Seasonal distribution of dissolved pesticides and polynuclear aromatic hydrocarbons in the Humber Estuary and Humber coastal zone

The distribution of atrazine, 2-methylthio-4-tert-butyl-amino-6-cyclopropylamino-s-triazine (Irgarol 1051), lindane, malathion, fluoranthene and pyrene dissolved in the water column of the Humber Estuary and adjacent coastal zone was determined. Atrazine concentrations declined from the head (35–53 ng l−1) to the mouth (5–11 ng l−1) of the estuary; the highest concentrations were found in June. Lindane concentrations also declined through the estuary, although elevations were observed near a sewage outfall, especially in June and September. Irgarol concentrations typically peaked in April, then decreased in June before increasing again in September. The patterns of variation of fluoranthene and pyrene were similar to each other, suggesting common sources. Levels were similar throughout the estuary, with an exceptionally large elevation at a sewage outfall in June. Malathion concentrations were generally very low (<1–9 ng l−1). The concentrations of all compounds were lower off-shore than in the estuary, suggesting that the Humber catchment is a major source of organic micropollutants to the Humber coastal zone. Concentrations of atrazine and lindane were also elevated at stations close to the Wash, suggesting a contribution from rivers into the Wash