Determining the sources of nutrient flux to water in headwater catchments: Examining the speciation balance to inform the targeting of mitigation measures.

Diffuse water pollution from agriculture (DWPA) is a major environmental concern, with significant adverse impacts on both human and ecosystem health. However, without an appropriate understanding of the multiple factors impacting on water, mitigation measures cannot be targeted. Therefore, this paper addresses this gap in understanding, reporting the hydrochemical monitoring evidence collected from the UK Government's Demonstration Test Catchments (DTC) programme including contrasting chalk and clay/mudstone catchments. We use data collected at daily and sub-daily frequency over multiple sites to address: (1) How does the behaviour of the full range of nitrogen (N) species and phosphorus (P) fractions vary? (2) How do N species and P fractions vary inter- and intra-annually? (3) What do these data indicate about the primary pollution sources? And (4) which diffuse pollution mitigation measures are appropriate in our study landscapes? Key differences in the rates of flux of nutrients were identified, dependent on catchment characteristics. Full N speciation and P fractionation, together with dissolved organic carbon (DOC) enabled identification of the most likely contributing sources in each catchment. Nitrate (NO3-N) was the dominant N fraction in the chalk whereas organic and particulate N comprised the majority of the load in the clay/mudstone catchments. Despite current legislation, orthophosphate (PO4-P) was not found to be the dominant form of P in any of the catchments monitored. The chalk sub-catchments had the largest proportion of inorganic/dissolved organic P (DOP), accompanied by episodic delivery of particulate P (PP). Contrastingly, the clay/mudstone sub-catchments loads were dominated by PP and DOP. Thus, our results show that by monitoring both the inorganic and organic fractions a more complete picture of catchment nutrient fluxes can be determined, and sources of pollution pin-pointed. Ultimately, policy and management to bring nutrient impacts under control will only be successful if a multi-stressor approach is adopted.

Mitigating diffuse phosphorus transfer from agriculture according to cost and efficiency.

Potential options for mitigating phosphorus (P) transfer from agriculture to water in England and Wales (E&W) were collated across a range of farm systems to assess their potential effectiveness in reducing mass of P transferred and potential cost (pounds sterling [ pound]) to the farming industry. A simple model framework (called PEASE) incorporating a number of assumptions was used to identify 15 methods for mitigating inputs of P to agricultural systems, 19 methods for preventing mobilization of P, and six methods for controlling the transport of P to streams. The scope for largest reductions in P inputs was to grassland and horticulture. Potential reductions in P mobilization were up to 1.2 kg P ha(-1). Reductions in P transfer associated with transport mitigation were larger than those associated with input and mobilization methods (up to 2.2 kg P ha(-1)). The largest estimated reductions were achieved by installing buffer zones and constructed wetlands, the former being very cost effective ( pound3-5 kg(-1) P saved). Plots of cost curves helped identify where the combined and cumulative P transfer reductions were attainable; these were approximately 0.2 kg ha(-1) for uplands, 0.6 kg ha(-1) for outdoor pigs, 0.9 kg ha(-1) for intensive dairy, and 2.2 kg ha(-1) for arable examples. We concluded that established catchment-scale evidence for mitigation is sparse, especially for specific farm systems in E&W. Sensitivities and uncertainties in the approach, especially associated with expert coefficients, are noted. This approach is nonetheless considered useful for prioritizing where and how best options might be most effectively targeted for least cost but greatest benefit.

Characterization of phosphorus sources in rural watersheds.

Correct identification of P sources in rural watersheds is critical for the development of cost-effective measures to combat agriculturally-driven eutrophication. The chemical composition of various storm runoff types (field surface runoff, field drain outfalls, roads, farmyards, and septic tanks) and the receiving streams in three micro (<10 km(2)) watersheds of varying agricultural intensity were monitored over a 2-yr period. Mean weekly stream soluble reactive phosphorus (SRP) and total phosphorus (TP) concentrations increased from 29 and 69 microg L(-1), respectively in the watershed with the lowest intensity agriculture to 382 and 503 microg L(-1), respectively in the watershed with high intensity agriculture and a village sewage treatment works. Concentrations of TP in storm runoff varied by up to two orders of magnitude reflecting the complex origins, routing, and composition of contributing source areas. Application of the DESPRAL test suggested field runoff TP concentrations were influenced by both P and organic matter in soil. However, runoff from impervious surfaces (farmyard and roads), and/or influenced by septic tank discharges, was significantly more concentrated (0.08-16 mg TP L(-1), mean >>1 mg L(-1)) than surface and subsurface runoff from cultivated land and pasture (0.02-3.6 mg TP L(-1), mean <1 mg L(-1)), and/or contained a significantly greater proportion (>50% vs. <50%) of P in dissolved forms. It is concluded that P sources associated with the functioning of rural communities (impervious surfaces, detergents, and wastewater) may be more ecologically relevant than those associated with agriculture and should be better quantified and controlled to avoid localized eutrophication impacts.

Particulate phosphorus transport by sub-surface drainage from agricultural land in the UK. Environmental significance at the catchment and national scale.

Phosphorus (P) is the key limiting nutrient in most UK freshwater systems. With increased legislation controlling point source inputs, dissolved (DP) and particulate P (PP) derived from diffuse sources are making a more significant contribution to the total P loading of surface waters. Recent research has focused on pathways linking diffuse sources to the fluvial system and sub-surface field drains have been shown to transport both sediment and P rapidly to watercourses. Preliminary results are presented from an ongoing study using environmental tracers to identify the source of the drain sediment and its potential as a carrier of PP. These results suggest that the majority of sediment in drains is topsoil derived, but the significance of P loss via this pathway in a regional or UK context has yet to be evaluated. A protocol to study the potential problem at a regional/national scale is discussed and initial data presented.

Comparison of cimetidine (Tagamet) with antacid for safety and effectiveness in reducing gastric acidity before elective cesarean section.

One hundred twenty-six parturients for elective cesarean section under general anesthesia were allocated to either a cimetidine or an antacid group in a randomized, double-blind, multicenter trial. The cimetidine-treated group received 300 mg cimetidine orally the evening before the operation and 300 mg intramuscularly between 1 and 3 h preoperatively. The antacid-treated group received 30 ml of Mylanta-II orally on both occasions. Gastric volume, 30 min after induction of anesthesia and 30 min before response to oral commands, was less in the cimetidine-treated group. Gastric pH 30 min after induction was greater in the cimetidine-treated group. The maternal serum level of cimetidine at birth was 1.31 +/- 0.12 micrograms/ml and the umbilical venous level was 0.78 +/- 0.05 micrograms/ml. The neonatal gastric acidity, Apgar scores, and Early Neonatal Neurobehavioral Scale (ENNS) scores were similar in both groups. No maternal or neonatal complication was attributed to treatment.

Obesity, gravity, and spread of epidural anesthesia.

Epidural anesthesia was administered for cesarean section in 250 patients using 20 ml of 0.75% bupivacaine administered at L3-4 with the patient in a sitting position for 5 minutes. Comparing the results with those obtained in a previous study in which parturients were kept horizontal at all times, it was found that the sitting position limited cephalad spread of anesthesia only in obese patients and that the decrease in spread was in proportion to the degree of obesity. The previous findings that cephalad spread is positively correlated to body mass index BMI (weight in kilograms divided by height in meters squared) and with body weight were confirmed.

Caesarean section associated with gross obesity.

The anaesthetic and surgical problems associated with Caesarean section in eight grossly obese patients (weight 150-204 kg) are described. In addition to an increase in the frequency and severity of the complications of obesity, those weighing more than 150 kg present a panniculus which may weigh 70 kg. Extradural analgesia was used for three patients and general anaesthesia for five (two because of fetal distress). One fetus died in utero after serious and prolonged arterial hypotension in the mother caused by powerful cephalad retraction of the panniculus (extradural analgesia). General anaesthesia was associated with severe episodes of hypertension in two patients.