When supporters of a new toxic waste cleanup law tried to lobby Congress yesterday with soil and water samples taken from back yards back home, they got a much bigger reaction than they bargained for.

"I was just outside," said Rep. Patricia Schroeder (D-Colo.), "and there were all these extra police and TV cameras, and I thought something awful had happened. I asked one of the policemen, 'What's going on?' And he told me, 'They were gonna bring you dirty water, but we're not gonna let it in.' "

"Are they telling me that I can live right beside 100 million gallons of this stuff, and they're afraid of a little jar?" asked Bonnie Exner of Denver, who gave Schroeder samples of her back yard dirt and creek water taken near Denver's infamous Lowry Landfill, after staffers for Colorado Republicans Dan Schaefer and Hank Brown refused at first to accept them.

"That is correct," said Richard Jones, legislative assistant to Rep. Elwood Hillis (R-Ind.), another refusenik. (Brown and Schaefer's offices later reversed themselves.) "They do live with this in their back yard, and yes, it is true that I do not want a bottle of it on my desk."

It was all in a day's excitement for partisans of "Superdrive for Superfund," a four-truck convoy loaded with placards, petitions and mason jars which has been criss-crossing the country since Labor Day to dramatize their demands for tougher legislation.

Yesterday at the Capitol, as the Senate passed a $7.5 billion Superfund cleanup bill and sent it to the House, the group culminated a 15,000-mile campaign through 100 toxic dumping areas -- from the Stringfellow acid pits of Glen Avon, Calif., to the P.J.P. Landfill of Jersey City -- by holding a rally and then lobbying House members on behalf of a $10 billion version of the bill.

"Where's my jar of toxic fumes?" asked Esla Bynoe-Andreolo, an activist from Jersey City, home of perpetual underground fires, as she perused several samples sitting under an oak tree. "I thought I had a jar of toxic fumes here somewhere." The would-be lobbyists said the stuff in the jars was not really toxic, just "symbolic." But it was just this sort of symbolism that alarmed House Sergeant-at-Arms Jack Russ.

Russ said he learned about the plans from a "Superdrive" press release -- not, as some of the activists suspected, from a tip from the opposition -- and ordered beefed-up security at House office buildings. He then required the group, on pain of arrest, to phone each member's office for permission to deliver the jars, and supply the sergeant-at-arms with a list of names for verification.

"What would keep somebody who hated a member of Congress from bringing in some very dangerous material?" said Russ, whose employes spent much of the morning phoning members about the jars. "The group couldn't guarantee to me that it was safe. I have an obligation to protect members of Congress, period. That's my responsibility. It has nothing to do with politics." Eric Draper of the National Campaign Against Toxic Hazards, the sponsoring organization for yesterday's events, said 47 members eventually accepted the jars while four declined.

Said Boyd Marcus, press secretary to Thomas J. Bliley Jr. (R-Va.), one of the four, "This is all very silly. It's a publicity stunt on their part to gain attention. I don't have anything to do with a pile of dirt."

"We have a small office," said Billie LaBarbera, personal secretary to Rep. H.L. Sonny Callahan (R-Ala.), who also begged off. And if it's something that's dangerous, we just don't have room in here to walk around it. Anyhow, we get enough of toxic waste in our own district."

Joel Cassiday, press secretary to Hank Brown, was chagrined by the whole affair. "I can't understand why they would try and politically embarrass somebody without giving them a chance to know what their position is on the issue," he said. "This morning, Capitol security called and said these people wanted to bring by an actual bottle of toxic materials. We're not equipped to dispose of it properly. I can certainly understand why no one else would want it either."

Cassiday said he changed his mind after being assured by the lobbyists that the jars were not harmful.

Said Holly Propst, press secretary to Dan Schaefer, "Originally when we got the call, we were told it was a small sample of toxic waste. We have since been assured that it's symbolic. So we are allowing them to send the sample. We weren't aware of the magnitude this seems to have taken on."

Pat Schroeder, whose district is adjacent to Brown's and Schaefer's, was not inclined to be charitable about their initial reluctance to take the dirt. "It's 'hear no evil, see no evil.' It really is tragic."

She plans to have some fun with her colleagues. "I'm going to call them and tell them, 'I have some of your district in my office.' "