Roberto García-Ruiz

Spatial and seasonal variation in denitrification in the Swale–Ouse system, a river continuum

Rates of denitrification were studied in the sediments at five sites along the river continuum of the Swale–Ouse river system, NE England, together with one site on a highly eutrophic tributary (R. Wiske). Intact cores were taken on a monthly basis for 17 months and used to assess denitrification rates under simulated ambient conditions using acetylene blockage methodology. Within the headwater site (2.5 km upstream of start of main river) rates rarely exceeded 20 μmol N m−2 h−1. At the most downstream site (145.0 km down the main river and at the tidal limit) the maximum was 659 μmol N m−2 h−1. The highest rates on all sampling occasions were for the Wiske. Both spatial and seasonal trends were evident. A general trend for the rate to increase moving downstream can be explained largely by two factors: increase in ambient nitrate concentration and changes in sediment composition. Seasonally, a spring peak was evident at all sites, which can again be explained largely by two factors: temperature and nitrate concentration.

Denitrification and nitrous oxide production in sediments of the Wiske, a lowland eutrophic river

Abstract Denitrification rate and nitrous oxide production were investigated in sediments of the River Wiske, a lowland, nutrient-rich calcareous tributary of the River Swale, NE England. Slurries from samples taken on two occasions at the most downstream site were used to compare potential denitrifying activity at various depths; this activity decreased by about 40% between the 0–1 and 1–2 cm layers. Minimum and maximum values for 5-cm depth cores sampled at the same site from visually different sediments differed by a factor of four. Denitrification rate in cores measured monthly during 1996 showed the lowest values in winter, a peak in late spring and a subsequent decrease through summer and autumn. Nitrous oxide production showed a similar trend and accounted for 0–100% of total nitrogen gases produced by nitrate reduction, with an average value of 42%. Denitrification rate typically ranged over one order of magnitude on passing down the river. The relative importance of various environmental factors on denitrification rate was assessed by laboratory experimental studies, using previous data for nitrate and new studies on temperature and organic carbon. Temperature showed a different effect according to whether assays were carried out with cores or slurries; denitrification rate showed an increase up to 30°C, irrespective of the season of sampling. Addition of organic substrates had no detectable effect on denitrification rate, but did lead to a significant decrease in the proportion of nitrous oxide formed as a result of nitrate reduction. Limitations in current methodologies for assaying denitrification are discussed.

Changes in soil phosphatase activity and P transformation rates induced by application of N- and S-containing acid-mist to a forest canopy.

The indirect effects of acid-misting applied to tree canopies, on soil P availability, phosphatase activity and P mineralisation rates in a Sitka spruce (Picea sitchensis (Bong.) Carr) stand have been investigated. The treated trees, grouped according to five height classes, had for four years previously received acid mist consisting of a mixture of H2SO4 and NH4NO3 (pH 2.5) at concentrations of 3.2 mM H 1 and 1.6 mM each of NH 1 4 ; NO 2 3 and SO 22 4 : These simulate cloudwater composition in uplands affected by acidic deposition. Another group of mixed heightclass trees, received a double dose of acid mist. Control — no acid-misted-trees received only the usual precipitation inputs. The acid mist treatments had previously been found to induce a significant reduction in stem diameter growth, but no canopy visible injury symptoms were observed. Root bioassays had demonstrated the induction of P nutritional stress in acid-misted versus no acid-misted trees. Soil chemical analysis showed that acidifying inputs induced changes in the inorganic P subcycle by: (i) increasing acidity and P sorption capacity of the soils; and (ii) decreasing the concentration of labile inorganic P. We report here on changes in the organic P subcycle (phosphatase activity and gross mineralisation rates). We used a method which applies independent treatments to soil samples (control, HgCl 2-addition, HgCl2addition 1 autoclaving) to separate mineral solubilisation, organic mineralisation and immobilisation of solution P. Soil phosphatase activity was significantly lower under acid-misted trees (263.9mg pNP h 21 g 21 ) than under control trees (382.0 mg pNP h 21 g 21 ). Soils beneath double-dose acid-misted trees showed a 42% reduction in the labile inorganic P pool-size, and a 33% increase in the labile organic P poolsize, compared to soils under control trees. A pattern of decreasing net P solubilisation and gross P mineralisation rates with increasing acidmist dose-level was also found. Thus, the combined effects of acid-misting on the inorganic and organic P subcycles, in addition to the suggested effect of N saturation enhancing demand for P by the trees, may have induced P deficiency and reduced tree growth. The effects described are considered to be important factors in the forest decline syndrome. q 2000 Elsevier Science Ltd. All rights reserved.

Hydrological cycle and interannual variability of the aquatic community in a temporary saline lake (Fuente de Piedra, Southern Spain)

Fuente de Piedra is a shallow, temporary saline lake whoseseasonal behavior is strongly dependent on the annual hydrologicalbudget. In this study, we outline the characteristics of Fuente dePiedra Lake for two years that had different hydrological budgets.The high precipitations in 1989–90 caused the lake not to dry asusual, and decreased both salinity and the amplitude of changes.There were also differences in nutrient dynamics, with generallylower concentrations of soluble reactive phosphorus and ammonium,whereas in the more humid year nitrate showed a distinct maximum inwinter. Winter bloom chlorophyll a concentrations were alsomuch higher in 1989–90 (>600 μg l-1) but there wasalso a winter productive phase that was presumably poorly coupledwith consumption processes that predominate in spring. Planktonicassemblages were different between years. Highly halotolerantphytoplankton species (Dunaliella salina and D. viridis) became scarcer, and especially two previouslyunrecorded diatoms (Cyclotella sp. and Chaetoceros sp.)became dominant in the bloom time in the wet year. The speciesrichness of the zooplankton increased in the wet year, with newspecies appearing that were not collected during 1987–88(Branchinectella media, Daphnia mediterranea, Macrothrix sp.,Arctodiaptomus salinus, Cyclops sp., Sigara sp...).There was also a much higher development of macrophytes (Ruppiadrepanensis, Althenia orientalis, Lamprothamnium papulosum)and bird populations, especially flamingoes (Phoenicopterusruber).Important interannual variations in this sort of system pointto the need for long term studies to observe the whole range ofstates that define the lake as an entity.

Phosphorus fractionation and mobility in the food and faeces of hatchery reared rainbow trout (Onchorhynchus mykiss)

Abstract The fractionation of phosphorus in both food and faecal material of rainbow trout has been determined. The total phosphorus (TP) concentration in faeces was 8.25 mg P g −1 dry wt., approximately half that in the food (16.06 mg P g −1 dry wt.). Greater than 80% of the decrease between food and faeces could be accounted for by the uptake of calcium phosphate by the fish. Only 25% of the TP in food was readily labile but this fraction increased to 44% in faecal material. The release of phosphorus from food or faeces was investigated in the laboratory with and without the addition of formaldehyde. When bacterial activity was inhibited, soluble reactive phosphate (SRP) concentrations rapidly increased in the water phase and could account for the labile phosphorus fraction in food or faeces after 24 h of incubation. In the absence of formaldehyde, SRP was rapidly assimilated into bacterial biomass but concentrations of dissolved unreactive phosphate increased. The rate at which labile phosphorus was lost from food increased if the sample was shaken or the food pellets ground to a dust, but decreased slightly if the temperature was lowered. Leaching of SRP from sedimenting food or faecal material was estimated as about 5% of the soluble phosphorus load per tonne of fish produced. The bulk of this came from faecal solids.

Denitrification in sediments of the freshwater tidal Yorkshire Ouse

Studies were made on denitrification rate and nitrous oxide production in the 21-km freshwater tidal stretch of the Yorkshire Ouse. Denitrification was not detected in the water column at the most downstream site (Selby) under conditions likely to be the most favourable for this process. All but one sample of the sediment cores showed high activity per unit area, with values ranging up to 575 μmol N m−2 h−1. In contrast to all other measurements on the Swale–Ouse river system, values for denitrification rate at the most downstream site showed on three occasions a decrease in comparison with the next site upstream (Cawood). It is suggested that this may be due to sediment instability at this site. Experimental studies with sediment slurries made on two different dates showed an increase in denitrification rate at all sites in response to added nitrate, but none due to added glucose. However, a combination of nitrate and glucose added to slurries from the most upstream site (Naburn Weir) and assayed under low O2 conditions showed a significantly higher denitrification rate than with added nitrate alone.

The Spanish Transition to Industrial Metabolism: Long‐Term Material Flow Analysis (1860-2010)

The aim of this work is to reconstruct the main economy‐wide/material flow accounting indicators for the Spanish economy between 1860 and 2010. The main results indicate that from 1960 onward, the country saw a very rapid industrial transition based on the domestic extraction of quarry products and the import of fossil fuels and manufactured goods. Direct material consumption rose from 58.7 million tonnes (Mt) in 1860 to 570.2 Mt in 2010. In per capita terms, it rose from 2.76 tonnes per capita per year (t/cap/yr) to 11.61 t/cap/year. Of the decennial years studied in this article, a peak of 15.23 t/cap/yr occurs in the year 2000; the subsequent fall is explained by the crisis of 2008. Until 1930, Spain was a net exporter of resources, but since that year, and especially since 1960, it began to depend heavily on overseas resources. The physical trade balance per inhabitant in Spain was -0.01 t/cap/year in 1860 and today it is 2.45 t/cap/year. This process also reveals the change in consumption patterns, which became increasingly dependent on abiotic resources. In 1860, 98.1% of resources consumed was biomass, whereas today the figure is 16.2%. In all events, this article shows how, although the great transformation did not occur until 1960, before that date the country saw significant qualitative transformation, which did not involve relevant changes in the mobilization of resources.

Guidelines for Constructing Nitrogen, Phosphorus, and Potassium Balances in Historical Agricultural Systems

Changes in cropland intensification and extension and their socioeconomic consequences have been a topic mainly investigated by agrarian historians. Results of the nutrient balances of these historical agricultural systems with relatively closed nutrient cycles might have played an important role because long-term sustainability only is achieved when the replacement of nutrients match those harvested. Thus, the analysis of the nutrient balance of specific historical agricultural systems or management practices has been the focus of agrarian historians. However, many of these nutrient balances have failed to take into account specific processes of importance. In this study, we provide a guideline for constructing nitrogen, phosphorus, and potassium balances in historical agroecosystems at both crop and aggregated scales. A rationale for explaining the processes involved and the variables that must be taken into account is provided. We also apply the model for specific crops at a parish scale using a case study from 1752. In addition, we provide the basis for linking a specific outcome of the nutrient balance with the long-term sustainability of specific crops.

Utilizing Microbial Community Structure and Function to Evaluate the Health of Heavy Metal Polluted Soils

The aim of this chapter is to combine perspectives developed in soil ecology, microbiology and biochemistry into a common framework for evaluating the health of soils polluted with heavy metals.

Gross and net rates of nitrogen mineralisation in soil amended with composted olive mill pomace.

Olive mill pomace is the major waste product in the olive oil industry and composting these by-products for the purpose of recycling nutrients and organic matter is a sound environmental strategy. Yet little is known about the quantity and timing of nitrogen (N) release from composted olive mill pomace. This paper assesses both gross (using the (15)N dilution technique) and net (aerobic incubation) nitrogen (N) mineralisation and N(2)O emissions of soil amended with seven commercially available composts of olive mill pomace (COMP). All are currently produced in Andalusia and differ in the proportions of raw materials co-composted with the pomace. The absence of significant differences in net N or gross mineralisation and nitrification in COMP-amended soil compared with a control, except for COMP combined with poultry manure, highlighted the recalcitrant nature of the COMP-N. Applications of COMP are hence unlikely to supply available N in available forms, at least in the short-term. Furthermore, N(2)O emissions from COMP-amended soil were negligible and, therefore, applications in the field should not result in increased N loss through denitrification.