The Arsenic Contamination of Drinking and Groundwaters in Bangladesh: Featuring Biogeochemical Aspects and Implications on Public Health.

Arsenic is a widespread contaminant of drinking and groundwaters in the world. Even if these contaminations have a geogenic origin, they often are exacerbated by anthropogenic activities. This is particularly true for the Bengal delta. Millions of people in Bangladesh are consuming drinking water with arsenic concentrations ≥ 50 µg/L. Their drinking water supply is based on groundwaters extracted by pumping wells, which were part of a well-drilling program by the United Nations. The intention was to provide the people with groundwater instead of surface water due to its critical hygienic conditions. Unfortunately, many wells extract the groundwater at depths where arsenic concentrations are highest. Arsenic is being dissolved from the aquifer by biogeochemical processes that are fueled by the presence of high amounts of organics in the Bengal delta sediments. This problem was not encountered at the time due to a lack of chemical analyses of the waters.

Secreted pitfall-trap fluid of carnivorous Nepenthes plants is unsuitable for microbial growth.

BACKGROUND AND AIMS: Carnivorous plants of the genus Nepenthes possess modified leaves that form pitfall traps in order to capture prey, mainly arthropods, to make additional nutrients available for the plant. These pitchers contain a digestive fluid due to the presence of hydrolytic enzymes. In this study, the composition of the digestive fluid was further analysed with regard to mineral nutrients and low molecular-weight compounds. A potential contribution of microbes to the composition of pitcher fluid was investigated. METHODS: Fluids from closed pitchers were harvested and analysed for mineral nutrients using analytical techniques based on ion-chromatography and inductively coupled plasma-optical emission spectroscopy. Secondary metabolites were identified by a combination of LC-MS and NMR. The presence of bacteria in the pitcher fluid was investigated by PCR of 16S-rRNA genes. Growth analyses of bacteria and yeast were performed in vitro with harvested pitcher fluid and in vivo within pitchers with injected microbes. KEY RESULTS: The pitcher fluid from closed pitchers was found to be primarily an approx. 25-mm KCl solution, which is free of bacteria and unsuitable for microbial growth probably due to the lack of essential mineral nutrients such as phosphate and inorganic nitrogen. The fluid also contained antimicrobial naphthoquinones, plumbagin and 7-methyl-juglone, and defensive proteins such as the thaumatin-like protein. Challenging with bacteria or yeast caused bactericide as well as fungistatic properties in the fluid. Our results reveal that Nepenthes pitcher fluids represent a dynamic system that is able to react to the presence of microbes. CONCLUSIONS: The secreted liquid of closed and freshly opened Nepenthes pitchers is exclusively plant-derived. It is unsuitable to serve as an environment for microbial growth. Thus, Nepenthes plants can avoid and control, at least to some extent, the microbial colonization of their pitfall traps and, thereby, reduce the need to vie with microbes for the prey-derived nutrients.

Determination of water-extractable nonstructural carbohydrates, including inulin, in grass samples with high-performance anion exchange chromatography and pulsed amperometric detection.

The exact and reliable determination of carbohydrates in plant samples of different origin is of great importance with respect to plant physiology. Additionally, the identification and quantification of carbohydrates are necessary for the evaluation of the impact of these compounds on the biogeochemistry of carbon. To attain this goal, it is necessary to analyze a great number of samples with both high sensitivity and selectivity within a limited time frame. This paper presents a rugged and easy method that allows the isocratic chromatographic determination of 12 carbohydrates and sugar alcohols from one sample within 30 min. The method was successfully applied to a variety of plant materials with particular emphasis on perennial ryegrass samples of the species Lolium perenne. The method was easily extended to the analysis of the polysaccharide inulin after its acidic hydrolysis into the corresponding monomers without the need for substantial change of chromatographic conditions or even the use of enzymes. It therefore offers a fundamental advantage for the analysis of the complex mixture of nonstructural carbohydrates often found in plant samples.

A novel single-run dual temperature combustion (SRDTC) method for the determination of organic, in-organic and total carbon in soil samples.

The quantification of organic (OC) and inorganic carbon (IC) in soils provides an essential tool for understanding biogeochemical processes. Examples of its potential application are the assessment of the humification degree of soil organic matter, the calculation of carbon fluxes and budgets in terrestrial systems on a regional and global scale and the investigation of the carbon storage potential of soils. The verification of changes in carbon stocks requires an extensive number of samples as well as precise and reliable analyses. Due to the wide variation in the concentrations of the two forms of carbon in solid samples, the exact distinction is very difficult. We present the advantages of a single-run dual temperature combustion method (SRDTC) at 515 degrees C for OC and 925 degrees C for IC, which allows the determination of OC, IC and total carbon (TC) within one single analytical run. The three parameters are analyzed in less than 30 min. Additionally, the method is characterized by a significantly reduced variability and low operator bias, as there is no need of chemical sample pre-treatment. It is applicable to a broad range of varying OC and IC contents, which is demonstrated by the use of numerous synthetic soil mixtures that have been analyzed. Furthermore, SRDTC indicates the presence of thermally instable carbonates, like magnesite, in the sample. Use of silver boats as a catalytic agent results in an improved distinction between OC and IC in this case. To examine the accuracy and reliability of the SRDTC method, it was compared to other techniques frequently used for carbon determination in soil samples: total combustion by elemental analysis to determine TC and acidification of the sample prior to combustion to determine OC. We will show that the rugged SRDTC method offers a substantial progress for both the reliable and rapid OC and IC determination in soil samples where elemental carbon is negligible.

Accurate determination of Cd, Cr, Cu and Ni in woodlice and their skins--is moulting a means of detoxification?

Cd, Cr, Cu and Ni were determined in two different species of woodlice: Porcellio scaber and Porcellio dilatatus. Both P. scaber and P. dilatatus were cultivated under standardized conditions in a climatic chamber. Moreover, skins of the cultivated animals were collected and analysed separately to examine whether moulting is a way of detoxification from these elements. After drying and grinding both animal and skin samples, they were pooled to obtain enough sample material for each species. The pooled samples were digested in pure concentrated nitric acid using microwave-assisted high pressure digestion and, finally, analysed by ICP-OES. Special emphasis was given to quality control. To match the matrix of the samples very closely, the reference materials Dorm-2, Dogfish Muscle (Squalus acanthias) and SRM 1577b Bovine Liver were used to evaluate the whole analytical process including sample digestion. Analyses of the elements in the reference materials were carried out using three different wavelengths for each element simultaneously to check for spectral interferences and to select the wavelengths which were best suited for the analyses. Concentrations of Cd, Cr, Cu and Ni in woodlice and their skins indicated that moulting is a possible means of detoxification in the case of Cr and Ni.