Pesticide Concentrations in Stream Sediments from Three Farm Management Approache

The relative impacts of organic, integrated, and conventional sheep and beef farms on the physical and chemical properties of streams have been studied in the past, as well as the impact on stream macroinvertebrates. To determine if these different farming practices affect pesticide residues in streams, Shahpoury et al. (2013) quantified chlorinated pesticides in 100 sediment samples from 15 streams in New Zealand, finding that streams in all three farming categories contained pesticides in the stream sediment, but sediments from conventional farms contained significantly higher concentrations of dieldrin, endosulfans, current-use pesticides, and chlorinated pesticides compared to organic and integrated farms. ā€”Kahea Kanuha

Shahpoury, B., Hageman, J., Matthaei, C., Magbanua, S., 2013. Chlorinated pesticides in stream sediments from organic, integrated and conventional farms. Environmental Pollution 181, 219-225.

There is an increasing global interest in understanding how different farm management approaches affect the environment. Three such management approaches are organic, integrated, and conventional. Organic farming avoids the use of synthetic pesticides and fertilizer, with the goal of using environmentally sustainable approaches to farm management. Conventional farming uses these chemicals. Integrated farming aims to achieve optimal results by finding a balance between the economic benefits of synthetic fertilizers and pesticides and their environmental costs. Pesticides are of an increasing concern because they often have unintentional impacts on non-target organisms and may accumulate in the tissue of animals and humans. In addition, they persist in the environment for a long time and may continue to have environmental impacts long after initial application.
Shahpoury et al. collected sediment samples from 15 streams passing through sheep/beef farms on the South Island of New Zealand. The farms were arranged in clusters at five locations, each cluster comprising three neighboring farms using different farm management techniques: organic, conventional, and integrated. Sediment sample extracts were analyzed for 19 legacy pesticides and 5 current-use pesticides. The current-use pesticides selected for this analysis have been widely applied, previously detected in groundwater systems, are highly toxic compared to other pesticides, and have high volatilization potentials, making them prone to vapor drift from and between farms.
To more easily understand the data, the pesticide concentrations were split into groups for analysis: dieldrin, endosulfans, current-use pesticides, and all pesticides. Dieldrin was originally developed in the 1940s as an alternative to DDT and was widely used in the 1950sā€”1970s. However, long-term exposure has proven toxic to a wide range of animals, including humans; dieldrin has been linked to a range of human health problems and is now banned in most of the world. Endosulfans are highly toxic insecticides banned in New Zealand in January 2009. Current-use pesticides are pesticides registered for use in New Zealand when the sampling took place, while legacy pesticides are pesticides, often very toxic, applied in the past that have remained in the environment.
For each of these pesticides or pesticide groups, mean concentrations were found to be highest in stream sediments from conventional farms. A previous study of the same 15 sheep/beef farming streams found that stream macroinvertebrate communities were more degraded in streams passing through conventional farms than through integrated or organic farms. It is certainly possible that the higher pesticide concentrations found in stream sediments from conventional farms have contributed to the macroinvertebrate community degradation.

Chlorinated pesticides were found throughout the study areas regardless of the farm management strategies applied during the 8ā€”11 years preceding the study. One explanation of this is the high volatilization potential of some pesticides. This results in the pesticides being volatized or evaporated into the air and then carried by wind into a different area. As the impacts and concentrations of pesticides are further studied, it seems clear that pesticide use in farming often has unintended and long-range impacts on areas different from those where pesticides were originally applied.

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