Two years after the riots that focused the world's attention on the sprawling African township on the outskirts of Johannesburg, seething discontent continues to pervade the black community of 1.2 million people.

As the cold weather of South African winter approaches, there is outward calm in Soweto imposed by the white minority government's crackdown on black political activism and arrests of nearly 50 black leaders last October.

But despite their physical proximity, the emotional and political gap between Johannesburg's whites and Soweto's blacks has increased since the riots and the October crackdown.

In addiition, lines of communications between the two groups have been severly damage, suggesting a foreboding disappearance of common ground and will to search for negotated solutions.

One indication was the cancelation last week of a meeting between Connie Mulder, the minister of black affairs, and Dr. Nthato Motlana, the recognized though unelected leader of Soweto's blacks.

Motlana is the chairman of the Committee of 10, an alliance of young black militants and middle-aged moderates that was formed last year following student riots and an extensive school boycott.

The committee, which provided leadership to Soweto, also was to have served as a link between the boycotting students and the white government. But the government last year refused to meet with the committee and jailed all of its members without trail last Oct. 19. In April, five remain in detention.

Mulde and Motlana agreed about a month ago to meet and establish lines of communications. But the members of the committee who are not in prison decided after long discussions that they would not long discussions that they not resume their activities.

The decision effectively left Motlana without a forum for acting on behalf of Soweto and as a consequence, he said he could not meet with Mulder because he had no mandate from the Committee of 10.

In an interview, Motlana said that even when the meeting was still on, it was controversial.

"I got a lot of flak from all sides because of it. Blacks don't want to talk to whites because they say whites don't want to listen. Young blacks ask me "What will you get? Concessions? We don't want concessions, we want the political system changed," Motlana said.

For the past year, Motlana has been in a precarious political position, trying to maintain the respect of and his credibility with younger militants even while he was open to negotating and meeting with white officials. If, as it appears, radical youths are taking an increasingly hard line against contact with white authorities, then Motlana may also be forced to reject contact in order to keep his links with them.

The implications are clear. Only nine months ago, when the Committee of 10, including some young radical members, were ready to talk to the government, they were rebuffed. Now that the government is prepared to meet with the committee's chairman, it is no longer possible.

By its heavy-handed treatment of Soweto's political leaders, the government has created a situation where communication is stymied. On the one hand, it has made moderate leaders afraid to put themselves out on a limb because they might be arrested. On the other hand, it has brought more radical blacks to the conclusion that talking with the white government is no longer worthwhile.

Meanwhile, during the past two weeks, more than 20 people from all over the country have been indefinitely detained and "scores" of others arrested in black and "colored" (mixed race) areas around Johannesburg.

The arrests are seen by many young blacks as an attempt to forestall the organization of political demonstrations on June 16, the anniversary of the first student riots two years ago.

"They are arresting anyone who can organize," said one black youth.

Last year, after several months of relative quiet, the approach of June 16 was heralded by bombings, demonstrations, stonings and detentions that set off a four-month-long school boycott and a period of unrest that spread to several other major urban areas and lasted until the arrest of black leaders Oct. 19.

Some observers, however, do not see the spate of arrests connected so much with the approach of June 16 as with the government's efforts to mute all black political activity that does not take place on government approved platforms.

"I think the arrests are a reaction to the courage of these young blacks who started another organization after the government had made up its mind that the voice of black dissent will not be heard," said Motlana. He was referring to the arrests of nine people, including three officials, of the Azanian Peoples' Organization (AZAPO) formed less than six weeks ago.

The latest police activity has prompted the black daily, the Johannesburg Post, to comment that "detentions without trial are becoming as much a part of our lives as breathing."

Soweto commissioner of police, Brig. Jan Visser said he was not apprehensive about June 16.

"I approach June 16 as any other day. I don't know why people don't want to forget it - it happened two years ago. Since then good relations, bridges, have been built up between us and the community in Soweto," Visser said, adding that church services commemorating June 16 would be allowed. South African law prohibits outdoor meetings of more than three people except by special permission.

But commissioner-designate of police, Gen. Mike Geldenhuys, told the pro-government Citizen newspaper that police were taking the necessary stops to prevent violence before and on June 16.

Deputy head of security police, Brig. Johan Coetzee, said "there had not been a marked increase" in the number of arrests under security laws and the Ministry of Justice failed to respond to queries about the exact number of arrests that have been made in the last month.

But according to the Rand Daily Mail newspaper, 27 people were arrested under security legislation which allows indefinite detention without trial in the last two weeks. Five of those people, including a black journalist, Phil Mtikulu, were released after questioning. Another journalist, July Mayet, is still bein held.

The regular police force also has arrested a large number of people after setting up roadblocks at entrances to black and colored areas around Johannesburg.

Visser would not disclose the number arrested or what the alleged offenses were, but another police official said his men had arrested "scores of people" in two black communities west of Johannesburg. The roadblocks came one day after black power slogans were scrawled on two high schools and the administrative section of one school was set ablaze causing $4,500 in damage.

In another mover egarded by young blacks as an attempt to offset any political activity on June 16, Soweto schools will close June 8, almost two weeks earlier than the normal school vacation which traditionally begins the third week in June. In a community where students do not have cars or telephones, the daily contact at school is the principal means of communication.