Soil sensitivity to acidification in Asia: status and prospects

Exceedance of steady-state critical loads for soil acidification is consistently found in southern China and parts of SE Asia, but there is no evidence of impacts outside of China. This study describes a methodology for calculating the time to effects for soils sensitive to acidic deposition in Asia under potential future sulfur (S), nitrogen (N), and calcium (Ca) emission scenarios. The calculations are matched to data availability in Asia to produce regional-scale maps that provide estimates of the time (y) it will take for soil base saturation to reach a critical limit of 20% in response to acidic inputs. The results show that sensitive soil types in areas of South, Southeast, and East Asia, including parts of southern China, Burma, Hainan, Laos, Thailand, Vietnam, and the Western Ghats of India, may acidify to a significant degree on a 0-50 y timescale, depending on individual site management and abiotic and biotic characteristics. To make a clearer assessment of risk, site-specific data are required for soil chemistry and deposition (especially base cation deposition); S and N retention in soils and ecosystems; and biomass harvesting and weathering rates from sites across Asia representative of different soil and vegetation types and management regimes. National and regional assessments of soils using the simple methods described in this paper can provide an appreciation of the time dimension of soil acidification-related impacts and should be useful in planning further studies and, possibly, implementing measures to reduce risks of acidification.     

Benchmarking Optical/Thermal Satellite Imagery for Estimating Evapotranspiration and Soil Moisture in Decision Support Tools

Generally, one expects evapotranspiration (ET) maps derived from optical/thermal Landsat and MODIS satellite imagery to improve decision support tools and lead to superior decisions regarding water resources management. However, there is lack of supportive evidence to accept or reject this expectation. We “benchmark” three existing hydrologic decision support tools with the following benchmarks: annual ET for the ET Toolbox developed by the United States Bureau of Reclamation, predicted rainfall‐runoff hydrographs for the Gridded Surface/Subsurface Hydrologic Analysis model developed by the U.S. Army Corps of Engineers, and the average annual groundwater recharge for the Distributed Parameter Watershed Model used by Daniel B. Stephens & Associates. The conclusion of this benchmark study is that the use of NASA/USGS optical/thermal satellite imagery can considerably improve hydrologic decision support tools compared to their traditional implementations. The benefits of improved decision making, resulting from more accurate results of hydrologic support systems using optical/thermal satellite imagery, should substantially exceed the costs for acquiring such imagery and implementing the remote sensing algorithms. In fact, the value of reduced error in estimating average annual groundwater recharge in the San Gabriel Mountains, California alone, in terms of value of water, may be as large as $1 billion, more than sufficient to pay for one new Landsat satellite.     

Young northern pike,yellow perch and crayfish as bioindicators in a mercury contaminated watercourse

Young-of-the-year and yearling northern pike (Esox lucius), yearling yellow perch (Perca flavescens) and adult crayfish (Orconectes virilis) were collected in the mercury-contaminated Wabigoon/English/Winnipeg River System, Ontario, and analyzed for total mercury. Analysis of mercury concentrations in these organisms produced consistent geographical trends; i.e. mercury concentrations in biota downstream of Dryden > English River system > Winnipeg River system > control sites. In the Wabigoon River system the bioavailability of mercury increases with distance downstream of the historical point source. Mercury concentrations in the biota studied were highly correlated with mercury concentrations in fish species which are of sport and commercial interest. The locations where young fish obtain their bodyburdens are known typically within 100 m. The biota studied compare favourably with the criteria proposed by Phillips (1980) as prerequisites for biological indicators. The wide distribution of young pike, perch and crayfish in North America, Europe and Asia may enhance their appeal as biomonitors.The views expressed are those of the authors and do not necessarily reflect the views of the Ontario Ministry of the Environment. No endorsement should be inferred.     

土壤中嗪草酮迁移和降解的研究

 通过两季马铃薯大田试验，研究了嗪草酮在灌溉沙壤土中的消失和移动情况。结果表明，表层土壤中，嗪草酮施用后最初7～15天内其含量急剧降低，此后随时间推移降低幅度平缓，1993年和1994年试验结束时的残留量分别为5.9μg/kg和2.3μg/kg。两年共采集的379个土样（分布在15～75cm各土层）中只有5个检测到有嗪草酮。1994年大田135cm土层处的水样中，嗪草酮的检测率高达66％，检测浓度范围为0.06～15.85μg/kg，平均浓度为1.94μg/kg。相比较，嗪草酮在大田试验中的消失速率远大于实验室控制条件下的降解速率。     

Evaluating microbial purification during soil treatment of wastewater with multicomponent tracer and surrogate tests

Soil treatment of wastewater has the potential to achieve high purification efficiency, yet the understanding and predictability of purification with respect to removal of viruses and other pathogens is limited. Research has been completed to quantify the removal of virus and bacteria through the use of microbial surrogates and conservative tracers during controlled experiments with three-dimensional pilot-scale soil treatment systems in the laboratory and during the testing of full-scale systems under field conditions. The surrogates and tracers employed included two viruses (MS-2 and PRD-1 bacteriophages), one bacterium (ice-nucleating active Pseudomonas), and one conservative tracer (bromide ion). Efforts have also been made to determine the relationship between viruses and fecal coliform bacteria in soil samples below the wastewater infiltrative surface, and the correlation between Escherichia coli concentrations measured in percolating soil solution as compared with those estimated from analyses of soil solids. The results suggest episodic breakthrough of virus and bacteria during soil treatment of wastewater and a 2 to 3 log (99-99.9%) removal of virus and near complete removal of fecal coliform bacteria during unsaturated flow through 60 to 90 cm of sandy medium. Results also suggest that the fate of fecal coliform bacteria may be indicative of that of viruses in soil media near the infiltrative surface receiving wastewater effluent. Concentrations of fecal coliform in percolating soil solution may be conservatively estimated from analysis of extracted soil solids.     

Maternal age-specific risks for trisomies at 9—14 weeks' gestation

This study provides data on the incidence of fetal trisomies 21, 18, and 13 at 9–14 weeks' gestation in women aged 35–45 years and estimates of maternal age-specific risks in women aged 20–45 years. Our data from 5814 singleton pregnancies undergoing first-trimester karyotyping for the sole indication of maternal age ⩾ 35 years were combined with those from two previous reports and the incidence of the trisomies was calculated from a total of 15 793 pregnancies. Comparison of incidences at 9–14 weeks' gestation with published data at 15–20 weeks' gestation and in livebirths demonstrated that at birth the maternal age-specific incidence of trisomy 21 is 33 per cent lower than at 15–20 weeks' gestation and 54 per cent lower than at 9–14 weeks' gestation. Furthermore, the relative frequency of trisomies 18 and 13 decreases from 30 per cent at 9–14 weeks to 22 per cent at 15–20 weeks and 14 per cent at birth.     

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).     

Evolution of reproductive features and larval development in the genus Amphiglena (Polychaeta: Sabellidae)

Larval development in Amphiglena mediterranea is direct in the parental tube, and larvae crawl away as young juveniles with a radiolar crown capable of feeding. The non-feeding larvae of A. nathae are initially brooded in the parental tube, and then have a swimming phase before settling and developing a radiolar crown. Developmental data and reproductive features such as sperm structure are combined with other morphological data for an assessment of the cladistic relationships of the species in the genus Amphiglena. Two species of Laonome are included as part of the ingroup. Six genera, representing a sister group to the Laonome/Amphiglena clade, are used as an outgroup. Two most-parsimonious cladograms were found, and the evolution of reproductive features are discussed. The monophyly of Amphiglena is indicated by features previously identified, as well as two features based on sperm morphology. At present a plesiomorphic larval form cannot be identified for the genus Amphiglena. Received: 16 June 1997 / Accepted: 29 January 1998     

Mercury exposure through diet in pregnant women and women of childbearing age

The study examined the stage of clean-up of the Port Lavaca bay sites in Texas, which were polluted during the early 1990's by effluent containing mercury (Hg) from a chloralkali plant. In addition to Hg intoxication through environmental contaminations, human exposure through dietary fish and other seafoods occurred. Bacteria converts inorganic Hg to alkyl organic compounds and subsequently the metal crosses the blood brain barrier thus exerting adverse effects on the fetal developing nervous system. In order to conduct a survey of dietary Hg exposure, blood was collected from pregnant women and those of childbearing age at routine clinic visits at each of three centers in South Texas cities (Galveston, Texas City, Port Lavaca/Victoria, TX). A questionnaire sought dietary and lifestyle information including consumption, sources of fish and other seafoods. A significant number of subjects (119 out of 175, 68%) ate fish caught locally. The blood Hg concentrations (µg?L^?1) range varied with the location of the study centers: City of Galveston 2.6–62; Texas City 2.8–111.8; and the Port Lavaca areas 3.02–126.7. The concentrations of blood Hg was directly proportional to the number of fish meals consumed for each species considered. Mean blood Hg concentrations for no fish meals per week were: Port Lavaca 4.5 (N?=?3), Galveston 4.3 (N?=?3), Texas City 3.5 (N?=?10). For >3 fish meals per week, the mean blood Hg concentrations were: Port Lavaca, 48.0 (N?=?53), Galveston 29.1 (N?=?35), Texas City, 36.1 (N?=?31). Data show that residues of Hg were still present in 1994 despite the clean-up efforts.