Forecasting leachate generation from pilot woodchip stockpiles using a three-dimensional transient flow model.

Leachate generation from open stockpiles of recycled woodchip materials is potentially harmful to aquatic ecosystems. There is growing interest in using numerical models to simulate leachate generation from outdoor piles, but this requires information about the hydraulic properties of the materials. The objectives of this study were to simulate leachate from woodchip piles with the numerical model HYDRUS-3D and to optimize subsets of parameters for single (SPM) and dual (DPM) pore flow models with the Bayesian Markov Chain Monte Carlo algorithm DREAMZS. Three experimental piles, each approximately 30 m3, were setup with mixtures of either once (coarse) or twice (fine) ground woodchips. Leachate continuously collected over a period of six months was similar across piles. As a result, subsets of optimized flow parameters for the coarse and fine woodchips were not different. Leachate predictions by the two pore flow models were similar and agreed reasonably with the field measurements, as indicated by Nash-Sutcliffe efficiency values greater than 0.6. This result suggests the simpler SPM is adequate for field predictions of leachate. However, leachate was consistently under-predicted by both pore models by 13-27% during rainfall events with more than 1 cm in 6 h. The optimized flow models can be used as a tool for studying pile management strategies.

Modeling chlorine-produced oxidant demand and dilution in chlorinated combined sewer overflow discharges.

Combined sewer overflow (CSO) water introduces pathogens to receiving waters. To control pathogenic releases, chlorine may be added to disinfect CSO water. The added chlorine may react with water constituents to form oxidative species known as chlorine-produced oxidants (CPO). CPO are the sum of free and combined oxidative species that form upon adding free chlorine-bearing compounds (e.g. gaseous chlorine or hypochlorite) to water. CPO discharge is often regulated by governing agencies. Current methods to model CPO behavior do not account for CPO decay and dilution simultaneously in receiving water. This study creates a novel model for CPO demand and dilution in receiving water from chlorinated effluent in order to determine site-specific practices for implementation of a CSO water disinfection regime. To do this, representative receiving water was collected and dosed with 1, 2, and 4 mg/L chlorine. The residual chlorine was measured at intervals up to 30 min after dosing. The immediate and subsequent chlorine demand was calculated, with the subsequent demand modeled by simultaneous application of dilution and decay using pseudo-first-order decay kinetics. A comparison of model calculations indicates that application of dilution before decay underestimates CPO demand, while application of decay before dilution overestimates CPO demand.

Design of a GIS-based rating protocol to assess the potential for landfill closure using dredge material in post Hurricane Sandy New Jersey.

New Jersey is rapidly running out of capacity for storage of dredged material. A potential solution to this lack of storage space is to remove and reuse the dredged material for some beneficial use. Results from a Rutgers University project performed for the New Jersey Department of Transportation, Office of Maritime Resources, designed to assess the potential for closure of New Jersey landfills using dredge material from existing Confined Disposal Facilities (CDFs) are presented and discussed. The project included an update of the existing NJDEP landfill database, the development of a rating system to identify landfills with the highest potential to utilize dredged material for their closure, and the identification and preliminary investigation of the top candidate landfills based on this rating system.

Source Apportionment of Atmospheric Polychlorinated Biphenyls in New Jersey 1997-2011.

Concentrations of polychlorinated biphenyls (PCBs) in the Delaware River currently exceed the Water Quality Criteria of 16 pg/L for the sum of PCBs due in part to atmospheric deposition. The purpose of this work was to use a source apportionment tool called Positive Matrix Factorization (PMF) to identify the sources of PCBs to the atmosphere in this area and determine whether their concentrations are declining over time. The data set was compiled by the Delaware Atmospheric Deposition Network (DADN) from samples taken in Camden, NJ from 1999 to 2011 and New Brunswick, NJ from 1997 to 2011. The PMF analysis revealed four resolved factors at each site. The factors that dominate the PCB burden in the atmosphere at both Camden and New Brunswick resemble Aroclor 1242. These factors declined in concentration during some portions of the monitoring period, but this decline slowed or stopped during 2003-2011. None of the factors displayed consistent declines in concentration throughout the monitoring periods, and some factors actually increased in concentration during some periods. This suggests natural attenuation alone will not control atmospheric PCB concentrations, and additional efforts are needed to control PCB atmospheric emissions as well as the numerous other sources of PCBs to the estuary.

Characterization of wood mulch and leachate/runoff from three wood recycling facilities.

Large-scale open storage of wood mulch is common practice at wood recycling facilities. During rain and snow melt, leachate with soluble compounds and suspended particles is released from mulch stockpiles. The objective of this study was to determine the quality of leachate/runoff from wood recycling facilities to evaluate its potential to contaminate receiving waterbodies. Wood mulch (n = 30) and leachate/runoff (n = 26) samples were collected over 1.5 years from three wood recycling facilities in New Jersey, USA. Differences by site were found (p < 0.05) for most of the 21 constituents tested in the solid wood mulch samples. Biochemical oxygen demand (range <20-3000 mg/L), chemical oxygen demand (134-6000 mg/L) and total suspended solids (69-401 mg/L) median concentrations of the leachate/runoff samples were comparable to those of untreated domestic wastewater. Total Kjeldahl N, total P and fecal coliform median values were slightly lower than typical wastewater values. Dose-response studies with leachate/runoff samples using zebrafish (Danio rerio) embryos showed that mortality and developmental defects typically did not occur even at the highest concentration tested, indicating low toxicity, although delayed development did occur. Based on this study, leachate/runoff from wood recycling facilities should not be released to surface waters as it is a potential source of organic contamination and low levels of nutrients. A study in which runoff from a controlled drainage area containing wood mulch of known properties is monitored would allow for better assessment of the potential impact of stormwater runoff from wood recycling facilities.

Symbolic regression of upstream, stormwater, and tributary E. coli concentrations using river flows.

Symbolic regression was used to model E. coli concentrations of upstream boundary, tributaries, and stormwater in the lower Passaic River at Paterson, New Jersey. These models were used to simulate boundary concentrations for a water quality analysis simulation program to model the river. River flows from upstream and downstream boundaries of the study area were used as predictors. The symbolic regression technique developed a variety of candidate models to choose from due to multiple transformations and model structures considered. The resulting models had advantages such as better goodness-of-fit statistics, reasonable bounds to outputs, and smooth behavior. The major disadvantages of the technique are model complexity, difficulty to interpret, and overfitting. The Nash-Sutcliffe efficiencies of the models ranged from 0.61 to 0.88, and they adequately captured the upstream boundary, tributary, and stormwater concentrations. The results suggest symbolic regression can have significant applications in the areas of hydrologic, hydrodynamic, and water quality modeling.

Pathogen transport and fate modeling in the Upper Salem River Watershed using SWAT model.

Simulation of the fate and transport of pathogen contamination was conducted with SWAT for the Upper Salem River Watershed, located in Salem County, New Jersey. This watershed is 37 km(2) and land uses are predominantly agricultural. The watershed drains to a 32 km stretch of the Salem River upstream of the head of tide. This strech is identified on the 303(d) list as impaired for pathogens. The overall goal of this research was to use SWAT as a tool to help to better understand how two pathogen indicators (Escherichia coli and fecal coliform) are transported throughout the watershed, by determining the model parameters that control the fate and transport of these two indicator species. This effort was the first watershed modeling attempt with SWAT to successfully simulate E. coli and fecal coliform simultaneously. Sensitivity analysis has been performed for flow as well as fecal coliform and E. coli. Hydrologic calibration at six sampling locations indicate that the model provides a "good" prediction of watershed outlet flow (E = 0.69) while at certain upstream calibration locations predictions are less representative (0.32 < E < 0.70). Monthly calibration and validation of the pathogen transport and fate model was conducted for both fecal coliform (0.07 < E < 0.47 and -0.94 < E < 0.33) and E. coli (0.03 < E < 0.39 and -0.81 < E < 0.31) for the six sampling points. The fit of the model compared favorably with many similar pathogen modeling efforts. The research contributes new knowledge in E. coli and fecal coliform modeling and will help increase the understanding of sensitivity analysis and pathogen modeling with SWAT at the watershed scale.

Impact of sea level rise on tide gate function.

Sea level rise resulting from climate change and land subsidence is expected to severely impact the duration and associated damage resulting from flooding events in tidal communities. These communities must continuously invest resources for the maintenance of existing structures and installation of new flood prevention infrastructure. Tide gates are a common flood prevention structure for low-lying communities in the tidal zone. Tide gates close during incoming tides to prevent inundation from downstream water propagating inland and open during outgoing tides to drain upland areas. Higher downstream mean sea level elevations reduce the effectiveness of tide gates by impacting the hydraulics of the system. This project developed a HEC-RAS and HEC-HMS model of an existing tide gate structure and its upland drainage area in the New Jersey Meadowlands to simulate the impact of rising mean sea level elevations on the tide gate's ability to prevent upstream flooding. Model predictions indicate that sea level rise will reduce the tide gate effectiveness resulting in longer lasting and deeper flood events. The results indicate that there is a critical point in the sea level elevation for this local area, beyond which flooding scenarios become dramatically worse and would have a significantly negative impact on the standard of living and ability to do business in one of the most densely populated areas of America.

Mass transfer coefficients for volatilization of polychlorinated biphenyls from the Hudson River, New York measured using micrometeorological approaches.

Air-water exchange is an important process controlling the fate of many organic chemicals in the environment. Modeling this process is hampered by the lack of direct observations. Thus, the purpose of this work was to derive direct measurements of the mass transfer coefficients for air-water exchange (v(aw)) of polychlorinated biphenyls (PCBs) that may be used to check the validity of values derived from tracer gas experiments. v(aw) values for PCBs were determined using previously published turbulent fluxes divided by the corresponding dissolved phase concentrations. The median v(aw) values for each homolog decreased with increasing molecular weight and ranged from 0.29 for hexachlorobiphenyls to 2.2 m d(-1) for monochlorobiphenyls with a propagated uncertainty of about 70%, lower than in previous studies. Due to relatively low wind speeds and possible sorption of PCBs to colloids, these numbers may be biased low. These field measurements of v(aw) differ by as much as a factor of 23 from predictions based on the widely-used Whitman two-film model. Therefore a new formulation for the calculation of v(aw) based on field measurements is needed. This study demonstrates that micrometeorological approaches are a viable option for the measurement of v(aw) for hydrophobic organics such as PCBs and should be used to generate enough field data on the air-water exchange of hydrophobic organics to allow the development of new predictive models.

Fluxes of polychlorinated biphenyls volatilizing from the Hudson River, New York measured using micrometeorological approaches.

This study represents the first time that a micrometeorological technique, using turbulent transport measurements, has been used to determine the direction and magnitude of air-water exchange of polychlorinated biphenyls (PCBs). The study was conducted during July 2008 on the Hudson River estuary near the Tappan Zee Bridge, which is the site of some of the most serious PCB contamination in the world. Gas-phase ΣPCB concentrations measured at two heights above the water column averaged 1.1 ng m(-3), and concentrations were usually lower in the upper air sample, indicating net transport of PCBs from the water column to the air. Volatilization PCB fluxes were calculated using the modified Thornthwaite-Holzman equation. Values of friction velocity and atmospheric stability were calculated using the Aerodynamic Gradient and Eddy Correlation techniques. The PCB fluxes were corrected for changes in atmospheric stability using the atmospheric stability factor of water vapor (ϕ(w)) calculated from empirical formulations which ranged from 1.0 to 3.2 (neutral to stable atmospheric boundary layer conditions). Vertical ΣPCB fluxes ranged from +0.5 µg m(-2) d (-1) to +13 µg m(-2) d (-1). Mono- through tri-homologues accounted for about half of ΣPCB fluxes, with tetra- through hexa-homologue accounting for the other half. This work demonstrates the utility of a micrometeorological approach to measuring the air-water exchange of organic contaminants.

Comparison of kriging and cokriging for the geostatistical estimation of specific capacity in the Newark Basin (NJ) aquifer system.

Groundwater is a major water source in New Jersey; hence, accurate hydrogeologic data are extremely important. However, most measured data have inadequate spatial density and their locations are often clustered. Our study focuses on implementing geostatistical methods to generate the spatial distribution of specific capacity over the Newark Basin in New Jersey. Two geostatistical methods, ordinary kriging and cokriging, were employed and compared. Ordinary kriging was employed to estimate the spatial distribution of specific capacity by using measured values. Cokriging incorporated the spatial variability of fracture density into the estimation with the spatial variability of specific capacity, as groundwater flow in fractured rock aquifers depends on the fracture characteristics in the Newark Basin. Results indicate that cokriging manifested substantial improvements over ordinary kriging including a larger areal coverage, a more detailed variation of specific capacity, and reduction in the variance of its estimates.

Comparison of a novel profile method to standard chamber methods for measurement of sediment oxygen demand.

A methodology is presented to determine the impact of flow rate upon sediment oxygen demand (SOD) based upon dissolved oxygen transport through the logarithmic boundary layer in stream systems. Previous work has used profile methodology to estimate atmospheric fluxes of pollutants from sediment, and similar principles are applied in this study. Chamber and profile SOD measurements were collected on July 21, 2009 in the Millstone River in Hillsborough, NJ and on July 22 and 28, 2009 in the Lawrence Brook in Milltown, NJ. The two systems were installed 2 meters apart laterally across the stream to measure SOD simultaneously. A total of 7 chamber measurements and 50 profile measurements were collected over 3 days. Chamber SOD measurements in the Lawrence Brook varied from 3.6 to 13.0 g/m(2)/day and had a mean of 5.0 g/m(2)/day. Concurrent profile SOD measurements varied from 1.3 to 13.5 g/m(2)/day and had a mean of 7.16 g/m(2)/day. In the Millstone River, the single chamber measurement was 4.6 g/m(2)/day while the profile measurements varied from 0.5 to 2.2 g/m(2)/day with a mean of 1.32 g/m(2)/day. The measurements made via the profile and chamber methods were found to be in relative agreement. A linear relationship between friction velocity and stream SOD was observed.

Distribution of polychlorinated biphenyls in the Newark Bay Estuary.

As part of the NJ Toxics Reduction Workplan for NY/NJ Harbor, ambient water samples were collected at 15 locations along the tidal portions of the Hackensack, Passaic, Raritan, Rahway and Elizabeth Rivers, and in Newark Bay, the Arthur Kill, and Kill van Kull. A Trace Organics Platform Sampler was used to collect a total of 73 dissolved phase and 73 suspended sediment phase samples between June 2000 and May 2002. These samples were analyzed for spatial and wet versus dry weather trends in the 114 polychlorinated biphenyls (PCBs; modified USEPA Method 1668A). Mean total PCB concentrations at the sampling locations ranged between 3.45 and 56 ng/L. PCB homolog groups distribution patterns at the sampling locations are presented.

Mercury emissions from cement-stabilized dredged material.

Upland placement of dredged materials from navigation channels in the New York/New Jersey Harbor is currently being used to manage sediments deemed inappropriate for open water disposal. Although upland placement sites are equipped with engineering controls (leachate collection and/or barrier walls), little is known of the potential impacts of this approach to air quality. The aim of this study was to estimate the flux of mercury to the atmosphere from New York/New Jersey Harbor stabilized dredged material (SDM) that was used for land reclamation at a site in northeastern New Jersey. Total gaseous mercury (TGM) was measured at a site receiving SDM in August and October 2001 and May and November 2002. TGM was also monitored at an urban reference site 3.5 km west of the SDM site in September 2001 and from February 2002 to July 2002 and from October 2002 to February 2003. The concentration of TGM at the urban reference site averaged 2.2 +/- 1.1 ng m(-3), indicating some local contribution to the Northern Hemisphere background. TGM concentrations exhibited seasonality with the highest values in summer (3.3 +/- 2.1 ng m(-3) in June 2002) and the lowest in winter (1.7 +/- 0.6 ng m(-3) in January 2003). TGM concentrations at the SDM placement site ranged from 2 to 7 ng m(-3) and were significantly higher (p < 0.001) than those at the urban reference site. Sediment-air fluxes of Hg at the SDM placement site estimated by the micrometeorological technique ranged from -13 to 1040 ng m(-2) h(-1) (sediment to air fluxes being positive) and were significantly correlated to solar radiation (r2 = 0.81). The estimated contribution of Hg emissions from land-applied SDM to local TGM concentrations was found to be negligible (<4%). However, the estimated annual volatilization rate of TGM atthe SDM site (130 kg y(-1))was comparable to those of other industrial sources in New Jersey (140-450 kg y(-1)).