Dan Treado. "Drawing A Record," 2016, oil on panels, 75 x 92 inches; on view at Addison/Ripley Fine Art. (Dan Treado/Addison/Ripley Fine Art)

There are many ways to paint a target. The concentric circles of Washington Color School innovator Kenneth Noland are soft and a bit craggy, and their pigment merges with the canvas. Jasper Johns’s are simpler and more painterly, and often juxtaposed with other elements. Unlike those predecessors, Dan Treado renders colored rings on circular panels, their pulsating orbits meant to evoke hypnotic powers. That’s why his Addison/Ripley Fine Art show is titled “You Are Getting Sleepy.”

The D.C. artist is known for painting abstract patterns that suggest things seen under a powerful microscope: amoebas, cells, subatomic structures. This show includes such pictures, also on circular panels and sometimes grouped with the targets in wall-filling installations. The largest includes 18 abutting or overlapping rounds, half of them targets. It’s a galaxy of random or orderly patterns, all seemingly ready to rotate.

Some of the pieces stand alone, and one suite of vertical stripe paintings uses a rectangular format. Single targets, like the show’s title picture, with its three-dozen rings, are little universes of their own.

Noland concealed the visual evidence of how he painted, and so does Treado, but with a different technique. He applies oils to impermeable surfaces, yet produces the appearance of softness and diffusion. It resembles airbrush work but is achieved with squeegees, scrapers, solvents and brushes of Treado’s devising. The resulting tones are complex and seemingly continuous, even when the hues contrast sharply. The show includes some vast compositions, but the pictures — fittingly for ones partly inspired by the microscopic — are also fascinating at close range.

Dan Treado: You Are Getting Sleepy On view through May 28 at Addison/Ripley Fine Art, 1670 Wisconsin Ave. NW. 202-338-5180. addisonripleyfineart.com.

"Chernobyl Revisited" by Gabriela Bulisova. (Gabriela Bulisova)
Radioactive Shadowlands

The circumstances behind them are similar, but the two sets of photographs in “Half-Lives and Half-Truths in the Radioactive Shadowlands” are very different. The Goethe-Institut show marks the 30th anniversary of the 1986 Chernobyl nuclear-plant catastrophe with disturbing pictures by D.C.’s Gabriela Bulisova. These contrast Dutchman Robert Knoth’s gentler images of the region around Japan’s Fukushima plant, which experienced a triple meltdown in 2011.

Knoth’s work, done for a Greenpeace project, includes misty green landscapes and studies of abandoned structures. The latter are mostly in good repair, with traffic lights and vending machines still plugged in and glowing. Although Knoth did photograph Fukushima-area residents, none of those pictures is included here.

In Ukraine and Belarus between 2002 and 2005, Bulisova documented a more visibly damaged landscape and population. There’s an uncanny image of a horse inside a derelict house, but most of the photos are of people. These include two with visible effects of radiation poisoning: a child with hydrocephaly that later proved fatal, and a woman with a grisly neck scar from surgery to remove her thyroid. Such operations are so common in the region, Bulisova notes, that the wound is called the “Belarus necklace.”

Half-Lives and Half-Truths in the Radioactive Shadowlands On view through May 20 at Goethe-Institut Washington, 1990 K St. NW (entrance on 20th Street). 202-847-4700. goethe.de/washington.

Rikke Kühn Riegels

With their solid lines and seeming depths, Rikke Kühn Riegels’s oil paintings of theoretical buildings appear to be, as the British say, safe as houses. Yet the D.C.-based Danish artist is skeptical, which is why her Hillyer Art Space show is titled “In a State of Impermanence.” Riegels doesn’t depict fires, earthquakes and tidal waves, but she anticipates them.

Rikke Kuhn. "Construction 80," oil on canvas; on view at Hillyer Art Space. (Rikke Kuhn/Hillyer Art Space)

Many of the pictures are based on architectural models or dollhouse-like structures. They use varied perspective as well as imagined shadows and reflections to simulate three full dimensions, and sometimes verge on M.C. Escher-like visual riddles. One painting departs the model shop for the real world, where the artist’s orderly crossbeams become a window through which clouds are visible. Riegels is concerned with the vulnerability of our built environment, but this piece looks out at nothing but blue skies.

Rikke Kühn Riegels: In a State of Impermanence On view through May 28 at Hillyer Art Space, 9 Hillyer Ct. NW. 202-338-0325. hillyerartspace.org.

Lisa Kellner

Although she’s also interested in architecture, Lisa Kellner doesn’t emphasize straight lines. The Maine artist’s “Always Into Now” transforms Target Gallery into something like a 3-D abstract canvas, or in her term, a “painting in space.” Visitors can walk amid the brushstrokes, which are actually swirls of gauzy silk hanging from the ceiling and walls. The palette is mostly peacock, indigo and ivory, and continues in the soft orbs attached to the floor.

The painting’s frame — the room itself — is rectangular, of course. Kellner mimics the space’s right angles in the white lines and squares that punctuate the dark blue walls, and are sometimes highlighted by white fluorescent tubes. Yet the space is defined by softer, freer gestures. Kellner can’t demolish the wall between viewer and artwork, but she does a pretty good job of blurring it.

Lisa Kellner: Always Into Now On view through May 29 at Target Gallery, 105 N. Union St., Alexandria. 703-838-4565, Ext. 4. torpedofactory.org/galleries/target.

Colleen Sabo

The most intriguing of Colleen Sabo’s paintings are the ones in which you don’t know where you are. The Annapolis-area artist’s Touchstone Gallery show, “A Few of My Favorite Things,” includes flower studies and a half-dozen French street scenes. But the pictures that hold the eye are more mysterious: “Red Light,” which hints at a house near a hazy crimson wall of trees, and “Blueberry State,” whose grass, trees and a barn-like roof, all in amber and lavender, flow into each other. The lack of precise detail in these rustic reveries is what makes them such fine places to get lost.

Also at Touchstone is a celebration of the cooperative gallery’s 40th anniversary, with works by 50 current and 40 former gallery artists. The selection is too diverse to be summarized, but among the standouts are pieces by Ellyn Weiss and Janathel Shaw. Weiss contributed three imaginary artifacts, with fossil-like forms embedded in squares of colored wax. Shaw’s “Ode to Sandra Bland” is a ceramic bust that includes an image of a noose and a reference to “Strange Fruit,” the anti-lynching lament sung by Billie Holiday. The craftsmanship is elegant, but the message is raw.

Colleen Sabo: A Few of My Favorite Things and Celebrating 40th Anniversary On view through May 29 at Touchstone Gallery, 901 New York Ave. NW. 202-347-2787. touchstonegallery.com.