Harford County Department of Parks & Recreation Turf Management Program

The purpose of this document is to provide an agronomic plan for the Harford County Department of Parks & Recreation that establishes a minimum/recreational level turf grass standard for a variety of activities and that uses the most cost-effective treatment options available. The department maintains 91 multi-purpose fields and 58 baseball and softball diamonds. All of these sites consist of native soil and standard grass (mostly fescue and some bluegrass) playing surfaces. Fields are generally used from 5pm to dark on weekdays and games are played on weekends typically from sun-up to sun-down. Prior data collection indicates fields are used approximately 20-30 hours a week. There are instances where fields are used up to 35 hours a week. The current mowing schedule is a seven-day mowing cycle. Current mowing heights are between 2.5” - 3” (which can be adjusted) with a rotating cross-cut direction each week. Mowing occurs from early April until early November. Based on the current budget, we recommend maintaining the mowing schedule at once per week and rotating the direction of cut. Currently, the recreation councils are treating their fields with fertilizer treatment, weed inhibitor, seeding and sodding when needed. The goal is to determine the most cost-effective treatment option for these playing surfaces. Equally important is to create a uniform maintenance regime among all fields.Harford Count

Stratospheric carbon isotope fractionation and tropospheric histories of CFC-11, CFC-12, and CFC-113 isotopologues

We present novel measurements of the carbon isotope composition of CFC-11 (CCl3F), CFC-12 (CCl2F2), and CFC-113 (CF2ClCFCl2), three atmospheric trace gases that are important for both stratospheric ozone depletion and global warming. These measurements were carried out on air samples collected in the stratosphere the main sink region for these gases and on air extracted from deep polar firn snow. We quantify, for the first time, the apparent isotopic fractionation, ?app(13C), for these gases as they are destroyed in the high- and mid-latitude stratosphere: ?app(CFC-12, high-latitude)?=(-20.2 4.4)? , and ?app(CFC-113, high-latitude)?=(-9.4 4.4)? , ?app(CFC-12, mid-latitude)?=(-30.3 10.7)? , and ?app(CFC-113, mid-latitude)?=(-34.4 9.8)? . Our CFC-11 measurements were not sufficient to calculate ?app(CFC-11), so we instead used previously reported photolytic fractionation for CFC-11 and CFC-12 to scale our ?app(CFC-12), resulting in ?app(CFC-11, high-latitude)?=(-7.8 1.7)? and ?app(CFC-11, mid-latitude)?=(-11.7 4.2)? . Measurements of firn air were used to construct histories of the tropospheric isotopic composition, dT(13C), for CFC-11 (1950s to 2009), CFC-12 (1950s to 2009), and CFC-113 (1970s to 2009), with dT(13C) increasing for each gas. We used ?app(high-latitude), which was derived from more data, and a constant isotopic composition of emissions, dE(13C), to model dT(13C, CFC-11), dT(13C, CFC-12), and dT(13C, CFC-113). For CFC-11 and CFC-12, modelled dT(13C) was consistent with measured dT(13C) for the entire period covered by the measurements, suggesting that no dramatic change in dE(13C, CFC-11) or dE(13C, CFC-12) has occurred since the 1950s. For CFC-113, our modelled dT(13C, CFC-113) did not agree with our measurements earlier than 1980. This discrepancy may be indicative of a change in dE(13C, CFC-113). However, this conclusion is based largely on a single sample and only just significant outside the 95?% confidence interval. Therefore more work is needed to independently verify this temporal trend in the global tropospheric 13C isotopic composition of CFC-113. Our modelling predicts increasing dT(13C, CFC-11), dT(13C, CFC-12), and dT(13C, CFC-113) into the future. We investigated the effect of recently reported new CFC-11 emissions on background dT(13C, CFC-11) by fixing model emissions after 2012 and comparing dT(13C, CFC-11) in this scenario to the model base case. The difference in dT(13C, CFC-11) between these scenarios was 1.4? in 2050. This difference is smaller than our model uncertainty envelope and would therefore require improved modelling and measurement precision as well as better quantified isotopic source compositions to detect

Investigating stratospheric changes between 2009 and 2018 with halogenated trace gas data from aircraft, AirCores, and a global model focusing on CFC-11

We present new observations of trace gases in the stratosphere based on a cost-effective sampling technique that can access much higher altitudes than aircraft. The further development of this method now provides detection of species with abundances in the parts per trillion (ppt) range and below. We obtain mixing ratios for six gases (CFC-11, CFC-12, HCFC-22, H-1211, H-1301, and SF6), all of which are important for understanding stratospheric ozone depletion and circulation. After demonstrating the quality of the data through comparisons with ground-based records and aircraft-based observations, we combine them with the latter to demonstrate its potential. We first compare the data with results from a global model driven by three widely used meteorological reanalyses. Secondly, we focus on CFC-11 as recent evidence has indicated renewed atmospheric emissions of that species relevant on a global scale. Because the stratosphere represents the main sink region for CFC-11, potential changes in stratospheric circulation and troposphere–stratosphere exchange fluxes have been identified as the largest source of uncertainty for the accurate quantification of such emissions. Our observations span over a decade (up until 2018) and therefore cover the period of the slowdown of CFC-11 global mixing ratio decreases measured at the Earth's surface. The spatial and temporal coverage of the observations is insufficient for a global quantitative analysis, but we do find some trends that are in contrast with expectations, indicating that the stratosphere may have contributed to the slower concentration decline in recent years. Further investigating the reanalysis-driven model data, we find that the dynamical changes in the stratosphere required to explain the apparent change in tropospheric CFC-11 emissions after 2013 are possible but with a very high uncertainty range. This is partly caused by the high variability of mass flux from the stratosphere to the troposphere, especially at timescales of a few years, and partly by large differences between runs driven by different reanalysis products, none of which agree with our observations well enough for such a quantitative analysis

Stratospheric carbon isotope fractionation and tropospheric histories of CFC-11, CFC-12, and CFC-113 isotopologues

We present novel measurements of the carbon isotope composition of CFC-11 (CCl3F), CFC-12 (CCl2F2), and CFC-113 (CF2ClCFCl2), three atmospheric trace gases that are important for both stratospheric ozone depletion and global warming. These measurements were carried out on air samples collected in the stratosphere the main sink region for these gases and on air extracted from deep polar firn snow. We quantify, for the first time, the apparent isotopic fractionation, ?app(13C), for these gases as they are destroyed in the high- and mid-latitude stratosphere: ?app(CFC-12, high-latitude)?=(-20.2 4.4)? , and ?app(CFC-113, high-latitude)?=(-9.4 4.4)? , ?app(CFC-12, mid-latitude)?=(-30.3 10.7)? , and ?app(CFC-113, mid-latitude)?=(-34.4 9.8)? . Our CFC-11 measurements were not sufficient to calculate ?app(CFC-11), so we instead used previously reported photolytic fractionation for CFC-11 and CFC-12 to scale our ?app(CFC-12), resulting in ?app(CFC-11, high-latitude)?=(-7.8 1.7)? and ?app(CFC-11, mid-latitude)?=(-11.7 4.2)? . Measurements of firn air were used to construct histories of the tropospheric isotopic composition, dT(13C), for CFC-11 (1950s to 2009), CFC-12 (1950s to 2009), and CFC-113 (1970s to 2009), with dT(13C) increasing for each gas. We used ?app(high-latitude), which was derived from more data, and a constant isotopic composition of emissions, dE(13C), to model dT(13C, CFC-11), dT(13C, CFC-12), and dT(13C, CFC-113). For CFC-11 and CFC-12, modelled dT(13C) was consistent with measured dT(13C) for the entire period covered by the measurements, suggesting that no dramatic change in dE(13C, CFC-11) or dE(13C, CFC-12) has occurred since the 1950s. For CFC-113, our modelled dT(13C, CFC-113) did not agree with our measurements earlier than 1980. This discrepancy may be indicative of a change in dE(13C, CFC-113). However, this conclusion is based largely on a single sample and only just significant outside the 95?% confidence interval. Therefore more work is needed to independently verify this temporal trend in the global tropospheric 13C isotopic composition of CFC-113. Our modelling predicts increasing dT(13C, CFC-11), dT(13C, CFC-12), and dT(13C, CFC-113) into the future. We investigated the effect of recently reported new CFC-11 emissions on background dT(13C, CFC-11) by fixing model emissions after 2012 and comparing dT(13C, CFC-11) in this scenario to the model base case. The difference in dT(13C, CFC-11) between these scenarios was 1.4? in 2050. This difference is smaller than our model uncertainty envelope and would therefore require improved modelling and measurement precision as well as better quantified isotopic source compositions to detect

Investigating stratospheric circulation and chemistry changes over three decades with trace gas data from aircraft, large balloons, and AirCores

Laube et al. (2020) investigated stratospheric changes between 2009 and 2018 with halogenated trace gas data (CFC-11, CFC-12, H-1211, H-1301, HCFC-22, and SF6) from air samples collected via aircraft and AirCores, and compared the mixing ratios and average stratospheric transit times derived from these observations with those from a global model. We here expand this analysis in three ways: firstly, by adding data from further traces gases such as CFC-115, C2F6, and HCFC-142b to broaden the range of tropospheric trends and stratospheric lifetimes, both of which help to assess the robustness of inferred long-term trends in the stratosphere; secondly, by increasing the temporal span of the observations to nearly three decades using new AirCore observations as well as reanalysed archived air samples collected on board high altitude aircraft and large balloons in the 1990s and 2000s; and thirdly, by investigating the fractional release factors and mean ages of air derived from the aforementioned species as measures of their stratospheric chemistry and the strength of the Brewer-Dobson circulation. In combination with model data from the Chemical Langrangian Model of the Stratosphere (CLaMS) this unique data set allows for an unprecedented evaluation of stratospheric chemistry and dynamics in the mid-latitudes of the Northern Hemisphere

Investigating stratospheric circulation and chemistry changes over three decades with trace gas data from aircraft, large balloons, and AirCores

Laube et al. (2020) investigated stratospheric changes between 2009 and 2018 with halogenated trace gas data (CFC-11, CFC-12, H-1211, H-1301, HCFC-22, and SF6) from air samples collected via aircraft and AirCores, and compared the mixing ratios and average stratospheric transit times derived from these observations with those from a global model. We here expand this analysis in three ways: firstly, by adding data from further traces gases such as CFC-115, C2F6, and HCFC-142b to broaden the range of tropospheric trends and stratospheric lifetimes, both of which help to assess the robustness of inferred long-term trends in the stratosphere; secondly, by increasing the temporal span of the observations to nearly three decades using new AirCore observations as well as reanalysed archived air samples collected on board high altitude aircraft and large balloons in the 1990s and 2000s; and thirdly, by investigating the fractional release factors and mean ages of air derived from the aforementioned species as measures of their stratospheric chemistry and the strength of the Brewer-Dobson circulation. In combination with model data from the Chemical Langrangian Model of the Stratosphere (CLaMS) this unique data set allows for an unprecedented evaluation of stratospheric chemistry and dynamics in the mid-latitudes of the Northern Hemisphere

Investigating stratospheric circulation and chemistry changes over three decades with trace gas data from aircraft, large balloons, and AirCores

Laube et al. (2020) investigated stratospheric changes between 2009 and 2018 with halogenated trace gas data (CFC-11, CFC-12, H-1211, H-1301, HCFC-22, and SF6) from air samples collected via aircraft and AirCores, and compared the mixing ratios and average stratospheric transit times derived from these observations with those from a global model. We here expand this analysis in three ways: firstly, by adding data from further traces gases such as CFC-115, C2F6, and HCFC-142b to broaden the range of tropospheric trends and stratospheric lifetimes, both of which help to assess the robustness of inferred long-term trends in the stratosphere; secondly, by increasing the temporal span of the observations to nearly three decades using new AirCore observations as well as reanalysed archived air samples collected on board high altitude aircraft and large balloons in the 1990s and 2000s; and thirdly, by investigating the fractional release factors and mean ages of air derived from the aforementioned species as measures of their stratospheric chemistry and the strength of the Brewer-Dobson circulation. In combination with model data from the Chemical Langrangian Model of the Stratosphere (CLaMS) this unique data set allows for an unprecedented evaluation of stratospheric chemistry and dynamics in the mid-latitudes of the Northern Hemisphere.&#160;ReferencesLaube, et al., Atmos. Chem. Phys., 20, 9771&#8211;9782, 2020, https://doi.org/10.5194/acp-20-9771-2020</p

Investigating stratospheric circulation and chemistry changes over three decades with trace gas data from aircraft, large balloons, and AirCores

Laube et al. (2020) investigated stratospheric changes between 2009 and 2018 with halogenated trace gas data (CFC-11, CFC-12, H-1211, H-1301, HCFC-22, and SF6) from air samples collected via aircraft and AirCores, and compared the mixing ratios and average stratospheric transit times derived from these observations with those from a global model. We here expand this analysis in three ways: firstly, by adding data from further traces gases such as CFC-115, C2F6, and HCFC-142b to broaden the range of tropospheric trends and stratospheric lifetimes, both of which help to assess the robustness of inferred long-term trends in the stratosphere; secondly, by increasing the temporal span of the observations to nearly three decades using new AirCore observations as well as reanalysed archived air samples collected on board high altitude aircraft and large balloons in the 1990s and 2000s; and thirdly, by investigating the fractional release factors and mean ages of air derived from the aforementioned species as measures of their stratospheric chemistry and the strength of the Brewer-Dobson circulation. In combination with model data from the Chemical Langrangian Model of the Stratosphere (CLaMS) this unique data set allows for an unprecedented evaluation of stratospheric chemistry and dynamics in the mid-latitudes of the Northern Hemisphere.&#160;ReferencesLaube, et al., Atmos. Chem. Phys., 20, 9771&#8211;9782, 2020, https://doi.org/10.5194/acp-20-9771-2020</p

Development of the Navigation Guide Evidence-to-Decision Framework for Environmental Health

This framework provides a transparent and consistent approach for developing recommendations to protect human health from environmental exposures, particularly historically marginalized communities

Investigating stratospheric changes between 2009 and 2018 with halogenated trace gas data from aircraft, AirCores, and a global model focusing on CFC-11

We present new observations of trace gases in the stratosphere based on a cost-effective sampling technique that can access much higher altitudes than aircraft. The further development of this method now provides detection of species with abundances in the parts per trillion (ppt) range and below. We obtain mixing ratios for six gases (CFC-11, CFC-12, HCFC-22, H-1211, H-1301, and SF6), all of which are important for understanding stratospheric ozone depletion and circulation. After demonstrating the quality of the data through comparisons with ground-based records and aircraft-based observations, we combine them with the latter to demonstrate its potential. We first compare the data with results from a global model driven by three widely used meteorological reanalyses. Secondly, we focus on CFC-11 as recent evidence has indicated renewed atmospheric emissions of that species relevant on a global scale. Because the stratosphere represents the main sink region for CFC-11, potential changes in stratospheric circulation and troposphere-stratosphere exchange fluxes have been identified as the largest source of uncertainty for the accurate quantification of such emissions. Our observations span over a decade (up until 2018) and therefore cover the period of the slowdown of CFC-11 global mixing ratio decreases measured at the Earth's surface. The spatial and temporal coverage of the observations is insufficient for a global quantitative analysis, but we do find some trends that are in contrast with expectations, indicating that the stratosphere may have contributed to the slower concentration decline in recent years. Further investigating the reanalysis-driven model data, we find that the dynamical changes in the stratosphere required to explain the apparent change in tropospheric CFC-11 emissions after 2013 are possible but with a very high uncertainty range. This is partly caused by the high variability of mass flux from the stratosphere to the troposphere, especially at timescales of a few years, and partly by large differences between runs driven by different reanalysis products, none of which agree with our observations well enough for such a quantitative analysis