Phytoremediation is the use of green plant-based systems to remediate contaminated soils, sediments, and water. Relative to many traditional remediation engineering techniques, phytoremediation is a fledgling technology intended to address a wide variety of surficial contaminants. Phytoremediation targets currently include contaminating metals, metalloids, petroleum hydrocarbons, pesticides, explosives, chlorinated solvents, and industrial by -products. The primary market driver for continued research in this area is the significant cost reduction these systems appear to afford. Phytoremediation, however has inherent limitations in that plants are living organisms with specific oxygen, water, nutrient and pH limits that must be maintained. In addition, significant depth, concentration, and time frame limitations also apply. Despite these limitations, many forms of phytoremediation have emerged from the laboratories and are currently in practice. Commercial phytoremediation systems for clean up of shallow aquifers and water born contaminants are now in place. Field tests for the phytoextraction of metals from contaminated soils are underway as well as advanced stabilization trials. For the most part, the current practices are technically sound, but far from optimized. Field tests have generally been met by good regulatory and public acceptance, yet improvements and extensions can and will be made on many of them. The biological resource for phytoremediation remains largely untapped. Bringing multi-disciplinary teams consisting of biologists, chemists, engineers, as well as lawyers, accountants, and public advocates should continue to yield additional solutions and possibilities for continued application of phytoremediation.Significant quantities of air, water, and soil have been contaminated as a by-product of the industrial revolution and increased urbanization of the landscape. Increasingly stringent standards for water and air quality have propelled whole industries to re-engineer their fundamental 2

The ability of aquatic plants to absorb, translocate and concentrate metals has led to the development of various plant-based treatment systems. The potential to accumulate chromium by Scirpus lacustris, Phragmites karka and Bacopa monnieri was assessed by subjecting them to different chromium concentrations under laboratory conditions. Plants showed the ability to accumulate substantial amounts of chromium during a short span of one week. When the plants were grown in tannery effluent and sludge containing 2.31 μg ml -1 and 214 mg kg -1 Cr, respectively, they caused significant reduction in chromium concentrations. While there was an increase in biomass, no visible phytotoxic symptoms were shown by treated plants. The plants can then be harvested easily and utilized for biogas production.Chromium is one ofthe toxic metals widely distributed in nature. Ofthe two forms found in the environment, trivalent and hexavalent, hexavalent chromium is the form considered to be the greatest threat because of its high solubility, its ability to penetrate cell membranes, and its strong oxidizing ability (1). The large-scale uses of chromium in metallurgical, pigment and dye, and in textile, and electroplating makes these industries potential sources of chromium pollution. The tanning industry is also a major contributor of chromium pollution of water resources. In India, according to a recent estimate, ca 2,000-3,200 tonnes of elemental chromium escape into the environment annually from the tanning industries alone (2). Chromium concentrations in effluents usually range between 2,000-5,000 pg ml" 1 compared to the recommended permissible limit of 2 pg ml 1 . The management of large amounts of effluent discharged by the tanneries has become a formidable task in developing countries. Contamination of water resources by these effluents is posing serious health hazards and is a threat to aquatic ecosystems. 274

The gonadal development of Murray cod, Maccullochella peelii peelii, in Lake Charlegrark, Victoria, and adjacent farm ponds was evaluated. Gonadosomatic index, macroscopic classification and histological analysis were used to determine the age at first maturity and the gonadal development in this introduced population. There is a marked difference between the sexes in the size at first maturity, with females maturing at approximately 6 years of age and 2000 g in weight and males maturing at 3-4 years and 700 g. Gonadosomatic index data indicate that spawning occurs around November. Ovarian development in this species follows a pattern similar to that in a number of other teleosts. Testes have a lobular structure. Macroscopic evaluation of ovaries provided a good indication of the stage of the development of the gonad. However, the presence of spermatozoa throughout the year in the gonads of mature male fish makes the macroscopic evaluation of testicular development less reliable. Three cod, approximately 1% of the population, contained gonads with both ovarian and testicular tissue.

The EC Directive (91/271/EEC) concerning urban waste water treatment has far‐reaching financial and technological implications for local authorities in Scotland which are responsible for sewerage. Increased capital consent limits and additional financial assistance from central government are essential if the requirements of the legislation are to be met. Although the Directive is welcomed in general terms, the sections of the legislation dealing with the identification of sensitive waters and the provision of primary treatment for coastal discharges to less sensitive waters are of limited environmental significance in Scotland. The elimination of sewage sludge disposal at sea will create severe difficulties for Scottish authorities as a high percentage of sewage sludge is currently disposed of at sea. Each of the main alternative disposal options presents environmental, financial and technical problems and, in the case of incineration, the certainty of widespread unpopularity with the public.

Plant roots influence the soil in which they grow in a variety of ways, making the soil more conducive for microbial growth and activity, as well as cometabolic reactions. Studies examining the fate of pesticides in plant-soil systems have revealed a marked decrease in persistence of these compounds. Additionally, similar observations have recently been made for oil residues, polycyclic aromatic hydrocarbons, trichloroethylene, and surfactants. These previous studies suggest that the root zone could potentially be managed to effect bioremediation of surface soils containing hazardous organic compounds through enhanced biochemical transformation of these organic constituents at waste sites by indigenous rhizosphere microorganisms. In order to further test this hypothesis, a study was initiated using soil and vegetation from an existing pesticide-contaminated site in Iowa. Initial characterization of this site revealed several herbicide-tolerant plant species including Kochia sp., knotweed (Polygonum sp.), and crabgrass (Digitaria sp.). Experiments testing the influence of these tolerant varieties on microbial degradation of a mixture of herbicides are reported. By facilitating microbial degradation of pesticide wastes, vegetation could provide a cost-effective and ecological approach to restoration of contaminated surface soils in situ.