Copper contamination affects the biogeochemical cycling of nitrogen in freshwater sediment mesocosms

Trace elements can have a wide variety of effects on microbial populations and their function in the aquatic environment. However, specific impacts on chemical and biological processes are often difficult to unravel, due to the wide variety of chemical species involved and interactions between different elemental cycles. A replicated mesocosm experiment was used to test the effect of increasing copper concentrations, i.e., from 6 mg kg‾¹ to 30 and 120 mg kg‾¹, on nitrogen cycling in a freshwater sediment under laboratory conditions. Nitrous oxide emissions from the treated sediments were measured over three consecutive 24 h periods. This was followed by measurements of iron, manganese, copper and mineral nitrogen species (nitrate and ammonium) mobilisation in the sediments using the diffusive gradients in thin films (DGT) and diffusive equilibria in thin films (DET) techniques and sequential extractions. Increasing copper concentrations are shown to have resulted in significantly reduced nitrate formation near the sediment–water interface and increased nitrous oxide emissions from the sediment overall. The concomitant mobilisation and sequestration of iron with ammonium in the sediment with the highest Cu treatment strongly imply links between the biogeochemical cycles of the two elements. Modest Cu contamination was shown to affect the nitrogen cycle in the tested freshwater sediment, which suggests that even relatively small loads of the metal in fresh watercourses can exert an influence on nutrient loads and greenhouse gas emissions from these environments

Extractable aluminium in New Zealand Andisols and Inceptisols

It is critical to have a soil test that allows for the measurement of potential toxicity. A laboratory experiment was undertaken to investigate the effects of changing the concentration of salt in the extract and extraction time of the standard CaCl₂ and KCl soil Al tests on the Al concentrations extracted from 13 soils from four New Zealand soil orders. Al extracted by KCl (AlKCl) was 13 times higher than extracted by CaCl₂ (AlCaCl2) across all soils. The effect of changing extract salt concentration and extraction time on Al extracted differed among the four soil orders tested for the two extraction methods. Increasing the concentration of CaCl₂ in the extract increased (P .05) the AlCaCl2 extracted from all soils. An increase in the concentration of KCl in the extract up to 1 M increased AlKCl (P .05) with a further increase in concentration. Extraction time affected AlKCl (P < .001) for Pallic soils, while the interaction of concentration of KCl in the extract and extraction time resulted in differences (P < .001) only for the Pallic soils. These findings suggest that the Al concentrations measured by the two extraction methods are affected by specific soil properties in the topsoil related to soil order. This means that when measuring the Al bioavailability in soils, extreme care must be taken when interpreting soil Al test results

The effect of contrasting biosolids application strategies on soil quality

Purpose: Incorporating biosolids into the soil improves plant yield compared with surface application, but it can result in the increased uptake of trace elements. However, there is a lack of knowledge about how different types of biosolids applications affect soil quality. We aimed to determine the effect of the type and rate of biosolids application on soil quality and the mobility of contaminants. Methods: Soil quality was determined by soil fertility (inorganic N, exchangeable P, Mg, Ca, K), exchangeable trace and non-essential elements (Al, Mn, Zn, Cu and Cd) and biological activity (dehydrogenase activity). We measured the properties of soil pore water, bulk soil and rhizosphere in a pot and a rhizobox experiment, with increasing concentration of biosolids (equiv. 16 t ha¯¹, 48 t ha¯¹ and 145 t ha¯¹ dry weight), applied on the surface, incorporated to 25 cm, or incorporated into a patch. Results and discussion: The incorporation of biosolids into the soil increased the exchangeable Zn, Cu, Cr, Ni and Cd, compared with surface application. The surface application of biosolids increased the inorganic N in the soil compared with biosolids incorporation (680 mg kg¯¹ vs. 380 mg kg¯¹), and decreased soil pH by 1.1 units. This aligned with solubilisation of Al (43 mg kg¯¹ vs. 6 mg kg¯¹) and Mn (43 mg kg¯¹ vs. 33 mg kg¯¹) and explains the decreased microbial activity in the soil compared with the unamended soil. Incorporating biosolids in the soil increased the biological activity, likely due to biosolids-borne microbes. The root systems significantly increased microbial activity, pH, and the concentration of NH₄⁺, NO₃⁻, and exchangeable P, S, Mg, Na, Zn, Cu and Ni, and significantly decreased exchangeable concentration of Mn and Fe

Temporal Changes in Cd Sorption and Plant Bioavailability in Compost-Amended Soils

The application of Cd-contaminated phosphate fertiliser has enriched concentrations of this non-essential element in many agricultural soils. Consequently, concentrations of the metal in some agricultural products exceed the Maximum Limit in foods. Composts can reduce the transfer of Cd from soil to plants; however, it is unclear how long this beneficial effect endures. We aimed to determine temporal changes of phytoavailable Cd in two market garden soils (an Allophanic Orthic Granular Soil and a Recent Silt Loam). Soils were amended with either municipal green waste compost or sawdust and animal waste compost at a rate of 2.5% w/w under three incubation regimes: at 19 °C, at 30 °C, and at 30 °C with additional N added as urea at 0.6 g urea/kg soil added over 1 year. Each replicate was sampled after 1, 5, 9, 13, 21, 31, and 49 weeks, and phytoavailable Cd was estimated through 0.05 M Ca(NO3)2 extraction. Seed potato (Solanum tuberosum), ‘Nadine’ variety, was grown in the Pukekohe Allophanic Orthic Granular Soil, freshly amended with municipal compost and the same soil aged for one year. The concentration of Cd in all samples was analysed using an ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer). The C concentration in the soil—compost mixtures decreased over the year, with the greatest decreases occurring in the soils incubated at 30 °C with added N. Unexpectedly, the concentration of Ca(NO3)2-extractable Cd in the compost-amended soils did not increase over time and in some cases even decreased. This was confirmed through a pot experiment, which showed the Cd concentration in potato was reduced by 50% in both the freshly amended soil and the amended soil aged for one year. Cadmium immobilisation in soils might be due to both the sorption of Cd by organic matter and the occlusion of sorbed Cd by oxy-hydroxides of iron and aluminium. Over 49 weeks, soluble Cd does not increase as organic matter oxidises. The application of municipal compost to soil will reduce both plant Cd solubility and plant Cd uptake for at least one year in the soils tested

Heavy metals in suburban gardens and the implications of land-use change following a major earthquake

Numerous studies have shown that urban soils can contain elevated concentrations of heavy metals (HMs). Christchurch, New Zealand, is a relatively young city (150 years old) with a population of 390,000. Most soils in Christchurch are sub-urban, with food production in residential gardens a popular activity. Earthquakes in 2010 and 2011 have resulted in the re-zoning of 630 ha of Christchurch, with suggestions that some of this land could be used for community gardens. We aimed to determine the HM concentrations in a selection of suburban gardens in Christchurch as well as in soils identified as being at risk of HM contamination due to hazardous former land uses or nearby activities. Heavy metal concentrations in suburban Christchurch garden soils were higher than normal background soil concentrations. Some 46% of the urban garden samples had Pb concentrations higher than the residential land use national standard of 210 mg kg⁻¹, with the most contaminated soil containing 2615 mg kg⁻¹ Pb. Concentrations of As and Zn exceeded the residential land use national standards (20 mg kg⁻¹ As and 400 mg kg⁻¹ Zn) in 20% of the soils. Older neighbourhoods had significantly higher soil HM concentrations than younger neighbourhoods. Neighbourhoods developed pre-1950s had a mean Pb concentration of 282 mg kg⁻¹ in their garden soils. Soil HM concentrations should be key criteria when determining the future land use of former residential areas that have been demolished because of the earthquakes in 2010 and 2011. Redeveloping these areas as parklands or forests would result in less human HM exposure than agriculture or community gardens where food is produced and bare soil is exposed

Evaluation of the diffusive gradients in thin-films (DGT) technique for measuring nitrate and ammonium in soil

Rationale. The availability of soil nitrogen for plant uptake can be affected by numerous soil factors such as soil texture, moisture and organic matter content, temperature and microbial activity. Conventional extraction techniques may affect the measurement of plant-available N concentrations following sampling and sample preparation processes, including drying, sieving, homogenising, freezing and thawing. The diffusive gradients in thin-films (DGT) technique can overcome some limitations of the conventional extraction techniques and has been used to successfully estimate the plant-available fractions of nutrients, such as P, K, Zn, Cu and Mn in soils. Therefore, it is important to evaluate the use of DGT for measuring NO₃- and NH₄⁺ in a wide variety of soils and examine the factors that contribute to the plant-availability of these ions in soils. Methodology. The experiment evaluated the ability of the DGT technique to measure NO₃-N and NH₄-N in soils using binding layers containing A520E anion exchange resin or Microlite® PrCH cation exchange resin, respectively. The DGT results were compared to those from conventional KCl extraction. Results. The A520E- and PrCH-DGTs showed good detection limits for NO₃-N (6.90 µg L−¹) and NH₄-N (6.23 µg L−¹) and were able to measure potentially available NO₃-N and NH₄-N in unfertilised soils. The mass of NO₃-N and NH₄-N that accumulated on the DGT device increased linearly across soil concentrations ranging from 5 to 300 mg kg−¹ NO₃-N (depending on soil type) and 5–300 mg kg−¹ NH₄-N; which is equivalent to fertiliser rates of 75–450 kg ha¯¹ N. DGTs were used to measure potentially available NO₃-N and NH₄-N in ten soils with various physical and chemical properties. The DGT results were compared with conventional KCl extraction used to determine soil mineral N. DGT and KCl extraction measured values were significantly correlated with each other for NO₃-N (R² = 0.53; P-value < 0.001), but the relationship between the two measurements was weaker for NH₄-N (R² = 0.20, P-value = 0.045). Discussion. The results suggest that the two methods sample different N pools in the soils, with DGT targeting the NO₃-N and NH₄-N that are available in soil pore water and attached to labile solid phases

Temperature effects on dislocation core energies in silicon and germanium

Temperature effects on the energetics of the 90-degree partial dislocation in silicon and germanium are investigated, using non-equilibrium methods to estimate free energies, coupled with Monte Carlo simulations. Atomic interactions are described by Tersoff and EDIP interatomic potentials. Our results indicate that the vibrational entropy has the effect of increasing the difference in free energy between the two possible reconstructions of the 90-degree partial, namely, the single-period and the double-period geometries. This effect further increases the energetic stability of the double-period reconstruction at high temperatures. The results also indicate that anharmonic effects may play an important role in determining the structural properties of these defects in the high-temperature regime.Comment: 8 pages in two-column physical-review format with six figure

Animal Welfare Attitudes: Effects of Gender and Diet in University Samples from 22 Countries

Animal Welfare Attitudes (AWA) are defined as human attitudes towards the welfare of animals in different dimensions and settings. Demographic factors, such as age and gender are associated with AWA. The aim of this study was to assess gender differences among university students in a large convenience sample from twenty-two nations in AWA. A total of 7914 people participated in the study (5155 women, 2711 men, 48 diverse). Participants completed a questionnaire that collected demographic data, typical diet and responses to the Composite Respect for Animals Scale Short version (CRAS-S). In addition, we used a measure of gender empowerment from the Human Development Report. The largest variance in AWA was explained by diet, followed by country and gender. In terms of diet, 6385 participants reported to be omnivores, 296 as pescatarian, 637 ate a vegetarian diet and 434 were vegans (n = 162 without answer). Diet was related with CRAS-S scores; people with a vegan diet scored higher in AWA than omnivores. Women scored significantly higher on AWA than men. Furthermore, gender differences in AWA increased as gender inequality decreased

Diffusive gradients in thin-films (DGT) in soil science research: Review of the last 25 years

The diffusive gradients in thin-films (DGT) technique was originally developed for use in natural waters to measure the elusive “free” trace metal ion. It was quickly adapted for use in aquatic sediments and soils to measure trace metal and phosphorus fluxes, and the first scientific article reporting its use in soils was submitted for publication 25 years ago. The technique showed early promise as a reliable measurement of plant available trace metal in soils and it was first used for that purpose on Aotearoa soils in the late 2000s. It has since been adapted to measure a variety of different analytes, in expanded dimensionality and simultaneously with measurements of other dynamic soil variables (e.g. pH, enzyme activity). The insight gained in the last quarter of a century of DGT research will be used to re-examine some of the early assumptions about the information it can provide. The presentation will go on to highlight some new and interesting applications for both applied and theoretical soil scientists in Aotearoa. There are clearly important challenges to understanding what the results of DGT measurements in some soils represent. However, increased knowledge of processes that influence the supply of nutrients and trace elements to DGT presents new opportunities to investigate biogeochemical cycling in soils in ways that are not possible with most other techniques. This provides interesting prospects for future soil research where the technique can play a unique and important role

Effects of age on marathon finishing time among male amateur runners in Stockholm Marathon 1979–2014

Purpose: The purpose of the present study was to investigate the age-related changes in the endurance performance among male amateur marathon runners. Methods: Subjects were taken from the 36 Stockholm Marathons held from 1979 through 2014, and age and finishing time were analyzed for a total of 312,342 male runners. Results: The relation was found to be a second-order polynomial, t = a + bx + cx2, which models 99.7% of the variation in the average running time t as a function of age x. The model shows that the marathon performance of the average runner improves up to age 34.3 ± 2.6 years, thereafter, the performance starts to decline. A quantification of the age's influence on running time shows that it accounts for 4.5% of the total variance seen in the performance data. Conclusion: These outcomes indicate that the effect of age on performance in endurance running events is clearly measurable, quantifiable, and possible to describe. At the same time the findings indicate that other factors, such as training, affect the performance more. A comparison with the elite showed peak performance at the same age, but the rates of change in performance with age, improvement as well as degradation, was found to be higher among the elite