An experimental design to probe the interactions of dissolved organic matter and xenobiotics: bioavailability of pyrene and 2,2',5,5'-tetrachlorobiphenyl to Daphnia magna

Experiments were conducted to probe the interactions between natural dissolved organic matter (DOM) and two xenobiotics, and to determine how DOM influences their bioavailability. The experimental set-up, using dialysis bags, was designed to expose test organisms to the same constant concentration of free dissolved chemical, while increasing the concentration of the bound-to-DOM fraction. Daphnia magna S. were exposed to pyrene or 2,2',5,5'-tetrachlorobiphenyl in the presence of 0, 1, 2, 5, 10 or 20 mg L(-1) of a reference riverine humic acid (Suwannee River Humic Acid). The physico-chemical parameters were well constrained in the microcosm, demonstrating its potential usefulness. However bioaccumulation by D. magna showed important variability between replicate treatments, sufficient to mask any trends as a function of DOM concentration. The organic-carbon-normalised partition coefficients (K(OC)) ranged from 52000 to 92000 L kg(-1) for pyrene and from 8200 to 89000 L kg(-1) for 2,2',5,5'-tetrachlorobiphenyl, with a marked "concentration effect" for the latter compound.     

The association between enforcement and seat belt use

A statistical association is found between the number of traffic citations for belt law violations versus observed belt use. Also, belt use is higher in primary enforcement states where officers issue such citations for belt law violations alone. In secondary enforcement states officers issue such citations only after stopping motorists for another reason. Most belt laws provide for secondary enforcement. Enforcement data were confined to the highway patrol in each state (local arrest data are rarely compiled statewide). Belt use data were based on observational surveys conducted in each belt law state.     

SPATIAL AND TEMPORAL DYNAMICS OF WOOD IN HEADWATER STREAMS OF THE PACIFIC NORTHWEST1

This paper synthesizes information on the spatial and temporal dynamics of wood in small streams in the Pacific Northwest region of North America. The literature on this topic is somewhat confused due to a lack of an accepted definition of what constitutes “small” streams and what is the relative size of woody debris contained within the channel. This paper presents a matrix that defines woody debris relative to channel size and then discusses the components of a wood budget. Headwater streams are in close proximity to wood sources and, in steeplands, are often tightly constrained by steep hillslopes. Special consideration is given to ecosystem characteristics and to management practices that affect the wood dynamics in this context. Knowledge gaps and uncertainties that can be used to guide future research are identified. Very little is currently known about the role of mass wasting in wood recruitment and storage relative to other processes, such as bank erosion and mortality, in larger streams. Further, very little work has addressed the relative importance of different wood depletion processes, especially those associated with wood transport. The effect of other ecosystem variables on wood dynamics locally across a watershed (from valley bottom to mountaintop) and regionally across the landscape (from maritime to continental climates) is not addressed. Finally, the scientific community has only begun to deal with the effects of management practices on wood quantity, structure, and movement in small streams.     

THREE‐DIMENSIONAL KRIGING ANALYSIS OF SEDIMENT MERCURY DISTRIBUTION: A CASE STUDY1

ABSTRACT: This study presents an application of a three‐dimensional kriging technique to estimate spatial distribution of total mercury (Hg) in the Cedar‐Ortega Rivers watershed located in the lower St. Johns River basin, Florida. The kriging procedures, including preliminary data analysis, structural data analysis and the log kriging estimation, are presented. Results show watershed wide Hg contamination of river sediment to a depth of 1.0 m. A three‐dimensional plot of Hg against the Florida Sediment Assessment Guidelines (i.e., the probable effect level or PEL) demonstrates that the Cedar River is more contaminated with Hg than the rest of the watershed. The maximum sediment depth with Hg concentrations above PEL value (0.696 mg/kg) is 1.5 m. Hg concentrations at or above this level could pose a significant hazard to aquatic organisms. Analysis of the spatial distribution of Hg in the watershed finds multiple input sources. This study suggests that there is a need to identify the major sources of Hg in the watershed, and to determine the pathways that allow Hg to enter the river.     

Inter-Laboratory Comparison of Air Particulate Monitoring Data

ABSTRACT

This paper compares three analytical methods that are often used to analyze composition of atmospheric aerosol: Ion Chromatography (IC), Proton Induced X-ray Emission (PIXE), and X-Ray Fluorescence (XRF). Three monitoring studies are discussed: (1) a comparison of air particulate data collected by several independent sampler/ analytical technique suites run by different laboratories; (2) a study involving two identical samplers and a single suite of analytical techniques; and (3) analysis of identical aerosol samples by two different techniques (XRF vs. PIXE). While the XRF versus PIXE project shows a very good agreement for most elements, the first interlaboratory study demonstrates the “real-life” noise introduced into the final data set by various sampling complications and different collection characteristics of the samplers used. The XRF versus PIXE study also revealed an unexplained deviation in measured sulphur concentrations for very lightly loaded samples. In the five-sampler comparison, two data sets provided by IC were approximately 20% lower than the three data sets obtained by PIXE and XRF. When two identical IMPROVE-compat-ible samplers were used and samples were subjected to similar procedures and the same analytical techniques, the variability between the two air concentration data sets significantly decreased.     

The occurrence and effects of Mytilicola intestinalis in Mytilus edulis

Mytilicola intestinalis was observed in the mussel Mytilus edulis in increasing numbers for the first time at Brighton (England), in October 1966; the populations here and at Whitstable were examined. Mussels exposed high in the littoral zone were less heavily infected than those lower down, the degree of infection being directly related to the duration of exposure in each tidal cycle. Silt in the intestine of the mussel is considered to act as a controlling factor in numbers of parasites present at Whitstable. Egg-bearing copepods were present in samples throughout the year, suggesting that breeding is not interrupted by the winter. Evidence indicates that juvenile stages of the parasite cause most damage to the host, due in part to their presence in the ramifications of the hepatopancreas. Recovery of the mussel from the effects of parasitation is rapid, following a reduction in parasite population density and number of juveniles. In the laboratory, M. edulis is more rapidly affected by lack of food at 10 °C than M. intestinalis. No dead parasites were seen during 4 months of laboratory storage. Juvenile parasites continned to mature, indicating that this period of time may be required for Mytilicola intestinalis to reach maturity at 10°C.     

What Makes Them Pay? Values of Volunteer Tourists Working for Sea Turtle Conservation

As charismatic mega-fauna, sea turtles attract many volunteers to conservation programs. This article examines the ways in which volunteers value sea turtles, in the specific context of volunteers working with the Caribbean Conservation Corporation, at Tortuguero, Costa Rica. The complexity of volunteer values is explored using a qualitative approach. In-depth interviews with 31 volunteers were conducted in July of 1999 and 2000. Interviews probed, among other things, interest in sea turtles and their conservation, motives for participating, and the most gratifying parts of their volunteer experience. Results show that volunteers hold multiple and complex values for sea turtles, but particular values dominate. Results have implications for understanding human–environment relations and the emerging study of volunteer tourism. There are also management implications for volunteer programs hoping to attract participants.     

城市土壤中重金属元素的积累及其微生物效应

与农村土壤相比,阿伯丁市城市土壤(路边土、公园土)的微生物特征发生了显著的改变,微生物基底呼吸作用明显增强,但微生物生物量却显著降低,微生物生理生态参数C_mic/C_org、q_co2值明显升高,Biolog数据显示城市土壤对能源碳的消耗量和速度显著升高.对重金属元素研究表明,与农村土相比城市土壤中重金属Pb、Zn、Cu、Ni已经有明显积累,化学形态研究表明Pb主要与氧化铁有关,Ni、Zn以残渣态为主,Cd以有效态为主,而Cu除有效态外,其它结合形态基本具有同等重要的意义.主成分分析表明,有效态Pb是控制城市土壤与农村土壤微生物特征差异的主要因素,其次为Zn,Cu和Ni的有效态和有机态亦有一定的作用效应.