Historical changes in tree and impervious surface cover following urban renewal in a small postindustrial city.

Changes in tree cover and impervious surfaces have been observed across many cities in the United States over the past 70 years. Many municipalities are implementing tree planting programs in efforts to increase tree cover. A detailed understanding of historical changes in land cover can inform urban forest management. I applied a convolutional neural network image segmentation approach to historical aerial imagery to delineate changes in land cover in 1957, 1974, and 2017 in Utica, New York, a small, postindustrial city. The model predicted tree, pavement, and building land cover in each year with overall accuracies ranging from 82-87%. From 1957 to 2017, tree cover declined in many areas and impervious surface cover (buildings and pavement) increased. Tree cover gains largely occurred in uninhabited, natural areas; whereas, the greatest declines in tree coverage occurred in many residential areas following the start of the urban renewal efforts in 1957. Current tree planting efforts targeted at homeowners could drive disparities in future tree cover since several areas of Utica with low tree have a high proportion of renter occupied homes and a low median household income. Convolutional Neural Network approaches for image segmentation of aerial imagery are a helpful tool in understanding patterns in changes in tree and impervious surfaces. A better understanding of the legacies of historical policies and neighborhood-scale changes in land cover can assist in highlighting priorities for urban forest management and justice-oriented urban forestry approaches to urban tree planting.

Anaerobic pyrite oxidation in a naturally occurring pyrite-rich sediment under preload surcharge.

Pyrite undergoes oxidation when exposed to aqueous oxygen to produce acidic leachate with high concentrations of H+, SO42-, and Fe3+. The oxidation mechanism is currently ascribed to contact between the mineral and aqueous oxygen. Consequently, management of acidic leachate from acid sulfate soils and acid mine drainage is focused on the prevention of contact between the sediment and aqueous oxygen through the surface. Intriguing though is the fact that in aquatic sediments, redox processes occur in sequence with the oxidizing agents. Among the common oxidants in aquatic sediments are O2, [Formula: see text], Mn, and Fe, in the order of efficiency. Consequently, following the depletion of oxygen in pyrite-rich sediment, it would be expected that [Formula: see text], followed by Mn and then Fe, would continue the oxidation process. However, evidence of anaerobic pyrite oxidation in a naturally occurring pyrite-rich sediment is limited. Few studies have investigated the process in aquatic systems but mostly in laboratory experimental set ups. In this study, pyrite oxidation in a naturally occurring pyrite-rich sediment was investigated. A section of the sediment was covered with surface surcharge, in the form of compacted fill. The section of the sediment outside the surcharged area was preserved and used as control experiment. Solid phase soil and porewater samples were subjected to elemental, mineralogical, and microbial analyses. The results show excess accumulation of sulfate and sulfide in the anoxic zones of the original sediment and beneath the surcharge, accompanied by the disappearance of [Formula: see text], Mn, and Fe in the anoxic zones, indicating electron transfers between donors and acceptors, with pyrite as the most likely electron donor. The study outcome poses a significant challenge to the use of surface cover for the management of acidic leachate from pyrite oxidation, particularly, in areas rich in [Formula: see text], MnO-2, or Fe.

Design and performance evaluation of a 1000-year evapotranspiration-capillary surface barrier.

Surface barrier technology is used to isolate radioactive waste and to reduce or eliminate recharge water to the waste zone for 1000 years or longer. However, the design and evaluation of such a barrier is challenging because of the extremely long design life. After establishing a set of design and performance objectives, a package of design solutions was developed for 1000-year surface barriers over nuclear waste sites. The Prototype Hanford Barrier (PHB) was then constructed in 1994 in the field over an existing waste site as a demonstration. The barrier was tested to evaluate surface-barrier design and performance at the field scale under conditions of enhanced and natural precipitation and of no vegetation. The monitoring data demonstrate that the barrier satisfied nearly all objectives in the past two decades. The PHB far exceeded the Resource Conservation and Recovery Act criteria, functioned in Hanford's semiarid climate, limited drainage to well below the 0.5 mm yr-1 performance criterion, limited runoff, and minimized erosion and bio-intrusion. Given the two-decade record of successful performance and consideration of the processes and mechanisms that could affect barrier stability and hydrology in the future, the results suggest the PHB is very likely to perform for its 1000-year design life. This conclusion is based on two assumptions: (1) the exposed subgrade receives protection against erosion and (2) institutional controls prevent inadvertent human activity at the barrier. The PHB design can serve as the basis for site-specific barriers over waste sites containing underground nuclear waste, uranium mine tailings, and hazardous mine waste.

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.

Rice straw cover decreases soil erosion and sediment-bound C, N, and P losses but increases dissolved organic C export from upland maize fields as evidenced by δ13C.

Soil surface with crop residue is effective in reducing soil erosion and carbon (C), nitrogen (N), and phosphorus (P) losses from sloping fields. However, there is a high possibility that surface cover increases export of dissolved organic C (DOC) though relevant field studies under natural rainfall are lacking. In this study, the effects of surface cover with rice (Oryza sativa L.) straw on soil and CNP losses in both dissolved and sediment-bound forms from maize (Zea mays L.) fields were investigated under two fertilization levels (standard and double) × two types of runoff experiments (natural rainfall and artificial irrigation). Changes in soil properties including moisture, temperature, nutrients, and C concentration as well as maize yield were also examined. Surface cover decreased soil and total CNP losses by up to 82% across the experimental plots with some exceptions. However, surface cover increased DOC export in both natural (by 68-82% in total across all events) and artificial (by 3-4 fold) runoff, suggesting that crop residue cover may act as a DOC pollution source of water bodies. The contribution of rice straw to DOC, which was calculated using the δ13C of DOC from covered plots (-24.1 to -28.0‰) and control plots (-19.6 to -25.1‰), was 52.5-95.8%. The concentrations of K2SO4-extractable and microbial biomass C of the soils did not differ between covered and control plots, suggesting that DOC produced from rice straw was not incorporated into the soils, but rather, was washed out with surface runoff in this study. Surface cover increased maize growth and yield, particularly in double fertilization plots, through improved soil moisture, temperature, and nutrient conditions. To take full advantage of surface cover with crop residue, a further study on reducing DOC loss from crop residue needs to be conducted.

Density Dependence Influences the Efficacy of Wastewater Remediation by Lemna minor.

As part of a circular economy (CE) approach to food production systems, Lemnaceae, i.e., duckweed species, can be used to remediate wastewater due to rapid nutrient assimilation and tolerance of non-optimal growing conditions. Further, given rapid growth rates and high protein content, duckweed species are a valuable biomass. An important consideration for duckweed-mediated remediation is the density at which the plants grow on the surface of the wastewater, i.e., how much of the surface of the medium they cover. Higher duckweed density is known to have a negative effect on duckweed growth, which has implications for the development of duckweed-based remediation systems. In the present study, the effects of density (10-80% plant surface coverage) on Lemna minor growth, chlorophyll fluorescence and nutrient remediation of synthetic dairy processing wastewater were assessed in stationary (100 mL) and re-circulating non-axenic (11.7 L) remediation systems. Overall, L. minor growth, and TN and TP removal rates decreased as density increased. However, in the stationary system, absolute TN and TP removal were greater at higher densities (50-80% coverage). The exact cause of density related growth reduction in duckweed is unclear, especially at densities well below 100% surface coverage. A further experiment comparing duckweed grown at 'low' and 'high' density conditions with the same biomass and media volume conditions, showed that photosynthetic yield, Y(II), is reduced at high density despite the same nutrient availability at both densities, and arguably similar shading. The results demonstrate a negative effect of high density on duckweed growth and nutrient uptake, and point towards signals from neighbouring duckweed colonies as the possible cause.

Increased association between climate change and vegetation index variation promotes the coupling of dominant factors and vegetation growth.

Vegetation productivity dynamics are closely related to climate change, and water availability determines vegetation growth in water-limited ecosystems. Nevertheless, how changes in the interactions between climatic factors and vegetation activity variation regulate the relationship between their trends remains unclear. The Normalized Difference Vegetation Index (NDVI) is an effective proxy of vegetation growth. First, we investigated the NDVI trends, and the results revealed a vegetation activity with weaker greening and greater spatial heterogeneity after an obvious land-cover breakpoint in 1999 compared with that before 1999 in northwest China. Notably, the Loess Plateau greatly led the greenness trends, but the Tibet Plateau showed mean browning after 1999, which implied that the coupling of climate change and vegetation trends varied with spatio-temporal changes. Subsequently, using the Geographical Detector Method (GDM), we quantified and compared the association between climate change and the interannual variability of NDVI in the two stages. Vegetation productivity variation is more closely related to changes in climatic factors after 1999 compared with that before 1999. Precipitation (PPT) and vapor pressure deficit (VPD) are the primary constraints to vegetation growth in both stages. Patterns in NDVI trend increases are consistent with those of increased PPT and decreased VPD and vice versa after 1999. However, the same patterns were not observed before 1999 because of the weak association between climate change and NDVI variation. This implicated a great significance of the association between climate change and changes in vegetation activity for the prediction of potential carbon sequestration due to the shift of dominant factors and their trends under future climate change.

Evaluation of site-specific lateral inclusion zone for vapor intrusion based on an analytical approach.

In 2002, U.S. EPA proposed a general buffer zone of approximately 100 feet (30 m) laterally to determine which buildings to include in vapor intrusion (VI) investigations. However, this screening distance can be threatened by factors such as extensive surface pavements. Under such circumstances, EPA recommended investigating soil vapor migration distance on a site-specific basis. To serve this purpose, we present an analytical model (AAMLPH) as an alternative to estimate lateral VI screening distances at chlorinated compound-contaminated sites. Based on a previously introduced model (AAML), AAMLPH is developed by considering the effects of impervious surface cover and soil geology heterogeneities, providing predictions consistent with the three-dimensional (3-D) numerical simulated results. By employing risk-based and contribution-based screening levels of subslab concentrations (50 and 500 µg/m(3), respectively) and source-to-subslab attenuation factor (0.001 and 0.01, respectively), AAMLPH suggests that buildings greater than 30 m from a plume boundary can still be affected by VI in the presence of any two of the three factors, which are high source vapor concentration, shallow source and significant surface cover. This finding justifies the concern that EPA has expressed about the application of the 30 m lateral separation distance in the presence of physical barriers (e.g., asphalt covers or ice) at the ground surface.

Variation of Spirulina maxima biomass production in different depths of urea-used culture medium

Fewer studies have assessed the outdoor cultivation of Spirulina maxima compared with S. platensis, although the protein content of S. maxima is higher than S. platensis. Spirulina growth medium requires an increased amount of NaHCO3, Na2CO3, and NaNO3, which increases the production cost. Therefore, the current study used a low-cost but high-efficiency biomass production medium (Medium M-19) after testing 33 different media. The medium depth of 25 cm (group A) was sub-divided into A1 (50% cover with a black curtain (PolyMax, 12 oz ultra-blackout), A2 (25% cover), and A3 (no cover). Similarly the medium depths of 30 and 35 cm were categorized as groups B (B1, B2, and B3) and C (C1, C2, and C3), respectively, and the effects of depth and surface light availability on growth and biomass production were assessed. The highest biomass production was 2.05 g L-1 in group A2, which was significantly higher (p < 0.05) than that in all other groups and sub-groups. Spirulina maxima died in B1 and C1 on the fifth day of culture. The biochemical composition of the biomass obtained from A2 cultures, including protein, carbohydrate, lipid, moisture, and ash, was 56.59%, 14.42%, 0.94%, 5.03%, and 23.02%, respectively. Therefore, S. maxima could be grown outdoors with the highest efficiency in urea-enriched medium at a 25-cm medium depth with 25% surface cover or uncovered.