Biogeochemical cycling was studied in Sitka spruce [Picea sitchensis (Bong.) Carr.] and western hemlock‐Douglas‐fir [Tsuga heterophylla (Raf.) Sarg.‐Pseudotsuga menziesii (Mirbel) Franco] ecosystems on chronosequence of five uplifted marine terraces in coastal Oregon. The terraces occur 0.25 to 8.6 km from the Pacific Ocean and range from 80 to ∼500 kyr in age. The soils are highly weathered and include Inceptisols on the youngest terrace and Spodosols with clay‐enriched horizons and Ultisols on the older terraces. Bulk precipitation, throughfall, and soil solutions (four depths) were collected monthly from November 1992 through April 1993. The solutions were analyzed for pH, dissolved cations (Na, Mg, Ca, K, Fe, Al, and Si), anions (Cl, SO4, HCO3, NO3, and PO4), and organic C. Cations (µmolc L−1) in all solutions were ranked: Na > Mg > Ca ≥ K > H; anions were ranked: Cl > SO4 > NO3 >> HCO3. The Na/Cl ratio in all solutions was comparable to that of seawater. The mean sums of cations and anions in all solutions declined sharply with distance from the coast. Throughfall enrichment of all ions suggests that aerosol impaction of sea salts is a dominant process within the coastal fogbelt of Oregon. In that the soils have low inherent fertility, the trees appear to obtain Ca, Mg, K, and S primarily from atmospheric sources. These nutrients are utilized by abundant fine roots in the forest floor and upper 5 to 20 cm of mineral soil. Net cation loss is less than in other areas of the Pacific Northwest and is controlled by organic anions rather than the bicarbonate anion.
Growth in urban populations has lead to increased pressure to use urban soils for green space, play areas, and urban and community gardens, but existing soil interpretations do not address the issues faced in urban settings. Therefore, the goals of this research were (i) to develop a method for characterizing urban soils in Maine, (ii) to characterize the physical and chemical properties of select urban soils, (iii) to evaluate the relationship between trace elements and other soil factors, and (iv) to use this information to develop interpretations to assist urban residents. We examined seven pedons from a low‐income urban neighborhood in Portland, ME that was heavily industrialized in the late 1800s. The pedons were described in detail, and mineral horizons were analyzed for particle size, cation exchange capacity (CEC), base saturation, exchangeable bases, pH, and trace elements (Pb, Cr, Cu, Co, Cd, Ni, Zn, Hg, Ti, Zr). The soils contained many artifacts, and all soil properties exhibited a high degree of horizontal and vertical spatial variability. Several trace elements were present at elevated levels, but Pb was the dominant metal in surface horizons (600 mg/kg). Many metals were correlated with each other, and also with Fe and Al. Several metals were also correlated with clay content and pH. Mapping soil units with specific ranges of trace element levels would be very difficult because of the extreme variability, although correlations between heavy metals and easily measurable soil properties may prove useful in future urban soil explorations in Portland.
Many soils in the greater Portland, ME area are contaminated with high concentrations of lead, largely because of the prevalence of lead in pre‐1978 residential paint and past industrial activities. Lead is highly toxic, especially to children, and negatively impacts children's health by disrupting the development of the nervous system, causing delays in growth and learning disabilities. This study was conducted to determine the soil lead distribution throughout the Bayside, Parkside, and West End neighborhoods of the Portland peninsula. The peninsula is the oldest part of the city, the heart of the business district, and the location of three very ethnically diverse urban neighborhoods. Bayside is a low‐income, racially and ethnically diverse neighborhood and is home to the largest number of refugees and immigrants of any other neighborhood in Portland. Parkside is the most densely populated and ethnically diverse square mile of Maine, and 25% of the population live below the poverty level. The West End neighborhood was developed after Portland's “great fire” in 1866, and approximately 84% of the housing was built before 1950. All of the neighborhoods have a history of heavy industry and manufacturing; including stove foundries, tanneries, boat building, and scrap metal recycling. Thus, lead poisoning is a great concern in Portland, and cases of severely poisoned children have been identified. We sampled 104 residential properties and collected 1087 surface soil samples according to EPA's Lead Safe Yard Protocols. Soils were extracted using USEPA Method 3050b and analyzed on an ICP for Pb, Cd, Ni, Zn, Cr, Co, Cu, As, Mn, and Hg. Concentrations for most metals were below EPA critical limits, but lead concentrations varied from 10 mg/kg to 25,100 mg/kg. Lead concentrations were then mapped using GIS. The spatial distribution maps show lead distribution patterns that are likely generated by a nonrandom process, such as historical point sources.
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