Exploring spatial and temporal symptoms of the freshwater salinization syndrome in a rural to urban watershed.

The freshwater salinization syndrome (FSS), a concomitant watershed-scale increase in salinity, alkalinity, and major-cation, and trace-metal concentrations, over recent decades, has been described for major rivers draining extensive urban areas, yet few studies have evaluated temporal and spatial FSS variations, or causal factors, at the subwatershed scale in mixed-use landscapes. This study examines the potential influence of land-use practices and wastewater treatment plant (WWTP) effluent on the export of major ions and trace metals from the mixed-use East Branch Brandywine Creek watershed in southeastern Pennsylvania, during the 2019 water year. Separate analysis of baseflow and stormflow subsets revealed similar correlations among land-use characteristics and streamwater chemistry. Positive associations between percent impervious surface cover, which ranged from 1.26 % to 21.9 % for the 13 sites sampled, and concentrations of Ca2+, Mg2+, Na+, and Cl- are consistent with road-salt driven reverse cation exchange and weathering of the built environment. The relative volume of upstream WWTP was correlated with Cu and Zn, which may be derived in part from corroded water-conveyance infrastructure; chloride to sulfate ratios (CSMR) ranged from ~6.3 to ~7.7× the 0.5 threshold indicating serious corrosivity potential. Observed exceedances of U.S. Environmental Protection Agency Na+ and Cl- drinking water and aquatic life criteria occurred in winter months. Finally, correlation between percent cultivated cropland and As and Pb concentrations may be explained by the persistence of agricultural pesticides that had been used historically. Study results contribute to the understanding of FSS solute origin, fate, and transport in mixed-use watersheds, particularly those in road salt affected regions. Study results also emphasize the complexity of trace-metal source attribution and explore the potential for FSS solutes to affect human health, aquatic life, and infrastructure.

Metal accumulation in salt marsh soils along the East Coast of the United States.

Coastal salt marshes are depositional environments that can accumulate pollutants introduced to the environment from human activities. Metals are a contaminant of concern in coastal environments due to their longevity and toxicity. We assessed metal concentrations and accumulation rates in nine salt marsh sites along the U.S. East Coast from Maine to Georgia. Following a metal mobility assay in organic-rich and mineral dominated salt marsh soils under aerobic/anaerobic and freshwater/saltwater conditions, we focused on profiles of chromium, nickel, copper, zinc, cadmium, lead, and uranium in two soil cores from each of the nine marshes that had previously been dated using lead-210 radioisotope techniques. We examined how land cover and the spatial distribution of land cover, marsh vertical accretion, and other watershed characteristics correlated with metal concentrations and depth/time-integrated accumulation of metals. We found statistically significant differences in metal concentrations and/or inventories between sites, with accumulation of metals positively correlated with both developed land cover in the watershed and rates of vertical accretion in the tidal marsh. The accumulation of chromium, cadmium, and lead were significantly correlated with developed land cover while the accumulation of chromium, nickel, copper, zinc, and lead were correlated with factors that determine sediment delivery from the landscape (e.g., riverine suspended sediment, soil erodibility in the watershed, and agricultural land cover skewed towards the coast) and measured wetland accretion rates. We observed declines in the concentration of many metals since 1925 at sites along the U.S. East Coast, indicating pollution mitigation strategies have succeeded in reducing metal pollution and delivery to the coastal zone. However, increasing rates of salt marsh vertical accretion over recent decades largely offset reductions in metal concentrations, resulting in rates of metal accumulation in coastal salt marsh soils that have not changed or, in some instances, increased over time.

Long-term impacts of impervious surface cover change and roadway deicing agent application on chloride concentrations in exurban and suburban watersheds.

Roadway deicing agents, including rock salt and brine containing NaCl, have had a profound impact on the water quality and aquatic health of rivers and streams in urbanized areas with temperate climates. Yet, few studies evaluate impacts to watersheds characterized by relatively low impervious surface cover (ISC; < 15 %). Here, we use long-term (1997-2019), monthly streamwater quality data combined with daily streamflow for six exurban and suburban watersheds in southeastern Pennsylvania to examine the relations among chloride (Cl-) concentrations and ISC. Both flow-normalized Cl- concentrations and ISC increased over time in each of the six watersheds, consistent with changes in watershed management (e.g., ISC, road salt application, etc.). The watersheds that experienced the greatest changes in percent ISC (e.g., agriculture replaced by residential and commercial development) experienced the greatest changes in flow-normalized Cl- concentrations. We also utilized a comprehensive mass-balance model (2011-2018) that indicated Cl- inputs exceeded the outputs for the study watersheds. Road salt applied to state roads, non-state roads, and other impervious surfaces accounted for the majority of Cl- inputs to the six watersheds. Furthermore, increasing Cl- concentrations during baseflow conditions confirm impacts to shallow groundwater. Although flow-normalized Cl- concentrations are below the U.S. Environmental Protection Agency's chronic threshold value for impacts to aquatic organisms, year-round exceedances may result before the end of this century based on current trends. Though reduced Cl- loading to streams may be achieved by limiting the expansion of impervious surfaces in exurban and suburban watersheds, changes in baseflow concentrations are likely to be gradual because of the accumulated Cl- in groundwater.

Mobile monitoring of air and noise pollution in Philadelphia neighborhoods during 2017.

Mobile monitoring is a useful approach for measuring intra-urban variation of air pollution in urban environments. In this study, we used a mobile monitoring approach to study the spatial-temporal variability of air and noise pollution in urban neighborhoods of Philadelphia. During summer 2017, we used portable instruments to measure PM2.5, black carbon (BC), and noise levels along 5 km paths in four residential neighborhoods (Tioga, Mill Creek, Chestnut Hill, and Northern Liberties) and one commercial district (Center City) in Philadelphia, Pennsylvania, USA. A total of 62 sets of measurements were made at three different times of day (during morning rush hour, mid-afternoon, and during afternoon rush hour) from June 5 to July 7, 2017. Spatially, there was a significant difference in PM2.5 concentrations among the four residential neighborhoods. Overall, the Chestnut Hill neighborhood had the highest PM2.5 concentrations (13.25 ±â€¯6.89 µg/m3), followed by Tioga (9.58 ±â€¯4.83 µg/m3), Northern Liberties (7.02 ±â€¯4.17 µg/m3), and Mill Creek (3.9 ±â€¯4.5 µg/m3). There was temporal variability of pollutants depending on the neighborhood; Northern Liberties demonstrated the highest temporal variability in these data. The highest PM2.5 (18.86 ±â€¯3.17 mg/m3) was measured in the Chestnut Hill neighborhood during mid-afternoon. Mean PM2.5, BC, and noise levels based on mobile measurements at Philadelphia during summer 2017 were 8.41 ±â€¯4.31 µg/m3, 0.99 ±â€¯0.44 µg C/m3, and 62.01 ±â€¯3.20 dBA, respectively. Environmental noise showed the highest temporal variation of the monitored components for 3 time periods. In general, tree cover showed a weak and inconclusive association with particulate pollution levels.

A quantitative review of urban ecosystem service assessments: concepts, models, and implementation.

Although a number of comprehensive reviews have examined global ecosystem services (ES), few have focused on studies that assess urban ecosystem services (UES). Given that more than half of the world's population lives in cities, understanding the dualism of the provision of and need for UES is of critical importance. Which UES are the focus of research, and what types of urban land use are examined? Are models or decision support systems used to assess the provision of UES? Are trade-offs considered? Do studies of UES engage stakeholders? To address these questions, we analyzed 217 papers derived from an ISI Web of Knowledge search using a set of standardized criteria. The results indicate that most UES studies have been undertaken in Europe, North America, and China, at city scale. Assessment methods involve bio-physical models, Geographical Information Systems, and valuation, but few study findings have been implemented as land use policy.

Urban ecosystem services for resilience planning and management in New York City.

We review the current state of knowledge about urban ecosystem services in New York City (NYC) and how these services are regulated, planned for, and managed. Focusing on ecosystem services that have presented challenges in NYC-including stormwater quality enhancement and flood control, drinking water quality, food provisioning and recreation-we find that mismatches between the scale of production and scale of management occur where service provision is insufficient. Adequate production of locally produced services and services which are more accessible when produced locally is challenging in the context of dense urban development that is characteristic of NYC. Management approaches are needed to address scale mismatches in the production and consumption of ecosystem services. By coordinating along multiple scales of management and promoting best management practices, urban leaders have an opportunity to ensure that nature and ecosystem processes are protected in cities to support the delivery of fundamental urban ecosystem services.