UUnniivveerrssiittyy ooff RRhhooddee IIssllaanndd DDiiggiittaallCCoommmmoonnss@@UURRII Graduate School of Oceanography Faculty Graduate School of Oceanography Publications 4-17-2013 OOrrggaannoocchhlloorriinnee PPoolllluuttaannttss iinn WWeesstteerrnn AAnnttaarrccttiicc PPeenniinnssuullaa SSeeddiimmeennttss aanndd BBeenntthhiicc DDeeppoossiitt FFeeeeddeerrss Lin Zhang Rebecca Dickhut Dave DeMaster Kari Pohl Rainer Lohmann University of Rhode Island, [email protected] Follow this and additional works at: https://digitalcommons.uri.edu/gsofacpubs TThhee UUnniivveerrssiittyy ooff RRhhooddee IIssllaanndd FFaaccuullttyy hhaavvee mmaaddee tthhiiss aarrttiiccllee ooppeennllyy aavvaaiillaabbllee.. PPlleeaassee lleett uuss kknnooww hhooww OOppeenn AAcccceessss ttoo tthhiiss rreesseeaarrcchh bbeenneefifittss yyoouu.. This is a pre-publication author manuscript of the final, published article. Terms of Use This article is made available under the terms and conditions applicable towards Open Access Policy Articles, as set forth in our Terms of Use. CCiittaattiioonn//PPuubblliisshheerr AAttttrriibbuuttiioonn Zhang, L., Dickhut, R., DeMaster, D., Pohl, K., & Lohmann, R. (2013). Organochlorine pollutants in western Antarctic peninsula sediments and benthic deposit feeders. Environmental Science & Technology, 47(11), p. 5643-5651. Available at: http://dx.doi.org/10.1021/es303553h This Article is brought to you for free and open access by the Graduate School of Oceanography at DigitalCommons@URI. It has been accepted for inclusion in Graduate School of Oceanography Faculty Publications by an authorized administrator of DigitalCommons@URI. For more information, please contact [email protected]. Organochlorine Pollutants in Western Antarctic Peninsula Sediments and Benthic Deposit Feeders. Lin Zhang1,2, Rebecca Dickhut3†, Dave DeMaster4, Kari Pohl1, and Rainer Lohmann1* 1Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882-1197, USA 2 now at Marine Chemistry & Geochemistry,Woods Hole Oceanographic Institution, Clark Lab, MS#25, Woods Hole, MA, 02543 3 Virginia Institute of Marine Science, The College of William & Mary, Gloucester Point, Virginia † deceased 4 Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC, 27695-8208, USA * corresponding author: Tel: 001-401-874-6612, Fax: 001-401-874-6811,E-mail: [email protected] Page 1 of 34 Abstract Sediments and benthic deposit feeding holothurians were collected near the Palmer Long Term Ecological Research grid during the austral winter of 2008. Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were measured in Western Antarctic Peninsula continental shelf sediments, porewater, and benthic biota. Concentrations and fluxes in sediments decreased sharply away from the tip of the peninsula towards its interior. Sedimentary PCB fluxes were order of magnitues lower than reported elsewhere, supporting the notion of a pristiner Antarctic environment. Hexa-chlorinated biphenyls dominated (40- 100%) the PCB profiles in the sediments, while tri-chlorinated biphenyl 28 was the most abundant PCB congener in the porewater. PCB and OCP concentrations in holothurians were comparable to concentrations in other low trophic level biota in the Antarctic food web (i.e., krill). The partitioning of PCBs and OCPs between the sediments and porewater can be explained by a dual- mode model which included both organic carbon and black carbon as partitioning media. Alternatively, a simpler one-parameter prediction assuming coal tar-like organic carbon performed equally well in explaining porewater concentrations The majorities of PCBs (63-94%) in the Western Antarctic Peninsula sediments were bound to black carbon or recalcitrant tar-like organic carbon, thereby lowering porewater concentrations. PCBs and OCPs in the holothurians were in equilibrium with those in the porewater. Page 2 of 34 Introduction The Southern Ocean plays a pivotal role in the global carbon cycle and climate change (1), leading to an increasing amount of scientific activities and the establishment of numerous research stations in the Antarctic (2). Increased anthropogenic activity will very likely place extra stress on Antarctic ecosystems, which includes the contamination by anthropogenic organic pollutants (3). Several baseline studies around deserted and current scientific research stations have been conducted to investigate local levels of contaminants (2, 4, 5). They have found patchy distribution of persistent organic pollutants (POPs) and higher concentrations of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) adjacent to scientific station (5, 6), indicating contamination from human activities. Atmospheric and oceanic long range transport may also contribute to the presence of POPs in the Antarctic (7). Fuoco et al. showed that PCBs were supplied by surrounding seas to the Ross Sea region (8). However, the ‘westerlies’ and Antarctic Circumpolar Current act as physical/dynamical barriers that may significantly impede the atmospheric and oceanic transport of POPs from the north (3, 9). The inter-hemispheric exchange in the atmosphere is slow as reflected by the strong hemispheric gradients in gas phase concentrations of POPs (10) and the north-south atmospheric delivery is less efficient than west-east within the Southern Hemisphere (3). It would take several hundred years for seawater formed in the Arctic to travel to the Southern Ocean according to the 14C data (11, 12) and modeling studies found the transport time for Page 3 of 34 North Atlantic Deep Water from 47°N to 30°S is about 150 years (25 ~ 300 years) and another 95 years (25 ~ 422 years) from 30°S to the Southern Ocean (13, 14) Since the first detection of PCBs and organochlorine pesticides (OCPs) in the Antarctic five decades ago (15, 16), there have been dozens of investigations on the occurrence, distribution of POPs in Antarctic air (17-20), water (8, 21), soil (2, 4), sediments (22, 23), and biota (24-33). Most of the studies were conducted at the tip of the Western Antarctic Peninsula (WAP) and Ross Sea area (2, 6). The physico- chemical properties of POPs plus the seasonal change in the sea ice result in POPs entering the Antarctic coastal waters. POPs deposit on the sea ice and migrate into it. Following sea ice melting, the POPs are released back into the water, where they can enter the sea ice microbial community, and surface phytoplankton and then be transferred within the food web. POPs in the pelagic food web in the Antarctic were found to biomagnify with trophic level (30, 33). Due to their lipophilic nature, POPs can be carried by sinking particulate organic matter (POC) downward to the sediments. When the POC is remineralized by microbes, POPs are released back to the water column or porewater, rendering them available for uptake by the benthos and microbes. To the best of our knowledge, no studies have been conducted on the fate of POPs in sediments and benthic biota in Antarctica. Previous studies suggested benthic-pelagic coupling during winter could occur (34) when the pelagic food sources are limited. Partitioning of POPs from benthic media to benthos may represent another bioaccumulation pathway along the WAP food web. Page 4 of 34 POPs in the benthic media may be less available for uptake by biota due to the presence of black carbon. Previous studies have shown that adsorption onto black carbon present in the sediments can greatly reduce the availability of POPs in the porewater (35-39). Yet these studies have focused on areas strongly affected by human activities and have not investigated pristine locations such as Antarctic. Passive samplers have been proven to be a robust sampling device to determine truly dissolved porewater concentration of POPs (35-40). The importance of black carbon for reducing bioavailability in the porewater thus can be assessed using passive sampler (35-40). The objectives of this study are to 1) provide the first data of POPs in the WAP benthic biota and porewater; 2) investigate the bioaccumulation of POPs by benthic deposit feeders and determine whether different feeding strategies affect body burdens; and 3) study the influence of sediment geochemistry (e.g., black carbon) on the porewater concentrations of POPs in the WAP sediments. Materials and Methods Sampling Locations Sediments and benthic biota samples were collected from five different locations on the WAP shelf near the Palmer long term ecological research (LTER) grid in Jul 2008 (Fig1) (41). Sites 1 to 5 in this study are corresponding to site AA, B, E, F, and G in the FOODBANCS-2 project(42)( http://www.soest.hawaii.edu/expeditions/blog_antarctica/foodbancs2.html). The sampling locations covered a relatively large spatial range with site 1 close to Page 5 of 34 Livingstone Island (62.60°S, 60. 50°W) which is in the Southern Ocean away from the northern end of WAP, site 2 near Palmer Station (64.67°S, 64.05°W), and the rest further south towards the interior of the WAP (see Table 1 for details). The most northern site 1 is about 565 Km away from the most southern site 5. The top sediments (0-5 cm) were collected at approximately 600m depth using a Bowers and Connelly Megacorer (OSIL, Havant, Hampshire, UK, www.osil.co.uk). The benthic megafaunal samples were collected using a 5.5m semi-balloon otter trawl (2cm mesh). The sediments and biota samples were stored in clean amber glass jars with aluminum foil lined lids at -20° C until analysis. Tumbling experiment A non-depletive, polyethylene (PE) passive sampling technique was employed to measure the freely dissolved concentrations of PCBs and OCPs. Passive sampling has been shown by previous studies to be a reliable and robust approach to obtain porewater concentrations of POPs (35-40). The detailed methods have been described elsewhere (37). Approximately 100 g wet weight (40 - 60 g, dry weight) of sediments was added to clean, 250 mL flat-bottom glass jars. A PE sampler (~ 2g) and sodium azide (final concentration = 0.43 µmol/mL) were also added to each jar which was then filled with Milli-Q water. Laboratory blanks were composed of a PE sheet, sodium azide, and Milli-Q water. The sodium azide acted as a biocide to avoid any biological interference with diffusion into the passive sampler. The sealed sediment-water slurries were placed on a shaker table and agitated until equilibrium was reached (~8 weeks). Page 6 of 34 During this time, the samples were kept in an environmental chamber at 20 ± 1°C. Performance reference compounds (PRCs) were pre-impregnated in the PE and used to quantify the equilibrium between porewater-PE system following literature methods (43, 44, 44). See detailed information on PRCs in SI on page 6 and physical-chemical properties used in Table SI-7. Laboratory Analysis Details on organic carbon (OC), black carbon (BC), sample extraction, analysis, derived sedimentary fluxes, and QA/QC are given in the SI. Partitioning models The partitioning of hydrophobic POPs between the lipids in biota and porewater is governed by the partitioning coefficient (K ) when equilibrium is reached. lipid (cid:1) (cid:6) (cid:7)(cid:8)(cid:9)(cid:10)(cid:9)(cid:11) (cid:1) (cid:2)(cid:3)(cid:4)(cid:3)(cid:5) (cid:7)(cid:10)(cid:12)(cid:13)(cid:14)(cid:15)(cid:16)(cid:17)(cid:14)(cid:13) Where C is the concentrations of POPs in the lipids of biota (ng/g lipid) and lipid C is the concentrations of POPs in the porewater (pg/L). Traditionally, porewater absorption into OC was considered as the dominant sorption process between sediments and porewater. This process can be modeled as: (cid:1) (cid:6) (cid:19) (cid:1) (cid:1) (cid:18) (cid:20)(cid:21)(cid:7) (cid:21)(cid:7) (cid:1) (cid:6) (cid:7)(cid:22)(cid:14)(cid:11)(cid:9)(cid:23)(cid:14)(cid:24)(cid:17)(cid:22) (cid:1) (cid:21)(cid:7) (cid:7)(cid:10)(cid:12)(cid:13)(cid:14)(cid:15)(cid:16)(cid:17)(cid:14)(cid:13) where K is the observed partitioning coefficients between the sediment and the D pore water (mL/g), C is the concentration of PCBs and OCPs in the sediments sediments (ng/g dry weight), f is the OC fraction present in the sediment (%, g TOC Page 7 of 34 OC/g sediment dry weight) and K is the equilibrium partitioning coefficient OC between OC and water (mL/g). Absorption of POPs from water into octanol has been used as a standard partitioning reference to describe the absorptive partitioning to general organic phases. A slope close to 1 of the linear regression between logK and logK OC OW indicated similar processes controlled partitioning into OC and n-octanol (45). log K = 0.97*log K – 0.12 (cid:1) OC OW The K values were derived from the linear free energy relationship (LFER) with OC corresponding octanol-water partitioning coefficients (K ) (Equation (cid:1)) (45). The OW K LFER relationship was derived for only biogenic source OC and humic OC substances that were not produced by burning (pyrogenic source > 50°C) and not altered by diagenetic effects (46). In other words, the derived K did not OC include any BC contribution which is suitable for this partitioning model (Equation (cid:1)). The OC is also defined as amorphous organic carbon (AOC) in other studies (36). The following bimodal partitioning model has been proposed to account for the partitioning into BC (47): (cid:1) (cid:6) (cid:19) (cid:1) (cid:25)(cid:19) (cid:1) (cid:27)"#$ (cid:1) (cid:18) (cid:21)(cid:7) (cid:21)(cid:7) (cid:26)(cid:7) (cid:26)(cid:7) (cid:4)(cid:28)(cid:29)(cid:30)(cid:31) !(cid:30)(cid:29) where f is the fraction of BC present in the sediment (g BC/ g sediment, dry BC weight), C in this equation (cid:1) has a unit of ng/mL, K is the equilibrium porewater BC partitioning coefficients of POPs between BC and porewater (mL/g), which is dominated by adsorptive partitioning. And n is the Freundlich exponent for Page 8 of 34 adsorption onto BC, which reflects non-linear partitioning and often is found to be between 0.3 and 1 (48). See detailed information on K and K in Table SI-7. BC OW Previous studies also provided an alternative one-carbon model approach (total organic carbon) to interpret the partitioning of pollutants between sediments and porewater(36, 49-52). The TOC include both AOC and BC. Hawthorne et al (36) compiled log K (L/kg ) for 53 different sediments historically contaminated TOC TOC with PCBs and suggested to use a coal-tar poly parameter linear-free energy relationship (pp-LFER) for estimating log K (See detailed information on log TOC K in Table SI-7). We also followed this approach to predict the partitioning TOC behavior of PCBs between sediment and porewater by modifying equation ② (replacing K with K ). OC TOC Results and Discussion Sediment & Biota Characteristics Phytoplankton derived organic matter can be stored in the WAP shelf on the time scales of months and years, acting as a “foodbank” for benthic detritivores (34, 53, 54). Previous studies also suggested that there was no or little variability among the organic matter in the WAP sediments, though there were seasonal pulse inputs of bloom-generated organic matter from the overlying water column (55). This has been evidenced by previous staple isotope studies on sinking particulate organic matter (POM), sediments, and benthic biota (55). The isotope signatures of POM and sediments showed little seasonal and inter-annual variations (55). Thus, benthic deposit feeders were exposed to similar fresh detrital carbon year-round (42). It is also expected that benthic detritivores showed Page 9 of 34