Date of Award

1-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Duke Ophori

Committee Member

Clement Alo

Committee Member

Huan Feng

Committee Member

Yang Deng

Committee Member

Solomon Gbondo-Tugbawa

Abstract

Groundwater deterioration has emerged as a pressing global concern, with widespread observations of declining water quality in various regions. The predominant cause of this deterioration is attributed to anthropogenic activities, which are deeply intertwined with daily human practices that contaminate water resources. Over the decades, many forested and wetland areas have been converted mainly for increased urbanization and industrialization use in northern New Jersey. The region’s watershed, already characterized as a low-yield aquifer, is facing deterioration because of continuous change in land cover. Anthropogenic activities aimed at providing solutions to problems, such as food scarcity, icy roads during the winter season, among others, have in turn created a form of harm to the environment. Fertilizers used to enhance agricultural productivity, and road deicing salts used to melt icy surfaces during the winter season, are carried by runoff into water resources. The use of salt for deicing purposes has tripled in the last four decades. The infiltration of salt-laden water into groundwater results in contamination of the freshwater, and changes to groundwater speciation. The detrimental impact of salt constituents on the environment necessitates increased attention to this often-overlooked pollutant. Effective groundwater management relies on regular monitoring and assessment of groundwater composition to ensure and maintain its quality. In light of this, conducting an extensive study to address water quality issues in northern New Jersey has become a pressing imperative, providing a valuable understanding for effective groundwater management. This dissertation describes an integrated approach to groundwater management in northern New Jersey. It is a comprehensive assessment of the effects of contaminants on available freshwater quality, focusing on groundwater salinization dynamics, hydrogeochemical speciation patterns, spatial distribution of water quality, and groundwater transport mechanisms across multiple watershed management areas (WMAs) in northern New Jersey, in a way that is hitherto unknown to the author. For the first time, a regression equation is developed, capable of estimating groundwater’s specific conductance (salinity) from available major-ion concentrations in areas where data are unavailable in northern New Jersey. Following a detailed hydrogeochemical analysis of the data, a spatiotemporal freshwater distribution map of northern New Jersey was produced. A simulation of the hydrodynamics of groundwater quality was then performed. The dissertation addresses these factors in five different stages that are focused on providing a comprehensive assessment of the effects of contaminants on available freshwater quality. First, major ions present in the water were used to estimate groundwater salinity. Specific conductance provided valuable insights into the status of water quality and salinity level. By estimating specific conductance values, it has been possible to assess salinity values, even in aquifers where data are scarce, thereby helping in informed decision-making by stakeholders seeking to improve the water quality. A regression model was developed to predict groundwater salinity in land-use watersheds across northern New Jersey using existing data on major cations and anions. The results show that Ca, K, Mg, SO4, Cl, and HCO3ions are the most useful ions for estimating salinity in the region. However, for parsimony, Ca and Cl were selected for the best model. The model’s performance is judged to be exceptional, with a low Root Mean Square Error (RMSE) value and a coefficient of determination (R2) of 90%. Second, an extensive hydrogeochemical assessment was carried out with the aim of characterizing groundwater quality and suitability for various uses within the northern New Jersey non-coastal plains. This study explored the use of a multivariate statistical approach. A Principal Component Analysis (PCA) on available groundwater data indicated a complex interplay between natural processes and anthropogenic activities influencing the geochemical composition of groundwater during four temporal sampling cycles. Various water quality indices were used to determine the suitability of the groundwater for irrigation and drinking purposes. The analysis revealed significant variations in hydrogeochemical parameters, with specific conductance values reflecting the influence of land use. This was most pronounced in the more urbanized Northeast region where anthropogenic activities, such as deicing salt use and sewage overflow, appeared to elevate ion concentrations. Major ion concentrations, including Ca, Mg, Na, K, Cl, SO4, and HCO3, identified varied sources and fluctuating trends through time, influenced by geogenic processes and anthropogenic imprints. The results revealed that the hydrogeochemical composition is mostly calcium-bicarbonate dominant, but there seems to be a shift towards other water types, like Na-Cl, owing to anthropogenic influences. The Northwest watershed region was more associated with agricultural activities, while the Northeast was linked to deicing salt application and municipal sewage. Irrigation water quality indices revealed fluctuating suitability across all the regions. While most of the water is deemed suitable for irrigation, challenges such as hardness, salinity, and sodium levels in certain regions highlighted the importance of careful water management practices. In general, the system’s hydrochemistry is controlled by geological processes with some influence from anthropogenic activities. Third, a visual pictorial spatial and temporal distribution of available freshwater across northern New Jersey watersheds was developed using a geostatistical model with specific conductance values from measured locations. The model predicted salinity levels and mapped the extent of freshwater coverage across the watershed regions. The spatial patterns of groundwater quality were analyzed using the kriging interpolation technique. This geostatistical approach creates a detailed map from sampled points, identifying the optimal semivariogram model for the groundwater data. The spatial analysis revealed groundwater quality in the Northeast watershed region is the most impacted, and freshwater coverage in the region revealed a disturbing trend: a steady decline with time after four sampling time cycles, from 1999 to 2018. An overlay of highways and major roads on the generated freshwater distribution map revealed that the fluctuating groundwater quality during the sampling periods is closely associated with rapid change in land use towards urbanization and application of deicing salts on the large surface area of the road network across northern New Jersey. Fourth, groundwater transport dynamics in parts of the Brunswick aquifer in northern New Jersey were simulated in order to examine how the groundwater quality, salinity, and contamination may move and be redistributed now and in the future. Guided by the findings from the preceding study, which mapped fluctuating spatial and temporal freshwater availability across northern New Jersey watersheds, this study focused on the lower Passaic Water Management Area (WMA), an area distinguished by elevated salinity levels. The study area, characterized as a 'typical hydrogeologic environment of northern New Jersey,' is located in a predominantly urban region and includes Montclair State University (MSU) and its environs. Notably, this area exhibits elevated salinity levels, making it an ideal location for transport analysis. The area is representative of the highly saline northeast region, providing a unique opportunity to investigate the worst-case scenario in the watershed region. In this study, a numerical model was developed to simulate the advective transport of contaminants (chloride particles) in the Brunswick aquifer, using the MODFLOW code in the Groundwater Modeling System (GMS) package. Travel times and distances of chloride particles from points of particle introduction (recharge areas) to discharge points (of typical groundwater flow systems) were determined using the MODPATH code. Results from the groundwater model revealed that the groundwater quality, salinity, or contamination, mimicking the availability and distribution of freshwater, can fluctuate within a time period of four to ten years in a typical hydrogeologic environment of northern New Jersey. Lastly, a groundwater contaminant transport model was developed to simulate the transport of deicing salt constituents (chloride ions) in the Brunswick aquifer, using chloride as a surrogate for other contaminants in the region due to chloride’s conservative attributes. The model was developed using the MODFLOW code, coupled with the solute transport code, MT3DMS. The model was used to predict the potential plume behavior, concentration distribution, and travel location and time of chloride ions in the typical hydrogeologic environment of northern New Jersey. Analysis from the transport model revealed that substantial concentrations of chloride (> 250mg/L), mimicking deicing salts, can migrate spatially and temporally within the typical environment in 5 to 79 years.

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