A distinct urban biogeochemistry? Kaye, Jason P.; Groffman, Peter M.; Grimm, Nancy B. ...
Trends in ecology & evolution (Amsterdam),
04/2006, Letnik:
21, Številka:
4
Journal Article
Recenzirano
Most of the global human population lives in urban areas where biogeochemical cycles are controlled by complex interactions between society and the environment. Urban ecology is an emerging ...discipline that seeks to understand these interactions, and one of the grand challenges for urban ecologists is to develop models that encompass the myriad influences of people on biogeochemistry. We suggest here that existing models, developed primarily in unmanaged and agricultural ecosystems, work poorly in urban ecosystems because they do not include human biogeochemical controls such as impervious surface proliferation, engineered aqueous flow paths, landscaping choices, and human demographic trends. Incorporating these human controls into biogeochemical models will advance urban ecology and will require enhanced collaborations with engineers and social scientists.
We investigated the effects of land use and cover and surface geology on soil properties in Baltimore, MD, with the objectives to: (i) measure the physical and chemical properties of surface soils ...(0-10 cm) by land use and cover; and (ii) ascertain whether land use and cover explain differences in these properties relative to surface geology. Mean and median values of each variable measured across all plots showed that soil properties varied considerably. Chemical properties generally varied more than physical properties. A subset of the variables measured showed a pattern with land use and cover. Potassium, P, and bulk density were the most discerning variables differentiating forest cover from land uses dominated by turfgrass cover. Soil pH differentiated residential land use and cover from the other turfgrass types. This separation may reflect differences in management, e.g., additions of fertilizer, although additional research is needed to assess the importance of management on soil properties. Differences in surface soil properties among land use and cover types could be useful when conducting urban soil surveys, at least to spatially differentiate remnant soils from highly disturbed and managed soils. Other soil properties (Al, Mg, V, Ti, Mn, Fe, Ni, and soil texture) were related to surface geology and thus unique to the Baltimore region. The importance of surface geology was contrary to our expectation that urban factors would be more important in determining the distribution of surface soil characteristics. Heavy metal concentrations did not differentiate land use and cover, suggesting that these elements are more related to other factors.
We investigated the spatial distribution of heavy metal above-background (anthropic) contents of Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, Ti, V, and Zn in Baltimore City surface soils and related these levels ...to potential contaminating sources. Composite soil samples (0–10
cm depth) were digested using a nitric and hydrochloric extraction technique. Slightly more than 10% of plots exceeded United States Environmental Protection Agency screening guidelines for Pb. In a principal component analysis, the first component corresponded to Co, Cr, and Fe, which are constituents of local mafic rocks. The second component corresponded to Cu, Pb, and Zn which were significantly higher within than beyond a 100
m buffer of the major roads within the city; furthermore, Pb and Zn were higher in older residential lots.
Spatial distribution of metals in soils of an older US city (Baltimore) was affected by parent material, proximity to major roads, and housing age.
Urban green space is purported to offset greenhouse-gas (GHG) emissions, remove air and water pollutants, cool local climate, and improve public health. To use these services, municipalities have ...focused efforts on designing and implementing ecosystem-services-based "“green infrastructure"” in urban environments. In some cases the environmental benefits of this infrastructure have been well documented, but they are often unclear, unquantified, and/or outweighed by potential costs. Quantifying biogeochemical processes in urban green infrastructure can improve our understanding of urban ecosystem services and disservices (negative or unintended consequences) resulting from designed urban green spaces. Here we propose a framework to integrate biogeochemical processes into designing, implementing, and evaluating the net effectiveness of green infrastructure, and provide examples for GHG mitigation, stormwater runoff mitigation, and improvements in air quality and health.
Approximately 75-80% of the population of North America currently lives in urban areas as defined by national census bureaus, and urbanization is continuing to increase. Future trajectories of fossil ...fuel emissions are associated with a high degree of uncertainty; however, if the activities of urban residents and the rate of urban land conversion can be captured in urban systems models, plausible emissions scenarios from major cities may be generated. Integrated land use and transportation models that simulate energy use and traffic-related emissions are already in place in many North American cities. To these can be added a growing dataset of carbon gains and losses in vegetation and soils following urbanization, and a number of methods of validating urban carbon balance modeling, including top down atmospheric monitoring and urban 'metabolic' studies of whole ecosystem mass and energy flow. Here, we review the state of our understanding of urban areas as whole ecosystems with regard to carbon balance, including both drivers of fossil fuel emissions and carbon cycling in urban plants and soils. Interdisciplinary, whole-ecosystem studies of the socioeconomic and biophysical factors that influence urban carbon cycles in a range of cities may greatly contribute to improving scenarios of future carbon balance at both continental and global scales.
•Soil contamination of metals occurred in residences located in older, more urbanized areas.•Earthworm burdens correlated with soil Pb and isopod burdens correlated with As, Cr, Ni, Pb and Zn.•Bird ...blood Pb correlated with earthworm Pb burdens suggesting a high risk to wildlife.•The persistence of Pb contamination in urban soils after decades of reduced emissions is alarming.
This study examined the distribution of metals in residential soils from the scale of a residential yard to a metropolitan area by comparing residences along an urbanization gradient in the Baltimore–Washington area, USA. In addition, earthworms and terrestrial isopods were sampled from residential yards to measure body burdens of metals. Soil metal concentrations from lawns and planting bed (road, foundation, and yard) patches were compared (1) among land-use types (inner urban, outer urban, suburban, and rural); (2) between pre- and post-1940 built residential structures; and (3) among yard patch types. Lawn soil concentrations of As, Cd, and Pb varied statistically among the land-use types. Differences between inner urban and rural lawn soils varied almost eight-fold for Pb, three-fold for Cd, and more than two-fold for As. Bed patches exhibited a slightly stronger relationship than lawns across the urbanization gradient. A similar relationship was shown for pre- and post-1940 structures with older having higher concentrations than post-1940 structures. Earthworm body burdens were statistically correlated with soil Pb, while isopod burdens exhibited a significant relationship with soil As, Cr, Ni, Pb, and Zn. A post-hoc analysis with bird blood Pb data that was available for the residences, showed a significant relationship with earthworm Pb body burdens. This study suggests that despite policy efforts to reduce metal emissions, contamination of soil persists in urban residences at levels that have health implications for people and wildlife living in the Baltimore–Washington, DC area.
Soils constitute the largest sink of terrestrial carbon (C), and urban soils have the potential to provide significant soil C storage. Soils in urbanized landscapes experience a multitude of human ...alterations, such as compaction and management subsidies, that impact soil C dynamics. While field studies may provide data on urban soil C storage, modeling soil C dynamics under various human impact scenarios will provide a basis for identifying drivers of urban soil C dynamics and for predicting the potential for these highly altered soils to store C over time intervals not typically amenable to empirical validation. The goal of this study was to model soil C dynamics in residential lawns using CENTURY, a dynamic mechanistic model, to determine whether drivers of soil C dynamics in natural systems (e.g., soil texture) were equally useful for estimating soil C content of highly modified soils in urban residential areas. Without incorporating human impacts, we found no relationship between initial CENTURY model simulations and observed soil C (P > 0.05). Factors that best explained soil C accumulation for the observed soil C (bulk density, r2 = 0.30; home age, r2 = 0.37; P < 0.01) differed from those found important for the CENTURY model simulations (percent sand, r2 = 0.72, P < 0.001). Therefore, we conducted a modeling exercise to test whether simulating potential construction disturbance and lawn management practices would improve modeled soil and tree C. We found that incorporating these factors did improve CENTURY's ability to model soil and tree C (P < 0.001). The results from this analysis suggest that incorporating various human disturbances and management practices that occur in urban landscapes into CENTURY model runs will improve its ability to predict urban soil C dynamics, at least within a 100-yr time frame. Thus, enhancing our ability to provide recommendations for management and development practices that result in increasing urban soil C storage.
Riparian zones have been found to function as “sinks” for nitrate (NO3 -), the most common groundwater pollutant in the U. S., in many areas. The vast majority of riparian research, however, has ...focused on agricultural watersheds. There has been little analysis of riparian zones in urban watersheds, despite the fact that urban areas are important sources of NO3 - to nitrogen (N)-sensitive coastal waters in many locations. In this study, we measured stream incision, water table depths, and pools, production (mineralization, nitrification), and consumption (denitrification) of NO3 - in urban soils. Samples were taken from soil profiles (0−100 cm) of three forested urban and suburban zones and one forested reference riparian zone in the Baltimore, Maryland metropolitan area. Our objectives were to determine (1) if stream incision associated with urbanization results in lower riparian water tables, and (2) if pools, production, and consumption of NO3 - vary systematically with stream incision and riparian water table levels. Two of the three urban and suburban streams were more incised and all three had lower water tables in their riparian zones than the forested reference stream. Urban and suburban riparian zones had higher NO3 - pools and nitrification rates than the forested reference riparian zone, which was likely due to more aerobic soil profiles, lower levels of available soil carbon, and greater N enrichment in the urban and suburban sites. At all sites, denitrification potential decreased markedly with depth in the soil pro-file. Lower water tables in the urban and suburban riparian zones thus inhibit interaction of groundwater-borne NO3 - with near surface soils that have the highest denitrification potential. These results suggest that urban hydrologic factors can increase the production and reduce the consumption of NO3 - in riparian zones, reducing their ability to function as sinks for NO3 - in the landscape.
To determine the patterns of atmospheric deposition and throughfall in the vicinity of a large city, bulk deposition, oak forest throughfall, and particulate dust deposition were measured at sites ...along a transect within and to the north of New York City. Concentrations and fluxes of NO3 -, NH4 +, Ca2+, Mg2+, SO4 2-, and Cl- in throughfall all declined significantly with distance from the city, while hydrogen ion concentration and flux increased with distance from the city. Most of the change in concentrations and fluxes occurred within 45 km of the city. Throughfall deposition of inorganic N was twice as high in the urban sites as compared to the suburban and rural sites. Bulk deposition patterns were similar to those of throughfall, but changes along the transect were much less pronounced. The water-extractable component of dust deposition to Petri plates also was substantially higher in the urban sites for Ca2+, Mg2+, SO4 2-, NO3 -, and Cl-. The dust particles had little alkalinity, suggesting that alkaline aerosols were neutralized by acidic gases in the atmosphere. We propose that dust emissions from New York City act like an “urban scrubber”, removing acidic gases from the atmosphere and depositing them on the city as coarse particle dry deposition. Despite the urban scrubber effect, most of the dry deposition of nitrate was from gaseous nitrogen oxides, which were in much higher concentration in the city than in rural sites. Excess deposition of nutrients and pollutants could be important for the nutrient budgets of forests in and near urban areas.
Previous studies at the scale of a city have shown that surface soil nutrients, pH, and soil organic matter (SOM) can vary by land cover, land use, and management. This study was conducted in ...Baltimore County, Maryland, to quantify the differences in characteristics of soil in a residential neighborhood and adjacent forest patch sampling at a fine scale. The first objective was to compare soil characteristics in a residential neighborhood among ecotope types of forest, lawn, and planting beds that were underlain by the same parent material and thus only differed in plant cover. Another objective was to examine differences in soil properties of lawn soils that differed in age by 10 years. The final objective was to quantify the variation of these residential and forest soils. Composite soil samples from the surface to a depth of 5 cm were taken from planting beds and lawns from 50 residences and an adjacent forest patch. Results showed that the forest soil had 30 % more SOM and was more acidic than lawn soil. Conversely, Mg, P, K, and Ca were 47 to 67 % lower in forest compared to lawn soils even though both soils developed from similar parent materials. For the residential lawns, the older development had significantly higher concentration of soil P. There was also a difference between front and back lawns where front lawns had 26 and 10 % higher concentrations of Ca and Mg, respectively, and a higher pH than the back lawns. Finally, the variation of soil characteristics of all areas sampled, from lowest to highest was pH < SOM < K < Mg < Ca < P. Results of this study suggest that anthropogenic factors appear to overwhelm natural soil forming factors in suburban residential areas in the Baltimore metropolitan area and these differences appear to increase with time.
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