From NEILK@dec.anr.state.vt.us Thu Mar 23 13:18:35 2000 Date: Mon, 27 Oct 1997 09:00:24 -0500 From: Neil Kamman To: lakes-l@badger.state.wi.us, PALEOLIM@LISTS.UFL.EDU Subject: Results of mercury sampling query Good day Associates, My sincere thanks to everyone who took a moment (or quite a bit more), to answer my query regarding appropriate sediment sampling strategies for Hg and MeHg analysis. Some very heavy hitters in the mercury field took the time to reply, and I decided that the collective response might be of interest to the community at large. Here is a compilation of responses. Apologies for cross-listing, especially to those with slow connections: The original query: >Here is a question for those of you familiar with clean >methods for acquisition of THg and MeHg samples from sediments. > >I am initiating on a study to evaluate ambient concentrations of this >metal in VT and NH lakes. I am curious how others have collected >sediments while maintaining a strict clean environment around the >sediments. > >My idea is to use a standard corer design (Glew or KB, 3", 30"+ tube) >using 'cleaned' lexan core tubes, sleeves, and cones, meaning only >the corer head will have metal parts (all stainless). Only a core >with a very clean interface, and adequate overlying water will be >accepted. From this core, a sediment subcore will be extracted using >a 'cleaned,' open-ended PETE syringe (a la Gilmour et. al, 1992.). >This protocol should allow the assumption that the mud and interface >actually acquired by the syringe subcorer will never have contacted >the metal from the corer head > >Thus my questions: > >1) Is it reasonable to assume that this protocol will maintain >the integrity of the sediments. That is, not contaminated by the >nearby presence of the stainless corer head? Obviously, this will >need to be tested. > >2) Are there alternate coring strategies, besides diver-assisted? > >3) Are all plastic corers available on the market? > >I appreciate any germane thoughts regading this, and thank you in >advance. Responses: Your query was routed to me by our lakes group in Madison and I will attempt to answer your questions based on our experience. First, the method selected will depend on the question being asked and this was not perfectly clear in your email. If you want to establish geochronologies, then coring tubes are required - along with clean protocols for slicing, etc. I'd suggest you contact Dan Engstrom at the Limnological research Center, U-MN if this is your objective. If you are after contemporaneous concentrations, life can be easier. We typically collect the top centimeter or so (roughly 10 years accumulation in our lakes) from the center of a box core using a cleaned syringe, teflon spatula or plastic spoon. This can be done from a boat or through the ice, taking care during deployment and retreival not to disturb the sample. One can "watch" the descent using sonar. The sample is placed in a clean ziplock bag and frozen until analysis. Enough sample is collected to accomodate subsamples for HgT, MeHg, LOI or TOC, dry weight and % water - plus ancillary elements or compounds of interest. We typically collect samples along a transect in each lake running from shore to deep water. However, the number and location of samples will again depend on your purposes. I trust life in northern Vt is enjoyable as ever. I used to live in Greensboro near Caspian Lake - started my limnological career in the 70s sampling the upper Lamoile with Ginny Garrison and Carl Pagel. Stay well and let us know if we can help in any way. Best regards, Carl C.J.Watras, Research Scientist Environmental Contaminants Section, WI DNR Univ Wisconsin Trout Lake Station 10810 CTY N, Boulder Jct., WI, USA, 54512 cjwatras@facstaff.wisc.edu 715-356-9494 (tel) 715-356-6866 (fax) I hadn't seen any replies to the group so I thought I's send my 2 cents. I was in the same spot a couple of years ago trying to sort out methods and found it frustrating when few people replied. I'm finishing my doctorate working on mercury deposition and bioaccumulation in wetlands. The project combines a number of techniques including coring in wetlands. In wetlands you usually don't need the coring head. The barrel is pushed down by hand. My advisor, Hans Gottgens, has used divers in the western basin of Lake Erie and also has push rods made of some metal that isn't supposed to deform when pressed. The core head is plastic with rubber rings. The plastic could be replaced by Teflon but the rings hold the seal so may be difficult to substitute. What is the design for the Glew corer? I've never heard of one. Off the record, contamination may not be your primary concern if you are dealing with sediments. In Lake Erie the sediments are so hot that we worry about diluting the mercury signal with clean sediments. In water work, the clean protocols have to be very strict to account for ppt analysis. Are your cores going to be dated? Our lab is primarily a paleolimnology lab so the cores here are all lead-210 dated. It's a long process and expensive if it's not done in house. If you are interested in the design of our core head or need leads on other people who might be able to help you, drop a line. Brenda Simmers Dept of Biology University of Toledo Hi Neil: With respect to the head of the corer. I have fabricated some devices with ABS and GP Nylon. The only difference in the design is that the weight is on the external part of the core tube, if you look at the general arrangement drawing of the KB you will see an item that I think is identified as additional weight, in the case of the corers with plastic tops the additional weight becomes the standard weight. Another advantage of this arrangement is that it further lowers the center of gravity of the corer which makes it a little more stable and the lower weight has a tendency to stop the corer penetrating too deeply into the sediment because once the weight enters the sediment there is little mass remaining to drive the corer further. Cheers JRG (John Glew) Date sent: Mon, 20 Oct 1997 06:39 CDT From: "LEVERJ%DNRSD.decnet"@dnr.state.wi.us (Jim Leverance SD WR \(608\)275-3329) To: NEILK@dec.anr.state.vt.us Subject: RE: Collection of sediments for Mercury analysis You probably have already received numerous responses about your question. The U of Wisconsin in cooperation with the DNR's old Research Bureau (now Integrated Science Services) did extensive work on Devil's Lake. This was recently publised and is title "Hypolimnetic methylmercury and its uptake by plankton during fall destratification: a key point of mercury into the food chain of Devil's Lake, Wisconsin". There are numerous references in the document. You could talk with Dick Lathrop who was a part of that study at 608-262-3088 (this is a campus number and he might have to be paged). Doug Knauer would also be another source of information. Doug can be reached at 608-221-6354. Good luck. Date sent: Mon, 20 Oct 1997 09:18:03 +0100 To: neilk@dec.anr.state.vt.us From: Rich Bindler Subject: mercury in sediments I have analyzed sediment cores here in Sweden, as well as previously in Maine. Your protocols seem quite reasonable. In cores I have analyzed and for cores that others have taken in Maine normal coring procedures do not introduce contamination problems with sediments -- the greater problem is when you are looking to analyze the lower concentrations found in water, etc. It is also unlikely you will contaminate with MeHg; the problem there is on the analytical end since some methods for extracting the methyl, such as distillation, can introduce significant errors. For a Hg project I was involved with in Maine we rinsed the core tubes in a dilute HCl solution before coring. Those cores were taken in Acadia Nat. Park for Steve Norton, professor in the Dept. of Geol. Sci, at UMaine, and Terry Haines, professor in zoology at UMaine (and affiliated to USGS). Those might be two persons to contact with questions on strategies for Hg sampling; also they are obviously in your neck of the woods. Terry's research has focused on mercury for the past several years and he has or has had at least a half dozen graduate students focused on Hg research; additionally, he has facilities for analysis of Hg in fish, sediment, and water. But you may already have other arrangements for analyses. So, from what I have seen and experienced up to date, coring itself is not usually a source of contamination, but the handling of the samples afterwards is the greatest concern -- having properly cleaned vessels, glassware, etc. One graduate student under S. Norton has analyzed old archived sediments (10+ years old), which had originally been taken without thought to Hg, and had results very similar to cores taken with Hg analyses in mind -- he got similar sediment profiles and concentration ranges. I hope this is somewhat helpful. But you might consider calling or e-mailing either Steve or Terry. Rich From: Milt Ostrofsky Date sent: Mon, 20 Oct 97 09:05:35 -0400 To: Neil Kamman Subject: Re: Collection of sediments for Mercury analysis In your last post you asked if all-plastic corers were available on the market. I don't know, but they are not hard to make. I assume you have a standard KB gravity corer. The steel core tube is a standard size - 2", I think, and the threads are standard threads. Several years ago I needed to get a longer core, so we went to a plumbing supply store and bought a 3' piece of 2" pipe and had it threaded on both ends. Total cost was about $4. The threads matched the valve end on the corer, and the black plastic nose cone that retains the liner. My point is, you could get a piece of 2" PVC, or lexan if transparency were an issue, and have it threaded at your local plumbing store. This would give you an all plastic corer, at least from the valve assembly downward - all that will come into contact with the sediments. Say hello to Ginny. Milt Ostrofsky Allegheny College Biology Dept. Meadville, PA, 16335 I will send you by mail a copy of a coring protocol for mercury work that was developed last year. If you have follow up questions, you can contact either me or Dan Engstrom, who handles all of the coring I am involved in. Dan is at the Science Museum of Minnesota, and holds an appointment in geology at the University of Minnesota. My off-the-cuff responses: >1) Is it reasonable to assume that this protocol will maintain >the integrity of the sediments. That is, not contaminated by the >nearby presence of the stainless corer head? Obviously, this will >need to be tested. >>Stainless steel is extremely clean for mercury and methylmercury. Methylmercury is harder to contaminate for than inorganic mercury, since there are so few sources of methylmercury. Are you intending on measuring methylmercury in the sediment? If so, please stay in touch with Dan and me, for we will be gathering methyl data on Minnesota cores and interpretation may be problematical. >2) Are there alternate coring strategies, besides diver-assisted? >>You may not want to recore the core, as it may create problems that >>were not there. > 3) Are all plastic corers available on the market? >>>Not that I know of, but somebody may have made one. Dan? Stay in touch, Ed Neil -- I'll send you a copy of the ES&T paper -- it came out last March. The coring procedures we use for our mercury work are not strictly "clean hands" -- nor do they need to be given the high levels of t-Hg normally found in lake sediments (10s to 100s of ng/g dry sediment). Our cores are collected using a 3" diameter piston corer operated by rigid drive rods from the lake surface. The core barrel is polycarbonate, the coring head is aluminum, and the pistons are rubber and stainless. This type of corer produces the least disturbance of the sediment interface of any we have used, and it does not cause problems of core-shortening (compression) that are common to non-piston corers. Moreover, we find it necessary to take very long cores in our culturally impacted lakes (1.5-2 meters long), lengths that are beyond the reach of most gravity corers. Regarding possible contamination of the samples, there is no contact of the sediment with the piston or the coring head. The outer "rind" of the core in contact with the core-barrel should be scraped away to remove the core-wall smear and any possible contamination. We extrude our cores in the field to prevent disturbance of the flocculent surface. The cores are held vertically at all times, and the core is pushed out the top of the core tube using a mechanical extrusion devise the controls precisely the increment in each slice. We wear rubber (vinyl) gloves, use stainless or plastic implements, and transfer the sediments to acid-washed polypropylene jars. We've processed somewhere around 100 cores using these methods and have found no evidence for contamination. I really can't see any reason to employ a second syringe as you propose for subsampling your cores; it could be a nuisance to use in the field, and it may create other problems. I also don't think you need an all-plastic corer, as the sediment normally only comes into contact with the core barrel, never the head (or piston if the corer is so equipped). There's a recent publication that you may have already seen which provides a lot of detail about all aspects of core-work to document historical Hg inputs to lakes and bogs -- you may well have seen it already: 1996. Protocol for Estimating Historic Atmospheric Mercury Deposition EPRI/TR-106768. Electric Power Research Institute, Palo Alto, CA, pp. Hope this helps -- let me know if you have other questions. regards, Daniel Engstrom Dr. D.R. Engstrom St. Croix Watershed Research Station Science Museum of Minnesota Marine on St. Croix, MN 55047 dre@maroon.tc.umn.edu 612-433-5953 (phone) 612-433-5924 (fax) We have collected a number of cores from lakes for Hg analysis using a acrylic piston corer with metal head as well as same tube with core collected by a diver thus no metal. When have found no contamination if sectioned immediately after collection. Also important to have some overlying water as you noted. Paul Garrison WI DNR 1350 Femrite Dr. Monona, WI 53716 Neil, Good people to contact are Dr. Darell Slotton (Director, Aquatic Metals Lab, UC Davis) and Dr. Carl Watras (U Wisconsin, Director Trout Lake Field Station and Director Hg in Temperate Lakes Project). I've cc'd this message to Dr. Slotton. We have been studying Hg in Clear Lake, CA for 5 years now. One of my main projects was a coring study of Clear Lake and one of the things we looked at was Hg, both total and methyl. For longer cores (ca 2.5m) I made my own drive rod operated piston corer, but I have used a Wildco KB gravity corer for some other work here. What are the sediments like at the lakes you want to core? How deep are the lakes? Do you have a point source for Hg deposition, or is it mainly atmospheric? One thing to keep in mind is that the more you core and sub-core the more compression there is to account for. I have read a few papers that say compression can be up to 50% with a gravity corer in soft sediments (I have see approximately this much while coring microcosim experiments we've run, and while sub-coring test cores I've taken). We have very soft sediments here. One thing to remember is that the smaller the diameter gets and the less mass you are getting for each subsample, the more of a problem smearing of the profile can be. For a 2" core, it should be pretty minimal, so further subcoring isn't needed. For narrower cores, the section surface area to volume ratio will get larger, and smearing may become a problem. I don't know what the Hg levels are in your lakes, here we have everything from .1ppm to >100ppm. My KB corer has a plastic head and uses plastic linertubes, and my piston corer was all PVC, so there was no metal/sediment contact for my cores. As far as sub-sampling goes, I wouldn't feel the need to go too overboard on ultraclean equipment for seds. For water, it is very important (the sampling containers mainly (use acid cleaned Teflon only for water collection, double glove, etc...) but, even Dr. Watras, the guru of ultraclean, uses garden hose and a high flow submersible pump for sample pumping. You just have to make sure you collect a high enough volume to wash out any potential contamination, ie. overfilling your sample bottle). You shouldn't be using dirty equipment by any means, but as long as you wash off your sampling and subsampling equipment, you should be fine. We sub-sample with stainless scoopulas into clean Aluminum weigh boats (to dry tHg samples) or directly (for meHg) into Qoorpack jars with TFE lined lids (after drying, the tHg samples are stored in Qoorpacks with TFE lined lids). Make sure you freeze meHg samples asap after sampling, and try not to store them too long before having them analyzed. If they get frozen too long the wet/dry ratios can get altered. We have gotten very good profiles using these techniques, including much better than average tHg QC data. Recently there has been some discussion of problems with meHg extraction techniques causing different "artifact" levels of meHg (Bloom et al., (1997) Fresenius J. Anal. Chem. 358: 371-377). Unfortunately the method that gives the lowest detection limit, also has the potential to cause the most artifact. A good source of information on this would be Nick Bloom of Frontier Geosciences in Washington state. He can point you to a method that should work with the levels you have in your sediments. Best of luck on your work, Jesse Becker Post Graduate Researcher III =========================================== Neil Kamman, Aquatic Biologist VT Department of Environmental Conservation 103 S. Main St, 10N Waterbury, VT 05671-0408 (802) 241-3777 (802) 241 3287 (fax) neilk@dec.anr.state.vt.us http://www.state.vt.us/anr/water1.htm ===========================================