Geostatistical analysis of soil hydrologic properties in a field plot

A 91-m transect was set up in an irrigated field near Las Cruces, New Mexico to obtain soil water tension and water content data to investigate their spatial variability. A total of 455 sampling points were monitored along a grid consisting of 91 stations placed 1 m apart by 5 depths per station (at 0.3, 0.6, 0.9, 1.2 and 1.5 m below the surface). Post-irrigation tension and wetness measurements were recorded over 45 days at 11 time periods. Soil water tension was measured with tensiometers using a hand-held pressure transducer. A neutron probe was used to obtain volumetric water content. Using the observed wetness and tension data, unsaturated hydraulic conductivity values were derived (using a cubic spline function to estimate the gradient), and an exponential model was used to fit the calculated conductivity-tension curves to obtain hydraulic conductivity parameter values. The spatial and temporal variability of wetness, tension, saturated hydraulic conductivity and pore-size distribution parameters, and texture at the 0.3-m depth were examined using geostatistical techniques.The exponential model was found to inadequately describe the hydraulic conductivity/tension relationship for the full range of tension, particularly in the tension range near saturation. The derived values of the saturated hydraulic conductivity parameter were much greater than expected and do not correspond to reasonable saturated hydraulic conductivity values.All of the soil parameters studied exhibited large spatial variability horizontally and vertically in the field. Ranges of dependence determined from semivariogram analysis over the 44-day drainage period are 3–32 m for wetness, 6–34 m for soil water tension, 5–35 m for natural log of saturated hydraulic conductivity parameters, 5–11 m for pore-size distribution parameter, and 8–24 m for percent sand, silt and clay at the 0.3 m depth. An alternate hole-effect model is suggested to describe the texture semivariograms.It was determined that the variance of volumetric water content generally increased at each depth over the measured time periods, which is consistent with certain past field studies and a stochastic analysis of unsaturated flow in heterogeneous soils. Future research is recommended relating soil texture to soil hydrologic parameters with the goal of predicting soil behavior with less extensive sampling schemes.     

Development and application of a Lagrangian model to determine the origins of ozone episodes in the UK

This paper describes the further development and application of the Edinburgh–Lancaster Model for Ozone (ELMO). We replace straight-line back-trajectories with trajectories and associated meteorology supplied by the US National Oceanic and Atmospheric Administration Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) service to allow more realistic modelling of specific UK ozone episodes. We call this ELMO-2. Model performance is rigorously tested against observed ozone concentrations for two episodes recorded across 14 rural UK monitoring stations during the spring and summer of 1995. For both episodes, the afternoon concentrations (usually coinciding with the daily maxima) are captured well by the model and the diurnal ozone cycle is reproduced, although the amplitude in concentrations is generally smaller than the observed. The summer episode is investigated further through indicator species analysis and source attribution, and found to be mainly VOC-limited. European emissions account for the majority of ozone production. We demonstrate how improved modelling leads to better understanding of regional and local ozone production across the UK under episodic conditions.     

Spatial characterization of the Baltic sea drainage basin and its unmonitored catchments

We present an updated, harmonized hydrologic base map of the entire Baltic Sea Drainage Basin (BSDB), including 634 subdrainage basins. The updated map has a level of detail approximately 5 to 10 times higher than the current standard and includes various spatial-aggregation possibilities of relevance for water management. All 634 subdrainage basins and their various spatial aggregations are characterized in terms of population, land cover, drainage density, and slope. We identify, quantify, and characterize, in particular, drainage basins that are unmonitored with regard to the combination of water-flow and nutrient-concentration measurements needed to monitor coastal nutrient and pollutant loading. Results indicate that out of a total BSDB population of 84 239 000 in 2002, 24% lived in unmonitored coastal drainage basins that cover 13% of the total BSDB area. A more detailed analysis of Swedish catchments indicates that Sweden has a particularly large proportion of unmonitored coastal catchment areas (20% of the total Swedish area) with high population pressures (55% of the total Swedish population), when compared with average conditions for the whole BSDB. In general, the investigated characteristics of unmonitored coastal basins vary and differ largely from those in adjacent monitored drainage basins within the BSDB.     

Development of a new model for batch sedimentation and application to secondary settling tanks design.

Assuming that settling takes place in two zones (a constant rate zone and a variable rate zone), a model using four parameters accounting for the nature of the water-suspension system has been proposed for describing batch sedimentation processes. The sludge volume index (SVI) has been expressed in terms of these parameters. Some disadvantages of the SVI application as a design parameter have been pointed out, and it has been shown that a relationship between zone settling velocity and sludge concentration is more consistent for describing the settling behavior and for design of settling tanks. The permissible overflow rate has been related to the technological parameters of secondary settling tank by simple working equations. The graphical representations of these equations could be used to optimize the design and operation of secondary settling tanks.     

Development and application of a three-dimensional aerosol chemical transport model,PMCAMx

A three-dimensional chemical transport model (PMCAMx) is used to simulate PM mass and composition in the eastern United States for a July 2001 pollution episode. The performance of the model in this region is evaluated, taking advantage of the highly time and size-resolved PM and gas-phase data collected during the Pittsburgh Air Quality Study (PAQS). PMCAMx uses the framework of CAMx and detailed aerosol modules to simulate inorganic aerosol growth, aqueous-phase chemistry, secondary organic aerosol formation, nucleation, and coagulation. The model predictions are compared to hourly measurements of PM_2.5 mass and composition at Pittsburgh, as well as to measurements from the AIRS and IMPROVE networks. The performance of the model for the major PM_2.5 components (sulfate, ammonium, and organic carbon) is encouraging (fractional errors are in general smaller than 50%). Additional improvements are possible if the rainfall measurements are used instead of the meteorological model predictions. The modest errors in ammonium predictions and the lack of bias for the total (gas and particulate) ammonium suggest that the improved ammonia inventory used is reasonable. The significant errors in aerosol nitrate predictions are mainly due to difficulties in simulating the nighttime formation of nitric acid. The concentrations of elemental carbon (EC) in the urban areas are significantly overpredicted. This is a problem related to both the emission inventory but also the different EC measurement methods that have been used in the two measurement networks (AIRS and IMPROVE) and the actual development of the inventory. While the ability of the model to reproduce OC levels is encouraging, additional work is necessary to confirm that that this is due to the right reasons and not offsetting errors in the primary emissions and the secondary formation. The model performance against the semi-continuous measurements in Pittsburgh appears to be quite similar to its performance against daily average measurements in a wide range of stations across the Eastern US. This suggests that the skill of the model to reproduce the diurnal variability of PM_2.5 and its major components is as good as its ability to reproduce the daily average values and also the significant value of high temporal resolution measurements for model evaluation.     

Modelling pesticide volatilization after soil application using the mechanistic model Volt'Air

Volatilization of pesticides participates in atmospheric contamination and affects environmental ecosystems including human welfare. Modelling at relevant time and spatial scales is needed to better understand the complex processes involved in pesticide volatilization. Volt'Air-Pesticides has been developed following a two-step procedure to study pesticide volatilization at the field scale and at a quarter time step. Firstly, Volt'Air-NH₃ was adapted by extending the initial transfer of solutes to pesticides and by adding specific calculations for physico-chemical equilibriums as well as for the degradation of pesticides in soil. Secondly, the model was evaluated in terms of 3 pesticides applied on bare soil (atrazine, alachlor, and trifluralin) which display a wide range of volatilization rates. A sensitivity analysis confirmed the relevance of tuning to K_h. Then, using Volt'Air-Pesticides, environmental conditions and emission fluxes of the pesticides were compared to fluxes measured under 2 environmental conditions. The model fairly well described water temporal dynamics, soil surface temperature, and energy budget. Overall, Volt'Air-Pesticides estimates of the order of magnitude of the volatilization flux of all three compounds were in good agreement with the field measurements. The model also satisfactorily simulated the decrease in the volatilization rate of the three pesticides during night-time as well as the decrease in the soil surface residue of trifluralin before and after incorporation. However, the timing of the maximum flux rate during the day was not correctly described, thought to be linked to an increased adsorption under dry soil conditions. Thanks to Volt'Air's capacity to deal with pedo-climatic conditions, several existing parameterizations describing adsorption as a function of soil water content could be tested. However, this point requires further investigation. Practically speaking, Volt'Air-Pesticides can be a useful tool to make decision about agricultural practices such as incorporation or for the estimation of overall pesticide volatilization rates, and it holds promise for time specific dynamics.     

Pharmaceutical and personal care products in groundwater, subsurface drainage, soil, and wheat grain, following a high single application of municipal biosolids to a field

Dewatered municipal biosolids (DMBs) were applied to a field at a rate of ~22 Mg dw ha(-1) in October 2008. Pharmaceuticals and personal care products (PPCPs) were monitored in groundwater, tile drainage, soil, DMB aggregates incorporated into the soil post-land application, and in the grain of wheat grown on the field for a period of ~1 year following application. Over 80 PPCPs were analyzed in the source DMB. PPCPs selected for in-depth monitoring included: antibiotics (tetracyclines, fluoroquinolones), bacteriocides (triclosan, triclocarban), beta-blockers (atenolol, propranolol, metaprolol), antidepressants (fluoxetine, citalopram, venlafaxine, sertraline), antifungals (miconazole), analgesics (acetaminophen, ibuprofen) and anticonvulsants (carbamazepine). PPCPs in tile were observed twice, ~3 weeks and 2 months post-application. Of all PPCPs measured in tile drainage, only carbamazepine, ibuprofen, acetaminophen, triclosan, triclocarban, venlafaxine, and citalopram were detected (5-74 ng L(-1)). PPCPs were not detected in groundwater >2 m depth below the soil surface, and concentrations above detection limits at 2 m depth were only observed once just after the first rain event post-application. In groundwater, all compounds found in tile, except carbamazepine, acetaminophen and citalopram, were detected (10-19 ng L(-1)). PPCPs were detected in DMB aggregates incorporated in soil up to 1 year post-application, with miconazole and fluoxetine having the lowest percent reductions over 1 year (~50%). For several compounds in these aggregates, concentration declines were of exponential decay form. No PPCPs were detected in the grain of wheat planted post-application on the field. No PPCPs were ever detected in water, soil or grain samples from the reference plot, where no DMB was applied.     

Extractable soil heavy metals following the cessation of biosolids application to agricultural soil

Changes in soil heavy metal extractability following the cessation of biosolids applications were studied in a long-term field experiment. Two anaerobically digested biosolids from wastewater treatment plants in Madrid (Sur and Viveros) were applied to cropland from 1983 to 1990. Soil samples were collected in the 1st, 5th and 9th year after the last biosolids application. Soil pH did not vary significantly after biosolids applications. Organic matter and total heavy metals (Zn, Pb, Cd, Ni, Cr and Cu) concentrations initially increased but then declined over time, mostly after the first 5 years following biosolids application. Metal extracted with DPTA increased in Sur treatments during the 1st year and diminished thereafter. However, in Viveros treatments, heavy metals extracted increased during the 1st year, declined in 1995, and showed a slight increase in 1999. These changes in heavy metal extractability were widely observed in the percentage of extractable metal recovery (EMR). The differences observed in the pattern of the two sources of biosolids applied could be due to the different rates of decomposition of their organic matter.     

Long term remediation of highly polluted acid mine drainage: a sustainable approach to restore the environmental quality of the Odiel river basin

During 20 months of proper operation the full scale passive treatment in Mina Esperanza (SW Spain) produced around 100 mg/L of ferric iron in the aeration cascades, removing an average net acidity up to 1500 mg/L as CaCO₃ and not having any significant clogging problem. Complete Al, As, Cd, Cr, Cu, Ti and V removal from the water was accomplished through almost the entire operation time while Fe removal ranged between 170 and 620 mg/L. The system operated at a mean inflow rate of 43 m³/day achieving an acid load reduction of 597 g·(m² day)⁻¹, more than 10 times higher than the generally accepted 40 g·(m² day)⁻¹ value commonly used as a passive treatment system designing criteria. The high performance achieved by the passive treatment system at Mina Esperanza demonstrates that this innovative treatment design is a simple, efficient and long lasting remediation option to treat highly polluted acid mine drainage.     

Impact of industrial and mine drainage wastes on the heavy metal distribution in the drainage basin and estuary of the Sado River (Portugal)

This paper presents results from a survey of the heavy metal distribution in sediments in the drainage basin and estuary of the Sado River (Portugal). In the drainage basin, heavy metals originate mostly from pyrite outcrop erosion and mining activities (Cd, Zn, Cu and locally Hg, Pg), and also from crust erosion (Sn, Ni, Ti, Zr). These sources are not correlated with the particulate organic carbon (POC) and so the metals are thought to be in inorganic forms in this area. Anthropogenic heavy metal sources (urban and industrial) are found in the lower estuary (Sn, Cd, Hg, Zn, Pb and Cu) along with high POC concentrations. In this zone, these metals are thought to be strongly adsorbed onto organic particles. Furthermore, organo-metallic species are likely to be present, as demonstrated in the case of Sn, since methyl- and butyl-tin species were detected in sediments from this area. This suggests the need for the detection of organo-metallic species to understand the heavy metal geochemical cycles. No long-term changes in metal concentrations are found in sediment cores, except in the middle estuary (Zn, Cu) due to the development of mining activities on an industrial scale in the 1860s.     

Skill and uncertainty of a regional air quality model ensemble

Recently several regional air quality projects were carried out to support the negotiation under the Clean Air For Europe (CAFE) programme by predicting the impact of emission control policies with an ensemble of models. Within these projects, CITYDELTA and EURODELTA, the fate of air quality at the scale of European cities or that of the European continent was studied using several models. In this article we focus on the results of EURODELTA. The predictive skill of the ensemble of models is described for ozone, nitrogen dioxide and secondary inorganic compounds, and the uncertainty in air quality modelling is examined through the model ensemble spread of concentrations.For ozone daily maxima the ensemble spread origin differs from one region to another. In the neighbourhood of cities or in mountainous areas the spread of predicted values does not span the range of observed data, due to poorly resolved emissions or complex-terrain meteorology. By contrast in Atlantic and North Sea coastal areas the spread of predicted values is found to be larger than the observations. This is attributed to large differences in the boundary conditions used in the different models. For NO₂ daily averages the ensemble spread is generally too small compared with observations. This is because models miss highest values occurring in stagnant meteorology in stable boundary layers near cities. For secondary particulate matter compounds the simulated concentration spread is more balanced, observations falling nearly equiprobably within the ensemble, and the spread originates both from meteorology and aerosol chemistry and thermodynamics.     

Development of a black carbon-inclusive multi-media model: application for PAHs in Stockholm

A multi-media model was developed for predicting the fate of organic chemicals in the Greater Stockholm Area, Sweden, and applied to selected polycyclic aromatic hydrocarbons (PAHs). Although urban models have been previously developed, this model is novel in that it includes sorption to pyrogenically-derived particles, commonly termed "black carbon" (BC), within the model structure. To examine the influence of BC sorption on environmental fate of PAHs, two versions of the model were generated and run: one in which sorption to BC was included and one in which BC sorption was excluded. The inclusion of BC sorption did not cause any significant variations to air levels, but it did cause an average 20-30% increase in sediment concentrations related to increased sediment solids partitioning. The model also predicted reduced advective losses out of the model domain, as well as chemical potential to diffuse from sediments, whilst total chemical inventory increased. In all cases, the lighter PAHs were more affected by BC inclusion than their heavier counterparts. We advocate the addition of sorption to BC in future multi-media fate and exposure models, which as well as influencing fate will also alter (lower) chemical availability and, thus, wildlife exposure to hydrophobic chemicals. A quantification of the latter was derived with the help of the soot-inclusive model version, which estimated a lowering of dissolved water concentrations between five and >200 times for the different PAHs of this study.     

Study of water quality response to water transfer patterns in the receiving basin and surrogate model

Environmental Science and Pollution Research - The spatio-temporal response of water quality in the receiving basins to water transfer remains unclear when considering more practical factors....     

An optimal model and its application for the management of municipal solid waste from regional small cities in China

Based on the basic characteristics of municipal solid waste (MSW) from regional small cities in China, some optimal management principles have been put forward: regional optimization, long-term optimization, and integrated treatment/disposal optimization. According to these principles, an optimal MSW management model for regional small cities is developed and provides a useful method to manage MSW from regional small cities. A case study application of the optimal model is described and shows that the optimal management scenarios in the controlling region can be gained, adequately validating and accounting for the advantages of the optimal model.     

Identifying sources of soil inorganic pollutants on a regional scale using a multivariate statistical approach: role of pollutant migration and soil physicochemical properties

Principal components analysis (PCA) and correlation analysis were used to estimate the contribution of four components related to pollutant sources on the total variation in concentrations of Cu, Zn, Pb, Cd, As, Se, Hg, Fe and Mn in surface soil samples from a valley in east China with numerous copper and zinc smelters. Results indicate that when carrying out source identification of inorganic pollutants their tendency to migrate in soils may result in differences between the pollutant composition of the source and the receptor soil, potentially leading to errors in the characterization of pollutants using multivariate statistics. The stability and potential migration or movement of pollutants in soils must therefore be taken into account. Soil physicochemical properties may offer additional useful information. Two different mechanisms have been hypothesized for correlations between soil heavy metal concentrations and soil organic matter content and these may be helpful in interpreting the statistical analysis.     

Development and application of kinetic model on biological anoxic/aerobic filter

An up-flow biological anoxic filter (BANF) has been developed to achieve high removal performance of suspended solids and BOD removal as well as nitrogen. With a view to understand treatment mechanisms, we developed a filtration model that incorporates filtration, deposit scoring and biological reactions simultaneously. The biological reactions consist of four types of reaction; dissolution of organic particles; utilization of dissolved organic matter; denitrification; and self-degradation of bacteria. Whereas the reactor is generally assumed to be a plug flow reactor in the filtration model, it is assumed a continuous-flow stirred tank reactor (CSTR) in the model of biological reactions. The hydrodynamics is supposed that the filter bottom (the portion sludge settled) is a CSTR and the filter bed (the portion filled with filter media) consists of number of CSTR of equal size arranged in series. The model obtained in this study was verified and simulated using experimental results taken from a pilot-scale plant and predicted the experimental data well, applying to design and operate BANF.     

Development of a fuzzy-stochastic nonlinear model to incorporate aleatoric and epistemic uncertainty

Site uncertainties significantly influence groundwater flow and contaminant transport predictions. Aleatoric and epistemic uncertainty are both identified in site characterization and represented using proper uncertainty theories. When one theory best represents one parameter whereas a different theory may be more suitable for another parameter, the hybrid propagation of aleatoric (random) and epistemic (nonrandom) uncertainties will occur. The computational challenges of joint propagation of aleatoric and epistemic uncertainty through groundwater flow and contaminant transport models are significant. A fuzzy-stochastic nonlinear model was developed in this paper to incorporate these two types of uncertain site information and reduce the computational cost. The results show that (1) the computational cost using the nonlinear model is reduced compared with that of using the sparse grid algorithm and Monte Carlo methods; (2) the uncertainty of hydraulic conductivity (K) significantly influences the water head and solute distribution at the observation wells compared to other uncertain parameters, such as the storage coefficient and the distribution coefficient (K_d); and (3) the combination of multiple uncertain parameters substantially affects the simulation results. Neglecting site uncertainties may lead to unrealistic predictions.     

Land application of tylosin and chlortetracycline swine manure: Impacts to soil nutrients and soil microbial community structure

The land application of aged chortetracycle (CTC) and tylosin-containing swine manure was investigated to determine associated impacts to soil microbial respiration, nutrient (phosphorus, ammonium, nitrate) cycling, and soil microbial community structure under laboratory conditions. Two silty clay loam soils common to southeastern South Dakota were used. Aerobic soil respiration results using batch reactors containing a soil-manure mixture showed that interactions between soil, native soil microbial populations, and antimicrobials influenced CO₂ generation. The aged tylosin treatment resulted in the greatest degree of CO₂ inhibition, while the aged CTC treatment was similar to the no-antimicrobial treatment. For soil columns in which manure was applied at a one-time agronomic loading rate, there was no significant difference in soil-P behavior between either aged CTC or tylosin and the no-antimicrobial treatment. For soil-nitrogen (ammonium and nitrate), the aged CTC treatment resulted in rapid ammonium accumulation at the deeper 40cm soil column depth, while nitrate production was minimal. The aged CTC treatment microbial community structure was different than the no-antimicrobial treatment, where amines/amide and carbohydrate chemical guilds utilization profile were low. The aged tylosin treatment also resulted in ammonium accumulation at 40 cm column depth, however nitrate accumulation also occurred concurrently at 10 cm. The microbial community structure for the aged tylosin was also significantly different than the no-antimicrobial treatment, with a higher degree of amines/amides and carbohydrate chemical guild utilization compared to the no-antimicrobial treatment. Study results suggest that land application of CTC and tylosin-containing manure appears to fundamentally change microbial-mediated nitrogen behavior within soil A horizons.     

Land application of tylosin and chlortetracycline swine manure: Impacts to soil nutrients and soil microbial community structure

The land application of aged chortetracycle (CTC) and tylosin-containing swine manure was investigated to determine associated impacts to soil microbial respiration, nutrient (phosphorus, ammonium, nitrate) cycling, and soil microbial community structure under laboratory conditions. Two silty clay loam soils common to southeastern South Dakota were used. Aerobic soil respiration results using batch reactors containing a soil-manure mixture showed that interactions between soil, native soil microbial populations, and antimicrobials influenced CO(2) generation. The aged tylosin treatment resulted in the greatest degree of CO(2) inhibition, while the aged CTC treatment was similar to the no-antimicrobial treatment. For soil columns in which manure was applied at a one-time agronomic loading rate, there was no significant difference in soil-P behavior between either aged CTC or tylosin and the no-antimicrobial treatment. For soil-nitrogen (ammonium and nitrate), the aged CTC treatment resulted in rapid ammonium accumulation at the deeper 40cm soil column depth, while nitrate production was minimal. The aged CTC treatment microbial community structure was different than the no-antimicrobial treatment, where amines/amide and carbohydrate chemical guilds utilization profile were low. The aged tylosin treatment also resulted in ammonium accumulation at 40 cm column depth, however nitrate accumulation also occurred concurrently at 10 cm. The microbial community structure for the aged tylosin was also significantly different than the no-antimicrobial treatment, with a higher degree of amines/amides and carbohydrate chemical guild utilization compared to the no-antimicrobial treatment. Study results suggest that land application of CTC and tylosin-containing manure appears to fundamentally change microbial-mediated nitrogen behavior within soil A horizons.     

Development and application of a regional-scale atmospheric mercury model based on WRF/Chem: a Mediterranean area investigation

The emission, transport, deposition and eventual fate of mercury (Hg) in the Mediterranean area has been studied using a modified version of the Weather Research and Forecasting model coupled with Chemistry (WRF/Chem). This model version has been developed specifically with the aim to simulate the atmospheric processes determining atmospheric Hg emissions, concentrations and deposition online at high spatial resolution. For this purpose, the gas phase chemistry of Hg and a parametrised representation of atmospheric Hg aqueous chemistry have been added to the regional acid deposition model version 2 chemical mechanism in WRF/Chem. Anthropogenic mercury emissions from the Arctic Monitoring and Assessment Programme included in the emissions preprocessor, mercury evasion from the sea surface and Hg released from biomass burning have also been included. Dry and wet deposition processes for Hg have been implemented. The model has been tested for the whole of 2009 using measurements of total gaseous mercury from the European Monitoring and Evaluation Programme monitoring network. Speciated measurement data of atmospheric elemental Hg, gaseous oxidised Hg and Hg associated with particulate matter, from a Mediterranean oceanographic campaign (June 2009), has permitted the model’s ability to simulate the atmospheric redox chemistry of Hg to be assessed. The model results highlight the importance of both the boundary conditions employed and the accuracy of the mercury speciation in the emission database. The model has permitted the reevaluation of the deposition to, and the emission from, the Mediterranean Sea. In light of the well-known high concentrations of methylmercury in a number of Mediterranean fish species, this information is important in establishing the mass balance of Hg for the Mediterranean Sea. The model results support the idea that the Mediterranean Sea is a net source of Hg to the atmosphere and suggest that the net flux is ≈30 Mg year^?1 of elemental Hg.