Impact of land drainage on peatland hydrology

There is a long history of drainage of blanket peat but few studies of the long-term hydrological impact of drainage. This paper aims to test differences in runoff production processes between intact and drained blanket peat catchments and determine whether there have been any long-term changes in stream flow since drainage occurred. Hillslope runoff processes and stream discharge were measured in four blanket peat catchments. Two catchments were drained with open-cut ditches in the 1950s. Ditching originally resulted in shorter lag times and flashier storm hydrographs but no change in the annual catchment runoff efficiency. In the period between 2002 and 2004, the hydrographs in the drained catchments, while still flashy, were less sensitive to rainfall than in the 1950s and the runoff efficiency had significantly increased. Drains resulted in a distinctive spatial pattern of runoff production across the slopes. Overland flow was significantly lower in the drained catchments where throughflow was more dominant. In the intact peatlands, matrix throughflow produced by peat layers below 10 cm was rare and produced <1% of the runoff. However, in drained peatlands, matrix throughflow in deeper peat layers was common and provided around 23% of the runoff from gauged plots. Macropore flow, the density of soil piping, and pipeflow were significantly greater in drained peatlands than in intact basins. Gradual changes to peat structure could explain the long-term changes in river flow, which are in addition to those occurring in the immediate aftermath of peatland drainage.     

ESTIMATING NUTRIENT AND SEDIMENT THRESHOLD CRITERIA FOR BIOLOGICAL IMPAIRMENT IN PENNSYLVANIA WATERSHEDS1

ABSTRACT: This study employs a simple nonlinear statistical approach to establish nitrogen, phosphorus, and sediment concentration and unit area load thresholds to aid in the evaluation of aquatic biological health of watersheds within the state of Pennsylvania. Flow, nitrogen and phosphorus species, sediment, basin area, land cover, and biological assessment data were assembled for 29 Pennsylvania watersheds. For each watershed, rating curves depicting flow versus load relationships were developed using the U.S. Environmental Protection Agency's (USEPA's) storage and retrieval database (STORET) flow and concentration data, then applied to daily flow data obtained from U.S. Geological Survey (USGS) daily flow gauging stations to estimate daily load between 1989 and 1999. The load estimates and concentration data were then sorted into six sets of data: mean annual unit area nitrogen, phosphorus, and sediment loads; and average nitrogen, phosphorus, and sediment concentrations. Results of Mann‐Whitney tests conducted on each of the six datasets indicate that there is a statistically significant difference between the concentrations and unit area loads of nitrogen, phosphorus, and sediment in impaired and unimpaired watersheds. Concentration thresholds, calculated as the midpoint between the impaired and unimpaired watersheds’ 95 percent confidence interval for the median, were estimated to be 2.01 mg/L, 0.07 mg/L, and 197.27 mg/L for nitrogen, phosphorus, and sediment, respectively. Annual unit area load thresholds were estimated to be equal to 8.64 kg/ha, 0.30 kg/ha, and 785.29 kg/ha, respectively, for nitrogen, phosphorus, and sediment species.     

Carbon dioxide flux as affected by tillage and irrigation in soil converted from perennial forages to annual crops

Among greenhouse gases, carbon dioxide (CO(2)) is one of the most significant contributors to regional and global warming as well as climatic change. A field study was conducted to (i) determine the effect of soil characteristics resulting from changes in soil management practices on CO(2) flux from the soil surface to the atmosphere in transitional land from perennial forages to annual crops, and (ii) develop empirical relationships that predict CO(2) flux from soil temperature and soil water content. The CO(2) flux, soil temperature (T(s)), volumetric soil water content (theta(v)) were measured every 1-2 weeks in no-till (NT) and conventional till (CT) malt barley and undisturbed soil grass-alfalfa (UGA) systems in a Lihen sandy loam soil (sandy, mixed, frigid Entic Haplustoll) under irrigated and non-irrigated conditions in western North Dakota. Soil air-filled porosity (epsilon) was calculated from total soil porosity and theta(v) measurements. Significant differences in CO(2) fluxes between land management practices (irrigation and tillage) were observed on some measurement dates. Higher CO(2) fluxes were detected in CT plots than in NT and UGA treatments immediately after rainfall or irrigation. Soil CO(2) fluxes increased with increasing soil moisture (R(2)=0.15, P<0.01) while an exponential relationship was found between CO(2) emission and T(s) (R(2)=0.59). Using a stepwise regression analysis procedure, a significant multiple regression equation was developed between CO(2) flux and theta(v), T(s) (CO(2) [Formula: see text] ; R(2)=0.68, P0.01). Not surprisingly, soil temperature was a driving factor in the equation, which accounted for approximately 59% in variation of CO(2) flux. It was concluded that less intensive tillage, such as no-till or strip tillage, along with careful irrigation management will reduce soil CO(2) evolution from land being converted from perennial forages to annual crops.     

ASsessment Of Alcohol Ethoxylate Surfactants And Fatty Alcohols Mixtures In River Sediments And Prospective Risk Assessment

A feasible and relatively readily available analytical method was adapted for the assessment of alcohol ethoxylates (AE) and fatty alcohols (FA) in sediments. This study illustrates the simultaneous measurement of 38 of 114 possible alcohol ethoxylate ethoxymers (AE) and fatty alcohols (FA) found in commercially important AE products. We predicted toxicity for all identified fractions, as well as the total mixture toxicity, relative to three exposure scenarios via sewage treatment plants (STP) for these widely used chemicals in consumer products and hence generate a preliminary environmental risk screening for AE and FA in sediments. The method is based on derivatization of solvent or solid-phase extracts with 2-fluoro-N-methylpyridinium p-toluenesulfonate (Pyr+). The derivatized extracts were analyzed with liquid chromatography/mass spectrometry (LC/MS) operating in the positive ion electrospray mode. The extraction efficiency of AE and FA in three different sediments of varying composition was evaluated with spike-recovery studies, ranging from 64% to 80%. The detection limits for individual ethoxymers typically ranged from 1 to 5ngg⁻¹on a dry weight basis. The mean limit of detection (LOD) was 6ngg⁻¹and the median LOD was 3ngg⁻¹. AE and FA in sediments were found to be stable for two weeks if preserved with 3% (v/v) formalin and stored at 4–6^∘C. Based on equilibrium partitioning, background concentrations of AE and FA were predicted to be below concentrations known to elicit chronically toxic effects. Total worst case mixture toxicities for all AE ethoxymers combined with FA were predicted to result in a risk quotient less than 0.6. Activated sludge treatment (STP) significantly reduced the release of total AE and FA by four-fold, suggesting that the total mixture risk quotient would be < 0.15 for sediment dependent organisms.     

A rapid and accurate method for the determination of plutonium in food using magnetic sector ICP-MS with an ultra-sonic nebuliser and ion chromatography

In the event of a nuclear incident it is essential that analytical information on the distribution and level of contamination is available. An ICP-MS method is described which can provide data on plutonium contamination in food within 3 h of sample receipt without compromising detection limits or accuracy relative to traditional counting methods. The method can also provide simultaneous determinations of americium and neptunium. Samples were prepared by HNO3 closed-vessel microwave digestion, evaporated to dryness and diluted into a mobile phase comprising 1.5 M HNO3 and 0.1 mM 2,6-pyridinedicarboxylic acid. A commercially available polystyrene-divinylbenzene ion chromatography column provides on-line separation of 239Pu and 238U reducing the impact of the 238U1H interference. Oxidation of the sample using H2O2 ensures all Pu is in the Pu(+4) state. The oxidation also displaces Np away from the solvent front by changing the oxidation state from Np(+3) to Np(+4) and produces the insoluble Am(+4) ion. Simultaneous Pu, Am and Np analyses therefore require omission of the oxidation stage and some loss of Pu data quality. Analyses were performed using a magnetic sector ICP-MS (Finnigan MAT Element). The sample is introduced to the plasma via an ultrasonic nebuliser-desolvation unit (Cetac USN 6000AT+). This combination achieves an instrumental sensitivity of 238U > 2 x 10(7) cps/ppb and removes hydrogen from the sample gas, which also inhibits the formation of 238U1H. The net effect of the improved sample introduction conditions is to achieve detection levels for Pu of 0.020 pg g(-1) (4.6 x 10(-2) Bq kg(-1)) which is significantly below 1/10th of the most stringent EU (European Union) legislation, currently 0.436 pg g(-1) (1 Bq kg(-1)) set for baby food. The new method was evaluated with a range of biological samples ranging from cabbage to milk and meat. Recovery of Pu agrees with published values (100% +/- 20%).     

The influence of water vapour on the determination of glutaraldehyde vapour concentrations using an electrochemical fuel cell sensor

The effects of relative humidity (40-90% RH) and varying glutaraldehyde vapour concentrations (< 0.1 ppm) on the response of an electrochemical fuel cell sensor have been investigated over time (0-400 s). These studies have identified changes in the response of the fuel cell with time after sampling. In particular, it has been found that the maximum cell output for water vapour occurs ca. 10 s after sampling whilst the response to glutaraldehyde occurs much later (> 100 s). For mixtures containing different ratios of water and glutaraldehyde vapours, the time taken to reach maximum fuel cell response varies between 10 and 100 s, depending on the ratio of the two vapours. For instance, glutaraldehyde vapour containing higher % RH has been found to result in shorter times to reach maximum fuel cell response. A comparison was made between measuring glutaraldehyde vapour concentrations in the presence of water vapour at the maximum fuel cell response and also at a fixed interval (240 s) after sampling. Such a comparison resulted in a reduction in the standard error from 36% to 5% for a glutaraldehyde vapour sample (0.023 ppm) measured at different values of relative humidity (40 to 80%). Examination of the effect of the sample volume (30-60 ml) on the response of the fuel cell shows, as expected, an approximate doubling of the fuel cell response. Optimisation of the fuel cell measurement parameters to measure a 60 ml sample leads to a lowering of the limit of detection from 0.083 ppm (for data taken at the maximum cell response) to 0.017 ppm for data measured 240 s after sampling. In the light of recent reductions in the legal limits for exposure to glutaraldehyde, this has important implications for the measurement of glutaraldehyde vapour in the workplace.     

A Comparison of Loch Chemistry from 1955 and 1999 in the Cairngorms,N.E. Scotland

The Cairngorms in north-east Scotland is remote from pollutant sources although it currently receives ca. 10 kg ha¹ yr¹ S and ca. 11 kg ha¹ yr¹ N deposition from the atmosphere.In 1955, 15 lochs (lakes) at a range of altitudes were sampled and analysed for major ion concentrations. A new survey of these and an additional 23 lochs and their catchment soils was conducted in 1999 to determine the impact of acid deposition, and the changes in loch chemistry since the 1955 survey. The bedrock geology of this region has a strong influence on the loch chemistry. Surface waters were generally more acidic in high altitude areas due to predominantly poorly buffered, thin alpine soils developed on granitic parent material (mean acid neutralising capacity (ANC) for 23 lochs = 30 eq L¹). At lower altitudes where the geology is dominated by Dalradian metamorphic rocks surface waters are comparatively base rich and have higher ANC (mean ANC for 15 lochs = 157 eq L¹). Surface water nitrate concentrations show a negative relationship with soil C:N status, in that higher nitrate only occurs at low soil C:N ratios. A comparison of data for 1955 and 1999 shows that sulphate concentrations are significantly lower (67.8 and 47.5 eq L¹, respectively), and pH has improved (pH 5.6 and 5.9) in response to decreased S deposition since the mid 1970s. However, mean nitrate concentrations were found to increase from 2.48 >eq L¹ in 1955 to 5.65 eq L¹ in 1999. Differences in the sampling and laboratory methods from 1955 and 1999 are acknowledged in the interpretation of data.     

Egg incubation temperature affects male reproductive success but not display behaviors in lizards

The complex ritualized displays of males in many territorial species suggest that selection has shaped male behaviors in ways that affect fitness. In this study, we evaluated the link between display behavior during male–male interactions and reproductive success in the Australian jacky dragon (Amphibolurus muricatus), a lizard species that uses a complex series of movement patterns for communication. We quantified variation in male display behaviors by using video playback experiments in the laboratory, and subsequently assessed variation in male reproductive success by paternity analyses of offspring. Because the lizards used in this study came from eggs incubated under three thermal environments, we also could evaluate the impact of developmental temperature on adult behavior and reproductive success. Incubation temperature had a strong effect on male reproductive success; males produced under intermediate temperatures sired more offspring than those produced under extreme developmental temperatures. However, incubation temperature did not affect male display behavior, nor was male behavior associated with reproductive success. Our findings do not support the common assumption that display behaviors used during male–male interactions affect reproductive success.     

Who counts in evaluating the effects of air pollution policies on households? Non-market valuation in the presence of dependencies

Individuals who are likely to realize the largest benefits from improvements in air quality often depend on other members of their households to make time or monetary contributions to their care. The presence of these dependency relationships among household members poses challenges for benefit estimation since it is unlikely that the conditions necessary for recovering the underlying individual preferences from household choices are satisfied in this setting. We propose a conceptual framework that highlights the role of these dependencies in the choice models used to estimate the willingness to pay for environmental quality improvements. We design a complementary stated preference survey that describes hypothetical dependency relationships for household members of different ages to test the implications of our conceptual model. Respondents' stated choices take into account the proposed care-giving responsibilities for young children and teenagers but not for older adults.