Sedimentary record of the impact of management actions on pollution of Cartagena bay, Colombia

Sustainability impacts of sediments on the estuary, ports, and fishing communities of Cartagena Bay, Colombian Caribbean

“…Sediment cores extracted from the coastal zone of Cartagena in 2013 and dated by the 210‐Pb method demonstrated how sedimentation varies both spatially and temporally (Figure 5; Restrepo et al, 2016). For Cartagena Bay (Figure 5a), a median sedimentation rate of 1.80 cm was observed, corroborating other 210‐Pb dating studies in the bay (Espinosa Díaz et al, 2021), while similar sedimentation rates were also observed in Barbacoas Bay to the south (1.84 cm/year) and in the Dique Canal itself at Pasacaballos (1.50 cm/year). Sedimentation was found to be even higher off the coast of the Baru Peninsula (2.06 cm/year), while lower rates were observed in the Honda (0.60 cm/year) and Coquitos lagoons (1.11 cm/year) along the south coast of Cartagena Bay.…”

“…The proximity of these dangerous mercury levels to the surface is clearly of great concern for the ecosystem and coastal residents when one considers the frequent dredging activities needed to maintain the bay's maritime transport sector. Monitoring results presented in Figure 7b show that among various locations sampled over the 2014-2022 period, the median mercury concentration in the sediments on the surface of Cartagena Bay's bottom is 0.11 μg/g (Tosic, Restrepo, et al, 2019), similar to results in other recent studies (Alonso et al, 2000;Caballero Gallardo et al, 2020;Cogua et al, 2012;Espinosa Díaz et al, 2021;Parra et al, 2011). This median value is just below the Threshold Effects Levels (TEL) of 0.13 μg/g (Buchman, 2008) used as an indicator of potential impacts on marine life, which means that about half of the data from Cartagena Bay is above the TEL, while 75% of results from the bay's industrial zone exceed the TEL (Figure 7b).…”

“…However, these sediments also have the potential to bury locally sourced contamination from previous years, such is the case of industrial mercury pollution in Cartagena Bay. Much research has been dedicated to this subject, which found high concentrations of mercury in the bay's sediments (Alonso et al, 2000; Caballero Gallardo et al, 2020; Cogua et al, 2012; Espinosa Díaz et al, 2021; FAO & CCO, 1978; Guerrero et al, 1995; Parra et al, 2011; Tosic, Restrepo, et al, 2019), microplastics (Acosta Coley et al, 2019), marine organisms (Aguirre Rubí et al, 2018; Alonso et al, 2000; Cogua et al, 2012; Guerrero et al, 1995; Olivero Verbel et al, 2008, 2009), coastal birds (Olivero Verbel et al, 2013), and nearby human populations (Alvarez Ortega et al, 2017, 2019; Guerrero et al, 1995; Olivero Verbel et al, 2008).…”

“…Despite the chemical plant's closure, its contamination can still be found buried at the bay's bottom. A sediment core extracted from the nearshore zone adjacent to the plant's previous location was used to reconstruct mercury levels over the 1964–2009 period through 210‐Pb dating (Espinosa Díaz et al, 2021). Results confirmed that high mercury levels still exist at depths corresponding to the plant's operational period in the late 1960s and 70s (Figure 7a).…”

“…(a) Mercury concentration (μg/g) over time from a sediment core taken near the old chlor‐alkali industry in Cartagena Bay (modified from Espinosa Díaz et al, 2021). (b) Box‐plots of mercury concentration measured in the surface sediments of the Dique Canal, Cartagena Bay, Baru Point, and Industrial Zone in 2014–2015, 2018–2019, and 2022 (based on data from Tosic, Restrepo, et al, 2019).…”