Seasonal exports of phosphorus from intensively fertilised nested grassland catchments

We carried out a one year (2002) study of phosphorus (P) loss from soil to water in three nested grassland catchments with known P input in chemical fertilizer and animal liquid slurry applications. Chemical fertilizer was applied to the grasslands between March and September and animal slurry was applied over the twelve months. The annual chemical P fertilizer applications for the 17 and 211 ha catchments were 16.4 and 23.7 kg P/ha respectively and the annual slurry applications were 10.7 and 14.0 kg P/ha, respectively. The annual total phosphorus (TP) export in stream-flow was 2.61, 2.48 and 1.61 kg P/ha for the 17, 211 and 1524 ha catchments, respectively, compared with a maximum permissible (by regulation) annual export of ca. 0.35 kg P/ha. The export rate (ratio of P export to P in land applications) was 9.6% and 6.6% from the 17 and 211 ha catchments, respectively. On average, 70% of stream flow and 85% of the P export occurred during the five wet months (October to February) indicating that when precipitation is much greater than evaporation, the hydrological conditions are most favourable for P export. However the soil quality and land use history may vary the results. Particulate P made up 22%, 43% and 37% of the TP export at the 17, 211 and 1524 ha catchment areas, respectively. As the chemical fertilizer was spread during the grass growth months (March to September), it has less immediate impact on stream water quality than the slurry applications. We also show that as the catchment scale increases, the P concentrations and P export decrease, confirming dilution due to increasing rural catchment size. In the longer term, the excess P from fertilizer maintains high soil P levels, an antecedent condition favourable to P loss from soil to water. This study confirms the significant negative water quality impact of excess P applications, particularly liquid animal slurry applications in wet winter months. The findings suggest that restricted P application in wet months can largely reduce the P losses from soil to water.     

Transport of Sewage Sludge From the 106-Mile Site - Results From an October Survey

Approximately 8 million tons of sewage sludge were disposed of annually at the 106-Mile Deepwater Municipal Sludge Dump Site (106-Mile Site) between 1987 and 1990. Beginning in 1988 and continuing to the present, the focus of monitoring at the 106-Mile Site moved towards improved understanding of the fate of the sludge. A survey conducted in October 1989 was designed to (1) detect the presence of any sludge particles that settle rapidly following disposal, (2) determine if sludge could be detected in the surface waters at locations away from the immediate disposal site, and (3) determine if water quality was degraded, by assessing whether the Environmental Protection Agency's marine water quality criteria were being exceeded.

The survey showed that the sludge does have a rapidly settling component composed of organic floc. mineral grains, and other heavy, gritlike particles, all of which are relatively large. These particles may settle at rates of between 8 and 180 m h^-1 and may reach the sea floor within 1 to 13 days following disposal. Even though a rapidly settling component is present in the sludge, a significant fraction of the sludge was detectable in the form of intact sludge plumes in the upper 35 m of the water column at least 15 km from the Site. in addition, unique tracers of sludge such as xylem tracheids and Clostridium perfringens plus elevated total suspended solids and trace metals concentrations, were found at locations up to 40 km from the Site. the presence of these tracers correspond with in situ transmissometry data suggesting that a fraction of the sludge was remaining in the near-surface waters above the seasonal pycnocline. Concentrations of metals were below EPA chronic marine water quality criteria, which indicates that the water quality downstream of the Site was not impaired. the detection of sludge downstream of the 106-Mile Site is consistent with the southwestward movement of the surface water mass during the survey, as recorded by satellite-tracked surface drifters and current vectors derived from a current meter moored at 100-m depth immediately west of the Site. Near-surface transport was generally towards the southwest at a speed of approximately 22 cm s^-1*.     

SOME SIMPLE MODELS FOR CONTINUOUS VARIATE TIME SERIES1

ABSTRACT: A survey is given of recently developed models for continuous variate non–Gaussian time series. The emphasis is on marginally specific models with given correlation structure. Exponential, Gamma, Weibull, Laplace, Beta and Mixed Exponential models are considered for the marginal distributions of the stationary time series. Most of the models are random coefficient, additive linear models. Some discussion of the meaning of autoregression and linearity is given, as well as suggestions for higher–order linear residual analysis for non–Gaussian models.     

Corallum morphology and composition of crustacean cryptofauna of the hermatypic coralMadracis mirabilis

The motile crustacean cryptofauna of the hermatypic coralMadracis mirabilis (Duchassaing and Michelotti) was examined from three sites on reefs along the west coast of Barbados in 1985. In addition to site differences in degree of eutrophication, two distinct with-in-corallum habitats were recognized, based on differences in the growth form of the coral host. One form grows in isolated, hemispherical heads, with short, robust, widely separated branches covered by 50 to 80% live tissue. The second form occurs within large continuous beds of long, thin, tightly spaced branches tipped by 20 to 30% live tissue. Coral habitats consisting of small isolated heads support a crustacean fauna of high decapod and amphipod diversity, with numerous rare and site endemic species and an abundance of relatively large decapods and amphipods. The continuous beds favour a community of lower decapod and amphipod diversity, fewer rare and site endemic species and with an abundance of smaller sized isopods and copepods. It is suggested that spatial separation of branches and colonies as well as food availability associated with corallum morphology are factors influencing the variation in species abundance and faunal composition of the two habitats.     

An economist's remarks on landscaping

These costs and benefits may be more easily noticed or precisely defined by different persons. Some are seen by the landscape architect but not by the economist, and the other way round. This implies that a reasonably adequate enumeration of the benefits and costs, each considered in a very wide sense, can be achieved only if a proposal is viewed from the standpoints of different disciplines.

It may very well be that the mere enumeration of these costs and benefits will either convince the economist that the proposed scheme is ‘on’ or convince the landscape architect that it is ‘off’. In the latter case the landscape architect may say that while it would be wonderful to proceed with the scheme he can see that it would, in the wide ‘opportunity’ sense of the phrase, cost too much. But there may come a stage where the enumeration of costs and benefits leaves the landscape man wanting Scheme A and the social scientist wanting Scheme B. It is here that, first of all, adjustment must be tried. But if it fails then compromise may be needed, in which one side or the other, or both, reluctantly sacrifices some feature of his favoured scheme. If agreement cannot be reached, then the difference of opinion ought to be put to the client, who can reach his own decision.     

A multi-hazard history of Antigua*

Antigua experiences earthquakes, droughts and hurricanes. To isolate for study each of these as they occur, would be to over simplify the inter-relationships between the aftereffects of one and the occurrence and the effects of the next. Moreover, there will be conditions arising from factors outside the natural disaster spectrum which bear upon, and are themselves affected by, all of these phenomena. This interplay of events and conditions is readily illustrated in the case of island countries, which have a natural and clearly defined containment. Such interrelationships suggest a complex human-ecological system which must be recognized if environmental balance and compatability are to be maintained - particularly in respect of hazards. This documentary analysis of the colonial era in Antigua, has to conclude for the time being with questions concerning the environmental effectiveness of imported systems of administration which, with no knowledge of comparable natural hazards, assumed sectoral separation.     

Source apportionment of Phoenix PM2.5 aerosol with the Unmix receptor model

The multivariate receptor model Unmix has been used to analyze a 3-yr PM2.5 ambient aerosol data set collected in Phoenix, AZ, beginning in 1995. The analysis generated source profiles and overall average percentage source contribution estimates (SCEs) for five source categories:gasoline engines (33 +/- 4%), diesel engines (16 +/- 2%), secondary SO4(2-) (19 +/- 2%), crustal/soil (22 +/- 2%), and vegetative burning (10 +/- 2%). The Unmix analysis was supplemented with scanning electron microscopy (SEM) of a limited number of filter samples for information on possible additional low-strength sources. Except for the diesel engine source category, the Unmix SCEs were generally consistent with an earlier multivariate receptor analysis of essentially the same data using the Positive Matrix Factorization (PMF) model. This article provides the first demonstration for an urban area of the capability of the Unmix receptor model.