No abstract

The suitability of passive samplers (Chemcatcher) as an alternative to grab sampling in estimating time-weighted average (TWA) concentrations and total loads of herbicides was assessed. Grab sampling complemented deployments of passive samplers in a tropical waterway in Queensland, Australia, before, during and after a flood event. Good agreement was observed between the two sampling modes in estimating TWA concentrations that was independent of herbicide concentrations ranging over 2 orders of magnitude. In a flood-specific deployment, passive sampler TWA concentrations underestimated mean grab sampler (n = 258) derived concentrations of atrazine, diuron, ametryn, and metolachlor by an average factor of 1.29. No clear trends were evident in the ratios of load estimates from passive samplers relative to grab samples that ranged between 0.3 and 1.8 for these analytes because of the limitations of using TWA concentrations to derive flow-weighted loads. Stratification of deployments by flow however generally resulted in noticeable improvements in passive sampler load estimates. By considering the magnitude of the uncertainty (interquartile range and the root-mean-squared error) of load estimates a modeling exercise showed that passive samplers were a viable alternative to grab sampling since between 3 and 17 grab samples were needed before grab sampling results had less uncertainty.

23Pesticide exposure threatens many freshwater and estuarine ecosystems around the world. 24This study examined the temporal and spatial trends of pesticide concentrations in a 25 waterway within an agriculturally developed dry-tropics catchment using a combination of 26 grab and passive sampling methods over a continuous two year monitoring program. A total 27 of 43 pesticide residues were detected with seven pesticides exceeding ecologically relevant 28 water quality guidelines/trigger values during the study period and four (ametryn, atrazine, 29 diuron and metolachlor) of these exceeding guidelines for several months. The presence and 30 concentration of the pesticides in the stream coincided with seasonal variability in rainfall, 31 harvest timing/cropping cycle and management changes. Our sampling approach 32demonstrates that the application of these complementary sampling techniques (both grab 33 and passive sampling) were effective to establish pesticide usage patterns in upstream 34 locations where application data are unavailable. 35

No abstract

Proper application of sunscreen is essential as an effective public health strategy for skin cancer prevention. Insufficient application is common among sunbathers, results in decreased sun protection and may therefore lead to increased UV damage of the skin. However, no objective measure of sunscreen application thickness (SAT) is currently available for field-based use. We present a method to detect SAT on human skin for determining the amount of sunscreen applied and thus enabling comparisons to manufacturer recommendations. Using a skin swabbing method and subsequent spectrophotometric analysis, we were able to determine SAT on human skin. A swabbing method was used to derive SAT on skin (in mg sunscreen per cm(2) of skin area) through the concentration-absorption relationship of sunscreen determined in laboratory experiments. Analysis differentiated SATs between 0.25 and 4 mg cm(-2) and showed a small but significant decrease in concentration over time postapplication. A field study was performed, in which the heterogeneity of sunscreen application could be investigated. The proposed method is a low cost, noninvasive method for the determination of SAT on skin and it can be used as a valid tool in field- and population-based studies.