compared to the SMB method. The reason for this is thought to be caused by the high chloride concentration analysed in groundwater compared to rainfall samples which may be caused by increased chloride concentration as water passes through the rock formations (unsaturated zone) to the saturated zone. Further lack of atmospheric chloride deposition data may be another contributing factor.

Sources, concentrations, distributions, fluxes and fate of microplastics in a hypersaline lake: Maharloo, south-west Iran

Hypersaline lakes support unique ecosystems and biogeochemistries but are often subject to anthropogenic pressures from pollution, water abstraction-diversion and climate change. Less understood, however, are the inputs, distributions and impacts of microplastics (MPs) in hypersaline environments. In this study, MPs are determined in water and sediment cores of Maharloo Lake, south-west Iran, and in the anthropogenically-impacted rivers that recharge the lake. MP concentrations in river water ranged from 0.05 MP L−1 in the headwaters to about 2 MP L−1 downstream of industrial effluents, with intermediate (but elevated) concentrations observed in the lake. The maximum surface concentration in lake sediment cores was about 860 MP kg−1, and concentrations displayed a progressive reduction with increasing depth down to 50 cm that are qualitatively consistent with temporal changes in plastic production. The size distribution of MPs was skewed towards the finest fraction (< 100 μm) and the most abundant polymer types were polyethylene terephthalate, polyethylene and nylon. Flux calculations using river water data and published atmospheric deposition data for the region reveal that the atmosphere is, by at least an order of magnitude, the more important source. MPs added to the lake appear to be maintained in suspension by high density water but are subsequently deposited to sediments by encapsulation and nucleation as salts precipitate. In addition, it is proposed that direct atmospheric deposition to sediment takes place on areas that seasonally dry out and are subsequently inundated. The impacts of MPs on hypersaline ecosystems and biomass resources are unknown but warrant investigation.

Drivers of Dissolved Organic Carbon Mobilization From Forested Headwater Catchments: A Multi Scaled Approach

Understanding and predicting catchment responses to a regional disturbance is difficult because catchments are spatially heterogeneous systems that exhibit unique moderating characteristics. Changes in precipitation composition in the Northeastern U.S. is one prominent example, where reduction in wet and dry deposition is hypothesized to have caused increased dissolved organic carbon (DOC) export from many northern hemisphere forested catchments; however, findings from different locations contradict each other. Using shifts in acid deposition as a test case, we illustrate an iterative “process and pattern” approach to investigate the role of catchment characteristics in modulating the steam DOC response. We use a novel dataset that integrates regional and catchment-scale atmospheric deposition data, catchment characteristics and co-located stream Q and stream chemistry data. We use these data to investigate opportunities and limitations of a pattern-to-process approach where we explore regional patterns of reduced acid deposition, catchment characteristics and stream DOC response and specific soil processes at select locations. For pattern investigation, we quantify long-term trends of flow-adjusted DOC concentrations in stream water, along with wet deposition trends in sulfate, for USGS headwater catchments using Seasonal Kendall tests and then compare trend results to catchment attributes. Our investigation of climatic, topographic, and hydrologic catchment attributes vs. directionality of DOC trends suggests soil depth and catchment connectivity as possible modulating factors for DOC concentrations. This informed our process-to-pattern investigation, in which we experimentally simulated increased and decreased acid deposition on soil cores from catchments of contrasting long-term DOC response [Sleepers River Research Watershed (SRRW) for long-term increases in DOC and the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) for long-term decreases in DOC]. SRRW soils generally released more DOC than SSHCZO soils and losses into recovery solutions were higher. Scanning electron microscope imaging indicates a significant DOC contribution from destabilizing soil aggregates mostly from hydrologically disconnected landscape positions. Results from this work illustrate the value of an iterative process and pattern approach to understand catchment-scale response to regional disturbance and suggest opportunities for further investigations.

Long‐Term Shifts in U.S. Nitrogen Sources and Sinks Revealed by the New TREND‐Nitrogen Data Set (1930–2017)

AbstractReactive nitrogen (N) fluxes have increased tenfold over the last century, driven by increases in population, shifting diets, and increased use of commercial N fertilizers. Runoff of excess N from intensively managed landscapes threatens drinking water quality and disrupts aquatic ecosystems. Excess N is also a major source of greenhouse gas emissions from agricultural soils. While N emissions from agricultural landscapes are known to originate from not only current‐year N input but also legacy N accumulation in soils and groundwater, there has been limited access to fine‐scale, long‐term data regarding N inputs and outputs over decades of intensive agricultural land use. In the present work, we synthesize population, agricultural, and atmospheric deposition data to develop a comprehensive, 88‐year (1930–2017) data set of county‐scale components of the N mass balance across the contiguous United States (Trajectories Nutrient Dataset for nitrogen [TREND‐nitrogen]). Using a machine‐learning algorithm, we also develop spatially explicit typologies for components of the N mass balance. Our results indicate a large range of N trajectory behaviors across the United States due to differences in land use and management and particularly due to the very different drivers of N dynamics in densely populated urban areas compared with intensively managed agricultural zones. Our analysis of N trajectories also demonstrates a widespread functional homogenization of agricultural landscapes. This newly developed typology of N trajectories improves our understanding of long‐term N dynamics, and the underlying data set provides a powerful tool for modeling the impacts of legacy N on past, present, and future water quality.

Post-fire ecological consequences within the drained site of the Great Vasyugan Mire: retrospective water-thermal regime and pyrogenic disturbance estimation

The aim of this research is to carry out an assessment of pyrogenic load after the fire event in 2016 within the drained site of Great Vasyugan mire (Bakchar bog, North-East part of The Great Vasyugan mire). Specifically, the objectives of this study were to: 1) perform a retrospective analysis of the water-thermal regime of the area under study according to monitoring data on the nearby site for estimation of development emergence of a fire-dangerous situation conditions; 2) determine the quantitative characteristics of vegetation and microtopography fire transformation based on field data; 3) estimate zone of contamination by combustion products and 4) estimate the hydrocarbons composition of mire and river water, peat and typical plants of the pyrogenic disturbed bog. The water-thermal retrospective analysis confirmed that in August 2016, the most favourable conditions for the emergence of a fire-dangerous situation were developed. The area of fire spread was 5.54 km2, including within the mire of 4.44 km2. The area of Zn and Pb pollution covers an area of 8 km, which is consistent with the prevailing wind direction and atmospheric deposition data for 2016. The zone of extreme pollution of heavy metal peat deposits is limited mainly by the zone of intensive burning of the surface, however, and beyond it, there was also a significant (2 times) Zn, Cd and Pb concentration (except Cu) increase, mainly due to the migration of elements with water flow. Carbon losses for the burned area of 1 square metre to a depth of 30 cm were about 3,800 gC/m2. Against the background of a decrease in the content of n-alkanes, their share in the composition of peat lipids of the burnt area increases slightly, and among them the content of homologues C23–C25 increases, C29–C33 decreases and the CPI value decreases.

Evidence for accelerated weathering and sulfate export in high alpine environments

High elevation alpine ecosystems—the ‘water towers of the world’—provide water for human populations around the globe. Active geomorphic features such as glaciers and permafrost leave alpine ecosystems susceptible to changes in climate which could also lead to changing biogeochemistry and water quality. Here, we synthesize recent changes in high-elevation stream chemistry from multiple sites that demonstrate a consistent and widespread pattern of increasing sulfate and base cation concentrations or fluxes. This trend has occurred over the past 30 years and is consistent across multiple sites in the Rocky Mountains of the United States, western Canada, the European Alps, the Icelandic Shield, and the Himalayas in Asia. To better understand these recent changes and to examine the potential causes of increased sulfur and base cation concentrations in surface waters, we present a synthesis of global records as well as a high resolution 33 year record of atmospheric deposition and river export data from a long-term ecological research site in Colorado, USA. We evaluate which factors may be driving global shifts in stream chemistry including atmospheric deposition trends and broad climatic patterns. Our analysis suggests that recent changes in climate may be stimulating changes to hydrology and/or geomorphic processes, which in turn lead to accelerated weathering of bedrock. This cascade of effects has broad implications for the chemistry and quality of important surface water resources.

Reducing Wet Ammonium Deposition in Rocky Mountain National Park: the Development and Evaluation of A Pilot Early Warning System for Agricultural Operations in Eastern Colorado.

Agricultural emissions are the primary source of ammonia (NH3) deposition in Rocky Mountain National Park (RMNP), a Class I area, that is granted special air quality protections under the Clean Air Act. Between 2014 and 2016, the pilot phase of the Colorado agricultural nitrogen early warning system (CANEWS) was developed for agricultural producers to voluntarily and temporarily minimize emissions of NH3 during periods of upslope winds. The CANEWS was created using trajectory analyses driven by outputs from an ensemble of numerical weather forecasts together with the climatological expertize of human forecasters. Here, we discuss the methods for the CANEWS and offer preliminary analyses of 33 months of the CANEWS based on atmospheric deposition data from two sites in RMNP as well as responses from agricultural producers after warnings were issued. Results showed that the CANEWS accurately predicted 6 of 9 high N deposition weeks at a lower-elevation observation site, but only 4 of 11 high N deposition weeks at a higher-elevation site. Sixty agricultural producers from 39 of Colorado's agricultural operations volunteered for the CANEWS, and a two-way line of communication between agricultural producers and scientists was formed. For each warning issued, an average of 23 producers responded to a postwarning survey. Over 75% of responding CANEWS participants altered their practices after an alert. While the current effort was insufficient to reduce atmospheric deposition, we were encouraged by the collaborative spirit between agricultural, scientific, and resource management communities. Solving a broad and complex social-ecological problem requires both a technological approach, such as the CANEWS, and collaboration and trust from all participants, including agricultural producers, land managers, university researchers, and environmental agencies.

Measuring and Calculating Current Atmospheric Phosphorous and Nitrogen Loadings to Utah Lake Using Field Samples and Geostatistical Analysis

Atmospheric nutrient loading through wet and dry deposition is one of the least understood, yet can be one of the most important, pathways of nutrient transport into lakes and reservoirs. Nutrients, specifically phosphorus and nitrogen, are essential for aquatic life but in excess can cause accelerated algae growth and eutrophication and can be a major factor that causes harmful algal blooms (HABs) that occur in lakes and reservoirs. Utah Lake is subject to eutrophication and HABs. It is susceptible to atmospheric deposition due to its large surface area to volume ratio, high phosphorous levels in local soils, and proximity to Great Basin dust sources. In this study we collected and analyzed eight months of atmospheric deposition data from five locations near Utah Lake. Our data showed that atmospheric deposition to Utah Lake over the 8-month period was between 8 to 350 Mg (metric tonne) of total phosphorus and 46 to 460 Mg of dissolved inorganic nitrogen. This large range is based on which samples were used in the estimate with the larger numbers including results from “contaminated samples”. These nutrient loading values are significant for Utah Lake in that it has been estimated that only about 17 Mg year−1 of phosphorus and about 200 Mg year−1 of nitrogen are needed to support a eutrophic level of algal growth. We found that atmospheric deposition is a major contributor to the eutrophic nutrient load of Utah Lake.

Validating modelled data on major and trace element deposition in southern Germany using Sphagnum moss

Sphagnum mosses were collected from four ombrotrophic bogs in two regions of southern Germany: Upper Bavaria (Oberbayern, OB) and the Northern Black Forest (Nordschwarzwald, NBF). Surfaces of Sphagnum carpets were marked with plastic mesh and, one year later, plant matter was harvested and productivity determined. Major and trace element concentrations (Ag, Al, As, Ba, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Rb, Sb, Sc, Sr, Th, Ti, Tl, U, V, Zn) were determined in acid digests using sector field ICP-MS. Up to 12 samples (40 × 40 cm) were collected per site, and 6–10 sites investigated per bog. Variation in element accumulation rates within a bog is mostly the result of the annual production rate of the Sphagnum mosses which masks not only the impact of site effects, such as microtopography and the presence of dwarf trees, but also local and regional conditions, including land use in the surrounding area, topography, etc. The difference in productivity between peat bogs results in distinctly higher element accumulation rates at the NBF bogs compared to those from OB for all studied elements. The comparison with the European Monitoring and Evaluation Program (EMEP; wet-only and total deposition) and Modelling of Air Pollutants and Ecosystem Impact (MAPESI; total deposition) data shows that accumulation rates obtained using Sphagnum are in the same range of published values for direct measurements of atmospheric deposition of As, Cd, Cu, Co, Pb, and V in both regions. The accordance is very dependent on how atmospheric deposition rates were obtained, as different models to calculate the deposition rates may yield different fluxes even for the same region. In future studies of atmospheric deposition of trace metals, both Sphagnum moss and deposition collectors have to be used on the same peat bog and results compared. Antimony, however, shows considerable discrepancy, because it is either under-estimated by Sphagnum moss or over-estimated by both atmospheric deposition models. Atmospheric deposition data obtained from sampling in open fields is unlikely to always perfectly match data obtained using living Sphagnum moss from bogs. In fact, plant uptake and biochemical utilization by living moss may affect accumulation rates of those elements that are essential for plant nutrition (macro and micronutrients), which is clearly seen in the data presented here for Mn, Fe and Zn. Furthermore, Sphagnum moss is a unique receptor, with its characteristic roughness and chemical complexity. These two aspects, combined with conditions found on the bog surface (variations in microtopography, shrubs, trees, wetness, snow cover, etc.), result in a unique type of interception and retention. Despite all these factors, the comparison with modelled data shows that Sphagnum moss is a good indicator of atmospheric deposition at least in a semi-quantitative manner and certainly reflects inputs to terrestrial ecosystems.

Bioindication and modelling of atmospheric deposition in forests enable exposure and effect monitoring at high spatial density across scales

Moss surveys provide spatially dense data on environmental concentrations of heavy metals and nitrogen which, together with other biomonitoring and modelling data, can be used for indicating deposition to terrestrial ecosystems and related effects across time and areas of different spatial extension. For enhancing the spatial resolution of measuring and mapping atmospheric deposition by technical devices and by modelling, moss is used complementarily as bio-monitor. This paper investigated whether nitrogen and heavy metal concentrations derived by biomonitoring of atmospheric deposition are statistically meaningful in terms of compliance with minimum sample size across several spatial levels (objective 1), whether this is also true in terms of geostatistical criteria such as spatial auto-correlation and, by this, estimated values for unsampled locations (objective 2) and whether moss indicates atmospheric deposition in a similar way as modelled deposition, tree foliage and natural surface soil at the European and country level, and whether they indicate site-specific variance due to canopy drip (objective 3). Data from modelling and biomonitoring atmospheric deposition were statistically analysed by means of minimum sample size calculation, by geostatistics as well as by bivariate correlation analyses and by multivariate correlation analyses using the Classification and Regression Tree approach and the Random Forests method. It was found that the compliance of measurements with the minimum sample size varies by spatial scale and element measured. For unsampled locations, estimation could be derived. Statistically significant correlations between concentrations of heavy metals and nitrogen in moss and modelled atmospheric deposition, and concentrations in leaves, needles and soil were found. Significant influence of canopy drip on nitrogen concentration in moss was proven. Moss surveys should complement modelled atmospheric deposition data as well as other biomonitoring approaches and offer a great potential for various terrestrial monitoring programmes dealing with exposure and effects.

Colloidal transport in the Gordon Gulch catchment of the Boulder Creek CZO and its effect on C‐Q relationships for silicon

AbstractThe near‐constant Si concentration under varying discharge observed in Gordon Gulch of the Boulder Critical Zone Observatory (CZO) indicates that the silica fluxes are strongly controlled by discharge. To identify the mechanisms supplying increased Si at high discharge (Q), we examine Si‐Al‐Fe‐Ge in soils, streams, and groundwaters. We identify bedrock weathering in groundwater and colloidal transport as the two end‐members that supply Si to the system. During base flow, streamflow is derived from groundwater, and weathering of feldspar is the main source of Si with a Ge/Si ratio 0.2–0.5 µmol/mol and low dissolved Al and Fe. The groundwater data are consistent with incongruent weathering of feldspar as the main source of dissolved Si. As discharge increases, Si‐Al‐Fe‐bearing colloids are mobilized and the Ge/Si ratio of the stream rises to 3.0 µmol/mol. Mineralogical analysis using XRD identified Al‐Si phases including kaolinite, illite, and quartz in the colloidal size fraction (&lt;0.45 µm). The Ge/Si ratio of stream and soil colloids is ≈3.8 µmol/mol. The mechanism of colloidal transport with increasing discharge can account for the concentration‐discharge (C‐Q) patterns of Si, Al, and Fe with near‐zero or positive power law slopes observed in the Gordon Gulch catchment. Anomalously high Ge/Si ratios also identified a third end‐member resulting from coal fly ash deposition during the winter and spring. Wind trajectories during 2012, correlation between Ge/Si and , and comparison to atmospheric deposition data imply contamination from nearby coal fired power plant operations.

Assessing the Impact of Local and Regional Influences on Nitrogen Loads to Buzzards Bay, MA

Nitrogen and chlorophyll-a concentrations in estuarine systems often correlate positively with increased nitrogen input. To determine the interactions between nitrogen load, physical drivers, and water quality indicators, we estimated nitrogen inputs to 28 estuaries within the Buzzards Bay, Massachusetts (USA) watershed from 1985-2013. Estimates were derived by combining parcel specific wastewater disposal, point source wastewater discharge, land use, and atmospheric nitrogen deposition data with a previously verified nitrogen loading model. Linear regression analysis was used to quantify temporal trends in individual data sets and characterize relationships between variables. The land-use data indicated that fractional coverage of impervious surfaces increased with time for all sub-watersheds at the expense of vegetation and agriculture land use classes, reflecting a growth in residential unit density. Nitrogen loads decreased with time for most watersheds on the western side of Buzzards Bay, reflecting decreased atmospheric nitrogen deposition combined with management efforts to mitigate wastewater pollution. For most of Buzzards Bay’s eastern watersheds increases in nitrogen sourced from wastewater, driven primarily by the development of homes with on-site wastewater disposal, resulted in overall nitrogen load increases. The relationship between nitrogen load and mean summer in situ chlorophyll a underwent a shift to more chlorophyll a per unit nitrogen input over time that was partially correlated to climatic variables such as increased precipitation and warming water column temperatures.

SWAT Modeling of Nitrogen Dynamics Considering Atmospheric Deposition and Nitrogen Fixation in a Watershed Scale

The Soil and Water Assessment Tool (SWAT) nitrogen (N) water quality model considers the artificial inputs associated with human activities, including point and nonpoint source pollution loads. Although SWAT has the ability to simulate atmospheric N deposition and fixation, they were not considered in the modeling research. N deposition from the air is an important and considerable pathway for the input of N species into watersheds and water bodies, causing soil and water body acidification and the leaching of N into surface and groundwater, resulting in eutrophication and degraded water quality. The goal of this study is to assess the effects of atmospheric and agricultural N loads on stream water quality at the watershed scale. For a 6642 km2 Chungju dam watershed, SWAT was calibrated for 4 years (2003-2006) and validated for another 4 years (2007-2010) using daily anthropogenic N data (sewage discharge pollutants and fertilizer) and monthly measured atmospheric deposition data for NO3ˉ, NH4+, and dissolved organic N (DON). At the watershed outlet, the Nash-Sutcliffe (1970) efficiency (NSE) of daily streamflow during the validation period was 0.74. The coefficient of determination (R2) of total N was 0.69 considering atmospheric deposition, whereas it was 0.33 when removing the deposition effect. The results of this study demonstrate the potential for using the N dynamics between the atmosphere and land for SWAT assessments of nonpoint source pollution and for modeling stream water quality.

Developing Critical Loads of Nitrate and Sulfate Deposition to Watersheds of the Great Smoky Mountains National Park, USA

Long-term impacts of acidic deposition on the Great Smoky Mountains National Park (GRSM) include elevated inputs of sulfate, nitrate, and ammonium; the depletion of available nutrient cations from soil; and acidification of high-elevation streams. Critical loads and target loads (CLs/TLs) are useful tools to help guide future air quality management. We evaluated past and potential future effects of nitrate and sulfate deposition for 12 watersheds in the GRSM, USA, using the hydrochemical model, photosynthesis evapotranspiration biogeochemical (PnET-BGC). Two of the streams studied were listed by the state of Tennessee as impaired due to low stream pH. We reconstructed historical meteorological, atmospheric deposition, and land disturbance data for study watersheds for the period 1850 to present for model hindcasts. As future emissions are expected to decline, the model was run under a range of future scenarios from 2008 to 2200 of decreases in sulfate, nitrate, and ammonium and combinations of sulfate and nitrate deposition to estimate CLs and TLs of how watersheds might respond to emission control strategies. Model simulations of stream chemistry generally agreed with long-term (>10 years) observations. Model hindcasts indicate that watersheds in the GRSM are inherently sensitive to acidic deposition. Simulated mean projected stream ANC of 71 μeq/L (range 32 to 107 μeq/L) prior to industrial development (~1850) decreases in response to historical acidic deposition to 33 μeq/L (−13 to 88 μeq/L) in 2007. Future model projections show that decreases in sulfate deposition result in smaller increases in stream ANC compared with equivalent decreases in nitrate deposition; simultaneous controls on nitrate and sulfate deposition are more effective in ANC increases than individual control of nitrate or sulfate. Although there are no current programs in the USA to control ammonia emissions, model simulations suggest that decreases in ammonium deposition could also help mitigate acidification to a greater extent than equivalent controls on nitrate deposition.

艾比湖湿地退化对盐尘暴发生及运移路径的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 艾比湖湿地退化对盐尘暴发生及运移路径的影响 DOI: 10.5846/stxb201312263034 作者: 作者单位: 新疆大学资源与环境科学学院 绿洲生态教育部重点实验室 作者简介: 通讯作者: 中图分类号: X87 基金项目: 国家自然科学基金项目(41130531,41261090,41161063) Effect of salt dust storm migration pathways on degradation of Ebinur Lake Wetland Author: Affiliation: College of Resources and Environment Science,Xinjiang University,Key Laboratory of Oasis Ecosystem of Education Ministry,Xinjiang 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:新疆艾比湖湿地内间歇性裸露的干涸湖底加重了周围区域的盐渍化程度,为盐尘暴的发生发展提供了粉尘物质来源。盐碱粉末在风力作用下以颗粒物的形式悬浮在空中并向周围扩散,严重危害周边区域的生态安全和社会经济发展。本文选择研究区三期遥感影像,结合同期野外实测大气降尘及地表土壤采样数据,剖析区域土壤盐渍化与盐尘暴发生作用机制,探讨艾比湖湿地退化引发的盐尘暴在传输、沉降过程中对源地及途经区域的生态环境的影响,进而对盐尘暴的运移路径进行模拟预测。有关成果对于揭示该区域独特的盐尘暴发生及作用机制问题具有重要作用。 Abstract:The lake wetlands are a transition zone between aquatic and terrestrial ecosystems. They are also one of the most important environments that sustain human beings, especially in arid and semi-arid areas of Northwestern China. The lake wetland ecosystem not only serves as an important media reflecting the dynamics of the local natural processes and habitat, but also promotes the interaction between human beings and the nature to maintain a sustainable balance between the two. Salt dust storm and alkaline dust deposition are generally caused by lack of water as loose deposits, dry lake bed crust, salt and saline soil are blown and salt deposits are dispositioned due to wind erosion. The salt powder in the form of suspended particles in the air becomes a natural disaster accompanied with strong wind. In addition to saline, alkaline elements, it contains crystalline dry lakebed sediments, toxic chemicals, and harmful heavy metal particles, which threaten plant survival. The development process of alkaline dust storm not only contaminates the air, food, water, and other natural resources with a mix of bacteria, fungi, and other toxic and harmful substances, but it also destroys the grassland and crops, and causes various diseases in humans and livestock. Intermittently exposed lake bottom of dry lake in the Ebinur Lake region is the primary source for salt dust storms in the surrounding area. Saline powder suspends in the air and spreads in the form of particles with the wind, seriously endangering the ecological stability and socio-economic development of the surrounding area. The current study attempts to investigate the dust storm migration pathways and its environmental effects using three remote sensing images combined with synchronous field measurements of salt dust and surface soil samples with the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. We also explore the environmental changes caused by salt dust storms and their impacts on the settlement process of Ebinur Lake by simulating and predicting the migration pathways of salt dust storms. Combining atmospheric dust deposition and surface soil data as well as the westerly direction and airflow path, we simulated the transport trajectories of salt dust for about four months in Bortala Mongol Autonomous Prefecture of Xinjiang Uyghur Autonomous Region, China. The results indicate that: (1) the degree of soil salinization within the study area is uneven. The highest level of salinization occurs around the Ebinur Lake but gradually weakens towards the peripheral expansion areas; (2) the dynamics of saline land is closely related to the change in vegetation cover and water area and to human activity, which also has a significant impact on the evolution of soil salinization; (3) there are two different paths of salt dust storm, the north path starting from Bortala Mongol Autonomous Prefecture→Aletai→Gansu→Inner Mongolia→Mongolia→Heilongjiang and southeastern path from Bortala Mongol Autonomous Prefecture (Jinghe, Bole, Wenquan, and Alashankou)→Wusu→Kuitun→Vrümqi→Kurla→Turpan→Kumul. Our results present important information regarding the occurrence and mechanism of salt and dust storms in arid and semi-arid regions. 参考文献 相似文献 引证文献

Atmospheric Dry Deposition Of Total Phosphorous Prediction Using Neural Network

Surface waters are threatened by pollutants of atmospheric origin. Atmospheric deposition in Singapore and surrounding countries appears to provide significant fluxes of nutrients (Nitrogen species and Phosphorous species) of environmental concern and to play an important role in the eutrophication of surface water. The quantitative assessment of atmospheric nutrient depositions are essential for understanding regional variations, time at which critical loads exceed, and the air/water quality management on the regional scale. This paper presents a data-driven approach, artificial neural networks (ANNs), for effective and efficient prediction of total phosphorous (TP) from dry atmospheric deposition. Dry atmospheric nutrient deposition data were obtained from laboratory analysis of aerosol samples collected using a high volume air sampler every 48 hours continuously during 2006 haze period in the field monitoring, Singapore. The results of the best ANN model was rather satisfactory, with values of the Nash–Sutcliffe coefficient of efficiency

Model-based Scenario Analysis of the Impact of Remediation Measures on Metal Leaching from Soils Contaminated by Historic Smelter Emissions.

A spatially distributed model for leaching of Cd from the unsaturated zone was developed for the Belgian-Dutch transnational Kempen region. The model uses as input land-use maps, atmospheric deposition data, and soil data and is part of a larger regional model that simulates transport of Cd in soil, groundwater, and surface water. A new method for deriving deposition from multiple sites was validated using soil data in different wind directions. Leaching was calculated for the period 1890 to 2010 using a reconstruction of metal loads in the region. The model was able to reproduce spatial patterns of concentrations in soil and groundwater and predicted the concentration in shallow groundwater adequately well for the purpose of evaluating management options. For 42% of the data points, measurements and calculations were within the same concentration class. The model was used for forecasting under a reference scenario, an autonomous development scenario including climate change, and a scenario with implementation of remediation measures. The impact of autonomous development (under the most extreme scenario of climatic change) amounted to an increase of 10% in cumulative Cd flux after 100 yr as compared with the reference scenario. The impact of remediation measures was mainly local and is less pronounced (i.e., only 3% change in cumulative flux at the regional scale). The integrated model served as a tool to assist in developing management strategies and prioritization of remediation of the wide-spread heavy metal contamination in the region.

Quantitative Analysis of the Rate of Geochemical Weathering of Sulfur from Sedimentary Rocks Using Atmospheric Deposition, Concentration and River Discharge Data

Quantitative analysis of the rate of geochemical weathering of sulfur (S) from sedimentary rocks (GeoS) was conducted using concentration (Cs) and discharge (Qs) data from the Tedori River and atmospheric deposition (AtdepS) in the basin. First, S fluxes were calculated using 16 years of Cs and Qs data. The annual average discharge of S (TotalS) was estimated at 8597 ton·year-1 (117.3 kg·ha-1·year-1). Of this, 1331 ton·year-1 was AtdepS (18.2 kg·ha-1·year-1) and another 7266 ton·year-1 was GeoS (99.1 kg·ha-1·year-1). Monthly changes in TotalS were investigated, which showed that GeoS was highest in summer, because of the air temperature, while AtdepS peaked in winter because of seasonal wind. Using Qs and AtdepS corrected for altitude, TotalS, AtdepS and GeoS were estimated at six sites, and among these sites we found that the TotalS per unit area values were random, depending on the site characteristics. In particular, the discharge from the Kuwajima site was remarkably high suggesting that the sedimentary rocks at this site had higher pyrite content than at the other sites. Finally, we also assessed the relationship between the characteristics of sedimentary rocks and GeoS in a range of rivers in the Hokuriku Region, and found that there was a close relationship between concentrations of SO42- greater than 10 mg·l-1 and sedimentary rocks containing the pyrite group. In addition, we estimated that the influence of GeoS was present when the concentration of SO42- in river water was greater than 2 - 3 mg·l-1 in the Hokuriku region.