Phosphorus Retention in a Constructed Wetland System used to Treat Dairy Wastewater

The aim of this study was to develop an input/output mass balance to predict phosphorus retention in a five pond constructed wetland system (CWS) at Greenmount Farm, County Antrim, Northern Ireland. The mass balance was created using 14-months of flow data collected at inflow and outflow points on a weekly basis. Balance outputs were correlated with meteorological parameters, such as daily air temperature and hydrological flow, recorded daily onsite. The mass balance showed that phosphorus retention within the system exceeded phosphorus release, illustrating the success of constructed wetland systems to remove nutrients from agricultural effluent from a dairy farm. Pond 5 showed the greatest relative retention of 86%. Comparison of retention and mean air temperature highlighted a striking difference in trends between up-gradient and down-gradient ponds, with Ponds 1 and 2 displaying a positive quadratic relationship and ponds 3 through 5 displaying a negative quadratic relationship.

Limitations of instantaneous water quality sampling in surface-water catchments: Comparison with near-continuous phosphorus time-series data.

The validity of load estimates from intermittent, instantaneous grab sampling is dependent on adequate spatial coverage by monitoring networks and a sampling frequency that re?ects the variability in the system under study. Catchments with a ?ashy hydrology due to surface runoff pose a particular challenge as intense short duration rainfall events may account for a signi?cant portion of the total diffuse transfer of pollution from soil to water in any hydrological year. This can also be exacerbated by the presence of strong background pollution signals from point sources during low flows. In this paper, a range of sampling methodologies and load estimation techniques are applied to phosphorus data from such a surface water dominated river system, instrumented at three sub-catchments (ranging from 3 to 5 km2 in area) with near-continuous monitoring stations. Systematic and Monte Carlo approaches were applied to simulate grab sampling using multiple strategies and to calculate an estimated load, Le based on established load estimation methods. Comparison with the actual load, Lt, revealed signi?cant average underestimation, of up to 60%, and high variability for all feasible sampling approaches. Further analysis of the time series provides an insight into these observations; revealing peak frequencies and power-law scaling in the distributions of P concentration, discharge and load associated with surface runoff and background transfers. Results indicate that only near-continuous monitoring that re?ects the rapid temporal changes in these river systems is adequate for comparative monitoring and evaluation purposes. While the implications of this analysis may be more tenable to small scale ?ashy systems, this represents an appropriate scale in terms of evaluating catchment mitigation strategies such as agri-environmental policies for managing diffuse P transfers in complex landscapes.

Synthesis and Phosphorus Sulfur Bond-Cleavage Of 3'- Thiothymidylyl(3'5')Thymidine

The title compound is readily prepared from 5'-O-monomethoxytrityl-3'-thiothymidine (5); cleavage of the P–S bond can be accomplished by mild oxidative hydrolysis.

Cycloalkenyl Halide Substitution Reactions of Enantiopure Arene cis-Tetrahydrodiols with Boron, Nitrogen and Phosphorus Nucleophiles

Enantiopure arene cis-tetrahydrodiols of bromobenzene and iodobenzene have been obtained in good yields, from chemoselective hydrogenation (rhodium-graphite) of the corresponding cis-dihydrodiol metabolites. Palladium-catalysed substitution of the halogen, by hydrogen, boron, nitrogen and phosphorus nucleophiles, in the acetonide derivatives, has yielded highly functionalised products for application in synthesis with potential as scaffolds for chiral ligands.

THE CHEMISTRY OF PHOSPHORUS IN HOT MOLECULAR CORES

Hot molecular cores in star-forming regions are known to have gas-phase chemical compositions determined by the material evaporated from the icy mantles of interstellar grains, followed by subsequent reactions in the gas phase. Current models suggest that the evaporated material is rich in hydrogenated species. In this paper, we consider the chemistry induced in a hot core by the release of phosphine, PH3 from interstellar grains. We find that PH3 is rapidly destroyed by a series of reactions with atomic hydrogen and is converted, within 10(4) yr, into atomic P, and PO and PN, with P atoms being the most abundant species. Other P-bearing molecules can be formed in the hot gas, but on time-scales that are long compared to those of the hot cores.

PHOSPHORUS CHEMISTRY IN DENSE INTERSTELLAR CLOUDS

I have used recent laboratory studies on the reactions of the phosphorus hydride ions, PH(n)+ (n = 0-4) to construct a new model of phosphorus chemistry in interstellar clouds. I find that the non-detection of PN in cold, dark clouds in consistent with the chemical models only if the depletion of phosphorus in large, approximately 10(4) in TMC-1. Although the laboratory studies indicate that organo-phosphorus chains C(n)P can be formed, this large depletion precludes the detection of any phosphorus-bearing moleclues in cold clouds. However, in warm clouds associated with star formation, the depletion of phosphorus may be reduced. In this case one can reproduce the PN abundance toward Orion KL with a depletion factor of about 300. Interestingly, if the organo-phosphorus species are not destroyed by O atoms, I predict fractional abundances in Ori KL of between 10(-11) and 10(-10) for C(n)P (n = 2-4) and HCCP.

Approaches to the Implementation of the Water Framework Directive: Targeting Mitigation Measures at Critical Source Areas of Diffuse Phosphorus in Irish Catchments

The Water Framework Directive (WFD) has initiated a shift towards a targeted approach to implementation through its focus on river basin districts as management units and the natural ecological characteristics of waterbodies. Due to its role in eutrophication, phosphorus (P) has received considerable attention, resulting in a significant body of research, which now forms the evidence base for the programme of measures (POMs) adopted in WFD River Basin Management Plans (RBMP). Targeting POMs at critical sources areas (CSAs) of P could significantly improve environmental efficiency and cost effectiveness of proposed mitigation strategies. This paper summarises the progress made towards targeting mitigation measures at CSAs in Irish catchments. A review of current research highlights that knowledge related to P export at field scale is relatively comprehensive however; the availability of site-specific data and tools limits widespread identification of CSA at this scale. Increasing complexity of hydrological processes at larger scales limits accurate identification of CSA at catchment scale. Implementation of a tiered approach, using catchment scale tools in conjunction with field-by-field surveys could decrease uncertainty and provide a more practical and cost effective method of delineating CSA in a range of catchments. Despite scientific and practical uncertainties, development of a tiered CSA-based approach to assist in the development of supplementary measures would provide a means of developing catchment-specific and cost-effective programmes of measures for diffuse P. The paper presents a conceptual framework for such an approach, which would have particular relevance for the development of supplementary measures in High Status Waterbodies (HSW). The cost and resources necessary for implementation are justified based on HSWs’ value as undisturbed reference condition ecosystems.