Metal availability and soil toxicity after repeated croppings of Thlaspi caerulescens in metal contaminated soils

Metal phytoextraction with hyperaccumulating plants could be a useful method to decontaminate soils, but it is not fully validated yet. In order to quantify the efficiency of Cd and Zn extraction from a calcareous soil with and without Fe amendment and an acidic soil, we performed a pot experiment with three successive croppings of Thlaspi caerulescens followed by 3 months without plant and 7 weeks with lettuce. We used a combined approach to assess total extraction efficiency (2 M HNO3-extractable metals), changes in metal bio/availability (0.1 M NaNO3-extractable metals and lettuce uptake) and toxicity (lettuce biomass and the BIOMET biosensor). The soil solution was monitored over the whole experiment. In the calcareous soil large Cu concentrations were probably responsible for chlorosis symptoms observed on T. caerulescens. When this soil was treated with Fe, the amount of extracted metal by T. caerulescens increased and metal availability and soil toxicity decreased when compared to the untreated soil. In the acidic soil, T. caerulescens was most efficient: Cd and Zn concentrations in plants were in the range of hyperaccumulation and HNO3-extractable Cd and Zn, metal bio/availability, soil toxicity, and Cd and Zn concentrations in the soil solution decreased significantly. However, a reduced Cd concentration measured in the third T. caerulescens cropping indicated a decrease in metal availability below a critical threshold, whereas the increase of dissolved Cd and Zn concentrations after the third cropping may be the early sign of soil re-equilibration. This indicates that phytoextraction efficiency must be assessed by different approaches in order not to overlook any potential hazard and that an efficient phytoextraction scheme will have to take into account the different dynamics of the soil-plant system.     

Determination of growth rate and yield of nitrifying bacteria by measuring carbon dioxide uptake rate.

Nitrifier growth parameters--the maximum growth rate (microAmax) and yield (YA)--were estimated by measuring the rate of carbon dioxide uptake and additional rates of oxygen uptake and ammonia (or nitrite) use. Batch tests in a combined titrimetric and offgas analyzer with enriched Nitrobacter and Nitrosomonas cultures and an activated sludge sample were performed. The measured microAmax values for the Nitrobacter and Nitrosomonas cultures were 0.67 +/- 0.03 day(-1) and 0.54 +/- 0.09 day(-1), while the YA values were 0.072 +/- 0.01 g volatile suspended solids (VSS) x g nitrogen (N)(-1) and 0.14 +/- 0.02 gVSS x gN(-1), respectively. For the activated sludge sample, microAmax was observed to increase with pH (microAmax = 0.72 x 3.3(pH-7.1)) over the range 6.8 to 7.1. All microAmax and YA values determined by this method were similar to those previously reported. Compared with other microAmax and YA estimation methods, this method allows for unique microAmax and YA estimations for given conditions from a single experiment.     

Decreased acid deposition and the chemical recovery of Killarney,Ontario, lakes

Lakes in Killarney Park near Sudbury, Ontario, Canada, have shown dramatic water quality changes including general increases in pH and alkalinity, and decreases in SO4(2-), base cations and metals. While some lakes have recovered to pH > 6.0, many are still highly acidic despite decades of improvement. Very high historical S deposition related to emissions from the Sudbury metal smelters dominated the acidification process in this region. However, since the implementation of substantial S emission controls (90%) at the smelters, the Sudbury emissions are no longer the major source of S deposition in the Sudbury area. Wet deposition of SO4(2-) and SO4(2-) concentrations in lakewaters at Killarney now approach values in the Dorset, Ontario, area, about 200 km from Sudbury. This suggests that the S deposition to the Killarney area is now primarily from long-range transport, not from local sources. Studies of Killarney lakes are revealing the complex nature of the chemical recovery process. As lake acidity decreases, other changes including decreased Ca2+ concentrations, increased transparency, and altered thermal regimes may potentially affect some of these ecosystems. It is clear that continuing assessments of the recovery of Killarney lakes, within a multiple-stressor framework, are needed.     

Quantitative Determination of Gaseous Nitrogen Dioxide Concentrations over Long Path Lengths by Selective Absorption of Argon Ion Laser Emission

An argon ion laser emits several laser lines In the visible region of the optical spectrum. The absorption coefficients of N0₂ at these laser emissions were measured in a multiple pass absorption cell. A differential technique, in which the ratio of the transmitted intensities of the argon laser emissions is measured, is described to determine the concentration of N0₂ in a polluted atmosphere over path lengths of several kilometers. Measurement of ratios eliminates interferences from particle scattering and thermal index gradients. Evaluation of the data taken in the 48 meter multipass cell indicates that concentrations of N0₂ less than one part per million could be determined in a 1 km optical path.     

The impact of invasive aquatic plants on ecosystem services and human well-being in Wular Lake,India

Regional Environmental Change - Alien invasive species cause significant impacts on ecosystems and economies, but the impacts on human well-being and livelihoods are less well known. Negative...     

A new gas chromatographic determination of ethylenethiourea residues without derivatization

Abstract

A new gas chromatographic method reliable in the microgram range, was developed to measure ETU residues in various crops. Contrary to previously published procedures, this new method does not require prior derivatization of the ETU. The limit of sensitivity was shown to be 0.01 ppm using the flame photometric detector, FPD (sulfur mode, 394 nm).     

Impact of Carbon Storage Through Restoration of Drylands on the Global Carbon Cycle

   Using estimates of land suitable for restoration in woodlands, grasslands, and deserts, as well as estimates of the rate at which restoration can proceed, we estimate that carbon storage in these biomes can range up to 0.8 billion tons of carbon per year (Gt C/yr), for a combination of land management strategies. This corresponds to a reduction in atmospheric buildup of 0.5 Gt C/yr, which represents up to 15% of the average annual atmospheric carbon buildup in the next century, 3.5 Gt C/yr, assuming the IPCC 92d scenario. A global strategy for reducing atmospheric carbon dioxide concentration will require the implementation of multiple options. The advantage of carbon storage in restored drylands is that it comes as a side benefit to programs that are also justifiable in terms of land management.     

Evidence of response of vegetation to environmental change on high-elevation sites in the Swiss Alps

Climate change has in the past led to shifts in vegetation patterns; in a future, warmer climate due to enhanced greenhouse-gas concentrations, vegetation is also likely to be highly responsive to such warming. Mountain regions are considered to be particularly sensitive to such changes. In this paper we present an approach to assess the impact of climate change on long-term vegetation plots at the high-elevation site of the Schynige Platte, 2000 m above sea level, in the Bernese Alps (Switzerland). Records of vegetation spanning the period from 1928 to today at two different sites, each with several plots, were considered. The observed change in the species composition was then related to changes in land use and climate. We used daily values of temperature, snow and precipitation from several high-elevation weather stations to conduct these analyses. The correlation between climate and vegetation patterns revealed that species that prefer low thermal conditions move out of the plots, i.e., their frequency of occurrence is negatively correlated with the average number of degree-days over the last six decades. On the other hand, species with higher thermal demands are seen to be invading the plots, i.e., their frequency of occurrence is positively correlated to the average number of degree-days. Nutrient changes – though independent from climate – also play an important role in the observed shifts in species. Received: 20 June 1999 · Accepted: 14 January 2000     

MANAGING CRISIS: THE EFFECTIVENESS OF LOCAL DISTRICTS FOR CONTROL OF GROUND WATER MINING1

: This article examines the willingness and capacity of local districts to control ground water mining of the Ogallala Aquifer in the High Plains. The questions of willingness and capacity were approached through extensive field interviews and a survey of all district board members and managers. The analysis focuses on the policy alternatives board members and managers perceive and how they evaluate these alternatives. Methodologically, the study utilized factor analysis of responses rating the desirability of various policy alternatives to ascertain what alternatives were perceived by the sample. Then the sample's preferences for each of the identified factors were calculated. The results demonstrate that the sample of those who must regulate if ground water mining is to be controlled at the substate level are not oriented to regulatory policies and therefore lack the willingness to deal with ground water mining.