Assessment of contaminant lability during phytoremediation of polycyclic aromatic hydrocarbon impacted soil

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant compounds, some of which are known carcinogens, often found in high residual soil concentrations at industrial sites. Recent research has confirmed that phytoremediation holds promise as a low-cost treatment method for PAH contaminated soil. In this study, the lability of soil bound PAHs in the rhizosphere was estimated using solid phase extraction resin. An extraction time of 14 days was determined to be appropriate for this study. Resin-extractable PAHs, which are assumed to be more bioavailable, decreased during plant treatments. Significant reductions in the labile concentrations of several PAH compounds occurred over 12 months of plant growth. The differences in concentration between the unplanted and the planted soil indicate that the presence of plant roots, in addition to the passage of time, contributes to reduction in the bioavailability of target PAHs.     

The influence of organic ligands on the retention of lead in soil

Organic acids are commonly produced and exuded by plant roots and soil microorganisms. Some of these organic compounds are effective chelating agents and have the potential to enhance metal mobility. The effect of citrate and salicylate on the leaching of lead in soil was investigated in a laboratory experiment. In short-term batch experiments, adsorption of lead to soil was slightly enhanced with increasing salicylate concentration (500-5000 microM) but decreased significantly in the presence of citrate. These observations suggested that citrate may enhance Pb leaching, but this was not observed in the column study. Soluble Pb in the presence and absence citrate or salicylate (up to 5000 microM) was added to soil columns at a moderate flow rate, but no Pb was observed to emerge from the soil in any of the soil columns. Rapid biodegradation of citrate in soil eliminated potential complexing ability. Breakthrough of Pb from soil was noted only when using small columns at high flow rates (>20 pore volumes per day). Under these conditions of physical and chemical non-equilibrium, citrate was not degraded and significantly enhanced Pb mobility. As in the batch adsorption experiments, the presence of salicylate reduced Pb leaching. Considering the extreme conditions required to induce Pb leaching, it is likely that Pb will remain relatively immobile in soil even in the presence of a strong complexing agent such as citrate.     

Biosolids-amended soils: Part I. Effect of biosolids application on soil quality and ecotoxicity.

Investigations of potential risk from biosolids generally indicate that land application does not threaten human or ecosystem health, but questions continue to arise concerning the environmental effects of this practice. This research project was initiated to evaluate ecotoxicity resulting from the amendment of soils with biosolids from municipal wastewater treatment plants. Toxicity was evaluated using standard tests, including earthworm mortality, growth, and reproduction; seedling germination and root elongation; microbial respiration; and nematode mortality and reproduction. Nineteen municipal wastewater treatment plants were identified to participate in an initial screening of toxicity, and five were chosen for a more detailed evaluation. In addition, two soils with historically high applications of high-metal biosolids were evaluated. Contaminants examined were zinc, copper, nickel, chromium, arsenic, cadmium, lead, and coplanar polychlorinated biphenyls (PCBs). Single applications had no effect on soil metal concentrations. Coplanar PCBs were not detectable in any of the soils or biosolids. All target organisms were sensitive to reference toxicants. Limited toxicity was observed in a small number of the amended soils, but no patterns emerged. Approximately one-half of the negative effects of biosolids on bioindicators could be attributed to routine properties, such as slight depression of pH and/or elevated salinity. None of the accumulated metal concentrations were excessive, and most would not be considered elevated. These observations suggest that current regulations for application of biosolids to soils are providing adequate ecosystem protection.     

Social identity and applicant attraction: Exploring the role of multiple levels of self

Applicant attraction is a critical objective of recruitment. Common predictor variables of applicant attraction are limited in that they do not provide a comprehensive understanding of the process that shapes the perceptions and beliefs of job applicants about the firms for which they aspire to work for. Because individuals have the inherent desire to expand and enhance their social identities (e.g., personal, relational, and collective identities), they are likely to be attracted to organizations that allow them to do so. Building on recent work on levels of self, our paper suggests that social identities mediate the relation between currently established predictor variables of applicant attraction (e.g., compensation, type of work, and organizational image) and important applicant attraction outcomes. Common predictor variables of applicant attraction can lead to the activation, evaluation, and identification processes described by social identity theory. A theoretical framework is presented that illustrates the mediating influence of social identity on the relations between common predictor variables and applicant attraction outcomes. This framework may lead to more effective recruitment strategies. Copyright © 2015 John Wiley & Sons, Ltd.     

Occurrence of the Kumamoto oyster Crassostrea sikamea in the Ariake Sea, Japan

The Kumamoto oyster Crassostrea sikamea is distinguished from the closely related Pacific oyster C. gigas by concordant differences in 16S rDNA, allozymes, and a one-way gametic incompatibility. After repeated failures to find this oyster in its native habitat, we speculated in 1994 that “the Kumamoto oyster may be extinct in Japan”. In September 1996, we sampled small, deep-cupped oysters from the Ariake Sea and typed these for 16S rDNA and ITS-1 DNA markers previously shown to be diagnostic for the three most common oysters in the Ariake Sea, C. gigas, C. sikamea and  C. ariakensis. Our earlier suggestion of the demise of  C. sikamea proved incorrect. Of the 256 oysters sampled, 181 (71%) were  C. gigas, 53 (21%) were C. sikamea, and 22 (9%) were  C. ariakensis; no interspecific hybrids were observed. The distributions of C. sikamea and  C. ariakensis are clumped in the Ariake Sea:  C. sikamea occurs on the eastern and northern shores,  C. ariakensis occurs only in the northern part. These results emphasize the value of molecular markers for discriminating these morphologically plastic species both in the field and in aquaculture. Received 6 July 1998 / Accepted 8 October 1998     

Risk vs. reward: how predators and prey respond to aging olfactory cues

Many animals use olfaction to find food and avoid predators, and must negotiate environments containing odors of varying compositions, strengths, and ages to distinguish useful cues from background noise. Temporal variation in odor cues (i.e., “freshness”) seems an obvious way that animals could distinguish cues, yet there is little experimental evidence for this phenomenon. Fresh cues provide a more reliable indicator of donor presence than aged cues, but we hypothesize that the benefits of responding to aged cues depend on whether the cue indicates the proximity of a predator or a potential meal. As prey cannot remain eternally risk averse in response to predator odor, we predict that antipredator responses should diminish as predator cues age. In contrast, animals searching for food should investigate aged prey cues if investigation costs are sufficiently low and the potential benefit (a meal) sufficiently high; thus, we predict that predators will maintain interest in aged prey cues. We tested these ideas using free-ranging rats (Rattus spp.) in two separate experiments; firstly assessing giving-up densities in the presence of predator odor, and secondly examining investigation rates of prey odors. As predicted, giving-up densities dropped once predator odor had aged, but investigation rates remained similar for aged and fresh prey odor. Thus, rats used temporal variation in odor cues to evaluate the cost–benefit relationship of responding to predator and prey odors. We suggest that the ecological significance of variable cue age needs more research and should be considered when interpreting behavioral responses to olfactory information.     

Influence of residency and social odors in interactions between competing native and alien rodents

Residency status of individuals in populations may be an important determinant of the outcomes of interspecific competition between native and introduced species. We examined direct behavioral interactions between two similarly sized rodents, the alien Rattus rattus and native Rattus fuscipes when they were respective residents and intruders in a small enclosure. Resident individuals were dominant in their behaviors toward intruders irrespective of the species that was resident. In contrast, interactive behaviors between conspecifics were often neutral or amicable, supporting suggestions that R. rattus and R. fuscipes are social animals. We then tested whether rodent species use heterospecific odors to avoid aggressive competitive interactions and partition space in the field. Neither R. fuscipes nor R. rattus responded to traps scented with the odors of male or female heterospecifics. If R. fuscipes does not recognize the odor of introduced R. rattus, then odors will not be cues to the presence or territorial space of competing heterospecifics. Rather, findings from both enclosure and field trials suggest that direct aggressive interactions between individual R. rattus and R. fuscipes probably facilitate segregation of space between these two species in wild populations, where resident animals may typically be the winners and exclude heterospecific intruders. These findings have implications for the invasion success of introduced rodents such as R. rattus into intact forests, where native populations may have competitive advantage because of their residency status.     

Differential attraction of females to dominant males: Olfactory discrimination and mating preference in the brown lemming (Lemmus trimucronatus)

Summary This study investigated differential attraction of estrous brown lemmings (Lemmus trimucronatus) to conspecific males recently exposed to each other for a 10-min agonistic encounter. In tests conducted 5 min, 1 h and 24 h after agonistic encounters, females preferred the oder of dominant males to that of defeated males when both odors were presented simultaneously in a Y-maze olfactometer. Defeat in an agonistic encounter did not reduce the propensity of male lemmings to initiate sexual behavior. In one-male, one-female tests conducted 5 min after agonistic encounters, dominant males achieved higher mount and thrust scores while defeated males obtained higher scores for attempted mounts. The sexual behavior of dominant and defeated males did not differ significantly in similar tests conducted 1 h and 24 h later. In contrast, females readily mated with dominant males and tended to avoid defeated males in two-male tethering tests conducted 5 min after agonistic encounters. In these tests, females still showed a preference for dominant males 1 h and 24 h after male agonistic encounters.     

An investigation into reservoir NOM reduction by UV photolysis and advanced oxidation processes

A comparison of four treatment technologies for reduction of natural organic matter (NOM) in a reservoir water was made. The work presented here is a laboratory based evaluation of NOM treatment by UV-C photolysis, UV/H(2)O(2), Fenton's reagent (FR) and photo-Fenton's reagent (PFR). The work investigated ways of reducing the organic load on water treatment works (WTWs) with a view to treating 'in-reservoir' or 'in-pipe' before the water reaches the WTW. The efficiency of each process in terms of NOM removal was determined by measuring UV absorbance at 254 nm (UV(254)) and dissolved organic carbon (DOC). In terms of DOC reduction PFR was the most effective (88% removal after 1 min) however there were interferences when measuring UV(254) which was reduced to a lesser extent (31% after 1 min). In the literature, pH 3 is reported to be the optimal pH for oxidation with FR but here the reduction of UV(254) and DOC was found to be insensitive to pH in the range 3-7. The treatment that was identified as the most effective in terms of NOM reduction and cost effectiveness was PFR.