Extractable soil heavy metals following the cessation of biosolids application to agricultural soil

Changes in soil heavy metal extractability following the cessation of biosolids applications were studied in a long-term field experiment. Two anaerobically digested biosolids from wastewater treatment plants in Madrid (Sur and Viveros) were applied to cropland from 1983 to 1990. Soil samples were collected in the 1st, 5th and 9th year after the last biosolids application. Soil pH did not vary significantly after biosolids applications. Organic matter and total heavy metals (Zn, Pb, Cd, Ni, Cr and Cu) concentrations initially increased but then declined over time, mostly after the first 5 years following biosolids application. Metal extracted with DPTA increased in Sur treatments during the 1st year and diminished thereafter. However, in Viveros treatments, heavy metals extracted increased during the 1st year, declined in 1995, and showed a slight increase in 1999. These changes in heavy metal extractability were widely observed in the percentage of extractable metal recovery (EMR). The differences observed in the pattern of the two sources of biosolids applied could be due to the different rates of decomposition of their organic matter.     

Bioavailability of diuron,imazapic and isoxaflutole in soils of contrasting textures

This research was aimed at understanding the dynamics of the herbicides diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], imazapic [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-5-methylnicotinic acid] and isoxaflutole [5-cyclopropyl-4-(2-methanesulfonyl-4-trifluoromethyl benzoyl)isoxazole] in two soils of different physico-chemical properties. To accomplish such intent, several greenhouse experiments were run. The bioavailability of diuron (0; 1.6 and 3.2 kg ha^{? 1}), imazapic (0; 98 and 122.5 g ha^{? 1}) and isoxaflutole (0; 35 and 70 g ha^{? 1}) was measured in samples from a sandy loam soil and a clay soil, by sowing a bioindicator (Brachiaria decumbens), at 0, 25, 50, 75 and 100 days after herbicides application (DAA). Diuron was very stable in clay soil, providing control equal to or higher than 92% of bioindicator, up to 100 DAA, as assumed by biomass accumulation. No differential effect was observed in sandy loam soil, even when 2x labeled rate were applied. Imazapic provided a short bioavailability in relation to B. decumbens, independent of rates applied. The persistence of isoxaflutole was longer in clay soil (28 to 30 days).     

The freshwater planarian Polycelis felina as a sensitive species to assess the long-term toxicity of ammonia

Behavioural endpoints are a good link between physiological and ecological effects. However long-term behavioural endpoints are not uniformly studied over all different organism groups. For example behaviour has been scarcely studied in planarians. Unionized ammonia (NH₃) is one of the most widespread pollutants in developed countries, and is known to alter animal behaviour. In this study a long-term (30 d) bioassay was conducted to assess the effect of this pollutant on survival and behavioural activity (e.g. locomotion activity) of the freshwater planarian Polycelis felina. One control and three environmentally-realistic concentrations of unionized ammonia (treatments of 0.02, 0.05, and 0.09 mg N-NH₃ L⁻¹) were used in quintuplicate. The behaviour of planarians was measured after 0, 10, 20 and 30 d of ammonia exposure. Mortality was recorded every 2 d. Unionized ammonia increased mortality in the two highest NH₃ concentrations and the locomotory activity was depressed in all treatments after 20 d of exposure. Behavioural effect was observed at concentrations 20 times lower than the short-term LC50 for this species. Previous studies proposed safe concentrations of unionized ammonia of 0.01-0.10 mg N-NH₃ L⁻¹ to aquatic ecosystems, but our study has shown that these concentrations will affect planarians. Because planarians play a key role in streams (as predator/scavenger), safe concentrations should be below 0.02 mg N-NH₃ L⁻¹ to protect this species in the freshwater community. Our results can contribute to improve the knowledge about ammonia toxicity to freshwater ecosystems, we recommend that safe concentrations of unionized ammonia should be based on very sensitive species.     

Sequential extraction of metals from mixed and digested sludge from aerobic WWTPs sited in the south of Spain

The content of heavy metals is the major limitation to the application of sewage sludge in soil. However, assessment of the pollution by total metal determination does not reveal the true environmental impact. It is necessary to apply sequential extraction techniques to obtain suitable information about their bioavailability or toxicity. In this paper, sequential extraction of metals from sludge before and after aerobic digestion was applied to sludge from five WWTPs in southern Spain to obtain information about the influence of the digestion treatment in the concentration of the metals. The percentage of each metal as residual, oxidizable, reducible and exchangeable form was calculated. For this purpose, sludge samples were collected from two different points of the plants, namely, sludge from the mixture (primary and secondary sludge) tank (mixed sludge, MS) and the digested-dewatered sludge (final sludge, FS). Heavy metals, Al, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Ti and Zn, were extracted following the sequential extraction scheme proposed by the Standards, Measurements and Testing Programme of the European Commission and determined by inductively-coupled plasma atomic emission spectrometry. The total concentration of heavy metals in the measured sludge samples did not exceed the limits set out by European legislation and were mainly associated with the two less-available fractions (27-28% as oxidizable metal and 44-50% as residual metal). However, metals as Co (64% in MS and 52% in FS samples), Mn (82% in MS and 79% in FS), Ni (32% in MS and 26% in FS) and Zn (79% in MS and 62% in FS) were present at important percentages as available forms. In addition, results showed a clear increase of the concentration of metals after sludge treatment in the proportion of two less-available fractions (oxidizable and residual metal).     

Simulation of stomatal conductance for Aleppo pine to estimate its ozone uptake

The data from a previous experiment carried out in open-top chambers to assess the effects of ozone (O3) exposure on growth and physiology of Aleppo pine (Pinus halepensis Mill.) were re-assessed to test the performance of the EMEP O3 stomatal conductance model used to estimate tree O3 uptake at a European scale. Aleppo pine seedlings were exposed during three consecutive years to three different O3 treatments: charcoal filtered air, non-filtered air and non-filtered air supplemented with 40 nl l(-1). The results of the model using the default parameterisation already published for Mediterranean conifers showed a poor performance when compared to measured data. Therefore, modifications of g(max), f(min), and new f(VPD), f(temp) and f(phen) functions were developed according to the observed data. This re-parameterisation resulted in a significant improvement of the performance of the model when compared to its original version.     

Effectiveness of three configurations of membrane bioreactors on the removal of priority and emergent organic compounds from wastewater: comparison with conventional wastewater treatments

In this work the effectiveness of membrane bioreactors as advanced treatment on the removal of emergent and priority organic compounds in wastewater treatment plants has been evaluated during a one-year monitoring study. The studied wastewater treatment plant operates with flat sheet and hollow fibre membranes in two parallel lines. Moreover, a reverse osmosis module connected in series after the hollow fibre membrane was evaluated for one month. Comparison of membrane bioreactor and conventional activated sludge treatment was also investigated, as well as the influence of the physicochemical properties of the compounds on the removal rates achieved. Sixteen pharmaceutical compounds belonging to seven therapeutic groups and eight priority organic pollutants, including linear alkylbenzene sulfonates, nonylphenol and its ethoxylates and phthalate, were monitored. The highest mean concentrations corresponded to priority organic pollutants (309 μg L(-1) of linear alkylbenzene sulfonate C(12)) followed by pharmaceutical compounds (24.5 μg L(-1) of ibuprofen). No significant difference of effectiveness was found among flat sheet and hollow fibre membranes. However, an improvement was obtained with the addition of a reverse osmosis module for most of the compounds. Biodegradation has been shown as the main route involved in the removal of organic compounds during both technologies.     

Ecosystem service provision,management systems and climate change in Valsaín forest,central Spain

This study addresses the impact of climate change and management approach on the provision of four ecosystem services (ES) (timber production, protection against gravitational hazards, carbon sequestration and biodiversity) in Valsaín forest in central Spain. The hybrid forest patch model PICUS v1.6 was used to simulate the development of 24 representative stand types over 100 years (2010–2110) in a full factorial simulation experiment combining three management regimes [“business as usual” management (BAU) and two alternatives to BAU (AM1 and AM2)], a no-management scenario (NOM) and six climate scenarios (historic climate represented by the period 1961–1990 and five transient climate change scenarios). Simulations indicated relatively small differences as regards the impact of the different management alternatives (BAU, AM1 and AM2) on the provision of ES as well as a clear improvement in biodiversity, protection and carbon storage under the no-management regime (NOM). Although timber production indicators were the most sensitive to climate change scenarios, biodiversity-related indicators responded fastest to the management regimes applied. Indicators of protection against rockfall and landslides were affected by both management and climate change. The results indicate substantial vulnerability of ES provisioning under the more extreme climate change scenarios at low elevations (1250 m). At higher elevations, the productivity of Scots pine stands may show a moderate decrease or increase, depending on the climate change scenario.     

Identifying the potential of governance regimes to aggravate or mitigate local water conflicts in regions threatened by climate change

There is a need for specific knowledge of what people can do to mitigate harmful water conflicts. This need is evident in the rural dry tropics of Central America where people face climate change impacts, inefficient water management, and social tension. To address this need, we investigated why some local water conflicts escalated to violence and why other potential conflicts were avoided in Guanacaste Province, Costa Rica. We used interviews, focus groups, and a stakeholder workshop to analyse five cases. We found that violent actions only occurred when rural groups opposed government agencies in settings without mediating leadership. With one exception in a circumstance aggravated over many years, water users did not take violent action against competing water users. Distrust, which has been formed by legacies of ineffective rural stakeholder engagement, diminished the credibility of water-related information used in decision processes and thus prolonged conflicts. Active community-based groups respected by both rural constituencies and government agencies helped some people avoid difficult conflicts. Self-organised groups in other areas struggled to address disputes in settings with contested property rights, high socio-economic inequality, and low human capital. Using insights from Guanacaste, we outline practical conflict mitigation strategies fitted to a range of local water governance contexts found in rural Central America. Results suggest the need for incorporating certain types of peace-building processes in water management and development. The study provides a foundation for policy-makers, water managers, and other stakeholders to more effectively manage water disputes and avoid harmful conflicts in challenging regions.