C. N. Skorupka

Sources, distribution and variability of airborne trace metals in La Plata City area, Argentina

Airborne particulate trace metals have been measured bimonthly during day and night hours in four permanent stations located in residential, industrial and commercial sectors of La Plata City region, to characterize the sources and variability of atmospheric inputs. Airborne trace metal regional averages (Pb 64 +/- 62, Cu 30 +/- 27, Mn 26 +/- 20, Zn 273 +/- 227, Fe 1183 +/- 838, Ca 5343 +/- 3614, Mg 1472 +/- 967, Cr 4.3 +/- 2.4, Ni 3.2 +/- 3.5 and Cd 0.41 +/- 0.42 ng/m3) are comparable to the values reported for not grossly polluted cities and below the general trend described for urban particulates. Two- and three-way analysis of variance and variance components tests (P < 0.05) were performed to assess the contribution of the diurnal (day vs. night), spatial (inter-station) and temporal (inter-month) components of variability. Trace metal concentrations followed the behavior of total suspended particles with higher concentrations during the day and at the Downtown station and lower at the Residential site. In general, spatial and temporal variations prevailed over diurnal differences. Spatial differences were clearly most significant for Pb, which presented higher values at the Downtown site reflecting the importance of motor exhaust inputs. In contrast, diurnal differences were more important for Mn due to increased dust resuspension during day hours. A seasonal trend with concentrations usually increasing during winter months and decreasing in spring-summer was also detected. Enrichment factors (EF) were calculated to evaluate anthropogenic versus natural element sources. High EF (21-376) were obtained for Pb, Zn, Cd and Cu reflecting the importance of anthropic inputs. The comparison with EF calculated for high-emitting vehicle particle emissions indicated that motor exhausts are the most important source of these elements in La Plata region. In contrast, the EF calculated for Mn, Cr, Ni, Ca and Mg were low (1.3-7.5) suggesting chiefly natural sources, i.e. soil-derived dusts.

Seasonal and inter-annual variability of water quality in the Uruguay River, Argentina

Abstract Water quality of the Uruguay River was evaluated with multi-parametric (temperature, turbidity, conductivity, pH, dissolved oxygen) and sediment trap data (particle flux, total organic carbon and nitrogen contents) and correlated to precipitation, river discharge and El Niño Southern Oscillation (ENSO) indices for the period 2006–2011. Hydro-meteorological parameters averaged 24–85% variability with coincident precipitation (200–400 mm month-1), discharge (7000–28 000 m3 s-1) and turbidity peaks (50–80 NTU) in the austral spring, and absolute maxima during the El Niño 2009 episode. Spectral analysis of discharge and sea-surface temperature anomaly (SSTA) showed consistent variance maxima at approx. 3 and 1.5 years. Deseasonalized discharge was significantly correlated to SSTA. During river floods, pH decreased (from 7.5 to 6.6) and particle dynamics peaked (turbidity: 15–80 NTU; vertical fluxes: 20–200 g m-2 d-1; total solid load: <1000 to 100 000 t d-1),whereas TOC remained stable (3.2 ± 0.8%) and C/N ratios increased (10–12) due to the higher contribution of terrestrial detritus.

Behavior of Dioxin Like PCBs and PBDEs During Early Diagenesis of Organic Matter in Settling Material and Bottom Sediments from the Sewage Impacted Buenos Aires' Coastal Area, Argentina

Settling particles (SPs) and sediments collected in the Buenos Aires sewer area were analyzed for dioxin like polychlorinated biphenyls (dlPCBs) and polybrominated diphenyl ethers (PBDEs) to follow early diagenetic changes during transport and deposition of organic matter. SP showed a temporal trend of higher total organic carbon (TOC) and fresher dlPCBs and PBDEs signatures during warm-rainy months related to more efficient washout of residues. TOC-normalized sediment trap concentrations suggest a diagenetic magnification of dlPCBs during cold-dry months due to enhanced decomposition of TOC, whereas most labile PBDEs appear to follow TOC decay. The diagenetic behavior of individual congeners along seasonal changes (cold/warm) and during deposition (bottom sediment/SP) shows the selective preservation of heavier, more persistent congeners with a positive relationship with sediment half-lives. The 3–4 times diagenetic magnification of heavier congeners observed in bottom sediments would be a prevailing long-term pathway for dlPCBs and PBDEs bioaccumulation in detritus feeding organisms.

Size-related trace metal bioaccumulation in Asiatic clams (Corbicula fluminea) from the Rio de la Plata estuary, Argentina

Asiatic clams from the Rio de la Plata estuary were classified in seven Shell Length (SL) classes (6.0 ≤ SL ≤ 41.0 mm) and analysed for metals to evaluate their bioaccumulation dynamics and characterise the significance of growth-related variability potentially interfering in clam monitoring programmes. Metal concentrations were rather homogeneous (Zn: 223 ± 64; Fe: 222 ± 87; Cu: 29 ± 5.5; Mn: 20 ± 5.5; Cr: 2.9 ± 1.1; Ni: 2.5 ± 0.9; Cd: 0.7 ± 0.3 μg g −1 ). Regression analyses between metal concentrations and clam size, SL, soft tissues dry weight (BW) displayed different patterns: decreasing (Fe-Cd-Cr-Zn), independent (Mn-Ni) and increasing (Cu) concentrations with size, representing accumulation strategies from regulation to net accumulation. Covariance analyses of metal concentrations-SL/BW indicated no significant seasonal differences. Metal particulate phase speciation in the RLP, clam depuration and suspended particulate size-fractionation assays suggest that fine suspended particles are the prevailing clam metal mode of uptake.

Long-Term (1970–2017) Temporal Trends of Polychlorinated Biphenyls in Fish, Settling Material, and Sediments from Populated and Remote Sites in Río de la Plata Estuary, Argentina

Temporal trends of polychlorinated biphenyls (PCBs) were studied for detritivorous fish (1996-2017) and settling material (2002-2017) from polluted Buenos Aires coast and for a dated sediment core (1970-2013) from the outer Río de la Plata estuary. In spite of contrasting concentrations [5.3 ± 6.3 μg·g-1 dry weight (dw) for fish, 48 ± 26 ng·g-1 dw for settling material, and 1.5 ± 0.7 ng·g-1 dw for core], all three revealed exponentially decreasing trends over time (97%, 83%, and 83%, respectively). Time trends showed peak maxima coincident with Argentinas period of maximum PCB usage in 1973-1980 (80 cm depth in the core) and pulse discharges related to PCB banning in 2001-2002 (fish) with a lighter signature enriched in less persistent tri- and tetrachlorobiphenyls. The log-linear PCB time trends compare well with the predicted decrease for a high emission scenario from global emission data; the best fit was observed for the less impacted sediment core (-2%·year-1 versus -3%·year-1 for emission scenario). Steeper slopes are observed for the more polluted settling material (-5%·year-1) and especially for fish, in which the background decline trend tripled after the 2001 PCB pulse (from -7%·year-1 to -21%·year-1). These PCB time trends in related environmental compartments from contrasted sites provide rare evidence for evaluating the effectiveness of control measures in southern South America.