The effect of oxidation and acidification on the speciation of heavy metals in sulfide-rich freshwater sediments using a sequential extraction procedure

The speciation of metals in a contaminated, anoxic, sulfide-rich, freshwater sediment was determined experimentally, using a sequential extraction procedure based on the method of Tessier et al. Taking into account the advantages and disadvantages of sequential extractions, the applied methodology allowed the investigation of the influence of aeration and acidification on the distribution of various metals in the sediment. Aeration caused Zn and Cd to be released from sulfides. Carbonates were partly dissolved by the oxidation process, causing mobilisation of Ca. Fe became less mobile owing to a stronger binding to organic matter. The speciation of K, Al, Ni, Pb and Mn and to a lesser extent of Cu was not affected by aeration. As a result of acidification of the aerated sediment, Ca, Mn, Ni, Zn and Cd became more mobile owing to the dissolution of carbonates.     

Comparison of four measuring techniques to assess growth inhibition in standardized tests with seven freshwater algae and cyanobacteria

As representatives of primary producers, algae and cyanobacteria play an important role in assessing the risk of chemicals. However, the list of standard algal species commonly used for toxicity testing comprises very few species so that there is an urgent demand to identify further non-standard species which can be used for higher-tier risk assessment in general and the analysis of species sensitivity distributions in particular. In this study, four measuring techniques to assess growth inhibition were compared using five non-standard and two standard algal species and 3,5-dichlorophenol as reference substance. Regarding sensitivity and suitability, the measuring techniques were ranked in the following descending order: delayed fluorescence, prompt fluorescence, photometric absorbance, and microscopic cell count. All five non-standard species fulfilled the validity criteria if tested with delayed fluorescence.     

Dissolution kinetics of heavy metals in Dutch carbonate- and sulfide-rich freshwater sediments

In two sulfide-rich freshwater sediments from the Biesbosch and Kromme Rijn River in the Netherlands differing in carbonate content and acid volatile sulfide (AVS) content, metal and sulfide dissolution kinetics were studied at different acid concentrations by varying both the procedure of acid addition and the extraction time. The establishment of equilibrium was monitored by measuring the pH in time, which reached a near constant value. The equilibrium pH was reached quickly when large amounts of acid were added and slowly when small amounts of acid were added. This observation was confirmed by the yield of extracted metals after either a 45-min or 24-h extraction over a pH range from 0 to 5. The pH factor seemed to be of more influence than time for the dissolution of metals. The amount of extracted metals was highly dependent on the metal itself due to its physico-chemical behavior. Although the sediments studied varied in carbonate content, acid volatile sulfide (AVS), and total metal content, the extracted fraction of metals compared with their total content in the sediment was similar for most metals. Finally, the AVS content as well as the ratio of simultaneously extracted metals (SEM; sum of Cd, Cu, Ni, Pb, and Zn) to AVS decreased with increasing pH. Because the SEM to AVS ratio may be used to set environmental quality criteria for the sediment compartment, this observation is of significance.     

Reluctant pioneers in the European periphery? Environmental activism,food consumption and “growing your own”

East European food self-provisioning (FSP) has fascinated scholars of post-socialism ever since the early 1990s. In keeping with its predominantly economic and cultural conceptualisations, much of this research has been concerned with FSP’s role in household economy and with the social profile of its practitioners. In contrast to western conceptualisations of FSP as an opportunity to expand food activism and foster social justice and environmental sustainability, post-socialist FSP has rarely been considered as such. In Czechia, FSP is practised by 43% of citizens and many of them do so in a relatively environmentally friendly way. Yet, most food-related campaigns run by environmental NGOs (ENGOs) pay little attention to FSP and focus on market-based ethical consumerism and alternative food networks instead. Using insights from actor-network theory, this paper discusses how Czech ENGO activists engage with FSP through discourse and in practice. Based on ethnographic fieldwork and interviews with leading activists, we show that FSP does figure in non-food-related campaigns and that the FSP practised by activists themselves or the FSP carried out by relatives and relatives’ friends are not the same as the FSP on which they are reluctant to campaign. These differences, which include controllability and the time-consuming nature of practising FSP according to some of the activists’ ideals, help this paper to come to an initial understanding of why Czech ENGOs do not run campaigns explicitly focused on FSP at the moment and shed some light on how this could change in the future.     

Spatial and temporal variations in NO2 distributions over Beijing,China measured by imaging differential optical absorption spectroscopy

During the CAREBEIJING campaign in 2006, imaging differential optical absorption spectroscopy (I-DOAS) measurements were made from 08:00 to 16:00 on September 9 and 10 over Beijing, China. Detailed images of the near-surface NO₂ differential slant column density (DSCD) distribution over Beijing were obtained. Images with less than a 30-min temporal resolution showed both horizontal and vertical variations in NO₂ distributions. For DSCD to mixing ratio conversion, path length along the lines of I-DOAS lines of sight was estimated using the light-extinction coefficient and Ångstrom exponent data obtained by a transmissometer and a sunphotometer, respectively. Mixing ratios measured by an in-situ NO₂ analyzer were compared with those estimated by the I-DOAS instrument. The obtained temporal and spatial variations in NO₂ distributions measured by I-DOAS for the two days are interpreted with consideration of the locations of the major NO_x sources and local wind conditions. I-DOAS measurements have been applied in this study for estimating NO₂ distribution over an urban area with multiple and distributed emission sources. Results are obtained for estimated temporal and spatial NO₂ distributions over the urban atmosphere; demonstrating the capability of the I-DOAS technique. We discuss in this paper the use of I-DOAS measurements to estimate the NO₂ distribution over an urban area with multiple distributed emission sources.     

Insuring against earthquakes: simulating the cost‐effectiveness of disaster preparedness

Ex‐ante measures to improve risk preparedness for natural disasters are generally considered to be more effective than ex‐post measures. Nevertheless, most resources are allocated after an event in geographical areas that are vulnerable to natural disasters. This paper analyses the cost‐effectiveness of ex‐ante adaptation measures in the wake of earthquakes and provides an assessment of the future role of private and public agencies in disaster risk management. The study uses a simulation model approach to evaluate consumption losses after earthquakes under different scenarios of intervention. Particular attention is given to the role of activity diversification measures in enhancing disaster preparedness and the contributions of (targeted) microcredit and education programmes for reconstruction following a disaster. Whereas the former measures are far more cost‐effective, missing markets and perverse incentives tend to make ex‐post measures a preferred option, thus occasioning underinvestment in ex‐ante adaptation initiatives.     

Investigation on downwind short-range transport of pesticides after application in agricultural crops

For the assessment of potential risks from total exposure to both spray drift and volatilised pesticides, field experiments in barley were carried out with insecticide application in May and June 2000. Pesticide concentrations in the air at the edge of the treated plot and at various distances in downwind direction were determined. The concentrations at 10 m distance were 0.29 and 0.58 microg/m(3) (lindane), 0.07 and 0.12 microg/m(3) (parathion) or <0.02 and 0.04 microg/m(3) (pirimicarb) after 1 d. To quantify the exposure of aquatic ecosystems, water containers simulating surface waters were placed in downwind direction of the plot at distances of 10 and 50 m. Lindane as the most volatile and most persistent of the investigated active substances showed the highest entries in surface water with 35 and 153 microg/m(2) after 1 d at a distance of 10 m, attributable to a larger extent to deposition of volatilised compound than to spray drift when drift reducing nozzles were used. Similar results were obtained for parathion, but at a lower level. Mainly due to its photolytic instability in water, pirimicarb decayed in surface water, where a maximum deposition was measured 2 h after application.     

Simultaneous extraction of bromide, chloride, fluoride and sulfate from soils, waste- and building materials

The simultaneous extraction of bromide, chloride, fluoride and sulfate was studied in soils, waste- and building materials. Acid, neutral and alkaline extractants were used; 0.01 mol l(-1) H(3)PO(4), milliQ-water and 0.01 mol l(-1) NaOH, respectively. The extracts were analysed by ion chromatography and ion selective electrode. Extracted concentrations were compared with the amount obtained by an alkaline smelt, as an approximation of the total extractable content. The results indicate that there is a significant difference in extraction behaviour between waste- and building materials and soils. Bromide and chloride were in general completely extracted from the former solid materials, but less than 10% and 50%, respectively, from soils. Fluoride is strongly bound in all investigated samples; less than 10% of the total content was extracted with any of the three extractants. The fraction of extracted sulfate varied between 4 and 87% of the total content, and was in general larger in waste- and building materials than in soils. Differences in extracted concentration between the 3 extractants occurred mainly for fluoride and sulfate. Extracted bromide was similar with all three extractants and extracted chloride showed differences for the various soil samples only. Increasing the NaOH concentration up to 1 mol l(-1) resulted mainly in an increase of extracted amount of fluoride and for soils also in extracted amounts of bromide and sulfate. Although, the results show that the composition of the solid material strongly influences the final pH of the extract and the extracted amount of investigated anions, application of Milli-Q water as an extractant might be a very fruitful option within the development of the Dutch Building Materials Decree.     

Enzymatic pattern processing

 A table-top prototype has been constructed that uses the enzyme malate dehydrogenase to recognize input signal patterns. The device is controlled by the enzyme in response to injection of Mg²⁺ used as a signaling substance. Output is monitored spectroscopically. If Mg²⁺ is injected along either of two signal lines (i.e., if the input signal pattern is 10 or 01) the device emits an output of 1. Injection along neither or both lines results in an output of 0. The enzyme in effect is used as a transform that converts the linearly inseparable exclusive-or problem into a linearly separable problem. Received: 3 April 2000 / Accepted in revised form: 16 June 2000