The Importance of Selecting Appropriate Criteria for Calculating Acidity Critical Loads for Terrestrial Ecosystems Using the Simple Mass Balance Equation

The Simple Mass Balance (SMB) equationis commonly used throughout Europe for thecalculation of acidity critical loads for forestsoils. Different criteria can be set in themodel depending on whether the receptor (e.g. treeroots) is more sensitive to the toxic effects ofaluminium or to unfavourable pH conditions. Thispaper examines the effects on critical loadscalculations of using different criteria andcritical limits, and demonstrates the importanceof selecting the most appropriate and justifiablecriteria for the chosen receptor, since they caneffect the critical loads values obtained. Abrief review of the range of different criteriaand limits used throughout Europe is included. In addition, the gibbsite equilibrium constant,used in the SMB equation to represent therelationship between dissolved aluminium andhydrogen ions in soil solution, is discussed. This relationship is not generally described inthe literature as a criterion in the equation,but this work highlights the effects differentgibbsite values have on critical loadcalculations and the importance of applying themost appropriate value for the soil in therooting zone of the receptor.     

Cross-correlation bias in lag analysis of aquatic time series

Cross-correlation analysis is the most valuable and widely used statistical tool for evaluating the strength and direction of time-lagged relationships between ecological variables. Although it is well understood that temporal autocorrelation can inflate estimates of cross correlations and cause high rates of incorrectly concluding that lags exist among time series (i.e. type I error), in this study we show that a problem we term intra-multiplicity can cause substantial bias in cross-correlation analysis even in the absence of autocorrelation. Intra-multiplicity refers to the numerous time lags examined and cross-correlation coefficients computed within a pair of time series during cross-correlation analysis. We show using Monte Carlo simulations that intra-multiplicity can spuriously inflate estimates of cross correlations by identifying incorrect time lags. Further, unlike autocorrelation, which generally identifies lags close to the true lag, intra-multiplicity can erroneously identify lags anywhere in the time series and commonly results in a direction change of the correlation (i.e. positive or negative). Using Monte Carlo simulations we develop formulas that quantify the bias introduced by intra-multiplicity as a function of sample size, true cross correlation between the series, and the number of time lags examined. A priori these formulas enable researchers to determine the sample size needed to minimize the biases introduced by intra-multiplicity. A posteriori the formulas can be used to predict the expected bias and type I error rate associated with the data at hand, as well as the maximum number of time lags that can be analyzed to minimize the effects of intra-multiplicity. We examine the relationship between commercial catch of chum salmon and surface temperatures of the North Pacific (1925–1992) to illustrate the problems of intra-multiplicity in fisheries studies and the application of our formulas. These analyses provide a more robust framework to assess the temporal relationships between ecological variables. Received: 28 July 2000 / Accepted: 6 December 2000     

Influence of environmental factors on burrow irrigation and oxygen consumption in the mudflat invertebrate Urechis caupo

We examined burrow irrigation activity by the mudflat worm Urechis caupo in response to suspended food, ambient hypoxia (down to 3.3 kPa PO₂), hydrogen sulfide exposure (up to 100 µmol l^-1), and short-term temperature change (range 10-22°C). In normoxic, nutrient-free water at 14°C, O₂ consumption ( [(M)\dot]O₂ ) \left( {\dot M{\rm O}_2 } \right) was 45 nmol min^-1 g^-1, water flow rate ( [(V)\dot]_W ) \left( {\dot V_{\rm W} } \right) was 27 ml min^-1 (0.66 ml min^-1 g^-1), frequency of peristaltic waves (F_P) was 2.6 contractions min^-1, stroke volume (SV) was 11 ml, and O₂ extraction coefficient (EO₂) was 0.27. Adding suspended food to the burrow water occasionally elicited stereotypical feeding behavior but had no effect on any measured variables during nonfeeding periods. Hypoxia greatly decreased [(M)\dot]O₂ \dot M{\rm O}_2 (75% reduction at 3.3 kPa PO₂) but did not affect [(V)\dot]_W \dot V_{\rm W} , F_P, SV, or EO₂. Sulfide at 50 µmol l^-1 or less had no effect on burrow irrigation activity, whereas 100 µmol l^-1 sulfide decreased [(V)\dot]_W \dot V_{\rm W} by 58% and F_P by 50% but had no effect on SV. Temperature strongly affected [(V)\dot]_W \dot V_{\rm W} (Q₁₀ of 1.9 from 10°C to 22°C). We propose that U. caupo's ability to live in the hypoxic, sulfidic mud of productive mudflat environments, combined with its very efficient mucous net, allows it to process much less water for feeding than other suspension-feeding invertebrates. This, in turn, necessitates an efficient O₂ extraction mechanism, which is provided by the water lung activity of U. caupo's unique hindgut.     

Characterization of air manganese exposure estimates for residents in two Ohio towns

This study was conducted to derive receptor-specific outdoor exposure concentrations of total suspended particulate (TSP) and respirable (d_ae ≤ 10 µm) air manganese (air-Mn) for East Liverpool and Marietta (Ohio) in the absence of facility emissions data, but where long-term air measurements were available. Our “site-surface area emissions method” used U.S. Environmental Protection Agency’s (EPA) AERMOD (AMS/EPA Regulatory Model) dispersion model and air measurement data to estimate concentrations for residential receptor sites in the two communities. Modeled concentrations were used to create ratios between receptor points and calibrated using measured data from local air monitoring stations. Estimated outdoor air-Mn concentrations were derived for individual study subjects in both towns. The mean estimated long-term air-Mn exposure levels for total suspended particulate were 0.35 μg/m³ (geometric mean [GM]) and 0.88 μg/m³ (arithmetic mean [AM]) in East Liverpool (range: 0.014–6.32 μg/m³) and 0.17 μg/m³ (GM) and 0.21 μg/m³ (AM) in Marietta (range: 0.03–1.61 μg/m³). Modeled results compared well with averaged ambient air measurements from local air monitoring stations. Exposure to respirable Mn particulate matter (PM₁₀; PM <10 μm) was higher in Marietta residents.

Implications: Few available studies evaluate long-term health outcomes from inhalational manganese (Mn) exposure in residential populations, due in part to challenges in measuring individual exposures. Local long-term air measurements provide the means to calibrate models used in estimating long-term exposures. Furthermore, this combination of modeling and ambient air sampling can be used to derive receptor-specific exposure estimates even in the absence of source emissions data for use in human health outcome studies.     

A metabolomics based approach to assessing the toxicity of the polyaromatic hydrocarbon pyrene to the earthworm Lumbricus rubellus

The biochemical response of the earthworm Lumbricus rubellus to pyrene exposure was assessed using 1H nuclear magnetic resonance (NMR) spectroscopy, gas chromatography mass spectrometry (GC-MS) and pattern recognition techniques. Both analytical methods enabled the establishment of reproducible metabolic profiles. NMR analysis identified a total of 32 metabolites while GC-MS identified 51. The results demonstrate that not only is pyrene toxic to L. rubellus, but that alterations in its normal metabolic profile could be observed even when individuals were exposed to concentrations of 40mg kg(-1): a pollution level that is both below the concentration previously found to significantly reduce reproduction and within the range of polycyclic aromatic hydrocarbons (PAHs) found on some contaminated sites. Pyrene was found to cause a dose dependant decrease in lactate and the concentrations of the saturated fatty acids tetradecanoic, hexadecanoic and octadecanoic acid and an increase in production of the amino acids alanine, leucine, valine, isoleucine, lysine, tyrosine and methionine. It is proposed that this indicates impaired glucose metabolism, with an associated increase in fatty acid metabolism and changes in TCA cycle intermediates. This study demonstrates the versatility of metabolomics as a tool to monitor toxicity in the environment as opposed to utilising model species studied in a laboratory setting. Since it is a non-carcinogenic PAH, we propose that the metabolic changes observed in worms may reflect the non-specific toxic effects of pyrene as a typical, non-polar organic compound.     

Assumptions in ecosystem service assessments: Increasing transparency for conservation

Conservation efforts are increasingly supported by ecosystem service assessments. These assessments depend on complex multi-disciplinary methods, and rely on a number of assumptions which reduce complexity. If assumptions are ambiguous or inadequate, misconceptions and misinterpretations may arise when interpreting results of assessments. An interdisciplinary understanding of assumptions in ecosystem service science is needed to provide consistent conservation recommendations. Here, we synthesise and elaborate on 12 prevalent types of assumptions in ecosystem service assessments. These comprise conceptual and ethical foundations of the ecosystem service concept, assumptions on data collection, indication, mapping, and modelling, on socio-economic valuation and value aggregation, as well as about using assessment results for decision-making. We recommend future assessments to increase transparency about assumptions, and to test and validate them and their potential consequences on assessment reliability. This will support the taking up of assessment results in conservation science, policy and practice.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01379-9) contains supplementary material, which is available to authorized users.     

Influence of particle size distribution on anaerobic degradation of phenol and analysis of methanogenic microbial community

Sludge morphology considerably affects the mechanism underlying microbial anaerobic degradation of phenol. Here, we assessed the phenol degradation rate, specific methanogenic activity, electron transport activity, coenzyme F420 concentration, and microbial community structure of five phenol-degrading sludge of varying particle sizes (i.e., < 20, 20–50, 50–100, 100–200, and > 200 μm). The results indicated an increase in phenol degradation rate and microbial community structure that distinctly correlated with an increase in sludge particle size. Although the sludge with the smallest particle size (< 20 μm) showed the lowest phenol degradation rate (9.3 mg COD·gVSS−1 day−1), its methanogenic activity with propionic acid, butyric acid, and H2/CO2 as substrates was the best, and the concentration of coenzyme F420 was the highest. The small particle size sludge did not contain abundant syntrophic bacteria or hydrogenotrophic methanogens, but contained abundant acetoclastic methanogens. Moreover, the floc sizes of the different sludge varied in important phenol-degrading bacteria and archaea, which may dominate the synergistic mechanism. This study provides a new perspective on the role of sludge floc size on the anaerobic digestion of phenol.