Factors controlling lead bioavailability in the Butte mining district,Montana, USA

Microprobe analyses of 38 soil and 5 mine-waste samples from Butte, Montana, demonstrated that the samples contain predominantly sulphide/sulphate and oxide/phosphates of lead (Pb)-bearing phases associated with mine waste. The sulphide/sulphate assemblage consists primarily of galena altering to anglesite and plumbojarosite, with secondary jarosite precipitating and rinding the Pb-bearing minerals. In addition, galena was encapsulated within pyrite or quartz grains. The oxide/phosphate assemblage consists of pH-neutral soils in which a plausible paragenetic sequence of PbO to Pb phosphates, PbMnO, or PbFeO is proposed, dependent on the activity of P, Mn, Fe, and Cl in the soil. In addition, Pb-bearing grains are occasionally armoured by the presence of a 1- to 3-(m rind of authigenic silicate. The low solubility of the Pb-bearing minerals resulting from encapsulation in non-Pb-bearing reaction rinds may provide an explanation for the limited Pb bioavailability observed when Butte soils were fed to rats (Freemanet al., 1992). Further evidence of the lack of absorption of lead from these soils is provided by the results of a blood-Pb study indicating very low blood-Pb levels in Butte children. The lower bioavailability of Pb from mining sites, compared to smelting and urban environments, is also due to kinetic limitations that control dissolution rates of Pb-bearing solids relative to the residence time of soil in the gastrointestinal (Gl) tract. When the test soil was fed to New Zealand White rabbits, only 9% of the total Pb was solubilised in the stomach, and therefore available for absorption. Anin vitro assay, developed to estimate maximum available Pb from soil, demonstrates that ingestion of mine-waste-bearing soil results in limited Pb dissolution, and produces results similar to thein vivo testing.     

液相/质谱(LC/MS)技术用于有机磷农药分析

液质联用技术的飞速发展 ,业已成为在各种基质中微量极性农药的常规检测方法 .与现有的分析方法相比 ,如气质联用技术和液相 紫外检测技术 ,液质联用技术简化了样品净化过程 ,最终缩短了样品分析和方法开发的时间周期 (ＥｌｂｅｒｔＨｏｇｅｎｄｏｏｒｎａｎｄＰｅｉｔｖａｎＺｏｏｎｅｎ、ＪｏｕｒｎａｌｏｆＣｈｒｏｍａｔｏｇｒａｐｈｙＡ ,2 0 0 0 ,892∶3 5— 45 3 ) .由于现有的气相分析方法需要汽化而使某些热不稳定性农药在进样过程中产生热分解 ,从而降低了分析结果的质量 ,然而带有电喷雾离子源的液质联用技术可以直接分析此类化…     

Coefficient of variation of sea surface temperature (SST) as an indicator of coral bleaching

Coral bleaching has become a major problem on reefs around the world in recent decades. It is believed that mean temperature alone is the primary force driving this ecological phenomenon. We propose that variance in temperature in the short term is just as important as the mean. Thirty years of daily sea surface temperature (SST) data have been collected by the University of Puerto Rico at Mayaguez Marine Laboratory in La Parguera, PR. These data were collated and analyzed initially (by Amos Winter) for their relationship to coral bleaching in this area. We found that the data fell into three categories: high mean temperatures associated with severe bleaching, cooler mean temperatures associated with no bleaching, and years of high SSTs but with no coral bleaching. Here, we examined the relationship between mean temperature during those months in which bleaching occurred, temperature variance (as measured by standard deviation), and coefficient of variation (CV; i.e., SD standardized by the mean). We also derived a critical threshold temperature and level of resolution in time for calculating these statistics to clearly describe the circumstances of bleaching versus non-bleaching events, particularly at marginal bleaching temperatures. These characteristics were compared for the four warmest months of the year (July–October) for four warm bleaching years (1969, 1987, 1990, and 1995), four cool non-bleaching years (1984, 1985, 1986, and 1988), and two warm non-bleaching years (1994 and 2000). No relationship was found between the mean SST and SD in terms of predicting bleaching. The two primary statistics which, in concert, did indicate bleaching, however, were the short-term, biweekly mean temperature and its the associated CV. Bleaching occurs in association with both high temperatures and a high CV. The CV becomes a critical determinant of bleaching only when temperatures are ∼29.1–29.8°C. The warm, non-bleaching years were generally characterized by a CV of < 1.9 and a temperature range between 28.5 and 29.9°C. We conclude that increased mean SSTs alone are not sufficient to induce coral bleaching; a high variance in SST at marginal, lower bleaching temperatures can induce bleaching, and likewise, a low variance of such will not induce bleaching. This variance is most clearly described by the CV.     

Estimating the abundance of mouse populations of known size: promises and pitfalls of new methods.

Knowledge of animal abundance is fundamental to many ecological studies. Frequently, researchers cannot determine true abundance, and so must estimate it using a method such as mark-recapture or distance sampling. Recent advances in abundance estimation allow one to model heterogeneity with individual covariates or mixture distributions and to derive multimodel abundance estimators that explicitly address uncertainty about which model parameterization best represents truth. Further, it is possible to borrow information on detection probability across several populations when data are sparse. While promising, these methods have not been evaluated using mark-recapture data from populations of known abundance, and thus far have largely been overlooked by ecologists. In this paper, we explored the utility of newly developed mark-recapture methods for estimating the abundance of 12 captive populations of wild house mice (Mus musculus). We found that mark-recapture methods employing individual covariates yielded satisfactory abundance estimates for most populations. In contrast, model sets with heterogeneity formulations consisting solely of mixture distributions did not perform well for several of the populations. We show through simulation that a higher number of trapping occasions would have been necessary to achieve good estimator performance in this case. Finally, we show that simultaneous analysis of data from low abundance populations can yield viable abundance estimates.     

Marine reserve design: optimal size, habitats, species affinities, diversity, and ocean microclimate.

The design of marine reserves is complex and fraught with uncertainty. However, protection of critical habitat is of paramount importance for reserve design. We present a case study as an example of a reserve design based on fine-scale habitats, the affinities of exploited species to these habitats, adult mobility, and the physical forcing affecting the dynamics of the habitats. These factors and their interaction are integrated in an algorithm that determines the optimal size and location of a marine reserve for a set of 20 exploited species within five different habitats inside a large kelp forest in southern California. The result is a reserve that encompasses approximately 42% of the kelp forest. Our approach differs fundamentally from many other marine reserve siting methods in which goals of area, diversity, or biomass are targeted a priori. Rather, our method was developed to determine how large a reserve must be within a specific area to protect a self-sustaining assemblage of exploited species. The algorithm is applicable across different ecosystems, spatial scales, and for any number of species. The result is a reserve in which habitat value is optimized for a predetermined set of exploited species against the area left open to exploitation. The importance of fine-scale habitat definitions for the exploited species off La Jolla is exemplified by the spatial pattern of habitats and the stability of these habitats within the kelp forest, both of which appear to be determined by ocean microclimate.     

Sperm transfer and storage in relation to sperm competition in Callosobruchus maculatus

This paper examines the underlying mechanisms of sperm competition in the beetle Callosobruchus maculatus (F.) (Coleoptera: Bruchidae). Recently developed mathematical models of sperm competition are combined with an empirical investigation of the processes of sperm transfer and storage. During a single insemination virgin males transfer approximately 46000 sperm, 85% more sperm than females can effectively store in their spermathecae. Many of these sperm remain in the bursa copulatrix where they are apparently rapidly degraded and can therefore play no role in fertilization. The spermatheca (primary site of sperm storage) is filled by a single insemination and sperm are lost from this organ at a constant rate. This rate of sperm loss from the spermatheca is insufficient for sperm mixing (without displacement) or sperm stratification to account for the degree of last male sperm precedence measured as P ₂; the proportion of offspring fathered by the second male to mate reported for this species (P ₂ = 0.83, when two inseminations are separated by 24 h). Models of sperm displacement correctly predict high levels of sperm precedence although the precision of these predictions is limited because the proportion of sperm entering the spermatheca cannot be accurately determined. The results suggested that last male sperm precedence in C. maculatus the result of sperm displacement, although the exact mechanism of displacement (sperm-for-sperm or fluid displacement) remains unknown. Possible constraints imposed by female genital anatomy on sperm displacement are discussed.     

Crustal evolution in the silicate planets

This paper reviews recent discoveries from space missions to the Moon, Mercury, Mars, and Venus, and their implications for planetary development. It appears that all these planets have undergone similar sequences of crustal evolution, the chief difference among them being how far each has evolved. All have apparently undergone a first differentiation in which a global crust was formed. This crust was partly disrupted by heavy impact bombardment some 4·10⁹ years ago. A second differentiation, resulting in basalt eruptions, followed. The Moon and Mercury essentially stopped evolving at this point; Mars and Venus continued to a stage of incipient plate tectonics, with crustal fracturing and vulcanism. Terrestrial Precambrian geologic evidence is consistent with a similar but further-advanced evolutionary sequence for the Earth as well, and the theory is proposed that terrestrial continents are the greatly altered and redifferentiated remnants of an originally global igneous crust of intermediate composition. The ocean basins of today are the multi-cyle descendants of mare-like basins localized by a late heavy bombardment about 4·10⁹ years ago analogous to that which formed the lunar mare basins and similar basins on other planets.     

PREP-PAC: a nutrient replenishment product designed for smallholders in western Kenya

Continuous cropping in the absence of external nutrient inputs to soils has led to the expression of poorly productive patches in farmers’ fields of western Kenya. Farmers attempting to correct these conditions are often confused by the spatial and symptomatic irregularity of affected plants and, until recently, no soil management product was commercially available that is specifically formulated to restore soil fertility to these patches. PREP-PAC consists of 2.0 kg of Minjingu rock phosphate (RP), 200 g of urea, seeds of various symbiotic nitrogen-fixing food legumes, rhizobial inoculant, gum arabic seed adhesive, lime for seed pelleting, and instructions for the use of these materials. It is intended for addition to 25 m² and produced at a cost of $ 0.56 per unit. The general principle is to apply slowly available RP sufficient for several cropping seasons with readily available nitrogenous fertilizer and to intercrop farmer’s maize (Zea mays) with a legume that provides residual fixed-nitrogen and organic inputs to the soil. This approach was tested in on-farm experiments conducted in collaboration with several grassroots rural development organizations. An experiment examined interactions between PREP-PAC components in a maize–soybean (Glycine max) intercrop in nutrient-depleted soils with sandy and clayey surface horizons. The treatments included ±RP, ±urea, and ±inoculants arranged as a 2³ factorial with four replicates at each location. Total value of the intercrops ranged between $ 0.83 in the unamended plots and $ 2.44 in plots treated with PREP-PAC. Significant positive effects were observed with the addition of RP (P<0.001), urea (P=0.04), and inoculant (P=0.01) and in interactions between RP and urea (P=0.02) or inoculant (P=0.07). The return ratio to PREP-PAC investment was 2.6 in the sandy soil and 3.7 in the clay. PREP-PACs were tested on-farm in 52 symptomatic patches containing maize–bean intercrops with and without an improved variety of climbing Phaseolus vulgaris cv. Flora. Unamended patches (25 m²=0.0025 ha) produced 1.6 kg maize and 0.08 kg bean. With addition of PREP-PAC containing Flora, yields increased to 4.1 kg maize and 1.1 kg bean (P<0.001 for both crops). Improvement in bean yield during the first cropping season nearly offset PREP-PAC’s investment costs. PREP-PAC is a strategic approach because all of its ingredients, except for urea, originate from East Africa, and are relatively inexpensive; the product is intended for distribution through existing retail and development networks.