Assessment of trace metals, total organic carbon and total nitrogen of a shrimp farm system in Southern Brazil

Abstract

The unconsumed food in shrimp farm systems is responsible for increasing the organic compounds in sediment, and it is a potential source of trace metals. This study evaluates the total organic carbon (TOC), total nitrogen (TN), copper (Cu) and zinc (Zn) concentrations in sediments from control sites, a shrimp pond, a sedimentation basin and receiving ecosystem effluents at a semi-intensive Litopenaeus vannamei farm in southern Brazil. Copper and zinc concentrations were also analyzed in shrimp tissue. The sediment samples were taken before the effluent discharge (BD), 1 day post discharge (1PD), 10 days post discharge (10PD) and 30 days post discharge (30PD). The TOC concentrations ranged from 0.12 to 0.67%, and the TN concentrations were <0.07% in all samples. The labile Cu and Zn concentrations in sediment ranged from 0.12 to 1.27 μg g−1 and from 0.51 to 3.07 μg g−1, respectively, while the more strongly adsorbed fraction of Cu ranged from 0.3 to 2.65 μg g−1, and that of Zn ranged from 30.44 to 121.4 μg g−1. Some significant differences (p < 0.05) were observed among the sites, but they were not related to the effluent discharge. Pearson correlation analysis showed no relationship between the effluent discharge and increased TOC, TN, Cu or Zn values in the sediment, except in the 1PD sampling. The Cu and Zn concentrations in the shrimp tissues were 6.63 ± 0.2 μg g−1 and 19.76 ± 0.2 μg g−1 in pond 1 and 7.6 ± 0.51 μg g−1 and 19.13 ± 0.32 μg g−1 in pond 2. All parameters were within in accordance with the guidelines levels, and this shrimp farm did not have adverse effects on the environment when considering these parameters.