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Bacopa monnieri is commonly known as “Brahmi” or “Water hyssop” and is a source of nootropic drugs. Aboveground parts of plant samples collected from peri-urban Indian areas were analysed for total trace metal concentrations. Subsequently, three samples with high concentrations of Cd and Pb were subjected to in vitro gastrointestinal digestion to assess the bioaccessibility of the trace metals in these plants. The total concentrations of trace metals on a dry weight basis were 1.3 to 6.7 mg · kg−1 Cd, 1.5 to 22 mg · kg−1 Pb, 36 to 237 mg · kg−1 Cu, and 78 to 186 mg · kg−1 Zn. The majority of Bacopa monnieri samples exceeded threshold limits of Cd, Pb, Cu, and Zn for use as raw medicinal plant material or direct consumption. Therefore, it is necessary to evaluate Bacopa monnieri collected in nature for their trace metal content prior to human consumption and preparation of herbal formulations.

Environmental pollution by mercury is a world-wide problem. Particularly floodplain ecosystems are frequently affected. One example is the Elbe River in Germany and its catchment areas; large amounts of Hg from a range of anthropogenic and geogenic sources have been accumulated in the soils of these floodplains. They serve as sink for Hg originating from the surface water of adjacent river. Today, the vastly elevated Hg contents of the floodplain soils at the Elbe River often exceed even the action values of the German Soil Conservation Law. This is especially important as Hg polluted areas at the Elbe River achieve several hundred square kilometres. Thus, authorities are coerced by law to conduct an appropriate risk assessment and to implement practical actions to eliminate or reduce environmental problems. A reliable risk assessment particularly with view to organisms (vegetation as green fodder and hay production, grazing and wild animals) to avoid the transfer of Hg into the human food chain, requires an authentic determination of Hg fluxes and their dynamics since gaseous emissions from soil to atmosphere are an important pathway of Hg. However, reliable estimates of Hg fluxes from the highly polluted floodplain soils at the Elbe River and its tributaries, and its influencing factors are scarce. For this purpose, we have developed a new method to determine mercury emissions from soils at various sites. Our objectives were i) to quantify seasonal variations of total gaseous mercury (TGM) fluxes for floodplain soils at the Elbe River, ii) to provide insights into physico-chemical processes regulating these TGM fluxes, and iii) to quantify the impacts of the controlling factors soil temperature and soil water content on Hg volatilization from a typical contaminated floodplain soil within soil microcosm experiments under various controlled temperature and moisture conditions. Our study provides insight into TGM emissions from highly Hg-polluted floodplain soils in

The heavy metal contamination in Lake Ohrid, a lake shared between Albania and Macedonia, was studied. Lake Ohrid is believed to be one of the oldest lakes in the world, with a large variety of endemic species. Different anthropogenic pressures, especially heavy metal influxes from mining activities, might have influenced the fragile equilibrium of the lake ecosystem. Heavy metal concentrations in water, sediment, emergent vegetation, and fish were investigated at selected sites of the lake and a study of the heavy metals in five tributaries was conducted. The lake surface water was found to have low levels of heavy metals, but sediments contained very high levels mostly near river mouths and mineral dump areas with concentrations reaching 1,501 mg/kg for Ni, 576 mg/kg for Cr, 116.8 mg/kg for Co and 64.8 g/kg for Fe. Sequential extraction of metals demonstrates that heavy metals in the sediment are mainly present in the residual fraction varying from 75% to 95% in different sites. High heavy metal levels (400 mg/kg Ni, 89 mg/kg Cr, and 39 mg/kg Co) were found in plants (stem of Phragmites australis), but heavy metals could not be detected in fish tissue (gill, muscle, and liver of Salmo letnica and Salmothymus ohridanus).

We have assessed the effect of various factors on the mobility of total mercury (Hg) as well as on the methylation of Hg in two floodplain soils with different Hg loads using an automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) in soil suspensions. The experiment was conducted under stepwise variation from reducing (approximately -240 mV at pH 5) to oxidizing (approximately 600 mV at pH 5) conditions. Analysis of phospholipid fatty acids (PLFA) indicate the occurrence of sulphate reducing bacteria such as Desulfovibrio or Desulfobulbus species, which are considered to promote Hg methylation. A direct impact of EH and pH could not be detected, instead, EH and pH indirectly affected Hg dynamics and methylation rate. Dissolved organic carbon (DOC) is an important factor controlling the dynamics and methylation of Hg. Both, Hg and methyl mercury (MeHg) in the solution increased with raising DOC. The lnMeHg/Hg ratio as the net production of MeHg normalized to the Hg concentration increases with increasing lnDOC/Hg ratio under changing EH. Thus, an amendment of organic material e.g. during remediation techniques should be avoided since this would increase the MeHg production.

A pot experiment was conducted to study the contribution of reactive phosphate rocks (RPRs) on the accumulation of Cd and Zn in 10 acid upland soils in Indonesia and shoots of Zea mays plants grown on these soils. Two types of RPR were used at a rate of 0.5 g (kg soil)-1: RPRL containing 4 mg Cd?kg-1 and 224 mg Zn?kg-1, and RPRH containing 69 mg Cd?kg-1 and 745 mg Zn?kg-1. Zea mays was harvested at 6 weeks after planting. The application of RPRH significantly increased the concentrations of Cd in the shoots. The application of this RPR also increased the amount of Cd which could be extracted by 0.5 M NH4-acetate + 0.02 M EDTA pH 4.65 from the soils. More than 90% of the added Cd remained in the soil. As Zn is an essential element and the studied acid upland soils are Zn-deficient, increased plant growth upon RPR application might be partly attributed to Zn present in the phosphate rock. However, more experiments are needed to confirm this hypothesis. The Cd and Zn concentrations and CEC of the soils were important soil factors influencing the concentrations of Cd and Zn in the shoots of maize plants grown on these soils.

Environmental pollution by mercury (Hg) is a considerable environmental problem world-wide. Due to the occurrence of Hg volatilization from their soils, floodplains can function as an important source of volatile Hg. Soil temperature and soil water content related to flood dynamics are considered as important factors affecting seasonal dynamics of total gaseous mercury (TGM) fluxes. We quantified seasonal variations of TGM fluxes and conducted a laboratory microcosm experiment to assess the effect of temperature and moisture on TGM fluxes in heavily polluted floodplain soils. Observed TGM emissions ranged from 10 to 850 ng m-2 h-1 and extremely exceeded the emissions of non-polluted sites. TGM emissions increased exponentially with raised air and soil temperatures in both field (R2: 0.49-0.70) and laboratory (R2: 0.99) experiments. Wet soil material showed higher TGM fluxes, whereas the role of soil water content was affected by sampling time during the microcosm experiments.Warmer environmental conditions result in higher Hg volatilization rates from floodplain soils.

Different methods exist for measuring water and solute flux in and below the root zone. Besides indirect methods (e.g. water balance, tensiometer, time domain reflectometry, frequency domain reflectometry and environmental tracer, direct methods(e.g. drainagetype lysimeter, water flux meter)have a long tradition and have been successfully used in seepage research. However, lysimeters are most reliable and accurate for in situ water and solute assessment. A large weighable outdoor lysimeter is the best method for obtaining reliable data about seepage water quantity and quality, but it involves significant investment and additional expenses for maintenance. To tackle this problem new methods for the vertical collection of large volume soil monoliths and for the placement of the lysimeter in a container lysimeter unit have been developed. The design of lysimeters typically used in Europe - a weighable gravitation lysimeter and a weighable groundwater lysimeter are explained. An example is given for the high precision of the new lysimeter weighing technique. Besides recording rainfall and seepage, its weighing precision makes it possible to register mass input by dew, fog or rime. It also permitsaccurate calculation of actual evapotranspiration. The newly developed lysimeter types will be an essential tool for scaling up results obtained in small-scale experiments to larger geographical units. Furthermore, the newly developed experimental set-up allows a scenario simulation of topical climatic and hydrologic questions, e.g. global warming and its impact on the water and solute balance, the influence of dew and fog on the establishment of a vegetation cover in arid areas or the transport of contaminants during heavy rainfall following a severe drying-up of the soil profile.

Wetlands at the riverside of the UNESCO Biosphere Reserve "Central Elbe" are highly contaminated by heavy metals, especially mercury (Hg). The Hg-polluted Elbe floodplain soils turn out to be a source of gaseous mercury via Hg volatilization from soil into the atmosphere. A modified field sampling method was used to measure total gaseous mercury (TGM) volatilization from three different sites at the Elbe River. The modified setup had a reduced chamber size and contained an internal gas circulation system. An in-ground stainless steel cylinder minimizes Hg volatilization from adjacent soil air. Cold vapor atomic absorption spectrometry (CV-AAS) was used to determine TGM amalgamated on gold traps. Sampled TGM amounts ranged between 0.02 and 0.63 ng (absolute), whereas the calculated Hg fluxes varied from 2.0 to 63.3 ng m-2 h-1. The modified system should allow measurements of Hg volatilization at various sites with a high spatial resolution, which should enable the study of interrelations between TGM emission and several key factors influencing Hg emission from floodplain soils at the Elbe River and other riverine ecosystems in the near future.

Total metal content in the soil in itself is insufficient as a measure to indicate the actual environmental risks involved with soil contamination. Understanding the mobility of heavy metals in the soil and their speciation in the soil solution is of great importance for accurately assessing environmental risks posed by these metals. Solid-solution partition coefficients (soil-water distribution coefficient [K d]) for copper (Cu) and lead (Pb) were analyzed in a range of clean and contaminated agricultural soils, and metal speciation in soil solution was assessed. The influence of variables such as pH, soil organic carbon, clay content, and total soil metal concentration on the solid-solution partitioning and speciation of Cu and Pb were evaluated using multiple regression models. The best models were obtained for Kd that are based on total metal concentrations in both the soil solid phase, and the pore water and the various metal binding phases. In general, between 70% and 90% of the total variance was explained. The explained variance was significantly increased by taking the activity of the free metal into account. Strong correlations (R 2 = 0.88) were obtained by multiple regression analysis involving free metal ion (Cu 2+, Pb 2+) concentrations calculated with the equilibrium speciation model, Windermere Humic Aqueous Model/Model VI. Copyright © 2009 by Lippincott Williams & Wilkins, Inc.