Spatial variability in characteristics and trace metal levels in sediments from watercourses

Assessing sediment quality requires sampling designs which address variability. Often however, only one sample or composited sample is collected at a sample site. Existing studies on sediment variability or sampling strategies primarily concern lake or marine sediments. Two rivers and one canal were sampled to assess sediment variability. Further, it was determined if sediment contamination in running water could be predicted by using visual criteria and/or knowledge of the presence of depositional and erosion areas. Metal concentrations and sediment characteristics were measured in different visually distinct areas of the river. At all sample sites the coefficient of variance was relatively high for most sediment characteristics (1.4‐ > 100%) and metal levels (15.3–63.6%). In one river the majority of sediment characteristics variation was between two sediment types and detected by visually distinct differences. Significant differences in cadmium and zinc concentrations were also detected. Contrary to what was expected, cadmium, and zinc levels were highest in the coarse fraction. No differences were found in the second river. In the canal a greater concentration of fine grained sediments and metals were found in the deep areas. It was not possible to predict sediment areas with the highest levels of metal contamination using visual criteria or knowledge of the erosion and sedimentation pattern of the river.     

Leaching of copper,chromium and arsenic in a soil of south west Victoria,Australia

The movement of copper, chromium and arsenic originating from samples of the wood preservative Tanalith® through mildly acidic, sandy loam soil was investigated. Small, undisturbed soil cores (of dimensions 15 × 15 × 15 cm) were removed from the topsoil of a paddock adjacent to the Glenelg River in the Western District of Victoria, Australia. The paddock soils were thin (<30cm) greyish brown, mildly acidic, sandy loams with a moderate organic carbon content (2–5%) overlying a limestone cap. Tanalith® was applied to the surface of the cores which were then irrigated with deionised water at approximately 30 mm day^‐1. Copper concentrations in all leachate remained at background levels throughout the experiment, and this element was found to be immobilised in the top 4 cm of the soil. Up to 29% of the applied dose of chromium was detected in the leachate, with breakthrough occurring within 20 days of Tanalith® application. Up to 13% ofthe applied dose ofarsenic was detected in the leachate, although in this case breakthrough was not observed until 25 days after Tanalith® application and leachate concentrations were still rising when the experiment came to a close. Significant concentrations of arsenic and chromium were found in the top 6 cm of the soil profile.     

Particle sorting in bivalves: in vivo determination of the pallial organs of selection

Benthic particle feeders are exposed to a food supply varying in both quantity and quality. Previous studies have shown that bivalve molluscs deal with such fluctuating particle regimes in a variety of ways, including adjustments in pumping and ingestion rates, and selective rejection of non-nutritive particles as pseudofeces. The actual site of particle selection within the pallial cavity, however, has remained a topic of speculation. During August 1995 and January and August 1996, we exposed the oysters Crassostrea virginica (Gmelin) and C. gigas (Thunberg), and the mussel Mytilus trossulus Gould to a mixture of ground, aged Spartina alterniflora Loisel and similar-sized phytoplankton at three concentrations (10³, 10⁴, 10⁵ particles ml⁻¹). We then examined the ctenidia and labial palps by means of endoscopy and sampled, in vivo, the particulate material from various ciliated tracts, and analyzed the samples with a flow cytometer. We found that in oysters, the ctenidia are responsible for particle sorting, whereas the labial palps play an accessory role in particle selection, or function to control the volume of material to be ingested. In mussels, however, the ctenidia play little role in particle selection and simply transport particulate matter to the palps for further processing. We suggest that selection by the ctenidia of oysters is a function of their architecture (plicate, heterorhabdic). Received: 4 June 1997 / Accepted: 23 January 1998     

Comparison of current Federal Reference Methods for ambient lead measurements adjacent to a secondary lead smelter

The United States Environmental Protection Agency (EPA) reduced their National Ambient Air Quality Standard (NAAQS) for lead (Pb) an order of magnitude to a concentration level of 0.15 micrograms per cubic meter (µg/m³) when the new rule was promulgated in 2008. At that time, the possibility of revising the Pb sampling method from total suspended particulate (TSP) to particulate matter less than or equal to 10 µm in diameter (PM₁₀) was considered due to potential measurement bias of the Pb-TSP monitoring technique. The New York State Department of Environmental Conservation (NYSDEC) has been operating source-orientated colocated TSP and PM₁₀ monitors documenting ambient air lead (Pb) concentrations since 2011 at a site adjacent to a secondary Pb smelter in Wallkill, New York. The colocated Wallkill data show a very strong correlation between the readings recorded by these two sampling techniques. After the range of the variability in the individual Pb-PM₁₀/Pb-TSP ratios was reduced by using a 0.005 µg/m³ concentration cut point, because of the concerns about the measurements at low concentrations, an adjustment factor (AF) of 1.49 was calculated using the remaining data set. This AF can be used to estimate Pb-TSP concentrations from Pb-PM₁₀ readings at this Wallkill source-orientated location. It was stated by the EPA that there is only a limited data set in situations where Pb-TSP and Pb-PM₁₀ are colocated, especially for those sites considered to be source-oriented, so the analyses performed and summarized herein for the Wallkill colocated airborne Pb concentration data add to that limited data set.

Implications: These data analyses add to the limited data set in situations where Pb-TSP and Pb-PM₁₀ are colocated to help refine the derivation of a site-specific adjustment factor for estimating TSP Pb concentrations from measured PM₁₀ Pb concentrations. This could assist the EPA in transitioning away from the use of the Pb-TSP monitoring technique, with its indicated measurement bias, for the Pb NAAQS to the use of Pb-PM₁₀ instead. An adjustment factor of 1.49 was calculated that could be used to estimate Pb-TSP concentrations from Pb-PM₁₀ values collected around this source-orientated location.     

Genecological variation corresponding to Forest Ecosystem Classification vegetation and soil types for jack pine and black spruce from northwestern Ontario

A preliminary study was undertaken to reveal ecotypic differentiation in jack pine and black spruce corresponding to ecological land classification groups. Seed sources of jack pine (64) and black spruce (68) from northwestern Ontario were classified according to Vegetation Types (V-Types) and Soil Types (S-Types) defined by the Forest Ecosystem Classification (FEC) developed by the Ontario Ministry of Natural Resources and Forestry Canada for northwestern Ontario. Two short-term common garden field trials and a greenhouse trial were established for each species. Significant differences were present among ecological groupings of seed sources for both species. These differences were expressed according to V-Types and S-Types based on first, second, and third year heights as well as needle flushing dates for jack pine and second year growth increments for black spruce. Rank differences among the groups based on FEC V-Types and S-Types were generally consistent for each of the two species although certain groups showed rank reversals at the two field trials. Apparently, selection pressures corresponding to different FEC V-Types and S-Types have resulted in a detectable pattern of adaptive variation for both jack pine and black spruce in northwestern Ontario. However, the management implications for these two species are uncertain since additional tests are required to verify these results.     

Sex-specific differences in site fidelity and the cost of dispersal in yellow-headed blackbirds

Male migratory birds tend to be more faithful than females to previous breeding sites, suggesting sex differences in costs or benefits of dispersal. In Illinois, greater site fidelity by male yellow-headed blackbirds (Xanthocephalus xanthocephalus) was associated with reduced reproductive success the following year for dispersers relative to non-dispersers. Dispersing females suffered no reduction in reproductive success the following year. Males that attracted few social mates, and thus had low reproductive success, were more likely to disperse, whereas females dispersed in response to low-patch reproductive success, regardless of their individual performance. Males that dispersed appeared to be successful acquiring territories because none was observed as a floater. The rate of dispersal by males in this low-density population was greater than in more dense populations where dispersing males may be less successful at acquiring territories. Despite success at obtaining territories, males that dispersed acquired territories on the periphery of wetlands where fewer females nested, resulting in lower reproductive success. In the second year after dispersing, however, males moved onto more central territories where they acquired larger harems. Thus, dispersal by males may be a long-term strategy requiring at least 2 years for benefits to be realized. Long-term success was enhanced because dispersing males moved to wetlands on which reproductive success was higher than on the wetlands they left. In addition to demonstrating that both individual and patch reproductive success affect dispersal decisions, these data indicate that when evaluating costs and benefits of dispersal, researchers should use a time frame beyond 1 year.     

Parents influence asymmetric sibling competition: experimental evidence with partially dependent young

Asymmetric sibling competition, which occurs when some siblings hatch as stronger competitors than others, is an important component of avian reproductive strategies. Here, we report two experiments on the burying beetle Nicrophorus vespilloides investigating how parents might influence the outcome of asymmetric sibling competition. In this species, as in altricial birds, different-aged offspring compete for resources provided by the parents. However, unlike altricial birds, offspring depend only partially on their parents for resources, and parents adjust the brood size directly through filial cannibalism. In the first experiment, we compared the growth and survivorship of different-aged offspring when parents could and could not influence asymmetric sibling competition. In the second experiment, we recorded behavioral interactions between different-aged offspring and parents. We found that senior offspring (early-hatched) grew faster than juniors (late-hatched) when parents were present and could influence the outcome of sibling competition, whereas seniors and juniors grew at similar rates when parents were removed. Thus, seniors benefited more than did juniors when the offspring could obtain resources by begging from the female parent. There was no difference in the survivorship of seniors and juniors. We also found that seniors and juniors spent a similar amount of time feeding from female parents, but juniors spent more time begging and were less effective at begging than seniors. Interestingly, juniors spent more time begging only as long as seniors also begged, suggesting that juniors adjusted their begging effort in response to direct competition against seniors for resources provided by parents. Our study provides novel insights into the ecological significance of asymmetric sibling competition by showing that asymmetric sibling competition took place when parents were present and offspring could obtain resources by begging. In contrast, we found no evidence of asymmetric sibling competition when parents were absent and offspring obtained resources solely by self-feeding.     

Organochlorine pesticides in elementary school yards along the Texas-Mexico border

A reconnaissance study was undertaken to determine potential contaminant exposures to children through soil from elementary school playgrounds. Soil samples were collected from areas along the Texas-Mexico border, inland areas (soils from elementary school yards in cities/towns within the state of Texas), and three National Parks (one on the border, one in Tennessee, and one in Washington). The present study focused on organochlorine (OC) pesticides as the potential contaminants of concern because of their historical (and possibly current) use, and their importance as persistent organic pollutants (POPs). DDE and heptachlor were the most frequently detected OCs (69 and 63%, respectively), although heptachlor concentrations in soil never exceeded 5 ppb. Relatively higher concentrations of DDE were observed in agricultural areas along the border (50-60 ppb in soils from McAllen, Palmview, and San Benito) than in other soils. However, a school yard in Lubbock, TX had the highest OC concentration observed (70 ppb dieldrin). These results may be due to historical agriculture activity prior to the banning of OC pesticides such as DDT in the early 1970s, as well as the more recent use of DDT in Central and South America for malaria control.     

Temporal variation of metals in the seagrass Posidonia australis and its potential as a sentinel accumulator near a lead smelter

Temporal variation in the concentrations of Cd, Cu, Mn, Ni, Pb and Zn in leaves of the seagrass Posidonia australis was studied at three sites near a lead smelter on the shore of Spencer Gulf, a large hypersaline marine embayment in South Australia, on four occasions from October 1980 to September 1981. Concentrations of Cd, Mn, Pb and Zn of up to 541, 537, 379 and 4241 g g^-1, respectively, were found in leaves collected from the site nearest to the smelter. A substantial temporal variation in the concentrations of these metals in samples from all sites resulted from the combined effect of leaf age and collection strategy. Concentrations of Cd, Cu and Zn in the leaf epibiota were lower than those in the leaves, but the reverse was true for Mn and Ni. The use of seagrass leaves as sentinel accumulators for Cd, Pb and Zn must be based on collections made at the same time of year, or otherwise account for the effect of leaf age on concentrations of the metals in the samples.