Environmental risk assessment of compost prepared from salvinia, egeria densa, and alligator weed.

Approximately 70,000 m(3) of salvinia (Salvinia molesta) was removed from the Hawkesbury-Nepean River, New South Wales (NSW), Australia, during 2004. This study assessed the risks associated with applying compost prepared from aquatic weeds (AWC) to land, namely, survival and spread of aquatic and terrestrial weeds, eutrophication of waterways, accumulation of heavy metals and phytotoxicity. The results demonstrate composting is an effective method of reducing the viability of aquatic and terrestrial weeds. However, mortality of alligator weed (Alternanthera philoxeroides), which was used as an indicator plant, was significantly (P < 0.001) correlated with the temperature within the windrows and the length of time the material was subjected to composting. Conditions within the central core of the windrow were sufficient to kill the alligator weed, although not all of the aquatic weed material was exposed to the windrows' central core. This resulted in alligator weed continuing to grow at the base of the windrow. To reduce the risk of weeds surviving and spreading in aquatic and terrestrial environments it is suggested compost windrows should be located on an appropriate hard pad to enable complete mixing of the material and ensure all material is exposed to temperatures >55 degrees C for greater than three consecutive days. The likelihood of other risks associated with the AWC was low. If composting is selected as the preferred method for managing organic material harvested from waterways, then ongoing monitoring and evaluation is required to validate the composting process and ensure consumer confidence in the final product.

The development and testing of a prototype on-line radioiodine monitor for nuclear power stations.

A prototype on-line monitor has been developed which is capable of detecting radioiodine in the presence of as much as 1 X 10(6) higher concentration of noble gases. The system contains two identical radiation monitoring chambers through which the monitored air and a purging gas alternately cycle. Each chamber contains a silver zeolite filter which has a high retention of the various forms of airborne radioiodine but low retention of noble gases. During the purging cycle the radioactive noble gases are quickly purged from the filter and chamber and the lower levels of radioiodine accumulated on the filter are detected. This system has been successfully tested using short-lived radionuclides simulating vented reactor gases resulting from an abnormal condition.