Improvements in it aerospace and and aluminum businesses and near-record earnings in chemicals helped Martin Marietta Corp. of Bethesda post profit increases of 9 percent in the second quarter and 7.7 percent in the first half.

Martin Marietta said it earned $58.8 million ($2.36 a share) for the quarter, up from $53.9 million ($2.15) a year earlier. First-half net climbed to 93.3 million ($3.75) from $86.6 million ($3.44).

Slaes for the quarter increased by $120 million to $643 million and for the six months were up from $961 million to $1.2 billion, the company reported.

President J. Donald Rauth said Martin Marietta's aerospace earnings "continued a strong upward trend" becaus e of government defense and space program contracts.

Martin Marietta aluminum was the largest single profit center, with earnings "slightly ahead" of the first half of 1979 based on an 8 percent gain in sales. Chemical business "virtually equaled" last year's record first-half earnings, but profits from cement and rock products were off because of the showdown in construction, said Rauth.

Blaming high interest rates for a 28 percent plunge in its profits, Union Trust Bancorp of Baltimore reported its second-quarter earnings fell to $1.64 million (67 cents a share) from $2.28 million (93 cents) in the same period a year ago.

It was the second quarter in a row of lowered earnings for the big Maryland bank. For the first half of 1980, Union Trust's net fell to $3.43 million ($1.40) from $4.36 million ($1.78) last year.

Union Trust Chairman J. Stevenson Peck said he expects the bank's earnings to improve in the third and fourth quarters because of the drop in the interest rate the bank must pay for deposits during the second quarter.

LongEtronics of Springfield reported second-quarter net income of $345,000 (32 cents a share), compared with $324,000 (31 cents) a year ago.

First-half net income increased to $643,000 from $630,000, but earnings per share remained unchanged at 60 cents.

Revenues of the Virginia electronics firm were off by $3,000 for the quarter -- to 7.625 milllion -- but for the first half of the year increased to $15.2 million from $13.7 million.

Federal Realty Investment Trust turned in a 26 percent gain in net income for the second quarter and a 32 percent improvement in profits for the first half.

The Chevy Chase REIT posted a profit of $322,000 (21 cents a share) for the qurter, up from last year's $256,000 (17 cents), and earned $803,000 (53 cents) for the first half, up from $606,000 (40 cents).

Revenues climbed from $2.13 million to $2.49 million for the quarter and from $4.36 million to $4.97 million for the first half.

The trust acquired two shopping centers in April, which helped boost its earnings, and rentals from shopping centers were up 35 percent for the first half, said President Steven J. Guttman.

The slump in the housing industry hurt earnings of Ryland Group Inc., a Columbia builder. Ryland reported its second-quarter profits fell to $1.53 million (49 cents a share) from $1.64 million (51 cents) despite an increase in sales to $56.8 million from $55.2 million.

For the first half, Ryland's sales were up by $10 million -- to $109 million from $99 million -- but earnings increased only $5,000 -- to $2.8 million from $2.795 million. Because of a decrease in the number of shares of common stock outstanding, earnings per share increased to 90 cents from 87 cents.

In other reports, Atlantic Research Corp., the Alexandria technology firm, has reported a 29 percent rise in second-quarter profits to $504,000 (31 cents a share) from $391,000 (33 cents) for the 1979 second quarter. Sales rose from $12.5 million to $16.8 million.

For the first half of the year, the company reported profits of $811,000 (52 cents), up from $755,000 (64 cents) last year when fewer shares were outstanding. Sales increased to $30.6 million from $24.8 million.

Ethyl Corp. of Richmond reported a 34 percent drop in profits for the second quarter to $17.3 million (84 cents a share) from $26.33 million ($1.29) for the second quarter of 1979 as sales rose to $440 million from $413 million.

First-half profits dropped 3 percent to $45.84 million ($2.24) from $47.84 ($2.32) in 1979. Sales of $879 million topped last year's $783 million.

The company's chairman, F.D. Gottwald, said the company "was quite satisfied" with the first-half earnings in light of the effects of the recession on the chemical industry.

Chesapeake Corp. of Virginia, a West Point lumber and paper products firm, with second-quarter profits of $6.1 million ($1.00 a share) vs. $4.9 million (81 cents) as sales rose to $60.1 million from $57 million. Chesapeake said demand remained strong in the quarter but that because of recession second-half earnings are expected to decline from 1979 levels.

Adams Express Co., a Baltimore-based investment company, listed net asset value per share of $15.99 on June 30, compared with $14.83 a year earlier, as assets rose to $260 millin from $232 million. Duriing the second quarter, Adams added four new securities to its portfolio, including 100,000 shares of Geico Corp. and 100,000 shares of Mercantile Bankshares.

Noxell Corp., a Maryland cosmetics manufacturer, posted second-quarter profits of $4 million (82 cents a share) vs. $3.5 million (69 cents) as sales rose to $50.6 million from $46.1 million.