Microcosm investigations of stormwater pond sediment toxicity to embryonic and larval amphibians: variation in sensitivity among species

Stormwater ponds have become common features of modern development and often represent significant amounts of open space in urbanized areas. Although stormwater ponds may provide habitat for wildlife, factors responsible for producing variation in wildlife use of ponds have received limited attention. To investigate the role of variation in species tolerances of pollutants in structuring pond-breeding amphibian assemblages, we exposed species tolerant (Bufo americanus) and not tolerant (Rana sylvatica) of urbanization to pond sediments in laboratory microcosms. Pond microcosms had elevated sediment metal levels and chloride water concentrations. Among R. sylvatica embryos, exposure to pond sediments resulted in 100% mortality. In contrast, B. americanus embryos and larvae experienced only sublethal effects (i.e., reduced size at metamorphosis) due to pond sediment exposure. Our results suggest variation in pollutant tolerance among early developmental stages of amphibians may act in concert with terrestrial habitat availability to structure amphibian assemblages associated with stormwater ponds.     

Cranial biomechanics of Diplodocus (Dinosauria, Sauropoda): testing hypotheses of feeding behaviour in an extinct megaherbivore

Sauropod dinosaurs were the largest terrestrial herbivores and pushed at the limits of vertebrate biomechanics and physiology. Sauropods exhibit high craniodental diversity in ecosystems where numerous species co-existed, leading to the hypothesis that this biodiversity is linked to niche subdivision driven by ecological specialisation. Here, we quantitatively investigate feeding behaviour hypotheses for the iconic sauropod Diplodocus. Biomechanical modelling, using finite element analysis, was used to examine the performance of the Diplodocus skull. Three feeding behaviours were modelled: muscle-driven static biting, branch stripping and bark stripping. The skull was found to be ‘over engineered’ for static biting, overall experiencing low stress with only the dentition enduring high stress. When branch stripping, the skull, similarly, is under low stress, with little appreciable difference between those models. When simulated for bark stripping, the skull experiences far greater stresses, especially in the teeth and at the jaw joint. Therefore, we refute the bark-stripping hypothesis, while the hypotheses of branch stripping and/or precision biting are both consistent with our findings, showing that branch stripping is a biomechanically plausible feeding behaviour for diplodocids. Interestingly, in all simulations, peak stress is observed in the premaxillary–maxillary ‘lateral plates’, supporting the hypothesis that these structures evolved to dissipate stress induced while feeding. These results lead us to conclude that the aberrant craniodental form of Diplodocus was adapted for food procurement rather than resisting high bite forces.     

Monitoring new forestry

Techniques to monitor growth and mortality of live trees, and longevity of snags were developed and tested on 8 units in the Oregon and Washington Cascades where new forestry (structural retention) cuttings were utilized. Time and costs were quantified. The total area of three aggregated units and five dispersed units was 27.8 ha, with 2407 trees and snags measured on 25.1 ha of sample area. Cost of field work was approximately $4590 (4 person crew at 6 weeks) while costs of data entry, analysis and report writing were approximately $2000 (250 person hours). Monitoring is an important component of adaptive management and is essential if we are to understand the ramifications of new silvicultural systems.     

Risk assessment as a management tool for inactive hazardous materials disposal sites

A protocol for risk assessment at inactive hazardous material disposal sites has been developed by using mathematical modeling and estimation techniques. Compared with ranking models, the protocol yields quantitative results with a minimum of input data that may be used to select among management, scientific, or engineering alternatives for the site. This article reviews the background, presents the protocol, illustrates the application of the protocol, and demonstrates the use of the protocol in conjunction with thecritical environmental area concept. Comparisons are also presented with other model systems such as the EPA HRS.     

Contemporary (1979-1988) and inferred historical status of headwater lakes in North Central Ontario, Canada

Fifty-six headwater Canadian Shield lakes were repetitively sampled from 1979 to 88 to determine their response to changes in acidic deposition of the period. Annual wet sulphate loadings varied between 38 and 83 meq m(-2), with highest deposition in the late 1970s followed by somewhat lower but variable deposition in the 1980s. Median pH of the lakes increased 0.42 pH units from 1979 to 1985 and decreased by 0.15 units between 1985 and 1988. Short water renewal times (x=1.1 y) promoted rapid equilibration. Since lake were so responsive to changes in SO4(2-) inputs, they were at or near steady state at all times. Comparison of predicted original pH and ANC with 1979 data indicate a median decline of 0.45 pH units and a loss of 34 microeq litre(-1). ANC. Four of 9 lakes were found to be historically fishless, based on the continued presence of Chaoborus americanus in sediment cores. The remaining five lakes historically had fish populations, but fish were not collected in 1979 when pH ranged betwen 4.6 and 5.3. By 1987, fish species were found in five of these lakes where pH had increased on average by 0.9 pH units. Our data indicate that water quality improvements could allow for the reinvasion or resumption of recruitment for a significant number of Ontario lakes.     

Food contamination as a pathway for lead exposure in children during the 2010–2013 lead poisoning epidemic in Zamfara, Nigeria

In 2010, an estimated 400 to 500 children died of acute lead poisoning associated with artisanal gold mining in Zamfara, Nigeria. Processing of gold ores containing up to 10% lead within residential compounds put residents, especially children, at the highest risk. Principal routes of exposure were incidental ingestion and inhalation of contaminated soil and dusts. Several Nigerian and international health organizations collaborated to reduce lead exposures through environmental remediation and medical treatment. The contribution of contaminated food to total lead exposure was assessed during the environmental health response. Objectives of this investigation were to assess the influence of cultural/dietary habits on lead exposure pathways and estimate the contribution of contaminated food to children's blood lead levels(BLLs). A survey of village dietary practices and staple food lead content was conducted to determine dietary composition, caloric intakes, and lead intake. Potential blood lead increments were estimated using bio-kinetic modeling techniques. Most dietary lead exposure was associated with contamination of staple cereal grains and legumes during post-harvest processing and preparation in contaminated homes. Average post-harvest and processed cereal grain lead levels were 0.32 mg/kg and 0.85 mg/kg dry weight, respectively. Age-specific food lead intake ranged from 7 to 78 μg/day. Lead ingestion and absorption were likely aggravated by the dusty environment, fasting between meals, and nutritional deficiencies. Contamination of staple cereal grains by highly bioavailable pulverized ores could account for as much as 11%–34% of children's BLLs during the epidemic, and were a continuing source after residential soil remediation until stored grain inventories were exhausted.     

Distributional analysis of regional benefits and cost of air quality control

The methodology and results of an analysis of benefits and costs of air quality control for an urban region in Florida are given. The machinery used considers the spatial distribution of (a) emission sources, (b) the ambient levels resulting from local meteorological conditions and geographic features, and (c) the socioeconomic characteristics of the impacted population groups. This facilitates an examination of the distributional aspects of costs and benefits associated with various control scenarios. With appropriate adaptation and inputs the steps in our analysis should apply to a distributional benefit/cost analyses for any region.     

EFFECTIVENESS OF TIMBER HARVEST PRACTICES FOR CONTROLLING SEDIMENT RELATED WATER QUALITY IMPACTS1

ABSTRACT: Timber harvest best management practices (BMPs) in Washington State were evaluated to determine their effectiveness at achieving water quality standards pertaining to sediment related effects. A weight‐of‐evidence approach was used to determine BMP effectiveness based on assessment of erosion with sediment delivery to streams, physical disturbance of stream channels, and aquatic habitat conditions during the first two years following harvest. Stream buffers were effective at preventing chronic sediment delivery to streams and physical disturbance of stream channels. Practices for ground‐based harvest and cable yarding in the vicinity of small streams without buffers were ineffective or only partially effective at preventing water quality impacts. The primary operational factors influencing BMP effectiveness were: the proximity of ground disturbing activities to streams; presence or absence of designated stream buffers; the use of special timber falling and yarding practices intended to minimize physical disturbance of stream channels; and timing of harvest to occur during snow cover or frozen ground conditions. Important site factors included the density of small streams at harvest sites and the steepness of inner stream valley slopes. Recommendations are given for practices that provide a high confidence of achieving water quality standards by preventing chronic sediment delivery and avoiding direct stream channel disturbance.