Nitrate Concentrations in Springs Flowing into the Lower Flint River Basin,Georgia U.S.A.1

Allums, Stephanie E., Stephen P. Opsahl, Stephen W. Golladay, David W. Hicks, and L. Mike Conner, 2012. Nitrate Concentrations in Springs Flowing Into the Lower Flint River Basin, Georgia U.S.A. Journal of the American Water Resources Association (JAWRA) 48(3): 423-438. DOI: 10.1111/j.1752-1688.2011.00624.x Abstract: Analysis of long-term data from (2001-2009) in four springs that discharge from the Upper Floridan aquifer into the Flint River (southwestern Georgia, United States) indicate aquifer and surface-water susceptibility to nutrient loading. Nitrate-N concentrations ranged from 1.74 to 3.30 mg/l, and exceeded historical levels reported for the Upper Floridan aquifer (0.26-1.52 mg/l). Statistical analyses suggest increasing nitrate-N concentration in groundwater discharging at the springs (n = 146 over eight years) and that nitrate-N concentration is influenced by a dynamic interaction between depth to groundwater (an indicator of regional hydrologic conditions) and land use. A one-time synoptic survey of 10 springs (6 springs in addition to the 4 previously mentioned) using stable isotopes generated δ¹⁵N-NO₃⁻ values (4.8-8.4‰ for rural springs and 7.7-13.4‰ for developed/urban springs) suggesting mixed sources (i.e., fertilizer, animal waste, and soil organic nitrogen) of nitrate-N to rural springs and predominantly animal/human waste to urban springs. These analyses indicate a direct relation between nitrate-N loading since the 1940s and intensification of agricultural and urban land use. This study demonstrates the importance of evaluating long-term impacts of land use on water quality in groundwater springs and in determining how rapidly these changes occur.     

The availability of copper in soils historically amended with sewage sludge, manure, and compost

Metals in soils amended with sewage sludge are typically less available compared with those in soils spiked with soluble metal salts. However, it is unclear if this difference remains in the long term. A survey of copper (Cu) availability was made in soils amended with sewage sludge, manure, and compost, collectively named organic amendments. Paired sets of amended and control soils were collected from 22 field trials where the organic amendments had aged up to 112 yr. Amended soils had higher total Cu concentrations (range, 2-220 mg Cu kg; median, 15 mg Cu kg) and organic C (range, 1-16 g kg; median, 4 g kg) than control soils. All samples were freshly spiked with CuCl, and the toxicity of added Cu to barley was compared between amended and control soils. The toxicity of added Cu was significantly lower in amended soils than in control soil in 15 sets by, on average, a factor of 1.4, suggesting that aged amendments do not largely increase Cu binding sites. The fraction of added Cu that is isotopic exchangeable Cu (labile Cu) was compared between control soils freshly spiked with CuCl and amended soils with both soils at identical total Cu concentrations. Copper derived from amendments was significantly less labile (on average 5.9-fold) than freshly added Cu in 18 sets of soils. This study shows that Cu availability after long-term applications of organic amendments is lower than that of freshly added Cu salts, mainly because of its lower availability in the original matrix and ageing reactions than because of increased metal binding sites in soil.     

“One thing leads to another”—Commodities,linkages and industrial development

With a particular focus on low income economies in SSA, this paper addresses the nature and determinants of linkages from the commodities sectors and challenges the received view that enclave development is an inherent characteristic of resource extraction, particularly in the hard and energy commodities sectors. It argues that there has been a steady increase in linkage development and that there are significant opportunities for deepening this process. The opportunities may be greater for backward than for forward linkages, particularly in the minerals and energy sectors. In making this case, this Discussion Paper draws on the experience of high income countries which have resource intensive economic structures, the geographical specificity of many resources and the growing interest of large resource extracting firms in outsourcing the production of inputs which are outside of their core competences and in supporting local production of some inputs, it sets out a general model of linkage development which distinguishes between win–win and win–lose outcomes.     

Evidence for short-range transport of atmospheric mercury to a rural,inland site

Atmospheric mercury (Hg) species, including gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate-bound mercury (Hg_p), were monitored near three sites, including a cement plant (monitored in 2007 and 2008), an urban site and a rural site (both monitored in 2005 and 2008). Although the cement plant was a significant source of Hg emissions (for 2008, GEM: 2.20 ± 1.39 ng m^?3, RGM: 25.2 ± 52.8 pg m^?3, Hg_p 80.8 ± 283 pg m^?3), average GEM levels and daytime average dry depositional RGM flux were highest at the rural site, when all three sites were monitored sequentially in 2008 (rural site, GEM: 2.37 ± 1.26 ng m^?3, daytime RGM flux: 29 ± 40 ng m^?2 day^?1). Photochemical conversion of GEM was not the primary RGM source, as highest net RGM gains (75.9 pg m^?3, 99.0 pg m^?3, 149 m^?3) occurred within 3.0–5.3 h, while the theoretical time required was 14–23 h. Instead, simultaneous peaks in RGM, Hg_p, ozone (O₃), nitrogen oxides, and sulfur dioxide in the late afternoon suggested short-range transport of RGM from the urban center to the rural site. The rural site was located more inland, where the average water vapor mixing ratio was lower compared to the other two sites (in 2008, rural: 5.6 ± 1.4 g kg^?1, urban: 9.0 ± 1.1 g kg^?1, cement plant: 8.3 ± 2.2 g kg^?1). Together, these findings suggested short-range transport of O₃ from an urban area contributed to higher RGM deposition at the rural site, while drier conditions helped sustain elevated RGM levels. Results suggested less urbanized environments may be equally or perhaps more impacted by industrial atmospheric Hg emissions, compared to the urban areas from where Hg emissions originated.     

Dissipation of sulfamethoxazole and trimethoprim antibiotics from manure-amended soils

In this study, the dissipation of two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TRM), in three soils under both aerobic and anaerobic conditions are evaluated. Under aerobic conditions, SMX dissipated rapidly through biodegradation but TRM was more persistent. Within the first 20 days in biologically active soils, >50% of the SMX was lost from the clay loam and loamy sand soils, and >80% loss was noted in the loam soil. Anaerobic dissipation of both compounds was more rapid than aerobic dissipation. The addition of manure to the soil only slightly increased the initial dissipation rate of the two compounds. Little effect was found on glucose mineralisation in soil following the addition of SMX and TRM, even as mixtures at high concentrations.     

PBDEs in serum and blubber of harbor, grey and harp seal pups from Eastern Canada

Serum and blubber of pup harbor (Phoca vitulina), grey (Halichoerus grypus) and harp (Phoca groenlandica) seals from the Estuary and the Gulf of St. Lawrence were analyzed for polybrominated diphenyl ethers (PBDEs). Concentrations of ∑PBDEs (on lipid weight basis) in tissues of harbor seal pups inhabiting the St. Lawrence Estuary were about five times higher than in those from a colony located in the northern Gulf. Harp seal pups have the lowest levels of ∑PBDEs among the seal species born in the Gulf of St. Lawrence. Lipid normalized concentrations of ∑PBDEs in serum and blubber were strongly correlated, suggesting that the blood collection as a less invasive method could be used to monitor ∑PBDEs in pups. This study shows that fluvial inputs of PBDEs are important to the St. Lawrence marine ecosystem and that inhabiting harbor seal pups have a substantial exposure to PBDEs at a critical developmental stage. In addition, the observed difference in PBDE levels between harp and grey or harbor seal pups from the Gulf of St. Lawrence is explained by the difference in diets of their mothers which is linked with their residency time in the Gulf and their seasonal migration pattern.     

Remediation of metal contaminated soil with mineral-amended composts

This study examined the use of two composts derived from green waste and sewage sludge, amended with minerals (clinoptilolite or bentonite), for the remediation of metal-contaminated brownfield sites to transform them into greenspace. Soils contaminated with high or low levels of metals were mixed with the mineral-enhanced composts at different ratios and assessed by leaching tests, biomass production and metal accumulation of ryegrass (Lolium perenne L.). The results showed that the green waste compost reduced the leaching of Cd and Zn up to 48% whereas the composted sewage sludge doubled the leachate concentration of Zn. However, the same soil amended with composted sewage sludge showed an efficient reduction in plant concentrations of Cd, Cu, Pb or Zn by up to 80%. The results suggest that metal immobilisation and bioavailability are governed by the formation of complexes between the metals and organic matter. The amendment with minerals had only limited effects.     

Implications of climate change for the stomatal flux of ozone: a case study for winter wheat

Climate change factors such as elevated CO2 concentrations, warming and changes in precipitation affect the stomatal flux of ozone (O3) into leaves directly or indirectly by altering the stomatal conductance, atmospheric O3 concentrations, frequency and extent of pollution episodes and length of the growing season. Results of a case study for winter wheat indicate that in a future climate the exceedance of the flux-based critical level of O3 might be reduced across Europe, even when taking into account an increase in tropospheric background O3 concentration. In contrast, the exceedance of the concentration-based critical level of O3 will increase with the projected increase in tropospheric background O3 concentration. The influence of climate change should be considered when predicting the future effects of O3 on vegetation. There is a clear need for multi-factorial, open-air experiments to provide more realistic information for O3 flux-effect modelling in a future climate.     

Investigations on the effect of chlorine in lubricating oil and the presence of a diesel oxidation catalyst on PCDD/F releases from an internal combustion engine

This paper reports on an intensive study into releases of polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated furans (PCDF) and polychlorinated biphenyls (PCB) from a diesel engine and the analysis of PCDD/F and PCB in crankcase lubricating oil. Experimental conditions were set and carefully controlled in order to maximize the possible impact of, and our ability to measure the effect of, changes in the levels of chlorine in the lubricant. Emissions to air were measured using modified EPA methods following the principles of the European EN 1948 standards. A series of 40 experimental runs were completed using three reference lubricants formulated to have three levels of chlorine present as a residual component (at levels of 12, 131 and 259 mg kg(-1) or ppm). The engine was run with and without the diesel oxidation catalyst. All lubricants were realistic oils and the use of unrealistic additives or doping of components - particularly chlorine - in the fuel and lubricant was carefully avoided. Analysis of fuel and lubricant (before and after testing) samples required strenuous attention to achieve acceptable recoveries and showed non-detectable levels of PCB and PCDD/F at a detection limit of around 1.5 ng I-TEQ kg(-1) (ppt), indistinguishable from the laboratory blank. The testing demonstrated the need for extreme care to be taken in developing measurement methods that are sufficiently sensitive for measuring chlorine content of fluids and PCDD/F in oils, the latter being particularly challenging. Mean emissions of PCDD/F with the diesel oxidation catalyst in place were 23 pg I-TEQ l(-1) of fuel and with the diesel oxidation catalyst removed 97 pg I-TEQ l(-1) of fuel. The results of this testing showed that the emissions of PCDD/F were greatly reduced by the presence of a diesel oxidation catalyst in the exhaust, a finding that has not been explicitly tested in previous work. They also show that emissions from the engine were not controlled by the level of chlorine in the lubricant and that emissions did not change in response to a much greater step change in the total chlorine entering the combustion chamber due to a change in the level of chlorine in the fuel. Emissions when the engine was configured with a diesel oxidation catalyst showed a consistent pattern that appears to be unique in the experience of the authors.