Significance of metal exchange in EDDS-flushing column experiments

Chelating agents have been widely studied for extracting heavy metals from contaminated soils, and the effectiveness of EDDS ([S,S]-ethylene-diamine-disuccinic acid) has aroused extensive attention because of its biodegradability in the natural environment. However, in the course of EDDS-flushing, metal exchange of newly extracted metal-EDDS complexes with other sorbed metals and mineral cations may result in metal re-adsorption on the soil surfaces. Therefore, this study investigated the relative significance of metal exchange under different travel distances of chelant complexes, characteristics of soil contamination, and solution pH in the column experiments. As a result of metal exchange, the elution of Zn and Pb was retarded and the cumulative extraction was lower than those of Ni and Cu, especially over a longer travel distance. Compared with the field-contaminated soils, the effects of metal exchange were even more substantial in the artificially contaminated soil because of a greater amount of extractable metals and a larger proportion of weakly bound fractions. By contrast, metal exchange was insignificant at pH 8, probably due to less adsorption of metal-EDDS complexes. These findings highlight the conditions under which metal exchange of metal-EDDS complexes and the resulting impacts are more significant during EDDS-flushing.     

Zero-valent iron and iron oxide-coated sand as a combination for removal of co-present chromate and arsenate from groundwater with humic acid

The combination of zero-valent iron (Fe⁰) and iron oxide-coated sand (IOCS) was used to remove Cr(VI) and As(V) from groundwater in this study. The efficiency and the removal mechanism of Cr(VI) and As(V) by using this combination, with the influence of humic acid (HA), were investigated using batch experiments. Results showed that, compared to using Fe⁰ or IOCS alone, the Fe⁰-IOCS can perform better on the removal of both Cr(VI) and As(V). Metal extraction studies showed that As(V) was mainly removed by IOCS and iron corrosion products while Cr(VI) was mainly removed by Fe⁰ and its corrosion products. Competition was found between Cr(VI) and As(V) for the adsorption sites on the iron corrosion products. HA had shown insignificant effects on Cr(VI) removal but some effects on As(V) removal kinetics. As(V) was adsorbed on IOCS at the earlier stage, but adsorbed/coprecipitated with the iron corrosion products at the later stage.     

Public Discourses of Climate Change in Hong Kong

The changing political environment in Hong Kong is likely to accelerate the transition in environmental policy discourse. Opportunities for critical public involvement are increasing and new environmental discourses are emerging. Yet, previous social surveys did not explore the range of these discourses and few focused on climate change. The paper outlines the public discourses of climate change in Hong Kong. Using Q-methodology, four distinctive discourses were identified, namely Pure Environmentalism, Political Pragmatism, Popular Optimism, and Fair Rationalism. While the first one is climate-centric, the other three are political or social in nature and do not indicate a clear or coherent climate orientation. This suggests that the climate change concern of the Hong Kong public is not tightly embedded into a coherent narrative of social and institutional transformation. Effective climate change governance and policies require strengthening the link between such concern and the public desires for social and institutional transformation. Bringing together the ongoing social movements and environmental campaigns will be instrumental to nurture an active climate citizenry.     

Influence of salinity and temperature on the activity of biosurfactants by polychaete-associated isolates

Influence of different parameters on biosurfactant (BS) activity was carried out on strains that were isolated from the polychaetes Megalomma claparedei, Sabella spallanzanii and Branchiomma luctuosum and additional 30 strains that were previously identified as potential BS producers from crude oil enrichments of the same polychaete specimens. The selection of BS-producing strains from polychaete natural samples was carried out by using standard screening tests. The BS activity by each isolate was evaluated for the effect of salinity and temperature on emulsion production and surface tension reduction, during incubation in mineral medium supplemented with tetradecane or diesel oil. All isolates showed a similar time course of BS activity, and the latter was more influenced by salinity rather than temperature. Some of the BS producers belonged to genera that have not (i.e. Citricoccus, Cellulophaga, Tenacibaculum and Maribacter) or have poorly been (Psychrobacter, Vibrio, and Pseudoalteromonas) reported as able to produce BSs. This is remarkable as some of them have previously been detected in hydrocarbon-enriched samples. Results confirm that filter-feeding polychaetes are an efficient source for the isolation of BS producers.     

Science–policy processes for transboundary water governance

In this policy perspective, we outline several conditions to support effective science–policy interaction, with a particular emphasis on improving water governance in transboundary basins. Key conditions include (1) recognizing that science is a crucial but bounded input into water resource decision-making processes; (2) establishing conditions for collaboration and shared commitment among actors; (3) understanding that social or group-learning processes linked to science–policy interaction are enhanced through greater collaboration; (4) accepting that the collaborative production of knowledge about hydrological issues and associated socioeconomic change and institutional responses is essential to build legitimate decision-making processes; and (5) engaging boundary organizations and informal networks of scientists, policy makers, and civil society. We elaborate on these conditions with a diverse set of international examples drawn from a synthesis of our collective experiences in assessing the opportunities and constraints (including the role of power relations) related to governance for water in transboundary settings.     

Autochthonous clams monitoring of Ganzirri Lake (Sicily)

Two autochthonous clams, Venerupis aurea laeta and Cerastoderma edule/glaucum, collected for a period of 1 year, from May 2007 to January 2008, were studied in the Cape Peloro lagoon. On the samples, it was evaluated the presence of pathogenic microorganisms and proteins, lipids and yield edible part were determined. It was evaluated the concentration of mineral elements (Cd, Cu, Mn, Se, Pb, Zn) and organic contaminants (∑DDT and PCBs). Salmonella is never present in any sample. Total and faecal coliform values have always been under law limits for alive bivalves mussels production and sale. Zn, Cu, Cd and Pb levels were found in clams where they are slightly lower too. Both species do not show significant changes for Mn and Se. DDT and PCBs traces were discovered in Ganzirri Lake’ samples, but in all observed cases, they were below law limits. As a result of all these observations, it is clear that, in recent years, the bivalve’s use of Ganzirri Lake does not denote toxicological risk to human health.     

Environmental water demand assessment under climate change conditions

Measures taken to cope with the possible effects of climate change on water resources management are key for the successful adaptation to such change. This work assesses the environmental water demand of the Karkheh river in the reach comprising Karkheh dam to the Hoor-al-Azim wetland, Iran, under climate change during the period 2010–2059. The assessment of the environmental demand applies (1) representative concentration pathways (RCPs) and (2) downscaling methods. The first phase of this work projects temperature and rainfall in the period 2010–2059 under three RCPs and with two downscaling methods. Thus, six climatic scenarios are generated. The results showed that temperature and rainfall average would increase in the range of 1.7–5.2 and 1.9–9.2%, respectively. Subsequently, flows corresponding to the six different climatic scenarios are simulated with the unit hydrographs and component flows from rainfall, evaporation, and stream flow data (IHACRES) rainfall-runoff model and are input to the Karkheh reservoir. The simulation results indicated increases of 0.9–7.7% in the average flow under the six simulation scenarios during the period of analysis. The second phase of this paper’s methodology determines the monthly minimum environmental water demands of the Karkheh river associated with the six simulation scenarios using a hydrological method. The determined environmental demands are compared with historical ones. The results show that the temporal variation of monthly environmental demand would change under climate change conditions. Furthermore, some climatic scenarios project environmental water demand larger than and some of them project less than the baseline one.     

Microwave treatment and struvite recovery potential of dairy manure

Microwave digestion of liquid dairy manure was tested for the release of nutrients, such as orthophosphates, ammonia-nitrogen, magnesium, calcium and potassium, both with and without the aid of an oxidizing agent (hydrogen peroxide). The orthophosphate to total phosphorus ratio of the manure increased from 21% to greater than 80% with 5 minutes of microwave treatment. More than 36% of total chemical oxygen demand (t-COD) of the manure was reduced when microwave digestion was assisted with peroxide addition. In addition, the volatile fatty acids (VFAs) distribution shifted to simpler chain acids (acetic acid in particular) with an increase in operating temperature. In the second part of the study, digested manure with increased soluble phosphate was tested for the recovery of struvite (magnesium ammonium phosphate) at different pH. It was found that up to 90% of orthophosphate can be removed from the solution. Overall, it was concluded that the oxidizing agent-assisted microwave digestion process can be used upstream of anaerobic digestion, following which the anaerobically digested manure can be used for struvite recovery. Thus, this microwave digestion process presents the potential for enhanced efficiencies in both manure digestion and struvite recovery.     

Speciation of inorganic arsenic in coastal seawater from Ionian and Tyrrhenian Seas (Sicily, Italy) using derivative anodic stripping chronopotentiometry

The purpose of this paper was to use derivative anodic stripping chronopotentiometry (dASCP) as a sensitive and accurate technique, to determine the concentrations of dissolved As (III) and As (V) in coastal seawater samples from the Straits of Messina, the Ionian and the Tyrrhenian seas, and to investigate the relationship between the anthropogenic activities on the coastal areas and the concentration of dissolved inorganic arsenic in seawaters. The obtained data indicated that As (V) was the most abundant species, with concentration ranging from 26.7 to 307 nM, whereas As (III) levels were lower than 48 nM in all the samples. In particular, As (III) and As (V) levels significantly decreased from high to low anthropogenic activities zones (p < 0.00001, ANOVA), with the reference samples, from a wildlife reserve, showing the lowest values. Furthermore it was observed that human activities influenced inorganic arsenic speciation, since the zones that received high human input presented the highest As(V)/As (III) ratio.     

Optimal strategies for best management practice placement in a synthetic watershed

It is significant to arrange suitable design and placement of best management practices (BMPs) for reaching the aim that can not only satisfy environmental quality standards, but also decrease the total cost of BMPs. This study applied WinVAST model to predict watershed responses. The objective of this work was to discuss both the economic costs and benefits of BMPs and the control efficiency of discharge and pollutant exports, and to create some suitable standards for the optimal BMPs placement strategies. It is significant to find an optimal number and location of BMPs. In the case study herein, the number of BMPs including a detention pond and a grassy swale would be better to be given by four. The number of BMPs should also be determined by the environmental standards. Moreover, the result shows that the optimal location of BMPs placement is in the downstream area near the outlet and on the mainstream of the catchment. When the BMPs are set in these regions, it cannot only reduce the peak flow and peak pollutant exports, but also have slow time to peak watershed responses.