Trace metals, PAHs, and PCBs in sediments from the Jobos Bay area in Puerto Rico

This study provides baseline information on the extent of contamination in sediments of the Jobos Bay estuary and surrounding areas in Puerto Rico. Sediments from Jobos Bay area (n = 14) had higher overall average concentrations than those from La Parguera area (n = 5, used as reference site), in μg/g dw, for As (17 vs 9), Cu (29 vs 14), Pb (11 vs 4), and Zn (64 vs 28); and in %, for Fe (2.6 vs 0.6). Sediments (n = 8) screened for PAHs and PCBs exhibited total concentrations (ng/g dw) that ranged from 40.4 to 1912, and from not detected to 11.21, respectively. The quality of sediments of Jobos Bay could be classified as low to moderate pollution. The proximity to anthropogenic sources of contamination warrants a monitoring program for inorganic and organic pollutants in Jobos Bay area for an effective coastal management program of this tropical ecosystem.     

Assessing conditional extremal risk of flooding in Puerto Rico

We model multivariate hydrological risks in the case that at least one of the variables is extreme. Recently, Heffernan JE, Tawn JA (2004) A conditional approach for multivariate extremes. J R Stat Soc B 66(3):497–546 (thereafter called HT04) proposed a conditional multivariate extreme value model which applies to regions where not all variables are extreme and simultaneously identifies the type of extremal dependence, including negative dependence. In this paper we apply this modeling strategy and provide an application to multivariate observations of five rivers in two clearly distinct regions of Puerto Rico Island and for two different seasons each. This effective dimensionality of ten-dimensions cannot be handled by the traditional models of multivariate extremes. The resulting fitted model, following HT04 model and strategies of estimation, is able to make long term estimation of extremes, conditional than other rivers are extreme or not. The model shows considerable flexibility to address the natural questions that arise in multivariate extreme value assessments. In the Puerto Rico 5 rivers application, the model clearly puts together two regions one of two rivers and another of three rivers, which show strong relationships in the rainy season. This corresponds with the geographical distribution of the rivers.

Trace metals in fish and invertebrates of three California coastal Wetlands

Metal concentrations were measured in selected fish and invertebrate species from Mugu Lagoon, Malibu Lagoon and Ballona Wetlands in southern California in order to assess the extent of metal contamination in these three wetlands. Ranges of element concentrations (in microgram/g) found in biota were: Zn 12-650; Cu 1.9-440; Ni < 1-37; Cr < 1-55; Pb < 0.5-6.8; As < 1-8.5; Se < 1-3.8; Cd < 0.2-0.90; and Ag < 0.3-5.9. Relative to previous studies of California biota, the highest metal concentrations found were for chromium and nickel. The highest levels were in one of the two bottom-dwelling fish (juvenile Leptocottus armatus) (55 micrograms/g) and the two water-column fish sampled (Fundulus parvipinnis and Atherinops affinis) (30 and 24 micrograms/g). At Ballona Lagoon, elevated levels of copper and silver were found in the bivalve Tagelus californianus (440 and 5.9 micrograms/g). Chromium and nickel appeared to be most persistent in fish from Mugu (4.6-55 and 2.6-37 micrograms/g), the most northern site and an active military base, and Ballona (< 1-30 and < 1-16 micrograms/g), believed to be the most metal-contaminated site. Compared to previously measured metal concentrations in species of California coastal waters, these regions revealed higher levels of chromium, nickel, silver, arsenic, zinc, copper and, to a lesser extent, cadmium and selenium. Chromium and silver were present at high enough levels at all three sites to be considered environmental health hazards.     

Trace metals in oysters from Knysna estuary

A preliminary survey of seven trace metals in three species of oyster from the Knysna estuary, South Africa, has been carried out. The results which were obtained indicate that this area is as yet unpolluted and provide base-line levels against which future trace-metal pollution can be measured. Two species of oyster are being grown at a number of sites as part of a long-term programme to monitor trace-metal levels in the estuary.     

Biodegradation of toxic chemicals in Guayanilla Bay,Puerto Rico

Studies were conducted to assess the factors that may influence the rate and extent of biodegradation of biphenyl, naphthalene, phenanthrene, pentachlorophenol (PCP) and p-nitrophenol in water samples collected from the Guayanilla Bay (18 degrees N; 67.45 degrees W), southwest of Puerto Rico. In vitro studies mediated slow degradation of biphenyl, naphthalene and phenanthrene substrates by natural microbial flora present in the Bay. Addition of KNO(3) as a source of inorganic N greatly enhanced the degradation of phenanthrene but not of naphthalene, suggesting that effects on degradation due to nutrient limitation were compound specific. The rate and extent of degradation of naphthalene and PCP were higher in water samples collected closer to the source of contamination, i.e. the petrochemical complex. The identity of a phenanthrene degrading bacterium, previously identified by conventional phenotypic method (Zaidi et al., Utilizing Nature's Advanced Materials, Oxford Unviersity Press, 1999) as Alteromonas sp., was confirmed by partial DNA sequencing of the small subunit rRNA gene.     

Spatial variability associated with shifting land use: Water quality and sediment metals in La Parguera, Southwest Puerto Rico

Development in southwest Puerto Rico, as in many areas of the Caribbean, is outpacing the ability of upland flora, salt flats, and mangroves to capture sediments and intercept and transform nutrients. A comparative study to examine the effects of development on near-shore water quality in La Parguera, Puerto Rico, was initiated in 1998. Total suspended solids were significantly higher in the vicinity of developing areas compared to reference areas. Chlorophyll-a measurements near of the wastewater treatment plant averaged two times the level of other areas. The overall average concentrations of copper, chromium, nickel, and zinc in sediments collected from salt flats exceeded values reported to cause impairment of biological systems. Marine sediments near more developed locations had the highest metal concentrations, suggesting a greater transport in this area. Natural resources are the primary attraction in this area; therefore, protection of near-shore resources should receive greater attention in land use planning.     

Extreme floods and their relationship with tropical cyclones in Puerto Rico

An extreme value analysis (EVA) point process approach has been implemented to examine the flood characteristics of Puerto Rico when tropical cyclones (TCs) are present in the discharge series and when they are removed from it. Mean daily discharge values that exceeded the 99th percentile thresholds were used in both the TC and non-TC data series. In nine of the 12 stations the maximum discharge was associated with a TC, with hurricanes Hortense (1996), Georges (1998) and Eloise (1975) responsible for most of the maximum peaks at each site. Percentage changes in the generalized extreme value parameters, which include location (central tendency), scale (variance) and shape (skewness), between the TC and non-TC data exhibited a decrease in the majority of stations. Stations in the eastern interior and central region of the island showed the largest decrease in all parameters, in flood occurrences and in return periods when TCs were removed from the series.     

Trace metals in sediment cores from Deception and Penguin Islands (South Shetland Islands, Antarctica)

This paper presents information on the levels of trace elements in sediments collected at Deception and Penguin Islands and tracks the sources of natural and anthropogenic inputs of metals into this sub-Antarctic region. The results suggest that natural processes, such as volcanic activity, hydrothermal processes and sediment transport, are more important than anthropogenic inputs in accounting for the metal concentrations measured in sediments at Deception Island. The higher levels of trace metals recorded in sediments at Penguin Island seem to reflect the composition of the source rocks of the island, which are dominated by the olivine-basalt group. Our findings show that human activities in the study areas may contribute to negligible levels of trace metals associated with anthropogenic inputs (e.g., Cr and Zn) in sediments, and these results can be used in the future as background levels related to low anthropogenic impacts.     

Atrazine fate and transport within the coastal zone in southeastern Puerto Rico

Agrichemical transport to coastal waters may have adverse ecological impact. This work examined atrazine fate and transport in a field adjacent to Puerto Rico’s Jobos Bay National Estuarine Research Reserve. The herbicide’s use was linked to residue detection in shallow groundwater and movement toward the estuary; however, data indicated that transport via this pathway was small. In contrast, surface runoff as tropical storm systems moved through the area appeared to have high potential for atrazine transport. In this case, transport to the estuary was limited by runoff event timing relative to atrazine application and very rapid atrazine dissipation (DT₅₀ = 1–3 days) in field soil. Soil incubation studies showed that accelerated degradation conditions had developed in the field due to repeated atrazine treatment. To improve weed management, atrazine replacement with other herbicide(s) is recommended. Use of products that have greater soil persistence may increase runoff risk.     

Trace metals in algae from the Great Barrier Reef

Zinc, copper, cadmium, nickel, lead and mercury concentrations were examined in 48 species of algae from the Great Barrier Reef. In general the data showed considerable inter- and intra-specific variation with mean levels for each metal ranging from 0.27 to 38.6; 0.74 to 11.2; 0.08 to 2.2; 0.41 to 46.1; <0.45 to 6.7, and 0.005 to 0.320 μg g⁻¹ dry weight, respectively. Not-withstanding this, levels of all metals were substantially lower than reported values for algae from metal contaminated environments. The green alga, Chlorodesmis fastigiata, was the only species examined which was abundant at all study sites and, as a consequence, was considered to be the most suitable candidate for continued surveillance studies in the area.     

Trace metals in corals from the Great Barrier Reef

Various octocorallian and scleractinian corals from within the Great Barrier Reef Province were analysed for zinc, copper, cadmium, nickel and lead by atomic absorption spectroscopy. Of the two coral groups, the octocorals accumulated significantly greater amounts of all detectable metals. The soft coral, Sarcophyton sp., revealed distinct inter-locational differences for zinc, copper and cadmium. The potential of this genus for monitoring trace metal pollution in tropical reef waters is briefly discussed.     

Trace metals in tissues of gray whale (Eschrichtius robustus) carcasses from the Northern Pacific Mexican Coast

Samples of liver, lung, heart, muscle, and blubber tissue from the carcasses of juvenile gray whales (Eschrichtius robustus) found stranded on the coast off the Sea of Cortez, México were analyzed for a range of trace metals (Cu, Fe, Zn, Mn, Ni, Pb, and Cd). The highest concentrations of copper, iron, zinc, and manganese were found in liver; nickel and lead in heart, and cadmium in kidney. In all tissues analyzed, iron, zinc and copper were present in the highest concentrations; however, some whales also showed high levels of cadmium in the kidney which could be related to their diet. Elevated concentrations of copper were found only in the liver of one whale. In general, where low levels of iron were found in the liver, they were associated with poor nutrition. Lead, nickel, manganese and zinc levels in liver were within the normal range, indicating that these whales had not been exposed to high levels of these metals.     

Trace element content of metals from L-group chondrites

Eight L- and one LL-group chondrites were selected for a major and trace element content study of their metals by instrumental neutron activation techniques. The elements Ni, Co, Fe, Cu, As, Ga, W, Au and Ir were determined. For each meteorite three metallic fractions were analyzed: (1) coarse, >100 mesh; (2) intermediate, 100–200 mesh; (3) fine, <200 mesh. The composition of the metals varies considerably with grain size, as a result of a preferential concentration of kamacite in the coarse and of taenite in the intermediate and fine fractions.A third metallic component, consisting of very fine plessitic inclusions, was observed in chondrules of equilibrated chondrite types 5 and 6. This component is probably responsible for the decrease of Ni, Cu, Ga and Au observed in the fine metallic fractions of the equilibrated chondrite types.W, as well as Ga, increases in the bulk metals with the petrologic type, suggesting that a substantial amount of this element, as already observed for Ga by previous authors, is not in the metal, but in some silicate phases in the lower metamorphic petrologic types 3 and 4.Ir is always concentrated in the fine metallic fractions of all meteorites, independent of petrologic type, suggesting the presence of a fine-grained metallic component enriched in this element.     

Trace metals in Choromytilus meridionalis

Concentrations of metals in mature females of the mussel Choromytilus meridionalis are approximately twice those in males and some other trace elements also differ according to sex. If this species is to be used as an indicator of trace-metal pollution, comparative data should relate to individuals of similar size and care must be taken to determine whether differences in trace-metal content are the result of seasonal variations or reflect abnormal metal uptake.     

Architecture of the deep critical zone in the Río Icacos watershed (Luquillo Critical Zone Observatory,Puerto Rico) inferred from drilling and ground penetrating radar (GPR)

In the critical zone, surficial bedrock interactions result in the formation of a mantle of chemically‐ and physically‐altered material defined here as regolith. In the watershed of the Río Icacos, an upland river draining the Luquillo Mountains in tropical Puerto Rico, we explored the influence of lithology (quartz diorite versus hornfels‐facies volcaniclastic rock) on weathering. Regolith profiles were studied by drilling boreholes and imaging the subsurface using ground penetrating radar (GPR). Overall, the regolith structure is not laterally continuous but rather is punctuated by zones of deep fractures that host in situ weathering, corestones, and colluvial material. GPR images of these vertical zones show reflectors at 15–20 m depth. Thus, the architecture of the critical zone in the upper Luquillo Mountains is highly dependent on lithology and its influence on fracture development. At the highest elevations where hornfels overlies quartz diorite, positive feedbacks occur when the water table drops so that oxidative weathering of biotite in the more felsic rock creates microfractures and allows deeper infiltration of meteoric waters. Such exposure results in some of the fastest weathering rocks in the world and may contribute to formation of the knickpoint in the Río Icacos watershed. This work represents the first study combining GPR and drilling to look at the structure of the deep critical zone and demonstrates: (1) the importance of combining direct methods (such as drilling) with indirect methods (such as GPR) to understand the architecture of the critical zone in tropical systems; (2) the interplay of the surficial stress regime, lithology and climate in dictating the architecture of weathering. Copyright © 2016 John Wiley & Sons, Ltd.     

Trace metals in sediments from the Ligurian Coast,Italy

The content of trace metals (Fe, Cd, Cu, Ni, Pb and Cr) in the Ligurian Coastal Area were acid leached and analysed by the atomic absorption method. In the stations in front of Genoa, with the maximum organic carbon content, Cr, Cu and Pb show a significant correlation between the leachable fraction with cold reagents and the organic carbon content of the sediment. Significant linear correlations of metals to total Fe were obtained for unpolluted sediments.