The Wahlund effect and the geographical scale of variation in the intertidal limpet Siphonaria sp.

Samples of Siphonaria sp. were collected between 1978 and 1982 from sites covering its known geographic range, from Kalbarri, Western Australia to Port Robe, South Australia. Geographic variation of 7 polymorphic enzymes was examined in this intertidal pulmonate limpet, and was found to be consistently small, indicating a large-scale influence of gene flow due to planktonic dispersal. Despite this large-scale uniformity, there is fine-scale genetic patchiness, which is repeated, rather than accumulated, on the larger scale. Throughout its geographic range, Siphonaria sp. shows deficits of heterozygotes for all 7 loci. The consistency among loci indicates that the causes of the deficits are populational, rather than locus-specific. A Wahlund effect, the departure from Hardy-Weinberg equilibrium due to mixing of individuals from groups with different allelic frequencies, is the simplest explanation of such deficits. The limited geographic variation of allelic frequencies, however, is grossly inadequate to produce these deficits through a Wahlund effect. Similarly, temporal variation in allelic frequencies in recruits does not explain the deficits. The largest contributor to a Wahlund effect appears to be binomial sampling variance among small local breeding groups. Thus, mixing of larvae on a scale of metres, rather than among geographical areas, apparently produces the deficits of heterozygotes.     

Urinary arsenic concentrations and speciation in Cornwall residents

Inorganic arsenic and its methylated metabolites were determined in urine from adults and children in Cornwall and from corresponding control groups in Glasgow. In the mineralised south-west of England, where it has been suggested that the highly enriched soil arsenic concentrations may at least be a cofactor in the increased incidence of skin cancer, urinary arsenic levels were, in general, only slightly elevated. The potential for increased intake of inorganic arsenic in Cornwall was, however, reflected in the more frequent occurrence of trivalent inorganic arsenic and monomethylarsonic acid in urine and, of especial significance, in two comparatively highly elevated sum of arsenic species concentrations of 48.7 and 20.8 g g^–1 creatinine recorded for two pre-school children. These findings are discussed with reference to recommended limits and pathways of exposure to inorganic arsenic.     

Environmental auditing at the crossroads: The environmental auditing roundtable's response to ISO 14000

The Environmental Auditing Roundtable (EAR) is the single largest professional organization in the world, representing over 900 members. Built on a tradition of promoting environmental auditing through openly sharing experiences in the field of safety, health, and environmental auditing, the organization in recent years has significantly expanded its influence on auditing practices both nationally and internationally by monitoring audit activities and participating in the development of audit policy, regulation, standardization, and the certification of environmental auditors. This article describes the origin and evolution of the organization from meeting the needs of the membership to addressing the needs of external national and international stakeholders.     

ESTIMATING DRAINAGE AREA ON STEEP UNIFORM SLOPES1

ABSTRACT: A study was conducted to derive a simple procedure for estimating the tributary drainage area that may potentially develop at the base of a uniformly graded, steep slope. Data were extracted from a nil development flume study in which 112 rills and their tributary drainage areas were documented. The tributary drainage area for each rill was correlated to the slope length and the slope gradient. The findings are considered applicable to planar, convex, and divergent slopes with lengths of up to 130 m. Field verification is needed to extend the applicability of the relation.     

MONITORING OPERATIONS PERFORMANCE IN LARGE-SCALE PUBLIC IRRIGATION SYSTEMS IN INDONESIA1

ABSTRACT: Different allocation and delivery performance ratios are used to assess operations performance in a large scale public irrigation system in Indonesia. Results from this analysis indicate that field management practices deviate substantially from the official operating procedures. The lack of application of a single, standardized procedure for planning water allocations represents a serious constraint to effective monitoring and evaluating system performance. Underestimated and unrealistic planned allocations becomes the justification for overdiversion of water, and has the effect of undermining the resolve of managers to see to it that actual flows meet planned flows. Miscalculating planned allocations, poor matches between planned flows and actual deliveries, overdiversion and misreporting have economic consequences as well. For example, strict adherence to the standard operating rule during the second dry season of 1987 would have resulted in 19,070,000 m³ less water diverted into the irrigation system from the Brantas River or, at a conservative estimate of $1.78 per 100 m³ water, a savings of $339,500. Scope exists for making improvements in management by closer adherence to the standard delivery rule, which will also facilitate proper monitoring and evaluation.     

On-site remediation of PCB contamination using transportable incineration systems

Many Superfund or hazardous waste sites prove to be excellent candidates for remediation using transportable incineration. Transportable incineration has been selected as the alternative of choice to remediate numerous sites throughout the United States. There are a number of firms that provide mobile and transportable incineration equipment and services. A variety of treatment systems are available, including rotary kilns, fluidized beds, and infrared incinerators. Roy F. Weston, Inc., has been instrumental in the development, design, permitting, construction, performance testing, and operation of hazardous and toxic waste thermal treatment systems. Weston owns and operates two high-temperature transportable incineration systems (TISs). The first system is Weston's seven-ton-per-hour (tph) TIS-5. The second is the TIS-20, with a design capacity of up to 30 tph. These units are typical rotary kiln incinerators, the most flexible, adaptable type of incineration unit. This article discusses Weston's use of these incinerators to remediate soils at sites contaminated with polychlorinated biphenyls (PCBs).     

A COMPARISON OF TWO METHODS FOR MULTIOBJECTIVE OPTIMIZATION FOR RESERVOIR OPERATION1

ABSTRACT: Two major objectives in operating the multireservoir system of the Upper Colorado River basin are maximization of hydroelectric power production and maximization of the reliability of annual water supply. These two objectives conflict. Optimal operation of the reservoir system to achieve both is unattainable. This paper seeks the best compromise solution for an aggregated reservoir as a surrogate of the multireservoir system by using two methods: the constraint method and the method of combined stochastic and deterministic modeling. Both methods are used to derive the stationary optimal operating policy for the aggregated reservoir by using stochastic dynamic programming but with different objective functions and minimum monthly release constraints. The resulting operating policies are then used in simulated operation of the reservoir with historical inflow records to evaluate their relative effectiveness. The results show that the policy obtained from the combination method would yield more hydropower production and higher reliability of annual water supply than that from the constraint-method policy.     

DEFINING REGIONAL POPULATIONS OF LAKES FOR THE ASSESSMENT OF SURFACE WATER QUALITY1

ABSTRACT: Topographic maps are commonly used to define populations of lakes in regional surveys of surface water quality. To illustrate the effect of different maps on that process, we compared the lakes represented on the 1:250,000-scale maps used for the Northeast Region of the Eastern Lake Survey—Phase I (ELS-I) to the lakes on a sample of large-scale maps (1:24,000 or 1:62,500). Lake areas at or near the lower limit of representation delimited “smallest-lake” values for the compared 1:250,000-scale maps. The regional median for these values was 4.5 hectares (ha) and ranged from 0.6 to 24.8 ha. Lake representation is influenced by cartographic limitations such as map scale, age, and complexity as well as the inherent variability of waterbodies (e.g., water level fluctuations or the creation of reservoirs, beaver impoundments, and oxbows). The total number of lakes on large-scale maps increased markedly as lake area decreased. Approximately 15,700 of the estimated 29,000 lakes in the EPA's Northeast Region were 1 to 4 ha in area. Because maps affect the size distribution of lakes included in a regional survey and because lake areas are thought to modify lake chemistry, maps ultimately affect the estimates of regional surface water quality.     

Ecological Benefits of Riparian Reforestation in Urban Watersheds: Study Design and Preliminary Results

Riparian forest restoration has become a major focus of watershed initiatives to improve degraded stream ecosystems. In urban watersheds, however, the ability of riparian forests to improve stream ecosystems may be diminished due to widespread, upland disturbance. This paper presents the methodology and some preliminary results from the first year of fieldwork on a 3-year project designed to assess the ecological benefits of riparian reforestation in urban watersheds. The study is based on an integrated, multidisciplinary sampling of physical, chemical, and biological attributes at forested and non-forested sections of 12 streams with different amounts of urban developement within their watersheds. Restored sections of three streams are also being monitored over the 3-year duration of the project. Sampling and analysis will continue through December 2000.