When Spanish explorers first viewed the Delta from the top of Mt. Diablo in the late 1700’s, they thought they had discovered an inland sea. A vast low-lying, partly submerged marshland of wetland plants (tules) and winding tidal channels, the Delta teemed with birds and game animals, including elk, antelope, and grizzly bears. It’s only human inhabitants – small settlements of Miwok Indians – fished and hunted there during the drier months.

Today the Delta, dotted with levees and constructed islands, bears little resemblance to its native state; much has been reclaimed for agricultural use. But it wasn’t until the mid-Nineteenth Century, just over 150 years ago, that its momentous physical transformation began. It’s been a Herculean effort to meet the steep demands of California’s increasingly crowded and insatiably thirsty population, nearly two-thirds of who rely on the Delta as a primary water source. A stark symbol of our quest to bend nature to our will, the Delta also remains the epicenter of an epic drama of seemingly insurmountable political battles and power struggles, pitting north against south; farmer against environmentalist.

So how did it get like this?

Take a quick paddle through the key events in the slideshow above.

Cinnabar from Lake County. Photo by Andrew Alden.

It's widely known that California has a mercury problem unlike other parts of the world. We don't produce it and we don't emit much any more, but a lot of old mercury is still lying around from the mining days. How did that happen?

In undisturbed nature, mercury is no more than a very local and very temporary problem. Mercury occurs mostly in sulfide compounds that are concentrated where ore-forming fluids invade metal-rich rocks. Cinnabar and metacinnabar are both mercury sulfide, HgS. Metacinnabar forms at higher temperatures.

Metacinnabar from the Mt. Diablo Mine. Photo by Andrew Alden.

The California Coast Range was a natural place for world-class mercury ore bodies to grow. First, the range has a large amount of metal-rich rocks in the form of serpentinite and its parent rock, peridotite, derived from ancient seafloor. Second, these rocks were cracked and tilted as the Coast Range was built. Third, volcanic activity worked over these rocks, adding heat and chemically active fluids. Thus the source rocks were repeatedly mobilized, attacked and disrupted, a natural refining sequence that at each step concentrated metals.

Serpentinite is a slippery rock that tends to attract faults, which in turn attract fluids. Hot deep fluids replaced the serpentinite with carbonate minerals like calcite, then again with silicate minerals like quartz. As veins of these minerals fan outward they carry mercury with them. Coast Range mercury was originally deposited at high temperatures deep underground, often associated with gold sitting a bit deeper. It remains for erosion to slowly uncover the ores. In coastal California, erosion is quite active as the Coast Range continues to rise.

Wide zones of silica-carbonate alteration dot our mountains and host hundreds of mercury occurrences. The great New Almaden Mine, south of San Jose, exploited a deposit of this type. It was the largest mercury producer in North America, spawning the gold mining industry that followed the placer gold rush of 1849. Cheap, efficient mercury amalgamation was the key to gold production, and New Almaden mercury made it feasible.

Yuba Gold Dredge 17, still working the Sierra gravels, uses mercury amalgamation to capture flour gold. Photo by Andrew Alden.

Volcanic heat also spawns hot-spring activity that can create mercury ore bodies, too. The McLaughlin Mine, north of Lake Berryessa, exploited a hot-spring type deposit yielding gold as well as mercury.

Today the mercury mines of the Bay Area are all closed and being remediated. The New Almaden property is now a county park and the McLaughlin Mine is being carefully restored to a working countryside. Fortunately, mercury can be well controlled if acid mine drainage can be prevented, because cinnabar is poorly soluble except in strongly acid waters. At Clear Lake, the large former Sulphur Bank Mine is slowly getting under control. The privately owned Mount Diablo Mine, where my metacinnabar specimen was collected, is not a threat to spill into local streams although money is needed to fix it for good.

Worldwide, the overwhelmingly largest source of mercury pollution is from the burning of coal. A much smaller source is from oil and gas. Mercury appears to ride along with oil and gas as they trickle from their source rocks upward into the reservoirs we mine for energy. In oil, mercury lives in the tiny metal portion; in gas, mercury is a vapor. Levels in both are in the low parts-per-billion range, although California's oil tends to have relatively high levels. Mercury levels are highest in the dense fraction called petroleum coke, which is burned in place of coal. Even so, coal is far dirtier in terms of mercury, and the Bay Area is spared that insult.

More reading:

• Mercury Cycling and Bioaccumulation in Clear Lake, special issue of Ecological Applications
• Mercury Geoenvironmental Models by James Rytuba (US Geological Survey)

Suspended Sediment Concentration in the San Francisco Bay, USGS. Click here for a larger version of the image.

Much of the gold extracted from the Sierra foothills during the Gold Rush was in placer deposits. That is, it was mixed with the rest of the sediment naturally eroding from the mountainside. Flecks of gold have a greater density than almost all the other particles and, thus, can be concentrated through natural water movement. A similar process is seen when you go to the beach. When the mixture of minerals and waves are just right you might notice darker grains of sand creating streaks or patches in the wet sand.

Miners had to devise ways to extract the gold because it was still a minor component even in rich placer deposits. Methods like panning and simple equipment like sluice boxes were used with moving water to enhance the natural mineral separation process.

When all this relatively easy-to-get gold was extracted from the streams and rivers prospectors turned to hydraulic mining to obtain the riches. Hydraulic mining was the process of using high-powered water canons to artificially erode gold-bearing hills made of sedimentary deposits. These sedimentary deposits were ancient stream beds that contained gold in placer deposits much like the modern streams did. Essentially, hydraulic mining eroded ancient river sediment from the hillside and diverted the material into the modern river where miners then extracted the gold.

Unsurprisingly, the activity of hydraulic mining devastated the local environment. The landscape was scarred and the mountain streams choked with gravel and sediment. And the effects weren't just local. These rivers and streams flowed into the San Joaquin River and Sacramento River and deposited some of this sediment in the Central Valley causing flooding and navigation problems. Some of the finer sediment was transported even further, to the San Francisco Bay.

The effects of hydraulic mining practices are still measurable in the Bay today. Geologists from the USGS are studying the amount of sediment the Sacramento-San Joaquin Delta delivers to the Bay and are finding that the Gold Rush-induced sediment levels might be diminishing:

"[USGS geologist David Schoellhamer] says all the extra sediment has finally worked its way past the Golden Gate. The bay's water is about 30 percent clearer than it was 10 years ago."

It is taken many decades for this complex sediment delivery system to reach a new equilibrium. However, the readjustment of the estuary to these 'new' conditions might create new problems:

"Less sediment in the bay could spell trouble if scientists' predictions about rising sea levels come to pass. These delicate tidal marshes could be inundated over the next century."

What I find fascinating, yet also extremely challenging, is how the choices we've made as a civilization over the decades and centuries combine and sum to create the issues we face right now. There are no simple answers. Regardless of how well-intentioned some environmental programs may be there will always be some uncertainty about how natural systems respond. Continuing scientific research of these systems will reduce that uncertainty and inform policy decisions of the future.

Images: (1) California Water Science Center; (2) Wikipedia

37.7749295 -122.4194155

Generally speaking, these habitats are the marshes, sand beaches, mudflats and the shallow waters of our rivers and creeks whose soil is saturated with moisture either permanently or seasonally; such areas may also be covered partially or completely by shallow pools of water.

They are also nature’s best defense against climate change and subsequent sea-level rise, because of two important functions they perform: they help reduce the concentrations of greenhouse gases through their ability to sink carbon; and store and regulate water. In other words, they act as sponges absorbing any overflow of water.

The federal government came to understand how biologically productive wetlands are and in 1977 enacted the Clean Water Act, the primary federal law in the US governing water pollution and limiting wetlands destruction. The law also created requirements that if a wetland had to be drained, developers at least had to offset the loss by creating artificial wetlands.

Wetlands have historically been the victim of large-scale draining efforts for real estate development, flooding them for use as recreational lakes or agriculture. Ironically, wetlands absorb and protect the surrounding ecosystem from the polluted run-off coming from the agricultural lands that displaced them.

Since 2000, more than 300 wetland restoration projects have been commissioned, varying in size from the 0.7-acre large 12^th Street Reconstruction Project in Alameda County to more than 13,000 acres being restored as a part of the South Bay Salt Pond Restoration Project in San Mateo County. However, the collective size of the projects (58,889.5 acres across California) is dwarfed when you consider that the state has lost 95 percent of its wetland habitat in the past 125 years.

Worldwide, it is estimated that by 1993 half of the Earth’s wetlands had been drained, according to a report published in the New Scientist.

Below you’ll find a map detailing the restoration projects taking place in the San Francisco Bay Area that shows information of their size, location and construction status.

View Wetland Restoration Projects–Northern California in a larger map

Listen to The Changing Bay radio report online.

37.827184 -122.421682

This is one of those environmental stories where one event, seemingly far in the past, can have a surprising ripple effect into the future. Most of us think of the Gold Rush and picture prospectors panning for gold in streams and rivers. But some miners used more industrial techniques like hydraulic mining. Using massive, pressurized hoses, they washed down entire mountainsides to get to the gold. (Check out this clip from the KQED special "Saving the Bay" for more).

As a result, millions of tons of sediment washed into rivers and streams in the Sierra foothills and made its way down to San Francisco Bay.  Amazingly, that process has taken decades, creating a murkier bay in the meantime.  Ten years ago, scientists at the US Geological Survey noticed the bay was clearing. While that can have many causes, scientists believe that the sediment pulse from the Gold Rush had finally worked its way out of the system.

It seems like the story would end there, but sediment has a complex role in the bay. Some ecosystems, especially wetlands, depend on sediment.  Salt marshes are built on every high tide by sediment that gets trapped in the plants.  These wetlands are also continually sinking as the soil settles, so this growth is key for keeping them at the right elevation. Less sediment in the bay means there's less for the wetlands, which could be an issue. But there's one thing that makes it worse: sea level rise. Some estimates say that the bay could rise by 55 inches by the end of the century.  That means sediment will have an increasingly important role in the future, one that state agencies are just starting to plan for.

Listen to The Changing Bay radio report online.

37.827184 -122.421682

Mercury is a poisonous metallic element that is liquid at room temperature.

There's nothing like producing a controversial story on some favorite food group to have a profound effect on one's appetite. I gave up chicken after doing a story on factory farms (I already didn't eat beef or pork or I would have eliminated those as well.) Now, fish, too, has fallen from grace. Ignorance was bliss.

I've known for quite some time that some fish, especially tuna, were high in mercury. But discovering the extent of the problem, and that halibut and sea bass were also on the “do not eat too much of” list, was eye-opening for me. Now I count fish servings like some people count calories. Japanese cuisine, one of my favorites, has lost some of its glow, as well as its frequency in my dining-out plans.

Many of you have practical questions, as did I. How big a crimp does this have to put in my diet? How much is too much? How often is too often? Can I still enjoy that tuna sashimi and not worry about mercury overload?

Because there wasn't time in the QUEST TV segment on mercury in the bay to include information on safe fish eating practices, below are the guidelines, along with web links, to help you get plenty of Omega 3s and still keep your mercury levels low.

Here's what California's Office of Environmental Health Hazard Assessment says about eating fish from the San Francisco Bay and Delta Region.

• Women beyond childbearing age and men should eat no more than two meals per month of San Francisco Bay sport fish, including sturgeon and striped bass caught in the delta. (One meal for an adult is about eight ounces).
• Women beyond childbearing age and men should not eat any striped bass over 35 inches.
• Women of childbearing age, pregnant, nursing mothers, and children should not eat more than one meal of Bay fish per month. In addition, they should not eat any striped bass over 27 inches or any shark.
• This advisory does not apply to salmon, anchovies, herring, and smelt caught in the bay; other sport fish caught in the delta or ocean; or commercial fish.
• Richmond Harbor Channel area: In addition to the above advice, no one should eat any croakers, surfperches, bullheads, gobies or shellfish taken within the Richmond Harbor Channel area because of high levels of chemicals detected there.

Here’s a summary of the joint fish advisory published by the FDA and EPA for women who are pregnant, breastfeeding or may become pregnant and for children. This is a general advisory not exclusive to any water body.

• Do not eat Shark, Swordfish, King Mackerel, or Tilefish because they contain high levels of mercury.
• Eat up to 12 ounces (2 average meals) a week of a variety of fish and shellfish that are lower in mercury. Five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish.
• Another commonly eaten fish, albacore ("white") tuna has more mercury than canned light tuna. So, when choosing your two meals of fish and shellfish, eat only up to 6 ounces (one average meal) of albacore tuna per week.
• Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) per week of fish you catch from local waters, but don't consume any other fish during that week.
• Follow these same recommendations when feeding fish and shellfish to your young child, but serve smaller portions.

Also, check for local advisories for each water body in California that has fish consumption guidelines. They vary by water body.

And lastly, here’s some practical advice from Dr. Jane Hightower, the medical doctor who we feature in the mercury story.

• “If you’re genetically susceptible, it’s really important to know that if you are an autoimmune-prone patient, Lupus, MS, thyroiditis, these kinds of things, then you should not consume mercury on a regular basis or at all. … And then the cardiac patients. You know, mercury can cause a reaction in vessels that leads to inflammation. So you want to have your Omega 3 fatty acids, which is anti-inflammatory. And not have mercury which is pro-inflammatory…. If you want to avoid significant mercury and you just don’t know what the mercury content is in the fish, a rule of thumb is to eat the small fish. Not a piece of the fish. If it comes in a steak, you want to know how big the fish was that the steak came from. You want the whole fish to fit on your plate. Don’t buy a bigger plate. Get a smaller fish. With the exception of salmon. Salmon can have elevated mercury, but very rarely.”

Good luck, good health, and and watch out for bones!




Watch the Mercury in San Francisco Bay television story online.




37.8627 -122.318

Tags: almaden, gold rush, mercury, mining, poison, pollution, total maximum daily load, toxic
]]> http://science.kqed.org/quest/2009/10/06/producers-notes-mercury-in-san-francisco-bay/feed/ 0 37.8627000 -122.318000037.8627000-122.3180000 http://science.kqed.org/quest/slideshow/web-extra-farallon-islands-history-timeline/ http://science.kqed.org/quest/slideshow/web-extra-farallon-islands-history-timeline/#comments Sat, 25 Jul 2009 20:25:22 +0000 Dan Gillick http://science.kqed.org/quest/?post_type=slideshows&p=19855 The Farallon Islands, precariously perched just a few miles from the edge of the North American continental shelf, are home to an incredible array of wildlife, from tiny Auklets to Great White Sharks, The islands have played a surprising role in the cultural, economic, and technological development of the city of San Francisco. This timeline outlines the landmark events between Sir Francis Drake's landing in 1579 and the present day.
Tags: california, Farallon Islands, gold rush, history, san francisco, timeline
]]> http://science.kqed.org/quest/slideshow/web-extra-farallon-islands-history-timeline/feed/ 2 37.698509 -123.00391937.698509-123.003919 eggmen-on-farallones640 http://science.kqed.org/quest/2008/04/18/reporters-notes-mercury-in-the-bay-part-1/ http://science.kqed.org/quest/2008/04/18/reporters-notes-mercury-in-the-bay-part-1/#comments Sat, 19 Apr 2008 02:29:06 +0000 Amy Standen http://www.kqed.org/quest/blog/2008/04/18/reporters-notes-mercury-in-the-bay-part-1/

View Larger Map

In honor of Earth Day, we wanted to take a big look at a chronic environmental issue in the Bay Area, tracing it from its origins to the contemporary strategies to solve it. Mercury was the obvious choice: It's been flowing into the Bay since before California joined the union, and it continues to trickle in from not just the old culprits, like gold and mercury mines, but a modern crop of industries, like refineries and cement kilns. Even little things – like a broken mercury thermometer dumped into the sink – are part of the problem.

The key fact here is how incredibly potent mercury can be: Just one little globule from an old thermometer can poison all the fish in a 45-acre lake, making them unsafe for humans to eat. Mercury pollution is hardly unique to the Bay Area; what makes us interesting is that local officials are making real strides in trying to clean it up. Over the next 17 years or so, we'll spend $2.6 billion dollars on the project. Even then, we won’t have a clean bay for 120 years.

For a lot of people, mercury pollution in the Bay is largely theoretical, since few stores sell fish caught in the Bay, and relatively few residents fish for their food. But some still do – including many recent immigrants from fishing-intensive cultures like Laos. We’ll look at how mercury affects the health of local fishermen next week.

This piece marks our first-ever audio slide show, and what a difference it makes! We also hope you'll check out the mercury map above, where you can see how many pounds of mercury come from each of the Bay Area’s five refineries, plus other mercury sources and the bay's popular fishing spots.

Watch the audio slide show of "Mercury in the Bay" online, as well as find additional links and resources.

Amy Standen is a Reporter for QUEST and Radio News at KQED-FM.



37.179 -121.819

Tags: almaden, cinnibar, gold, gold rush, kqed, kqedquest, mercury, mine, mining, pollution, quicksilver, Radio, water, watershed
]]> http://science.kqed.org/quest/2008/04/18/reporters-notes-mercury-in-the-bay-part-1/feed/ 0 37.1790000 -121.819000037.1790000-121.8190000