Arsenic chemistry in the rhizosphere of Pteris vittata L. and Nephrolepis exaltata L

This greenhouse experiment evaluated the influence of arsenic uptake by arsenic hyperaccumulator Pteris vittata L. and non-arsenic hyperaccumulator Nephrolepis exaltata L. on arsenic chemistry in bulk and rhizosphere soil. The plants were grown for 8 weeks in a rhizopot with a soil containing 105 mg kg(-1) arsenic. The soil arsenic was fractionated into five fractions with decreasing availability: non-specifically bound (N), specifically bound (S), amorphous hydrous-oxide bound (A), crystalline hydrous-oxide bound (C), and residual (R). P. vittata produced larger plant biomass (7.38 vs. 2.32 mg plant(-1)) and removed more arsenic (2.61 vs. 0.09 mg pot(-1) arsenic) than N. exaltata. Plant growth reduced water-soluble arsenic, and increased soil pH (P. vittata only) in the rhizosphere soil. P. vittata was more efficient than N. exaltata to access arsenic from all fractions (39-64% vs. 5-39% reduction). However, most of the arsenic taken up by both plants was from the A fraction (67-77%) in the rhizosphere soil, the most abundant (61.5%) instead of the most available (N fraction).     

In situ ground water denitrification in stratified, permeable soils underlying riparian wetlands

The ground water denitrification capacity of riparian zones in deep soils, where substantial ground water can flow through low-gradient stratified sediments, may affect watershed nitrogen export. We hypothesized that the vertical pattern of ground water denitrification in riparian hydric soils varies with geomorphic setting and follows expected subsurface carbon distribution (i.e., abrupt decline with depth in glacial outwash vs. negligible decline with depth in alluvium). We measured in situ ground water denitrification rates at three depths (65, 150, and 300 cm) within hydric soils at four riparian sites (two per setting) using a 15N-enriched nitrate "push-pull" method. No significant difference was found in the pattern and magnitude of denitrification when grouping sites by setting. At three sites there was no significant difference in denitrification among depths. Correlations of site characteristics with denitrification varied with depth. At 65 cm, ground water denitrification correlated with variables associated with the surface ecosystem (temperature, dissolved organic carbon). At deeper depths, rates were significantly higher closer to the stream where the subsoil often contains organically enriched deposits that indicate fluvial geomorphic processes. Mean rates ranged from 30 to 120 microg N kg(-1) d(-1) within 10 m versus <1 to 40 microg N kg(-1) d(-1) at >30 m from the stream. High denitrification rates observed in hydric soils, down to 3 m within 10 m of the stream in both alluvial and glacial outwash settings, argue for the importance of both settings in evaluating the significance of riparian wetlands in catchment-scale N dynamics.     

Mycorrhizae increase arsenic uptake by the hyperaccumulator Chinese brake fern (Pteris vittata L.)

Chinese brake fern (Pteris vittata L.) is a hyperaccumulator of arsenic (As) that grows naturally on soils in the southern United States. It is reasonable to expect that mycorrhizal symbiosis may be involved in As uptake by this fern. This is because arbuscular mycorrhizal (AM) fungi have a well-documented role in increasing plant phosphorus (P) uptake, P and As have similar chemical properties, and ferns are known to be colonized by AM fungi. We conducted a factorial greenhouse experiment with three levels of As (0, 50, and 100 mg kg(-1)) and P (0, 25, and 50 mg kg(-1)) and with and without Chinese brake fern colonized by a community of AM fungi from an As-contaminated site. We found that the AM fungi not only tolerated As amendment, but their presence increased frond dry mass at the highest As application rate. Furthermore, the AM fungi increased As uptake across a range of P levels, while P uptake was generally increased only when there was no As amendment. These data indicate that AM fungi have an important role in arsenic accumulation by Chinese brake fern. Therefore, to effectively phytoremediate As-contaminated soils, the mycorrhizal status of ferns needs to be taken into account.     

Induced anti-predator responses of the green mussel, Perna viridis (L.), on exposure to the predatory gastropod, Thais clavigera Küster, and the swimming crab, Thalamita danae Stimpson

A laboratory experiment was conducted to test whether anti-predator responses could be induced in the green mussel, Perna viridis, on exposure to waterborne cues from two predators, the muricid gastropod, Thais clavigera, and the portunid crab, Thalamita danae, and from damaged conspecifics. There were five treatments in this study. Aquaria of two treatments housed either Thalamita danae or Thais clavigera. Another three treatments housed only intact mussels, broken and intact mussels, or no mussels. No significant differences were found among these five treatments in final shell weight and tissue dry weight. Induced defensive responses were predator-specific. Experimental mussels exposed to waterborne cues of T. clavigera had a higher percentage increase in shell length, height and width, whereas those exposed to waterborne cues of T. danae had a higher percentage increase in shell width and height. Mussels raised in the presence of crabs developed thicker shell at the umbo and lip margin, whereas mussels raised in the presence of gastropods had thicker shell lip. Predator preference for mussels from the control group and for those pre-exposed to waterborne cues of either of the predators was studied. T. clavigera preferentially selected mussels from the control group, whereas no prey preference was found for T. danae, although shell breaking time for mussels exposed to a crab was longer than that for the control. While the present results should be viewed with caution in the absence of a dietary control, this was the first time that prey handling was shown to be affected by defensive changes in the morphology of mussels.Communicated by T. Ikeda, Hakodate     

Prenatal diagnosis of trisomy 9. Six cases and a review of the literature

Six prenatally diagnosed cases of trisomy 9 are reported and 22 previously reported cases are reviewed; the difficulty of genetic counselling for such cases and the variation in the percentage of trisomic cells in different tissues, thus making accurate diagnosis of trisomy 9 difficult, are emphasized. In addition to karyotyping results, ultrasound findings are important in achieving diagnoses. Finally, a course of action when prenatal trisomy 9 is detected is proposed.     

Solid waste characterization,quantification and management practices in developing countries. A case study: Nablus district – Palestine

Solid waste management (SWM) is one of the most challenging issues faced by developing countries that suffer from serious pollution problems caused by the generation of large waste quantities. This paper presents the case study of SWM in the Nablus district – Palestine. Surveys for household residents' and SWM program operators, field investigations, on-site waste measurements and characterizations were conducted. Per capita waste generation rates varied between different localities although trends were similar. Overall, the majority of waste was organic (65.1% by weight), suggesting a strong resource recovery potential in terms of animal feed or compost. Recyclable waste (plastic, paper and card) made up 16.7% by weight the waste composition suggesting an incentive to introduce source separation. Household attitudes complemented the waste characterization study, revealing the main problems faced. SWM operators quoted on the current status, highlighting problems with disposing in unsanitary landfills, ineffective solid waste fees system, increasing solid waste quantities and lacking equipment and experienced personnel. To enhance sustainable SWM, public awareness, funding, expertise, equipment and facilities and other provisions currently lacking or inappropriate must be provided.     

Effects of pH and ionic strength on sulfamethoxazole and ciprofloxacin transport in saturated porous media

Many antibiotics regarded as emerging contaminants have been frequently detected in soils and groundwater; however, their transport behaviors in soils remain largely unknown. This study examined the transport of two antibiotics, sulfamethoxazole (SMZ) and ciprofloxacin (CIP), in saturated porous media. Laboratory columns packed with quartz sand was used to test the effects of solution pH and ionic strength (IS) on their retention and transport. The results showed that these two antibiotics behaved differently in the saturated sand columns. In general, SMZ manifested a much higher mobility than CIP for all experimental conditions tested. Almost all SMZ transported through the columns within one pore volume in deionized water (i.e., pH=5.6, IS=0), but no CIP was detected in the effluents under the same condition after extended column flushing. Perturbations in solution pH (5.6 and 9.5) and IS (0 and 0.1M) showed no effect on SMZ transport in the saturated columns. When pH increased to 9.5, however, ~93% of CIP was eluted from the sand columns. Increase of IS from 0 to 0.1M also slightly changed the distribution of adsorbed CIP within the sand column at pH 5.6, but still no CIP was detected in the effluents. A mathematical model based on advection-dispersion equation coupled with equilibrium and kinetic reactions successfully simulated the transport of the antibiotics in water-saturated porous media with R(2)=0.99.     

Net emissions of CH4 and CO2 in Alaska: implications for the region's greenhouse gas budget.

We used a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to study the net methane (CH4) fluxes between Alaskan ecosystems and the atmosphere. We estimated that the current net emissions of CH4 (emissions minus consumption) from Alaskan soils are approximately 3 Tg CH4/yr. Wet tundra ecosystems are responsible for 75% of the region's net emissions, while dry tundra and upland boreal forests are responsible for 50% and 45% of total consumption over the region, respectively. In response to climate change over the 21st century, our simulations indicated that CH4 emissions from wet soils would be enhanced more than consumption by dry soils of tundra and boreal forests. As a consequence, we projected that net CH4 emissions will almost double by the end of the century in response to high-latitude warming and associated climate changes. When we placed these CH4 emissions in the context of the projected carbon budget (carbon dioxide [CO2] and CH4) for Alaska at the end of the 21st century, we estimated that Alaska will be a net source of greenhouse gases to the atmosphere of 69 Tg CO2 equivalents/yr, that is, a balance between net methane emissions of 131 Tg CO2 equivalents/yr and carbon sequestration of 17 Tg C/yr (62 Tg CO2 equivalents/yr).     

Efficiency of Reovirus Concentration from Water with Positively Charged Filters

This study examined the efficacy of reovirus concentration from large volumes of water using two positively charged filters: Zeta Plus 1MDS and NanoCeram. The results indicated that an average of 61 and 81% of input reoviruses were effectively recovered, respectively, from recycled water and tap water using NanoCeram filtration.