Atrazine biota

Some currently used pesticides that are intermediate in water solubility and persistence can reach fairly high concentrations in water, sediment, and biota, in areas of high use. Pesticides that enter the lakes—whether by direct discharge along the shores, by runoff through tributaries, or from the atmosphere—are retained in the system and become more concentrated over time. For example, atrazine is detected widely in streams in the midwestern USA at concentrations in the range of several hundred ng/L to several tens of xg/L [12]. The half-life of atrazine in deeper lakes was estimated to be greater than 10 years. 

The possible environmental fate of chemical transformation products is dependent on various factors. Once formed under certain conditions, transformation products are distributed between four major environmental media air, water/sediment, soil, and biota. Therefore, environmental fate of transformation products is primarily influenced by the properties of the chemical and conditions of environmental media. Differences in fate are clearly due to variance in environmental media with different physical, chemical, and biological properties including temperature, soil type, light intensity, organic matter, moisture, pH, aeration, and microbial activity. For example, mobilities of flve atrazine transformation products, deethylatrazine, deisopropyl-atrazine, didealkyatrazine, hydroxyatrazine, and ammeline, were negatively correlated with soil organic matter content and positively correlated with sand content [43]. 

To date, only sporadic temporal and spatial measurements exist for atrazine concentration in the surface waters of the Chesapeake Bay, and the quality of the data only allows for an order-of-magnitude estimate of the resident atrazine mass. To obtain this estimate, we assume that the bulk of this herbicide resides in the water column and the sediment layer, with negligible amounts in biota and the surface microlayer, a layer of up to 1 mm thick at the air-water inter ce. 

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