The Mysterious Mauritian Red Nectar: A Selective Toxicant?

 Using knowledge-based computational structure-activity relationship models, it is hypothesized that the aurone responsible for the uniquely red nectar of several Mauritian bird-pollinated plants functions as a repellant of nectar-robbing or herbivorous mammalian species. Received: 30 November 1998 / Accepted: 18 March 1999     

Street floods in Metro Manila and possible solutions

Urban floods from thunderstorms cause severe problems in Metro Manila due to road traffic. Using Light Detection and Ranging (LiDAR)-derived topography, flood simulations and anecdotal reports, the root of surface flood problems in Metro Manila is identified. Majority of flood-prone areas are along the intersection of creeks and streets located in topographic lows. When creeks overflow or when rapidly accumulated street flood does not drain fast enough to the nearest stream channel, the intersecting road also gets flooded. Possible solutions include the elevation of roads or construction of well-designed drainage structures leading to the creeks. Proposed solutions to the flood problem of Metro Manila may avoid paralyzing traffic problems due to short-lived rain events, which according to Japan International Cooperation Agency (JICA) cost the Philippine economy 2.4 billion pesos/day.     

A role for selective contraception of individuals in conservation

Contraception has an established role in managing overabundant populations and preventing undesirable breeding in zoos. We propose that it can also be used strategically and selectively in conservation to increase the genetic and behavioral quality of the animals. In captive breeding programs, it is becoming increasingly important to maximize the retention of genetic diversity by managing the reproductive contribution of each individual and preventing genetically suboptimal breeding through the use of selective contraception. Reproductive suppression of selected individuals in conservation programs has further benefits of allowing animals to be housed as a group in extensive enclosures without interfering with breeding recommendations, which reduces adaptation to captivity and facilitates the expression of wild behaviors and social structures. Before selective contraception can be incorporated into a breeding program, the most suitable method of fertility control must be selected, and this can be influenced by factors such as species life history, age, ease of treatment, potential for reversibility, and desired management outcome for the individual or population. Contraception should then be implemented in the population following a step‐by‐step process. In this way, it can provide crucial, flexible control over breeding to promote the physical and genetic health and sustainability of a conservation dependent species held in captivity. For Tasmanian devils (Sarcophilus harrisii), black‐flanked rock wallabies (Petrogale lateralis), and burrowing bettongs (Bettongia lesueur), contraception can benefit their conservation by maximizing genetic diversity and behavioral integrity in the captive breeding program, or, in the case of the wallabies and bettongs, by reducing populations to a sustainable size when they become locally overabundant. In these examples, contraceptive duration relative to reproductive life, reversibility, and predictability of the contraceptive agent being used are important to ensure the potential for individuals to reproduce following cessation of contraception, as exemplified by the wallabies when their population crashed and needed females to resume breeding.     

Influence of combustion conditions on yields of solvent-extractable anhydrosugars and lignin phenols in chars: Implications for characterizations of biomass combustion residues

Anhydrosugars, such as levoglucosan and its isomers (mannosan, galactosan), as well as the solvent-extractable lignin phenols (methoxylated phenols) are thermal degradation products of cellulose/hemicellulose and lignin, respectively. These two groups of biomarkers are often used as unique tracers of combusted biomass inputs in diverse environmental media. However, detailed characterization of the relative proportion and signatures of these compounds in highly heterogeneous plant-derived chars are still scarce. Here we conducted a systematic study to investigate the yields of solvent-extractable anhydrosugars and lignin phenols in 25 lab-made chars produced from different plant materials under different combustion conditions. Solvent-extractable anhydrosugars and lignin phenols were only observed in chars formed below 350 °C and yields were variable across different combustion temperatures. The yields of mannosan (M) and galactosan (G) decreased more rapidly than those of levoglucosan (L) under increasing combustion severity (temperature and duration), resulting in variable L/M and L/(M + G) ratios, two diagnostic ratios often used for identification of combustion sources (e.g. hardwoods vs. softwoods vs. grasses). Our observations thus may provide an explanation for the wide ranges of values reported in the literature for these two ratios. On the other hand, the results of this study suggest that the ratios of the major solvent-extractable lignin phenols (vanillyls (V), syringyls (S), cinnamyls (C)) provide additional source reconstruction potential despite observed variations with combustion temperature. We thus propose using a property-property plot (L/M vs. S/V) as an improved means for source characterization of biomass combustion residues. The L/M-S/V plot has shown to be effective in environmental samples (soil organic matter, atmospheric aerosols) receiving substantial inputs of biomass combustion residues.     

Comparing the Community Composition of European and Eastern Chinese Waterbirds and the Influence of Human Factors on the China Waterbird Community

We compared the European and eastern Chinese waterbird assemblages and checked whether the effects of human disturbance could be detected in the assemblages’ composition. For the different Chinese provinces, we expected to find a negative effect of economic development on the mean bird species mass and on the proportion of bentivorous, piscivorous and insectivorous bird species. We also expected to find relatively fewer large species in the Chinese assemblage. Species rank–abundance curves were relatively similar, but China had significantly more species with smaller body masses. The China assemblage was characterized by relatively higher abundance of heavy-bodied species, contrary to our expectations. Mean bird body mass decreased in China with increasing disturbance and increasing gross domestic product (GDP). For coastal provinces in China the percentage of bentivorous, piscivorous and insectivorous bird species declined with increasing GDP, maybe through the increased use of pesticides or fertilizer.     

Wind Characteristics of Mesquite Streets in the Northern Chihuahuan Desert, New Mexico, USA

Past research has shown that the most important areas for active sand movement in the northern part of the Chihuahuan Desert are mesquite-dominated desert ecosystems possessing sandy soil texture. The most active sand movement in the mesquite-dominated ecosystems has been shown to take place on elongated bare soil patches referred to as “streets”. Aerodynamic properties of mesquite streets eroded by wind should be included in explaining how mesquite streets are more emissive sand sources than surrounding desert land. To understand the effects of wind properties, we measured them at two flat mesquite sites having highly similar soil textures but very different configurations of mesquite. The differences in wind properties at the two sites were caused by differences of size, orientation, and porosity of the mesquite, along with the presence of mesquite coppice dunes (sand dunes stabilized by mesquites growing in the dune and on its surface) found only at one of the two sites. Wind direction, u_* (friction velocity), z₀ (aerodynamic roughness height) and D (zero plane displacement height) were estimated for 15-m tower and 3-m mast data. These aerodynamic data allowed us to distinguish five categories with differing potentials for sediment transport. Sediment transport for the five categories varied from unrestricted, free transport to virtually no transport caused by vegetation protection from wind forces. In addition, “steering” of winds below the level of the tops of mesquite bushes and coppice dunes allowed longer parallel wind durations and increased wind erosion for streets that aligned roughly SW–NE. U.S. Government right to retain a non-exclusive royalty-free licence in and to any copyright is acknowledged.     

Collaborative Testing of Methods to Measure Air Pollutants II. The Non-Dispersive Infrared Method for Carbon Monoxide

The Methods Standardization Branch of the Environmental Protection Agency, National Environmental Research Center, has undertaken a program to standardize methods used in measuring air pollutants covered by the national primary and secondary air quality standards. This paper presents the results of a collaborative test of the method specified for carbon monoxide.

The test involved analysis of CO in air samples (in cylinders) by participating laboratories. Three concentrations, covering the range of the method which is, 0 to 58 mg/m³, were analyzed dry and humidified on each of three days by 15 collaborators. The method of analysis, nondispersive infrared spectrometry (NDIR), involved an NDIR instrument in combination with different procedures for eliminating water vapor interference. A statistical analysis of the data obtained produced the following results: 1. The checking limit for duplicates (replication error) is 0.5 mg/m³.

2. The repeatability (variation within a laboratory) is 1.6 mg/m³.

3. The reproducibility (variation between laboratories) varies nonlinearly with concentration; i.e., a minimum of 2.3 mg/m³ at a concentration of 20 mg/m³ and ranges as high as 4.3 mg/m³ in the concentration range of 0 to 58 mg/m³.

4. The reproducibility at the level of the national primary ambient air quality standard, 10 mg/m³-8-hour average, is 2.5 mg/m³ or 25%.

5. The minimum detectable sensitivity is estimated to be 0.3 mg/m³.

6. Compensation for water vapor interference is satisfactorily accomplished using drying agents and refrigeration methods. The use of narrow-band optical filters alone may not provide adequate compensation.

7. The accuracy obtained depends upon the availability of reliable calibration gases. Based on the results of this study, the method produces results that average 2.5% high.

Future papers will contain test results for methods to measure other air pollutants.     

Evaluating agricultural best management practices in tile-drained subwatersheds of the Mackinaw River, Illinois

Best management practices (BMPs) are widely promoted in agricultural watersheds as a means of improving water quality and ameliorating altered hydrology. We used a paired watershed approach to evaluate whether focused outreach could increase BMP implementation rates and whether BMPs could induce watershed-scale (4000 ha) changes in nutrients, suspended sediment concentrations, or hydrology in an agricultural watershed in central Illinois. Land use was >90% row crop agriculture with extensive subsurface tile drainage. Outreach successfully increased BMP implementation rates for grassed waterways, stream buffers, and strip-tillage within the treatment watershed, which are designed to reduce surface runoff and soil erosion. No significant changes in nitrate-nitrogen (NO-N), total phosphorus (TP), dissolved reactive phosphorus, total suspended sediment (TSS), or hydrology were observed after implementation of these BMPs over 7 yr of monitoring. Annual NO-N export (39-299 Mg) in the two watersheds was equally exported during baseflow and stormflow. Mean annual TP export was similar between the watersheds (3.8 Mg) and was greater for TSS in the treatment (1626 ± 497 Mg) than in the reference (940 ± 327 Mg) watershed. Export of TP and TSS was primarily due to stormflow (>85%). Results suggest that the BMPs established during this study were not adequate to override nutrient export from subsurface drainage tiles. Conservation planning in tile-drained agricultural watersheds will require a combination of surface-water BMPs and conservation practices that intercept and retain subsurface agricultural runoff. Our study emphasizes the need to measure conservation outcomes and not just implementation rates of conservation practices.     

Seasonal microbial community shift in a saline sewage treatment plant

Activated sludge was monthly sampled from a saline sewage treatment plant of Hong Kong (China) during June 2007 to May 2008 to analyze the microbial community shift along with environmental variations using denaturing gradient gel electrophoresis of polymerase chain reaction amplified 16S rDNA fragments. Environmental changes resulted into a seasonal microbial community shift characterized by alterations in species number and abundance in the sewage treatment plant. Correspondence analysis and cluster analysis on community structure profile showed that the 12 monthly samples fell into four groups, which is in accordance with season changing in Hong Kong. Canonical correspondence analysis revealed that PO ₄ ^3t- -P and NH ₄ ⁺ -N posed more significant effects on community structure than total phosphorus and total nitrogen, respectively. Compared with sludge retention time, influent total phosphorus had an inverse effect on the community structure shift, and chemical oxygen demand and NH ₄ ⁺ -N showed a similar effects. Results of this study may contribute to the development of new knowledge involving the microbial community shift in sewage treatment plants.     

Spiked sample standards; Their uses and disadvantages in analytical quality control

Standard samples, that is matrices containing precisely known concentrations of various radionuclides, are necessary adjuncts to any analytical quality control program. In general, we prefer the use of “natural matrix standards,” samples into which the radionuclides have become incorporated under natural conditions, and over as long a time span as possible. Under some circumstances, however, real advantages are offered by “spiked sample standards” samples to which the isotope of interest has been added in a precisely known amount, at the time of preparing the standard. It is our purpose to discuss the advantages and disadvantages of spiked standards and to contrast them with those of natural matrix standards, as well as to discuss the preparation of the former class of standards and the evidence supporting our recommendation of caution in their use.In general, spiked standards offer advantages of low cost of preparation, of advance assurance that the amount and chemical form of the radioisotopes added are known, and of the possibility of preparation of unnatural matrices, or of nuclides that are to be expected but not yet to be found in nature. The most salient disadvantages of spiked standards derive from the usual uncertainty concerning the concentration of any radionuclides in the matrix before spiking and from the difficulty of insuring that there will be no difference in analytical behavior between the spike and the same isotope that has become incorporated in the matrix under natural conditions. Consideration of these advantages and disadvantages leads to identification of a list of special problems for which spiked standards may be advantageous and of a list of precautions indicated in the interpretation of the resulting data. The argument against the general applicability of spiked standards appear overwhelming.